Biological Characterization Of H5 Avian Influenza Viruses Isolated From In China Between 2017 And 2018

In order to understand the biological characteristics of H5 subtype avian influenza viruses in China from 2017 to 2018,we conducted 24 H5 subtype avian influenza virus isolates for whole genomic phylogenic analysis and antigenic analysis,which according to the difference of HA and NA gene evolution and separation conditions that isolated from the avian influenza epidemiological surveillance in 2017-2018.Based on the above analysis results,further choose 18 virus isolates for the BALB/c mice pathogenic experiments,9 virus isolates for the receptor binding property analysis.By analyzing the genetic evolution of the surface genes of 24 strains of virus,except for one H5N3 subtype virus is a low pathogenic AIV,the other 23 strains contains the most H5N6 subtypes and a small amount of H5N1 subtypes,and all 23 strains possessed a typical characteristic of highly pathogenic AIV.Most of the virus isolates belonged to Clade 2.3.4.4 in China from 2017 to 2018.19H5 AIVs can be further divided into four small groups of 2.3.4.4.a,b,c,and d according to the 96%homology of nucleotides in this clade.24 strains of virus can be divided into 16 different genotypes by analyzing the genetic evolution of internal genes.Most of the internal genes of the virus are derived from the early H5 subtype AIV,but there are also a wide range of internal gene sources of different branch viruses.The antigenicity analysis results of the virus showed that the most of virus are reacted weakly with the recently used Re-8 vaccine.These data indicated that the antigenicity of the current epidemic strains has significant change.A 2.3.4.4.d clade H5N6 virus can be applied for the candidate vaccine which get good cross-reactivity with most viruses from 2017 to 2018.All of the 18 strains were replicated in BALB/c mice without prior adaptation,and presented three different pathogenicities of different viruses.Analysis of the receptor binding of 9 strains of viruses revealed that most of the virus isolates had strong α-2,3 receptor binding properties,only 2 virus isolates possessed a certain ability to bind α-2,6 receptors.In summary,the antigenicity of H5 avian influenza virus in China has significant changes during the period of 2017-2018.The gene sources of H5 subtype AIVs were multiple in China,the phenotype of virus biological characteristics is diverse,and some strains have a strong pathogenicity to mammals.