Background & Aims
Recently there has been emerging epidemiological data to suggest Helicobacter pylori (H. pylori) may protect against certain chronic inflammatory diseases such as inflammatory bowel disease (IBD). However, the mechanism for the observed inverse association between H. pylori and IBD has not been described.
Methods
The frequency of immunoregulatory (IRS) to immunostimulatory (ISS) sequences within the genome of various bacteria was calculated using MacVector software. The induction of type I IFN and IL-12 responses by DNA-pulsed murine bone marrow–derived dendritic cells (BMDC) and human plasmacytoid dendritic cells (pDC) was analyzed by cytokine production. The effect of H. pylori DNA on E. coli DNA production of type I IFN and IL-12 was assessed. The in vivo significance of H. pylori DNA suppression was assessed in a DSS-model of colitis. The systemic levels of type I IFN were assessed in H. pylori-colonized and non-colonized patients.
Results
We showed that H. pylori DNA has a significantly elevated IRS:ISS ratio. In vitro experiments revealed the inability of H. pylori DNA to stimulate type I IFN or IL-12 production from mouse BMDCs or human pDCs. Additionally, H. pylori DNA was able to suppress E. coli-DNA production of type I IFN and IL-12. Administration of H. pylori DNA prior to the induction of DSS colitis significantly ameliorated the severity of colitis as compared to E. coli DNA or vehicle control in both an acute and chronic model. Finally, the systemic levels of type I IFN were found to be lower in H. pylori-colonized patients versus non-colonized controls.
Conclusions
Overall, our study indicates that H pylori DNA has the ability to down-regulate pro-inflammatory responses from DCs and this may in part explain the inverse association between H. pylori and IBD.
Helicobacter pylori evades host immune defenses and causes chronic gastritis. Immunity against intestinal pathogens is largely mediated by dendritic cells, yet the role of dendritic cells in acute H. pylori infection is largely unknown. We observed the recruitment of dendritic cells to the gastric mucosa of H. pylori-infected mice. Bone marrow-derived dendritic cells from mice responded to live H. pylori by upregulating the expression of proinflammatory cytokine mRNA (i.e., IL-1alpha, IL-1beta, and IL-6). The supernatant from dendritic cells stimulated with H. pylori for 18 h contained twofold higher levels of IL-12p70 than IL-10 and induced the proliferation of syngeneic splenocytes and type 1 T helper cell cytokine release (IFN-gamma and TNF-alpha). These responses were significantly lower compared with those induced by Acinetobacter lwoffi, another gastritis-causing pathogen more susceptible to host defenses. Analysis of whole H. pylori sonicate revealed the presence of a heat-stable factor secreted from H. pylori that specifically inhibited IL-12 but not IL-10 release from dendritic cells activated by A. lwoffi. Our findings suggest that dendritic cells participate in the host immune response against H. pylori and that their suppression by H. pylori may explain why infected hosts fail to prevent bacterial colonization.
Background-The growing concern over the emergence of antibiotic-resistant Helicobacter pylori infection is propelling the development of an efficacious vaccine to control this highly adaptive organism.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.