Identification And Antigen Characterization Of H9N2 Subtype Avian Influenza Isolates In Liaoning Province

The pathogenicity of H9N2 subtype avian flu virus is usually low the infection won't cause death of the avian host.he H9N2 subtype avian influenza virus could reduce the production performance,under certain circumstanceif H9N2 subtype avian flu virus coinfected with other or bacterial pathogens could cause the death of the avian host.,The H9N2 subtype of avian influenza virus could also act as a gene donor,reassort with H5,H7 and other subtypes of avian influenza viruses,There're also human infectied cases of,so the prevention and control of H9N2 subtype influenza virus is particularly important.Because the treatment and prevention strategies of diseases caused by various subtypes of influenza viruses are different,it is important to establish a rapid subtypes detection method for the early diagnosis,prevention and control of influenza.In this paper,the PCR method for the classification and identification of H5,H7 and H9 subtypes of influenza viruses was firstly established.The method was used to detect the pharynx and anus swabsamples collected in the live poultry market.11 positive samples of H9N2 subtype of avian influenza virus were detected by this method.11 H9N2 virus named A/Chicken/Liaoning/01/2017(H9N2)-A/Chicken/Liaoning/11/2017(H9N2)were isolated from the 11 positive samples.The HA and NA gene of the 11 H9N2 viruses were sequenced,2 viruses A/Chicken/Liaoning/05/2017(H9N2)and A/Chicken/L iaoning/06/2017(H9N2)HA genes contain amino acids differences in 100,221,250,315 sites compared with the other 9 viruses.The antigenicity of the 11 viruses were analyzed by using H9N2 standard serum,it turned out that the antigenicity of A/Chi cken/Liaoning/05/2017(H9N2)and A/Chicken/Liaoning/06/2017(H9N2)experienced more variation than other Liaoning H9N2 viruses,,the four sites mutation at HA100,221,250,315,might affect the antigenicity of the virus.We used the two viruses to infect SPF chickens and collected antisera at 21 days post inoculation..HI assay with the two viruses antisera got high HI titers against all the 11 viruses,indicated that the two viruses represent the H9N2 virus antigenicity evolution direction.Therefore,these two strains of H9N2 virus may be the vaccine stock strains of H9N2 subtype avian influenza virus in Liaoning province.