Effect of PVP-I on direct binding activity of influenza viruses to glycopolymers. (A) Virus binding activity to glycopolymers linked with α2,3 (filled red square) and α2,6 (filled blue triangle)-sialic acids. (B) Inhibition of virus binding to a specific polymer. Percentage of untreated control viruses was plotted against inhibitor concentration. (filled green square) α2,3 linkage + PVP-I; (empty pink square) α2,3 linkage + fetuin; (filled green triangle) α2,6 linkage + PVP-I; (empty pink triangle) α2,6 linkage + fetuin.