Table 2

Receptor specificity of the different mutant A/H5N1 viruses, as determined by a modified TRBC hemagglutination assay. Introduction of Q222L and G224S in the A/H5N1 HA resulted in a receptor binding preference switch from the avian α-2,3– to the human α-2,6–linked SA receptor. Subsequent substitution of H103Y and T156A resulted in an increased affinity for α-2,3– and α-2,6–linked SA, in agreement with glycan array studies (51). For details, see supplementary experiment 9. HAU, hemagglutination units.

VirusSubtypeHA titer (HAU/50 μl)
TRBCα-2,3–linked TRBCα-2,6–linked TRBC
A/Netherlands/213/03H3N264064
A/Vietnam/1194/04H5N164640
A/H5N1PB2 E627KH5N164160
A/H5N1HA H103Y,T156A PB2 E627KH5N164480
A/H5N1HA Q222L,G224S PB2 E627KH5N164024
A/H5N1HA H103Y,T156A,Q222L,G224S PB2 E627KH5N164432