The Enhancer I Core Region Contributes to the Replication Level of Hepatitis B Virus In Vivo and In Vitro†

AUTOR(ES)

Bock, C.-Thomas

FONTE

American Society for Microbiology

RESUMO

Chronic hepatitis B virus (HBV) infection can lead to liver cirrhosis and hepatocellular carcinoma. Long-term interaction of the immune system with the virus results in the selection of escape mutants and viral persistence. In this work we characterize mutations in the enhancer I region isolated prior to liver transplantation from the HBV genomes of 10 patients with chronic HBV infection. The HBV-genomes were sequenced, and the enhancer I region was cloned into luciferase reporter constructs to determine the transcriptional activity. Functional studies were performed by transfecting HBV replication-competent plasmids into hepatoma cells. Analyses of the replication fitness of the mutant strains were conducted by biochemical analysis. In all HBV genomes the enhancer I region was mutated. Most of these mutations resulted in decreased transcriptional activity. The strongest effects were detectable in strains with mutations in the hepatocyte nuclear factor 3 and 4 (HNF3 and HNF4) binding sites of the enhancer I core domain. Replication-competent HBV constructs containing these mutations demonstrated up to 10-fold-reduced levels of virus replication. Before liver transplantation, when the mutant strains were detected in the patients' sera, low HBV DNA levels were found. After transplantation and reinfection with a wild-type virus, the levels of replication were up to 240-fold higher. Our results show that mutations in the enhancer I region of HBV have a major impact on HBV replication. These mutations may also determine the switch from high to low levels of viral replication which is frequently observed during chronic HBV infection.

Documentos Relacionados

• Expression of the hepatitis B virus core gene in vitro and in vivo.
• The degrees of hepatocyte nuclear but not cytoplasmic expression of hepatitis B core antigen reflect the level of viral replication in chronic hepatitis B virus infection.
• Identification of protein-binding sites in the hepatitis B virus enhancer and core promoter domains.
• Detection of pre-C and core region mutants of hepatitis B virus in chronic hepatitis B virus carriers.
• In vivo phosphorylation and protein analysis of hepatitis B virus core antigen.