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 ass ay (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 r elated to the ABO(H) blood group phenotype, stage of cancer or tumor morpho logy. The CagA-ELISA showed a good specificity (93.5%) and sensitivity (88. 5%) as compared with immunoblotting for blot CagA-negative and -positive do nors. The Helicobacter pylori seropositive blood group A donors revealed th e 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 significan tly lower among the H. pylori-seropositive patients with non-cardial cancer (35.4%) than in donors (48.8%). A significant suppression of immune respon se to CagA was found in the patients with advanced cancer. The proportion o f 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. Th e overall CagA seroprevalence was not influenced by tumor histology. Thus, the IgG immune response to CagA is dependent on the ABO(H) blood group phen otype of the host and the stage of cancer. The host-dependent differences i n the immune response to CagA may be more pronounced than those related to the putative disease-specific features of the H. pylori infection.