A modified hepatitis B surface antigen carrying both preS1 and preS2 epitopes

The DNA fragments coding for preS2(120–146) and preS1(21–47) amplified by PCR were fused to both 5′ and 3′ ends of S gene at the position of amino acid 223. The fusion gene was placed downstream of the promoter P7.5 of the universal vaccinia viral vector pGJP-5 and the recombinant vaccinia virus vS2SSI was then selected by invivo homogeneous recombination. Fusion protein S2SS1 could be expressed in the mammalian cells infected with vS2SSl. The investigation of expression, secretion, antigenicity and particle assembly of the S2SS1 protein demonstrated that S2SS1 protein could be assembled into particles which presented preSl, preS2 and S antigenicity and be efficiently secreted from the cells. It also showed that the level of its expression and secretion approached to that of the S protein expressed by the recombinant vaccinia virus.