Epidemiogical Investigation Of PRRSV In Parts Of Southern China And Prokaryotic Expression Of Nsp1α And Nsp1β

To analyze the genetic variation and survey the antibody level of PRRSV in Southern China from 2014 to 2015, in this experiment, we respectively detected the PRRSV antibody and antigen in serum and pathological samples collected during 2014 to2015 from Southern China. Test results showed that, In 2014 year, we collected 5046 serum samples, the PRRSV antibody positive samples was 4195,the positive rate was83.13%(4195/5046), 95% confidence interval was 82.67%-83.59%. In 2015 year, we collected 5531 serum samples, the positive samples was 3992, the positive rate was 72.18%(3992/5531), 95% confidence interval were 70.38%-72.4%. In 2014 year, we collected 583 samples, the PRRSV positive sample was 192, the antigen positive rate was 33.01%(192/583), 95% confidence interval were 32.78%-33.23%. In 2015 year, we collected 964 samples, the PRRSV positive sample was 356, the antigen positive rate was 36.88%(356/964), 95% confidence interval were 36.56%-37.2%. Compared with 2014, the positive rate of antibody decreased while the positive rate of antigen increased in 2015.Amplification of Nsp2 and GP5 genes in PRRSV positive samples, 31 Nsp2 sequences and 64 GP5 sequences were successfully obtained. Amino acid analysis results showed that26 of 31 Nsp2 genes contained 29+1 aa deletions, but there were also some other forms of deletions in Nsp2. Compared with reference strains, GP5 genes had a wide range of amino acid mutations, the main mutation domain were Signal peptide region, HVR1 and HVR2.GP5 phylogenic analysis revealed that Southern China existing both type I and type II PRRSV, type II PRRSV further divided into six subgenotypes, the main epidemic subgenotypes in Southern China were Subgenotype I and Subgenotype VI represented with JXA1 strain and GM2 strain, respectively.Ten strains of PRRSV were isolated and identificated, the nucleotide homology between ten strains was 92.6%-97.5%, the nucleotide homology with JXA1, VR2332 andCH-1R were 95.3%-98.9%, 87.8%-89.15%, 91.5%-94.9%, respectively. The complete genome phylogenetic tree showed that ten strains except FJXM strains all belonged to JXA1-like subgroup and had a closely relationship with each other, while the FJXM strain belonged to Intermediate subgroup. Compared with reference strains, the antigen epitope of GP3, GP5 and GP6 proteins had some amino acid mutation sites.Amplification of the Nsp1α and Nsp1β genes of PRRSV and connected to p ET-28 a expression vector, then the recombinant plasmid were transformed into BL21 competent cells, finally, the PRRSV Nsp1α and Nsp1β proteins were successfully expressed in E.coli,meanwhile we also optimize the expression conditions, this will provide a material basis for further study of Nsp1α and Nsp1β proteins.