Inhibition by Woodchuck Hepatitis Virus of Class I Major Histocompatibility Complex Presentation on Hepatocytes Is Mediated by Virus Envelope Pre-S2 Protein and Can Be Reversed by Treatment with Gamma Interferon

Abstract

Presentation of class I major histocompatibility complex (MHC) is severely down-regulated on hepatocytes in chronic hepatitis caused by woodchuck hepatitis virus (WHV).To determine which of the viral proteins mediates class I MHC antigen suppression, cultured normal woodchuck hepatocytes were transfected with the complete WHV genome, sequences encoding individual virus proteins, or whole virus genomes in which transcription of selected proteins was disabled by site-specific mutagenesis. It was found that hepatocyte presentation of class I MHC antigen was significantly inhibited following transfection with complete WHV genome or with viral subgenomic fragments encoding envelope pre-S2 protein or pre-S1 protein, which naturally encompasses pre-S2 amino acid sequence. In contrast, hepatocytes transfected with WHV X gene alone demonstrated a profound enhancement in the class I antigen display, whereas those expressing virus major S protein or nucleocapsid (core) protein were not different from control hepatocytes. Analysis of the mutated WHV sequences confirmed that the envelope pre-S2 protein was responsible for inhibition of the class I MHC antigen display. Interestingly, treatment with recombinant woodchuck gamma interferon (rwIFN-␥) restored the inhibited presentation of the class I antigen. Moreover, the class I antigen suppression was not associated with down-regulation of hepatocyte genes for class I MHC heavy chain, ␤ 2 -microglobulin, transporters associated with antigen processing, and proteasome subunits. These findings indicate that the defective presentation of class I MHC antigen on hepatocytes transcribing WHV is a consequence of posttranscriptional suppression exerted by virus pre-S2 protein and that this hindrance can be fully reversed by IFN-␥.Hepatitis B virus (HBV) is a member of the hepadnavirus family, which includes, among several mammalian and avian viruses, woodchuck hepatitis virus (WHV), which naturally infects eastern North American woodchucks (Marmota monax). Woodchucks infected with WHV represent a highly valuable natural model of hepatitis B in which molecular, immunological, and histological sequelae of virus-induced liver inflammation closely resemble those encountered in humans, including development of chronic hepatitis (20,32). It is now also evident that HBV and WHV invade and replicate not only in hepatic tissue but also in the lymphatic system, although under most circumstances, less vigorously than in the liver (24-26). The host cellular immune responses directed against hepadnavirus protein epitopes displayed on infected hepatocytes, particularly those mediated by cytotoxic T lymphocytes (CTL), are regarded to be crucial in the recovery from acute hepatitis as well as in the induction of hepatocellular damage in actively progressing infection (3). In contrast to acute hepatitis, which is characterized by a strong and specific CTL response directed towards multiple virus epitopes, chronic hepatitis B is characterized by a weak and narrowly focused CTL antiviral reactivity. It ...

Superinfection with Woodchuck Hepatitis Virus Strain WHVNY of Livers Chronically Infected with Strain WHV7

“…The final constructs pJSWHVNY-4C4 and pJSWHV7-2C6 were used as the standards for the analysis of WHV DNA and RNA by conventional PCR and qPCR assays. For the analysis of WHVNY cccDNA, a new DNA standard was generated based on the strategy described previously (36). The WHVNY rcDNA isolated from the serum of monoinfected woodchuck F6541 was used for the amplification of two fragments of the WHVNY genome.…”

Bicistronic Woodchuck Hepatitis Virus Core and Gamma Interferon DNA Vaccine Can Protect from Hepatitis but Does Not Elicit Sterilizing Antiviral Immunity

“…It is of note that WCM-260 cells normally do not express IFN-␥ and they display the class I MHC antigen at a minuscule level (70,71). For controls, naïve (nontransfected) WCM-260 hepatocytes and WCM-260 cells transfected with pC-WHc exposed to B1Bb9 monoclonal antibody (MAb) specific for the heavy chain of woodchuck class I MHC molecule (42,43), were used.…”

“…Expression of wIFN-␥ was determined in transfected WCM-260 hepatocytes by examining the cytokine mRNA using PCR with a reverse transcription (RT) step (RT-PCR) and conditions described before (70), as well as by assessing upregulation of the class I major MHC antigen by immunofluorescence staining and confocal microscopy as reported previously (70,71). It is of note that WCM-260 cells normally do not express IFN-␥ and they display the class I MHC antigen at a minuscule level (70,71).…”

Understanding the immunopathogenesis of chronic hepatitis B virus: An Asian prospective

“…Perhaps the kinetics of viral replication within the infected hepatocytes might directly influence the triggering of NK cells and the subsequent induction of an effective T-cell response. 53 However, whether this is due to inhibition of human leukocyte antigen (HLA) class I expression (which can stimulate NK cells) 54 or upregulation of 'stimulatory receptors' (like MIC-A, MIC-B or UPB-1, 2, 3) 55 on infected cells is unknown. What seems well established is that the differences in the adaptive immune response to HBV, which characterize chronically infected patients and those with resolved HBV infection, are heavily influenced by the immunological events occurring during the initial phase of HBV replication.…”