Figure 5

HA antigenic sites. A Amino acid alignments of the five antigenic sites A to E with HA sequences determined for French strains and other fully sequenced viral strains and compared with A/equine/Miami/1/1963. The antigenic sites defined for the human H3 influenza virus were used as a reference [36, 37, 39]. B Lateral and top views of the 3D structure of H3 hemagglutinin (PDB accession number: 4UO0) and location of its antigenic sites. While the HA2 domain (in pink and magenta) constitutes the stem, HA1 domains form the head of the HA bearing the antigenic sites. Antigenic sites are colored in cyan (site A), orange (site B), green (site C), red (site D), and yellow (site E). C Location of HA amino acid substitutions between the FC1 strains A/equine/Ohio/1/2003 and A/equine/Paris/1/2018. Amino acid changes are colored according to their positions in the corresponding antigenic sites (as in B) or in blue. D Location of HA amino acid substitutions between the FC2 strains A/equine/Richmond/1/2007 and A/equine/Saone-et-Loire/1/2015. Color patterning as in C.