Distinct repeat motifs at the C-terminal region of CagA of Helicobacter pylori strains isolated from diseased patients and asymptomatic individuals in West Bengal, India

Seventy-seven H. pylori strains isolated from patients with various clinical statuses were used to characterize the C-ternimal polymorphic region of CagA. Our analysis showed that there is no correlation between the previously described CagA types and various disease outcomes in Indian context. Further analyses of different CagA structures revealed that the repeat units in the spacer sequences within the EPIYA motifs are actually more discrete than the previously proposed models of CagA variants.Our analyses suggest that EPIYA motifs as well as the spacer sequence units are present as distinct insertions and deletions, which possibly have arisen from extensive recombination events. Moreover, we have identified several new CagA types, which could not be typed by the existing systems and therefore, we have proposed a new typing system. We hypothesize that a cagA gene encoding higher number EPIYA motifs may perhaps have arisen from cagA genes that encode lesser EPIYA motifs by acquisition of DNA segments through recombination events.The gastric pathogen Helicobacter pylori chronically infect more than half of human population. Although most infections are asymptomatic, 10-15？% of the H. pylori infected individuals develop chronic inflammation leading to atrophic gastritis, peptic ulcer as well as gastric adenocarcinoma [1,2].This pathogen was classified as a type I carcinogen by the World Health Organization in 1994. However, specific traits that enable a small proportion of this genetically diverse bacterium in the pathogenesis are poorly understood. Early studies showed that human convalescent sera collected from diseased patients significantly respond to a high molecular weight immunodominant bacterial protein known as CagA [3-5]. Subsequently, it was found that in western countries, H. pylori strains that express CagA and specific vacuolating cytotoxin (VacA) subtypes are significantly associated with the diseases [6-10]. Interestingly, the expression of these viru