title: Construction of avian hepadnavirus variants with enhanced replication and cytopathicity in primary hepatocytes.
abstract: Hepadnaviruses cause persistent noncytopathic infections of hepatocytes in humans and other animals. Virus replication depends on the pool of viral covalently closed circular DNA (cccDNA) molecules, which serve as transcriptional templates in the nuclei of infected cells. The size of this pool of cccDNA molecules is regulated by the ability of the large envelope protein of the virus to direct newly synthesized viral DNAs into a pathway for viral secretion and thereby inhibit their utilization for viral cccDNA synthesis. In this study, we showed that single amino acid changes in the large envelope protein could cause profound changes in cccDNA levels in transfected permissive cells or in infected cultured hepatocytes. While defects in cccDNA regulation were accompanied by a decrease of enveloped virus production in transfected cells, primary hepatocytes infected by such mutant viruses transiently produced wild-type or higher levels of enveloped virus. Moreover, high levels of cccDNA were always associated with cytopathic effects in the infected hepatocytes. The results demonstrate that the large envelope protein promotes persistent noncytopathic infection of hepatocytes by acting as an overall repressor of virus replication.
authors.affiliation: Department of Cell Biology, University of New Mexico School of Medicine, Albuquerque 87131.
authors.forename: R J
authors.initials: RJ
authors.lastname: Lenhoff
authors.forename: J
authors.initials: J
authors.lastname: Summers
mesh_terms: D000818:Animals; D002460:Cell Line; D003588:Cytopathogenic Effect, Viral; D004279:DNA, Viral / Q000096:biosynthesis; D004371:Hepatitis Virus, Duck / Q000235:genetics / Q000472:pathogenicity*; D066298:In Vitro Techniques; D008099:Liver / Q000382:microbiology*; D016297:Mutagenesis, Site-Directed; D012367:RNA, Viral / Q000096:biosynthesis; D013329:Structure-Activity Relationship; D014162:Transfection; D014779:Virus Replication
chemical_list: D004279:DNA, Viral; D012367:RNA, Viral