Detection of genomic and intermediate replicative strands of hepatitis C virus in liver tissue by in situ hybridization.

Nonisotopic in situ hybridization using a digoxigenin-labeled cDNA probe to the 3' nonstructural region (NS5) of hepatitis C virus (HCV) was performed on liver tissue from 33 patients. The results were compared with PCR detection of HCV RNA performed on 24 of the biopsies. Nonisotopic in situ hybridization correlated well with PCR findings. Hybridization signals were detected, within the cytoplasm and nuclei/nucleoli of hepatocytes, mononuclear, and biliary epithelial cells. In patients with clinically and histologically defined chronic active hepatitis related to active HCV infection, HCV genome was frequently detected in biliary epithelium and correlated well with biliary damage, an otherwise uncommon finding in chronic active hepatitis due to other hepatotropic viruses. Further studies using sense and antisense probes synthesized from the 5' non-coding region of the HCV genome confirmed the localization of positive strand of HCV in the above cell populations. The replicative intermediate strand was also present in all cells, although less frequently observed, apart from biliary epithelium, where negative strand of HCV was undetectable. The findings of HCV genome in liver biopsies of two patients with no significant histological abnormalities may suggest that the damage seen in chronic HCV infection is immune mediated, although the cytopathic effect of the virus may also be important.