Kinetic Insights into Cholera Toxin B-Biomimetic Glycan Interactions

Cholera is a diarrheal disease caused by Vibrio cholerae, which secretes cholera enterotoxin (CTX) in the small intestinal epithelium. The pentameric B subunit (CTB) of CTX binds to glycans on the cellular surface through a primary binding site for GM1 glycosphingolipid or galactose. However, GM1 is undetectable in the human SI, and fucose is a key alternative ligand. Previously, we developed linear norbornenyl glycopolymers that block CTB binding by forming CTB-glycopolymer aggregates. Here, we evaluate CTB-glycopolymer binding kinetics under flow conditions using surface plasmon resonance. A copolymer randomly displaying galactose and fucose formed stable complexes with nanomolar avidity, driven primarily by slow dissociation, even from low CTB density surfaces. In contrast, an equimolar mixture of homopolymers exhibited similar binding avidity and comparable inhibitory efficacy but did not display slow dissociation. These findings underscore the importance of codisplaying galactose and fucose on a single polymer backbone for stable complex formation and for developing clinically useful therapies.