An indirect ELISA for the detection of antibodies against porcine reproductive and respiratory syndrome virus using recombinant nucleocapsid protein as antigen.

An indirect enzyme-linked immunosorbent assay termed rnPRRS ELISA using baculovirus-expressed and affinity-purified viral nucleocapsid protein (rNC) antigen was developed for detecting antibodies against porcine reproductive and respiratory syndrome virus (PRRSV) in swine sera. Sera (1395) originating from different European countries were used for the validation of this assay. The rnPRRS ELISA was capable of detecting antibodies in all sera known to contain anti-PRRSV antibodies, resulting in 100% sensitivity. The specificity was 95.8%. The rnPRRS ELISA was more sensitive compared to the most widely used tests for the diagnosis of porcine reproductive and respiratory syndrome (PRRS) (i) a commercially available ELISA; (ii) the indirect immunofluorescence assay (IIFA); and (iii) the immunoperoxidase monolayer assay (IPMA). The main advantage of the rnPRRS ELISA compared to an ELISA using whole virus antigen is the use of a single immunogenic protein instead of infectious PRRSV. The rnPRRS ELISA is suitable for routine diagnosis of PRRS and also for epidemiological surveys since it allows highly reliable testing of a large number of sera within a short period of time.