Significant association of the dupA gene of Helicobacter pylori with duodenal ulcer development in a South-east Indian population

Abstract

A novel virulence factor, duodenal ulcer-promoting gene A (dupA), in Helicobacter pylori has been found to be associated with disease in certain populations but not in others. This study analysed a South-east Indian population as part of the debate about the relevance of dupA for the prediction of clinical outcomes. A total of 140 H. pylori strains isolated from duodenal ulcer (DU) (n583) and non-ulcer dyspepsia (NUD) patients (n557) were screened by PCR and dot-blot hybridization to determine the presence of the ORFs jhp0917 and jhp0918. Part of jhp0917-jhp0918 was sequenced to search for the C/T insertion that characterizes dupA and the levels of dupA transcripts were also assessed. The PCR and dot-blot results indicated the presence of jhp0917 and jhp0918 in 37.3 % (31/83) and 12.2 % (7/57) of H. pylori strains isolated from DU and NUD patients, respectively. Sequencing analysis showed insertion of a C at nt 1386 in the 39 region of jhp0917, forming the dupA gene in 35 strains. RT-PCR analysis detected the dupA transcript in 28 of these 35 strains. The expression level of the dupA transcript varied from strain to strain, as shown by real-time PCR. The results demonstrated that analysis based on PCR only for dupA may produce an erroneous interpretation. The prevalence of dupA was significantly greater among strains isolated from patients with DU than from patients with NUD in this population (P50.001, odds ratio54.26, confidence interval51. 60-11.74). Based on these findings, dupA can be considered a biomarker for DU patients in India. The reported discrepancies for this putative virulence marker in different populations may be due to the genome plasticity of H. pylori. INTRODUCTIONHelicobacter pylori is a Gram-negative, spiral pathogen that infects .50 % of the world's population (Brown, 2000). Infection with H. pylori plays an important role in the development of peptic ulcer disease, distal gastric carcinoma (GC) and gastric mucosa-associated lymphoid tissue lymphoma (Mégraud & Lamouliatte, 1992;Parsonnet et al., 1991;Wotherspoon et al., 1991). In India,~65-70 % of the population are infected with H. pylori (Graham et al., 1991;Singh et al., 2002). Overall, 15-20 % of infected patients develop gastric or duodenal ulcer (DU) and ,1 % develop gastric adenocarcinoma. H. pylori infection is more prevalent in developing countries, and its incidence is decreasing in western countries (Czinn, 2005). The decisive factor(s) in H. pylori-mediated infection is still unclear. However, involvement of several virulence factors of the bacteria, host genetics and environmental influences are believed to determine the outcome of infection. Among the host factors, pro-inflammatory cytokine gene polymorphisms have been associated with DU and GC (El-Omar et al., 2000;Machado et al., 2001;Rocha et al., 2005 et al. (2010) showed that the presence of dupA is significantly associated with DU, whilst another systematic review confirmed that dupA is associated with gastroduodenal diseases (Hussein, 2010).There are also indications...

Antigenic Proteins of Helicobacter pylori of Potential Diagnostic Value

“…Helicobacter pylori is a gram negative, spiral-shaped, microaerophilic, flagellated slow-growing bacteria (Alam et al, 2012). It colonizes the apical side of human gastric epithelial cells and mucous layer (Benoit et al, 2004;Chambers et al, 2013).…”

A report on Allelic Variation in Helicobacter pylori dupA: A viewpoint

“…Many studies from different regions of the world have reported that the prevalence of dupA in DU patients was higher than gastric ulcer (GU) , but in studies on Swedish, Australian, Chinese, Indian and Malaysian populations, no association was observed between dupA and DU or GC development; this result is consistent with results from South America and East Asia (9, 11, 16-18, 20-23, 25, 29-34). In other studies from Belgium, South Africa, China and the United States, there were not only associations between dupA and duodenal ulcer disease, but also there were initiatives to the occurrence of gastric cancer (21,26,32,(35)(36)(37).…”

“…However, the accuracy of dupA as a practically useful biomarker, at least for duodenal ulcer (DU) patients, has attracted many types of research in recent years (15,17,(19)(20)(21)(22)(23). Unfortunately, contradictory results obtained from different studies have prevented clinicians and microbiologists from having a straight conclusion about the association of that factor with digestive diseases (9,11,13,(19)(20)(21)(24)(25)(26). DupA is homologous to virB4 and has been proposed as a component of a new cluster of vir homologue genes in the bacterial plasticity region (PR) that might form a type IV secretion system similar to cag pathogenicity island (PAI).…”

“…The primer binding site of the dupA gene was highly variable in the designed PCR and application of different sets of primers had a great impact on reporting diverse percentages of dupA-positive strains from different populations (9,10,14,17,19,21,23,24,(26)(27)(28). Many studies from different regions of the world have reported that the prevalence of dupA in DU patients was higher than gastric ulcer (GU) , but in studies on Swedish, Australian, Chinese, Indian and Malaysian populations, no association was observed between dupA and DU or GC development; this result is consistent with results from South America and East Asia (9, 11, 16-18, 20-23, 25, 29-34).…”

Biomarkers and diagnostic tools for detection of Helicobacter pylori

“…Helicobacter pylori infection is caused by a gram-negative organism that colonizes the mucous layers and the apical surface of human gastric epithelial cells (Alam et al 2012;Khalilpour et al 2014a). More than 90 % of population in developing and Eastern countries and half of the world population have been affected with H. pylori infection (Chan et al 2006a;Malaty 2007a).…”