Hepatitis B Virus Antigen Development in Cultured Human Hepatocytes 1

Abstract

Summary

Australia antigen, now termed hepatitis B antigen or HB antigen, has been demonstrated to be closely associated with the serum hepatitis virus and to be an indicator for the presence of the infective agent. The development of HB antigen in cultured human fetal hepatic parenchymal cells (hepatocytes) after exposure to acute-phase sera containing the antigen is described. Hepatitis B antigen was demonstrated in the cultured cells by immunofluorescence methods and specificity determined by agar gel diffusion, counterelectrophoresis, blocking and absorption experiments, and examination of frozen sections of liver containing the antigen. Development of HB antigen in the cultured fetal hepatocytes was slow and occurred in a limited number of cells. Hepatitis B antigen was detected initially as irregularly shaped granular deposits in the nuclei of the hepatocytes and was first observed 2 weeks after exposure. These observations support the concept of the hepatocyte nucleus as the primary site of viral replication. Hepatitis B antigen was observed in the cytoplasm of cultured hepatocytes beginning 4 weeks following exposure. Five to six weeks after exposure, cytoplasmic-antigen-containing hepatocytes were detected in increased numbers, occurring as foci or plaques of 2-4 cells. The foci of antigen-containing cells continued to increase slowly in size. These findings may imply a secondary cytoplasmic phase in the development of hepatitis B virus and also suggest cell to cell transfer. The small number of cultured hepatocytes in which HB antigen developed may be due to a limited capacity of hepatocytes from fetuses in early stages of gestation to support viral synthesis, or to a blocking effect exerted by the large ratio of noninfective to infective virus particles present in the inoculum.

Grateful acknowledgment is given to the Blood Grouping Laboratory of the Buffalo General Hospital for serum specimens and to the Children's Hospital of Buffalo for fetal tissue and to Dorothy C. Noyes for invaluable assistance.