Cloning, expression and identification of hpaA gene from a clinical isolate of Helicobacter pylori

Abstract

To clone Helicobacter pylori adhesin (hpaA) gene,to construct the expression vector of the gene and to identify immunogenicity of the fusion protein. The hpaA gene from a clinical isolate Y06 of H.pylori was amplified by high fidelity PCR. The nucleotide sequence of the target DNA amplification fragment was sequenced after T-A cloning. The expression vector pET32a with inserted hpaA gene was constructed. hpaA fusion protein was expressed in E.coli strain BL21DE3 induced by IPTG at different dosages. Western blot using antibody against whole cell of H.pylori as well as immunodiffusion assay using antiserum of rabbit against the fusion protein was applied to determine immunogenicity of the fusion protein. In comparison with the reported corresponding sequences, the homology of nucleotide sequence of the cloned hpaA gene was from 94.25% approximate, equals 97.32%, while the homology of its putative amino acid sequence was as high as 95.38% approximate, equals 98.46%. The expression output of HpaA fusion protein in pET32a-hpaA-BL21DE3 system was approximately 40% of the total bacterial proteins. HpaA fusion protein was able to combine with antibody against whole cell of H.pylori and induce rabbit to preduce high titer antibody after the animal was immunized with the protein. An expression system with high efficiency of H.pylori hpaA gene has been established successfully. The expressed HpaA fusion protein with satisfactory immunogenicity and immunoreactivity can be used as antigen in H.pylori vaccine.