title: A 20-amino-acid deletion in the neuraminidase stalk and a five-amino-acid deletion in the NS1 protein both contribute to the pathogenicity of H5N1 avian influenza viruses in mallard ducks.
abstract: Since 2003, H5N1-subtype avian influenza viruses (AIVs) with both a deletion of 20 amino acids in the stalk of the neuraminidase (NA) glycoprotein (A-) and a deletion of five amino acids at positions 80 to 84 in the non-structural protein NS1 (S-) have become predominant. To understand the influence of these double deletions in the NA and NS1 proteins on the pathogenicity of H5N1-subtype AIVs, we selected A/mallard/Huadong/S/2005 as a parental strain to generate rescued wild-type A-S- and three variants (A-S+ with a five-amino-acid insertion in the NS1 protein, A+S- with a 20-amino-acid insertion in the NA stalk, and A+S+ with insertions in both NA and NS1 proteins) and evaluated their biological characteristics and virulence. The titers of the AIVs with A- and/or S- replicated in DEF cells were higher than that of A+S+, and the A-S- virus exhibited a replication predominance when co-infected with the other variants in DEF cells. In addition, A-S- induced a more significant increase in the expression of immune-related genes in peripheral blood mononuclear cells of mallard ducks in vitro compared with the other variants. Furthermore, an insertion in the NA and/or NS1 proteins of AIVs resulted in a notable decrease in virulence in ducks, as determined by intravenous pathogenicity index, and the two insertions exerted a synergistic effect on the attenuation of pathogenicity in ducks. In addition, compared with A+S+ and A+S-, the A-S+ and A-S- viruses that were introduced via the intranasal inoculation route exhibited a faster replication ability in the lungs of ducks. These data indicate that both the deletions in the NA stalk and the NS1 protein contribute to the high pathogenicity of H5N1 AIVs in ducks.
authors.affiliation: College of Veterinary Medicine, Yangzhou University, Jiangsu Co-Innovation Center for the Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, P.R. China.
authors.forename: Yanfang
authors.initials: Y
authors.lastname: Li
authors.affiliation: College of Veterinary Medicine, Yangzhou University, Jiangsu Co-Innovation Center for the Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, P.R. China.
authors.forename: Sujuan
authors.initials: S
authors.lastname: Chen
authors.affiliation: College of Veterinary Medicine, Yangzhou University, Jiangsu Co-Innovation Center for the Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, P.R. China.
authors.forename: Xiaojian
authors.initials: X
authors.lastname: Zhang
authors.affiliation: College of Veterinary Medicine, Yangzhou University, Jiangsu Co-Innovation Center for the Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, P.R. China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Fu
authors.affiliation: College of Veterinary Medicine, Yangzhou University, Jiangsu Co-Innovation Center for the Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, P.R. China.
authors.forename: Zhiye
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: College of Veterinary Medicine, Yangzhou University, Jiangsu Co-Innovation Center for the Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, P.R. China.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Shi
authors.affiliation: College of Veterinary Medicine, Yangzhou University, Jiangsu Co-Innovation Center for the Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, P.R. China.
authors.forename: Yinbiao
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: College of Veterinary Medicine, Yangzhou University, Jiangsu Co-Innovation Center for the Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, P.R. China.
authors.forename: Min
authors.initials: M
authors.lastname: Gu
authors.affiliation: College of Veterinary Medicine, Yangzhou University, Jiangsu Co-Innovation Center for the Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, P.R. China.
authors.forename: Daxin
authors.initials: D
authors.lastname: Peng
authors.affiliation: College of Veterinary Medicine, Yangzhou University, Jiangsu Co-Innovation Center for the Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, P.R. China.
authors.forename: Xiufan
authors.initials: X
authors.lastname: Liu
mesh_terms: D000818:Animals; D004372:Ducks; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics* / Q000502:physiology; D005585:Influenza in Birds / Q000821:virology*; D009439:Neuraminidase / Q000235:genetics* / Q000502:physiology; D017361:Viral Nonstructural Proteins / Q000235:genetics* / Q000502:physiology
chemical_list: C085820:INS1 protein, influenza virus; D017361:Viral Nonstructural Proteins; D009439:Neuraminidase
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