Duodenal ulcer promoting gene (dupA): skewing the immune response to Helicobacter pylori and hence disease pathogenesis
Lead Research Organisation:
University of Nottingham
Department Name: Sch of Biomedical Sciences
Abstract
Half the world‘s population is infected by the bacteria Helicobacter pylori (Hp), which survives in the human stomach. This is an important cause of ulcer disease and stomach cancer, though the majority of people who carry the bacteria are healthy. Different Hp strains have different genes, some of which are associated with disease and are called bacterial virulence factors. This project will help establish whether a new Hp virulence factor called dupA might explain why some people develop ulcers, specifically ulcers in the first part of the small bowel (duodenal ulcers). Hp strains with dupA may also protect people against developing cancer.
Most previously studied bacterial virulence factors have been found to affect the cells that make up the stomach wall. We think that dupA works on the cells of the immune system instead and so may change how a person‘s body fights the infection to predispose them to develop duodenal ulcers. We plan to collect small tissue samples from the stomach of patients having an endoscopy and study how the immune system responds in uninfected and infected patients.
We hope that this research will help us to more fully understand how Hp infection contributes to the development of ulcers.
Most previously studied bacterial virulence factors have been found to affect the cells that make up the stomach wall. We think that dupA works on the cells of the immune system instead and so may change how a person‘s body fights the infection to predispose them to develop duodenal ulcers. We plan to collect small tissue samples from the stomach of patients having an endoscopy and study how the immune system responds in uninfected and infected patients.
We hope that this research will help us to more fully understand how Hp infection contributes to the development of ulcers.
Technical Summary
Helicobacter pylori (Hp) colonises the stomachs of half the world‘s population and is the main cause of peptic ulcers and gastric carcinoma. Little is known of disease-specific bacterial factors that promote duodenal ulceration (DU). T-helper 1 (Th1) response in gastric mucosa is important in pathogenesis.
Duodenal ulcer promoting gene (dupA) is a novel Hp gene recently linked to the specific clinical outcome of DU and negatively associated with gastric carcinoma. dupA+ strains are associated with more intense antral neutrophil infiltration and higher antral IL-8 levels in vivo, giving biological plausibility to a role in DU pathogenesis. We have shown polymorphism at the dupA locus and that dupA is associated with an undescribed type IV secretion system, tentatively designated tfs4.
Our preliminary data using dupA disruption to explore phenotypes suggests that this virulence mechanism targets immune cells, in contrast to other Hp virulence factors which target epithelial cells. We found significantly higher Th1 cytokine levels, particularly IL-12, in mononuclear cell supernatants following culture with dupA+ strains than following culture with their dupA null mutants and dupA- strains. Disruption of other putative tfs4 components also significantly decreased IL-12 production. Flow cytometry suggested monocytes are an important source of this IL-12 in ex vivo specimens.
This study will investigate the immune response to dupA+ Hp strains in the human stomach and its role in pathogenesis.
Objectives
1. To characterise the cytokine response to dupA+ Hp strains in the human stomach, hypothesising that they are associated with a Th1 cytokine response with antral predominant inflammation in keeping with the pathophysiology of DU
2. To investigate the relationship between tfs4 genes, dupA type and cytokine response
3. To establish how the tfs4 / dup virulence system effects an immune response
Design/Methodology
Cytokine levels in antral and corpus gastric biopsies from Hp+ and Hp- donors attending for upper GI endoscopy will be characterised using real-time qPCR, along with dupA status, tfs4 profile, bacterial load and histological data. These samples and a human mononuclear cell model will be used to characterise the effect of dupA/tfs4 profile on cytokine induction, and our hypotheses tested using isogenic Hp mutants. To clarify possible mechanisms we will use flow cytometry, leukocyte cell lines and transcription factor/signalling assays.
Scientific/Medical opportunities
This will provide insights into the role of a novel Hp virulence system in orchestrating inflammatory signalling in the stomach and help determine why some patients develop DU rather than gastric carcinoma.
Duodenal ulcer promoting gene (dupA) is a novel Hp gene recently linked to the specific clinical outcome of DU and negatively associated with gastric carcinoma. dupA+ strains are associated with more intense antral neutrophil infiltration and higher antral IL-8 levels in vivo, giving biological plausibility to a role in DU pathogenesis. We have shown polymorphism at the dupA locus and that dupA is associated with an undescribed type IV secretion system, tentatively designated tfs4.
Our preliminary data using dupA disruption to explore phenotypes suggests that this virulence mechanism targets immune cells, in contrast to other Hp virulence factors which target epithelial cells. We found significantly higher Th1 cytokine levels, particularly IL-12, in mononuclear cell supernatants following culture with dupA+ strains than following culture with their dupA null mutants and dupA- strains. Disruption of other putative tfs4 components also significantly decreased IL-12 production. Flow cytometry suggested monocytes are an important source of this IL-12 in ex vivo specimens.
This study will investigate the immune response to dupA+ Hp strains in the human stomach and its role in pathogenesis.
Objectives
1. To characterise the cytokine response to dupA+ Hp strains in the human stomach, hypothesising that they are associated with a Th1 cytokine response with antral predominant inflammation in keeping with the pathophysiology of DU
2. To investigate the relationship between tfs4 genes, dupA type and cytokine response
3. To establish how the tfs4 / dup virulence system effects an immune response
Design/Methodology
Cytokine levels in antral and corpus gastric biopsies from Hp+ and Hp- donors attending for upper GI endoscopy will be characterised using real-time qPCR, along with dupA status, tfs4 profile, bacterial load and histological data. These samples and a human mononuclear cell model will be used to characterise the effect of dupA/tfs4 profile on cytokine induction, and our hypotheses tested using isogenic Hp mutants. To clarify possible mechanisms we will use flow cytometry, leukocyte cell lines and transcription factor/signalling assays.
Scientific/Medical opportunities
This will provide insights into the role of a novel Hp virulence system in orchestrating inflammatory signalling in the stomach and help determine why some patients develop DU rather than gastric carcinoma.