No avian H7 N9 outbreaks have occurred since the introduction of H7 N9 inactivated vaccine in the fall of 2017.However,H7 N9 is still prevalent in poultry.To surveil the prevalence,genetic characteristics,and antigeni...No avian H7 N9 outbreaks have occurred since the introduction of H7 N9 inactivated vaccine in the fall of 2017.However,H7 N9 is still prevalent in poultry.To surveil the prevalence,genetic characteristics,and antigenic changes of H7 N9,over7000 oropharyngeal and cloaca swab specimens were collected from live poultry markets and farms in 15 provinces of China from 2017 to 2019.A total of 85 influenza virus subtype H7 N9 strains were isolated and 20 representative strains were selected for genetic analysis and antigenicity evaluation.Results indicated the decreased prevalence of low-pathogenic H7 N9 strains while highly-pathogenic H7 N9 strains became dominated since the introduction of vaccine.Phylogenetic analysis showed that strains from 2019 formed an independent small branch and were genetically distant to strains isolated in 2013–2018.Analysis of key amino acid sites showed that the virus strains may adapt to the host environment evolutionally through mutation.Our analysis predicted additional potential glycosylation sites for HA and NA genes in the 2019 strains.Sequence analysis of HA gene in strains isolated from 2018 to 2019 showed that there were an increased nucleotide substitution rate and an increased mutation rate in the first and second nucleotides of coding codons within the open reading frame.The hemagglutination inhibition(HI)assay showed that H7-Re1 and H7-Re2 exhibited a lower HI titer for isolates from 2019,while H7-Re3 and r LN79 showed a high HI titer.The protective effect of the vaccine decreased after15 months of use.Overall,under vaccination pressure,the evolution of influenza virus subtype H7 N9 has accelerated.展开更多
基金supported by the China National Natural Science Foundation(31972709,31830097)the China Agriculture Research System(CARS-41-G16)the Guangdong Key S&T Program(2019B020217002)from the Department of Science and Technology of Guangdong Province,China National Animal Disease Surveillance and Epidemiological Survey Program(No.201947)。
文摘No avian H7 N9 outbreaks have occurred since the introduction of H7 N9 inactivated vaccine in the fall of 2017.However,H7 N9 is still prevalent in poultry.To surveil the prevalence,genetic characteristics,and antigenic changes of H7 N9,over7000 oropharyngeal and cloaca swab specimens were collected from live poultry markets and farms in 15 provinces of China from 2017 to 2019.A total of 85 influenza virus subtype H7 N9 strains were isolated and 20 representative strains were selected for genetic analysis and antigenicity evaluation.Results indicated the decreased prevalence of low-pathogenic H7 N9 strains while highly-pathogenic H7 N9 strains became dominated since the introduction of vaccine.Phylogenetic analysis showed that strains from 2019 formed an independent small branch and were genetically distant to strains isolated in 2013–2018.Analysis of key amino acid sites showed that the virus strains may adapt to the host environment evolutionally through mutation.Our analysis predicted additional potential glycosylation sites for HA and NA genes in the 2019 strains.Sequence analysis of HA gene in strains isolated from 2018 to 2019 showed that there were an increased nucleotide substitution rate and an increased mutation rate in the first and second nucleotides of coding codons within the open reading frame.The hemagglutination inhibition(HI)assay showed that H7-Re1 and H7-Re2 exhibited a lower HI titer for isolates from 2019,while H7-Re3 and r LN79 showed a high HI titer.The protective effect of the vaccine decreased after15 months of use.Overall,under vaccination pressure,the evolution of influenza virus subtype H7 N9 has accelerated.
