Genomic analysis of one Chinese H1N1 swine influenza virus strain fron healthy pig remaining different virulence determinants

The outbreak of Mexico flu pandemic in the Spring of 2009 has arisen the public attention to swine H1N1 influenza virus because H1N1 influenza virus did not bring a large-scale outbreak in human after causing 1 918 Spain flu pandemic. Researchers isolated one swine influenza virus strain A/swine/Guangdong/103/2002 (H1N1) from healthy pig in South China and sequenced its full-length genome. BLASTn analysis showed that all segments of the isolate had the above 99% similarities with A/swine/Shanghai/1/2005, A/swine/Shanghai/2/2005 and A/swine/Shanghai/3/2005 from the severe outbreak of respiratory disease pigs. Although, these four virus strains have high similarities they showed very different virulence. The H1N1 virus could replicate in pigs and mousse without causing clinical symptoms according to the animal regressive experiments results. None of the amino acid substitutions were reported to contribute in the pathogenicity of human and avian influenza viruses providing the basis for virulence determinants research by means of reverse genetics.