Serum Helicobacter pylori CagA antibody titer as a useful marker for advanced inflammation in the stomach in Japan

Background and AimSubjects infected with Helicobacter pylori containing cagA do not always induce serum CagA antibody. Our previous meta-analysis showed that serum CagA seropositivity was associated with gastric cancer even in East Asian countries. However, it remains unclear why serum CagA-positive status is associated with gastric cancer. In this study, we aimed to examine the relationship between anti-CagA antibody titer and the levels of pepsinogen (PG), and histological score. MethodsEighty-eight H.pylori-positive Japanese patients with gastritis were included. Serum CagA antibody titer, PG I, and PG II were evaluated by ELISA. Histological scores were evaluated according to Update Sydney System. CagA expression was examined by immunoblot. ResultsSeroprevalence of CagA antibody was found in 75.0%. Interestingly, serum CagA antibody titer was significantly correlated with PG I and PG II levels (P=0.003 and 0.004, respectively). Serum CagA antibody titer was also significantly correlated with mucosal inflammation in the corpus (P=0.04). On the other hand, bacterial density was not related with CagA antibody titer. CagA expression level of the strains was irrespective of the status of PG and serum CagA antibody. ConclusionsSubjects with higher serum CagA antibody titer can be considered as high-risk population for the development of gastric cancer from the point of strong gastric inflammatory response even in Japan. Host recognition rather than bacterial colonization might be associated with the difference of serum CagA antibody titer.