Fig. 5: Viral variations in vaccinated chain and their impact on oropharyngeal shedding of H9N2 AIV.

A Linkage analysis of high-frequency (>10%) variants that emerged during homologous vaccinated passage. B Multistep growth curves of the indicated H9N2 AIV mutants in CEF infected at MOI of 0.001. All data are representative of or presented as means ± SD of three independent experiments. C Impact of NP-N417D, M1-V219I, and/or NS1-R140W on the replication and transmission of H9N2 AIV in chickens. Three chickens were intranasally inoculated with 106 EID50 of virus. After 24 h, the inoculated chickens were housed together with three contact chickens. The viral titers in oropharyngeal swabs from inoculated chickens (n = 3) were determined at 3, 5, and 7 dpi and at 3, 5, and 7 dpc for the contact chickens. Statistical significance relative to HB17 was assessed with two-way ANOVA (*P < 0.05; **P < 0.01).