Identification And Isolation Of High Pathogenic PRRSV NJ Strain And Noval Study For Inactivated Vaccine

Porcine reproductive and respiratory syndrome (PRRS) caused by Porcine reproductive and respiratory syndrome virus (PRRSV), is a serious infectious disease characterized by severe reproduction failure in sow and serious respiratory disturbance in piglets. PRRSV has restricted tropism for porcine alveolar macrophages and antigenicity variation, resulting in the high pathogenic in prevalence currently. The traditional commercial vaccines to prevent PRRS are mainly attenuated and inactivated vaccines. Although attenuated vaccines can provide solid protection against PRRSV, there exist dangers of reversion to more virulent strain. Compared with attenuated vaccine, inactived vaccine is safe, but its effect is not stable. Therefore, it is of great importance to develop efficiency vaccine that is safer, more effective and cheaper for PRRS prevention. Ths study is aimed to enhance the immune efficiency of PRRSV inactived vaccine through antigen treatment and immunoptentiator addition without change the production technology of the vaccine. This paper includes:1. Isolation and identification of high pathogenic PRRSV NJ StrainNJ strain of high pathogenic PRRSV has been identified from a farm in Nanjing in February,2011. From the dead piglets, PRRSV NJ strain was isolated from the extraction of spleen, lung, lymph nodes and brain tissue, which was validated with RT-PCR specific to PRRSV, at the same time, virus contamination was eliminated by RT-PCR or PCR specific to CSFV, PCV,PPV, JEVand PRV etc. Cytopathic effect was obvious following three blind passage on Marc-145 cells, and virus titer for the third generation of the virus was 106.5TCID5o/mL. Animal challenge test results demonstrated that the isolated virus is virulent highly pathogenic porcine reproductive and respiratory syndrome virus, and named the highly pathogenic PRRSV NJ strains,which could be used to produce inactived vaccine and used as virulent virus in animal challenge experiments.2. Establishment of highly pathogenic PRRSV real-time quantitative PCRA pair of specific primers was designed to establish a detection method of highly pathogenic PRRSV real-time quantitative PCR according to the highly pathogenic PRRSV genome sequences obtained from GenBank. Results showed that method in this chapter is able to detect the presence of highly pathogenic PRRSV standard curve covering the 1 × 104 copies to?1×109 copies/?l, and amplification efficiency of 99%. This method is fast, simple, sensitive, and has important practical value.3. Preliminary study for high pathogenic PRRS inactivated vaccineCommercialized attenuated and inactivated vaccine for high pathogenic PRRSV have been developed, but their safety or immunogenicity are still much to be desired. Classic inactived vaccine against high pathogenic PRRSV only partially protective, while inducing neutralizing antibody lately, and the antibody titer is low, can not produce cellular immunity. Attenuated vaccine for high pathogenic PRRSV is poor security, especially return to virulence is strong to become a major issue of concern. This test is designed to produce a high performance PRRS inactived vaccine which is superior to conventional inactivated vaccines through virus treatment and immunoptentiator addition. Fortunately, two kinds of immunoptentiator was found out which could protect 60%(3/5)pigs against virulent PRRSV challenge.