Polymorphism of Helicobacter pylori′s cagA gene and EPIYA motifs in Changchun area of China / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the distribution of cytotoxin-associated gene A (cagA) of Helicobacter pylori (Hp) and the polymorphism of EPIYA motifs in patients with upper gastrointestinal diseases in Changchun area of China and to evaluate the association between EPYIA motifs patterns and gastrointestinal diseases.Methods Hp strains were isolated from clinical samples.Their cagA gene was analyzed by PCR and sequencing analysis.Nucleotide sequence of cagA gene was translated into amino acid sequence by using DNAMAN software,and then the amino acid sequence was imported into software MEGA6.0 for multiple comparisons and construction of a phylogenetic tree.Results A total of 60 Hp strains were isolated and identified from gastric mucosa specimens collected from 298 patients.Hp infection was not correlated with patient's age or sex (P>0.05).The isolation rate of Hp in peptic ulcer disease (PUD) group was higher than that in non-peptic ulcer dyspepsia (NUD) group (P<0.05).Of the 60 Hp strains,90% (54/60) carried cagA gene.Twenty-three out of 26 successfully sequenced strains (88.4%) were East Asian-type including 22 containing EPIYA-ABD motif and one containing EPIYA-ABBD motif.The other three strains (11.6%) were Western type including two carrying EPIYA-ABC motif and one carrying EPIYA-BC motif.Results of the phylogenetic tree showed that the sequences of cagA gene were clustered into two groups,East Asian-type and Western-type groups.East Asian-type strains caused no disease cluster of statistical significance.All Western-type Hp strains were isolated from patients with peptic ulcer disease (PUD).Four mutant Hp strains were detected in the PUD group and the amino acid mutations preferentially occurred in the EPIYA-B segment.Conclusion The positive rate of Hp cagA gene is 90% in this region.Its distribution is not related to the type of gastrointestinal diseases.EPIYA-ABD (84.6%,22/26) is the predominant EPIYA motif.The amino acid mutation of EPIYA-B segment is closely related to peptic ulcer disease.Neither significant change in the sequence of 3' region of Hp cagA gene nor regional difference is observed in those Hp strains circulating in Changchun area of China.