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.