Intrahepatic expression of hepatitis C virus antigens in chronic liver disease

Localization of hepatitis C virus (HCV) antigens was studied in fresh frozen and formalin-fixed, paraffin-embedded liver tissue by immunoperoxidase using monoclonal antibodies to nucleocapsid protein and polyclonal human immunoglobulin G purified from plasma containing antibodies to structural and non-structural antigens of hepatitis C virus. The results observed using monoclonal antibody to HCV core were similar to those of polyclonal IgG against HCV antigens in the majority of cases and both correlated well with HCV status as defined by 'nested' polymerase chain reaction. HCV antigens were detected in both hepatocytes and mononuclear cells. Using polyclonal human IgG, a small proportion of biliary epithelial cells were also positive in 6/29 patients. In most of the specimens examined, relatively few cells (1-5 per cent) were found to be positive for HCV antigens. The cryostat sections, using polyclonal IgG against HCV antigens, exhibited greater immunohistochemical staining, suggesting that the fixation and processing of the tissue may be a major factor in the conservation and the outcome of HCV antigen(s) findings. However, the results using monoclonal antibodies may reflect the specificity of antigen expression.