Evolution And Pathogenicity Research Of H5N6 Subtype Avian Influenza Virus In South China In 2016

Since its first notification on 2014 in Sichuan province in China,from 2014 to December2016,avian influenza A?H5N6?virus has caused eighteen cases epidemic in ten provinces of C hina.The H5N6 virus not only caused loss of poultry industry,but also threat people's public health and safety.19 strains of H5N6 subtypes avian influenza viruses were isolated from Guangdong in China in 2016.For analyzing genetic evolution,other biological characteristics and pathogenic analysis,we sequenced 19 strains viruses.In this study,the cleavage site in HA protein of these 19 strains was RRRKR?G that had five basic amino acids,which was the typical molecular characteristic of H5 subtype highly pathogenic avian influenza virus.All strains had 11 amino acids deleted in the neck of NA protein.There were no mutations in the Neuraminidase inhibitors resistance sites of NA protein.For the analysis sequence of PB2 genes,all strains were E at 627 site of PB2protein,which was the characteristic of typical poultry virus.All strains have not mutation in 701 site of PB2 protein.6 strains viruses had mutations at the 31 site of M2 protein,which were related to drug resistance.To molecular evolution analysised the whole genome sequence of these 19 strains AIV found that mostly strains were divided into some clades,including GD-like?Euaasian lineage?EC-like?ZJ-like?VN 2014-like?GD 2016-like and Mix-like.Some strains present genetic recombination from different genotypes.The HA gene of these H5N6 subtype avian influenza virus were divided into Clade 2.3.4.4.And 1 to 3 amino acid variants were detected compared with Re-8 vaccine strains.In order to understand the pathogenicity and transmission of the H5N6 subtype viruses,in this study,SPF chickens were intranasal?i.n.?inoculated with 10³EID₅₀ and 10⁶EID₅₀ in0.1ml to infected group and contact group respectively.In the 10³EID₅₀/0.1ml infected study,P41 virus was highly pathogenic and to chicken compared with other viruses,and inoculated group shedding was detected.In the 10⁶EID₅₀/0.1ml infected study,A41,A48and A51 were highly pathogenic to chicken compared with A58 virus.All chicken including inoculated group and contact group shedding were detected.Although A58 has lower pathogenic compared with other viruses,but all chicken including inoculated group and contact group died within 10 DPI.Therefore,the H5N6 virus isolated in waterfowl was high pathogenic to chicken,and showed different pathogenicity to some extent,furthermore the virus could transmission between chickens by contact.