No 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.

Helicobacter pylori, the major cause of gastritis, peptic ulcer and gastric cancer, infects half of the world population, but only a few infections lead to serious disease. In order to investigate specific proteins related to the pathogenic difference of this bacterium, comparative proteome analyses of Helicobacter pylori C1 (isolated from patients with gastric cancer) and G1 (isolated from patients with gastritis) were performed using two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). Four proteins (inorganic pyrophosphatase, 3-oxoadipate CoA-transferase subunit B, translation elongation factor, and aldo-keto reductase) were found only in Helicobacter pylori C1, and one protein (alkyl hydroperoxide reductase) was found in G1. Additionally, different isoelectric points (pI) of Hsp60 were observed from the two strains. Then we cloned and sequenced Hsp60 genes from forty-nine Helicobacter pylori isolated from gastric cancer and gastritis. Gene sequencing showed that one C→G single nucleotide polymorphism occurred in the 1399th nucleotide of Hsp60. These results indicate that pathogenic differences exist in various Helicobacter pylori isolated from Chinese patients.