Cytotoxic T lymphocytes inhibit hepatitis B virus gene expression by a noncytolytic mechanism in transgenic mice.

Abstract

During hepatitis B virus (HBV) infection, distinct host-virus interactions may establish the patterns of viral clearance and persistence and the extent of virusassoiated pathology. It is generally thought that HBV-speciflc class I-restricted cytotoxic T lymphocytes (CTLs) play a critical role in this process by destroying infected hepatocytes. This cytopathic m nism, however, could be lethal if most of the hepatocytes are Infected. In the current study, we demonstrate that class I-retricted HBV-speclfic CTLs profoundly suppress hepatoceliular HBV gene expression in HBV transgenic mice by a noncytolytic process, the strength ofwhich greatly exceeds the cytopathic effect of the CTLs in magnitude and duration. We also show that the regulatory effect of the CTLs is initially mediated by interferon y and tumor necrosis factor a, is delayed in onset, and becomes independent of these cytokines shortly after it begins. The data indicate that the anti-viral CTL response activates a complex regulatory cascade that inhibits hepatoceflular HBV gene expression without kifling the cell.The extent to which this mechanism contributes to viral clearance or viral persistence during HBV infection rem to be determined.The control of hepatitis B virus (HBV) infection is thought to be mediated by the class I-restricted cytotoxic T-lymphocyte (CTL) response. Patients with acute viral hepatitis, who successfully clear the virus, mount a multispecific polyclonal CTL response to several HBV-encoded antigens, whereas persistently infected patients with chronic hepatitis do not (1). Hepatitis B surface antigen (HBsAg)-specific murine CTL clones cause a necroinflammatory liver disease when they are injected into HBsAg-positive transgenic mice, and the cytopathic effect of the CTLs is largely mediated by the inflammatory cytokines that they release when they are activated by antigen recognition (2, 3). While the data indicate that the CTL response to HBV plays a critical role in viral clearance and disease pathogenesis, the extent to which viral clearance depends on the destruction of infected cells is not known at this time.We have shown that hepatocellular HBV gene expression in transgenic mice is negatively regulated, noncytopathically, by the pharmacological administration of recombinant interleukin (IL) 2 and tumor necrosis factor (TNF) a and that the IL-2 effect is mediated by TNF-a, which inhibits HBV gene expression by a posttranscriptional mechanism in these animals (4-6). We now report that hepatocellular HBV gene expression is profoundly inhibited, noncytopathically, by HBsAg-specific class I-restricted CTLs activated physiologically by antigen recognition in vivo, and we show that the inhibitory effect of the CTLs, which is mediated by TNF-a and interferon y (IFN-y), greatly exceeds their cytopathic effect in magnitude and duration. MATERIALS AND METHODSHBV Transgenic Mice. The two lineages studied were selected because they do not develop evidence of spontaneous liver disease and they display lineage-specific differences...

Viruses, Immunity, and Cancer: Lessons from Hepatitis B

“…50 While studying the basis for this observation we learned that, in addition to killing some of the hepatocytes, the CTL also downregulated the expression and replication of HBV by all of the hepatocytes in the liver without killing them. 49 In subsequent experiments using transgenic mice that contain the complete viral genome as recipients of CTLs, 47 we demonstrated that all of the viral RNAs, their translation products (HBcAg, HBeAg, and HBsAg), nucleocapsids, and episomal replicative DNA intermediates, are susceptible to this remarkable antiviral effect ( Figure 7). Two lines of evidence suggest that this antiviral process is noncytopathic and that it is mediated by inflammatory cytokines.…”

“…Importantly, the effector-to-target cell ratio in vivo in these experiments is very low (ϳ1/30 -1/100), so only a small fraction of the hepatocytes are killed by the combined effects of the CTLs plus the ensuing inflammatory response. [47][48][49] However, if many HBsAg-positive ground glass hepatocytes are present in the liver, a third process ensues in which the animal may die from fulminant hep-atitis because ground glass cells are exquisitely sensitive to destruction by IFN-␥, and this cytokine is actively secreted by CTLs after antigen recognition. 32 The striking similarities between the immunopathological and histopathological features of this model and acute viral hepatitis in man suggest that similar events may contribute to the pathogenesis of the human disease as well.…”

Ongoing Murine T1 or T2 Immune Responses to the Hepatitis B Surface Antigen Are Excluded from the Liver that Expresses Transgene-Encoded Hepatitis B Surface Antigen

“…Transgenic (tg) mouse lines have been constructed that express replication-competent HBV genomes or subgenomic HBV fragments in the liver (25)(26)(27)(28)(29)(30)(31)(32)(33). We used two alternative experimental strategies to test antiviral therapeutic vaccination approaches.…”

Hepatic CD206-positive macrophages express amphiregulin to promote the immunosuppressive activity of regulatory T cells in HBV infection

“…The cell suspension was gently overlaid onto Histopaque-1.077 (SigmaAldrich, St. Louis, MO, USA) and centrifuged at 750 g for 20 min. Mononuclear cells were collected from the interface, washed in PBS, and resuspended in Tris-NH 4 Cl solution to lyse residual RBCs. Cells were washed with PBS twice and were subject to further processing.…”

“…The T cell response to HBV is vigorous, polyclonal, and multispecific in acutely infected patients who successfully clear the virus and relatively weak and narrowly focused in chronically infected patients, suggesting that clearance of HBV is T cell dependent [2]. HBV-specific CD8 + T cells clear viral infections by killing infected cells through physical contact with infected cells and by secretion of IFN-g and TNF-a to inhibit HBV gene expression and replication [3][4][5][6]. However, impaired immune response contributes to the failure of viral clearance.…”