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Clinical and Vaccine Immunology, May 2009, p. 628-635, Vol. 16, No. 5
1071-412X/09/$08.00+0 doi:10.1128/CVI.00483-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Antibody Response to Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Nonstructural Proteins and Implications for Diagnostic Detection and Differentiation of PRRSV Types I and II
Elizabeth Brown,1,
Steven Lawson,1,
Craig Welbon,1
Josephine Gnanandarajah,2
Juan Li,2
Michael P. Murtaugh,2
Eric A. Nelson,1
Ramon M. Molina,3
Jeffery J. Zimmerman,4
Raymond R. R. Rowland,5 and
Ying Fang1*
Center for Infectious Disease Research and Vaccinology, Veterinary Science Department, South Dakota State University, Brookings, South Dakota 57007,1 Department of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, Minnesota 55108,2 Departmento de Ciencias Agronomicas y Veterinarias, Instituto Tecnologico de Sonora, Ciudad Obregon, Sonora, Mexico,3 Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Iowa State University, Ames, Iowa 50011-1250,4 Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas 665065
Received 19 December 2008/ Returned for modification 20 January 2009/ Accepted 24 February 2009
To further characterize the humoral immune response of pigs to porcine reproductive and respiratory syndrome virus (PRRSV), direct enzyme-linked immunosorbent assays (ELISA) were used to study the kinetics of antibody responses directed against PRRSV nonstructural proteins in pigs experimentally exposed to the virus. The highest immunoreactivities were against nsp1, nsp2, and nsp7. Using the recombinant nsp7 as an antigen, we validated a dual ELISA for the simultaneous detection and differentiation of serum antibodies against type I and type II PRRSV. Receiver operating characteristic analysis based on 1,334 known-positive and 1,357 known-negative samples showed good specificity (98.3% to type I and 99.3% to type II) and sensitivity (97.4% for type I and 99.8% for type II). To differentiate type I and type II PRRSV, 470 sera originating from experimentally inoculated pigs were tested, and positive sera were correctly differentiated in 469 of 470 samples. The capability of the nsp7 dual ELISA to detect serum antibody responses from pigs infected with various genetically different field strains was determined. The nsp7 dual ELISA possessed 97.6% agreement with the Idexx HerdChek PRRS 2XR ELISA. In further testing of Idexx ELISA suspected false-positive samples, the nsp7 dual ELISA resolved 98% of the samples as negative. Taken together, these results indicate that the nsp7 dual ELISA can be used as a differential test for PRRSV serology with high levels of sensitivity and specificity. This ELISA offers an additional tool for routine or follow-up diagnostics, as well as having substantial value in epidemiological surveys and outbreak investigations.
* Corresponding author. Mailing address: Center for Infectious Disease Research and Vaccinology, Department of Veterinary Science, Box 2175, South Dakota State University, Brookings, SD 57007-1396. Phone: (605) 688-6647. Fax: (605) 688-6003. E-mail: ying.fang{at}sdstate.edu
Published ahead of print on 4 March 2009.
E.B. and S.L. contributed equally to this study.
Clinical and Vaccine Immunology, May 2009, p. 628-635, Vol. 16, No. 5
1071-412X/09/$08.00+0 doi:10.1128/CVI.00483-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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