Strong inhibition of cholera toxin B subunit by affordable, polymer-based multivalent inhibitors

Abstract

Cholera is a potentially fatal bacterial infection that affects a large number of people in the developing countries. It is caused by the cholera toxin (CT), an AB5 toxin secreted by Vibrio cholera. The toxin comprises of a toxic A-subunit and a pentameric B-subunit that binds to the intestinal cell surface. Several monovalent and multivalent inhibitors of the toxin have been synthesized but are too complicated and expensive for practical use in developing countries. Meta-nitrophenyl α-galactoside (MNPG) is a known promising ligand for CT and here mono- and multivalent compounds based on MNPG were synthesized. We present the synthesis of MNPG in greatly improved yields and its use while linked to a multivalent scaffold. We used economical polymers as multivalent scaffolds, namely polyacrylamide, dextran and hyperbranched polyglycerols (hPGs). Copper catalyzed alkyne azide cycloaddition reaction (CuAAC) produced the inhibitors that were tested in an ELISA-type assay and an intestinal organoid swelling inhibition assay. The inhibitory properties varied widely depending on the type of polymer and the most potent conju-gates showed IC50 values in the nanomolar range.