Adherent-invasive Escherichia coli (AIEC) have previously been shown to induce gut inflammation in patients with Crohn's disease (CD). We developed a set of mannosides to prevent AIEC attachment to the gut by blocking the FimH bacterial adhesin. The crystal structure of the FimH lectin domain in complex with a lead thiazolylaminomannoside highlighted the preferential position for pharmacomodulations. A small library of analogues showing nanomolar affinity for FimH was then developed. Notably, AIEC attachment to intestinal cells was efficiently prevented by the most active compound and at around 10000-fold and 100-fold lower concentrations than mannose and the potent FimH inhibitor heptylmannoside, respectively. An ex vivo assay performed on the colonic tissue of a transgenic mouse model of CD confirmed this antiadhesive potential. Given the key role of AIEC in the chronic intestinal inflammation of CD patients, these results suggest a potential antiadhesive treatment with the FimH inhibitors developed.

Blocking the adherence of bacteria to cells is an attractive complementary approach to current antibiotic treatments, which are faced with increasing resistance. This strategy has been particularly studied in the context of urinary tract infections (UTIs), in which the adhesion of pathogenic Escherichia coli strains to uroepithelial cells is prevented by blocking the FimH adhesin expressed at the tips of bacteria organelles called fimbriae. Recently, we extended the antiadhesive concept, showing that potent FimH antagonists can block the attachment of adherent-invasive E. coli (AIEC) colonizing the intestinal mucosa of patients with Crohn's disease (CD). In this work, we designed a small library of analogues of heptyl mannoside (HM), a previously identified nanomolar FimH inhibitor, but one that displays poor antiadhesive effects in vivo. The anomeric oxygen atom was replaced by a sulfur or a methylene group to prevent hydrolysis by intestinal glycosidases, and chemical groups were attached at the end of the alkyl tail. Importantly, a lead compound was shown to reduce AIEC levels in the feces and in the colonic and ileal mucosa after oral administration (10 mg kg(-1) ) in a transgenic mouse model of CD. The compound showed a low bioavailability, preferable in this instance, thus suggesting the possibility of setting up an innovative antiadhesive therapy, based on the water-soluble and non-cytotoxic FimH antagonists developed here, for the CD subpopulation in which AIEC plays a key role.

The anti-adhesive strategy, consisting of disrupting bacterial attachment to the host cells, is widely explored as an alternative to antibiotic therapies. Recently, thiazolylmannosides (TazMans) have been identified as strong anti-adhesives of E. coli strains implied in the gut inflammation of patients with Crohn's disease. In this work, we developed a second generation of TazMans with improved chemical stability. The anomeric nitrogen was substituted by short linkers and the compounds were assessed against the bacterial adhesin FimH and the clinically isolated LF82 E. coli strain in four in vitro assays. The results obtained on the FimH adhesin alone and the whole bacteria enabled the identification of a candidate for further in vivo evaluations.