Cloning And Sequence Analysis Of The Patical Nsp2,ORF5～7 Gene And Research On Molecular Epidemiology Survey Of Porcine Reproductive And Respiratory Syndrome Virus In Guangxi

In this experiment,samples of serum,aborted fetus,fece,lung,lymphnode and kidney from different places of Guangxi were detected with porcine reproductive and respiratory syndrome virus(PRRSV)by RT-PCR,and 25 of the particle Nsp2,ORF5,ORF6,ORF7 gene were amplified from 2006 to 2008 on"Swine High Fever Disease".The particle Nsp2,ORF5,ORF6,ORF7 gene shared 77.1%～95.3%,81.9%～97.2%,92.0%～99.0%,85.2%～98.1% sequence homology with CH-1a,BJ-4,HB-1,HB-2,HN1 strains respectively for the nucleic acids,55.1%～94.0%;76.0%～95.0%,94.8%～98.9%,77.2%～96.0%similarity at the amino acids level;and shared 96.3%～99.3%,91.5%～99.7%,98.7%～100%,93.0%～100%sequence homology with JXA1,JX0612,HuN,HuN4,HuB1,HEB1respectively for the nucleic acids,74.7%～98.8%,84.1%～100%,97.7%～100%,83.7%～100%similarity at the amino acids level.It showed that 25 strains had higher identity with the JXA1,JX0612,HuN,HuN4,HuB1,HEB1 isolated from 2006～2007.Phylogenetically,all the 25 strains belong to the NA-type subgroupⅡ,and closely related to the JXA1,JX0612,HuN,HuN4,HuB1,HEB1.Therefor,the 25 strains and the Fatal PRRSV Variants maybe have a commom ancestor.In the Phylogentic tree of ORF5 gene,no significant correlation was observed between the geographic distribution of the viruses,but the GuangXi strains from 2003～2005 and the strains from 2006～2008 are not in the same clade of NA-typeⅡ,it found that the mutation in the 9aa,16aa,94aa,185aa between the 25 strains and JXA1,JX0612,HuN,HuN4,HuB1,HEB1 are identical,and the GuangXi strains from 2003～2005 have little mutation;it also found to be variable in the 54aa,59aa,104aa of strains from 2003～2005,but the 25 strains are not mutated.The R13,R151 in GP5 protein and the Q16 in M protein are considered to be involved in PRRSV attenuation,but the 25 strains are not mutated.All the strains were found to be high variable in PNE and mutated at L39→I39,and it also found deletions of 1 and 29 amino acids corresponded to positions 482 and 534～562 of strain VR-2332 in the Nsp2 Protein,but the deletion maybe not involved into the virulence of PRRSV.