Pathogenetic role of the tyrosine-phosphorylated CagA EPIYA sequence of Helicobacter pylori in histological gastritis in Japanese patients

Helicobacter pylori (H. pylori) CagA protein plays an important role in the clinical outcome of gastritis treatment. Tyrosine phosphorylated Glu-Pro-Ile-Tyr-Ala motif in CagA (CagA-P) plays a critical role in the morphological transformation of cells. We examine the relationship between serum titer of anti-CagA-P antibody and gastric inflammation as well as the status of the CagA-P expression in gastric mucosa. Fasting sera from 127 dyspeptic patients were collected, and anti-CagA-P antibody was evaluated. Gastric biopsy specimens were collected and histological gastritis was evaluated. We investigate the expression of CagA-P in human gastric mucosa by Western blotting and immunohistochemistry. The titers of anti-CagA-P antibodies in the sera of H. pylori (+) patients were significantly higher than those of H. pylori (-) patients (P < 0.001). In 107 H. pylori (+) patients, anti-CagA-P titer was statistically higher in patients with high gastritis scores in the corpus than in those with low scores (P < 0.05). CagA-P expression was detected in the foveolar epithelium of the H. pylori infected gastric mucosa. CagA-P is an antigen-peptide against the host, and serum titer of anti-CagA-P antibody may be a new marker for gastritis in the corpus.