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.

Mono- and polyvalent ligands with strong affinities for the mannose-binding adhesin FimH were synthesised, and their anti-adhesive properties against ten E. coli strains were compared in two cell-based assays. The compounds were assessed against the non-pathogenic E. coli K12 and nine strains isolated by coproculture or from patients with osteoarticular infections (OIs), Crohn's disease (CD) and urinary tract infections (UTIs). The results showed that the compounds could inhibit the whole set of bacterial strains but with marked differences in terms of effective concentrations. The relative inhibitory potency of the monovalent compounds was also conserved for the ten strains and in the two assays. These results clearly suggest that a potent monovalent anti-adhesive assessed on a single E. coli strain will probably be effective on a broad range of strains and may treat diverse E. coli infections (OIs, CD and UTIs). In contrast, the polyvalent compounds showed a significant strain-dependancy in preventing E. coli attachment to intestinal cells. The multivalent antiadhesive effect may therefore vary depending on the E. coli strain tested.

Shear force exerted on uropathogenic Escherichia coli adhering to surfaces makes type-1 fimbriae stretch out like springs to catch on to mannosidic receptors. This mechanism is initiated by a disruption of the quaternary interactions between the lectin and the pilin of the two-domain FimH adhesin and transduces allosterically to the mannose-binding pocket of FimH to increase its affinity. Mannose-specific adhesion of 14 E. coli pathovars was measured under flow, using surface plasmon resonance detection on functionalized graphene-coated gold interfaces. Increasing the shear had important differential consequences on bacterial adhesion. Adherent-invasive E. coli, isolated from the feces and biopsies of Crohn’s disease patients, consistently changed their adhesion behavior less under shear and displayed lower SPR signals, compared to E. coli opportunistically infecting the urinary tract, intestines or loci of knee and hip prostheses. We exemplified this further with the extreme behaviors of the reference strains UTI89 and LF82. Whereas their FimA major pilins have identical sequences, FimH of LF82 E. coli is marked by the Thr158Pro mutation. Positioned in the inter-domain region known to carry hot spots of mutations in E. coli pathotypes, residue 158 is indicated to play a structural role in the allosteric regulation of type-1 fimbriae-mediated bacterial adhesion.

Thiazolylaminomannosides (TazMan) are FimH antagonists with anti‐adhesive potential against adherent‐invasive Escherichia coli (AIEC) promoting gut inflammation in patients with Crohn's disease. The lead TazMan is highly potent in vitro, but shows limited in vivo efficiency, probably due to low pH stability and water solubility. We recently developed a second generation of stable TazMan, but the anti‐adhesive effect was lower than the first. Herein we report a co‐crystal structure of the lead TazMan in FimH, revealing that the anomeric NH group and the second thiazole moiety provide a positive hydrogen bonding interaction with a trapped water molecule, and π‐stacking with Tyr48 of FimH, respectively. Consequently, we developed NeoTazMan homologated with a methylene group for low‐pH and mannosidase stability with a conserved NH group and bearing various heterocyclic aglycones. Microencapsulation of the lead NeoTazMan in γ‐cyclodextrin dramatically improved water solubility without disrupting the affinity for FimH or the anti‐adhesive effect against AIEC isolated from patients with Crohn's disease.

A water-soluble "NSO" complexing agent was designed for polonium(iv) decorporation. The bifunctional ligand showed outstanding Po(iv) complexing abilities, with a conditional stability constant three orders of magnitude higher than the reference ligand BAL.

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