seventy percent of people who contract Hepatitis C will live with the virus

September 17, 2009
www.medicalnewstoday.com

More than seventy percent of people
who contract Hepatitis C will live with
the virus that causes it for the rest of their
lives and some will develop serious liver
disease including cancer. However, 30
to 40 percent of those infected somehow
defeat the infection and get rid of the
virus with no treatment. In this week’s
Advanced Online Publication at Nature,
Johns Hopkins researchers working as
part of an international team report the
discovery of the strongest genetic alteration
associated with the ability to get
rid of the infection.
“If we knew why some people got rid
of the disease on their own, then maybe
we could figure out ways to help other
people who didn’t,” says David Thomas,
M.D., professor of medicine and director
of infectious diseases at Johns
Hopkins. “Or maybe even help prevent
infections entirely.”
A previous study led by David
Goldstein at Duke University had found
a variation in a single chemical of DNA,
known as a single-nucleotide polymorphism,
or SNP, near the IL28B gene,
which while poorly understood, is
thought to help the immune response to
Hepatitis C viral infection. People infected
with Hepatitis C, who carried the
C/C variation SNP near their IL28B
Genetic Hint for Ridding the Body of Hepatitis C
gene, were found more likely to respond
to hepatitis C treatment, which can rid
some patients of the virus.
So the Hopkins-and-National-Institutes-
of-Health-led team wondered if the
C/C variation as opposed to the C/T or
T/T alternatives also played a role in
some peoples’ ability to get rid of the
virus without the help of medication. To
do this, they assembled information from
six different studies that had over many
years collected DNA and Hepatitis C
infection information from people all
over the world. The team then analyzed
DNA at the IL28B gene from a total of
1008 patients: 620 persistently infected
and 388 who had been infected but no
longer carried any virus. DNA analysis
revealed that of the 388 patients who no
longer carried virus, 264 have the C/C
variation.
“This is the strongest clue to date to
understanding what would constitute a
successful immune response,” says Thomas.
“We don’t yet know the significance
of this C variant, but we know we
need to do more work to find out what it
means and whether it might be helpful
to halting the disease.”
In addition to confirming that the C/
C variant correlates with the ability to
get rid of the virus once infected, the
researchers also noticed an intriguing
trend: the C/C variant does not appear
equally in all populations.
To investigate further, they analyzed
DNA from more than 2300 people
worldwide in order to further examine
distribution of the C/C variant in different
populations. Of the 428 samples from
Africa, only 148 carried the C/C genotype.
In contrast, of the European
samples 520 out of 761 carried the C/C
variant. The most striking were the DNA
samples from Asia, where 738 of 824
samples carried C/C.
“We wonder if this SNP also explains
some of the genetic basis for the population
difference of Hepatitis C clearance,”
says Chloe Thio, M.D., associate
professor of medicine. “It’s been reported
that African-Americans are less
likely to clear the disease than Caucasians.”
The team plans to pursue this research
further to better understand why some
populations become chronically infected.
Says Thio, “This is an exciting
step towards better understanding of
what the immune response is against the
virus so we can improve our therapies.”
This study was principally funded by
the National Institutes of Drug Abuse
and the National Cancer Institute of the
National Institutes of Health.
Source: Johns Hopkins Medicine