AIM:To clone hpaA gene from a clinical strain of Helicobacterpylori and to construct the expression vector of the geneand to identify immunity of the fusion protein.METHODS:The hpaA gene from a clinical isolate Y06 of H.pyloriwas amplified by high fidelity PCR.The nucleotidesequence of the target DNA amplification fragment wassequenced after T-A cloning.The recombinant expressionvector inserted with hpaA gene was constructed.Theexpression of HpaA fusion protein in E.coli BL21DE3 inducedby IPTG at different dosages was examined by SDS-PAGE.Western blot with commercial antibody against whole cellof H.pylori as well as immunodiffusion assay with self-prepared rabbit antiserum against HpaA fusion protein wereapplied to determine immunity of the fusion protein.ELISAwas used to detect the antibody against HpaA in sera of125 patients infected with H.pyloriand to examine HpaAexpression of 109 clinical isolates of H.pylori.RESULTS:In comparison with the reported correspondingsequences,the homologies of nucleotide and putative aminoacid sequences of the cloned hpaA gene were from 94.25-97.32% and 95.38-98.46%,respectively.The output ofHpaA fusion protein in its expression system of pET32a-hpaA-BL21DE3 was approximately 40% of the total bacterialproteins.HpaA fusion protein was able to combine with thecommercial antibody against whole cell of H.pyloriand toinduce rabbit producing specific antiserum with 1:4immunodiffusion titer after the animal was immunized withthe fusion protein.81.6% of the serum samples from 125patients infected with H.pylori(102/125) were positive forHpaA antibody and all of the tested isolates of H.pylori(109/109) were detectable for HpaA.CONCLUSION:A prokaryotic expression system with highefficiency of H.pylorihpaA gene was successfully established.The HpaA expressing fusion protein showed satisfactoryimmunoreactivity and antigenicity.High frequencies of HpaAexpression in different H.pylori clinical strains and specificantibody production in H.pylori infected patients indicatethat HpaA is an excellent and ideal antigen for developingH.pylori vaccine. AIM: To clone hpaA gene from a clinical strain of Helicobacter pylori and to construct the expression vector of the gene and to identify immunity of the fusion protein. METHODS: The hpaA gene from a clinical isolate Y06 of H. pylori was amplified by high fidelity PCR. nucleotide sequence of the target DNA amplification fragment was sequenced after TA cloning. The recombinant expression vector inserted with hpaA gene was constructed. The expression of HpaA fusion protein in E. coli BL21 DE3 induced by IPTG at different dosages was examined by SDS-PAGE. Western blot with commercial antibody against whole cell of H. pylori as well as immunodiffusion assay with self-prepared rabbit antiserum against HpaA fusion protein wereapplied to determine immunity of the fusion protein. ELISA was used to detect the antibody against HpaA in sera of 125 patients infected with H. pylorind to examine HpaAexpression of 109 clinical isolates of H.pylori.RESULTS: In contrast with the corresponding corresponding sequences, the homol ogies of nucleotide and putative aminoacid sequences of the cloned hpaA gene were from 94.25-97.32% and 95.38-98.46%, respectively. The output of HpaA fusion protein in its expression system of pET32a-hpaA-BL21DE3 was approximately 40% of the total bacterial proteins. HpaA fusion protein was able to combine with the commercial antibody against whole cell of H. pylorind toinduce rabbit producing specific antiserum with 1: 4 immunodiffusion titer after the animal was immunized with the fusion protein. 81.6% of the serum samples from 125patients infected with H. pylori 102/125) were positive for HpaA antibody and all of the tested isolates of H. pylori (109/109) were detectable for HpaA.CONCLUSION: A prokaryotic expression system with highefficiency of H. pylori hpaA gene was successfully established. The HpaA expressing fusion protein showed satisfactory immunoreactivity and antigenicity. High frequencies of HpaAexpression in different H. pylori clinical strains and specific antibody production in H. pylori infected patients indicate that HpaA is an excellent and ideal antigen for developing H. pylori vaccine.