Multivalent thiosialosides and their synergistic interaction with pathogenic sialidases.

Sialidases (SA) hydrolyze sialyl residues from glycoconjugates of the eukaryotic cell surface and are virulence factors expressed by pathogenic bacteria, viruses and parasites. The catalytic domain of SA are often flanked with carbohydrate-binding module(s) previously shown to bind sialosides and to enhance enzymatic catalytic efficiency. Here we designed non-hydrolyzable multivalent thiosialosides as probes and inhibitors of V. cholerae, T. cruzi and S. pneumoniae (NanA) sialidases. NanA was truncated from the catalytic and lectinic domains (NanA-L and NanA-C) to probe their respective roles when interacting with sialylated surfaces and the synthetically designed di-, and polymeric thiosialosides. NanA-L domain was shown to fully drive NanA binding, improving affinity for the thiosialylated surface and compounds by more than two orders of magnitude. Importantly, each thiosialoside grafted onto the polymer was also shown to reduce NanA and NanA-C catalytic activity with a 3000-fold higher efficiency compared to the monovalent thiosialoside reference. These results extend the concept of multivalency for designing potent bacterial and parasitic sialidase inhibitors.