title: Use of an experimental model to test the efficacy of planned exposure to live porcine reproductive and respiratory syndrome virus.
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 2-week-old pigs were randomly assigned to one of five groups: a group exposed to a low dose of autogenous PRRSV vaccine (the L-VAC group), a group exposed to a high dose of autogenous vaccine (the H-VAC group), a group exposed to a low dose of a heterologous PRRSV strain (strain SDSU73) prior to planned exposure (the SDSU73-L-VAC group), a group exposed to a high dose of a heterologous PRRSV strain (strain SDSU73) prior to planned exposure (the SDSU73-H-VAC group), and a control group. All groups were challenged with PRRSV VR2385 5 weeks after the planned exposure. Necropsy was done 2 weeks after the PRRSV challenge. The H-VAC, SDSU73-L-VAC, and SDSU73-H-VAC groups 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 copy numbers in their sera compared to the results for 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.
authors.affiliation: Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA. tanjaopr@iastate.edu
authors.forename: Tanja
authors.initials: T
authors.lastname: Opriessnig
authors.forename: Rodney B
authors.initials: RB
authors.lastname: Baker
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Halbur
mesh_terms: D000281:Administration, Intranasal; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D035061:Control Groups; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D018628:Gene Dosage; D009500:Neutralization Tests / Q000662:veterinary; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification / Q000472:pathogenicity; D012367:RNA, Viral / Q000097:blood / Q000302:isolation & purification; D011897:Random Allocation; D012307:Risk Factors; D012698:Serologic Tests / Q000662:veterinary; D034421:Sus scrofa; D013553:Swine Diseases / Q000097:blood / Q000276:immunology* / Q000473:pathology / Q000517:prevention & control* / Q000821:virology; D013997:Time Factors; D016896:Treatment Outcome; D014765:Viral Vaccines / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology* / Q000627:therapeutic use*; D014766:Viremia
chemical_list: D000914:Antibodies, Viral; D012367:RNA, Viral; D014765:Viral Vaccines