Helicobacter pylori cagA gene Polymorphism in Patients with Gastroduodenal Diseases

Abstract

Helicobacter pylori is a genetically diverse bacterial pathogen and its CagA gene is a major virulence factor that plays an important role in gastroduodenal pathologies. The biological function of cagA depends on tyrosine phosphorylation within the EPIYA (Glutamate-Proline-Isoleucine-Tyrosine-Alanine) motifs at the C-terminal region of the protein. This region may undergo polymorphism to give different types of EPIYA motifs. EPIYA motif diversity may provide a useful tool for prediction of H. pylori pathogenic activity and accurate determination of number and type of cagA EPIYA motifs could identify the virulent H. pylori. The aim of this study was to detect H. pylori cagA gene and its polymorphism in endoscopic gastroduodenal biopsy specimen from patients with gastroduodenal diseases in Bangladesh. This cross sectional study was carried out in the Department of Microbiology & Immunology, Bangabandhu Sheikh Mujib Medical University and Center for Advanced Research in Sciences, University of Dhaka during the period from March 2014 to February 2015. Gastric biopsies were collected from 78 patients with gastritis, duodenal ulcer, gastric ulcer and gastric carcinoma. H. pylori was identified by rapid urease test and ureC gene PCR. Presence of cagA gene and number and pattern of cagA EPIYA motif were determined by PCR. DNA sequencing was carried out to confirm the PCR detection method of cagA EPIYA motif and to analyse their peptide sequence. Among 31(39.7%) H. pylori positive cases, 19 (61.3%) were cagA gene positive in 11(55%) gastritis, 4(66.7%) duodenal ulcer, 2(66.7%) gastric ulcer and 2(100%) gastric carcinoma. A significant association was found between cagA gene and duodenal ulcer (p=˂0.05). EPIYA motif of all H. pylori cagA positive cases showed Western type cagA EPIYA ABC. No East Asian EPIYA ABD motif was found. Majority of gastroduodenal cases (57.9%) had 3 copies of EPIYA (ABC type), 26.3% had 4 copies (ABCC type) while remaining 10.5% had AC and 5.2% AB type EPIYA motif. EPIYA ABC was found in 75% of duodenal ulcer followed by 54.5% of gastritis and 50% of both gastric ulcer and gastric carcinoma patients. EPIYA ABCC motif was found in 50% of gastric ulcer and gastric carcinoma patients. Most of the EPIYA motif was EPIYA ABC and some were ABCC which has the risk of developing gastric carcinoma.