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Background: H.pylori is one of the most common chronic bacterial infections in population so more than 85 percent are infected in Iran. H.pylori can cause different gastrointestinal disease like gastritis, peptic ulcers and even cancer. One of the effective factors in pathogenesis of bacteria is cytotoxin associated with gene A (cagA). Strains with cagA gene are more virulent. The aim of this study was to determine the frequency of cagA gene of H.pylori in patients with gastric disorders who were admitted to Imam Hossein Hospital, Tehran. Materials and Methods: In this descriptive study, DNA was extracted from 84 paraffin- embedded tissues using QiaAmp tissue kit. H.pylori was verified with PCR of 16sRNA sequences specific for Helicobacter spices and cagA gene was determined using specific primer by the PCR method. The prevalence of cagA gene in three clinical groups gastritis, gastric ulcer, and atrophic patients was compared. Results: Among 84 H.pylori positive isolates ,72 biopsy samples were positive for 16sRNA (85.7%) and 46 (63.9%) for cagA. The prevalence of cagA positive strains in peptic ulcer patients (43.5%) was greater than in those with gastritis (30%). Conclusion: Results showed that Helicobacter pylori strains with cagA are more common in patients with peptic ulcer and cancer.

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Background: Helicobacter pylori (H. pylori) is a gram negative bacilli that causes the stomach and duodenum diseases in human. An important virulence factor of H. pylori is a CagA gene that increases of colonization it in stomach epithelial cells and lead to inflammation and peptic ulcers. The aim of the present study was to production of recombinant protein containing highly antigenic region of CagA in E. coli.

Materials and Methods: In this experimental study, the antigenic region (1245 base pair) of CagA gene was detected by bioinformatics methods, proliferated by PCR method, digested by BamHI and XhoI restriction enzymes and cloned into pET32a plasmid and was expressed in the E. coli BL21 (DE3) pLysS with induced by IPTG. The expressed protein was purified with Ni-NTA kit and its antigenicity was studied by western blotting method.

Results: Data showed the successful cloning and expression of the target gene. Recombinant CagA protein purified by Ni-NTA kit and dialysis with concentration of 1.5 mg/ml. In western blotting, the produced protein was interacted with infected human and mice sera.

Conclusion: Results indicated that recombinant CagA protein (65 KDa) maintains its antigenicity, so could be used for serological diagnosis of H. pylori diseases and production of vaccine.