Study On The Phylogenetic Analysis Of H9Subtype Of Avian Influenza Virus And Their Pathogenicity And Vaccine Assessment

H9N2subtype avian influenza virus has been already isolated and confirmed in the avian circulateworldwide. There is evidence that H9N2viruses have transmitted and established stable lineages inhumans and other Mammalians. The available evidence suggests that H9N2viruses did not appear inchickens until1994in China. The clinical symptoms of the infected chickens are a decline in egg and aretardation in growth or even death, resulted in a great economic losses in poultry industry.The four andfive patients with infuenza-like illnesses from Shaoguan and Shantou in Guangdong Province were thefirst evidence of H9N2can infect human, indicating that the H9N2subtype AIV is an important publichealth implications.To find out the variation of H9N2AIV in Mainland China, thirty viruses from2009to2011werechose to sequence the whole genome and took the phylogenetic analysis, and analyzed their antigenic,thus, it can reveal the epidemic regularity of the H9N2AIV.The results showed that, The HA amino acids of30viruses isolated from12provinces in mainlandChina, their cleave site are all-R (K) SSR/GL-, no cationic amino acid insert, showing typical characterof low pathogenic avian influenza. HA gene originated from CK/BJ/1/94-like virus. All thereceptor-binding sites have no big change, especially226site, having no preference to binding to SAα-2,6-Gal moieties in human cell.21of30viruses bear the CK/BJ/1/94-like NA genes, and the othersbear the G9-like NA genes, CK/BJ/1/94-like of NA gene have a9bp deletion and G9-like have no. PA、PB1and PB2gene originated from CK/SH/10/01-like virus, and the PB2had formed a new branchtaken DK/FJ/S2246/09as the representative virus. The entire30virus had the typical character of beinginfected the mice, but no lethal case; their affinities are higher than the viruses isolated before2000year.NP gene originated from CK/SH/10/01-like virus. NS gene has only one nuclear localization signal(NLS) in34~38amino acids, originated from CK/BJ/1/94-like virus. The entire30virus had the typicalcharacter of evaded from IFN and TNF-α. The M gene had formed a new branch taken DK/FJ/S2246/09as the representative virus.28of30viruses have the molecular characterization of amantadine resistancein AIV.Escherichia coli and Salmonella is common pathogens in poultry, and they are often mixed withthe H9subtype of avian influenza virus co-infection in poultry. This study was challenged by H9subtype avian influenza virus, Escherichia coli and Salmonella alone or co-infection on the SPFchickens and broiler chickens in a different order to evaluate their pathogenicity. The results showedthat, when co-infection with the H9subtype of avian influenza virus and bacterial, bacteria can extendthe distribution and proliferation of the virus in the host, H9can show more obvious clinical signs andpathological of the bacteria..To evaluate the immune efficacy of the vaccine strain Re-9ressortant avian influenza virus (AIV)derived from H9N2AIV, the4-week-old SPF chicks was immunized with Re-9inactivated vaccine andchallenged, respectively, at3weeks post immunization with5isolates of H9N2AIV isolated from2009 to2011. The results showed that the average antibody titer of the HI was up to9.5log2at3weeks postimmunization. In addition, the virus shedding was detected by virus isolations with chickenembryonated eggs from the trachea and cloaca swab samples collected at3,5and7days postchallenging, and virus shedding was all negative in the Re-9vaccinated vaccine groups, but the positiverates in the control groups were higher than80%at3and5days, and lower than60%7days postchallenge, respectively. These results demonstrated that the inactivated vaccine prepared with Re-9strain is high efficient against H9N2AIV infection.This study had taken phylogenetic analysis and antigenic analysis of thirty H9N2subtype AIVsisolated from2009to2011, and taken co-infection with H9AIV and bacteria, evaluated the immuneefficacy of the vaccine strain Re-9ressortant avian influenza virus, to give an important reference andguidance in prevention and control H9subtype avian influenza.