SEROLOGIC DETECTION OF INFECTION WITH CAGA(-PYLORI STRAINS() HELICOBACTER)

Approximately 60% of Helicobacter pylori isolates possess the cagA gen e and express its 120- to 140-kDa product (CagA). In this study, the c agA gene was detected in H. pylori isolates from 26 (81.3%) of 32 pati ents with duodenal ulcers (DU), 17 (68.0%) of 25 patients with gastric ulcers, and 23 (59.0%) of 39 patients with nonulcer dyspepsia (NUD), By Western blotting (immunoblotting) with antiserum to CagA, in vitro CagA expression was demonstrated for 95.5% of cagA(+) strains compared with 0% of strains lacking cagA. Sera from patients infected with cag A(+) strains (n = 66) reacted with recombinant CagA in an enzyme-linke d immunosorbent assay to a significantly greater extent than either se ra from patients infected with strains lacking cagA (n = 30) or sera f rom uninfected persons (n = 25) (P < 0.001), A strain lacking cagA was isolated from eight patients who had serum immunoglobulin G antibodie s to CagA, which suggests that these patients were infected with multi ple strains, Serum immunoglobulin G antibodies to CagA were present in 87.5, 76.0, and 56.4% of patients with DU, gastric ulcers, and NUD, r espectively (odds ratio, 5.41; 95% confidence interval, 1.44 to 24.72; P = 0.004 [DU versus NUD]), These data demonstrate an association bet ween infection with cagA(+) H, pylori and the presence of duodenal ulc eration and indicate that serologic testing is a sensitive method for detecting infection with cagA(+) strains.