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Resistance to Direct Antiviral Agents in Patients With Hepatitis C Virus Infection -
Gastroenterology Feb 2010
from Jules: drug resistance as it relates to the new oral HCV drugs, and 20-30 are listed in the table below, is crucial to understand. We do not yet know if resistance will persist after it develops, and it does develop, and lead to cross-resistance to other drugs in the class or prevent response to other drugs in the same class later on, but at this time it is important to consider that it might persist and if it does this needs to be considered in treatment decision making. I one poster at AASLD 2 years ago resistance to telaprevir persisted in several individual patients after up to 3 years, and this may occur with other protease inhibitors or other oral HCV drugs, but an important question is if resistance persists will it prevent response to treatment again with the same drug or class of drug. This has not yet been tested.
Christoph Sarrazin, Stefan Zeuzem
J. W. Goethe-University Hospital, Medizinische Klinik 1, Frankfurt am Main, Germany
Received 12 October 2009; accepted 12 November 2009. published online 14 December 2009.
"It is important to increase our understanding of mechanisms of resistance mutations, viral breakthrough, and relapse after therapy with DAA agents. Improving our knowledge of these processes will require more precise and earlier characterization of resistance profiles of patients given monotherapy, long-term follow-up data, and studies with combination therapies. Studies also are underway to test the effects of combinations of DAA agents without interferon alfa or ribavirin—these trials will provide valuable information about the ability of DAA agents to suppress HCV replication without development of resistance or even to eradicate the virus."
"It is not known whether resistant variants can persist in the long term as major or minor quasispecies in nonresponsive patients or those with viral breakthrough or relapse after DAA therapy. Thus, genotypic sequence analysis should be performed in the first days during therapy, directly after viral breakthrough, at the end of treatment, and during short-term and long-term follow-up evaluation. Initial characterization of the HCV resistance profile to DAA agents, using the highly sensitive clonal sequencing method, is mandatory. However, other methods for sequence analysis are available (ie, direct sequencing, TaqMAMA, hybridization assays, restriction enzyme assays, deep sequencing methods). It remains to be established which approach will be most useful to identify DAA agent resistance mutations in clinical practice.65......After termination of treatment with telaprevir the number of wild-type isolates rapidly increased within the first 7–10 days of follow-up evaluation. After 3–7 months no high-level resistance was observed anymore and the majority of resistant variants were replaced by wild-type virus.23 However, in single patients V36 and R155 variants still were detectable at low levels and in a recent report on long-term follow-up evaluation even after up to 3 years in single patients low- to medium-levels of V36 and R155 variants were observed.77......differences between linear tetrapeptide and macrocyclic inhibitors binding to the active site of the NS3 protease have been revealed (Figure 3). However, R155 is the main overlapping position for resistance, and different mutations at this amino acid site within the NS3 protease confer resistance to all protease inhibitors that are currently in advanced clinical development......Several nucleoside inhibitors targeting the active site of the HCV-RNA–dependent RNA-polymerase as well as a number of nonnucleoside inhibitors binding to different allosteric sites of the NS5B polymerase are currently in clinical development......R7128, another nucleoside polymerase inhibitor with antiviral activity in genotype 1–infected patients in phase 1 monotherapy studies,91 currently is being investigated in phase 2 clinical trials in genotype 1–, 2–, and 3–infected patients in combination with pegylated interferon and ribavirin as well as in combination with the protease inhibitor R7227/ITMN191. Also from these studies no viral breakthrough with selection of resistant variants was reported. In vitro, different resistant variants for R7128/NM283 (S282T) and R1626 (S96T) have been selected and cross-resistance was excluded......At least 4 different allosteric binding sites have been identified for inhibition of the NS5B polymerase by nonnucleoside inhibitors (Table 1). A number of mutations conferring resistance to the different chemical classes of nonnucleoside inhibitors have been observed mainly in in vitro studies (Figure 4)......VCH-759, VCH-916, and VCH-222 are 3 other NNI-site 2 inhibitors with antiviral activities in monotherapy studies (Figure 1C).16, 100, 101 For VCH-759 as well as VCH-916 viral breakthroughs with selection of resistant variants conferring high (M423T/V/I) and medium (L419V/M, I482L/V/T, V494A/I) levels of resistance were observed (Figure 4).16, 102 In the majority of patients who experienced a viral breakthrough resistance mutations were found to remain present up to 13 days despite a high HCV replication rate and a reduced replication fitness of the variants in vitro.16.....ABT-333, another palm site inhibitor, showed antiviral activity in patients with genotype 1 infection (Figure 1C) and from in vitro replicon studies C316Y and Y448C were observed as main resistance mutations.106, 107 In addition, S556G was reported to be associated with viral breakthrough in a clinical study (Figure 4).106.....In a single ascending dose study it was shown that inhibition of the NS5A protein with BMS-790052 leads to a sharp initial decline of HCV-RNA concentrations (Figure 1D).108 BMS-790052 is the first NS5A inhibitor binding to domain I of the NS5A protein, which was shown to be important for regulation of HCV replication.109 No clinical data on resistance to this class of drugs have been presented yet and results of multiple dose studies have to be awaited."
Chronic hepatitis C virus (HCV) infection is one of the major causes of cirrhosis, hepatocellular carcinoma, and liver failure that leads to transplantation. The current standard treatment, a combination of pegylated interferon alfa and ribavirin, eradicates the virus in only about 50% of patients. Directly acting antiviral (DAA) agents, which inhibit HCV replication, are in phase 1, 2, and 3 trials; these include reagents that target the nonstructural (NS)3 protease, the NS5A protein, the RNA-dependent RNA-polymerase NS5B, as well as compounds that directly inhibit HCV replication through interaction with host cell proteins. Because of the high genetic heterogeneity of HCV and its rapid replication, monotherapy with DAA agents poses a high risk for selection of resistant variants. We review the parameters that determine resistance, genotypic and phenotypic resistance profiles of DAA agents, and strategies to avoid the selection of resistant variants.
Drug resistance results from variations in drug targets (bacteria, fungi, viruses, tumor cells, and so forth) that affect signal transduction pathways, receptors, drug binding sites, or even host proteins to make the therapeutic agent ineffective. Chronic hepatitis C virus (HCV) infection, which affects more than 180 million patients worldwide and is one of the leading causes of cirrhosis and liver failure, is treated with a combination of pegylated interferon alfa and ribavirin. HCV strains with specific mutations that confer resistance to these drugs have not yet been identified in patients, yet only 50%–60% of patients treated with pegylated interferon alfa and ribavirin achieve a sustained virologic response.1 This low rate of response can be accounted for by several viral and host-related factors.2, 3, 4, 5 Furthermore, because of significant side effects associated with the administration of interferon alfa and ribavirin, combination drug doses and treatment duration are restricted. More effective and better-tolerated treatment options for HCV infection are needed. Directly acting antiviral (DAA) agents that are also named specific, targeted antiviral therapies (STAT-C) for HCV infection are in phase 1–3 trials. We review resistance to DAA agents, focusing on compounds in development such as reagents that target the HCV nonstructural (NS)3 protease, the NS5A protein, and the RNA-dependent RNA polymerase NS5B. We also discuss indirect inhibitors or compounds that inhibit HCV replication by not yet completely resolved mechanisms, such as cyclophilin inhibitors, nitazoxanide, and silibinin (Table 1, Figure 1).
Table 1. Direct Antiviral Drugs in Development for HCV Infection
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Figure 1. Antiviral activities (mean or median maximum decrease in HCV RNA log10 IU/mL) of DAA agents, as determined from phase 1 monotherapy studies (3–14 days) in patients infected with HCV genotype 1. Different reagents or durations of treatment were not compared directly in these studies. In patients who received the DAA for 7–14 days, the decrease in viral load might not reflect only the activity of the DAA agent but also the emergence of resistant variants. *Clinical development stopped. (A) NS3 protease inhibitors. (B) Nucleoside inhibitors of NS5B. (C) Nonnucleoside inhibitors of NS5B. (D) NS5A inhibitor, indirect inhibitors and agents with unknown mechanism of action. QD, every day, BID, twice a day, TID, three times a day, BW, body weight, #, 900 mg BID stopped from further development due to increase of liver enzymes in single cases.
Parameters That Affect Resistance
Heterogeneity of HCV
HCV has a high rate of turnover; its half-life was estimated to be only 2–5 hours, with the production and clearance of 1010 to 1012 virions per day in an infected patient.6, 7 The HCV-RNA–dependent RNA-polymerase NS5B has poor fidelity and lacks proof-reading activity. Because of this feature and the high replication activity of HCV, a large number of viral variants are produced continuously during infection (error rate, approximately 10-3 to 10-5 mutations per nucleotide per genomic replication).8 The majority of variants produced result in loss of viral replication via loss of function of encoded proteins or lack of tolerance by the host's immune system.9, 10 However, a large number of variants survive; the sum of these different isolates in an infected patient is called viral quasispecies. Typically a dominant strain (wild-type) is detectable within the viral quasispecies along with strains that are present at lower frequencies. The frequencies of HCV isolates depend on their replication efficacies and other known and unknown viral and host factors. During the phylogenetic evolution of HCV, at least 6 different genotypes and more than 100 subtypes have developed that are characterized by large differences in nucleotide sequence (31%–33% and 20%–25%, respectively).11 Thus, the development of HCV therapies is challenged by the different genotypes and subtypes of virus in different patients and also the variation in viral isolates in each patient. Given the heterogeneities in viral sequence, not all drugs will be equally effective for all HCV genotypes, subtypes, and isolates. However, variations are not distributed equally throughout the HCV genome; compounds that target more conserved regions (ie, the active site of the RNA-dependent RNA polymerase) have a better chance of efficacy in patients infected with different genotypes and subtypes.
HCV genotypes and resistance
Many DAA compounds that are being tested in clinical studies are designed to inhibit HCV genotype 1 isolates and the majority of studies have been performed in patients infected with HCV genotype 1. However, telaprevir, an inhibitor of the HCV NS3 protease that targets the active site of the enzyme, has been given subsequently also to patients infected with genotypes 2, 3, and 4. In these patients, viral load decreased by 3.9, 0.5, and 0.9 log10 IU/mL, respectively, after 2 weeks of monotherapy, compared with 4.4 log10 IU/mL in genotype 1–infected patients.12, 13, 14 Also, boceprevir has been reported to have weaker antiviral activity in patients infected with genotypes 2 or 3 and similar results are to be expected for other HCV protease inhibitors. Different levels of activity against different HCV genotypes also are expected from nonnucleoside NS5B inhibitors based on results from in vitro studies; little clinical data are available.15 Administration of VCH-759, for example, which binds the thumb 2 site to inhibit the polymerase NS5B, for 10 days led to a mean maximal decrease in HCV RNA log10 IU/mL of 2.5 in genotype 1–infected patients, whereas no viral decline was observed in a genotype 6–infected patient.16
The active site of NS5B is highly conserved between different genotypes, so nucleoside inhibitors could have similar levels of activity in patients infected with different genotypes. However, there are no data on the efficacy of monotherapy with nucleoside analogs against different genotypes. An interim analysis of data from a placebo-controlled trial of patients infected with HCV genotypes 2 or 3 who did not respond to interferon therapy reported increased rapid virologic response rates after 4 weeks of triple therapy with pegylated interferon alfa, ribavirin, and the nucleoside analogue R7128, compared with standard combination therapy (without the NS5B inhibitor). So, it appears that NS5B inhibitors have antiviral activity in patients with HCV genotypes 2 or 3.17
No clinical data are available on the efficacy of NS5A inhibitors in patients with HCV non–genotype 1, but given the relatively high level of heterogeneity in the NS5A protein, differences in antiviral activities against different genotypes are expected.
Agents that act on host proteins, such as cyclophilin inhibitors, would be predicted to have similar levels of antiviral activity against all HCV genotypes. However, monotherapy with the cyclophilin inhibitor Debio-025 was significantly less effective in patients infected with genotypes 1 or 4 compared with genotypes 2 or 3; viral loads decreased by 2.5 and 4.4 log10 IU/mL, respectively, after 4 weeks monotherapy with 1000 mg Debio-025.18 For monotherapy with nitazoxanide, another indirect inhibitor of HCV replication, data on viral load reduction are available only in patients infected with HCV genotype 4.19 However, indirect evidence for differences between HCV genotypes is available from combination therapies. Triple therapy with nitazoxanide, pegylated interferon, and ribavirin, after a lead-in phase with only nitazoxanide, resulted in different virologic response rates in patients infected with HCV genotype 1 compared with genotype 4 (5%–12% vs 64%, respectively).20, 21 Finally, silibinin, for which the mechanism of action is not yet entirely resolved, administered intravenously (20 mg/kg/day) for 7 days, led to a mean decline of the HCV-RNA concentration by 3 log10 IU/mL. So far, mainly genotype 1 and single patients with genotype 2, 3, and 4 infections have been investigated and no data on differences of antiviral activities for the different HCV genotypes are available.22
HCV subtypes and resistance
Differences in the HCV genome sequence are smaller between subtypes than between genotypes, resulting in smaller variations in antiviral activity of DAA agents between subtypes than genotypes.
However, differences between subtypes have been described in the activities of the linear protease inhibitors telaprevir and boceprevir. In clinical studies of telaprevir alone or in combination with pegylated interferon (with or without ribavirin), selection of resistant variants and viral breakthrough have been observed consistently more frequently in patients infected with HCV subtype 1a than subtype 1b.23, 24, 25 In the protease inhibition for viral evaluation (PROVE) 1 study (triple therapy: telaprevir, pegylated interferon alfa 2a, and ribavirin), 11 of the 12 patients who experienced a viral breakthrough were infected with HCV subtype 1a; only 1 of the 12 was infected with subtype 1b.25 This difference was shown to result from nucleotide differences at position 155 in HCV subtype 1a (aga, encodes R) vs 1b (cga, also encodes R). The mutation most frequently associated with resistance to telaprevir is R155K; changing R to K at position 155 requires 1 nucleotide change in HCV subtype 1a and 2 nucleotide changes in subtype 1b isolates (Figure 2). Selection of the resistant variant R155K to monotherapy with the NS3 inhibitor boceprevir also differed between patients infected with HCV subtypes 1a and 1b.26 Taken together, based on differences in codon usage for telaprevir and boceprevir several resistant variants were selected typically in subtype 1a– (V36M, R155K/T) or 1b– (R155Q, V170A) infected patients.23, 26 Differences between subtype 1a– and 1b–infected patients also were observed for macrocyclic NS3 protease inhibitors (ITMN191/R7227, BI201335).27, 28
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Figure 2. Molecular basis for different probabilities for selection of R155K/T/Q mutations in subtype 1a– vs subtype 1b–infected patients treated with a NS3 protease inhibitor. Selection of R155K/T requires 1 nucleotide exchange in subtype 1a but 2 nucleotide exchanges in subtype 1b patients. Selection of R155Q requires 1 nucleotide exchange in subtype 1b but 2 nucleotide exchanges in subtype 1a patients.
Nucleoside analogs that bind to the highly conserved, active site of NS5B seem to have an equal antiviral activity against different HCV subtypes; no differences have been reported for NM283, R1626, and R7128 in patients infected with HCV subtypes 1a or 1b.29, 30, 31
Polymerase inhibitors binding to less-conserved allosteric sites of NS5B have a greater risk of different antiviral activities and different resistance profiles in patients infected with different subtypes. Administration of BI207127, a nonnucleoside inhibitor of NS5B that binds to the thumb 1 site (NNI site 1), led to a viral decline in all patients infected with HCV genotype 1, without viral breakthrough during treatment for 5 days. However, BI207127 was reported to be less active against HCV subtype 1a than 1b.32 BILB1941, another thumb 1 site inhibitor, also had greater antiviral activity in patients infected with subtype 1b in comparison with subtype 1a.33
Filibuvir (PF-00868554) is a thumb 2 site (NNI site 2) inhibitor of NS5B. Differences in resistance to this drug were observed between patients infected with HCV subtypes 1a and 1b after 8 days of monotherapy.34 Also, triple therapy with filibuvir, pegylated interferon alfa 2a, and ribavirin resulted in a rapid virologic response more frequently in patients infected with subtype 1a (14 of 19) vs 1b (3 of 7) virus.35
Furthermore, differences in the reduction in median HCV-RNA levels have been reported between patients with HCV subtypes 1a (1.4–2.5 log10 IU) and 1b (2.6–3.2 log10 IU) who were treated for 3 days with the nonnucleoside inhibitor ANA598, which binds to the palm 1 site (NNI site 3).36 No viral breakthrough was detected during this short-term treatment but the observed differences of the antiviral activity could result from sequence differences between subtypes 1a and 1b in the ANA598 binding site. No host or HCV subtype-specific differences have been reported to affect the antiviral activity of HCV796, a palm 2 site inhibitor (NNI site 4) of NS5B. However, resistance data have been presented only from patients infected with HCV subtype 1a.37, 38 In vitro different resistant variants in subtype 1a and 1b isolates were selected during incubation with HCV-796.39
HCV isolates and resistance
Even within a given HCV subtype, variations in amino acid sequences are common and can affect the antiviral activity of an antiviral agent and the barrier of resistance.
For example, the pre-existing dominant strain in a patient's quasispecies can sometimes be an HCV variant with reduced sensitivity to NS3 inhibitors that bind to the active site of the protease. In different studies direct sequencing revealed resistant variants at positions V36, T54, R155, D168, and V170 of the NS3 protease in 0.2%–2.2% of patients as the pre-existing dominant strain.10, 40, 41, 42, 43 Patients with the R155K variant had a reduced response to telaprevir compared with patients without this variant and none of the 4 of 570 patients with this variant already present at baseline as the dominant strain achieved a sustained virologic response during treatment in the PROVE 1/2 studies.40 Studies using ultra-deep sequencing methods revealed that most amino acid variants that confer resistance to protease inhibitors are detectable within the HCV quasispecies already before treatment, but at low frequencies. Currently, it is unknown which frequency of a specific resistant variant influences effectiveness of treatment with an NS3 protease inhibitor.44
Mutations that confer in vitro resistance to nucleoside analogs that inhibit NS5B (S96T, S282T, N142T) were not detected in patients with HCV genotype 1 infections.10, 41, 45
Variants conferring resistance to nonnucleoside inhibitors that bind to different allosteric sites of the NS5B polymerase were detected in 0.6%–2.8% of patients by direct sequencing as pre-existing major variants.10, 34, 41, 45, 46 However, for nonnucleoside inhibitors resistance mutations also may occur as natural variants more frequently in patients infected with a specific subtype. For example, the C316Y mutation in NS5B is associated most frequently with resistance to HCV-796,37 although C316N also reduces sensitivity to HCV796 in vitro and this variant frequently is observed in many patients infected with HCV subtype 1b.45
Resistance mutations selected during treatment with DAA typically are associated with reduced replicative fitness. Interestingly, patients who have not yet received antiviral therapy but are infected with DAA-resistant variants as the pre-existing dominant strain have been reported to have high baseline concentrations of HCV RNA. Thus, it would be interesting to learn how the naturally occurring resistant variants achieved their high replicative capacities in the absence of drug selection.
Barrier to Resistance
The barrier to resistance to a direct antiviral agent is influenced by several parameters such as the HCV genotype and subtype, the activity and pharmacokinetics of the antiviral agent, patient compliance, and the binding affinity of the antiviral compound for its site. We have learned from studies of human immunodeficiency virus and hepatitis B virus (HBV) infection that several recently developed antiviral drugs have a high genetic barrier to resistance because of a flexible binding pattern that allows proper binding even in the presence of resistance mutations47 or the requirement of more than 1 amino acid exchange for resistance to occur.48 Development of DAA agents for HCV infection still is in its early days with no compounds approved yet and limited studies available on comparative resistance analysis. However, for the agents currently in development, it seems that the genetic barrier of nonnucleoside analogs is lowest, followed by those of NS3 inhibitors, and then nucleoside analogs. For nonnucleoside analogs low to medium antiviral activities (0.6–3.7 log10 HCV RNA IU/mL decline) were observed in clinical studies (Figure 1C). Nucleoside analogs also had relatively low antiviral activities in clinical studies (0.7–1.2 log10 HCV RNA IU/mL decline), which were enhanced up to 3.7 log10 only with very high doses (Figure 1B). NS3 protease inhibitors showed high antiviral activities (up to 4.6 log10 IU/mL HCV RNA decline) and for the first NS5A inhibitor at low doses a high antiviral activity also was observed (Figure 1D).
Nonnucleoside inhibitors bind to allosteric sites on the surface of NS5B. Here, a high number of variants with multiple amino acid exchanges can occur without functionally altering the NS5B polymerase activity; it is therefore challenging to design an NS5B inhibitor with a high genetic barrier to resistance. Variants that are resistant to most nonnucleoside inhibitors are selected for within a few days of treatment. Moreover, variants with reduced sensitivity to nonnucleoside NS5B inhibitors may be present at high frequencies already before initiation of direct antiviral therapy.
NS3 inhibitors that bind to the active site of the protease are considered to have an intermediate barrier to resistance. Here, variants conferring resistance rarely are observed as naturally occurring variants. However, selection of resistant variants during treatment with an NS3 protease inhibitor followed by a viral breakthrough was observed within 3–4 days of monotherapy.
Nucleoside analogs seem to have the highest genetic barrier to resistance. Mutations at the active site of NS5B most likely cause loss of polymerase function; no resistant variants have been reported to emerge in monotherapy studies (up to 2 weeks) with the nucleoside analogs R1626 or R7128.30, 31
In many patients—especially among suboptimal dosing cohorts in phase 1 studies—viral breakthrough occurs, with rapid selection of resistant variants. However, some patients have a continuous decrease in viral load throughout the entire dosing period (2 weeks). Nevertheless, the possibility of long-term suppression of viral replication in patients given monotherapy with a NS3 inhibitor seems unlikely. In one long-term study, telaprevir monotherapy was given to 5 patients for up to 24 weeks. Three patients experienced viral breakthrough with selection of resistant variants, 1 patient discontinued therapy because of side effects, and 1 patient had low levels of HCV RNA in serum at the end of the 24-week treatment period.49 No long-term monotherapy studies with NS5B inhibitors have been performed to date and results from additional monotherapy studies with telaprevir from Japan have to be awaited to determine the potential of viral eradication with a single DAA treatment approach.
No clinical data are available on the barrier to resistance for nitazoxanide or silibinin. Interestingly, HCV variants that are resistant to cyclophilin inhibitors have been reported in in vitro studies.50, 51
Pharmacokinetics and Compliance
With the exception of silibinin all DAA agents are being developed for oral administration. Both the NS3 inhibitors that are in phase 3 studies, boceprevir and telaprevir, have a relatively short half-life, requiring a 3-times-per-day dosing interval.12, 52 Trough plasma levels were correlated with antiviral responses in phase 1 studies of these agents. Moreover, 6 of 10 patients who received 2 daily doses of 1250 mg telaprevir had viral breakthrough and resistance, compared with 1 of 8 patients who received 3 daily doses of 750 mg telaprevir (the subsequent standard therapy) in a phase 1 monotherapy study.23 Interim analysis after 12 weeks of triple therapy with telaprevir, pegylated interferon, and ribavirin showed no differences in the decrease of antiviral activity or viral breakthrough in patients treated 2 times daily with 1125 mg, compared with 3 times daily with 750 mg telaprevir. However, small numbers (39–42 patients) were enrolled in each cohort and differences might become visible only in larger studies, especially in nonresponders to previous pegylated interferon/ribavirin combination therapy.53
For patients with human immunodeficiency virus infection, compliance is one of the major factors that affect the development of resistance.54 Treatment failure from drug resistance has been decreased by reducing the administration of antiretroviral therapy from 3-times-daily to once-daily highly active antiretroviral therapy. Many DAA agents currently in phases 1 and 2 trials have a half-life that allows for once- or twice-daily dosing. Similar to human immunodeficiency virus treatment, ritonavir also is given to HCV patients along with several HCV NS3 inhibitors (ITMN191/R7227, SCH900518) to improve pharmacokinetic properties and prolong dosing intervals. However, about 10% of patients are intolerant to ritonavir because of its side effects. Thus, the addition of ritonavir to triple therapies of DAA, pegylated interferon, and ribavirin may enhance early discontinuation rates and thereby may reduce a patient's potential to achieve a sustained virologic response.
Combination Therapies
In human immunodeficiency virus and HBV infection combination therapies are used to overcome rapid selection of variants that are resistant to single agents and increase the odds of long-term suppression of viral replication. HCV variants with amino acid changes that confer resistance to DAA compounds retain their sensitivity to interferon alfa and non–cross-resistant drug classes in vitro.55, 56, 57
DAA plus pegylated interferon
Combination therapies of protease inhibitors with pegylated interferon alfa have been tested for their abilities to overcome resistance to single agents and for their additive or even synergistic antiviral activities. In a phase 1 study of 14 days of combination therapy with telaprevir and pegylated interferon alfa 2a, a continuous decline in HCV-RNA concentrations, without viral breakthrough, was observed. Furthermore, antiviral efficacy was at least additive, with a maximum decline of 5.5 log10 for the combination therapy, compared with 4.4 log10 for telaprevir monotherapy.58 Another study showed that combination therapy with boceprevir with pegylated interferon alfa 2b principally may be effective in patients who did not respond to previous interferon alfa–based treatment regimens.52 Combination therapies with pegylated interferon and other protease or polymerase inhibitors had similar effects. However, in the first phase 2 trial, which included a longer duration of therapy, up to 24% of patients who received combination therapy with telaprevir and pegylated interferon alfa 2a experienced a viral breakthrough with emergence of resistant HCV variants. In addition, a high relapse rate (48%) was observed.25, 59
Triple therapy DAA plus pegylated IFN plus ribavirin
The addition of ribavirin to combination therapy with a protease inhibitor and pegylated interferon alfa significantly increased antiviral activity, lowered relapse rates, and reduced viral breakthrough and selection for resistant variants. In a study that compared combination therapy with telaprevir and pegylated interferon alfa to triple therapy that included ribavirin, HCV-RNA levels were undetectable after 12 weeks in 62% and 80% of patients, respectively. Furthermore, viral breakthrough occurred during treatment in 24% of patients on double therapy and 1% on the triple therapy; virologic relapse occurred in 42% and 25% of the patients, respectively.59 Similar results were observed in other studies comparing dual vs triple therapies with the NS3 protease inhibitor boceprevir or the polymerase inhibitor R1626.30, 60, 61, 62 However, no studies have been conducted to test combination therapies with DAA and ribavirin but without interferon alfa. Future studies are needed to determine whether ribavirin exerts its antiviral activity only in the presence of interferon alfa or also if it can decrease viral load and prevent selection of resistant variants in combination with a DAA agent.
DAA combination therapies
Another possibility to suppress viral replication, avoid the selection of resistant variants and viral breakthrough, as well as potentially eradicate the virus are DAA combination regimens. Studies in the in vitro HCV replicon model and in chimpanzees have indicated the potential of combination therapies with protease and polymerase inhibitors. Indeed, using this approach, HCV was eradicated in a chimpanzee.57, 63 Results of the first clinical study of the combination of a polymerase inhibitor (R7128) and an NS3 inhibitor (R7227/ITMN191) were presented recently (INFORM-1 study). In this proof-of-principle study, patients were given both DAA agents for up to 2 weeks. HCV-RNA concentrations decreased by as much as 5.2 log10 IU/mL, no viral breakthrough was observed, and HCV RNA was undetectable by the end of the study in up to 63% of patients, measured using a highly sensitive assay.64 The potential of this combination therapy to suppress replication for longer durations, without viral breakthrough or selection of resistant variants, and to ultimately achieve a sustained virologic response, has to be shown in future studies.
Characterization of Resistant Variants Selected During Treatment With DAA
The resistance profile of an HCV quasispecies is best determined by analysis of the genome sequence that is targeted by the DAA agent using a highly sensitive clonal sequencing approach. By direct sequencing, only amino acid variations that occur in the HCV quasispecies at a frequency of approximately 25% can be detected, whereas cloning and sequencing of, for example, 80 isolates, viral variants present at approximately 5% of the population will be detected. In addition, the clonal approach also allows analysis of mutations linked on a given isolate. Moreover, because of the rapid viral turnover during HCV infection and because highly resistant variants typically are associated with a significantly impaired replicative fitness these variants will be overgrown by wild-type virus shortly after termination of antiviral therapy and/or compensated by additional mutations that enhance the replication efficiency. The likeliness of selection of isolates with compensated replicative fitness increases with the duration of DAA therapy without complete suppression of viral replication. Furthermore, for combination therapies resistant viral variants may be selected in the first days during treatment followed by a continuous viral decline because of a lack of cross-resistance between the different antiviral drugs.
It is not known whether resistant variants can persist in the long term as major or minor quasispecies in nonresponsive patients or those with viral breakthrough or relapse after DAA therapy. Thus, genotypic sequence analysis should be performed in the first days during therapy, directly after viral breakthrough, at the end of treatment, and during short-term and long-term follow-up evaluation. Initial characterization of the HCV resistance profile to DAA agents, using the highly sensitive clonal sequencing method, is mandatory. However, other methods for sequence analysis are available (ie, direct sequencing, TaqMAMA, hybridization assays, restriction enzyme assays, deep sequencing methods). It remains to be established which approach will be most useful to identify DAA agent resistance mutations in clinical practice.65
The first characterization of HCV resistance variants selected during monotherapy with telaprevir and identified by the clonal method identified mutations that were not predicted with the HCV replicon assays.23, 66 Previous in vitro replicon studies identified the A156S/V/T mutation in NS3, but not mutations at V36, T54, or R155, which were selected in patients treated with telaprevir. High doses of telaprevir were used in the in vitro replicon studies, whereas lower concentrations of boceprevir selected for the T54A and V170A mutations in NS3 in the HCV replicon system. Mutations at position Q41 and F43 of NS3 were identified in the replicon assay, but these variants were not selected in patients treated with telaprevir or boceprevir so far.67 Mutations in NS3 that conferred resistance to boceprevir, such as V55A, also were not predicted from in vitro studies but were detected using highly sensitive genotypic analysis of the HCV quasispecies in patients from the phase 1 monotherapy study.26
Interestingly, for both telaprevir and boceprevir during monotherapy a large number of mutational variants were selected (n = 25–31) and restrictions (increase of more than 5% frequency from baseline, detection in more than 1 patient, decline after the end of treatment) were made for further analysis.23, 26, 68 Finally, mutations at 6 amino acid positions (V36, T54, V55, R155, A156, and V170) were associated clearly with resistance to these protease inhibitors. A potential importance of the multiple additional low-frequency variants at other positions has to be investigated in future studies.
After genotypic characterization, levels of resistance to the antiviral agent used in the clinical study, and potential cross-resistance to other direct antivirals must be determined by phenotypic assays. Different replicon- and enzyme-based phenotypic assays have been used to determine the IC50/EC50 values of DAA agents for HCV replication or enzymatic functions of wild-type and mutant HCV proteins.23, 26, 27, 69, 70 The majority of replicon assays is based on the HCV con1b isolate with restrictions for variants detected in subtype 1a isolates and other genotypes.39 Furthermore, typically only the detected variant, alone or in combination with another resistant variant, rather than the entire NS3 protease gene from a given patient, is introduced into NS3 for analysis in a phenotypic assay.
The data from clonal genotypic and phenotypic resistance analyses of telaprevir and boceprevir from phase 3 trials have been published.23, 24, 26 However, the resistance profiles of the majority of DAA agents have not been characterized fully. We summarize the available resistance genotypic and phenotypic resistance profile of DAA agents that are in phase 1, 2, or 3 trials.
NS3 Protease Inhibitors
BILN2061 (Ciluprevir) was the first NS3 protease inhibitor investigated in clinical studies. BILN2061 showed a high antiviral activity in genotype 1 and a variable antiviral activity in genotype 2/3–infected patients after dosing for 2 days. However, further development of BILN2061 was stopped and no clinical resistance data are available.71, 72, 73
Telaprevir
Telaprevir has a high antiviral activity (Figure 1A) but a medium genetic barrier to resistance.12 During monotherapy of genotype-1–infected patients with different doses of telaprevir for 14 days mainly viral variants at 6 positions within the NS3 protease were selected rapidly (Figure 3).23 These variants were detected either alone or in combination on the same isolate (mainly positions 36+155 or 36+156). Phenotypic analysis showed low- to medium-level (V36, T54, R155, A156S) and high-level (A156V/T) resistant variants. Molecular-based mechanisms of resistance have been proposed.66, 74, 75, 76 In more than 80% of the isolates of the HCV quasispecies at the end of treatment resistance mutations were detected. High-level resistant variants typically were observed in patients with higher telaprevir exposure and more pronounced viral decline. Generally, an inverse correlation between the level of telaprevir resistance conferred by a single mutation and replicative viral fitness was observed. Double mutants (V36A/M + R155K/T) seem to have a compensatory effect with an increase of replicative fitness together with a relatively high level of resistance.23, 24 After termination of treatment with telaprevir the number of wild-type isolates rapidly increased within the first 7–10 days of follow-up evaluation. After 3–7 months no high-level resistance was observed anymore and the majority of resistant variants were replaced by wild-type virus.23 However, in single patients V36 and R155 variants still were detectable at low levels and in a recent report on long-term follow-up evaluation even after up to 3 years in single patients low- to medium-levels of V36 and R155 variants were observed.77
Picture 7.png
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Figure 3. Amino acid positions within the NS3/4A protease associated with (A) resistance mutations to different NS3 protease inhibitors and a (B) cross-resistance table of different NS3 protease inhibitors based on mutations selected in patients from clinical studies and/or from in vitro studies. Amino acids forming the catalytic triad (H57, D81, S139) are highlighted. *Mutations associated with resistance in vitro but were not described in patients. **Mutations associated with resistance in vitro. Resistance mutations of linear NS3 protease inhibitors are shown in blue and resistance mutations described for macrocyclic NS3 protease inhibitors are shown in green.
During combination therapy of telaprevir with pegylated interferon alfa A156T/V variants were detectable in the initial viral decline phase but viral levels continued to decline.24 During triple therapy with telaprevir, pegylated interferon alfa 2a, and ribavirin in 3% of the patients (5 of 163) a viral breakthrough with wild-type virus in 1 patient but high-level resistant variants in 4 patients (V36M+R155K, A156T) was observed. Furthermore, in patients with relapse after the end of treatment also low- and high-level resistant variants with R155K as the main resistance mutation were detected.59
Generally, the likeliness of a viral breakthrough is correlated with the response to pegylated interferon alfa/ribavirin combination therapy. The majority of patients with a virologic null-response (<1 log10 decline at week 4 or <2 log10 decline at week 12) to pegylated interferon alfa/ribavirin combination therapy who were retreated with triple therapy including telaprevir showed a viral breakthrough. In partial nonresponders (>2 log10 decline at week 12 but HCV-RNA positive at week 24) only several viral breakthroughs were observed during triple therapy and in patients with a prior relapse after standard combination therapy no viral breakthrough was observed during re-treatment with triple therapy including telaprevir.78 Thus, for patients with null-response to pegylated interferon alfa/ribavirin, triple therapy is a form of functional monotherapy with the direct antiviral drug and this is associated with a high probability of viral breakthrough. Future studies have to investigate the possibility to select the optimal patients for triple therapy perhaps with a lead-in phase to characterize the responsiveness to pegylated interferon alfa/ribavirin alone or together with other response predictors (baseline viral load, IL28 polymorphism. This would on the one hand enable the possibility to avoid viral breakthrough with selection of resistant variants and perhaps on the other hand for patients with favorable response predictors no need of the addition of a DAA or very short triple therapies.
Telaprevir was investigated also in genotype 2–, 3–, and 4–infected patients with lower (genotype 2) or virtually absent (genotype 3, 4) antiviral activities.13, 14 Data on resistant variants selected in patients infected with genotype 2, 3, and 4 isolates will be presented at an upcoming meeting.
Boceprevir
Boceprevir has a medium antiviral activity (Figure 1A) and a medium genetic barrier to resistance.79 During monotherapy with 400 mg boceprevir 2 or 3 times daily for 14 days, mainly viral variants at 6 positions within the NS3 protease conferring low- to medium-level resistance were observed (Figure 3). As for telaprevir and also for boceprevir an increasing number of selected variants correlated with a higher viral decline. Interestingly, the mean frequency of wild-type variants was still 86% at the end of treatment and the high-level resistant variant A156T was not observed.26 The currently used dose of boceprevir in the phase 3 trials is 800 mg 3 times daily. However, no monotherapy data with this dose are available and it is unknown whether with the higher dose also high-level resistant variants will be selected.
Genotypic analyses show a largely overlapping cross-resistance profile of boceprevir and telaprevir (Figure 3). However, for example, the V170A variant conferred a higher level of resistance to boceprevir in comparison with telaprevir and this variant was not described to be a frequent variant in patients who received telaprevir.23, 24, 26 Shortly after the end of boceprevir treatment the frequency of wild-type variants increased to 96%. However, in a number of patients 1 year after the end of boceprevir dosing and in single patients even 4 years after the end of boceprevir dosing, either alone or in combination with pegylated interferon, resistant variants still were detected in the HCV quasispecies by clonal sequence analysis.80 Boceprevir also was investigated in genotype 2– and 3–infected patients. However, antiviral activity was reduced in these genotypes and no resistance analysis is available from these studies.
Triple therapy with boceprevir, pegylated interferon alfa 2b, and ribavirin in a large phase 2 study in genotype 1 treatment-naive patients for 2848 weeks was associated with viral breakthrough and selection of resistant variants in 7%–12% of the patients.61 Patients who received a lead-in treatment with pegylated interferon and ribavirin alone for 4 weeks before the addition of boceprevir for another 24 or 44 weeks showed lower viral breakthrough rates (4%–5%).61 However, to answer the question whether a lead-in phase with peginterferon and ribavirin alone will generally reduce the probability of a viral breakthrough, analysis of the phase 2 and 3 studies with boceprevir, telaprevir, and other DAA have to be awaited.
Other NS3 protease inhibitors (R7227ITMN191, MK7009, BI201335, TMC435350, SCH900518, BMS-650032, PHX1766)
Several NS3 protease inhibitors currently in phase 1/2 development showed high antiviral activities in monotherapy studies (Figure 1A)81, 82, 83, 84, 85, 86, 87 and initial resistance analyses have been presented at scientific meetings.27, 28, 84, 85, 88, 89 Taken together, differences between linear tetrapeptide and macrocyclic inhibitors binding to the active site of the NS3 protease have been revealed (Figure 3). However, R155 is the main overlapping position for resistance, and different mutations at this amino acid site within the NS3 protease confer resistance to all protease inhibitors that are currently in advanced clinical development (Figure 3).
Polymerase Inhibitors
Several nucleoside inhibitors targeting the active site of the HCV-RNA–dependent RNA-polymerase as well as a number of nonnucleoside inhibitors binding to different allosteric sites of the NS5B polymerase are currently in clinical development (Table 1).
Nucleoside analogs
Valopicitabine (NM283, 2′-C-methylcytidine/NM107), the first nucleoside inhibitor investigated in patients with chronic hepatitis C, showed a low antiviral activity (Figure 1B).29 Because of gastrointestinal side effects the clinical development of NM283 was stopped. Very sparse clinical data on resistance are available but from in vitro assays S282T mutation in the NS5B polymerase is known to confer resistance to NM283 (Figure 4).90
Picture 9.png
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Figure 4. Amino acid positions within the NS5B polymerase associated with (A) resistance mutations to different nucleoside and nonnucleoside inhibitors and a (B) cross-resistance table of different NS5B polymerase inhibitors based on mutations selected in patients or in vitro. Amino acids forming the catalytic triad (D318, D319, D220) are highlighted. *Mutations associated with resistance in patients. **Mutations associated with resistance in vitro. Mutations of 2′-C-methylcitidine and 4′-azidocytidine nucleoside inhibitors are shown in red and pink, respectively. For NNI-site 1, 2, 3, and 4 inhibitors resistance mutations are shown in orange, dark blue, dark green, and yellow, respectively.
The second nucleoside inhibitor to be reported in patients with chronic hepatitis C was R1626 (4′-azidocytidine/PSI-6130). A phase 1 study in genotype 1–infected patients observed a high antiviral activity at high doses of R1626 in genotype 1–infected patients (Figure 1B).30 No viral breakthrough with selection of resistant variants was reported from monotherapy or combination studies with pegylated interferon ± ribavirin.30, 62 In HCV replicon studies S96T mutation within the NS5B polymerase conferred resistance to R1626.90 Because of severe lymphopenia and infectious disease adverse events further development of R1626 was stopped.
R7128, another nucleoside polymerase inhibitor with antiviral activity in genotype 1–infected patients in phase 1 monotherapy studies,91 currently is being investigated in phase 2 clinical trials in genotype 1–, 2–, and 3–infected patients in combination with pegylated interferon and ribavirin as well as in combination with the protease inhibitor R7227/ITMN191. Also from these studies no viral breakthrough with selection of resistant variants was reported. In vitro, different resistant variants for R7128/NM283 (S282T) and R1626 (S96T) have been selected and cross-resistance was excluded (Figure 4).90
Recently, 2 other polymerase inhibitors (PSI-7851 and IDX184) were evaluated in phase 1 clinical trials in patients with chronic hepatitis C (Figure 1B). However, no data on resistance have been presented for these drugs so far.92, 93
Nonnucleoside analogs
At least 4 different allosteric binding sites have been identified for inhibition of the NS5B polymerase by nonnucleoside inhibitors (Table 1). A number of mutations conferring resistance to the different chemical classes of nonnucleoside inhibitors have been observed mainly in in vitro studies (Figure 4).
NNI-site 1 inhibitors (thumb 1/benzimidazole site)
BILB1941, BI207127, and MK-3281 are NNI-site 1 inhibitors that have been investigated in clinical phase 1 trials with low to medium antiviral activities (Figure 1C).32, 33, 94, 95 No viral breakthrough with selection of resistant variants has been reported during 5 days of treatment with BILB1941 or BI207127.32, 46 However, preexisting NS5B substitutions known to reduce sensitivity were identified for BILB1941 (V494I/A, I424V, P496A) and resistance mutations of NNI-site 1 inhibitors were characterized in vitro (Figure 4).96, 97
NNI-site 2 inhibitors (thumb 2/thiophene site)
Filibuvir (PF-00868554) is a NNI-site 2 inhibitor with medium antiviral activity in a phase 1 study (Figure 1C).98 Pre-existing variants conferring reduced sensitivity to filibuvir were observed in single patients (M426A). Several filibuvir resistant variants have been described in HCV replicon studies.99 During treatment a high number of different variants was observed. However, variants at position M423 known to confer resistance to filibuvir from in vitro studies were selected in the majority of patients (Figure 4).34, 99 In a subsequent triple-therapy trial with filibuvir, pegylated interferon alfa 2a, and ribavirin for 4 weeks, a viral breakthrough was observed in 5 of 26 patients.35
VCH-759, VCH-916, and VCH-222 are 3 other NNI-site 2 inhibitors with antiviral activities in monotherapy studies (Figure 1C).16, 100, 101 For VCH-759 as well as VCH-916 viral breakthroughs with selection of resistant variants conferring high (M423T/V/I) and medium (L419V/M, I482L/V/T, V494A/I) levels of resistance were observed (Figure 4).16, 102 In the majority of patients who experienced a viral breakthrough resistance mutations were found to remain present up to 13 days despite a high HCV replication rate and a reduced replication fitness of the variants in vitro.16
NNI-site 3 inhibitors (palm 1/benzothiadiazine site)
ANA598 is a NNI-site 3 inhibitor that displayed antiviral activity during treatment of genotype 1–infected patients (Figure 1C).36 No viral breakthrough was observed during this short-term monotherapy trial. However, several variants were described from in vitro replicon studies to confer resistance to ANA598 (Figure 4).103
NNI-site 4 inhibitors (palm 2/benzofuran site)
Monotherapy with the NNI-site 4 inhibitor HCV-796 showed low antiviral activity in genotype 1–infected patients (Figure 1C).38 Viral breakthrough was associated with selection of resistant variants that conferred medium to high levels of resistance in phenotypic analysis37, 104 (Figure 4). For GS-9190 low antiviral activity was observed in a clinical study and variants conferring resistance were identified in the β-hairpin of the polymerase.94, 105 ABT-333, another palm site inhibitor, showed antiviral activity in patients with genotype 1 infection (Figure 1C) and from in vitro replicon studies C316Y and Y448C were observed as main resistance mutations.106, 107 In addition, S556G was reported to be associated with viral breakthrough in a clinical study (Figure 4).106
NS5A Inhibitor
In a single ascending dose study it was shown that inhibition of the NS5A protein with BMS-790052 leads to a sharp initial decline of HCV-RNA concentrations (Figure 1D).108 BMS-790052 is the first NS5A inhibitor binding to domain I of the NS5A protein, which was shown to be important for regulation of HCV replication.109 No clinical data on resistance to this class of drugs have been presented yet and results of multiple dose studies have to be awaited.
Cyclophilin Inhibitors
Cyclophilins are functional regulators of the HCV NS5B polymerase.110 Debio-025, NIM811, and SCY-635 are cyclophilin A inhibitors, which block HCV replication in vitro.50, 111, 112 For Debio-025 antiviral activities in patients infected with different HCV genotypes (1–4) was shown during monotherapy and in combination studies with pegylated interferon (Figure 1D).18, 113 No viral breakthrough was observed in these studies. However, selection of HCV variants with mutations clustering in the NS5A gene resistant to Debio-025 was possible in the HCV replicon system.51, 112 Another cyclophilin inhibitor SCY-635 also showed antiviral activity in genotype 1–infected patients (Figure 1D).50 During this 14-day monotherapy study no viral breakthrough was reported. In vitro mutations within the NS5A (T17A, E295K, V444A) and NS5B (T77K, I432V) protein conferred resistance to SCY-635.114 No viral decline in genotype 1–infected patients treated with NIM811 alone was observed in a phase 1 study (Figure 1D).115 However, selection of cell lines conferring resistance to NIM811 without disclosure of the mutations observed was shown in the replicon system.111 Taken together, cyclophilin inhibitors may have the potential of broad antiviral activity to different HCV genotypes. However, selection of resistant variants is possible and the natural- and treatment-induced frequency of mutations conferring resistance to the different cyclophilin inhibitors have to be explored.116, 117
Nitazoxanide
Nitazoxanide is a thiazolide anti-infective with activity against anaerobic bacteria, protozoa, and viruses. It is approved for treatment of cryptosporidiosis and lambliasis in the United States. In vitro nitazoxanide was shown to inhibit HCV replication and the mechanism of action was proposed to be induction of double-strand RNA activated protein kinase.118 In a placebo-controlled study monotherapy with nitazoxanide for 24 weeks led to a mean reduction of HCV-RNA viral load in genotype 4–infected patients by 1.55 log10 IU/mL with 30% of patients having undetectable HCV RNA at the end of treatment.19 Studies in genotype 1–infected patients with a lead-in monotherapy with nitazoxanide for 4 weeks have been performed. However, no virologic response data in genotype 1–infected patients during monotherapy with nitazoxanide have been reported (Figure 1D).21, 119 Patients experiencing viral breakthroughs were not reported from monotherapy studies. However, in vitro studies suggested the potential of resistance to nitazoxanide most likely was conferred by changes in host proteins and not by mutations in the virus.118
Silibinin
The mechanism of action of silibinin is unknown but inhibition of NS5B polymerase as well as antiviral and anti-inflammatory activities shown in NS5B polymerase assays, in human peripheral blood mononuclear cells, and the HCV replicon, respectively, have been reported.120, 121 Monotherapy studies with daily intravenous application of silibinin in genotype 1–, 2–, and 3–infected patients for up to 14 days showed good antiviral activities (Figure 1D).22 Studies in larger cohorts of patients including resistance analysis are underway.
Conclusions
The development of DAA agents has increased the number of therapeutic options for patients with HCV infection. Data from phase 2 studies have shown that rates of sustained virologic response significantly improve in patients given triple therapies of a DAA agent, pegylated interferon, and ribavirin. However, these approaches also have many restrictions and raise some new problems and questions. Because of the high level of genomic heterogeneity among HCV subtypes and isolates, DAA agents will not have similar levels of activities in all patients. Most reagents are being developed to treat patients infected with HCV genotype 1. Although sustained virologic response rates are increasing among these patients, triple therapy is not effective in all patients infected with genotype 1 because of side effects, nonresponsiveness to pegylated interferon or ribavirin, or development of resistance. It is important to increase our understanding of mechanisms of resistance mutations, viral breakthrough, and relapse after therapy with DAA agents. Improving our knowledge of these processes will require more precise and earlier characterization of resistance profiles of patients given monotherapy, long-term follow-up data, and studies with combination therapies. Studies also are underway to test the effects of combinations of DAA agents without interferon alfa or ribavirin—these trials will provide valuable information about the ability of DAA agents to suppress HCV replication without development of resistance or even to eradicate the virus.
Thursday, March 4, 2010
Positive HBV Vaccine Response Halves HIV Progression and Death Risk in US Military
Positive HBV Vaccine Response Halves HIV Progression and Death Risk in US Military
17th Conference on Retroviruses and Opportunistic Infections, February 16-19, 2010, San Francisco
Mark Mascolini
A positive response to hepatitis B virus (HBV) vaccination approximately halved the risk of HIV disease progression or death in members of the US Military HIV Natural History Study, regardless of antiretroviral exposure or CD4 count [1]. The results underline the critical importance of HBV vaccination among people infected with HIV.
In addition, Michael Landrum and colleagues suggested, "HBV vaccine response may serve as a useful indicator for studying immunological correlates of HIV-related disease progression that are independent of the HIV RNA load or level of immune deficiency reflected by the CD4 count."
Earlier work by these researchers found that HBV vaccination did not lower the overall risk of HBV infection in this cohort, but they linked a vigorous vaccine response to a lower risk of chronic HBV infection, and chronic HBV and HBV vaccine response were associated with CD4 count and HIV load [2-4].
People eligible for this study at seven military care centers had a documented date of HIV infection and had not received an HBV vaccine before their HIV diagnosis. After testing positive for HIV, they received at least one HBV vaccine dose and had anti-hepatitis B surface (HBs) antigen measured 3 to 9 months after their last dose. Landrum and coworkers defined a positive vaccine response at anti-HBs antigen at or above 10 IU/L and nonresponse as a lower anti-HBs antigen level.
Study participants included 217 HBV vaccine responders and 409 nonresponders. Both groups had a median age around 32 years, and about 90% were men. Median CD4 counts stood at 505 in responders and 480 in nonresponders, a significant difference (P < 0.01). Median nadir CD4 count was higher in responders (398 versus 352, P < 0.01), and median viral load was lower (2.30 versus 3.62 log, P < 0.01). A higher proportion of responders than nonresponders got three or more HBV vaccine shots (70% versus 57%, P < 0.01), and responders were vaccinated more recently (median 2000 versus 1997, P < 0.01).
During a median follow-up of 5 years, 19 responders (9%) and 102 nonresponders (25%) had a new AIDS diagnosis or died (P <0.001 in a comparison unadjusted for other progression risk factors). To determine risk of progression or death, Landrum and colleagues devised a multivariate model that considered age, ethnicity, HIV duration before last HBV vaccination, number of vaccines doses, and year of last HBV vaccination.
That model determined that HBV vaccination lowered the risk of progression or death 42% (hazard ratio [HR] 0.58, 95% confidence interval [CI] 0.34 to 0.98, P = 0.04). Among people naive to antiretrovirals at their last HBV vaccine dose, vaccination halved the risk of progression or death (HR 0.50, 95% CI 0.27 to 0.91, P = 0.02). And among people naive to antiretrovirals at last vaccination and with a CD4 count above 349, vaccination also halved the risk of progression or death (HR 0.50, 95% CI 0.25 to 1.01, P = 0.05).
Because the study group consisted largely of young men receiving free care, the findings may not apply to all HIV populations.
Landrum and coworkers proposed that "response to HBV vaccine following immunization during HIV infection may be a useful independent predictor of clinical HIV-related disease progression, and may provide a functional assessment of immune function in such individuals."
References
1. Landrum M, Huppler Hullsiek K, Crum-Cianflone N, et al. Hepatitis B vaccine response predicts progression to clinical AIDS or death. 17th Conference on Retroviruses and Opportunistic Infections. February 16-19, 2010. San Francisco. Abstract 625. http://www.retroconference.org/2010/PDFs/625.pdf.
2. Landrum ML, Hullsiek KH, Ganesan A, et al. Hepatitis B vaccination and risk of hepatitis B infection in HIV-infected individuals. AIDS. 2009. Epub ahead of print.
3. Landrum ML, Fieberg AM, Chun HM, et al. The effect of human immunodeficiency virus on hepatitis B virus serological status in co-infected adults. PLoS One. 2010;5:e8687. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0008687.
4. Landrum ML, Huppler Hullsiek K, Ganesan A, et al. Hepatitis B vaccine responses in a large U.S. military cohort of HIV-infected individuals: another benefit of HAART in those with preserved CD4 count. Vaccine. 2009;27;4731-4738.
17th Conference on Retroviruses and Opportunistic Infections, February 16-19, 2010, San Francisco
Mark Mascolini
A positive response to hepatitis B virus (HBV) vaccination approximately halved the risk of HIV disease progression or death in members of the US Military HIV Natural History Study, regardless of antiretroviral exposure or CD4 count [1]. The results underline the critical importance of HBV vaccination among people infected with HIV.
In addition, Michael Landrum and colleagues suggested, "HBV vaccine response may serve as a useful indicator for studying immunological correlates of HIV-related disease progression that are independent of the HIV RNA load or level of immune deficiency reflected by the CD4 count."
Earlier work by these researchers found that HBV vaccination did not lower the overall risk of HBV infection in this cohort, but they linked a vigorous vaccine response to a lower risk of chronic HBV infection, and chronic HBV and HBV vaccine response were associated with CD4 count and HIV load [2-4].
People eligible for this study at seven military care centers had a documented date of HIV infection and had not received an HBV vaccine before their HIV diagnosis. After testing positive for HIV, they received at least one HBV vaccine dose and had anti-hepatitis B surface (HBs) antigen measured 3 to 9 months after their last dose. Landrum and coworkers defined a positive vaccine response at anti-HBs antigen at or above 10 IU/L and nonresponse as a lower anti-HBs antigen level.
Study participants included 217 HBV vaccine responders and 409 nonresponders. Both groups had a median age around 32 years, and about 90% were men. Median CD4 counts stood at 505 in responders and 480 in nonresponders, a significant difference (P < 0.01). Median nadir CD4 count was higher in responders (398 versus 352, P < 0.01), and median viral load was lower (2.30 versus 3.62 log, P < 0.01). A higher proportion of responders than nonresponders got three or more HBV vaccine shots (70% versus 57%, P < 0.01), and responders were vaccinated more recently (median 2000 versus 1997, P < 0.01).
During a median follow-up of 5 years, 19 responders (9%) and 102 nonresponders (25%) had a new AIDS diagnosis or died (P <0.001 in a comparison unadjusted for other progression risk factors). To determine risk of progression or death, Landrum and colleagues devised a multivariate model that considered age, ethnicity, HIV duration before last HBV vaccination, number of vaccines doses, and year of last HBV vaccination.
That model determined that HBV vaccination lowered the risk of progression or death 42% (hazard ratio [HR] 0.58, 95% confidence interval [CI] 0.34 to 0.98, P = 0.04). Among people naive to antiretrovirals at their last HBV vaccine dose, vaccination halved the risk of progression or death (HR 0.50, 95% CI 0.27 to 0.91, P = 0.02). And among people naive to antiretrovirals at last vaccination and with a CD4 count above 349, vaccination also halved the risk of progression or death (HR 0.50, 95% CI 0.25 to 1.01, P = 0.05).
Because the study group consisted largely of young men receiving free care, the findings may not apply to all HIV populations.
Landrum and coworkers proposed that "response to HBV vaccine following immunization during HIV infection may be a useful independent predictor of clinical HIV-related disease progression, and may provide a functional assessment of immune function in such individuals."
References
1. Landrum M, Huppler Hullsiek K, Crum-Cianflone N, et al. Hepatitis B vaccine response predicts progression to clinical AIDS or death. 17th Conference on Retroviruses and Opportunistic Infections. February 16-19, 2010. San Francisco. Abstract 625. http://www.retroconference.org/2010/PDFs/625.pdf.
2. Landrum ML, Hullsiek KH, Ganesan A, et al. Hepatitis B vaccination and risk of hepatitis B infection in HIV-infected individuals. AIDS. 2009. Epub ahead of print.
3. Landrum ML, Fieberg AM, Chun HM, et al. The effect of human immunodeficiency virus on hepatitis B virus serological status in co-infected adults. PLoS One. 2010;5:e8687. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0008687.
4. Landrum ML, Huppler Hullsiek K, Ganesan A, et al. Hepatitis B vaccine responses in a large U.S. military cohort of HIV-infected individuals: another benefit of HAART in those with preserved CD4 count. Vaccine. 2009;27;4731-4738.
Activation of CD8 T Cells Predicts Progression of HIV Infection in Women Coinfected with Hepatitis C Virus
Activation of CD8 T Cells Predicts Progression of HIV Infection in Women Coinfected with Hepatitis C Virus
"HCV coinfection was associated with increased CD8 activation. Finally, our most important finding was the statistically significant association between the level of activated CD8 T cells and incident AIDS among HCV‐positive viremic women. HCV‐positive viremic women with >43% activated CD8 T cells had an almost 3‐fold increased risk of AIDS‐defining conditions and/or AIDS‐related deaths compared with HCV‐positive viremic women with <26% activated CD8 T cells. This was not found for HCV‐negative women"........Ongoing antigen‐driven activation of CD8 T cells ultimately leads to CD8 T cell exhaustion and replicative senescence, which lead to inability to fight opportunistic pathogens....... factors that drive immune activation may increase the available targets for further viral replication. Finally, HCV infection may impair T cell maturation more globally to a more immature primed activated phenotype and also may impair responses to Toll‐like receptors, suggesting that both the innate and adaptive arms are affected [24, 39].....Animal studies have suggested that immune activation, rather than viral load, is linked to HIV disease progression [8].....The 592 women with immune activation data were slightly older (mean age, 37.4 vs 35.5 years); were more likely African American or Hispanic (82.5% vs 77.5%), injection drug users (53% vs 27%), and smokers (58% vs 49%); and had higher CD4 cell counts (mean, 439 vs 403 cells/μL) and CD8 cell counts (mean, 964 vs 867 cells/μL) than women without these data (data not shown)."
The Journal of Infectious Diseases March 15 2010
"...HCV‐positive viremic women had a statistically significantly higher percentage of activated CD8 T cells (p<.001)...
...HCV‐positive viremic women with HIV coinfection who have high levels of T cell activation may have increased risk of AIDS...
....In adjusted generalized estimating equation models, percentage of CD8+CD38+DR+ T cells was statistically significantly positively associated with HCV status (p=.04). Other independent correlates of CD8 activation included HIV RNA level and ART.......HCV‐positive viremic women were more likely to have bacterial pneumonia (20% vs 13%; p=.002 ), dementia and/or encephalopathy (11% vs 7%; p=.02), and wasting syndrome (12% vs 8%; p=.03) than were HCV‐negative women.....HCV‐positive viremic women were more likely to develop AIDS with an HCV RNA level of >2.3 million IU/mL.....and were more likely to die an AIDS‐related death with an HCV RNA level of >3.98 million IU/mL...
....Immune activation has been closely linked to HIV disease progression [1, 4, 5, 34–36], but to our knowledge this association has not previously been reported in the setting of HCV coinfection....
.....our findings from this large cohort study, which included 1307 women, are notable: HCV coinfection was associated with increased CD8 activation. Finally, our most important finding was the statistically significant association between the level of activated CD8 T cells and incident AIDS among HCV‐positive viremic women. HCV‐positive viremic women with >43% activated CD8 T cells had an almost 3‐fold increased risk of AIDS‐defining conditions and/or AIDS‐related deaths compared with HCV‐positive viremic women with <26% activated CD8 T cells. This was not found for HCV‐negative women.....data suggest that the increased risk of HIV disease progression among HCV‐coinfected women with high levels of CD8 activation may be due to immune dysfunction....
....We determined that (1) HCV viremia is associated with AIDS outcome, independent of injection drug use, HIV RNA level, CD4 cell count, and ART (Table 2); (2) HCV viremia is associated with CD4 and CD8 activation, independent of HIV RNA level (Table 3); and (3) high levels of CD8 activation are associated with AIDS in HCV‐positive viremic women but not in HCV‐negative women.....
.....In conclusion, our study demonstrates that HIV‐coinfected HCV‐positive viremic women are at increased risk for AIDS‐defining conditions compared with HCV‐negative women, possibly because of high levels of activation of T cells, especially CD8 T cells, which indicates increased immune dysregulation in this population of women. Lower levels of activation of both CD8 and CD4 T cells and activation of CD8 T cells expressing only HLA‐DR is protective against AIDS. Further study is needed to understand better the pathogenesis of T cell activation, especially of CD8 T cells in relation to HIV disease. HCV‐positive viremic women may benefit from treatment of HIV and HCV infection to prevent significant immunologic changes and improve long‐term outcome. Assessing CD4 and CD8 T cell activation could help clinicians evaluate their patients’ risk of developing AIDS.....
.....CD8+CD38−DR+ T cells appear to have high proliferative capacity and cytotoxic activity upon antigenic stimulation. Our study results suggest further research is needed to better understand the path of CD8 activation, especially the protective effect of HLA‐DR expression.....
...HCV viremic women were more likely to report wasting syndrome, bacterial pneumonia, and encephalopathy at the end of follow‐up....
.....Our multivariate models showed that the causal pathway between T cell activation and HIV disease progression cannot be completely explained by HIV or HCV viral load, and other mediators of CD8 activation may be involved in increasing AIDS risk. This may be because substantial immune activation occurs in tissues such as the liver, and viral load may not reflect the extent of the activation....Whether the liver plays a role in amplifying or modulating this activation, especially with prior HCV infection, is unknown, but a recent study found evidence of increased microbial translocation among HCV‐positive individuals with cirrhosis......
......This finding suggests that HCV‐positive viremic women may be at continued risk for certain AIDS‐defining conditions and further supports the importance of treatment in this group. The pathogenesis of these findings may be HCV‐related infection of the central nervous system and/or progressive liver disease including cirrhosis. Bacterial pneumonia is increased among HIV‐infected individuals, especially injection drug users [44, 45], and cirrhosis may play a role in some who are coinfected with HCV. However, continued immune activation is also associated with encephalopathy, and some studies have suggested that microbial translocation related to gut‐associated immunodeficiency may be a contributing factor [43, 46–48]. Furthermore, wasting syndrome may be a manifestation of chronic and severe gut‐associated immunodeficiency that may be exacerbated by progressive HCV disease and/or alcohol use.......
.......In vitro studies have shown that CD8 T cells have a lower threshold for activation and proliferation compared with CD4 T cells [37]. Ongoing antigen‐driven activation of CD8 T cells ultimately leads to CD8 T cell exhaustion and replicative senescence, which lead to inability to fight opportunistic pathogens [4]. The factors that influence T cell activation among the women included in our study are most likely multifactorial and may be a direct consequence of activation in the liver or may be related to extrahepatic replication of HCV [38]. Alternatively, host‐specific factors (eg, cytokines) may drive persistent T cell activation. Furthermore, factors that drive immune activation may increase the available targets for further viral replication. Finally, HCV infection may impair T cell maturation more globally to a more immature primed activated phenotype and also may impair responses to Toll‐like receptors, suggesting that both the innate and adaptive arms are affected [24, 39]."
Andrea Kovacs,1 Roksana Karim,1,2 Wendy J. Mack,2 Jiaao Xu,1 Zhi Chen,1 Eva Operskalski,1 Toni Frederick,1 Alan Landay,4 John Voris,4 La Shonda Spencer,1 Mary A. Young,5 Phyllis C. Tien,3 Michael Augenbraun,6 Howard D. Strickler,7 and Lena Al‐Harthi3
1Maternal, Child, and Adolescent Center for Infectious Diseases and Virology and 2Department of Preventive Medicine, University of Southern California Keck School of Medicine, Los Angeles, and 3Department of Medicine, University of California, San Francisco, and San Francisco Veterans Affairs Medical Center, San Francisco, California; 4Department of Immunology and Microbiology, Rush University Medical Center, Chicago, Illinois; 5Division of Infectious Diseases, Georgetown University, Washington, D.C.; 6Department of Medicine, State University of New York Downstate College of Medicine, Brooklyn, and 7Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York
ABSTRACT
Background. Because activation of T cells is associated with human immunodeficiency virus (HIV) pathogenesis, CD4 and CD8 activation levels in patients coinfected with HIV and hepatitis C virus (HCV) may explain conflicting reports regarding effects of HCV on HIV disease progression.
Methods. Kaplan‐Meier and multivariate Cox regression models were used to study the risk of incident clinical AIDS and AIDS‐related deaths among 813 HCV‐negative women with HIV infection, 87 HCV‐positive nonviremic women with HIV coinfection, and 407 HCV‐positive viremic women with HIV coinfection (median follow‐up time, 5.2 years). For 592 women, the percentages of activated CD4 and CD8 T cells expressing HLA‐DR (DR) and/or CD38 were evaluated.
Results. HCV‐positive viremic women had a statistically significantly higher percentage of activated CD8 T cells (p<.001) and a statistically significantly higher incidence of AIDS compared with HCV‐negative women (p<.001 [log‐rank test]). The AIDS risk was greater among HCV‐positive viremic women in the highest tertile compared with the lowest tertile (>43% vs <26%) of CD8+CD38+DR+ T cells (hazard ratio, 2.94 [95% confidence interval, 1.50–5.77]; p=.001). This difference was not observed in the HCV‐negative women (hazard ratio, 1.87 [95% confidence interval, 0.80–4.35]; p=.16). In contrast, CD4 activation predicted AIDS in both groups similarly. Increased percentages of CD8+CD38−DR+, CD4+CD38−DR−, and CD8+CD38−DR− T cells were associated with a >60% decreased risk of AIDS for HCV‐positive viremic women and HCV‐negative women.
Conclusion. HCV‐positive viremic women with HIV coinfection who have high levels of T cell activation may have increased risk of AIDS. Earlier treatment of HIV and HCV infection may be beneficial.
Persistent generalized immune activation is a hallmark of human immunodeficiency virus (HIV) infection and is associated with CD4 cell count and HIV RNA level [1–7]. Activation of T cells accelerates their maturation and is associated with decreased CD4 level, increased HIV replication, more rapid HIV disease progression, and a decreased amount of CD4 gain following highly active antiretroviral therapy. Animal studies have suggested that immune activation, rather than viral load, is linked to HIV disease progression [8].
Worldwide, many HIV‐infected individuals are coinfected with hepatitis C virus (HCV). However, studies of the effect of HCV on HIV disease progression have been conflicting [9–19]. In contrast, all studies find liver disease to be accelerated in HIV‐coinfected patients compared with patients singly infected with HCV [20–22]. Determining the association between HCV and HIV is critical for clinical management of both infections in coinfected patients. We assessed the effect of HIV and HCV on HIV disease progression in a prospective cohort of women, and we determined the percentages of CD4 and CD8 T cells that expressed the cell surface markers HLA‐DR (DR) and/or CD38 as measures of immune activation. We hypothesized that the combined effects of these 2 viruses would be increased immune activation and higher likelihood of HIV disease progression.
Results
Demographic and baseline clinical characteristics of study participants.Among the 1307 women included in the study, there were 813 HCV‐negative women (62%), 87 HCV‐positive nonviremic women (7%), and 407 HCV‐positive viremic women (31%). Among the 260 HCV‐positive viremic women for whom HCV genotype was determined, 210 (80%) were infected with genotype 1. HCV‐positive women were older and more likely to be injection drug users than HCV‐negative women (Table 1). Number of sexual partners and CD4 and CD8 cell counts were similar among the groups. The overall prevalence of injection drug use during the follow‐up period was 0.4% (range, 0%–1%) in HCV‐negative women, 10.5% (range, 0%–21%) in HCV‐positive nonviremic women, and 12.7% (range, 6%–26%) in HCV‐positive viremic women (p<.001 [χ2 test]; data not shown). Although anti‐HCV therapy was not generally given during the period of this study, 19 of 1307 women received interferon, the majority after the 10th visit. Among these 19 women, there were 14 HCV‐positive viremic women, 1 HCV‐positive nonviremic woman, and 4 HCV‐negative women. None of these women received ribavirin.
The 592 women with immune activation data were slightly older (mean age, 37.4 vs 35.5 years); were more likely African American or Hispanic (82.5% vs 77.5%), injection drug users (53% vs 27%), and smokers (58% vs 49%); and had higher CD4 cell counts (mean, 439 vs 403 cells/μL) and CD8 cell counts (mean, 964 vs 867 cells/μL) than women without these data (data not shown).
Disease progression and HCV.Among the 1307 women who were AIDS free at baseline, 495 developed AIDS, including 162 women who died an AIDS‐related death during 10 years of follow‐up. Although at the time of first AIDS diagnosis there were no statistically significant differences in reported individual AIDS‐defining conditions between HCV‐negative women and HCV‐positive women, by the end of follow‐up HCV‐positive viremic women were more likely to have bacterial pneumonia (20% vs 13%; ), dementia and/or encephalopathy (11% vs 7%; ), and wasting syndrome (12% vs 8%; ) than were HCV‐negative women. By the end of follow‐up, HCV‐positive viremic women were also more likely to have tuberculosis than were HCV‐negative women; however, the difference was borderline statistically significant (6% vs 4%; ). HCV‐positive viremic women were less likely to have any cancer (5% vs 8%; ) and toxoplasmosis (0.6% vs 2%; ) than were HCV‐negative women.
Kaplan‐Meier analyses showed that HCV‐positive viremic women were more likely to develop AIDS with an HCV RNA level of >2.3 million IU/mL (Figure 3A) and were more likely to die an AIDS‐related death with an HCV RNA level of >3.98 million IU/mL (Figure 3B) than were women in the other groups ( and , respectively [log‐rank test]). Among women who never had a CD4 cell count of <200 cells/μL, HCV‐positive women (regardless of HCV RNA status) were more likely to develop AIDS than were HCV‐negative women (Figure 3C), with rates at 1, 3, and 5 years after study entry of 13% vs 7%, 26% vs 16%, and 33% vs 21%, respectively ( ).
Disease progression and HCV.
Among the 1307 women who were AIDS free at baseline, 495 developed AIDS, including 162 women who died an AIDS‐related death during 10 years of follow‐up. Although at the time of first AIDS diagnosis there were no statistically significant differences in reported individual AIDS‐defining conditions between HCV‐negative women and HCV‐positive women, by the end of follow‐up HCV‐positive viremic women were more likely to have bacterial pneumonia (20% vs 13%; p=.002), dementia and/or encephalopathy (11% vs 7%; p=.02), and wasting syndrome (12% vs 8%; p=.03) than were HCV‐negative women. By the end of follow‐up, HCV‐positive viremic women were also more likely to have tuberculosis than were HCV‐negative women; however, the difference was borderline statistically significant (6% vs 4%; p=.06). HCV‐positive viremic women were less likely to have any cancer (5% vs 8%; ) and toxoplasmosis (0.6% vs 2%; ) than were HCV‐negative women.
Kaplan‐Meier analyses showed that HCV‐positive viremic women were more likely to develop AIDS with an HCV RNA level of >2.3 million IU/mL (Figure 3A) and were more likely to die an AIDS‐related death with an HCV RNA level of >3.98 million IU/mL (Figure 3B) than were women in the other groups (p<.001 and p=.03, respectively [log‐rank test]). Among women who never had a CD4 cell count of <200 cells/μL, HCV‐positive women (regardless of HCV RNA status) were more likely to develop AIDS than were HCV‐negative women (Figure 3C), with rates at 1, 3, and 5 years after study entry of 13% vs 7%, 26% vs 16%, and 33% vs 21%, respectively (p<.001).
After adjusting for age, race, smoking, and ART, we found HCV status, injection drug use, CD4 cell count, and HIV plasma RNA level to be independent risk factors for AIDS‐defining conditions in the Cox model (Table 2). Compared with women who never had a CD4 cell count of <200 cells/μL, women with a current and previous CD4 cell count of <200 cells/μL had a 3‐fold increased risk of AIDS and AIDS‐related death (HR, 3.48 [95% CI, 2.77–4.36]). This was confirmed in a separate model that assessed visit‐specific CD4 cell counts of <200 vs >500 cells/μL (HR, 3.00 [95% CI, 2.26–4.00]; data not shown). Alcohol use, prophylactic antibiotic use, and aspartate to platelet ratio index were not statistically significant predictors of AIDS, and their inclusion in multivariate models did not alter HR estimates for injection drug use, HCV status, CD4 cell count, and HIV RNA levels. Among ART‐naive women, HCV‐positive viremic women had a 2‐fold higher risk of AIDS compared with HCV‐negative women (data not shown).
Association between level of immune activation and HCV status.
HCV status was statistically significantly correlated with CD8+CD38+DR+ and CD4+CD38+DR+ T cell levels in univariate analyses (Table 3). In adjusted generalized estimating equation models, percentage of CD8+CD38+DR+ T cells was statistically significantly positively associated with HCV status (p=.04). Other independent correlates of CD8 activation included HIV RNA level and ART. For CD4+CD38+DR+ T cells, there was no statistically significant positive trend overall by HCV status. However, after the HCV‐negative group was removed from the analysis, the trend was statistically significant among HCV‐positive women (p=.02).
Immune activation and risk of AIDS.
Among the 592 women with immune activation data, AIDS risk was statistically significantly increased among women in the highest tertile of CD8+CD38+DR+ T cells compared with women in the lowest tertile of CD8+CD38+DR+ T cells, and among women in the highest tertile of CD4+CD38+DR+ T cells compared with women in the lowest tertile of CD4+CD38+DR+ T cells (Table 4). In contrast, higher percentages of CD8+CD38−DR−, CD8+CD38−DR+, and CD4+CD38−DR− T cells were statistically significantly protective against AIDS. When we adjusted for HIV RNA level, these associations remained unchanged. However, after adjusting for CD4 cell count or CD4 cell count and HIV RNA level, HRs remained statistically significant only for CD8+CD38−DR+ and CD4+CD38+DR+ T cells. Of note, HRs for each HCV RNA level were not statistically significant in any immune marker models: in model 1 for CD8+CD38+DR+ T cells, the HR was 0.94 (95% CI, 0.48–1.82) for HCV‐positive nonviremic women and 0.88 (95% CI, 0.45–1.73), 1.67 (95% CI, 0.62–2.20), 1.14 (95% CI, 0.61–2.17), and 1.14 (95% CI, 0.60–2.17) for HCV‐positive viremic women with RNA levels of 983,000, 983,001–2,395,000, 2,395,001–3,980,000, and >3,980,001 IU/mL, respectively.
Immune activation and risk of AIDS in HCV‐negative and HCV‐positive viremic women.
Stratified analyses showed that among HCV‐positive viremic women (n=278), AIDS risk was statistically significantly increased with higher percentages of CD8+CD38+DR+ and CD4+CD38+DR+ T cells (Table 4). However, for HCV‐negative women, percentage of CD8+CD38+DR+ T cells was not statistically significantly associated with AIDS. Conversely, higher percentages of CD4+CD38−DR−, CD8+CD38−DR−, and CD8+CD38−DR+ T cells were associated with decreased AIDS risk for both groups. After additional adjustments for HIV RNA level, CD4 cell count, or both, risk was altered but remained statistically significant for CD8+CD38−DR+ and CD4+CD38+DR+ T cells and was borderline statistically significant for CD8+CD38+DR+ T cells only among HCV‐positive viremic women. For HCV‐negative women (n=242), HRs remained statistically significant only for CD8+CD38−DR+ and CD4+CD38+DR+ T cells after adjusting for HIV RNA level (Table 4). HRs were not statistically significantly different between HCV‐positive viremic women and HCV‐negative women (p>.50 for all interactions).
Discussion
HIV‐positive patients with chronic active or reactivating viral coinfections (eg, cytomegalovirus or herpes simplex virus coinfections) have higher plasma HIV RNA levels, lower T cell counts, and greater progression to AIDS compared with HIV‐positive patients without evidence of infection/reactivation [31, 32]. For HCV coinfection, however, there have been conflicting reports [10–19]. Consequently, our findings from this large cohort study, which included 1307 women, are notable. First, women with high baseline HCV RNA levels have an increased risk of AIDS, independent of CD4 cell count and HIV RNA level. Second, there was an almost 2‐fold increased probability of developing AIDS for HCV‐positive women compared with HCV‐negative women who never had a CD4 cell count of <200 cells/μL and for women who remained ART naive. Third, HCV coinfection was associated with increased CD8 activation. Finally, our most important finding was the statistically significant association between the level of activated CD8 T cells and incident AIDS among HCV‐positive viremic women. HCV‐positive viremic women with >43% activated CD8 T cells had an almost 3‐fold increased risk of AIDS‐defining conditions and/or AIDS‐related deaths compared with HCV‐positive viremic women with <26% activated CD8 T cells. This was not found for HCV‐negative women. In contrast, high levels of CD4 activation similarly predicted AIDS in both groups of women. These data suggest that the increased risk of HIV disease progression among HCV‐coinfected women with high levels of CD8 activation may be due to immune dysfunction. Importantly, we also showed that women with high percentages of CD8+CD38−DR+ and CD4+CD38−DR− or CD8+CD38−DR− T cells had a 50%–70% decreased AIDS risk, which suggests better immunity among this group of women.
To our knowledge, the Swiss HIV Cohort Study [17] was the first large study to demonstrate that HCV accelerated HIV disease independent of injection drug use. Other studies found no effect of HCV on HIV disease progression, although recent studies have reported increased risk [9–19]. Our study, in which only 10%–20% of the participants were active injection drug users during follow‐up, demonstrates an increased risk of an AIDS‐defining condition with increasing HCV RNA level. Furthermore, our study assessed outcome from the time of study entry to the time of an AIDS‐defining condition adjusting for ART in time‐dependent Cox models, whereas some studies limited outcome from initiation of highly active ART or excluded women with CD4 cell counts of <200 cells/μL at baseline, neither of which was done in our study. Although the effect of HCV genotype on immune activation is unknown, most women in our study were infected with genotype 1, which is associated with higher HCV RNA levels [33]. In our study, higher HCV RNA levels correlate with higher levels of immune activation. Differences in genotype or in rates of active injection drug use may explain differences between the results of our study and those in previous reports [19].
Immune activation has been closely linked to HIV disease progression [1, 4, 5, 34–36], but to our knowledge this association has not previously been reported in the setting of HCV coinfection. Our finding of increased incidence of AIDS‐defining conditions in relation to high levels of immune activation suggests that there is impaired T cell function in HCV‐positive viremic women that may potentially put them at higher risk of HIV disease progression compared with HCV‐negative women.
There are a number of factors that could potentially influence immune activation and in turn pathogenesis of HIV disease, including age, race, gender, injection drugs, use of highly active ART and antibiotic prophylaxis, smoking, alcohol, HCV genotype, and extent of liver damage. We evaluated for each of these in univariate models and then in multivariate models when appropriate.
In vitro studies have shown that CD8 T cells have a lower threshold for activation and proliferation compared with CD4 T cells [37]. Ongoing antigen‐driven activation of CD8 T cells ultimately leads to CD8 T cell exhaustion and replicative senescence, which lead to inability to fight opportunistic pathogens [4]. The factors that influence T cell activation among the women included in our study are most likely multifactorial and may be a direct consequence of activation in the liver or may be related to extrahepatic replication of HCV [38]. Alternatively, host‐specific factors (eg, cytokines) may drive persistent T cell activation. Furthermore, factors that drive immune activation may increase the available targets for further viral replication. Finally, HCV infection may impair T cell maturation more globally to a more immature primed activated phenotype and also may impair responses to Toll‐like receptors, suggesting that both the innate and adaptive arms are affected [24, 39].
Our study systematically evaluated the association between HCV viremia, immune activation, and AIDS outcome. We determined that (1) HCV viremia is associated with AIDS outcome, independent of injection drug use, HIV RNA level, CD4 cell count, and ART (Table 2); (2) HCV viremia is associated with CD4 and CD8 activation, independent of HIV RNA level (Table 3); and (3) high levels of CD8 activation are associated with AIDS in HCV‐positive viremic women but not in HCV‐negative women. Our multivariate models showed that the causal pathway between T cell activation and HIV disease progression cannot be completely explained by HIV or HCV viral load, and other mediators of CD8 activation may be involved in increasing AIDS risk. This may be because substantial immune activation occurs in tissues such as the liver, and viral load may not reflect the extent of the activation. For instance, recently there has been evidence that the gastrointestinal tract is a site for activation of T cells as a result of microbial translocation. Gut‐associated T cell depletion may also have a significant effect on HIV pathogenesis [8, 40–42]. From the intestines, T cells and microbial antigens circulate directly through the liver, where activation may continue. Whether the liver plays a role in amplifying or modulating this activation, especially with prior HCV infection, is unknown, but a recent study found evidence of increased microbial translocation among HCV‐positive individuals with cirrhosis [43]. In our study, liver biopsy data were unavailable. However, we did evaluate for liver disease by use of the aspartate to platelet ratio index [30] and found no statistically significant correlation with AIDS risk. Furthermore, we found no association between alcohol use and AIDS outcome. On the other hand, although at the time of AIDS diagnosis there were no statistically significant differences in individual AIDS‐defining conditions noted between HCV‐negative women and HCV‐positive women, HCV viremic women were more likely to report wasting syndrome, bacterial pneumonia, and encephalopathy at the end of follow‐up. This finding suggests that HCV‐positive viremic women may be at continued risk for certain AIDS‐defining conditions and further supports the importance of treatment in this group. The pathogenesis of these findings may be HCV‐related infection of the central nervous system and/or progressive liver disease including cirrhosis. Bacterial pneumonia is increased among HIV‐infected individuals, especially injection drug users [44, 45], and cirrhosis may play a role in some who are coinfected with HCV. However, continued immune activation is also associated with encephalopathy, and some studies have suggested that microbial translocation related to gut‐associated immunodeficiency may be a contributing factor [43, 46–48]. Furthermore, wasting syndrome may be a manifestation of chronic and severe gut‐associated immunodeficiency that may be exacerbated by progressive HCV disease and/or alcohol use.
Our study results confirm those of previous studies that the presence of HLA‐DR on CD8 T cells without CD38 expression appears to be protective [36, 49]. This is consistent with reports showing that elite controllers have higher percentages of HIV‐specific and global CD8+CD38−DR+ T cells [49]. CD8+CD38−DR+ T cells appear to have high proliferative capacity and cytotoxic activity upon antigenic stimulation. Our study results suggest further research is needed to better understand the path of CD8 activation, especially the protective effect of HLA‐DR expression.
Although our study is unique, it has limitations. We did not have information on the timing of HIV or HCV infection. Furthermore, HCV‐positive women and HCV‐negative women may be different because of differing routes of HIV infection (injection drug use vs sexual). Immune activation markers were measured for only a subset of the study population [7, 24, 25], and not all phenotypic markers were measured at the same time. Nevertheless, our results confirmed previous observations by other investigators [1, 6, 36]. Finally, we evaluated HCV RNA levels only at baseline because not all women underwent multiple measures. We assumed that HCV RNA levels would not change substantially in women who were not treated for HCV infection, on the basis of published studies that found that even with initiation and discontinuation of highly active ART there is only a 0.43–0.59 log change in HCV viral load [50]; such small changes would not affect our findings.
In conclusion, our study demonstrates that HIV‐coinfected HCV‐positive viremic women are at increased risk for AIDS‐defining conditions compared with HCV‐negative women, possibly because of high levels of activation of T cells, especially CD8 T cells, which indicates increased immune dysregulation in this population of women. Lower levels of activation of both CD8 and CD4 T cells and activation of CD8 T cells expressing only HLA‐DR is protective against AIDS. Further study is needed to understand better the pathogenesis of T cell activation, especially of CD8 T cells in relation to HIV disease. HCV‐positive viremic women may benefit from treatment of HIV and HCV infection to prevent significant immunologic changes and improve long‐term outcome. Assessing CD4 and CD8 T cell activation could help clinicians evaluate their patients’ risk of developing AIDS.
Acknowledgment
We thank the participants of this study. Data in this manuscript were collected by the Women's Interagency HIV Study (WIHS) Collaborative Study Group, with centers (Principal Investigators) located at New York City/Bronx Consortium (Kathryn Anastos); Brooklyn, NY (Howard Minkoff); Washington DC Metropolitan Consortium (Mary Young); The Connie Wofsy Study Consortium of Northern California (Ruth Greenblatt); Los Angeles County/Southern California Consortium (Alexandra Levine); Chicago Consortium (Mardge Cohen); and Data Analysis Center (Stephen Gange). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health.
"HCV coinfection was associated with increased CD8 activation. Finally, our most important finding was the statistically significant association between the level of activated CD8 T cells and incident AIDS among HCV‐positive viremic women. HCV‐positive viremic women with >43% activated CD8 T cells had an almost 3‐fold increased risk of AIDS‐defining conditions and/or AIDS‐related deaths compared with HCV‐positive viremic women with <26% activated CD8 T cells. This was not found for HCV‐negative women"........Ongoing antigen‐driven activation of CD8 T cells ultimately leads to CD8 T cell exhaustion and replicative senescence, which lead to inability to fight opportunistic pathogens....... factors that drive immune activation may increase the available targets for further viral replication. Finally, HCV infection may impair T cell maturation more globally to a more immature primed activated phenotype and also may impair responses to Toll‐like receptors, suggesting that both the innate and adaptive arms are affected [24, 39].....Animal studies have suggested that immune activation, rather than viral load, is linked to HIV disease progression [8].....The 592 women with immune activation data were slightly older (mean age, 37.4 vs 35.5 years); were more likely African American or Hispanic (82.5% vs 77.5%), injection drug users (53% vs 27%), and smokers (58% vs 49%); and had higher CD4 cell counts (mean, 439 vs 403 cells/μL) and CD8 cell counts (mean, 964 vs 867 cells/μL) than women without these data (data not shown)."
The Journal of Infectious Diseases March 15 2010
"...HCV‐positive viremic women had a statistically significantly higher percentage of activated CD8 T cells (p<.001)...
...HCV‐positive viremic women with HIV coinfection who have high levels of T cell activation may have increased risk of AIDS...
....In adjusted generalized estimating equation models, percentage of CD8+CD38+DR+ T cells was statistically significantly positively associated with HCV status (p=.04). Other independent correlates of CD8 activation included HIV RNA level and ART.......HCV‐positive viremic women were more likely to have bacterial pneumonia (20% vs 13%; p=.002 ), dementia and/or encephalopathy (11% vs 7%; p=.02), and wasting syndrome (12% vs 8%; p=.03) than were HCV‐negative women.....HCV‐positive viremic women were more likely to develop AIDS with an HCV RNA level of >2.3 million IU/mL.....and were more likely to die an AIDS‐related death with an HCV RNA level of >3.98 million IU/mL...
....Immune activation has been closely linked to HIV disease progression [1, 4, 5, 34–36], but to our knowledge this association has not previously been reported in the setting of HCV coinfection....
.....our findings from this large cohort study, which included 1307 women, are notable: HCV coinfection was associated with increased CD8 activation. Finally, our most important finding was the statistically significant association between the level of activated CD8 T cells and incident AIDS among HCV‐positive viremic women. HCV‐positive viremic women with >43% activated CD8 T cells had an almost 3‐fold increased risk of AIDS‐defining conditions and/or AIDS‐related deaths compared with HCV‐positive viremic women with <26% activated CD8 T cells. This was not found for HCV‐negative women.....data suggest that the increased risk of HIV disease progression among HCV‐coinfected women with high levels of CD8 activation may be due to immune dysfunction....
....We determined that (1) HCV viremia is associated with AIDS outcome, independent of injection drug use, HIV RNA level, CD4 cell count, and ART (Table 2); (2) HCV viremia is associated with CD4 and CD8 activation, independent of HIV RNA level (Table 3); and (3) high levels of CD8 activation are associated with AIDS in HCV‐positive viremic women but not in HCV‐negative women.....
.....In conclusion, our study demonstrates that HIV‐coinfected HCV‐positive viremic women are at increased risk for AIDS‐defining conditions compared with HCV‐negative women, possibly because of high levels of activation of T cells, especially CD8 T cells, which indicates increased immune dysregulation in this population of women. Lower levels of activation of both CD8 and CD4 T cells and activation of CD8 T cells expressing only HLA‐DR is protective against AIDS. Further study is needed to understand better the pathogenesis of T cell activation, especially of CD8 T cells in relation to HIV disease. HCV‐positive viremic women may benefit from treatment of HIV and HCV infection to prevent significant immunologic changes and improve long‐term outcome. Assessing CD4 and CD8 T cell activation could help clinicians evaluate their patients’ risk of developing AIDS.....
.....CD8+CD38−DR+ T cells appear to have high proliferative capacity and cytotoxic activity upon antigenic stimulation. Our study results suggest further research is needed to better understand the path of CD8 activation, especially the protective effect of HLA‐DR expression.....
...HCV viremic women were more likely to report wasting syndrome, bacterial pneumonia, and encephalopathy at the end of follow‐up....
.....Our multivariate models showed that the causal pathway between T cell activation and HIV disease progression cannot be completely explained by HIV or HCV viral load, and other mediators of CD8 activation may be involved in increasing AIDS risk. This may be because substantial immune activation occurs in tissues such as the liver, and viral load may not reflect the extent of the activation....Whether the liver plays a role in amplifying or modulating this activation, especially with prior HCV infection, is unknown, but a recent study found evidence of increased microbial translocation among HCV‐positive individuals with cirrhosis......
......This finding suggests that HCV‐positive viremic women may be at continued risk for certain AIDS‐defining conditions and further supports the importance of treatment in this group. The pathogenesis of these findings may be HCV‐related infection of the central nervous system and/or progressive liver disease including cirrhosis. Bacterial pneumonia is increased among HIV‐infected individuals, especially injection drug users [44, 45], and cirrhosis may play a role in some who are coinfected with HCV. However, continued immune activation is also associated with encephalopathy, and some studies have suggested that microbial translocation related to gut‐associated immunodeficiency may be a contributing factor [43, 46–48]. Furthermore, wasting syndrome may be a manifestation of chronic and severe gut‐associated immunodeficiency that may be exacerbated by progressive HCV disease and/or alcohol use.......
.......In vitro studies have shown that CD8 T cells have a lower threshold for activation and proliferation compared with CD4 T cells [37]. Ongoing antigen‐driven activation of CD8 T cells ultimately leads to CD8 T cell exhaustion and replicative senescence, which lead to inability to fight opportunistic pathogens [4]. The factors that influence T cell activation among the women included in our study are most likely multifactorial and may be a direct consequence of activation in the liver or may be related to extrahepatic replication of HCV [38]. Alternatively, host‐specific factors (eg, cytokines) may drive persistent T cell activation. Furthermore, factors that drive immune activation may increase the available targets for further viral replication. Finally, HCV infection may impair T cell maturation more globally to a more immature primed activated phenotype and also may impair responses to Toll‐like receptors, suggesting that both the innate and adaptive arms are affected [24, 39]."
Andrea Kovacs,1 Roksana Karim,1,2 Wendy J. Mack,2 Jiaao Xu,1 Zhi Chen,1 Eva Operskalski,1 Toni Frederick,1 Alan Landay,4 John Voris,4 La Shonda Spencer,1 Mary A. Young,5 Phyllis C. Tien,3 Michael Augenbraun,6 Howard D. Strickler,7 and Lena Al‐Harthi3
1Maternal, Child, and Adolescent Center for Infectious Diseases and Virology and 2Department of Preventive Medicine, University of Southern California Keck School of Medicine, Los Angeles, and 3Department of Medicine, University of California, San Francisco, and San Francisco Veterans Affairs Medical Center, San Francisco, California; 4Department of Immunology and Microbiology, Rush University Medical Center, Chicago, Illinois; 5Division of Infectious Diseases, Georgetown University, Washington, D.C.; 6Department of Medicine, State University of New York Downstate College of Medicine, Brooklyn, and 7Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York
ABSTRACT
Background. Because activation of T cells is associated with human immunodeficiency virus (HIV) pathogenesis, CD4 and CD8 activation levels in patients coinfected with HIV and hepatitis C virus (HCV) may explain conflicting reports regarding effects of HCV on HIV disease progression.
Methods. Kaplan‐Meier and multivariate Cox regression models were used to study the risk of incident clinical AIDS and AIDS‐related deaths among 813 HCV‐negative women with HIV infection, 87 HCV‐positive nonviremic women with HIV coinfection, and 407 HCV‐positive viremic women with HIV coinfection (median follow‐up time, 5.2 years). For 592 women, the percentages of activated CD4 and CD8 T cells expressing HLA‐DR (DR) and/or CD38 were evaluated.
Results. HCV‐positive viremic women had a statistically significantly higher percentage of activated CD8 T cells (p<.001) and a statistically significantly higher incidence of AIDS compared with HCV‐negative women (p<.001 [log‐rank test]). The AIDS risk was greater among HCV‐positive viremic women in the highest tertile compared with the lowest tertile (>43% vs <26%) of CD8+CD38+DR+ T cells (hazard ratio, 2.94 [95% confidence interval, 1.50–5.77]; p=.001). This difference was not observed in the HCV‐negative women (hazard ratio, 1.87 [95% confidence interval, 0.80–4.35]; p=.16). In contrast, CD4 activation predicted AIDS in both groups similarly. Increased percentages of CD8+CD38−DR+, CD4+CD38−DR−, and CD8+CD38−DR− T cells were associated with a >60% decreased risk of AIDS for HCV‐positive viremic women and HCV‐negative women.
Conclusion. HCV‐positive viremic women with HIV coinfection who have high levels of T cell activation may have increased risk of AIDS. Earlier treatment of HIV and HCV infection may be beneficial.
Persistent generalized immune activation is a hallmark of human immunodeficiency virus (HIV) infection and is associated with CD4 cell count and HIV RNA level [1–7]. Activation of T cells accelerates their maturation and is associated with decreased CD4 level, increased HIV replication, more rapid HIV disease progression, and a decreased amount of CD4 gain following highly active antiretroviral therapy. Animal studies have suggested that immune activation, rather than viral load, is linked to HIV disease progression [8].
Worldwide, many HIV‐infected individuals are coinfected with hepatitis C virus (HCV). However, studies of the effect of HCV on HIV disease progression have been conflicting [9–19]. In contrast, all studies find liver disease to be accelerated in HIV‐coinfected patients compared with patients singly infected with HCV [20–22]. Determining the association between HCV and HIV is critical for clinical management of both infections in coinfected patients. We assessed the effect of HIV and HCV on HIV disease progression in a prospective cohort of women, and we determined the percentages of CD4 and CD8 T cells that expressed the cell surface markers HLA‐DR (DR) and/or CD38 as measures of immune activation. We hypothesized that the combined effects of these 2 viruses would be increased immune activation and higher likelihood of HIV disease progression.
Results
Demographic and baseline clinical characteristics of study participants.Among the 1307 women included in the study, there were 813 HCV‐negative women (62%), 87 HCV‐positive nonviremic women (7%), and 407 HCV‐positive viremic women (31%). Among the 260 HCV‐positive viremic women for whom HCV genotype was determined, 210 (80%) were infected with genotype 1. HCV‐positive women were older and more likely to be injection drug users than HCV‐negative women (Table 1). Number of sexual partners and CD4 and CD8 cell counts were similar among the groups. The overall prevalence of injection drug use during the follow‐up period was 0.4% (range, 0%–1%) in HCV‐negative women, 10.5% (range, 0%–21%) in HCV‐positive nonviremic women, and 12.7% (range, 6%–26%) in HCV‐positive viremic women (p<.001 [χ2 test]; data not shown). Although anti‐HCV therapy was not generally given during the period of this study, 19 of 1307 women received interferon, the majority after the 10th visit. Among these 19 women, there were 14 HCV‐positive viremic women, 1 HCV‐positive nonviremic woman, and 4 HCV‐negative women. None of these women received ribavirin.
The 592 women with immune activation data were slightly older (mean age, 37.4 vs 35.5 years); were more likely African American or Hispanic (82.5% vs 77.5%), injection drug users (53% vs 27%), and smokers (58% vs 49%); and had higher CD4 cell counts (mean, 439 vs 403 cells/μL) and CD8 cell counts (mean, 964 vs 867 cells/μL) than women without these data (data not shown).
Disease progression and HCV.Among the 1307 women who were AIDS free at baseline, 495 developed AIDS, including 162 women who died an AIDS‐related death during 10 years of follow‐up. Although at the time of first AIDS diagnosis there were no statistically significant differences in reported individual AIDS‐defining conditions between HCV‐negative women and HCV‐positive women, by the end of follow‐up HCV‐positive viremic women were more likely to have bacterial pneumonia (20% vs 13%; ), dementia and/or encephalopathy (11% vs 7%; ), and wasting syndrome (12% vs 8%; ) than were HCV‐negative women. By the end of follow‐up, HCV‐positive viremic women were also more likely to have tuberculosis than were HCV‐negative women; however, the difference was borderline statistically significant (6% vs 4%; ). HCV‐positive viremic women were less likely to have any cancer (5% vs 8%; ) and toxoplasmosis (0.6% vs 2%; ) than were HCV‐negative women.
Kaplan‐Meier analyses showed that HCV‐positive viremic women were more likely to develop AIDS with an HCV RNA level of >2.3 million IU/mL (Figure 3A) and were more likely to die an AIDS‐related death with an HCV RNA level of >3.98 million IU/mL (Figure 3B) than were women in the other groups ( and , respectively [log‐rank test]). Among women who never had a CD4 cell count of <200 cells/μL, HCV‐positive women (regardless of HCV RNA status) were more likely to develop AIDS than were HCV‐negative women (Figure 3C), with rates at 1, 3, and 5 years after study entry of 13% vs 7%, 26% vs 16%, and 33% vs 21%, respectively ( ).
Disease progression and HCV.
Among the 1307 women who were AIDS free at baseline, 495 developed AIDS, including 162 women who died an AIDS‐related death during 10 years of follow‐up. Although at the time of first AIDS diagnosis there were no statistically significant differences in reported individual AIDS‐defining conditions between HCV‐negative women and HCV‐positive women, by the end of follow‐up HCV‐positive viremic women were more likely to have bacterial pneumonia (20% vs 13%; p=.002), dementia and/or encephalopathy (11% vs 7%; p=.02), and wasting syndrome (12% vs 8%; p=.03) than were HCV‐negative women. By the end of follow‐up, HCV‐positive viremic women were also more likely to have tuberculosis than were HCV‐negative women; however, the difference was borderline statistically significant (6% vs 4%; p=.06). HCV‐positive viremic women were less likely to have any cancer (5% vs 8%; ) and toxoplasmosis (0.6% vs 2%; ) than were HCV‐negative women.
Kaplan‐Meier analyses showed that HCV‐positive viremic women were more likely to develop AIDS with an HCV RNA level of >2.3 million IU/mL (Figure 3A) and were more likely to die an AIDS‐related death with an HCV RNA level of >3.98 million IU/mL (Figure 3B) than were women in the other groups (p<.001 and p=.03, respectively [log‐rank test]). Among women who never had a CD4 cell count of <200 cells/μL, HCV‐positive women (regardless of HCV RNA status) were more likely to develop AIDS than were HCV‐negative women (Figure 3C), with rates at 1, 3, and 5 years after study entry of 13% vs 7%, 26% vs 16%, and 33% vs 21%, respectively (p<.001).
After adjusting for age, race, smoking, and ART, we found HCV status, injection drug use, CD4 cell count, and HIV plasma RNA level to be independent risk factors for AIDS‐defining conditions in the Cox model (Table 2). Compared with women who never had a CD4 cell count of <200 cells/μL, women with a current and previous CD4 cell count of <200 cells/μL had a 3‐fold increased risk of AIDS and AIDS‐related death (HR, 3.48 [95% CI, 2.77–4.36]). This was confirmed in a separate model that assessed visit‐specific CD4 cell counts of <200 vs >500 cells/μL (HR, 3.00 [95% CI, 2.26–4.00]; data not shown). Alcohol use, prophylactic antibiotic use, and aspartate to platelet ratio index were not statistically significant predictors of AIDS, and their inclusion in multivariate models did not alter HR estimates for injection drug use, HCV status, CD4 cell count, and HIV RNA levels. Among ART‐naive women, HCV‐positive viremic women had a 2‐fold higher risk of AIDS compared with HCV‐negative women (data not shown).
Association between level of immune activation and HCV status.
HCV status was statistically significantly correlated with CD8+CD38+DR+ and CD4+CD38+DR+ T cell levels in univariate analyses (Table 3). In adjusted generalized estimating equation models, percentage of CD8+CD38+DR+ T cells was statistically significantly positively associated with HCV status (p=.04). Other independent correlates of CD8 activation included HIV RNA level and ART. For CD4+CD38+DR+ T cells, there was no statistically significant positive trend overall by HCV status. However, after the HCV‐negative group was removed from the analysis, the trend was statistically significant among HCV‐positive women (p=.02).
Immune activation and risk of AIDS.
Among the 592 women with immune activation data, AIDS risk was statistically significantly increased among women in the highest tertile of CD8+CD38+DR+ T cells compared with women in the lowest tertile of CD8+CD38+DR+ T cells, and among women in the highest tertile of CD4+CD38+DR+ T cells compared with women in the lowest tertile of CD4+CD38+DR+ T cells (Table 4). In contrast, higher percentages of CD8+CD38−DR−, CD8+CD38−DR+, and CD4+CD38−DR− T cells were statistically significantly protective against AIDS. When we adjusted for HIV RNA level, these associations remained unchanged. However, after adjusting for CD4 cell count or CD4 cell count and HIV RNA level, HRs remained statistically significant only for CD8+CD38−DR+ and CD4+CD38+DR+ T cells. Of note, HRs for each HCV RNA level were not statistically significant in any immune marker models: in model 1 for CD8+CD38+DR+ T cells, the HR was 0.94 (95% CI, 0.48–1.82) for HCV‐positive nonviremic women and 0.88 (95% CI, 0.45–1.73), 1.67 (95% CI, 0.62–2.20), 1.14 (95% CI, 0.61–2.17), and 1.14 (95% CI, 0.60–2.17) for HCV‐positive viremic women with RNA levels of 983,000, 983,001–2,395,000, 2,395,001–3,980,000, and >3,980,001 IU/mL, respectively.
Immune activation and risk of AIDS in HCV‐negative and HCV‐positive viremic women.
Stratified analyses showed that among HCV‐positive viremic women (n=278), AIDS risk was statistically significantly increased with higher percentages of CD8+CD38+DR+ and CD4+CD38+DR+ T cells (Table 4). However, for HCV‐negative women, percentage of CD8+CD38+DR+ T cells was not statistically significantly associated with AIDS. Conversely, higher percentages of CD4+CD38−DR−, CD8+CD38−DR−, and CD8+CD38−DR+ T cells were associated with decreased AIDS risk for both groups. After additional adjustments for HIV RNA level, CD4 cell count, or both, risk was altered but remained statistically significant for CD8+CD38−DR+ and CD4+CD38+DR+ T cells and was borderline statistically significant for CD8+CD38+DR+ T cells only among HCV‐positive viremic women. For HCV‐negative women (n=242), HRs remained statistically significant only for CD8+CD38−DR+ and CD4+CD38+DR+ T cells after adjusting for HIV RNA level (Table 4). HRs were not statistically significantly different between HCV‐positive viremic women and HCV‐negative women (p>.50 for all interactions).
Discussion
HIV‐positive patients with chronic active or reactivating viral coinfections (eg, cytomegalovirus or herpes simplex virus coinfections) have higher plasma HIV RNA levels, lower T cell counts, and greater progression to AIDS compared with HIV‐positive patients without evidence of infection/reactivation [31, 32]. For HCV coinfection, however, there have been conflicting reports [10–19]. Consequently, our findings from this large cohort study, which included 1307 women, are notable. First, women with high baseline HCV RNA levels have an increased risk of AIDS, independent of CD4 cell count and HIV RNA level. Second, there was an almost 2‐fold increased probability of developing AIDS for HCV‐positive women compared with HCV‐negative women who never had a CD4 cell count of <200 cells/μL and for women who remained ART naive. Third, HCV coinfection was associated with increased CD8 activation. Finally, our most important finding was the statistically significant association between the level of activated CD8 T cells and incident AIDS among HCV‐positive viremic women. HCV‐positive viremic women with >43% activated CD8 T cells had an almost 3‐fold increased risk of AIDS‐defining conditions and/or AIDS‐related deaths compared with HCV‐positive viremic women with <26% activated CD8 T cells. This was not found for HCV‐negative women. In contrast, high levels of CD4 activation similarly predicted AIDS in both groups of women. These data suggest that the increased risk of HIV disease progression among HCV‐coinfected women with high levels of CD8 activation may be due to immune dysfunction. Importantly, we also showed that women with high percentages of CD8+CD38−DR+ and CD4+CD38−DR− or CD8+CD38−DR− T cells had a 50%–70% decreased AIDS risk, which suggests better immunity among this group of women.
To our knowledge, the Swiss HIV Cohort Study [17] was the first large study to demonstrate that HCV accelerated HIV disease independent of injection drug use. Other studies found no effect of HCV on HIV disease progression, although recent studies have reported increased risk [9–19]. Our study, in which only 10%–20% of the participants were active injection drug users during follow‐up, demonstrates an increased risk of an AIDS‐defining condition with increasing HCV RNA level. Furthermore, our study assessed outcome from the time of study entry to the time of an AIDS‐defining condition adjusting for ART in time‐dependent Cox models, whereas some studies limited outcome from initiation of highly active ART or excluded women with CD4 cell counts of <200 cells/μL at baseline, neither of which was done in our study. Although the effect of HCV genotype on immune activation is unknown, most women in our study were infected with genotype 1, which is associated with higher HCV RNA levels [33]. In our study, higher HCV RNA levels correlate with higher levels of immune activation. Differences in genotype or in rates of active injection drug use may explain differences between the results of our study and those in previous reports [19].
Immune activation has been closely linked to HIV disease progression [1, 4, 5, 34–36], but to our knowledge this association has not previously been reported in the setting of HCV coinfection. Our finding of increased incidence of AIDS‐defining conditions in relation to high levels of immune activation suggests that there is impaired T cell function in HCV‐positive viremic women that may potentially put them at higher risk of HIV disease progression compared with HCV‐negative women.
There are a number of factors that could potentially influence immune activation and in turn pathogenesis of HIV disease, including age, race, gender, injection drugs, use of highly active ART and antibiotic prophylaxis, smoking, alcohol, HCV genotype, and extent of liver damage. We evaluated for each of these in univariate models and then in multivariate models when appropriate.
In vitro studies have shown that CD8 T cells have a lower threshold for activation and proliferation compared with CD4 T cells [37]. Ongoing antigen‐driven activation of CD8 T cells ultimately leads to CD8 T cell exhaustion and replicative senescence, which lead to inability to fight opportunistic pathogens [4]. The factors that influence T cell activation among the women included in our study are most likely multifactorial and may be a direct consequence of activation in the liver or may be related to extrahepatic replication of HCV [38]. Alternatively, host‐specific factors (eg, cytokines) may drive persistent T cell activation. Furthermore, factors that drive immune activation may increase the available targets for further viral replication. Finally, HCV infection may impair T cell maturation more globally to a more immature primed activated phenotype and also may impair responses to Toll‐like receptors, suggesting that both the innate and adaptive arms are affected [24, 39].
Our study systematically evaluated the association between HCV viremia, immune activation, and AIDS outcome. We determined that (1) HCV viremia is associated with AIDS outcome, independent of injection drug use, HIV RNA level, CD4 cell count, and ART (Table 2); (2) HCV viremia is associated with CD4 and CD8 activation, independent of HIV RNA level (Table 3); and (3) high levels of CD8 activation are associated with AIDS in HCV‐positive viremic women but not in HCV‐negative women. Our multivariate models showed that the causal pathway between T cell activation and HIV disease progression cannot be completely explained by HIV or HCV viral load, and other mediators of CD8 activation may be involved in increasing AIDS risk. This may be because substantial immune activation occurs in tissues such as the liver, and viral load may not reflect the extent of the activation. For instance, recently there has been evidence that the gastrointestinal tract is a site for activation of T cells as a result of microbial translocation. Gut‐associated T cell depletion may also have a significant effect on HIV pathogenesis [8, 40–42]. From the intestines, T cells and microbial antigens circulate directly through the liver, where activation may continue. Whether the liver plays a role in amplifying or modulating this activation, especially with prior HCV infection, is unknown, but a recent study found evidence of increased microbial translocation among HCV‐positive individuals with cirrhosis [43]. In our study, liver biopsy data were unavailable. However, we did evaluate for liver disease by use of the aspartate to platelet ratio index [30] and found no statistically significant correlation with AIDS risk. Furthermore, we found no association between alcohol use and AIDS outcome. On the other hand, although at the time of AIDS diagnosis there were no statistically significant differences in individual AIDS‐defining conditions noted between HCV‐negative women and HCV‐positive women, HCV viremic women were more likely to report wasting syndrome, bacterial pneumonia, and encephalopathy at the end of follow‐up. This finding suggests that HCV‐positive viremic women may be at continued risk for certain AIDS‐defining conditions and further supports the importance of treatment in this group. The pathogenesis of these findings may be HCV‐related infection of the central nervous system and/or progressive liver disease including cirrhosis. Bacterial pneumonia is increased among HIV‐infected individuals, especially injection drug users [44, 45], and cirrhosis may play a role in some who are coinfected with HCV. However, continued immune activation is also associated with encephalopathy, and some studies have suggested that microbial translocation related to gut‐associated immunodeficiency may be a contributing factor [43, 46–48]. Furthermore, wasting syndrome may be a manifestation of chronic and severe gut‐associated immunodeficiency that may be exacerbated by progressive HCV disease and/or alcohol use.
Our study results confirm those of previous studies that the presence of HLA‐DR on CD8 T cells without CD38 expression appears to be protective [36, 49]. This is consistent with reports showing that elite controllers have higher percentages of HIV‐specific and global CD8+CD38−DR+ T cells [49]. CD8+CD38−DR+ T cells appear to have high proliferative capacity and cytotoxic activity upon antigenic stimulation. Our study results suggest further research is needed to better understand the path of CD8 activation, especially the protective effect of HLA‐DR expression.
Although our study is unique, it has limitations. We did not have information on the timing of HIV or HCV infection. Furthermore, HCV‐positive women and HCV‐negative women may be different because of differing routes of HIV infection (injection drug use vs sexual). Immune activation markers were measured for only a subset of the study population [7, 24, 25], and not all phenotypic markers were measured at the same time. Nevertheless, our results confirmed previous observations by other investigators [1, 6, 36]. Finally, we evaluated HCV RNA levels only at baseline because not all women underwent multiple measures. We assumed that HCV RNA levels would not change substantially in women who were not treated for HCV infection, on the basis of published studies that found that even with initiation and discontinuation of highly active ART there is only a 0.43–0.59 log change in HCV viral load [50]; such small changes would not affect our findings.
In conclusion, our study demonstrates that HIV‐coinfected HCV‐positive viremic women are at increased risk for AIDS‐defining conditions compared with HCV‐negative women, possibly because of high levels of activation of T cells, especially CD8 T cells, which indicates increased immune dysregulation in this population of women. Lower levels of activation of both CD8 and CD4 T cells and activation of CD8 T cells expressing only HLA‐DR is protective against AIDS. Further study is needed to understand better the pathogenesis of T cell activation, especially of CD8 T cells in relation to HIV disease. HCV‐positive viremic women may benefit from treatment of HIV and HCV infection to prevent significant immunologic changes and improve long‐term outcome. Assessing CD4 and CD8 T cell activation could help clinicians evaluate their patients’ risk of developing AIDS.
Acknowledgment
We thank the participants of this study. Data in this manuscript were collected by the Women's Interagency HIV Study (WIHS) Collaborative Study Group, with centers (Principal Investigators) located at New York City/Bronx Consortium (Kathryn Anastos); Brooklyn, NY (Howard Minkoff); Washington DC Metropolitan Consortium (Mary Young); The Connie Wofsy Study Consortium of Northern California (Ruth Greenblatt); Los Angeles County/Southern California Consortium (Alexandra Levine); Chicago Consortium (Mardge Cohen); and Data Analysis Center (Stephen Gange). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health.
HCV Therapy Response Predicts Outcome in Co-Infected Patients
CROI: HCV Therapy Response Predicts Outcome in Co-Infected Patients
By Michael Smith, North American Correspondent, MedPage Today
Published: February 21, 2010
Reviewed by Barry S. Zingman, MD; Professor of Clinical Medicine, Albert Einstein College of Medicine, Bronx, NY and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner Earn CME/CE credit
for reading medical news
Action Points
* Explain to interested patients that HIV and hepatitis C co-infection is common.
* Note that this study showed that failure to respond to hepatitis C treatment increases the risk of HIV progression and mortality, separately from increased risk of liver-related complications.
* Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered preliminary until published in a peer-reviewed journal.
SAN FRANCISCO -- For people with both HIV and Hepatitis C, a poor response to hepatitis therapy markedly increased the risk of HIV progression and death, a researcher said here.
Previous research had shown that such patients were at increased risk of liver-related complications and death, according to Juan Berenguer, MD, of the Gregorio Marañon University Hospital in Madrid.
But analysis of outcomes for more than 1,400 co-infected patients at 20 clinical centers in Spain showed the same is true for outcomes not related to the liver disease, Berenguer told reporters at the Conference on Retroviruses and Opportunistic Infections.
In those who did not respond to therapy, he said, the risk of AIDS-defining conditions and non-liver death was significantly higher -- even though all patients in the study were on anti-HIV therapy and had fully suppressed virus.
Many studies have looked at the risks and benefits of various treatments, he said, but there is little data on long-term outcomes for people with both diseases.
To tease out some answers, he and colleagues looked at a large cohort of 1,428 patients treated with interferon and ribavirin between January, 2000 and July, 2007, Berenguer said. For this analysis, the researchers compared outcomes for those who did or did not achieve a so-called "sustained virological response."
A sustained virological response is a standard measure of response, defined as an undetectable serum level of Hepatitis C RNA 24 weeks after the completion of therapy.
Overall, he said, 36% of the patients had a sustained virological response. Compared with them, those who did not respond:
* Had a 3.6-fold greater risk of a new AIDS-defining condition, which was significant at P=0.008
* Had a 3.5-fold greater risk of non-liver-related death (P=0.019)
* Had a 3.3-fold greater risk of both (P=0.001)
After adjustment for covariates such as age, sex, hepatitis C genotype, and prior AIDS-defining illness, the risk of non-liver-related death lost significance, although the hazard ratio remained high at 2.6.
The risks of a new AIDS-defining condition or both AIDS and death remained high and significant, Berenguer said, (HR 3.24 and 2.86, respectively).
All told, he said, there were 24 non-liver-related deaths among the 908 patients who did not achieve a sustained virological response, compared with four among the 520 who did clear hepatitis C. At the same time, 34 of the nonresponders had a new AIDS-defining condition, compared with five of the responders.
The reason for the disparity is unclear, Berenguer said.
It may be that the increased risks are a function of poorer immune response that does not involve control of HIV, he said, since there was no significant difference between responders and nonresponders in suppression of HIV.
It may also be a result of chronic HIV viremia, he said.
The study is part of a range of research aimed at teasing out the natural history and effects of hepatitis C, according to David Thomas, MD, of Johns Hopkins University, who moderated a press conference at which the study was presented.
"Some people can recover from hepatitis C all by themselves," he said. "They just clear it out of the body and it's gone." Meanwhile, others respond to treatment, but many do neither, he said, although it has not been clear why not.
Thomas noted that HIV and hepatitis C are among the most prominent co-infections in the world. Berenguer's research outlines the risks for those co-infected patients who do not respond to hepatitis C treatment, he said.
The study was supported by the Fundación para la Investigación y la Prevención del SIDA en España.
Berenguer reported financial links with Roche and Schering-Plough.
Primary source: Conference on Retroviruses and Opportunistic Infections
Source reference:
Berenguer J, et al "Sustained virological response to interferon plus ribavirin reduces HIV progression and non-liver-related mortality in patients co-infected with HIV and HCV" CROI 2010; Abstract 167.
By Michael Smith, North American Correspondent, MedPage Today
Published: February 21, 2010
Reviewed by Barry S. Zingman, MD; Professor of Clinical Medicine, Albert Einstein College of Medicine, Bronx, NY and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner Earn CME/CE credit
for reading medical news
Action Points
* Explain to interested patients that HIV and hepatitis C co-infection is common.
* Note that this study showed that failure to respond to hepatitis C treatment increases the risk of HIV progression and mortality, separately from increased risk of liver-related complications.
* Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered preliminary until published in a peer-reviewed journal.
SAN FRANCISCO -- For people with both HIV and Hepatitis C, a poor response to hepatitis therapy markedly increased the risk of HIV progression and death, a researcher said here.
Previous research had shown that such patients were at increased risk of liver-related complications and death, according to Juan Berenguer, MD, of the Gregorio Marañon University Hospital in Madrid.
But analysis of outcomes for more than 1,400 co-infected patients at 20 clinical centers in Spain showed the same is true for outcomes not related to the liver disease, Berenguer told reporters at the Conference on Retroviruses and Opportunistic Infections.
In those who did not respond to therapy, he said, the risk of AIDS-defining conditions and non-liver death was significantly higher -- even though all patients in the study were on anti-HIV therapy and had fully suppressed virus.
Many studies have looked at the risks and benefits of various treatments, he said, but there is little data on long-term outcomes for people with both diseases.
To tease out some answers, he and colleagues looked at a large cohort of 1,428 patients treated with interferon and ribavirin between January, 2000 and July, 2007, Berenguer said. For this analysis, the researchers compared outcomes for those who did or did not achieve a so-called "sustained virological response."
A sustained virological response is a standard measure of response, defined as an undetectable serum level of Hepatitis C RNA 24 weeks after the completion of therapy.
Overall, he said, 36% of the patients had a sustained virological response. Compared with them, those who did not respond:
* Had a 3.6-fold greater risk of a new AIDS-defining condition, which was significant at P=0.008
* Had a 3.5-fold greater risk of non-liver-related death (P=0.019)
* Had a 3.3-fold greater risk of both (P=0.001)
After adjustment for covariates such as age, sex, hepatitis C genotype, and prior AIDS-defining illness, the risk of non-liver-related death lost significance, although the hazard ratio remained high at 2.6.
The risks of a new AIDS-defining condition or both AIDS and death remained high and significant, Berenguer said, (HR 3.24 and 2.86, respectively).
All told, he said, there were 24 non-liver-related deaths among the 908 patients who did not achieve a sustained virological response, compared with four among the 520 who did clear hepatitis C. At the same time, 34 of the nonresponders had a new AIDS-defining condition, compared with five of the responders.
The reason for the disparity is unclear, Berenguer said.
It may be that the increased risks are a function of poorer immune response that does not involve control of HIV, he said, since there was no significant difference between responders and nonresponders in suppression of HIV.
It may also be a result of chronic HIV viremia, he said.
The study is part of a range of research aimed at teasing out the natural history and effects of hepatitis C, according to David Thomas, MD, of Johns Hopkins University, who moderated a press conference at which the study was presented.
"Some people can recover from hepatitis C all by themselves," he said. "They just clear it out of the body and it's gone." Meanwhile, others respond to treatment, but many do neither, he said, although it has not been clear why not.
Thomas noted that HIV and hepatitis C are among the most prominent co-infections in the world. Berenguer's research outlines the risks for those co-infected patients who do not respond to hepatitis C treatment, he said.
The study was supported by the Fundación para la Investigación y la Prevención del SIDA en España.
Berenguer reported financial links with Roche and Schering-Plough.
Primary source: Conference on Retroviruses and Opportunistic Infections
Source reference:
Berenguer J, et al "Sustained virological response to interferon plus ribavirin reduces HIV progression and non-liver-related mortality in patients co-infected with HIV and HCV" CROI 2010; Abstract 167.
Supported in part by an educational grant from Bristol-Myers Squibb. Supported in part by an educational grant from Bristol-Myers Squibb. CROI: HCV
Supported in part by an educational grant from Bristol-Myers Squibb.
Supported in part by an educational grant from Bristol-Myers Squibb.
CROI: HCV Spread Abetted by Needle Type
By Crystal Phend, Senior Staff Writer, MedPage Today
Published: February 20, 2010
Reviewed by Barry S. Zingman, MD; Professor of Clinical Medicine, Albert Einstein College of Medicine, Bronx, NY and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner Earn CME/CE credit
for reading medical news
Action Points
* Explain to interested patients that hepatitis C virus remains viable longer in high-volume syringes and at lower temperatures.
* Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered preliminary until published in a peer-reviewed journal.
SAN FRANCISCO -- Among injection drug users, the type of needle used and the temperature it's stored at can substantially affect the risk of transmitting hepatitis C virus (HCV), researchers found.
Syringes with detachable needles appeared by far the most likely to transmit the virus, Elijah Paintsil, MD, of Yale, and colleagues showed in a laboratory study.
And lower temperatures kept HCV viable for up to 63 days in the syringes with a high void volume, they reported here at the Conference on Retroviruses and Opportunistic Infections.
The bottom line is that sharing needles is a bad idea no matter what the conditions, although there may be implications for prevention, Paintsil said at a press conference.
Needle sharing programs typically offer users whatever kind they want, noted co-author Robert Heimer, PhD, also of Yale.
But changing that to offer only types less associated with transmission may help cut down on what has become an epidemic among injection drug users, he said.
These kind of programs aimed at harm reduction have been much more effective in reducing incidence of HIV, which is 10-fold less transmissible than HCV.
By comparison, HCV is a hardy virus -- a grenade to HIV's firecracker of transmissibility, said David Thomas, MD, of Johns Hopkins, moderator of the press conference at which the results were presented.
The researchers investigated why by loading a variety of syringes with HCV-spiked blood and then storing them at different temperatures.
After a delay of up to 63 days, they recovered the virus and tested its infectivity in cell cultures.
At room temperature (22°C, or 72°F), HCV dropped off sharply in activity over the first few hours but then decayed slowly over the next three days.
Whereas the low, 2-μL volume syringe of the sort usually used for insulin administration maintained viable HVC out to three days at room temperature, it extended to seven days at 4ºC (39°F).
For a high, 32-μL volume syringe with detachable needle, some degree of viability was maintained at all temperatures out to 63 days, although again low temperatures maintained greater viability.
Most needles used by injection drug users stay in circulation up to 23 days, a period during which the virus remained at high viral titers, Paintsil said.
The researchers cautioned that this simulation in the laboratory under carefully controlled conditions might not accurately replicate what would happen among intravenous drug users.
It's also possible that other genotypes or strains of the virus would have different survival characteristics.
While these findings suggest increased transmissibility, effects on population level transmission now need to be determined by epidemiologic studies, Paintsil said.
"This is just the first step," but one that may help inform prevention efforts, Thomas concluded at the press conference.
The study was funded by grants from the Yale Center for Interdisciplinary Research on AIDS and National Institute on Drug Abuse.
Paintsil and Thomas reported no conflicts of interest. Heimer provided no information on conflicts of interest.
Primary source: Conference on Retroviruses and Opportunistic Infections
Source reference:
Paintsil E, et al "Survival of HCV in syringes: Implication for HCV transmission among injection drug users" CROI 2010; Abstract 168.
Supported in part by an educational grant from Bristol-Myers Squibb.
CROI: HCV Spread Abetted by Needle Type
By Crystal Phend, Senior Staff Writer, MedPage Today
Published: February 20, 2010
Reviewed by Barry S. Zingman, MD; Professor of Clinical Medicine, Albert Einstein College of Medicine, Bronx, NY and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner Earn CME/CE credit
for reading medical news
Action Points
* Explain to interested patients that hepatitis C virus remains viable longer in high-volume syringes and at lower temperatures.
* Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered preliminary until published in a peer-reviewed journal.
SAN FRANCISCO -- Among injection drug users, the type of needle used and the temperature it's stored at can substantially affect the risk of transmitting hepatitis C virus (HCV), researchers found.
Syringes with detachable needles appeared by far the most likely to transmit the virus, Elijah Paintsil, MD, of Yale, and colleagues showed in a laboratory study.
And lower temperatures kept HCV viable for up to 63 days in the syringes with a high void volume, they reported here at the Conference on Retroviruses and Opportunistic Infections.
The bottom line is that sharing needles is a bad idea no matter what the conditions, although there may be implications for prevention, Paintsil said at a press conference.
Needle sharing programs typically offer users whatever kind they want, noted co-author Robert Heimer, PhD, also of Yale.
But changing that to offer only types less associated with transmission may help cut down on what has become an epidemic among injection drug users, he said.
These kind of programs aimed at harm reduction have been much more effective in reducing incidence of HIV, which is 10-fold less transmissible than HCV.
By comparison, HCV is a hardy virus -- a grenade to HIV's firecracker of transmissibility, said David Thomas, MD, of Johns Hopkins, moderator of the press conference at which the results were presented.
The researchers investigated why by loading a variety of syringes with HCV-spiked blood and then storing them at different temperatures.
After a delay of up to 63 days, they recovered the virus and tested its infectivity in cell cultures.
At room temperature (22°C, or 72°F), HCV dropped off sharply in activity over the first few hours but then decayed slowly over the next three days.
Whereas the low, 2-μL volume syringe of the sort usually used for insulin administration maintained viable HVC out to three days at room temperature, it extended to seven days at 4ºC (39°F).
For a high, 32-μL volume syringe with detachable needle, some degree of viability was maintained at all temperatures out to 63 days, although again low temperatures maintained greater viability.
Most needles used by injection drug users stay in circulation up to 23 days, a period during which the virus remained at high viral titers, Paintsil said.
The researchers cautioned that this simulation in the laboratory under carefully controlled conditions might not accurately replicate what would happen among intravenous drug users.
It's also possible that other genotypes or strains of the virus would have different survival characteristics.
While these findings suggest increased transmissibility, effects on population level transmission now need to be determined by epidemiologic studies, Paintsil said.
"This is just the first step," but one that may help inform prevention efforts, Thomas concluded at the press conference.
The study was funded by grants from the Yale Center for Interdisciplinary Research on AIDS and National Institute on Drug Abuse.
Paintsil and Thomas reported no conflicts of interest. Heimer provided no information on conflicts of interest.
Primary source: Conference on Retroviruses and Opportunistic Infections
Source reference:
Paintsil E, et al "Survival of HCV in syringes: Implication for HCV transmission among injection drug users" CROI 2010; Abstract 168.
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