Serum CagA antibodies in asymptomatic subjects and patients with peptic ulcer: Lack of correlation of IgG antibody in patients with peptic ulcer or asymptomatic Helicobacter pylori gastritis

Aim/background - Several studies have suggested that Helicobacter pylori which express CagA may be more virulent than those that do not, but limited populations have been studied to date. The aim of this study was to confirm and extend the association of CagA positive H pylori strains in a different geographical area and to a large, well defined patient population. Method - A validated ELISA for serum IgG to CagA was used to investigate the prevalence of CagA seropositivity in 100 patients with peptic ulcer compared with 77 with H pylori infection without ulcer disease in a North American population. The extent of antral and corpus inflammation and H pylori density in relation to CagA seropositivity in 40 subjects with H pylori infection were assessed semiquanitatively. All studies were carried out in a coded and blinded manner. Results - The prevalence of serum IgG CagA antibodies was higher in H pylori infected patients with ulcer (59%) compared with healthy H pylori infected volunteers (44%), but the difference was not significant. In contrast, the titre of serum IgG anti-CagA antibodies was higher among the seropositive subjects without ulcer disease, but again the difference was not significant. Comparison of histological features between asymptomatic individuals with H pylori infection in relation to CagA IgG antibody status revealed no differences in infiltration with acute inflammatory cells, H pylori density, or gastritis index. There was no relation evident between the degree of polymorphonuclear cell infiltration and the serum IgG antibody titre to CagA. Mononuclear cell infiltration in the antrum, but not the corpus, was greater in those with CagA IgG compared with those without (median score 5 v 3). Conclusions - A tight association between the presence or titre of serum IgG to CagA and peptic ulcer disease, greater H pylori density or infiltration of the mucosa with acute inflammatory cells could not confirmed in a North American population. Perhaps geographical differences in the prevalence of circulating H pylori strains are responsible for the discrepant results reported.