title: Commercial PCV2a-based vaccines are effective in protecting naturally PCV2b-infected finisher pigs against experimental challenge with a 2012 mutant PCV2.
abstract: Current commercial PCV2 vaccines are all based on PCV2a and have been shown to be effective in reducing PCV2a and PCV2b viremia and PCV2-associated lesions and disease. The recent emergence of novel mutant PCV2 (mPCV2) strains and linkage of mPCV2 with cases of porcine circovirus associated disease (PCVAD) in vaccinated herds have raised concerns over emergence of vaccine-escape mutants and reduced efficacy of PCV2a-based vaccines. The aim of this study was to determine the ability of three commercial PCV2a-based vaccines administered in the presence of an ongoing PCV2b infection and passively-acquired anti-PCV2 antibodies to protect conventional pigs against experimental challenge with mPCV2 at 11 weeks of age. Fifty naturally PCV2b-infected 2-week-old pigs were divided into five treatment groups with 10 pigs each. Pigs were unvaccinated (positive and negative controls) or vaccinated at 3 (VAC-A, VAC-B, VAC-C) and at 5 weeks of age (VAC-C). At 11 weeks of age, all pigs except the negative controls were challenged with a 2012 U.S. strain of mPCV2. The experiment was terminated 21 days after challenge. Under the conditions of this study, vaccinated pigs were protected against PCV2 viremia and lesions whereas non-vaccinated pigs were not. Moreover, concurrent PCV2b and mPCV2 infection was demonstrated in all positive controls and 3/10 had microscopic lesions consistent with PCVAD while negative controls infected with PCV2b alone did not develop PCVAD. The results indicate that concurrent PCV2b/mPCV2 infection can trigger PCVAD development and that commercial vaccines are effective in protecting conventional pigs against emerging mPCV2 strains.
authors.affiliation: The Roslin Institute and The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK; Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA. Electronic address: Tanja.Opriessnig@roslin.ed.ac.uk.
authors.forename: Tanja
authors.initials: T
authors.lastname: Opriessnig
authors.affiliation: Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.
authors.forename: Priscilla F
authors.initials: PF
authors.lastname: Gerber
authors.affiliation: Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.
authors.forename: Chao-Ting
authors.initials: CT
authors.lastname: Xiao
authors.affiliation: Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Halbur
authors.affiliation: Department of Biomedical Sciences and Pathobiology, Center for Molecular Medicine and Infectious Diseases, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
authors.forename: Shannon R
authors.initials: SR
authors.lastname: Matzinger
authors.affiliation: Department of Biomedical Sciences and Pathobiology, Center for Molecular Medicine and Infectious Diseases, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
authors.forename: Xiang-Jin
authors.initials: XJ
authors.lastname: Meng
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D018173:Circoviridae Infections / Q000517:prevention & control / Q000662:veterinary*; D017925:Circovirus / Q000276:immunology* / Q000502:physiology; D004279:DNA, Viral / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D013552:Swine; D013553:Swine Diseases / Q000517:prevention & control*; D014765:Viral Vaccines / Q000276:immunology*; D014766:Viremia / Q000517:prevention & control; D014779:Virus Replication
chemical_list: D000914:Antibodies, Viral; D004279:DNA, Viral; D007074:Immunoglobulin G; D014765:Viral Vaccines
keywords: Genotypes; Mutant PCV2; PCV2; Porcine circovirus; Vaccination; Vaccine efficacy