Heterogeneities Of Antigenicity In Relation To The Genetic Variation Of HA Gene In Different H9N2Avian Influenza Viruses

The avian influenza virus is classified as a number of the Orthomyxoviridae genus. Itcause high morbidity and mortality in non-immunized chickens even in some immunizedchickens population with respiratory tract infections. Many scholars tried to discover themolecular variation trend of H9N2subtype AIV, and a lot of date on molecular epidemiologyhave been reported in the past several years. But the relation between the biological propertiesand genetic variations, especially the relationship between the genetic and antigenic evolutionof the HA is still not clear.This study was designed to explore the different periods of H9N2subtype AIV epidemicstrains variation in antigenic and molecular level, master of H9N2subtype avian influenzavirus variation at the molecular level, analysis of antigenic changes in the virus, which revealour the H9N2genetic variation trend for clinical comprehensive scientific provide a strongtheoretical basis for the prevention and control of H9N2avian influenza.In this paper,22prevailed H9N2AIV isolates in China during1998-2011were identified,purified, sequenced and analyzed, comparing with the46H9N2references in GenBank. Then,the phylogenetic tree was reconstructed based on those H9N2strains. First of all,6representative isolates were chosen, which belong to different genotype, to make for signalpositive serum. Secondly, the cross neutralization test was determined by using positiveserums in specific pathogen free (SPF) chicken embryos, respectively. Thirdly, the correlationof the virus neutralization index (VN) in chicken embryo was compared with the amino acidhomologies of HA gene of different H9N2isolates by SPSS14.0software in order to explorethe relationship between antigenic variations and genetic evaluations of the prevailed H9N2isolates undergo the effect of vaccination. Importantly, the correlation coefficient and index ofVN and amino acid homology was significantly correlated (p<0.01, R=0.6398), whichsuggested that the H9N2virus undergo10years of vaccination, has changed to some degree at the molecular level and antigenicity. Collectively, these data implied that antigenicvariations of H9N2isolates result in the genetic mutations of HA, which was essential fordeveloping the new vaccine.