[Origin of internal genes of two strains of swine influenza A (H1N1) virus].
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.
Guo
Yuan-ji
YJ
Department of Influenza, Institute of Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 100052, China.
Wen
Le-ying
LY
Zhang
Ye
Y
Wang
Min
M
Guo
Jun-feng
JF
Li
Zi
Z
Shu
Yue-long
YL
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*
D018076:DNA, Complementary; D012367:RNA, Viral