| In March 2009, the 2009 pandemic H1N1 influenza A virus broke out in Mexico, in April, the first strain was isolated, since then more and more reports showed that the 2009 pandemic H1N1 influenza A virus has transmitted from human to swine. Later researches found that there is substantial evidence that the 2009 pandemic H1N1 influenza A virus is novel reassortant influenza virus of swine, avian and human influenza viral RNA segments, which causes significant economic losses to livestocks and poses a serious threat to human lealth. Therefore, the public health concern calls for epidemiological investigation and careful surveillance to H1N1 influenza viruses in province. During January 2013 to December 2014, swime influenza investigation was carried out in farms and infected swinery in Guangxi to isolate viruses in this study, in order to obtain the SIV strains and understand the subtypes, genetic variation and stealth infection of SI in this region, which provide important reference data for the SI research and prevention. The experiment obtained the following results:1. Twelve H1N1 SIVS were isolated and identified from infected swinery, one of these was determined as 2009 influenza A(H1N1) virus.1609 Nasal/tracheal swap samples were collected form infected swinery in farms in Guangxi eight areas between January 2013 and December 2014. The samples were separated by 9-11 days SPF chiken embryos affter conventional treatment and obtained twelve SIVS, the HA and NA gene were sequenced using RT-PCR identified as H1N1 subtype influenza viruses, one of these was determined as swine-origin 2009 influenza A(H1N1) virus, it will as the objects of this study which was named A/swine/Guangxi/18/2013(H1N1).2. Phylogenetic analysis showed that the eight gene segments of the isolate that evolutionary relationship is consistent with other 2009 influenza A(H1N1) viruses. Eight gene segments of the strain were amplifid, cloned and sequencing and obtained the complete genome sequences, then comparison and analysis of the nucleotide and amino acid variation by MegAlign software, and evolutionary trees were builded by MEGA5.0 software. The results showed that the strain and 2009 influenza A(H1N1) viruses were located into the same clade, and it had high similarity with A/California/04/2009(H1N1), which suggest that they originated from a common ancestor. The gene HA, NS and NP from classical H1N1 swine lineage, NA and M from avain-like H1N1 swine lineage, PA and PB2 from avian lineage, PB1 stemmed from H3N2 human lineage. The mutated amino acid of the isolate strain were detected at receptor binding sites, potrntial glycosylation sites and resistant sites, will have affected the antigenicity, host adaptability, virulence and drug resistence of the virus.3. Experiment on mice showed that the isolate strain had pathogenicity to BALB/c mice. For BALB/c mice inoculated intranasally with virus of the experimental result showed that the virus can infected in mice, and can be effectively replicated in lung and turbinate tissue, cause obvious clinical symptoms after infection, what’s more, falling weight quickly and the highest average weight decreased by 13.02% in mice. |
