Table 4.

Comparison of the receptor-binding activities of WSN, SD0, and egg-adapted strains of SD0

VirusNA stalkRelative HA titeraBinding to sialylglycopolymersb
3′SL-PAA6′SLN-PAA
WSNYES111
SD0NO11.41.6
2EANO>324020
0EAYES13.42.7
21EAYES112.5
  • a Ratio of hemagglutinating titers determined at 4 and 20°C (ratio = HA at 4°C/HA at 20°C). A higher ratio indicates a lower affinity for sialic acid substrates.

  • b The relative binding affinities for each sialylglycopolymer were calculated by the formulaK rel =K aff(x)/K aff(WSN). Higher values of K rel correspond to lower affinities. For each polymer, K aff of WSN = 1.