Infection with CagA+ Helicobacter pylori strains as a possible predictor of risk in the development of gastric adenocarcinoma in Mexico.

Helicobacter pylori strains possessing the Cag pathogenicity island have been associated with increased gastric inflammation and with duodenal ulcer. In contrast, studies on the association of cagA+ H. pylori infections and gastric cancer have shown conflicting results. The aim of our study was to determine whether H. pylori and CagA status are associated with gastric cancer in Mexico. We selected serum samples from 3 geographic areas with gastric cancer mortality rates per 100,000 inhabitants of 2.5 (low risk), 4.5 (medium risk) and 6.4 (high risk). H. pylori infection was determined by the detection of antibodies to H. pylori whole cell antigen by an enzyme-linked immunosorbent assay (ELISA). To study the prevalence of infection with cagA+ strains, serum IgG antibodies to CagA were determined by ELISA using a recombinant CagA antigen. Of the 2,775 individuals studied, 1,931 were H. pylori seropositive and 1,710 had antibodies against CagA. The risk for gastric cancer in the 3 populations studied increased proportionally as infection with cagA+ strains increased (p < 0.001 for trend). H. pylori infection also showed association with gastric cancer (p < 0.05). Individuals seropositive for CagA, but seronegative for H. pylori whole cell antigen, were more frequent in areas with higher gastric cancer rates (p < 0.01). These results support the possible role of CagA(+) status as predictor of risk for gastric adenocarcinoma in Mexico; this is in agreement with results in European and American populations, but contrary to studies in some Asian countries.