Abstract
Using an adenovirus-hepatitis B virus (HBV) recombinant, expression of the HBV surface antigen (HBsAg) genes was examined in various cell lines using S1 nuclease mapping and radioimmunoassay. The steady-state level of the 2·4 kb RNA encoding the large HBsAg was much greater than, or the same as, that of the 2.0 kb RNA, encoding the middle and major HBsAgs, in primate cells, but was negligible in non-primate cells, as is the case in most expression systems. According to the amount of 2·4 kb RNA expressed, cells were classified into three groups: those in which (1) the amount of 2·4 kb RNA was much greater than that of 2·0 kb RNA (HepG2 and JHH-4), (2) the amount of 2·4 kb RNA was the same as that of 2·0 kb (Hul-1, HeLa and other non-hepatic primate cells), and (3) the amount of 2·4 kb RNA was less than one-tenth of that of 2·0 kb RNA (rodent cells). Radioimmunoassay revealed that most HBsAg is located intracellularly in primate cells, but is secreted into the culture medium of rodent cells. The expression of 2·4 kb RNA was unaffected by an inhibitor of DNA synthesis in HepG2 cells, which are of human liver origin, whereas it was strongly inhibited in human non-hepatic HeLa cells.
† Present address: Third Department of Internal Medicine, Ehime University, School of Medicine, Shigenobu-Cho, Onsen-gun, Ehime 791-02, Japan.