Hepatitis B surface antigen and albumin in human hepatocytes. An immunofluorescent and immunoelectron microscopic study.

A close correlation between the presence of hepatitis B surface antigen and albumin in the cytoplasm of hepatocytes infected with hepatitis B virus was established by immunofluorescence and immunoelectron microscopy in 52 liver biopsy specimens of various forms of hepatitis and liver cirrhosis. Albumin deposits usually accompanied cytoplasmic content of hepatitis B surface antigen, but were less frequently observed together with hepatitis B antigen localized in or on the membranes. Ultrastructural observations demonstrated albumin on the tubular and spherical forms of hepatitis B surface antigen in the endoplasmic reticulum. The hepatocytes with the content of hepatitis B surface antigen and albumin showed the ability of binding with the fluorescein-labeled preparation of polymerized human serum albumin. The affinity of polymerized albumin to hepatitis B surface antigen was considerably increased after preincubuation of liver sections with 2-mercaptoethanol that removed most of the originally present albumin. This may be indicative for the role of disulfide bonds in the formation of hepatitis B surface antigen-albumin complexes. These results justify the hypothesis that albumin may be incorporated into the viral coat protein during its synthesis in the cytoplasm of infected hepatocytes.