Interferon-alpha (IFN-alpha) is a potent suppressor of hepatitis B virus (HBV) replication in the HBV-transgenic mouse, depleting virus replication intermediates from infected hepatocytes via pathways mediated by
interferon-gamma (IFN-gamma) and
tumor necrosis factor alpha (
TNF-alpha). It has also been hypothesized that
cytokines induce curing of infected hepatocytes via non-cytolytic pathways during resolution of transient hepadnavirus
infections. We have therefore evaluated
therapy of chronic woodchuck hepatitis virus (WHV)
infections using treatment with the
nucleoside analog clevudine [
L-FMAU; 1-(2-fluoro-5-methyl-b-L-arabinofuranosyl)
uracil] and
therapy with adenovirus vectors expressing INF-gamma,
TNF-alpha, and
beta-galactosidase. Before their use in vivo, expression of IFN-gamma and
TNF-alpha from the adenovirus vectors was evaluated in vitro.
Conditioned media from adenovirus-infected WC-3 cells was shown to inhibit WHV replication in baculovirus-transduced cells. Adenovirus super-
infection of the liver in woodchucks led to declines in the percentage of hepatocytes with detectable core
antigen and
nucleic acids, and in levels of covalently closed
circular DNA (cccDNA) and total WHV
DNA, but a major long-term benefit of adenovirus super-
infection during
clevudine treatment was not demonstrated. Moreover, the effect took at least 2 weeks to develop suggesting that the declines in the percentage of WHV-infected cells, ccc, and total WHV
DNA resulted from induction of the adaptive immune response by the adenovirus super-
infection, and only indirectly from the expression of
cytokines by the vectors.