Development of an in-house capture ELISA: An attempt to detect CagA antigen in sera of Helicobacter pylori infected patients

The CagA protein one of the key virulence factors of Helicobacter pylori plays an important role in the pathogenesis of peptic ulcer diseases. Unfortunately the cagA gene status can only be determined by PCR while serology is an alternative approach to detect antigens or antibodies. Our aim is to detect the CagA antigen in sera of infected subjects by the development of an in-house capture ELISA test. Gastric antral biopsies and serum samples were collected from 63 patients. PCR was used to determine the cagA status. Our previously developed recombinant CagA protein and monoclonal antibody were used for setting up the capture ELISA test. H. pylori positive [(38 gastritis, 14 duodenal ulcers (DU), 11 gastric ulcer (GU)] patients were determined by PCR. The cagA gene was detected in 21 (55%) of gastritis, 11 (78%) of DU and 7 (60%) of GU patients. The reagents used in setting up the capture ELISA test following optimization displayed high performance. This study showed that our developed in-house capture ELISA has the potential to detect the CagA antigen at very low concentrations even though not detected in our H. pylori infected patients sera but we are also intended to use it in saliva and stool samples.