Prevalence of CagA-bearing Helicobacter pylori strains detected by the anti-CagA assay in patients with peptic ulcer disease and in controls.

Cytotoxin-associated gene (CagA)-bearing Helicobacter pylori strains have been associated with significant gastroduodenal pathologies. We have performed a study to evaluate the prevalence of CagA-bearing strains in a group of H. pylori-positive peptic ulcer disease and non-ulcer dyspepsia (NUD) patients, and healthy asymptomatic controls. Two hundred ninety-seven peptic ulcer disease, 45 NUD subjects, and 200 asymptomatic controls were studied. The newly developed anti-CagA antibody assay was used for the purpose of this study. The assay was performed by a conventional three-step enzyme-linked immunosorbent assay (ELISA) to detect the concentration of anti-CagA antibody present in the tested sera against the recombinant CagA 17/12 fusion protein. The final results were expressed with reference to a standard curve constructed from pooled CagA+ sera. Anti-CagA antibody assay reproducibility was assessed by intraplate and interplate variations. The mean intraplate and interplate variations were 8.0% and 11.2%, respectively. Anti-CagA antibody was present in 165/197 (84%) duodenal ulcer disease, 80/100 (80%) gastric ulcer disease, 25/45 (55.6%) NUD subjects, and 29/100 (29%) asymptomatic controls. The ulcer disease subjects were significantly more likely than the NUD subjects and the asymptomatic controls to have a positive anti-CagA antibody assay ( p < 0.005 and p < 0.001, respectively). Moreover, the NUD subjects were more likely to be anti-CagA+ antibody than the asymptomatic controls (p < 0.005). This newly developed anti-CagA antibody assay was highly reproducible. Anti-CagA antibody positivity was present in a significantly higher percentage of peptic ulcer disease subjects than in non-ulcer and asymptomatic healthy controls. Thus, anti-CagA antibody can be used as a clinical marker for peptic ulceration.