Pathogenicity And Cross-species Transmission Of Influenza A (H7N9)Virus Isolated From Environment

Since the first case of H7N9 influenza virus infecting humans in Shanghai in 2013,Anhui,Jiangsu,etc.have also occurred.Cases of H7N9 avian influenza have also occurred in poultry,which has brought losses to the breeding industry and also brought global public health challenge.It has been confirmed that mutations of amino acids in genes of influenza viruses can cause it to spread and infect humans,but there were few reports on influenza viruses of environmental sources.Therefore,this study conducted homology,genetic evolution,and amino acid mutation analysis of an environmental source H7N9 influenza virus in Hebei Province in 2019.In order to explore the pathogenicity of virus to mammals and the risk of cross-species transmission,mouse-adapted virus(MA-P5 for short)was constructed through the method of mouse lung-lung passage.The main contents of the study were as follows:1.The influenza A(H7N9)virus was isolated from environmental swabs collected from a live poultry trading market in Hebei Province in 2019 and named A/Environment/Hebei/621/2019(H7N9)(EN621 or WT).The 8 genes of the virus were amplified and sequenced,genetic evolution analysis,homology and important amino acid site analysis.The results showed that PB2,PB1,PA,HA5 NP,NA,M,NS gene fragments with the highest nucleotide homology strains were all avian influenza(H7N9)virus.The eight genes belonged to the Eurasian branch and highly homologous to the corresponding genes of human H7N9 influenza strain.2.WT and MA-P5 receptor binding characteristics test showed that WT and MA-P5 have the ability to bind to ?-2,3 sialic acid receptor and ?-2,6 sialic acid receptor,respectively,and MA-P5 virus have stronger ability to bind to the receptor.This meant that the WT virus and MA-P5 virus can not only infect poultry,but also humans.3.The results of the mouse pathogenicity test showed that the weight change and mortality of WT virus infected mice were lower than the weight change and mortality of MA-P5 virus infected mice,indicated that MA-P5 virus was highly pathogenic to mammals.Serological results showed that MA-P5 virus did not produce antibodies in mice after infection,while the H7 subtype influenza antibodies could be detected in the body after the WT virus infected mice.4.The transmission ability test between guinea pigs showed that both WT virus and MA-P5 virus can be transmitted through direct contact and aerosol transmission,but the aerosol transmission ability of the MA-P5 virus was stronger than that of WT,which indicated that MA-P5 virus had a certain ability to spread across species.After comparing the whole genome sequence of WT and MA-P5,it was found that the amino acid site mutations of PB2(E627K)and PB1(H115Q)are closely related to their pathogenicity and transmission ability.In this study,genetic evolution,amino acid site analysis,receptor binding characteristics,pathogenicity,and cross-species transmission risk of H7N9 influenza virus from environmental sources were studied.The results showed that isolated and mouse-adapted viruses have a certain risk of cross-species transmission among mammals.It is reminded that the monitoring of the PB2 and PB1 genes of the H7N9 influenza virus should be strengthened,which provides a theoretical basis for the prevention and control of the H7N9 influenza virus.