title: [Origin of internal genes of two strains of swine influenza A (H1N1) virus].
abstract: BACKGROUND
  Through the analysis of internal genes of viruses to understand whether the internal genes of two strains of swine influenza A(H1N1) virus contain the gene segment deriving from avian influenza A viruses, and whether the reassortment of the internal genes occurred between swine H1N1 and swine H9N2 viruses.
  
  
  METHODS
  Viruses were passaged in embryonated hen eggs and virion RNA was extracted from allantoic fluids and reverse transcribed to synthesize cDNA. cDNA was amplified by PCR and the PCR product was purified with a purification kit. Afterwards, RNA sequence analysis was performed by dideoxynucleotide chain termination and a cloning method. Finally, phylogenetic analysis of the sequencing data was performed with MegAlign (version 1.03).
  
  
  RESULTS
  All the six, but PB2 gene segment internal gene segments were the same between A/swine/Beijing/1/2002(H1N1) and A/Swine/Beijing/3/2002(H1N1) viruses. Whereas all the six internal gene segments in two trains of swine (H1N1) virus were similar to those of swine H1N1 viruses, but different from those of classical strain of swine (H1N1) virus.
  
  
  CONCLUSIONS
  Two strains of Beijing swine H1N1 influenza A virus were not reassortant, All the six internal gene segments were closely related to swine influenza A (H1N1) viruses.
authors.affiliation: Department of Influenza, 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: Ye
authors.initials: Y
authors.lastname: Zhang
authors.forename: Min
authors.initials: M
authors.lastname: Wang
authors.forename: Jun-feng
authors.initials: JF
authors.lastname: Guo
authors.forename: Zi
authors.initials: Z
authors.lastname: Li
authors.forename: Yue-long
authors.initials: YL
authors.lastname: Shu
mesh_terms: D000818:Animals; D002642:Chick Embryo; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*; D053127:Influenza A Virus, H9N2 Subtype / Q000235:genetics; D010802:Phylogeny; D012367:RNA, Viral / Q000235:genetics; D016865:Reassortant Viruses / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013552:Swine / Q000821:virology*
chemical_list: D018076:DNA, Complementary; D012367:RNA, Viral