title: Origin and characteristics of internal genes affect infectivity of the novel avian-origin influenza A (H7N9) virus.
abstract: BACKGROUND
  Human infection with a novel avian-origin influenza A (H7N9) virus occurred continuously in China during the first half of 2013, with high infectivity and pathogenicity to humans. In this study, we investigated the origin of internal genes of the novel H7N9 virus and analyzed the relationship between internal genes and infectivity of the virus.
  
  
  RESULTS
  We tested the environmental specimens using real-time RT-PCR assays and isolated five H9N2 viruses from specimens that were positive for both H7 and H9. Results of recombination and phylogeny analysis, performed based on the entire sequences of 221 influenza viruses, showed that one of the Zhejiang avian H9N2 isolates, A/environment/Zhejiang/16/2013, shared the highest identities on the internal genes with the novel H7N9 virus A/Anhui/1/2013, ranging from 98.98% to 100%. Zhejiang avian H9N2 isolates were all reassortant viruses, by acquiring NS gene from A/chicken/Dawang/1/2011-like viruses and other five internal genes from A/brambling/Beijing/16/2012-like viruses. Compared to A/Anhui/1/2013 (H7N9), the homology on the NS gene was 99.16% with A/chicken/Dawang/1/2011, whereas only 94.27-97.61% with A/bramnling/Beijing/16/2012-like viruses. Analysis on the relationship between internal genes and the infectivity of novel H7N9 viruses were performed by comparing amino acid sequences with the HPAI H5N1 viruses, the H9N2 and the earlier H7N9 avian influenza viruses. There were nine amino acids on the internal genes found to be possibly associated with the infectivity of the novel H7N9 viruses.
  
  
  CONCLUSIONS
  These findings indicate that the internal genes, sharing the highest similarities with A/environment/Zhejiang/16/2013-like (H9N2) viruses, may affect the infectivity of the novel H7N9 viruses.
authors.affiliation: Key Lab. of emergency detection for Public Health of Zhejiang province, Zhejiang provincial Centre for Disease Control and Prevention, Hangzhou, Zhejiang province, People's Republic of China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Feng
authors.forename: Haiyan
authors.initials: H
authors.lastname: Mao
authors.forename: Changping
authors.initials: C
authors.lastname: Xu
authors.forename: Jianmin
authors.initials: J
authors.lastname: Jiang
authors.forename: Yin
authors.initials: Y
authors.lastname: Chen
authors.forename: Juying
authors.initials: J
authors.lastname: Yan
authors.forename: Jian
authors.initials: J
authors.lastname: Gao
authors.forename: Zhen
authors.initials: Z
authors.lastname: Li
authors.forename: Shichang
authors.initials: S
authors.lastname: Xia
authors.forename: Yiyu
authors.initials: Y
authors.lastname: Lu
mesh_terms: D000818:Animals; D023061:Gene Order; D005814:Genes, Viral; D016679:Genome, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D064766:Influenza A Virus, H7N9 Subtype / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology*; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000235:genetics; D010802:Phylogeny; D062486:Public Health Surveillance; D014764:Viral Proteins / Q000235:genetics
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D014764:Viral Proteins; C487630:NA protein, influenza A virus; D009439:Neuraminidase