Further studies on production and characterization of HBsAg derived from a human hepatoma cell line (PLC/PRF/5)

Four aspects for the use of PLC/PRF/5 cell line as an alternative source of HBsAg for hepatitis B vaccine production were assayed in this study: improvement in HBsAg production with chemical inducers, tests for the presence of hepatitis B virions, antigenic topology of HBsAg polypeptides and immunogenicity of HBsAg in guinea pigs. 10(-6) M dexamethasone and/or 10(-4) M sodium butyrate treatments enhanced HBsAg production by a factor of approximately two when compared with untreated cells. Particles of 35 nm diameter produced by PLC/PRF/5 cells were observed at a CsCl density of 1.22-1.24, associated with typical HBsAg 22 nm spheres. These particles did not contain HBV DNA as proved by negative results of hybridization using cloned HBV/DNA as a probe. Western blot analysis revealed that only polypeptides P 22000 (P1) and P 26000 (P2) were specifically recognized by a human anti-HBs serum, irrespective of the origin of HBsAg, i.e. human serum or PLC/PRF/5 hepatoma cell line. HBsAg purified from PLC/PRF/5 cell line was immunogenic in guinea pigs. However, the humoral response was delayed and lower in terms of anti-HBs titers when compared to the response obtained after immunization with a licensed hepatitis B vaccine (HEVAC B, Institut Pasteur Production).