High expression of HBV S gene in Bombyx mori cell culture and in silkworms.

The coding sequence of human hepatitis B virus (HBV) subtype adr surface antigen S gene was inserted into the genome of the nuclear polyhedrosis virus of Bombyx mori (BmNPV) under control of the polyhedrin promoter, and a recombinant BmNPVS virus was constructed. Upon infection of the recombinant virus, the yield of HBsAg was 35.5 micrograms per 10(6) cells, 750 micrograms per larva, and 690 micrograms per pupa. Western blot and electron microscope observation of the preliminary purified HBsAg particles showed that they were well glycosylated and assembled as regular 22-nm (diameter) particles. The CsCl buoyant density was 1.2 g/mL, which is consistent with that of HBsAg in the blood of patients.