Gene fusion of cholera toxin B subunit and HBV PreS2 epitope and the antigenicity of fusion protein

A unique EcoRI site was introduced at the 3′ end of cholera toxin B subunit (CTB) gene by site-directed mutagenesis, polynucleotides encoding 120–145aa epitope of HBV PreS 2 were chemically synthesized and fused to the 3′ end of cholera toxin B subunit gene. The fused gene was over-expressed (about 30 μg ml −1) in E. coli, and more than 95% of the fusion protein was secreted into the medium. The fusion protein expressed was purified by affinity chromatography. The chimera protein obtained bound to ganglioside GM1, and had the antigenicity of both cholera toxin B subunit and HBV PreS2 as confirmed by ELISA. After mice were immunized intramuscularly with the fusion protein, anti-CTB antibody and anti-PreS2 antibody were produced. These results indicated that the fusion protein retained not only the biological function of CTB but also the antigenicity and the immunogenicity of cholera toxin B subunit and HBV PreS2 epitope. This work provided a sound basis for further studies on the construction of engineered peptide vaccine.