Characterization Of H4Subtype Avian Influenza Virus In South China From2009to2011

South China has been regarded as one of the places that influenza is prone to take place, and nowis popular with highly pathogenic avian influenza virus (HPAIV) but along with many other lowlypathogenic avian influenza virus (LPAIV). In recent years, a large number of H6and H9subtypeLPAIVs have been isolated in south China and have become the main popular LPAIVs subtype. Weisolated a mounting number of H4subtype avian influenza virus (AIV) in regular national avianinfluenza virus surveillance in south China in2009, then we analyzed55viruses of this subtype from2009to2011to illustrate the it’s antigenicity, genetic evolutionary relationship and the ability to infectthe mammals model.Firstly, the results of antigenicity analysis of14viruses out of55showed that they were roughlydivided into4subgroups, and be of significant differences to reflect the antigenic diversity among H4subtype AIV in China. Secondly, the results of genetic evolution analysis of external genes of55virusesand internal genes of28viruses indicated the discrepant origins. HA genes were dramatically influencedby A/avian/Japan/8KI0185/2008(H4N6) isolate from Japan and might get evolution from it. The NAgenes, combined with HA genes, contained N2, N3, N6and N8and got low homology and complicatedorigins. Except for NS genes, the other internal genes belonged to America branch and werehomologous with the H3or H6subtype AIV isolated in China or surrounding regions and countries. NSgenes could be put into America branch and Eurasian branch and got low homology between them,highly reassorted with other subtype viruses. Genotyping results showed the complex and diversity ofthis subtype AIV. Eventually, the28whole-genome-sequenced viruses were challenged in BALB/c miceto determine the infection and virulence. It was found that5out of28did not be of the ability ofinfection, and it was only limited in the lung and turbinate in viruses isolating in the23infected, butnonlethal at all, which suggested that H4subtype viruses did not get the ability to infect the whole bodyby now.This research systematically illustrate the biological diversity and genetic complex of H4subtypeAIV in China, the virus is of complicated origins, significant antigenicity and multiple genotype, makesit hard to prevent and control in the future. Although it has not yet constitute a whole body infection, thediverse infection ability still implies the hazards it may pose in reassorting with HPAIV.