Helicobacter pylori DNA's anti-inflammatory effect on experimental colitis.

Our laboratory has demonstrated a clinical inverse association between H. pylori infection and inflammatory bowel disease (IBD). In our most recent work we described a possible mechanism by which H. pylori can reduce the risk of developing IBD. Specifically, we were able to demonstrate the immuno-regulatory properties of the H. pylori genome and its ability to downregulate inflammatory responses through interaction with mucosal dendritic cells both in an in vitro and in vivo model. Furthermore, we were able to demonstrate the ability of H. pylori DNA to downregulate dendritic cell production of IL-12 and type I interferon, two pro-inflammatory cytokines. In the present work, we conducted further studies to examine the unique properties of the H. pylori genome and the exact mechanism through which it interacts with dendritic cells. Our data highlight a specific immuno-regulatory sequence (IRS), TTTAGGG, which occurs significantly more frequently as compared with other IRS sequences and is unique to the H. pylori genome. Additionally, we illustrate that H. pylori DNA has no effect on modulating the TLR-4 dependent LPS-induction of dendritic cell IL-12 production. This indicates that the inhibitory effect of H. pylori genomic DNA is restricted to the TLR-9 signaling pathway that senses bacterial DNA. In conclusion, the findings of this addendum strengthen the evidence for unique immunoregulatory properties of the H. pylori genome and revealed the importance of TLR-9 mediated mechanism in the pathogenesis of IBD.