Figure 6. Binding of influenza A virus mutant H5N12.3.4 HA (A) and H5N8 HA (B) to fetuin. Binding was assayed as described in the legend to Figure 1. Mutated residues are indicated. 160/222/227, 160/193/222/227, and 160/193/199/222/227 refer to T160A/K222Q/S227R, T160A/K193N/K222Q/S227R and T160A/K193N/T199D/K222Q/S227R substitutions in H5N12.3.4 HA, respectively. Optical density at 450 nm (OD450) corresponds to binding of HA to glycoproteins. WT, wild-type; HA, hemagglutinin. H5N12.3.4, novel H5N1 virus clade 2.3.4.