Materials and methods
Virus and virus inactivation
The H9N2 virus used in this study was A/Chicken/Hebei/4/2008.The complete genome sequences of the virus are available from GenBank under accession numbers FJ499463– FJ499470. The viruses were propagated in the allantoic cavities of 9-day-old embryonated eggs from specific-pathogen-free(SPF)hens for 48 to 60 h at 37 C.