Immune Effect Of A Recombinant Plasmid Of Porcine Reproductive And Respiratory Syndrome Virus E Gene

Porcine reproductive and respiratory syndrome (PRRS) caused by PRRS virus (PRRSV) is a severe infectious disease in swine herds characterized by reproductive failure in sows and respiratory illness in piglets. The E protein is the key immunogenic protein of PRRSV with an epitope relative to virus neutralization, which plays a key role in immune response. The E gene of PRRSV is considered as the first selection gene for subunit vaccine, recombinant viral living-carrier vaccine and DNA vaccine.This study was designed to explore the immunogenicity of E gene, whether it can induce specific antibodies and neutralizing antibodies. The plasmid of eukaryotic expression vector pIRES-E was constructed and was purified and then used to inoculate rabbits together with the plasmid of empty pIRESneo, PRRS attenuated vaccine and normal saline. In addition, PRRSV GXA strain was propagated on Marc-145 cells. Virus was harvested after the cells were observed CPE and the virus titer (TCID₅₀) was examined. Eighteen male rabbits(1.5～2.0 kg in weight) were randomly assigned to five groups. Four rabbits in groups were each inoculated with 200μg of pIRES-E and empty pIRESneo vectors respectively. 1 mL normal saline of per rabbit were given to four rabbits in group. Three rabbits in group were each inoculated 0.5 mL of PRRS attenuated vaccine. Three rabbits in group were each inoculated 1 mL of PRRS attenuated vaccine. All rabbits were inoculated through hind leg muscles and boosted twice at 2-week intervals. Serum samples were collected at different times from the immunized rabbits and tested the level of specific antibodies and neutralizing antibodies by indirect ELISA and neutralizing experiment. The results showed that not only the anti-PRRSV E specific antibodies was induced by the plasmid pIRES-E but also neutralizing antibodies were detected in three rabbits.In this study, using the plasmid of eukaryotic expression vector pIRES-E to immunize rabbits can induce anti-PRRSV E protein specific antibodies and neutralizing antibodies. These results further verify the immunogenicity of E gene and show some immune effect of pIRES-E. This study lays a foundation of further study on the novel vaccine development of PRRS.