Physicochemical and immunological properties of the hepatitis B surface antigen containing the preS2 9 amino acid sequence produced by a recombinant yeast.

The hepatitis B virus surface antigen containing the preS2 nine amino acid sequence produced by a recombinant Saccharomyces cerevisiae (yHBsAg) was purified and its physicochemical properties were determined. Ultrastructurally, the yHBsAg was found to be a homogeneous spherical particle with a diameter of 24 +/- 4 nm. The homogeneity of the yHBsAg particles was also demonstrated by analyses of their buoyant density and isoelectric point. They consisted of protein (53%), lipid (36%) and carbohydrate (11%), and the alpha-helix content was estimated to be 32%, differing from the reported values for human plasma-derived HBsAg (hHBsAg). Immunodiffusion analysis showed that the antigenic specificity of yHBsAg was identical to that of hHBsAg. Immunization of mice demonstrated that the immunogenicity of the yHBsAg was significantly higher than that of hHBsAg.