title: Correlates of Protection Following Vaccination with Inactivated Porcine Circovirus 2 Vaccines.
abstract: Porcine circovirus type 2 (PCV2) is associated with a number of diseases and syndromes, collectively referred to as porcine circovirus-associated disease. The main objective of this study was to define some in vitro correlates of protection after injection of inactivated PCV2 vaccines with a defined antigen mass. Twelve pigs were vaccinated with three different doses of inactivated, whole-virus antigen (211-844 ng), while four animals were injected with a commercial vaccine (positive control) and four other pigs were mock-vaccinated with phosphate-buffered saline (PBS) in the same oil emulsion. Four weeks later, they were intranasally challenged with 2 × 10(5) TCID50 of a PCV2a strain. Antibody was measured in blood and oral fluids by enzyme-linked immunosorbent assay (ELISA) and a neutralization assay. PCV2 was quantified in serum by real-time polymerase chain reaction for ORF2 gene. PCV2-specific cell-mediated responses were investigated by an IFN-γ release assay in whole blood, IFN-γ ELISPOT, and lymphocyte proliferation (Ki-67 and BrDU assays). All the vaccines under study but mock provided complete or incomplete protection from PCV2 infection in terms of post-challenge viremia. Serum antibody titers (ELISA and neutralizing) after vaccination were not correlated with protection, as opposed to the early neutralizing antibody levels of vaccinated pigs at day 7 after infection. Cell-mediated immune parameters showed a good correlation with vaccine efficacy. In particular, the IFN-γ release assay at 3 weeks after vaccination was an effective marker for predicting protection. All control pigs always tested negative in assays of cell-mediated immunity. Our results outline in vitro testing procedures toward reduced animal usage in the control of PCV2 vaccine batches.
authors.affiliation: 1 Laboratory of Cellular Immunology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia-Romagna , Brescia, Italy .
authors.forename: Cinzia
authors.initials: C
authors.lastname: Zanotti
authors.affiliation: 2 Laboratory Animal Medicine, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia-Romagna , Brescia, Italy .
authors.forename: Nicola
authors.initials: N
authors.lastname: Martinelli
authors.affiliation: 3 Department of Virology; Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia-Romagna , Brescia, Italy .
authors.forename: Davide
authors.initials: D
authors.lastname: Lelli
authors.affiliation: 1 Laboratory of Cellular Immunology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia-Romagna , Brescia, Italy .
authors.forename: Massimo
authors.initials: M
authors.lastname: Amadori
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000032:analysis / Q000097:blood; D015415:Biomarkers / Q000032:analysis; D001769:Blood / Q000276:immunology; D049109:Cell Proliferation; D018173:Circoviridae Infections / Q000517:prevention & control / Q000662:veterinary*; D017925:Circovirus / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D058501:Enzyme-Linked Immunospot Assay; D007371:Interferon-gamma / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000276:immunology; D009500:Neutralization Tests; D010865:Pilot Projects; D012463:Saliva / Q000276:immunology; D013552:Swine; D013553:Swine Diseases / Q000517:prevention & control*; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology; D014765:Viral Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D014766:Viremia / Q000517:prevention & control
chemical_list: D000914:Antibodies, Viral; D015415:Biomarkers; D015164:Vaccines, Inactivated; D014765:Viral Vaccines; D007371:Interferon-gamma