penciclovir and Hepadnaviridae-Infections

Penciclovir (9-[2-hydroxy-1-(hydroxymethyl)-ethoxymethyl]guanine [PCV]), lamivudine ([-]-beta-L-2',3'-dideoxy-3'-thiacytidine [3TC]), and adefovir (9-[2-phosphonylmethoxyethyl]-adenine [PMEA]) are potent inhibitors of hepatitis B virus (HBV) replication. Lamivudine has recently received approval for clinical use against chronic human HBV infection, and both PCV and PMEA have undergone clinical trials against HBV in their respective prodrug forms (famciclovir and adefovir dipivoxil [bis-(POM)-PMEA]). Since multidrug combinations are likely to be used to control HBV infection, investigation of potential interactions between PCV, 3TC, and PMEA is important. Primary duck hepatocyte cultures which were either acutely or congenitally infected with the duck hepatitis B virus (DHBV) were used to investigate in vitro interactions between PCV, 3TC, and PMEA. Here we show that the anti-DHBV effects of all the combinations containing PCV, 3TC, and PMEA are greater than that of each of the individual components and that their combined activities are approximately additive or synergistic. These results may underestimate the potential in vivo usefulness of PMEA-containing combinations, since there is evidence that PMEA has immunomodulatory activity and, at least in the duck model of chronic HBV infection, is capable of inhibiting DHBV replication in cells other than hepatocytes, the latter being unaffected by treatment with either PCV or 3TC. Further investigation of the antiviral activities of these drug combinations is therefore required, particularly since each of the component drugs is already in clinical use.

Topics: Acyclovir; Adenine; Animals; Antiviral Agents; Cells, Cultured; Drug Interactions; Drug Therapy, Combination; Ducks; Guanine; Hepadnaviridae Infections; Hepatitis B Virus, Duck; Humans; Lamivudine; Liver; Organophosphonates; Virus Replication

Recent studies have implicated bile duct epithelial cells (BDEC) as a reservoir of hepatitis B virus (HBV) infection that may be particularly important in the development of post-liver transplant recurrence of hepatitis B. The aim of this study was to compare the effects of antiviral therapy on duck HBV (DHBV) expression in hepatocytes and BDEC and to determine if this was affected by biliary hyperplasia.. Ducklings congenitally infected with DHBV received penciclovir (10 mg/kg per day) treatment from 9 days of age. In order to mimic the biliary hyperplasia that often accompanies severe post-liver transplant HBV recurrence, half the animals underwent bile duct ligation. Duck HBV-DNA in serum was measured at day 1, and serum and liver DHBV-DNA were determined when the animals were killed on day 17. Intrahepatic expression of viral preS1 antigen and DHBV-DNA was measured by immunohistochemistry and in situ hybridization, respectively.. Viraemia became undetectable in the penciclovir-treated animals at day 17, following 8 days of therapy. Examination of liver tissue revealed that all hepatocytes and the majority of BDEC contained DHBV preS1 antigen and DHBV-DNA. Penciclovir greatly reduced the intrahepatic viral burden, but there was no antiviral effect on viral markers within BDEC. Despite the increased number of BDEC after bile duct ligation, the same proportion of BDEC was seen to be infected, and this was unaffected by antiviral therapy.. In the duck model with and without biliary hyperplasia, penciclovir controls DHBV replication and reduces viral burden in hepatocytes, but not in BDEC. The BDEC appear to be an important reservoir of virus that is relatively unaffected by antiviral treatment, and may play an important role in disease persistence and relapse following cessation of therapy.

Topics: Acyclovir; Animals; Antiviral Agents; Bile Ducts; Cell Division; Disease Models, Animal; DNA, Viral; Ducks; Epithelial Cells; Guanine; Hepadnaviridae Infections; Hepatitis B Surface Antigens; Hepatitis B Virus, Duck; Hyperplasia; In Situ Hybridization; Liver; Protein Precursors; Reverse Transcriptase Inhibitors; Treatment Outcome; Viral Envelope Proteins; Virus Replication

Ducks congenitally infected with duck hepatitis B virus (DHBV) were treated with the antiviral guanine nucleoside analog penciclovir for 12 or 24 weeks at a dosage of 10 mg/kg of body weight per day. By the completion of both 12 and 24 weeks of therapy, molecular hybridization studies of the liver tissue revealed that the viral DNA, RNA, and protein levels were significantly reduced compared to those in the placebo-treated controls. Penciclovir treatment for 12 or 24 weeks was not associated with any toxicity, establishing the efficacy and safety of long-term penciclovir therapy in chronic DHBV infection.

Topics: Acyclovir; Animals; Antiviral Agents; Chronic Disease; DNA, Viral; Ducks; Guanine; Hepadnaviridae Infections; Hepatitis B Virus, Duck; Viral Proteins

Ducks congenitally infected with duck hepatitis B virus (HBV) were treated with the antiviral guanine nucleoside analog penciclovir for 4 weeks at a dose of 10 mg/kg of body weight per day. The effects of treatment on viremia and intrahepatic viral genome replication, transcription, and translation were examined. In seven of eight penciclovir-treated ducks, viremia was barely detectable after a week of treatment. After 4 weeks of treatment, molecular hybridization studies showed that intrahepatic viral DNA, RNA, and protein levels were significantly reduced compared with those in placebo-treated controls. Synthesis of all viral replicative intermediates, including the normally persistent viral supercoiled DNA species, was inhibited by penciclovir treatment. Examination of liver tissue sections after in situ DNA hybridization or immunohistochemical staining confirmed that viral DNA and protein synthesis had been profoundly inhibited in most hepatic parenchymal cells. However, small subpopulations of cells, in particular the small bile duct epithelial cells, remained strongly positive for duck HBV antigens and DNA despite treatment. There was no evidence of toxicity associated with penciclovir therapy. This study confirms the safety and potent antihepadnaviral activity of penciclovir in vivo but indicates that further improvements in antiviral therapy will be required to completely eliminate HBV infection.

Topics: Acyclovir; Animals; Antiviral Agents; Blotting, Southern; DNA, Viral; Ducks; Female; Guanine; Hepadnaviridae Infections; Hepatitis B Virus, Duck; Immunoblotting; Immunohistochemistry; In Situ Hybridization; Liver; Pancreas; RNA, Viral; Virus Replication

Chronic hepatitis B virus (HBV) infection is a major health problem worldwide. Antiviral strategies available at present, including interferon-alpha, have only limited efficacy, leading us to analyse the antiviral effects of penciclovir and famciclovir in the duck hepatitis B virus (DHBV) model of HBV infection in vitro and in vivo. In DHBV-infected duck hepatocytes, penciclovir effectively inhibited viral replication, with a concentration giving half-maximal inhibition of 0.25 microM. Furthermore, in vivo, penciclovir and its orally administered prodrug famciclovir strongly inhibited DHBV replication. These data demonstrate that penciclovir and famciclovir both have strong antiviral activities, and suggest that these agents might be useful for treating HBV infection in humans.

Topics: 2-Aminopurine; Acyclovir; Animals; Antiviral Agents; Ducks; Famciclovir; Guanine; Hepadnaviridae Infections; Hepatitis B Virus, Duck; Hepatocytes; Virus Replication

Detection of hepadnaviral DNA in extrahepatic tissues of human and animal models of hepatitis B virus (HBV) has raised the question of whether virus replication in organs other than the liver could be targeted for the treatment of chronic hepatitis B. Since duck hepatitis B virus (DHBV) replication is dynamic in the liver, kidney, pancreas, and spleen of newly hatched ducklings infected in ovo, we used the duck model and the new antiherpesvirus agent, famciclovir (FCV), to determine whether antiviral effect of nucleoside analogues on DHBV replication is pluripotential. Day-old ducklings hatched from eggs laid by a DHBV-carrier duck were bled and administered FCV (25 mg/kg/bd) orally for periods of 1, 2, 3, 6, 9, and 12 days. Seventeen (17) hours after the last dose of each regimen the duckling(s) was bled and postmortem samples of liver, kidney, pancreas, and spleen were snap-frozen and stored at -70 degrees C. Analysis of plasma samples of ducklings treated for 2 days and longer by dot-blot hybridisation showed that levels of DHBV DNA were reduced significantly compared to levels in samples collected before treatment begun. Southern blot hybridisation of tissue DNA corroborated these results and showed that DHBV DNA replicative intermediates in all the tissues examined were reduced to levels that reflected the amount of virus released into the blood of each treated duckling. It is concluded from these results that if antiviral agents could be transformed to active metabolites in any infected tissues including the liver, replication of hepadnaviruses would be inhibited.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Animals; Animals, Newborn; Antiviral Agents; Biotransformation; Disease Models, Animal; DNA, Viral; Ducks; Eggs; Famciclovir; Guanine; Hepadnaviridae Infections; Hepatitis B Virus, Duck; Kidney; Liver; Organ Specificity; Pancreas; Poultry Diseases; Prodrugs; Spleen; Viremia; Virus Replication; Xanthine Oxidase