Epidemiological Investigation In Jilin Area And Construction Of Eukaryotic Vaccine And Immunogenicity Of Porcine Reproductive And Respiratory Syndrome Virus (PRRSVC)

Infection and antibody lever of PRRSV were investigated by using method of PRRSV special antibody ELISA in Large-scale pig farm of jilin area in study.268 serum samples were detected with PRRSV special antibody in PRRSV immune pig farms and 232 serum samples were detected with same method in unimmune pig farms.The Results show PRRSV in Large-scale pig farm of some unimmune PRRSV vaccine had higher infection rate which is 50%-75%.Serum antibody positive rate of immuned PRRSV vaccine is 66.67%-100% in Large-scale pig farm.The difference of serum positive rate of different age pig were discovered in this survey, serum positive rate of group of gilts was the highest. serum positive rate of 5～10 weeks days weaning piglet was the lowest. serum positive rate of sows which could produce piglets was higher than weaning piglets, less than gilts.GP5 gene of PRRSV positive materials was cloned and analysed, the results demonstrate that the GP5 protein gene is approximately 603bp in length and code polypeptide which contains 201 amino acid. compared to VR-2332 srain and LV strain nucleotide, homology was respectively 91.6% and 48.7%, homology of coding amino acid was respectively 87.6% and 60.0%. PRRSV JL/07/SW strain GP5 gene which was isolated by laboratory of author was higher homology with American VR-2332 strain GP5 gene, less than European LV strain GP5 gene. PRRSV JL/07/SW isolation strain was American strain. It is worth mentioning that amino acid sequence of PRRSV JL/07/SW strain GP5 gene was higher homology with BJ-4 which was isolated for the first time in china. It show that PRRSV JL/07/SW and BJ-4 may come from the same strains or mutant strain.To futher study immune function of PRRSV GP5 protein, Recombinant plasmid DNA vaccine(pEGFP-GP5) of single expressing PRRSV GP5 gene was successfully constructed by pEGFP-N1 vector which contains reporter gene(EGFP) and PRRSV JL/07/SW GP5 gene which was as interested gene. All piglets were given booster vaccinations at 21 days after the initial inoculation. Constructed vaccine was evaluated for theirs abilities to induce humeral and cellular responses in piglets. The immunogenicities of DNA vaccine construct was evaluated in piglets. Compared to commercial application of the different types of PRRSV vaccine. All piglets were inoculated two times, given booster vaccinations at 28d after the first inoculation(21d), given inoculation at 0 days and 28 days. The results showed that the piglets inoculated with recombinant plasmid DNA vaccine (pEGFP-GP5) could produce specific ELISA antibody and neutralizing antibodies, neutralizing antibodies titers of Induced in pigs after immunization range from 1:3.44 to 1:10.99. The results of cell-mediated immunity detection showed that the production of IFN-y in the pigs immunized with pEGFP-GP5 were significantly higher than PEGFP-N1, and the number of CD4+ and CD8+ T-lymphocyte and special T-lymphocyte proliferation response were significantly increased immunized with pEGFP-GP5 than PEGFP-N1 (P<0.05).The results showed that recombinant plasmid DNA vaccine of expressing PRRSV GP5 protein could induce TH1 Cell-mediated immune response.The results of study showed that GP5 nucleic vaccine of PRRSV had Stronger immunogenicity, and could produce special humeral and cellular responses by inducing body. This study will provide foundation for developing new PRRSV vaccines.