Impact of Helicobacter pylori infection on the humoral immune response to MUC1 peptide in patients with chronic gastric diseases and gastric cancer.

Many investigators have demonstrated alteration of gastric mucins in H. pylori infected individuals. The inflammatory environment induced by H. pylori leading to aberrant glycosylation of MUC1 and demasking of core peptide MUC1 epitope could enhance immune responses to MUC1. IgG and IgM immune response to MUC1 in patients with gastric cancer (n = 214) chronic gastroduodenal diseases (n = 160) and healthy blood donors (n = 91) was studied with ELISA using bovine serum albumin-MUC1 60-mer peptide as antigen. H. pylori serologic status was evaluated with ELISA and CagA status by immunoblotting. Gastric mucosa histology was scored according to the Sydney system. Compared to H. pylori seronegative individuals, higher levels of IgG antibody to MUC1 were found in H. pylori seropositive patients with benign gastric diseases (p < 0.01) and blood donors (p < 0.03). Higher MUC1 IgG antibody levels were associated with a higher degree of gastric corpus mucosa inflammation in patients with chronic gastroduodenal diseases (p < 0.0025). There was a positive correlation between the levels of anti-H. pylori IgG and MUC1 IgG antibody levels in blood donors (p = 0.03), and in patients with benign diseases (p < 0.0001). In patients with gastric cancer (n = 214) a significantly higher level of anti-MUC1 IgG than in blood donors was observed (p < 0.001) irrespective of H. pylori status or stage of cancer. MUC1 IgM antibody levels were not related to the H. pylori serology. IgG immune response to tumor-associated MUC1 is up regulated in H. pylori infected individuals. This increase is associated with a higher IgG immune response to H. pylori and with a higher degree of gastric mucosa inflammation. High levels of MUC1 IgG antibody irrespective of H. pylori serologic status characterized patients with gastric cancer. The findings suggest that, in some individuals, the H. pylori infection may stimulate immune response to tumor-associated MUC1 peptide antigen thus modulating tumor immunity.