Replication and Transmission of H9N2 Influenza Viruses in Ferrets: Evaluation of Pandemic Potential
Figure 4
Effect of Leu226 or Gln226 mutations on receptor specificity of H9N2 viruses.
The importance of amino acid 226 of HA in receptor specificity was confirmed by site-directed mutagenesis followed by glycan microarray analysis. Viruses with a natural Leu226 (A: RGWF10 L) or Gln226Leu mutation (D: mQa88 L ) bind to human-type α2-6 sialosides (glycans 33 to 46), whereas viruses with Leu226Gln mutation (B: mWF10 Q) or natural Gln226 (C: RGQa88 Q) bind to avian-type α2-3 sialosides (glycans 1 to 32). Viruses were analyzed at hemagglutination titers of 128 per 50 µl. Allantoic fluid was used as negative control (E). Glycans 1–32 are avian-type α2-3 sialosides (light gray) and 33–46 are human-type α2-6 sialosides (dark gray). L and Q correspond to Leu226 and Gln226, respectively in the HA RBS. The complete structures of each sialoside are available upon request.