Suppression of hepatitis B virus expression and replication by hepatitis C virus core protein in HuH-7 cells

Abstract

Hepatitis B and C viruses (HBV and HCV, respectively) are associated with acute and chronic liver diseases and hepatocellular carcinoma. To elucidate the molecular status of superinfection with these two hepatitis viruses, we cotransfected the full-length or truncated version of HCV structural genes (core and envelope 1) together with the cloned HBV DNA into a human hepatoma cell line (HuH-7). Expression of HBV-specific major transcripts (3.5 and 2.1 kb), as well as HBV antigens (hepatitis B surface antigen and hepatitis B e and core antigens), was reduced about two- to fourfold by the presence of the HCV structural genes. In addition, the secretion of HBV viral particles, including the viral nucleocapsid and mature virion, was drastically suppressed about 20-fold. Analysis of the intracellular HBV core protein-associated nucleic acid indicated that the encapsidated HBV pregenomic RNA was similarly reduced about 14-fold. Deletion analysis of the HCV structural genes demonstrated that the core gene alone or the fragment containing the core protein's N-terminal 122 amino acid residues conferred the same level of suppressive activity as the full-length structural genes. By indirect immunofluorescence, we found that the core protein of HCV was located in the cytoplasm of transfected HuH-7 cells at day 3 posttransfection and was targeted to the nucleus at day 6. Thus, the kinetics of the suppressive effect exerted by HCV constructs matched the timing of core protein entrance into the nucleus. Our results substantiate the clinical finding that HBV markers are suppressed by superinfection with HCV and further imply that this inhibitory effect may occur in the processes of transcription and encapsidation of HBV pregenomic RNA and may be mediated by the core protein of HCV. The deduced amino acid sequence of the HCV core protein has revealed that it is a basic protein which contains a putative DNA-binding motif (SPRG), as well as triplicate nuclear localization signals and several putative protein kinase A and C recognition sites. These characteristics imply that the HCV core protein can also function as a gene-regulatory protein.

HBV superinfection in hepatitis C virus chronic carriers, viral interaction, and clinical course

“…8 In chronic HBV/HCV concurrent infection, it has been observed that HCV also exerts an inhibition on the expression of the HBV genome. [1][2][3][4]6,8 Our data showing that the patients in the case BC group and those in the control B group had a similar HBV viral load and similar dynamics of HBV-DNA negativization seem to refute an active inhibition of the chronic HCV infection on the acute HBV replication. This is suggested also by the observation that the HBV-DNA plasma values are similar in the case BC group and in the control B group at the different screening points.…”

“…P atients with chronic hepatitis B virus (HBV)/hepatitis C virus (HCV) concurrent infection show a reciprocal inhibition of viral genomes, an association with a severe clinical presentation, and an infrequent response to interferon alfa treatment. [1][2][3][4][5][6][7][8][9][10] Instead, very lit-tle is known about HBV/HCV acute concurrent infection because only a few case reports are available in the literature. 11,12 Also, little is known about HBV acute infection when it develops in chronic HCV carriers, but the few case reports published on the topic suggest an association with a severe clinical presentation.…”

Role of hepatitis B, C, and D viruses in dual and triple infection: Influence of viral genotypes and hepatitis B precore and basal core promoter mutations on viral replicative interference

“…These data concur with the in vitro demonstration by Shih et al that in the absence of host factors, the HCV-core protein can bind to HBV-RNA and suppress HBV gene expression and replication. 22 Using sequence comparison, Pontisso et al uphold this observation with the finding that the HBV core protein and the 101-102 core domain of HCV genotypes 1 and 3 share an important Arg-rich motif. 23 HBV replication would therefore be more effectively inhibited by HCV genotypes 1 and 3 than the remaining HCV genotypes, which do not share this homology with HBV.…”

Regulation of Hepatitis B Virus Replication by the Phosphatidylinositol 3-Kinase-Akt Signal Transduction Pathway

“…Finally, previous work suggests that HCV-mediated inhibition of HBV replication in patients coinfected with the two viruses most likely occurs through an HCV protein-mediated intracellular pathway (36). Studies in search of the HCV proteins that are responsible for the inhibition have reported that HCV core and NS2 proteins inhibited HBV replication in cultured cells, but so far, the underlined molecular mechanism(s) is not clear (9,12,38,43,44). Here we demonstrate that the HCV NS5A protein inhibits HBV gene transcription and DNA replication via the activation of the PI3K-Akt pathway and, thus may be, at least in part, responsible for the observed inhibition of HBV replication during HCV coinfection.…”