Effect of interferon alpha on hepatitis B virus replication and gene expression in transiently transfected human hepatoma cells

Background/Aims: Chronic hepatitis B virus (HBV) infection is predominantly treated with interferon alpha (IFNα), which results in efficient reduction of the viral load only in 10–20% of treated patients. The mechanisms induced by IFNα resulting in reduction of viremia in responding patients are unknown. The aim of this study was to characterize HBV-specific IFNα-inducedintracellular inhibitory mechanisms and IFNα-sensitive HBV targets. Methods: To determine the antiviral activity, cells transiently transfected with HBV DNA were treated with IFNα and thereafter, viral products were quantified at different time points. Results: Time-dependent reduction of RNA, replicative DNA-intermediates, core protein and secreted HBsAg/HBeAg levels was observed in IFNα-treated cells. Viral RNA levels were reduced most effectively early post-treatment whereas those of core protein and replicative intermediates decreased later. By expression of subgenomic HBV sequences, an RNA target region mediating IFNα-induced RNA degradation was mapped. Conclusions: These data indicate that HuH7 cells transiently transfected with HBV-DNA represent a system well suited for detailed analysis of IFNα-induced antiviral mechanisms and HBV targets. At least two IFNα-induced HBV-specific antiviral activities are active in this system: one reduces the levels of core protein and replicative intermediates, the other leads to posttranscriptional degradation of HBV-RNA. Based on the established in vitro system a detailed characterization of the IFNα-sensitive RNA-region and of factors mediating this intracellular antiviral effect is feasible. This may lead to the development of novel strategies for therapy of chronic hepatitis.