THE HEPATITIS-B VIRUS-X PROTEIN UP-REGULATES TUMOR-NECROSIS-FACTOR-ALPHA GENE-EXPRESSION IN HEPATOCYTES

Human hepatocytes infected by hepatitis B virus (HBV) produce the proi nflammatory cytokine, tumor necrosis factor alpha (TNF-alpha). In this study, we explored the mechanism of induction of TNF-alpha synthesis by HBV. We found that the stable HBV-transfected hepatoma cell line, 2 .2.15, expressed high-molecular-weight (HMW) TNF-alpha mRNAs, which we re absent in the parent HepG2 cells. Treatment of 2.2.15 cells with in terferon alfa (IFN-alpha) and/or interleukin-1 beta (IL-1 beta) reduce d both viral gene transcription and TNF-alpha mRNA expression. Transie nt or stable transfection of hepatocyte-derived cell lines with HBV X protein (HBx) expression vectors induced the production of biologicall y active TNF-alpha. In these cells, the HBx-induced TNF-alpha was dete cted both as cell-associated and soluble forms. Luciferase gene-expres sion assays showed that the TNF-alpha gene promoter contained target s equences for HBx trans-activation within the proximal region of the pr omoter. These results indicate that the hepatocyte TNF-alpha synthesis induced by HBV is transcriptionally up-regulated by HBx. Thus, HBx ma y have a role in the induction of the intrahepatic inflammatory proces ses that take place during acute and chronic hepatitis B.