Due
to overlapping risk factors, many individuals are infected with more than one
form of viral hepatitis. The hepatitis B and
C viruses (HBV and HCV) are transmitted by blood
- and less commonly by sexual activity - while the hepatitis A virus (HAV) is
transmitted through contaminated water and food. Hepatitis delta virus (HDV) is
a defective virus that can only replicate in conjunction with HBV.
Belgian
researchers presented an overview of coinfection with multiple hepatitis viruses
in the December 2006 European Journal of Gastroenterology and Hepatology.
"Coinfection
with other hepatitis viruses modifies the viral profile in serum and leads to
more liver damage and more rapid progression during the course of hepatitis C
virus infection," the authors wrote.
The
combined effects of coinfection with more that one hepatitis virus is due not
only to virus-virus or virus-cell interactions, but is also attributable to enhanced
immune response, which is responsible for much of the liver damage associated
with viral hepatitis.
"A
super-infecting viral infection does not cross-activate protective immune responses
to the pre-existing virus, albeit the latter can become undetectable," the
researchers wrote. "The induced cytokine stimulation might enhance the hepatic
inflammation."
Moreover,
they added, "hepatitis B virus coinfection increases the risk of development
of hepatocellular carcinoma in hepatitis C virus patients through common necro-inflammatory
pathways or by direct oncogenic activity of hepatitis B virus."
Viral
interactions can also complicate the management of patients with hepatitis coinfections,
since HCV infection impairs the body's humoral response to the HAV and HBV vaccines,
and because treatment that suppresses HCV "endangers dually infected patients
with reactivation of coinfected hepatitis B virus."
Therefore,
the authors concluded, "Optimized strategies and follow-up are thus necessary
in the treatment of infection with multiple viruses." It seems necessary,
they advised, to look for markers of HBV and HDV infection in chronic hepatitis
patients who test positive for HCV antibodies but negative for HCV RNA. Likewise,
it is important to test for HCV RNA in patients who are HBsAg-negative/anti-HBc-positive
(that is, they have undetectable HBV surface antigen but detectable HBV core antibodies)
with a low level of HBV DNA.
Department
of Hepatology, University Hospital Gasthuisberg, Laboratory of Clinical &
Epidemiological Virology, Department of Microbiology and Immunology, Rega Institute
for Medical Research, Catholic University of Leuven, Leuven, Belgium.
1/16/07
Reference L
Lin, C Verslype, J F van Pelt, and others. Viral interaction and clinical implications
of coinfection of hepatitis C virus with other hepatitis viruses. European
Journal of Gastroenterology and Hepatology 18(12): 1311-1319. December 2006.
