Analysis of the 3' Variable Region of Cytotoxin-Associated Gene A (<i>cagA</i>) in <i>Helicobacter pylori</i> Isolates in China

Abstract

Infection by the bacterium Helicobacter pylori is a putative cause of various gastric disorders, including gastric adenocarcinoma. Incident rates are associated with variants of the H . pylori virulence factor cytotoxin-associated gene A protein (CagA), encoded by the gene cagA . However, these variants have not been characterized in China, where gastric cancer is common. We investigated the diversity of CagA variants in H . pylori strains isolated from a Chinese population. The 3' variable region of cagA genes from 66 clinical isolates in China were amplified by polymerase chain reaction, sequenced, aligned, and analyzed. All 66 H . pylori strains were CagA-positive, of which 93.9% were East Asian type and the tyrosine phosphorylation motifs (TPMs) were EPIYA-ABD. The remainder was Western type, in which TPMs were EPIYA-ABC. Interestingly, two of sixty-two strains (3.2%) of the East Asian type were mutated into ESIYA-B, whereas all four Western type (100%) strains were mutated into EPIYT-B. Both of the two strains with Western-type CagA obtained from gastric cancer patients contained a distinguished mutation on the first residue following the EPIYA site in the EPIYA-A motif. The predominant CagA type in these H . pylori strains isolated from Chinese patients in China was East Asian, with TPMs EPIYA-ABD, and there existed mutations in both the East Asian and Western type CagA.