Evolution Analysis And Infectivity Evaluation Of Avian Influenza H16N3 Virus Isolated From Wild Birds

Since the H16 subtype avian influenza virus was first discovered in 2005,it has spread sporadically around the world,but the background is unclear.In order to understand the prevalence,genetic evolution and biological characteristics of H16 virus of wild birds,we had conducted the genetic evolution analysis and infectivity evaluation of H16N3 virus.Our project could provide a scientific basis for warnings of avian influenza viruses from wild birds.A low pathogenic avian influenza strain(named A/Black-headed Gull/Cangzhou/CZ638/2017,abbreviated CZ638)was isolated from Black-headed Gull in Cangzhou for the first time through surveillance of wild bird epidemic source.In this study,we evaluated the genetic evolution characteristics of the H16N3 by homology analysis,phylogenetic analysis,amino acid site mutation analysis,as well as molecular evolution rate speculation.Receptor binding assay,the pathogenicity and transmissibility of H16N3 in poultry(chicken,duck)and mammals(mouse,guinea pig and ferret)were performed to assess its biological characteristics.The main results are as follows:1.All 8 gene segments of CZ638 belonged to Eurasian lineage.It was a novel recombination virus derived from H13N8,H11N9,H13N6 and H16N3.2.The analysis results of receptor binding characteristics showed that the monobasic cleavage site of HA was INER?GLFG,which proved to be a low pathogenic influenza virus.The HA G228 S site mutates to S,suggesting its ability to bind to alpha 2-6 sialic acid receptors.M1(N30D,T215A),NS1(P42S,L98 F,I101M)and other mutations suggest that it may infect mammals.3.The analysis results of receptor binding characteristics showed that the CZ638 strain had the double receptor binding ability of the upper respiratory influenza virus receptor and the avian-like receptor,which further confirmed that the virus had the molecular basis to infect humans.4.The transmissibility and pathogenicity tests showed that CZ638 couldn't infect poultry(chickens,ducks)and mice,but could infect guinea pigs and ferrets without transmission,indicating that CZ638 couldn't spread among mammals.This study shows that CZ638 is a recombinant virus with the ability to infect mammals,but it doesn't have transmissibility.As a result,the risk of direct human-to-human transmission of the H16 subtypevirus is low,but there is still a possibility that it could infect humans.In addition,the virus currently doesn't have the ability of infecting SPF chickens and ducks,indicating that transhost barrier infection of land-fowl has not occurred.We should pay close attention to the transformation of H16 subtype virus from low to high pathogenicity due to mutation and recombination,and strengthen surveillance.The H16 subtype avian influenza virus can be used as a model virus to study the cross-species transmission from wild birds to domestic birds and poultry to mammals,which has important research significance.