Pseudomonas aeruginosa (PA) and Burkholderia ambifaria (BA) are two opportunistic Gram negative bacteria and major infectious agents involved in lung infection of cystic fibrosis patients. Both bacteria can develop resistance to conventional antibiotherapies. An alternative strategy consists of targeting virulence factors in particular lectins with high affinity ligands such as multivalent glycoclusters. LecA (PA-IL) and LecB (PA-IIL) are two tetravalent lectins from PA that recognise galactose and fucose respectively. BambL lectin from BA is trimeric with 2 binding sites per monomer and is also specific for fucose. These three lectins are potential therapeutic targets in an anti-adhesive anti-bacterial approach. Herein, we report the synthesis of 18 oligonucleotide pentofuranose-centered or mannitol-centered glycoclusters leading to tri-, penta- or decavalent clusters with different topologies. The linker arm length between the core and the carbohydrate epitope was also varied leading to 9 galactoclusters targeting LecA and 9 fucoclusters targeting both LecB and BambL. Their dissociation constants (Kd) were determined using a DNA-based carbohydrate microarray technology. The trivalent xylo-centered galactocluster and the ribo-centered fucocluster exhibited the best affinity for LecA and LecB respectively while the mannitol-centered decafucocluster displayed the best affinity to BambL. These data demonstrated that the topology and nature of linkers were the predominant factors for achieving high affinity rather than valency.
Lectin A (LecA) from Pseudomonas aeruginosa is an established virulence factor. Glycoclusters that target LecA and are able to compete with human glycoconjugates present on epithelial cells are promising candidates to treat P. aeruginosa infection. A family of 32 glycodendrimers of generation 0 and 1 based on a bifurcated bis-galactoside motif have been designed to interact with LecA. The influences both of the central multivalent core and of the aglycon of these glycodendrimers on their affinity toward LecA have been evaluated by use of a microarray technique, both qualitatively for rapid screening of the binding properties and also quantitatively (K ). This has led to high-affinity LecA ligands with K values in the low nanomolar range (K =22 nm for the best one).
Due to the ability of Pseudomonas aeruginosa (PA) to develop antibiotic resistances, alternative therapeutic strategies have been proposed. Among others, carbohydrate multivalent molecules targeting lectin‐based virulent factors have been widely reported in particular those targeting LecA. LecA is a tetravalent galactose specific lectin involved in biofilm formation and cell internalization. Herein, we report the synthesis of 36 galactoclusters built from galactosides with aromatic and non‐aromatic aglycons and with an additional chain. The chains were either neutral or positively charged. Only the galactoclusters with naphthyl or tyrosine aglycon showed a moderate increase of binding for the positively charged 3‐dimethylammonium propyl chain. In contrast, the non‐aromatic galactoclusters display typically poorer binding properties towards LecA. The introduction of these side chains led to improved affinities up to becoming comparable to the high‐affinity aromatic galactoclusters.
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