An indirect ELISA based on recombinant nucleoprotein for detection of antibodies to porcine reproductive and respiratory syndrome virus

PRRSV The recombinant nucleoprotein was expressed by E.coli and purified through high-salt washing method.Using purified nucleoprotein, an indirect ELISA for detection of anti-PRRSV antibodies was developed and its optimal reaction conditions were determined: coating antigen for 37℃1 hour and 4℃ overnight at a concentration of 0.27 μg/ml, serum sample(1∶40) and HRP labeled anti-porcine IgG being incubated at 37℃for 30 min, the substrate for ELISA being incubated at 37℃ for 15 min. The ELISA assay was confirmed to have a good reiterativity, specificity and sensitivity by reiterativity test. cross test and blocking test. And Compared with the IDEXX Test kit, the specificity and sensitivity of the ELISA is 97.6% and 92.1% respectively, which showed no significant difference between the two assays. In addition, 187 serum samples collected from swine farms were detected by the developed assay ,it was showed that the positive rate was 30.5%.for antibody against PRRSV.