Département de chimie moléculaire

Multivalent interactions between complex carbohydrates and oligomeric C-type lectins govern a wide range of immune responses. Up to date{,} standard SPR (surface plasmon resonance) competitive assays have largely been to evaluate binding properties from monosaccharide units (low affinity{,} mM) to multivalent elemental antagonists (moderate affinity{,} µM). Herein{,} we report typical case-studies of SPR competitive assays showing that they underestimate the potency of glycoclusters to inhibit the interaction between DC-SIGN and immobilized glycoconjugates. This paper describes the design and implementation of a SPR direct interaction over DC-SIGN oriented surfaces{,} extendable to other C-type lectin surfaces as such Langerin. This setup provides an overview of intrinsic avidity generation emanating simultaneously from multivalent glycoclusters and from DC-SIGN tetramers organized in nanoclusters at the cell membrane. To do so{,} covalent biospecific capture of DC-SIGN via StreptagII /StrepTactin interaction preserves tetrameric DC-SIGN{,} accessibility and topology of its active sites{,} that would have been dissociated using standard EDC-NHS procedure under acidic conditions. From the tested glycoclusters libraries{,} we demonstrated that the scaffold architecture{,} the valency and the glycomimetic-based ligand are crucial to reach nanomolar affinities for DC-SIGN. The glycocluster 3.D illustrates the tightest binding partner in this set for a DC-SIGN surface (KD= 18 nM). Moreover{,} the selectivity at monovalent scale of glycomimetic D can be easily analyzed at multivalent scale comparing its binding over different C-type lectin immobilized surfaces. This approach may give rise to novel insights into the multivalent binding mechanisms responsible for avidity and make a major contribution to the full characterization of the binding potency of promising specific and multivalent immodulators.