Figure 2
The decrease in the readouts of cross-MN titres due to HA A180V mutation. A The location of the amino acid mutations in the three-dimensional structure of the HA protein of the H9N2 avian influenza virus. The blue colour indicates the location of position 180 in the HA receptor-binding site. The yellow colour indicates the locations of the HA receptor-binding sites, including positions 91, 143, 145, 173, 180 (blue colour), 184, 185; the orange colour indicates the locations of the right edge of the receptor-binding pocket 214–219 and the left edge of the 128–132 receptor-binding pocket. B MN titres of F/98 immune sera from chickens (n = 8) to the F/98 or the rF/HAA180V viruses. C MN titres of rF/HAA180V immune sera from chickens (n = 8) to the F/98 or the rF/HAA180V viruses. D MN titres of GD/SS/94 immune sera from chickens (n = 6) to the F/98, rF/HAA180V or GD/SS/94 viruses. E MN titres of JS/YZ618/12 immune sera from chickens (n = 6) to the F/98, rF/HAA180V or JS/YZ618/12 viruses. F MN titres of rF/HAA180V immune sera from chickens (n = 6) to the F/98, rF/HAA180V, GD/SS/94, or JS/YZ618/12 viruses. *A ≥ fourfold change in MN titres of the standard antiserum was considered significant antigenic change. These data indicated that the fold change was relative to the levels of the virus rF/HAA180V.