A Chimeric Porcine Circovirus PCV1-2 Live Virus And Recombinant Plasmid Induces Protective Immunity In Commercial Pigs And The Development Of Indirect Immunofluorescence Assay For PCV2 Specific Antibody Detection

Porcine circovirus type 2(PCV2) is the primary causative agent and a recently recognized pathogen of postweaning multisystemic wasting syndrome (PMWS) and other associated dieases. PMWS was initially recognized in weaning piglets of a high-health-status Canadian herd in 1991, since then PMWS has become an economically important disease in virtually all regions of the world where pigs are produced. The most common clinical signs are unthriftiness wasting, dyspnea, enlarged lymphnodes, diarrhea, pallor and jaundice.At present, effective vaccine which can effectively control PCV2 are researched at home and abroad. Some vaccines have been put into clinical experiment and evaluation of immune effect. In this study, a chimeric virus PCV1-2 live virus and the recombinant eukaryotic expression vector pcDNA3.1/V5-His-orf2 were vaccinated in commercial pigs. Comprehensive evaluation on commerical pigs immunized with PCV1-2 live virus and pcDNA3.1/V5-His-orf2 was responsible for the purpose of the commercialisation of these vaccines. In other hand, the development of indirect immunofluorescence assay was also carried out, which aimed to detect the PCV2 specific antibodies.1 A chimeric porcine circovirus PCV1-2 live virus and the recombinant plasmid expressing the major nucleocapsid gene of PCV2 induces protective immunity in commercial pigsA chimeric virus PCV1-2 live virus and the recombinant eukaryotic expression vector pcDNA3.1/V5-His-orf2 were vaccinated in commercial pigs with maternal antibody titers determined by ELISA varied from 0.07 to 0.60. A total of 9 pigs were randomly assigned to four groups. Pigs in group 1 were vaccinated by intramuscular injection with 10 3.5 50% tissue culture infective doses (TCID50) of the chimeric PCV1-2 live virus. Pigs in group 2 were vaccinated by intramuscular injection with 200μg of recombinant plasmid. Pigs in group 3 were vaccinated by intramuscular injection with 200μg of pcDNA3.1. Pigs in group 4 were served as challenge control. By 42 days post-vaccination (DPV), pigs in group 1 and group 2 had seroconverted to PCV2 capsid antibody. At 42 DPV, all pigs were challenged intramuscularly with 2×104.5 TCID50 of pathogenic PCV2 virus and 106 TCID50 of PRRSV virus. Necropsies were performed at 21 days post-challenge, the lymph nodes in the non-vaccinated but challenged pigs were larger than those of vaccinated pigs. The PCV2 genomic copy loads in lymph nodes were reduced in vaccinated pigs. Moderate amounts of PCV2 antigen were detected in most lymphoid tissues of nonvaccinated pigs. These data indicated that when given intramuscularly in pigs, the chimeric PCV1-2 live virus and recombinant plasmid induces protective immunity against PCV2 infection and could potentially serve as an effective vaccine.2 The development of indirect immunofluorescence assay for PCV2 specific antibody detectionDulac cells inoculated with PCV2 virus and passaged repeatly were spread into wells of 96-cell culture plate. Serum samples were diluted serially and added into wells mentioned above, the titers of PCV2 specific antibody were determined by indirect immunofluorescence assay. No cross-reations were observed between the antibody against PCV2 and the antibodies specific to classical swine fever(CSF), pseudorabies (PR), porcine parvovirus (PPV), porcine reproductive and respiratory syndrome (PRRS). 172 clinical sera were detected by IFA and the result was consistant with that detected by ELISA kit provided by Zhejiang University. The indirect immunofluorescent assay established in this study can be used to detect PCV2 specific antibodies.