title: [Virulence changes of H5N1 avian influenza virus after gene reassortment].
abstract: OBJECTIVE
  Recently H5N1 subtype avian influenza virus (AIV) is capable of mortality to aquatic bird. The molecular basis for the virulence of this virus is still poorly understood.
  
  
  METHODS
  We characterized two H5N1 subtype viruses, A/mallard/Huadong/Y/2003 (Y) is nonpathogenic to mallard whereas A/mallard/Huadong/S/2005 (S) is highly pathogenic to mallard. Using reverse genetics, we constructed a series of single-gene or multiple-gene reassortants from these two viruses.
  
  
  RESULTS
  Substitution of single-gene for PB2, PB1, PA (3P), HA and of combination for 3P gene resulted in complete attenuation of S virus in mallard. However, these corresponding substitutions only slightly increased virulence of Y virus in mallard. Other gene segments had little contribution to the virulence of both viruses.
  
  
  CONCLUSIONS
  These results indicate that the pathogenicity of H5N1 AIV to mallard was regulated by multiple gene segments, and these regulations had more sensitive effect on highly pathogenic virus backbone than on low pathogenic virus backbone.
authors: Key Laboratory of Animal Infectious Disease, Ministry of Agriculture, School of Veterinary Medicine Yangzhou University, Yangzhou 225009, China. tyhlw@yahoo.com.cn
authors: Yinghua
authors: Y
authors: Tang
authors: Peipei
authors: P
authors: Wu
authors: Daxin
authors: D
authors: Peng
authors: Jinxue
authors: J
authors: Long
authors: Pinghu
authors: P
authors: Zhang
authors: Wenjun
authors: W
authors: Zhang
authors: Yanfang
authors: Y
authors: Li
authors: Wenbin
authors: W
authors: Wang
authors: Xiufan
authors: X
authors: Liu
mesh_terms: D000818:Animals; D005814:Genes, Viral / Q000235:genetics*; D005822:Genetic Vectors / Q000235:genetics; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics* / Q000472:pathogenicity*; D016865:Reassortant Viruses / Q000235:genetics* / Q000472:pathogenicity*; D011995:Recombination, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D014774:Virulence / Q000235:genetics