title: [Origin of hemagglutinin and neuraminidase gene of swine influenza A H1N1 viruses].
abstract: OBJECTIVE
  To understand the origin of hemagglutinin (HA), and neuraminidase (NA) gene of swine influenza A (H1N1) viruses isolated in pigs in mainland China in 2002 and reveal the reason of pathogenesis of them in pigs.
  
  
  METHODS
  The target gene amplified by PCR,PCR product was linked with PGEM-T Easy Vector(Promega company, USA) at 4? degrees C, the recombined plasmid was transferred into DH 10B bacteria, positive colonies were selected and identified them with restriction enzyme. Afterwards, they were sent to Liu He Tong company in Beijing for testing nucleotide sequence. Finally, phylogenetic analysis of the sequencing data was performed with MegAlign (Version 1.03)and Editseq (Version 3.69) software.
  
  
  RESULTS
  The HA and NA genes of three strains of swine influenza A (H1N1) viruses isolated from pigs in China were closely related to those of swine influenza A (H1N1) virus, but different from those of avian or human influenza A (H1N1) virus. The swine strain of influenza A (H1N1) virus isolated in 2002 was derived from swine influenza A (H1N1) virus circulated in pigs in China in 1991. Since the antigenic drifts of HA and NA proteins of the new isolates occurred, their activity in pigs is increasing and they can cause disease in pigs.
  
  
  CONCLUSIONS
  The HA and NA genes of three strains of influenza A (H1N1) virus tested were identified to be derived from those of swine influenza A (H1N1) virus. The increased activity and pathogenesis of them in pigs were most likely due to antigenic drifts of HA and NA proteins of the new isolates.
authors.affiliation: Department of Influenza, National Institute of Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 100052, China.
authors.forename: Yuan-ji
authors.initials: YJ
authors.lastname: Guo
authors.forename: Le-ying
authors.initials: LY
authors.lastname: Wen
authors.forename: Min
authors.initials: M
authors.lastname: Wang
authors.forename: Ye
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jun-feng
authors.initials: JF
authors.lastname: Guo
authors.forename: Zi
authors.initials: Z
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D006388:Hemagglutinins / Q000235:genetics*; D053118:Influenza A Virus, H1N1 Subtype; D009980:Influenza A virus / Q000235:genetics* / Q000302:isolation & purification; D009439:Neuraminidase / Q000235:genetics*; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D013552:Swine
chemical_list: D006388:Hemagglutinins; D009439:Neuraminidase