Expression, Purification and Evaluation of Antigenicity of CagA Antigenic Fragment of Helicobacter pylori

Abstract

Background: Helicobacter pylori is a human pathogen that causes chronic gastritis, which playsrole in gastric and duodenal ulcers, is also involved in gastric carcinogenesis and may be regarded as a possible important factor in at least a subset of patients with functional dyspepsia. Objectives: This study was aimed to construct a recombinant protein containing H. pylori antigenic CagA region and determine its antigenicity as a vaccine candidate against H. pylori. Materials and Methods: The antigenic region of CagA gene was detected by bioinformatics techniques. In this study, the H. pylori antigenic CagA region was amplified by PCR and sub-cloned to prokaryotic expression vector pET32a. Escherichia coli BL21 (DE3) pLysS was transformed with pET32a- CagA and gene expression was induced by IPTG. The expressed protein was purified by affinity chromatography using Ni-NTA resin. The integrity of the product was confirmed by western-blot analysis using Sera of infected individual. Finally antigenicity was studied by western-blot analysis using human sera infected with H. pylori. Results: Enzyme digestion analysis, PCR and sequencing showed that the target gene (1245 bp) was correctly inserted into the recombinant vector. The expressed protein was purified using affinity chromatography by Ni-NTA resin. The data also indicated that CagA protein from H. pylori detected from patients' sera. Conclusions: Results indicates that antigenic region of recombinant CagA protein were recognized as an antigen , so it might be a candidate for the development of H. pylori vaccine, ELISA kit designs and serological diagnosis of H. pylori infections.