Figure 2 Antigenic sites on
the surface of the HA protein of H9N2 AIV. The HA amino acid sequence of
CQY-2014 isolate and mutations were uploaded to the SWISS-MODEL website
for model prediction, and the predicted trimeric proteins were annotated
using the ChimeraX 1.3 software. A: Forty-six antigenic sites
were labeled gray in the α-subunits, and the six preselected
high-frequency mutation sites were labeled yellow in the β-subunits.B: When asparagine was substituted with glycine at site 201
(D201G), the α helix structure remained unchanged, but the surface
structure changed significantly (red boxes).