Expression of hepatitis C virus core protein in hepatocytes does not modulate proliferation or apoptosis of CD8+ T cells

Expression of hepatitis B virus x protein in hepatocytes suppresses CD8 T cell activity

Background

CD8⁺ T cells contribute to the clearance of Hepatitis B virus (HBV) infection and an insufficient CD8⁺ T cell response may be one of the major factors leading to chronic HBV infection. Since the HBx antigen of HBV can up-regulate cellular expression of several immunomodulatory molecules, we hypothesized that HBx expression in hepatocytes might affect CD8⁺ T cell activity.

Methods

We analyzed the activation and apoptosis of CD8⁺ T cells co-cultured with primary hepatocytes rendered capable of expressing HBx by recombinant baculovirus infection.

Results

Expression of HBx in hepatocytes induced low production of interferon-γ and apoptosis of CD8⁺ T cells, with no effect on CD8 T cell proliferation. However, transcriptional levels of H-2K, ICAM-1 and PD-1 ligand did not correlate with HBx expression in hepatocytes.

Conclusion

Our results suggest that HBx may inhibit CD8⁺ T cell response by regulation of interferon-γ production and apoptosis.

Association among Fas expression in leucocytes, serum Fas and Fas-ligand concentrations and hepatic inflammation and fibrosis in chronic hepatitis C

BACKGROUND

Replication of the hepatitis C virus (HCV) in peripheral blood mononuclear cells (PBMC) may impair immune functions and establish persistent infection. The aim of this study was to assess the influence of HCV on PBMC and their susceptibility to apoptosis in relation to liver inflammation and fibrosis.

METHODS

Eighty-one patients with chronic hepatitis C (CHC) were enrolled in this study. Flow cytometry was used to determine the amount of T cells (CD4(+), CD8(+)), B cells (CD19(+)), monocytes (CD14(+)) and natural killer cells (CD16(+)) in the peripheral blood and the expression of CD95(+) (CD95/APO-1) in each subset. Serum concentrations of sFas and sFasL were assessed by the enzyme-linked immunosorbent assay method.

RESULTS

An increased expression of Fas was observed in CD4(+) and CD8(+) cells in CHC. There was a more prominent expression of Fas on CD4(+) cells in HCV genotype 1b in contrast to 3a. Increased Fas expression on CD4(+) cells was seen in advanced stages of liver disease. Fas expression on monocytes was lower in advanced stages of liver inflammation and fibrosis. Serum sFas concentration was higher in CHC compared with the control group. There was an association between sFasL concentration and inflammatory activity in the liver. Serum sFasL concentration correlated positively with the mean intensity of fluorescence of the Fas receptor in CD4(+) and CD8(+) cells, granulocytes and monocytes.

CONCLUSION

These findings indicate that there is an increased susceptibility of PBMC to apoptosis, which can be attributed to the constant contact of leucocytes with the inflamed liver tissue, or from direct HCV influence.