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.
Conclusion: 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.