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

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) (n=83) and non-ulcer dyspepsia (NUD) patients (n=57) 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 3' 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 (P=0.001, odds ratio=4.26, confidence interval=1.60-11.74). 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

Attenuation of Helicobacter pylori-induced gastric inflammation by prior cag− strain (AM1) infection in C57BL/6 mice

Helicobacter pylori, colonize in stomach of ~50% of the world population. cag pathogenicity Island of H. pylori is one of the important virulent factors that attributed to gastric inflammation. Coinfection with H. pylori strain with different genetic makeup alters the degree of pathogenicity and susceptibility towards antibiotics. The present study investigates host immunomodulatory effects of H. pylori infection by both cag+ strain (SS1) and cag− strain (AM1). C57BL/6 mice were infected with AM1 or SS1 strain as well as AM1 followed by SS1 (AM1/SS1) and vice versa. Results: Mice infected with AM1/SS1 strain exhibited less gastric inflammation and reduced proMMP9 and proMMP3 activities in gastric tissues as compared to SS1/SS1 and SS1/AM1 infected groups. The expression of both MMP9 and MMP3 followed similar trend like activity in infected tissues. Both Th1 and Th17 responses were induced by SS1 strain more profoundly than AM1 strain infection which induced solely Th1 response in spleen and gastric tissues. Moreover, IFN-γ, TNF-α, IL-1β and IL-12 were significantly downregulated in mice spleen and gastric tissues infected by AM1/SS1 compared to SS1/SS1 but not with SS1/AM1 coinfection. Surprisingly, IL-17 level was dampened significantly in AM1/ SS1 compared to SS1/AM1 coinfected groups. Furthermore, number of Foxp3+ T-regulatory (Treg) cells and immunosuppressive cytokines like IL-10 and TGF-β were reduced in AM1/SS1 compared to SS1/SS1 and SS1/AM1 coinfected mice gastric tissues. Conclusions: These data suggested that prior H. pylori cag− strain infection attenuated the severity of gastric pathology induced by subsequent cag+ strain in C57BL/6 mice. Prior AM1 infection induced Th1 cytokine IFN-γ, which reduced the Th17 response induced by subsequent SS1 infection. The reduced gastritis in AM1/SS1-infected mice might also be due to enrichment of AM1- primed Treg cells in the gastric compartment which inhibit Th1 and Th17 responses to subsequent SS1 infection. In summary, prior infection by non-virulent H. pylori strain (AM1) causes reduction of subsequent virulent strain (SS1) infection by regulation of inflammatory cytokines and MMPs expressio

Comparative Transcriptomics of H. pylori Strains AM5, SS1 and Their hpyAVIBM Deletion Mutants: Possible Roles of Cytosine Methylation

Helicobacter pylori is an important human pathogen and one of the most successful chronic colonizers of the human body. H. pylori uses diverse mechanisms to modulate its interaction with the host in order to promote chronic infection and overcome host immune response. Restriction-modification genes are a major part of strain-specific genes present in H. pylori. The role of N-6 -adenine methylation in bacterial gene regulation and virulence is well established but not much is known about the effect of C-5 -cytosine methylation on gene expression in prokaryotes. In this study, it was observed by microarray analysis and RT-PCR, that deletion of an orphan C-5 -cytosine methyltransferase, hpyAVIBM in H. pylori strains AM5and SS1 has a significant effect on the expression of number of genes belonging to motility, adhesion and virulence. AM Delta DhpyAVIBM mutant strain has a different LPS profile and is able to induce high IL-8 production compared to wild-type. hpyAVIBM from strain 26695 is able to complement mutant SS1 and AM5 strains. This study highlights a possible significance of cytosine methylation in the physiology of H. pylori

Natural transformation efficiency of <i>H. pylori</i> strains AM5 and SS1 and their respective <i>hpyAVIBM</i> deletion mutant strains.

<p>Values are calculated as transformants/cfu/mg DNA. P<0.0001.</p

Survival of a pathogen in host depends upon its ability to modulate the balance between virulence and avirulence.

<p>Survival of a pathogen in host depends upon its ability to modulate the balance between virulence and avirulence.</p

Comparative transcriptomics of <i>H. pylori</i> wild type vs <i>hpyAVIBM</i> deletion mutant of strains AM5 and SS1.

<p>The genes listed are either down- or up-regulated in the <i>hpyAVIBM deletion</i> mutant of <i>H. pylori</i> strains AM5 and SS1. The identity of each gene is indicated by the Locus name as annotated in the <i>H. pylori</i> strain 26695 genome. The average ratio presented is the mean of mutant/wt ratio. P value <0.005.</p><p>ND: not determined.</p><p>- : not significant.</p

<i>hpyAVIBM</i> deletion enhances IL-8 production in AGS cell lines.

<p>(1) <i>H. pylori</i> strain AM5/SS1 (2) <i>H. pylori</i> strain AM5<i>ΔhpyAVIBM/</i>SS1<i>ΔhpyAVIBM</i> (3) <i>hpyAVIBM</i> deletion mutant AM5/SS1 complemented with <i>hpyAVIBM</i> from strain 26695.</p

LPS profiles of <i>hpyAVIBM</i> deletion mutant and wild-type strains.

<p>Lane 1: wild-type strain AM5, lane 2: <i>hpyAVIBM</i> deletion mutant AM5 complemented with <i>hpyAVIBM</i> from strain 26695, lane 3: <i>hpyAVIBM</i> deletion mutant. * highlights the bands different between wild type and mutant.</p