Cytoplasmic localization of hepatitis B core antigen in hepatitis B virus infected livers.

Routine use of commercially available antisera against hepatitis B core antigen (HBcAg) obtained from Escherichia coli transfected with HBV-DNA, has permitted a re-evaluation of the histochemical distribution of the antigen in liver tissue. HBcAg, classically described almost exclusively in the nucleus, was found with a very high frequency in the cytoplasm of liver cells. Our data indicate, however, that formalin fixation and paraffin embedding destroy part of HBcAg antigenicity and eliminate most of its cytoplasmic expression. HBcAg was found in 6/7 (85.7%) of HBsAg/HBeAg positive subjects, and in 2/12 (16/6%) of HBsAg/anti-HBe positive subjects; in both subgroups the cytoplasmic expression of the antigen correlated with the presence of circulating hepatitis B virus-deoxyribonucleic acid (HBV-DNA).