People
Re-infected with Hepatitis C Are More Likely to Spontaneously
Clear Virus, Indicating Partial Immunity
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| SUMMARY:
Individuals who experience spontaneous clearance of
an initial hepatitis C virus (HCV) infection are more
likely to clear the virus again without treatment if
they become re-infected. This finding, reported in the
January
2010 issue of Gastroenterology, demonstrates
that the immune system can develop some degree of natural
immunity against HCV, but protection is not complete.
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By
Liz Highleyman
Unlike
diseases that are only contracted once because the body develops
protective immunity, HCV infection
can occur again after spontaneous clearance or successful treatment.
It is not certain, however, how often this occurs or whether the
immune system provides some level of protection against re-infection.
William
Osburn from Johns Hopkins and colleagues followed a group of active
injection drug users (IDUs) -- a group with ongoing exposure to
HCV -- who had spontaneously controlled an initial infection to
determine whether primary control conferred protection against
future chronic infection (persisting more than 6 months).
The study included 22 active IDUs who had cleared a primary HCV
infection for at least 60 days. Participants were monitored monthly
to check for re-infection, defined as the detection of a new HCV
infection.
Immune protection was assessed based on the magnitude and duration
of viremia (detectable virus in the blood) following re-infection
and generation of T-cell and neutralizing antibody responses.
Results
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HCV
re-infection occurred in 11 IDUs -- or 50% of study participants
-- who previously spontaneously controlled primary HCV infection.
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83%
of re-infected patients demonstrated spontaneous viral clearance
the second time -- much higher that the approximately 25%
of people who naturally clear an initial infection. |
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The
duration and maximum level of viremia during subsequent episodes
of re-infection were significantly lower than those seen during
initial infection in the same individuals. |
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In
contrast to chronic infection, HCV re-infection was associated
with a significant increase in the breadth of T-cell responses. |
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Neutralizing
antibodies against HCV "pseudoparticles" were detected
in 60% of re-infected participants during acute infection;
in contrast, cross-reactive neutralizing antibodies are rarely
detected in people who progress to chronic infection. |
Based on these results, the investigators concluded, "HCV
re-infection is associated with a reduction in the magnitude and
duration of viremia (compared with the initial infection), broadened
cellular immune responses, and generation of cross-reactive humoral
responses."
"These findings are consistent with development of adaptive
immunity that is not sterilizing but protects against chronic
disease," they added.
These results are important because if HCV infection can trigger
production of T-cell and/or neutralizing antibody responses, it
is more likely that an effective vaccine could be developed.
Department of Medicine & Department of Oncology, Johns
Hopkins Medical Institutions, Baltimore, MD; Department of Infectious
Diseases, Southwest Hospital, Third Military Medical University,
Chongqing, China.
1/26/10
Reference
WO
Osburn, BE Fisher, KA Dowd, and others. Spontaneous Control of
Primary Hepatitis C Virus Infection and Immunity against Persistent
Reinfection.
Gastroenterology 138(1): 315-324 (Abstract).
January 2010.
