Efficient expression and characterization of hepatitis B virus preS2 antigen in Escherichia coli

The complete (encoding 55 amino acids, aa) or partial (encoding aa 1-26) pr eS2 region gene of hepatitis B virus (HBV) was fused to the 3'-end of gluta thion-S-transferase (GST) gene and expressed under the control of the induc ible tac promoter in Escherichia coli at 37 degrees C. The fusion protein w ith the complete preS2 region was moderately expressed (8%) while the prote in with the N-terminal 26 aa was expressed at a higher level, yielding abou t 20% of the total cellular proteins. The GST-preS2 (aa 1-26) protein, whic h contains the immunodominant epitope, was produced form the soluble protei n fraction of the recombinant bacteria and purified by affinity chromatogra phy using glutathione-agarose column. The purified preS2 fusion protein sho wed the antigenicity of preS2, as assessed by indirect and competitive ELIS As.