Table 5.

Binding of monovalent receptor analogs, free α-anomer of Neu5Ac, α-methylglycoside of Neu5Ac (MN), 3′SL, and 6′SLN by influenza virusesa

Virus group and strainHost speciesHA subtypeApparent association constant (Kass[mM−1])Relative affinity with respect to Neu5Ac (Krel)b
Group 1
 Mal/TN/11464/85 (226Q, 228G)AvianH11.30.1110.
 Dk/Hokkaido/7/82 (226Q, 228G)AvianH320.15180.5590.30.08
 Leningrad/134/57 (226Q, 228G)HumanH20.70.05140.3200.40.07
 Udorn/72/R2 (226Q, 228G)HumanH32.50.2330.5130.20.08
 Udorn/72/R4 (226Q, 228S)HumanH32.30.25190.
Group 2
 Albany/7/57 (226L, 228G)HumanH21.
 RI/5+/57 (226L, 228S)HumanH21.
 Aichi/2/68 (226L, 228S)HumanH31.40.510.
 Udorn/72 (226L, 228S)HumanH34.
Group 3
 Sw/Netherlands/3/80 (225E, 155I)c Swine5.70.2211.
 Sw/Germany/2/81 (190D, 155V)c Swine50.381.
Seal viruses
 Seal/3984/92 (138S)c H31.41.30.9
  • a Binding was studied, and apparent association constants were determined in solution in a competitive assay, as described in Materials and Methods.

  • b The relative affinities reflect the ratio of the K ass values for a given sialoside and that for Neu5Ac (K rel =K [X]/K [Neu5Ac]). The higher the relative affinity, the better the sialosides bind (compared to free αNeu5Ac).

  • c 226Q and 228G are present in the HA of these viruses. Amino acids that differ from the avian virus consensus sequence in the other “key positions” of the HA RBS (23) are given in parentheses.