Expression of overlapping PreS1 fragment recombinant proteins for the determination of immunogenic domains in HBsAg PreS1 region.

In this study, eight preS1 fragments overlapped in preS1 (21-119) region of HBV adr subtype, i.e. preS1 (21-47), preS1 (34-59), preS1 (48-70), preS1 (60-85), preS1 (71-94), preS1 (86-109), preS1 (95-119) and preS1 (21-119), were cloned by PCR, and expressed as GST fusion proteins. These GSTpreS1 fusion proteins were highly expressed in soluble form in E. coli, and about 50 to 90 mg soluble fusion proteins were purified from 1 L culture. Using these fusion proteins, the immunogenic domains in preS1 (21-119) region were identified by Western blot analysis and competitive ELISA. The results showed that the immunogenic domains mainly existed in preS1 (21-59) in N-terminus and preS1 (95-109) in C-terminus, and more importantly, a major immunogenic domain preS1 (34-59), which has much stronger immunogenicity, was identified. It was also supported by the predictions of secondary structure and immunological property in the preS1 (21-119) region. The results here would be helpful for the design of new vaccines against HBV.