Development and validation of an immunogold chromatographic test for on-farm detection of PRRSV

An immunochromatographic test strip was developed to detect porcine reproductive and respiratory syndrome virus (PRRSV). The test uses two gold-labeled monoclonal antibodies: D5 against recombinant nucleocapsid protein (rN) and E9 against recombinant M protein (rM). In the test, PRRSV binds to a mixture of D5 and E9 labeled with colloidal gold; the complexes move through a membrane and are captured by rabbit anti-rM and anti-rN antibodies at a test line, producing a reddish-purple band because of the increased concentration of gold. Unbound monoclonal antibodies move past the test line to be captured by goat anti-mouse antibodies, producing a band at a control line. In samples without PRRSV or with low virus concentration, a band appears only at the control line. A crossover-trial demonstrated that the test strip was highly specific for PRRSV. The test strip detection limit was between 7.8x10(3) and 1.6x10(4) TCID(50)/ml. Analysis of 100 clinical samples indicated that the sensitivity, specificity, and accuracy of the immunochromatographic test strip relative to reverse transcription polymerase chain reaction (RT-PCR) were 97.0, 93.9, and 96.0%, respectively. Because the test is simple and rapid, it can be used by an unskilled person to detect PRRSV in the field.