Interferon-gamma-associated responses to woodchuck hepatitis virus infection in neonatal woodchucks and virus-infected hepatocytes.

Acute hepatitis and recovery from woodchuck hepatitis virus (WHV) infection involves increased intrahepatic expression of interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) mRNAs. In the present study, recovery correlated with increased intrahepatic expression of mRNAs for major histocompatibility complex class 1 (MHC1), beta(2)-microglobulin, 2'5'-oligoadenylate synthetase (2'5'-OAS), and indoleamine dioxygenase (IDO). By comparison, acute WHV infection progressing to chronicity was associated with diminished expression of these IFN-gamma-associated mRNAs in liver. Transfection of WHV-infected primary hepatocytes (WPH) from WHV carriers with an IFN-gamma-expressing plasmid (pIFN-gamma) resulted in dose-dependent accumulations of MHC1, TNF-alpha, 2'5'-OAS, and IDO mRNAs within 96 h. Markers of T cells and immune-mediated cytotoxicity that accumulate in recovering liver were not apparent in WPH based on the relative lack of CD3, CD4, Fas ligand, perforin, and granzyme B mRNAs. Expression of pIFN-gamma, and TNF-alpha-expressing plasmid (pTNF-alpha), did not affect total WHV RNA, or fully double-stranded WHV DNA in WPH, but each reduced some of the replicative intermediate (RI) species of WHV DNA synthesis. WPH treated with recombinant IFN-alpha protein had a higher fold induction of 2'5'-OAS mRNA associated with partial reductions in WHV RNAs and the major RI species. Thus, IFN-gamma expression in carrier WPH induced several host responses often observed in liver of recovering woodchucks, and impaired a stage of WHV DNA synthesis by a non-cytolytic mechanism mediated by TNF-alpha. Local enhancement of IFN-gamma-associated responses in chronic WHV-infected hepatocytes may promote therapeutic antiviral effects, but additional effector mechanisms evident during recovery appear necessary for more complete clearance of WHV infection.

Antiviral activities of oral 1-O-hexadecylpropanediol-3-phosphoacyclovir and acyclovir in woodchucks with chronic woodchuck hepatitis virus infection.

Acyclovir triphosphate is a potent inhibitor of hepatitis B virus DNA polymerase, but acyclovir treatment provides no benefit in patients with hepatitis B virus infection. This is due in part to the fact that hepatitis B virus, unlike herpes simplex virus, does not code for a viral thymidine kinase which catalyzes the initial phosphorylation of acyclovir. We synthesized 1-O-octadecyl-sn-glycero-3-phospho (3-P)-acyclovir and found that it was highly active in reducing hepatitis B virus replication in 2.2. 15 cells, while acyclovir was inactive. The greater antiviral activity of 1-O-octadecyl-sn-glycero-3-P-acyclovir appeared to be due to liver cell metabolism of the compound to acyclovir monophosphate (K. Y. Hostetler et al., Biochem. Pharmacol. 53:1815-1822, 1997). However, a closely related compound without a hydroxyl group at the sn-2 position of glycerol, 1-O-hexadecylpropanediol-3-P-acyclovir, was more active and selective in 2.2.15 cells in vitro. In this study, we treated woodchucks chronically infected with woodchuck hepatitis virus with increasing oral doses of 1-O-hexadecylpropanediol-3-P-acyclovir and assessed the response to therapy versus acyclovir or a placebo. At a dosage of 10 mg/kg of body weight twice a day, the test compound significantly inhibited viral replication in vivo, as indicated by a 95% reduction in serum woodchuck hepatitis virus DNA levels and by a 54% reduction in levels of woodchuck hepatitis virus replicative intermediates in the liver. Higher doses were somewhat less effective. In contrast, 20 mg of acyclovir/kg twice daily, a 5. 3-fold-higher molar dosage, had no demonstrable activity against woodchuck hepatitis virus. Oral 1-O-hexadecylpropanediol-3-P-acyclovir appeared to be safe and effective in chronic woodchuck hepatitis virus infection.