Prevalence of antibody against the core protein of hepatitis C virus in patients with hepatocellular carcinoma.

We have cloned the whole structural region of the hepatitis C virus (HCV) genome and transiently expressed the nucleocapsid protein in animal cells. Since the nucleotide sequences of this region of the HCV genome has been shown to be highly conserved among different HCV isolates, the assay detecting the antibody to this expressed protein is useful for studying the pathogenicity of HCV. In this work, we investigated the presence of antibodies to HCV nucleocapsid protein (p22) in patients with hepatocellular carcinoma (HCC) and compared its frequency with that of antibody to HCV non-structural protein (C-100), which is presently applied for blood screening for transfusion and diagnosis for chronic hepatitis C. By a sensitive Western blot analysis, 85 of 102 (83.3%) sera of hepatitis B virus surface antigen (HBsAg)-negative HCC patients were positive for the antibody to p22 (anti-p22), whereas 68 of the same 102 cases (66.7%) were positive for the anti-C100 by ELISA. The prevalence of anti-p22 in 23 HBV carrier HCC patients, 56 patients with non-HCC cancer and 100 healthy blood donors were 4.3, 12.5 and 1.0%, respectively. Thus, high prevalence of anti-p22 in non-B HCC confirmed that HCV infection is closely related to the development of HCC. Furthermore, the anti-p22 assay can detect HCV-infected patients who could not previously be identified as such by the present anti-C100 assay.