Analysis of influenza virus receptor specificity using glycan-functionalized gold nanoparticles

Recent cases of human infection with avian influenza H5N1 and H7N9 viruses underscore an urgent need for techniques that can rapidly assess their potential threat to the humans. Determination of the receptor-binding property of influenza virus is crucial to direct viral control and prevention measures. Current methods to perform this analysis are dependent on immunoanalytical strategies that use unstable biological components and complex procedures. We have developed a facile colorimetric assay to determine the interaction of the viral hemagglutinin (HA) protein with host glycan receptors using glycan-functionalized gold nanoparticles (gGNPs). This method is based on the color and absorbance changes of gold probes when the solution is simply mixed with HAs or intact viruses. The resulting sensitivity and selectivity has enabled HA/virus binding to various glycan structures to be differentiated visually and rapidly. Using this system, we have screened, in parallel, the receptor specificity of eight representative human and avian viral HAs and three whole viruses including an emerging H7N9 strain. Our results reveal the detailed receptor-binding profiles of H7N9 virus and its HA and show that they effectively bind to human-type receptors. This gGNP-based assay represents a strategy that would be helpful for developing simple and sensitive systems to probe glycan-mediated biological processes.