Recombinant hepatitis B virus surface antigen carrying the pre-S2 region derived from yeast: purification and characterization
Abstract Modified hepatitis B virus surface antigen (HBsAg) carrying the pre-S2 region (HBsAg M-P31c) has been highly purified from the recombinant yeast Saccharomyces cerevisiae . The purified HBsAg M-P31c formed spherical particles with a diameter of about 20 nm, which were similar in both shape and size to human plasma-derived HBsAg small particles (h-HBsAg). The M-P31c particles were composed of two major glycoproteins with molecular masses of 37 kDa (GP37) and 34 kDa (GP34). GP37 and GP34 had identical polypeptide backbones (P31) of 31 kDa and had N-linked sugar chains with a molecular mass of about 3 kDa at the Asn 4 residue. GP37 has additional sugar chain(s) in the pre-S2 region. The sugar chains were composed of mannose and N -acetylglucosamine. Like h-HBsAg, the particles also contained phospholipids, triglycerides, and free fatty acids. On the other hand, little cholesterol was contained in the particles. M-P31c vaccine adsorbed on Al(OH) 3 gel elicited anti-pre-S2 antibodies in addition to anti-S antibodies. These results demonstrate that M-P31c particles are promising as an improved immunogen for the hepatitis B vaccine.