Synthesis in animal cells of hepatitis B surface antigen particles carrying a receptor for polymerized human serum albumin.

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Abstract
A recombinant plasmid (pSVS dhfr) encoding the pre-S region and the S gene of human hepatitis B virus (HBV) and murine dihydrofolate reductase (DHFR) cDNA [complementary DNA] was used for the transfection of Chinese hamster ovary (CHO) DHFR- cells. Selection of clones resistant to methotrexate has permitted amplification of HBV sequences and an increase in production of hepatitis B surface antigen (HBsAg). HBV-specific transcripts were characterized. The HBsAg 22-nm particles contain a receptor for polymerized human serum albumin (pHSA) and elicit in animals the synthesis of antireceptor antibodies. This property is ascribed to a 34,000-dalton polypeptide in the particles, which is most likely encoded by the S gene and part of the pre-S region. Especially because the pHSA receptor is most abundantly present on the virion and because, in hepatitis B infection, the appearance of anti-pHSA receptor antibodies seems to be a highly reliable criterion for viral clearance, the HBsAg particles obtained may constitute a particularly efficient vaccine.