Bacterial adhesion is a key step for initiating infection that frequently involves specific recognition of host glycans by microbial adhesins. This is the case for uropathogenic Escherichia coli (UPEC), which exploits FimH, a prevalent mannose-specific adhesin, for infecting the human urothelium. Different monovalent and multivalent compounds have been synthesized and evaluated as microbial antiadhesives. We here report on the development of a versatile microarray approach for evaluation of bacterial adhesion and efficiency of FimH-targeted compounds. A straightforward set-up was established, allowing to directly monitor the binding of fluorescently labeled E. coli UTI89 (UPEC clinical isolate) to custom-designed mannan microarrays. Three novel fullerene hexakis-adducts bearing 12 peripheral mannose residues grafted onto the C60 core by different spacers were tested in competition assays as representative compounds. The IC50 values obtained for the fullerenes evidenced a clear multivalency effect, with up to 18-fold enhancement of the relative inhibitory potential per mannose residue compared to methyl ¿-D-mannopyranoside, in line with previous studies. Differences among fullerenes were detected, pointing to a noticeable impact on compound activity of the precise structure and length of the spacer used for linking mannose to the fullerene core. Comparison of array-derived results obtained for the archetypal mannose-binding lectin concanavalin A with data obtained by isothermal titration calorimetry analyses of ConA-mannofullerene interactions fully validated the utility of the arrays for evaluating the inhibitory potential of anti-adhesive compounds.

This work was supported by the Marie Curie Initial Training Network DYNANO (PITN-GA-2011-289033), the CIBER of Respiratory Diseases (CIBERES) – an initiative from the Spanish Institute of Health Carlos III (ISCIII), and the Spanish Ministry of Economy and Competitiveness (grants BFU2012-36825, BFU2015-70052-R). I.K. and M.A.F. were funded by Marie Curie contracts from the European Commission.

29th International Carbohydrate Symposium - ICS 14-19 of July (2018), Lisboa, Portugal .-- http://www.ics2018.eventos.chemistry.pt/