Abstract: Objective To construct the prokaryotic recombinant plasmids carring truncated HBcAg gene, whole-length HBcAg gene and HBc-HBsAg fusion gene,and to observe the expression of target proteins in E.coli and their immunogenicity in vitro. Methods Truncated HBcAg gene,whole-length HBcAg gene and HBc-HBsAg fusion gene were obtained from plasmid pUCmT-HBV containing whole-length HBV gene（subtype adr）and construct recombinant plasmids of pSK-HBs,pSK-HBc and pKS-HBV C. Truncated HBcAg gene,whole-length HBcAg gene and HBc-HBsAg fusion gene which were obtained by fusing truncated HBsAg and truncated HBcAg gene,were subcloned into a expression vector pET-30a respectively after confirmed by DNA sequencing. The gene products were expressed in E.coli BL21（DE3） and identified by SDS-PAGE and Western blot. Results The prokaryotic expression plasmids expressing truncated HBcAg gene,whole-length HBcAg gene and HBc-HBsAg fusion gene were successfully constructed. High levels of HBcAg protein and HBc-HBsAg fusion protein were observed in E.coli BL21（DE3） and their immunogenicity were confirmed by Western blot. Conclusion HBcAg protein and HBc-HBsAg fusion protein are successfully obtained by selected expressing vector in E.coli BL21（DE3） and the gene products have immunogenicity. This study has provided an experimental basis for specific immunotherapy for chronic hepatitis B.

Key words: Hepatitis B virus, Hepatitis B surface antigen, Hepatitis B core antigen, Fusion protein, Prokaryotic expression plasmid