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.
Highlights
Helicobacter pylori is a spiral shaped microaerophilic bacterium that colonizes gastric mucosa of more than half of the world’s population and is associated with development of complications such as peptic ulcer disease, gastric carcinoma and mucosa associated lymphoid tissue lymphoma.[1]
Among 31 H. pylori positive cases, 19(61.3%) were cagA gene positive including 55%(11/20) of gastritis cases, 66.7%(2/3) of gastric ulcer cases, 66.7%(4/6) of duodenal ulcer cases and 100%(2/2) gastric carcinoma cases. cagA gene is significantly associated with duodenal ulcer cases (p=˂0.05)
As large numbers of populations in Bangladesh are seropositive for H. pylori so, the present study was done to detect the number and pattern of H. pylori cagA EPIYA motifs using PCR based typing and sequencing analysis to identify the H. pylori infected patients who are at risk to develop gastric carcinoma
Summary
Helicobacter pylori is a spiral shaped microaerophilic bacterium that colonizes gastric mucosa of more than half of the world’s population and is associated with development of complications such as peptic ulcer disease, gastric carcinoma and mucosa associated lymphoid tissue lymphoma.[1]. Bangladesh is a developing country and epidemiological studies shown 92% adult population were seropositive for H. pylori.[2]. Helicobacter pylori strains can be divided into two major types based on their ability to produce a 120–145kDa immune-dominant protein called cytotoxin associated gene A (CagA) antigen.[3] H. pylori strains possessing the CagA gene were linked with an increased risk of developing gastric cancer and peptic ulcer. The risk of developing gastric cancer in H. pylori infected CagA-positive subjects is six fold higher than that in CagA-negative subjects.[4] More than 90% of isolated strains from East Asia including Korea, Japan, and China are known to harbor cagA, while 50%-60% of isolated strains from Western countries are positive for it.[5]
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