A Surface Plasmon Resonance Assay for the Binding of Influenza Virus Hemagglutinin to Its Sialic Acid Receptor

We have developed a sensitive microscale binding assay to study the interaction between influenza hemagglutinin and its cell surface receptor sialic acid using real-time surface plasmon resonance. The glycoprotein fetuin was bound to a carboxymethylated-Dextran sensor surface usingN-hydroxysuccinimide andN-ethyl-N′-(dimethylaminopropyl) carbodiimide. Low-pH-induced BHA rosettes bind specifically to the fetuin-derivitized sensor surface, but not to an asialofetuin-derivitized sensor surface. Binding can be inhibited by preincubation of BHA rosettes with millimolar concentrations of inhibitors of the influenza hemagglutinin–sialic acid interaction. The association rate, dissociation rate, and dissociation constant for the multivalent interaction between BHA rosettes and the fetuin-derivitized sensor surface were also measured, allowing us to quantitate the tight binding achieved through the multivalent interaction between BHA rosettes and the fetuin-derivitized sensor surface.