Different cagA and vacA Polymorphisms are Found in the Chinese versus the Malay and Indian Populations: An Analysis of Helicobacter Pylori Virulence Genes in Singapore

Abstract

Aim: Helicobacter pylori causes peptic ulcer disease and gastric cancer. Western studies suggest that polymorphisms in the virulence factors cagA and vacA may determine the ability of bacteria to cause gastroduodenal diseases. Differences in the cagA EPIYA motifs and polymorphisms of the signal (s), middle (m) and intermediate (i) regions of vacA are thought to be important. The aim of this study was to compare the polymorphisms of cagA and vacA of H. pylori isolated from the Chinese, Malay and Indian populations living in Singapore. Method: A total of 104 H. pylori isolates obtained from patients with dyspeptic symptoms were analysed. Of the 104 patients, 80 were Chinese, 9 Malays and 15 Indians. DNA was extracted from the isolates and the vacA allelic types and cagA EPIYA motifs were determined by polymerase chain reaction (PCR) and sequencing, respectively. Results: Differences in the vacA and cagA polymorphisms were found between the Chinese, Malays and Indians. Significantly more non-Chinese patients carried vacA s1/m1 strains versus Chinese patients ( p < 0.05). All 9 Malay patients, 11/15 (73.3%) Indians and 31/80 (38.8%) Chinese patients carried H. pylori strains with the vacA s1/m1/i1. Significantly more Chinese patients carried isolates with East Asian cagA EPIYA motifs versus non-Chinese patients ( p < 0.05). 79/80 (98.8%) of the Chinese isolates, 2/15 (13%) of Indian isolates, and 5/9(55.6%) of Malay isolates possessed CagA with the East Asian ABD type motif. Conclusion: Results from the current study demonstrated marked differences in the polymorphisms of vacA and CagA EPIYA motifs in strains isolated from Chinese versus non-Chinese patients. Epidemiologically, the Chinese are at the highest risk of developing gastric cancer. Work is ongoing to determine if differences found in the CagA EPIYA motifs of isolates from the Chinese patients can contribute to a subject's risk of developing gastric cancer.