Enhanced Replication Contributes to Enrichment of Hepatitis B Virus with a Deletion in the Core Gene

Abstract

Accumulation in immunosuppressed patients of hepatitis B virus (HBV) with a deletion in the C gene is associated with severe liver disease. The aim of this study was to determine the phenotype of such genomes in vitro. Four C gene fragments with different types of deletions were inserted in the context of a wild-type genome and tested by transfection into HuH7 cells. The deletions did not influence mRNA and surface protein levels. Truncated C gene translation products were expressed only from variants with in-frame deletions, whereas full-length polymerase was expressed from all variants at a similar or higher level than in wild-type virus. None of the variants was competent for autonomous replication; however, they produced 2- to 4.5-fold more progeny DNA than wild-type HBV when sufficiently complemented with wild-type core protein. Similarly, when variant and wild-type DNA were cotransfected in different ratios, the variants produced 2- to 5-fold more progeny DNA relative to the wild-type; this enrichment required the expression of the viral polymerase in cis. The mechanism of enrichment depended on the percentage of variant in the transfected DNA mixture. When the transfected DNA contained a small percentage of variant, enhanced replication of the variant accompanied by no or little suppression of wild-type replication was seen. Accordingly, overall production of progeny virus was slightly increased. At a high percentage of variant DNA, replication of both variant and wild-type decreased, probably due to a shortage of wild-type core protein. In conclusion, emergence of C gene deletion variants in vivo may be due to enhanced replication mediated at the level of encapsidation or reverse transcription. If the variants constitute a small part of the ccc DNA, they can be fully trans-complemented by wild-type virus which may increase the overall virus production.

Novel Type of Hepatitis B Virus Mutation: Replacement Mutation Involving a Hepatocyte Nuclear Factor 1 Binding Site Tandem Repeat in Chronic Hepatitis B Virus Genotype E

“…Core deletions are reported to be related to the presence of HBeAg and seroconversion in the near future (43). In an in vitro experiment, the core deletion type can replicate more efficiently than the wild type when complemented with wild-type core protein, and the replication enhancement by core deletion is not through the enhancement of transcription (11). Although a minor wild-type clone might enhance the replication of a core deletion clone, HNF1 binding seems to be the major cause of replication enhancement.…”

Replication of Naturally Occurring Woodchuck Hepatitis Virus Deletion Mutants in Primary Hepatocyte Cultures and after Transmission to Naive Woodchucks

“…HBV CID mutants were enriched if they were cotransfected with HBV wild-type DNA into a human hepatoma cell line. Consistent with these results, Gunther et al demonstrated that HBV CID mutants show an enhanced replication (15).…”

Hepatitis B virus as a gene delivery vector activating foreign antigenic T cell response that abrogates viral expression in mouse models

“…Interestingly, the rHBV in our study was similar to a naturally occurring HBV variant (⌬C-144) identified by Will and collegues. 22 This variant produced 2-to 4.5-fold more progeny DNA than wtHBV when sufficiently complemented with wild-type core protein. In addition, rHBV has a short viral genome that favors pgRNA packaging.…”