TNF-alpha and TNF Receptor Type p75 are Induced by Recombinant Hepatitis C Virus Proteins in Peripheral Mononuclear Blood Cells

Abstract

Recent studies showed an activation of the TNF system in patients with chronic Hepatitis C Virus (HCV) infection correlating with the severity of the disease. Peripheral blood mononuclear cells (PBMC), representing extrahepatic sites for HCV replication and a source of inflammatory cytokines play a central role in the regulation of immune-mediated response. The aim of this project was to imitate the very first contact with HCV of healthy individuals. To characterize the innate and primary response of PBMC to HCV components, we studied the cellular induction of TNF-alpha and TNF specific receptors TNFR–p55, -p75 after stimulation with recombinant HCV proteins in vitro. PBMC of 14 healthy individuals were incubated with recombinant HCV proteins from different core regions and non-structural (NS) proteins (NS3 and NS4) at optimal concentrations. TNF-alpha, soluble TNF receptors -p55 and -p75 were determined by enzyme-linked-immuno-assays and synthesis of specific mRNA was analyzed by RT-PCR technique. The most potent specific stimulus was the HCV core derived protein aa 1–83 with induction of TNF-a (5,8±1,9 ng/ml; p<0.001) and TNFR-p75 (3,9±0.8 ng/ml; p<0.001), respectively. The second most important inducer was NS4, followed by core and NS3. Protein synthesis was adequately paralleled by specific mRNA induction. The data show that stimulation of immunocompetent PBMC with HCV proteins leads to a specific enhancement of the TNFR-p75 protein as compared to TNF-p55. The corresponding antagonist TNF-alpha and its receptor TNFR-p75 are therefore not only involved in the pathogenesis of chronic HCV infection but already in the very early onset of the infection.