Study Of Gene Vaccination Of Porcine Reproductive And Respiratory Syndrome

Seven plasmids against PRRSV were constructed.pIRESorf5/4 contained the ORF4 and ORF5 genes of PRRSV CH-1a.pIRESorf6/5 contained the ORF6 and ORF5 genes of PRRSV CH-1a.pIRESorf5/7 contained the ORF5 and ORF7 genes of PRRSV CH-1a.pIRESorf7/IFN-γ contained the ORF7 gene of PRRSV and porcine IFN-γ gene.pIRESorf5/IFN-γ contained the ORF5 gene of PRRSV and porcine IFN-γ gene.pIRESorf7/IL-2 contained the ORF7 gene of PRRSV and porcine IL-2 gene. pIRESorf5/IL-2 contained the ORF5 gene of PRRSV and porcine IL-2 gene.The foreign genes of these plasmids were expressed by IIF test of the Marc-145 cells transfected with the plasmids.Ten BALB/c mice were injected with plasmids pIRESorf5/4 and pIRESorf5/7.The antibodies against PRRSV were identified after the second inoculation.Thirty-day old, PRRSV-negative piglets were divided into 10 groups (three piglets per group),The piglets of each group were received the seven types of plasmids,pIRES1neo and inactivated vaccine respectiveiy.The inoculated pigs were injected with 400μg of recombinant of unaltered plasmid DNA,or with 2.0ml of inactivated vaccine by intramuscular injection every 2 weeks for a total of four inoculations.The recombinant plasmids and inactivated vaccine could induce humoral and cellular immunity of the pigs.The percentage of CD4~+ and CD8~+ increased at different extents.Two weeks later,every pig was challenged in nasally with 2.0ml of PRRSV cultures (~106TCID50/ml).One pig of pIRES1neo group and negative control group had a fever,and the body temperature exceed 40℃ in 20 days after challenge.The temperature of other pigs retain 38-39℃,Viscera of some pigs of immunized group and negative control group had special pathologic change,especially in pneumonia.The contribution of PRRSV in tissues of pigs of different groups was various. The recombinant plasmids could protect the pigs from PRRS disease at different extents, but could not prevent the infection of PRRSV.