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Clin. Vaccine Immunol. doi:10.1128/CVI.00332-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Use of an experimental model to test the efficacy of planned exposure to live porcine reproductive and respiratory syndrome virus (PRRSV)

Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA

^* To whom correspondence should be addressed. Email: tanjaopr{at}iastate.edu.

	Abstract

The objectives of this study were to test the efficacy and safety of planned exposure to porcine reproductive and respiratory syndrome virus (PRRSV) in protecting naïve and previously exposed pigs against PRRSV challenge and to gain information on the dose of PRRSV necessary to induce a protective immune response. Fifty, two-week-old pigs were randomly assigned to one of five groups: L-VAC, H-VAC, SDSU73-L-VAC, SDSU73-H-VAC, and CONTROLS. Two groups were exposed to a heterologous PRRSV (SDSU73) prior to planned expose. Two groups received a low (L) and two groups received a high (H) dose of a homologous or heterologous PRRSV isolate. All groups were challenged with PRRSV VR2385 5 weeks after planned exposure. Necropsy was done 2 weeks after PRRSV challenge. H-VAC, SDSU73-L-VAC, and SDSU73-H-VAC had significantly (P < 0.05) less severe clinical disease (sneezing, respiratory scores, and weight gain), significantly (P < 0.05) less severe macroscopic and microscopic lung lesions, and significantly (P < 0.05) lower numbers of PRRSV-genomic copies in sera compared to the CONTROL group. Planned exposure to live PRRSV can be used as an inexpensive and effective way to decrease the severity of PRRSV-induced disease following subsequent challenge.