Comparison Of Three ELISAs To Detect Antibo-dies And Establishment Of A Indirect ELISA To Detect IgM Antibodies Against Porcine Reproductive And Respiratory Syndrome Virus (PRRSV)

One of the objective of the study is to determine the consistency of the established N-ELISA and 2 commercial ELISAs (LSI and IDEXX ELISA kits) for detecting IgG antibodies against PRRSV. The 3 ELISAs detected 544 clinical serum samples,147 serum samples from farms A, B and C,397 serum samples from laboratory. It was showed that the coincidence rate between the N-ELISA and IDEXX ELISA kit was 96.0% agreement, indicating that the positive coincidence rate was 96.1%, and negative coincidence rate was 95.7%; the coincidence rate between the N-ELISA and LSI ELISA kit was 86.6% agreement, indicating that the positive coincidence rate was 88.3% and negative coincidence rate was 82.2%. The results suggested that the established N-ELISA had better consistency to IDEXX ELISA kit, and the established N-ELISA could be used for detecting IgG antibodies against PRRSV.The recombinant N protein was used to establish a indicate ELISA (N protein based antibody indicate ELISA, NBI-ELISA) for detecting IgM antibodies against PRRSV. The NBI-ELISA showed good specificity and sensitivity, which can be detected IgM antibodies against PRRSV 7 days post immunization. Compare of NBI-ELISA and indicate immunofluorescence assay (IFA), NBI-ELISA have many advantages, such as easier of operator, shorter, lower and requirements for instrument. The N-ELISA and NBI-ELISA provided reference data for generalizing the recombinant N protein.The NBI-ELISA and IDEXX ELISA kit were applied to investigate the characteristic of PRRSV infection and antibody production in 3 large scale pig farms. The results showed that there was obvious difference in profiles IgG antibodies against PRRSV and IgM antibodies against PRRSV between swinery naturally infected with PRRSV and swinery immunized with PRRS vaccine. The sample-to positive peak value of IgG antibodies against PRRSV and IgM antibodies against PRRSV in swinery which immunized with PRRS vaccine were higher than non immunized with PRRS vaccine. Comparion of NBI-ELISA and IDEXX ELISA kit, IgM antibodies against PRRSV could be detected about 7 days before IgG antibodies against PRRSV, and NBI-ELISA could be used to diagnosis swinery naturally infected with PRRSV and swinery immunized with PRRS vaccine earlier.