Immune response to a recombinant fragment of the CagA protein of Helicobacter pylori in blood donors and patients with gastric cancer: relation to ABO(H) blood group phenotype, stage of the disease and tumor morphology.

IgG immune response to CagA was evaluated by enzyme-linked imunosorbent assay (ELISA) using a recombinant fragment of CagA as antigen in 171 patients with gastric cancer and 298 blood donors to determine whether it could be related to the ABO(H) blood group phenotype, stage of cancer or tumor morphology. The CagA-ELISA showed a good specificity (93.5%) and sensitivity (88.5%) as compared with immunoblotting for blot CagA-negative and -positive donors. The Helicobacter pylori seropositive blood group A donors revealed the lowest proportion (37.6%) of strong responders to CagA: A<O (51.2%)<B (56.9%)<AB (62.5%). The proportion of strong responders to CagA was significantly lower among the H. pylori-seropositive patients with non-cardial cancer (35.4%) than in donors (48.8%). A significant suppression of immune response to CagA was found in the patients with advanced cancer. The proportion of CagA strong responders was higher at the first stage of gastric cancer in only blood group O and A individuals as compared with related controls. The overall CagA seroprevalence was not influenced by tumor histology. Thus, the IgG immune response to CagA is dependent on the ABO(H) blood group phenotype of the host and the stage of cancer. The host-dependent differences in the immune response to CagA may be more pronounced than those related to the putative disease-specific features of the H. pylori infection.