title: A commercial porcine circovirus (PCV) type 2a-based vaccine reduces PCV2d viremia and shedding and prevents PCV2d transmission to naïve pigs under experimental conditions.
abstract: Porcine circovirus type 2 (PCV2) vaccination has been effective in protecting pigs from clinical disease and today is used extensively. Recent studies in vaccinated populations indicate a major PCV2 genotype shift from the predominant PCV2 genotype 2b towards 2d. The aims of this study were to determine the ability of the commercial inactivated PCV2a vaccine Circovac® to protect pigs against experimental challenge with a 2013 PCV2d strain and prevent transmission. Thirty-eight pigs were randomly divided into four groups with 9-10 pigs per group: NEG (sham-vaccinated, sham-challenged), VAC (PCV2a-vaccinated, sham-challenged), VAC+CHAL (PCV2a-vaccinated and PCV2d-challenged), and CHAL (sham-vaccinated, PCV2d-challenged). Vaccination was done at 3weeks of age using Circovac® according to label instructions. The CHAL and VAC+CHAL groups were challenged with PCV2d at 7weeks of age and all pigs were necropsied 21days post-challenge (dpc). The VAC-CHAL pigs seroconverted to PCV2 by 21days post vaccination (dpv). At PCV2d challenge on 28dpv, 3/9 VAC and 1/9 VAC+CHAL pigs were seropositive. NEG pigs remained seronegative for the duration of the study. Vaccination significantly reduced PCV2d viremia (VAC+CHAL) at dpc 14 and 21, PCV2d fecal shedding at dpc 14 and 21 and PCV2d nasal shedding at dpc 7, 14 and 21 compared to CHAL pigs. Vaccination significantly reduced mean PCV2 antigen load in lymph nodes in VAC+CHAL pigs compared to CHAL pigs. When pooled serum or feces collected from VAC+CHAL and CHAL pigs at dpc 21 were used to expose single-housed PCV2 naïve pigs, a pooled fecal sample from CHAL pigs contained infectious PCV2 whereas this was not the case for VAC+CHAL pigs suggesting reduction of PCV2d transmission by vaccination. Under the study conditions, the PCV2a-based vaccine was effective in reducing PCV2d viremia, tissue loads, shedding and transmission indicating that PCV2a vaccination should be effective in PCV2d-infected herds.
authors.affiliation: The Roslin Institute and The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, Scotland, 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; College of Biology, Hunan University, Changsha, China.
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: The Roslin Institute and The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, Scotland, UK.
authors.forename: Priscilla F
authors.initials: PF
authors.lastname: Gerber
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; D001769:Blood / Q000821:virology; D018173:Circoviridae Infections / Q000473:pathology / Q000517:prevention & control / Q000662:veterinary*; D017925:Circovirus / Q000276:immunology*; D005243:Feces / Q000821:virology; D008198:Lymph Nodes / Q000821:virology; D011897:Random Allocation; D000069078:Seroconversion; D013552:Swine; D013553:Swine Diseases / Q000517:prevention & control*; D013997:Time Factors; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology; D014765:Viral Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D014766:Viremia / Q000517:prevention & control / Q000662:veterinary; D017201:Virus Shedding
chemical_list: D015164:Vaccines, Inactivated; D014765:Viral Vaccines
keywords: PCV2; PCV2d; Porcine circovirus; Transmission; Vaccination; Vaccine efficacy