Letter: HBsAg on cell membrane in symptom-free carrier

Radioimmunometric assay for hepatitis B surface antigen on the surface of infected cells

It has been difficult to differentiate hepatitis B surface antigen (HBsAg) on the cell surface from intracellular or intramembranous HBsAg that is not exposed to the host immune response. We describe here a radioimmunometric assay for HBsAg on the cell surface using HBsAg producing hepatocellular carcinoma cell lines and fibroblasts transfected with cloned hepatitis B virus DNA as models. The assay is sensitive, specific, simple and takes approximately 1 1/2 h. The procedure may be modified to compare quantitatively cell surface with intracellular HBsAg and to demonstrate other cell associated hepatitis B virus antigens such as HBcAg and HBeAg.

Intracellular transport and secretion of hepatitis B surface antigen in mammalian cells

The oligosaccharide processing and secretion of hepatitis B surface antigen (HBsAg) was studied in Chinese hamster ovary cells stably transfected with the gene coding HBsAg. HBsAg was secreted from cells with a relatively long half time (ca. 5 h). This appeared to be a characteristic of HBsAg itself, since HBsAg-producing cells infected with vesicular stomatitis virus transported the viral envelope glycoprotein to the cell surface with normal kinetics (half time of ca. 30 min). The secreted HBsAg was comprised of both the unglycosylated (P20) and the glycosylated (G25) polypeptides, characteristic of HBsAg isolated from human serum or secreted from other cell lines (C. W. Crowley, C.-C. Liu, and A. D. Levinson, Mol. Cell. Biol. 3:44-55, 1983; M. F. Dubois, C. Pourcel, S. Rousset, C. Chang, and P. Tiollais, Proc. Natl. Acad. Sci. U.S.A. 77:4549-4553, 1980; C.-C. Liu, D. Yansura, and A. D. Levinson, DNA, 1:213-221, 1982; G. M. Macnab, J. J. Alexander, G. Lecatsas, E. M. Bey, and J. M. Urbanocvicz, Br. J. Cancer, 24:509-515, 1976; A. M. Moriarity, B. H. Hoyer, J. W.-K. Shih, J. L. Gerin, and D. H. Hamer, Proc. Natl. Acad. Sci. U.S.A. 78:2606-2610, 1981; D. L. Peterson, J. Biol. Chem., 256:6975-6983, 1981). The glycosylated polypeptide (GP25) contained complex oligosaccharide chains. Cell-associated HBsAg also was comprised of both an unglycosylated and a glycosylated polypeptide; however, the glycosylated form (GP23) contained only high-mannose oligosaccharide chains. No oligosaccharide processing of the high-mannose chains could be detected within the cells. Thus, most of the time before secretion of HBsAg from cells must have been spent in a pre-Golgi or early Golgi compartment. Glycosylation was inhibited completely by tunicamycin, although unglycosylated particles were still secreted from cells and were antigenic. The secretion and oligosaccharide processing of HBsAg were inhibited with high concentrations of monensin, but at lower concentrations of monensin HBsAg was still secreted, although only half of the oligosaccharide chains were processed to the complex form.

Histopathology and localization of viral antigens in the liver of HBsAg positive homosexuals

In a survey of the prevalence of chronic hepatitis B in a male homosexual population, liver biopsies were done in 28 asymptomatic patients who had persistently raised aminotransferases. Four patients had active cirrhosis (AC), 13 had chronic active hepatitis (CAH) of various degrees of severity and 11 had either chronic persistent hepatitis (CPH) or minor changes of the type seen in hepatitis B virus carriers. Core associated antigens and surface antigen, were demonstrated by the PAP immunoperoxidase method in 20 cases. Core and surface antigens tended to be present in the same areas of the biopsy and quantitation showed higher core to surface antigen ratios in CAH than in CPH, the difference being statistically significant. In seven cases no core-associated antigens were demonstrated in the presence of surface antigen: most of these patients had either inactive disease or active cirrhosis. In one carrier neither antigen was demonstrated. Ten patients had two or more biopsies. Four of these had no treatment and the amounts of core and surface positive cells in the liver did not increase. Six were treated with immunosuppressants. This did not alter the degree of either inflammation or fibrosis. but the number of surface and core antigen positive cells in the liver was higher after treatment in almost every case.

Correlations between anti-albumin antibodies and HBsAG in hepatic patients

A new category of autoantibodies--antipolymerized albumin antibodies (AAA)--was discovered in 1974. Studies performed from 1974 to 1976 showed their diagnosis and prognostic values in hepatic diseases; the AAA tests [immunodiffusion (ID) and hemagglutination (HS)] made possible a good estimation of the total liver cell function. Without being specific for a viral hepatitis B infection, highly significant linear correlations were found for AAA precipitin and agglutinin positivities with presence of HBsAg. High titre of AAA agglutinins unaccompanied by a positive ID test, characterise the "healthy carrier" of the HBsAg, while the isolated AAA positivity in ID is met in more severe, long-standing hepatic diseases.