Sequence Analysis of East Asian cagA of Helicobacter pylori Isolated from Asymptomatic Healthy Japanese and Thai Individuals

Abstract

CagA, especially East Asian type, is one of the most important virulence factors of Helicobacter pylori, which is believed to contribute to the gastric cancer development. There is extreme sequence heterogeneity on 3' region of cagA gene, demonstrated by the sequence analysis of cagA of H. pylori strains isolated from gastric disease patients. However, whether such heterogeneity of the cagA gene sequence is related to the pathogenicity of H. pylori in the gastric cancer development is not certain. Therefore, in this study, the 3' region of cagA sequences isolated from asymptomatic healthy individuals in Japan and Thailand, which show high and low gastric cancer prevalence, respectively, were analyzed and compared with those from patients with gastric cancer. The CagA sequences analysis in 21 and 12 H. pylori DNA samples obtained from Japanese and Thai individuals, respectively, by the molecular phylogenetic method showed that the sequences were more conserved in the Thai individuals (concordance rates among Thai sequences, 93.9-100%) than in the Japanese individuals (concordance rates among Japanese sequences, 82.8-100%) as shown by unrooted neighbor-joining (N-J) consensus trees constructed with the sequence between Asn869 and Ala967 in CagA. CagA sequences in gastric cancer patients were obtained from published data; analysis of these sequences revealed that CagA sequences from almost all Thai individuals were concentrated in one branch. In contrast, CagA sequences from Japanese individuals were uniformly distributed throughout the N-J consensus tree. These results suggest that the difference in the CagA sequences between asymptomatic healthy Japanese and Thai individuals may be linked to the incidence of gastric cancer in Japan and Thailand.

Elevated prevalence of Helicobacter species and virulence factors in opisthorchiasis and associated hepatobiliary disease

“…Discrete genotypes of cag A associate with severity of gastrointestinal diseases 48 . Unclassified type (AB type) represented the major cag A genotype in this study, in contrast with earlier reports indicating that AB represents only a minority genotype carried by otherwise healthy Thais 41 49 . Here, 22% of the cag A-encoded sequences were Western type (ABC type) with no East Asian type (ABD type), lower than reported for liver fluke infection-induced CCA 44 .…”

Phylogenetic analysis of Helicobacter pylori cagA gene of Turkish isolates and the association with gastric pathology

“…Mane et al [12] also studied the cagA gene of a strain isolated from an Amerindian subject and reported that there was a substantial divergence of that Amerindian strain from the Old World strains. Recently Hirai et al [13] studied the cagA 3′ region of isolates from asymptomatic healthy Japanese and Thai subjects and compared with those from patients with GC. They suggested that cagA sequence differences between those subjects might be linked to GC incidence in Japan and Thailand.…”