Figure 3. HA receptor specificity of H3 subtype IAV strains correlates with sensitivity to SAP and PTX3.

(A) Human erythrocytes were desialylated and subsequently resialylated with α(2,3)- or α(2,6)-sialyltransferases and used in hemagglutination assays. All viruses were adjusted to 64 HAU on native erythrocytes and showed no hemagglutinating activity (<1 HAU) against desialylated erythrocytes (data not shown). (B) Inhibition of HA activity of H3 subtype IAV by pentraxins. SAP or PTX3 were diluted in TBS containing 10 mM Ca²⁺ and used in a standard HI assay. Bars indicate the minimum concentration of SAP or PTX3 required to inhibit 4 HAU of each virus tested. Dashed line represents the highest concentration of inhibitor tested (10 µg/ml). ‘+’ indicates a value of >10 µg/ml. Data are representative of 2 or more independent experiments.