| A investigation in prevalence of swine influenza in Fujian province was fully completed in2010-2011.758serum samples were collected from29pig farms for testing the antibodies of H1,H3, H5and H9subtypes of swine influenza virus by ELISA and hemagglutination inhibition(HI)method. The results showed that: antibody positive rates of H1, H3and H9subtypes of swineinfluenza virus were44.5%(337/758),31.7%(240/758) and0.13%(1/758) respectively, antibodiesof H5subtype of swine influenza were negative.30specimens from25pig farms and8samples from2slaughterhouses were collected fordetecting swine influenza virus A and H1N1by fluorescence quantitative PCR and RT-PCRmethod. The results showed that: positive results of swine influenza virus A were observed in11of25pig farms, infected rate of swine farms was44.0%(11/25), positive results of swine influenzavirus A were observed in14of30specimens, which were collected from25swine farms,positive rate of specimens was46.7%(14/30). Negative results of swine influenza virus A wereobtained in the samples collected from2slaughterhouses. And negative results of H1N1virus wasfound in the specimens of pig farms and in the samples of slaughterhouses.The positive specimens were inoculated into SPF chicken embryo and swine influenza virus Astrain was isolated and named as A/Swine/Fujian/F1/2010(H1N2) after being identified by thevirus subtype molecular-biological characteristics. The isolated strain is classified to the type ofheat-unstable and its EID50is10-7.5/0.1mL. It could be inactivated by SDS, chloroform,formaldehyde and acid easily. After being challenged with the isolate, BALB/c mice and piglets of5weeks-old displayed some clinical symptoms of influenza infection. They were not lethal. Swineinfluenza virus A could be recovered from the challenged BALB/c mice.Sequencing the genome of A/Swine/Fujian/F1/2010(H1N2) strain, we knew that the isolated virusis composed of eight gene fragments and total nucleotides are13401. HA fragment containsseven potential glycosylated sites and has1709nucleotides. Other fragments are M, NA, NS, NP,PA, PB1, PB2and their nucleotides are991,1443,882,1543,2190,2302and2341, respectively.Compared to other H1N2virus, nucleotide homogeneity and amino acid homogeneity of HA, M,NA, NS, NP, PA, PB1, PB2fragments are90.9%~98.8%,90.3%~98.9%;96.5%~99.3%,98.4%~99.6%;96.0%~98.9%,95.5%~98.7%;95.9%~98.5%,93.7%~99.1%;96.6%~98.9%, 97.6%~99.8%;95.7%~98.6%,96.2%~98.1%;96.4%~99.0%,98.0%~99.1%;96.0%~99.0%,97.5%~98.9%, respectively.Phylogenetic analysis indicated that genetic relations of HA, M and PB1of the isolated strain arehighly closed to A/swine/Shanghai/1/2007(H1N2) strain; NA and PB2of the isolated strain arehighly closed to A/swine/Hubei/04/2009(H1N2) strain; NS of the isolated strain is highly closedto classic H1N1subtype of Swine influenza virus; NP and PA of the isolated strain are highlyclosed to H3N2subtype of Swine influenza virus.Conclusion: A new swine influenza virus was isolated from lungs and lymph nodes of clinicalpigs infected with swine influenza virus skeptically. The virus possess characteristic ofhemagglutination, and is highly pathogenic to chicken embryos. It was determined to be swineinfluenza virus H1N2subtype and named as A/Swine/Fujian/F1/2010(H1N2). Compared toGenBank publications and analysis of genetic evolution tree, we suggested that (1) gene fragmentsof NP, PB1, PB2, M and PA of the virus are recombined by swine influenza H3N2subtype virus;(2) HA gene fragment of the virus are recombined by classical swine influenza H1N1subtypevirus;(3) NA gene fragment of the virus are recombined by human influenza H3N2subtype virus;(4) NS gene fragment of the virus are recombined by human influenza H1N1subtype virus. Theresults indicated that this new strain is recombined with multiple-source. |
PDF Full Text Request