Construction and Humoral Immune Response of Recombinant Plasmid Co-Expressing GP3,GP5 and M Proteins of Porcine Reproductive and Respiratory Syndrome Virus

The aim of this study was to construct a recombinant eukaryotic plasmid co-expressing GP3,GP5 and M proteins of porcine reproductive and respiratory syndrome virus(PRRSV).GP3,GP5 and M protein gene fragments of PRRSV LN strain were amplified by PCR and cloned into vector pcDNA3.1(+) to produce the recombinant plasmid pcDNA3.1-GP3-GP5-M.The plasmid was transfected into COS7 cells,and immunological responses to the plasmid were investigated in BALB/c mice and piglets.The recombinant plasmid pcDNA3.1-GP3-GP5-M was transfected into COS7 cells,PCR identification and indirect immunofluorescence assay proved that GP3,GP5-M gene of PRRSV were expressed in COS7 cells.The result of Western blotting showed that the GP3 and GP5 and M proteins were co-expressed and formed fusion protein.The BALB/c mice were injected with recombinant plasmid pcDNA3.1-GP3-GP5-M to evaluate the induced immunological responses in vivo.The specific detectable anti-PRRSV neutralizing antibodies were produced in the vaccinated mice at 2 weeks and reached a peak 1:32 at 8 weeks after primary vaccination.In addition,it was observed that the 1:4-1:8 neutralizing antibodies of the vaccinated piglets.The results showed that the recombinant plasmid pcDNA3.1-GP3-GP5-M has been constructed successfully,and the recombinant plasmid has well immunity,the recombinant plasmid could be a basis to eukaryotic vector vaccine for PRRSV infection.