ULTRASTRUCTURAL ANALYSIS OF HEPATITIS-B SURFACE-ANTIGEN PRODUCTION INVITRO

  • 1 January 1982
    • journal article
    • research article
    • Vol. 47  (5) , 465-470
Abstract
Recently, several continuous cell lines (among these human hepatocellular carcinoma PLC/PRF/5 cells) producing hepatitis B surface antigen (HBsAg) were established from human hepatocellular carcinomas. The cultured cells provide the first opportunity to study HBsAg synthesis and secretion in vitro. HBsAg, but not hepatitis B core antigen, was localized by the fluorescent antibody technique in the cytoplasm and on the surface of the cultured cells. Under EM, the PLC/PRF/5 cells displayed morphologic characteristics of both hepatocytes and hepatocellular carcinoma cells. However, 22-nm. spherical or filamentous HBsAg particles were not seen in the cells, although spherical HBsAg particles were observed in the supernatant culture media. Thus, the indirect immunoperoxidase technique was used to demonstrate HBsAg at the ultrastructural level. Electron-dense reaction product was detected along the nuclear envelope, on rough-surfaced endoplasmic reticulum, and in cisternae of endoplasmic reticulum. Evidently, HBsAg is synthesized on rough-surfaced endoplasmic reticulum and transferred into endoplasmic cisternae for processing and secretion. This mode of HBsAg production is identical with that observed in hepatocytes of patients infected with hepatitis B virus. The absence of detectable intracellular HBsAg particles suggests that the cultured cells secrete the particles very rapidly or that they may have a defect in intracisternal packaging of HBsAg into particles.