title: Could a deletion in neuraminidase stalk strengthen human tropism of the novel avian influenza virus H7N9 in China, 2013?
abstract: Objective. A novel avian influenza A virus (AIV) H7N9 subtype which emerged in China in 2013 caused worldwide concern. Deletion of amino-acids 69 to 73 in the neuraminidase stalk was its most notable characteristic. This study is aimed to discuss the tropism and virulence effects of this deletion.
  
  
  METHODS
  Neuraminidase gene sequences of N9 subtype were collected from NCBI and GISAID. MEGA6.0, Stata12.0, and UCSF Chimera were employed for sequence aligning, significance testing, and protein tertiary structure homology modeling.
  
  
  RESULTS
  A total of 736 sequences were obtained; there were 81 human isolates of the novel AIV H7N9, of which 79 had the deletion. Among all the 654 avian origin sequences, only 43 had the deletion (p < 0.001). Tertiary structure displayed that the deletion obviously changed the spatial direction of neuraminidase.
  
  
  CONCLUSIONS
  The deletion in neuraminidase stalk could have strengthened human tropism of the novel AIV H7N9, as well as its virulence.
authors.affiliation: Department of Sanitary Microbiology, School of Public Health, Fudan University, Shanghai 200032, China. chenliangfd@sina.com.
authors.forename: Liang
authors.initials: L
authors.lastname: Chen
authors.affiliation: Intensive Care Unit of Burn and Trauma Center, Changhai Hospital, Second Military Medical University, Shanghai 200433, China. z8160720@126.com.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhu
authors.affiliation: Department of Sanitary Microbiology, School of Public Health, Fudan University, Shanghai 200032, China. xiongchenglong@fudan.edu.cn.
authors.forename: Chenglong
authors.initials: C
authors.lastname: Xiong
authors.affiliation: Key Laboratory of Public Health Safety, Ministry of Education, Fudan University, Shanghai 200032, China. epistat@gmail.com.
authors.forename: Zhijie
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Sanitary Microbiology, School of Public Health, Fudan University, Shanghai 200032, China. jianglufang@fudan.edu.cn.
authors.forename: Lufang
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Department of Epidemiology and Community Medicine, Faculty of Medicine, University of Ottawa, Ontario K1H 8M5, Canada. ychen@uottawa.ca.
authors.forename: Yue
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Key Laboratory of Public Health Safety, Ministry of Education, Fudan University, Shanghai 200032, China. gmzhao@shmu.edu.cn.
authors.forename: Genming
authors.initials: G
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Public Health Safety, Ministry of Education, Fudan University, Shanghai 200032, China. xiongchenglong1@sina.com.
authors.forename: Qingwu
authors.initials: Q
authors.lastname: Jiang
mesh_terms: D001483:Base Sequence; D002681:China; D006801:Humans; D064766:Influenza A Virus, H7N9 Subtype / Q000235:genetics / Q000502:physiology*; D007251:Influenza, Human / Q000821:virology; D009439:Neuraminidase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017384:Sequence Deletion; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D056189:Viral Tropism
chemical_list: D014764:Viral Proteins; D009439:Neuraminidase