A novel diagnostic monoclonal antibody specific for Helicobacter pylori CagA of East Asian type.

Molecular biological and epidemiological studies have suggested that Helicobacter pylori producing East Asian CagA protein variant is more virulent than that producing Western CagA. In the present study, we developed and validated an enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody specifically recognizing East Asian CagA-positive H. pylori. A total of 32 H. pylori strains were tested and the data were subjected to receiver-operator characteristic (ROC) curve analysis. The accuracy of the test, determined by calculating the area under the curve, was 0.96, which indicated a high level of accuracy. At the ROC optimized cutoff, the sensitivity and specificity of our ELISA method were 88.0% and 100%, respectively. The validated ELISA showed good performance in terms of sensitivity and specificity. These results suggest that this test is suitable for the diagnostic detection of East Asian CagA carrying strains. We also analyzed the localization of the CagA protein in H. pylori-infected gastric mucosa with fluorescence immunohistochemistry, and found that CagA protein expression was up-regulated by adhesion to epithelial cells.