Antonio Ponzetto

Evidence for replication of hepatitis delta virus RNA in hepatocyte nuclei after in vivo infection

Examination of a naturally infected human liver and experimentally infected chimpanzee and woodchuck livers by in situ hybridization showed that hepatitis delta virus (HDV) RNA was restricted to hepatocytes. Genomic RNA was 20-30 times more abundant than antigenomic RNA and was predominantly single-stranded while antigenomic RNA was predominantly double-stranded. In acute delta hepatitis, viral RNA was a more reliable marker of virus infection in single cells than hepatitis delta antigen (HDAg) while in chronic hepatitis both markers were usually present in the same cell. In all cases, viral antigen and RNA were localized predominantly to the nuclei of infected cells. Thus, replication of HDV RNA is closely associated with HDAg expression at the cellular and intracellular level and it is likely that this new class of defective animal RNA viruses replicates in the nucleus of the infected cells.

Radioimmunoassay and characterization of woodchuck hepatitis virus core antigen and antibody

Solid-phase radioimmunoassays for woodchuck hepatitis virus core antigen (WHcAg) and antibody (anti-WHc) were developed. WHcAg in woodchuck liver homogenates was characterized by ultracentrifugation in CsCl gradients; both heavy (1.35 g/cm3) and light (1.31 g/cm3) cores were obtained from the liver of an animal during acute WHV infection, which is consistent with observations in hepatitis B virus infection in man. Endpoint titers of anti-WHc were higher in chronic WHV carriers than in animals recovered from acute infections. Both IgM and IgG anti-WHc antibodies were produced by infected woodchucks. A survey of colony woodchucks demonstrated that 88/89 animals having one or more markers of past or ongoing WHV infection were positive for anti-WHc. Thus, serum anti-WHc appears to be a sensitive marker of WHV infection.