| As we know, pigs can be infected by both the human and avian influenza virus, beacuse there are two kinds of sialic acid receptor in pig’s upper respiratory tract (SAα-2,3-Gal and SAα-2,6-Gal). This is the reason why pigs are known as "mixing vessels". The H1N1 swine influenza virus outbreak in 2009 causing a human influenza pandemic and was introduced into pig herd soon afterwords. So far, there are various types of recombinant viruses exist in herd. It is of great significant for public health that control and prevention of SIV outbreak by intensifying the monitoring and understanding it’s biological characteristics.In order to clarify the pathogenicity of a novel recombinant H3N2 subtype SIV to pigs, we used two H3N2 subtype swine influenza virus strains for research, which namely A/Swine/Guangxi/NNXD/2013(H3N2) and A/Swine/ Guangxi/JG1/2013(H3N2). They all carrying the internal genes (PB2/PB1/PA/ NP/M) of pdm09 and the surface genes (HA and NA) of seasonal influenza virus. Use these two strains to challenge 10 piglets by intratracheal inoculation, each group of 4, and 2 as control. All the nasal swab are positive of influenza virus, which revealed the challenged pigs can detox through the nasal cavity. In 3 dpi and 5 dpi, both the JG1 and NNXD strains can replicate well in lung tissues, among which the JG1 group has a higher virus titer in lung (reached to 104 PFU/mL) and lung lavage (reached to 104.91 PFU/mL). The analysis of histopathology found the alveolar damage and inflammatory are more serious in JG1 group. It proved that JG1 is more pathogenic than NNXD in pigs.To explore the role of NS gene in swine pathogenic difference, the eight segments of NNXD and the NS segment of JG1 were synthesized by RT-PCR and cloned into bidirection expression vector pHW2000 respectively by a series of clone technology, forming the infectious recombinant plamids. And then we cotransfected 8 recombinant plasmids into 293T and MDCK co-cultured cell to rescue the rgNNXD and rgNNXD-JG1/NS. |
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