Development of an arCagA Antigen-Based Assay for the Detection of Helicobacter pylori in Stool Specimens

Background: Helicobacter pylori infection can lead to the development of gastritis and peptic ulcer in humans. Two categories of diagnostic methods are generally used for the detection of H. pylori infection. Particularly, non-invasive methods are recognized as practical, feasible, and sensitive diagnostic tests for the detection of H. pylori infection. Objectives: This study was designed with the aim to develop an assay, based on cytotoxin-associated gene A (CagA) antigen through western blotting method for the detection of H. pylori in fecal samples. Methods: The antigenic region of CagA (arCagA) gene was amplified by polymerase chain reaction (PCR) method and cloned to pET32a plasmid. Isopropyl β-D-1-thiogalactopyranoside (IPTG) was used to induce gene expression, and Escherichia coli BL21 (DE3) pLysS was transformed into pET32a-arCagA. Afterwards, the recombinant protein was purified by Ni-NTA resin. The rats were immunized by the purified arCagA protein for the production of antibodies. For the detection of H. pylori infection, stool samples from 80 patients were evaluated, using Western blot analysis and rat anti-arCagA antibody. The antigenic recombinant CagA region was expressed in E. coli, and CagA protein was produced and purified. Rat anti-CagA antibody was produced after immunization with the recombinant antigenic protein. Results: We investigated CagA protein, using the immunoblotting method in stool samples, which were already identified as positive by the application of a commercial kit. The developed test showed sensitivity of 87% and specificity of 90% in the patients. Conclusions: Based on the findings, application of recombinant arCagA antigen for the detection of H. pylori infection is a simple, rapid, and brief non-invasive method. Therefore, it can be suggested as an appropriate antigen for H. pylori detection kits.