title: Thymic depletion of lymphocytes is associated with the virulence of PRRSV-1 strains.
abstract: Porcine reproductive and respiratory syndrome virus (PRRSV) exists as two distinct viruses, type 1 (PRRSV-1) and type 2 (PRRSV-2). Atrophy of the thymus in PRRSV-2 infected piglets has been associated with a loss of thymocytes. The present study aimed to evaluate the impact of PRRSV-1 strains of differing virulence on the thymus of infected piglets by analysing the histomorphometry, the presence of apoptotic cells and cells producing cytokines. Thymic samples were taken from animals experimentally infected (with LV, SU1-bel, and 215-06 strains) or mock inoculated animals at 3, 7 and 35days post-infection (dpi) and processed for histopathological and immunohistochemical analyses. PRRSV antigen was detected in the thymus from 3dpi until the end of the study in all virus-infected animals with the highest numbers of infected cells detected in SU1-bel group. The histomorphometry analysis and counts of CD3(+) thymocytes in the thymic cortex displayed significant differences between strains at different time-points (p≤0.011), with SU1-bel group showing the most severe changes at 7dpi. Cell death displayed statistically significant increase in the cortex of all infected animals, with SU1-bel group showing the highest rate at 3 and 7dpi. The number of cells immunostained against IL-1α, TNF-α and IL-10 were predominantly detected in the medulla (p≤0.01). An increase in the number of TNF-α and IL-10 positive cells was observed in LV and SU-1bel groups. Our results demonstrate that different PRRSV-1 strains induced depletion of the thymic cortex due to apoptosis of thymocytes and that the most severe depletion was associated with the highly virulent SU1-bel strain.
authors.affiliation: Department of Anatomy and Comparative Pathology, Faculty of Veterinary Medicine, Campus Universitario de Rabanales, 'International Excellence Agrifood Campus, CeiA3', 14071 Córdoba, Spain. Electronic address: ashyrleypaola@yahoo.com.
authors.forename: Shyrley Paola
authors.initials: SP
authors.lastname: Amarilla
authors.affiliation: CICAP-Food Research Centre, 14400 Pozoblanco, Córdoba, Spain.
authors.forename: Jaime
authors.initials: J
authors.lastname: Gómez-Laguna
authors.affiliation: Department of Anatomy and Comparative Pathology, Faculty of Veterinary Medicine, Campus Universitario de Rabanales, 'International Excellence Agrifood Campus, CeiA3', 14071 Córdoba, Spain.
authors.forename: Librado
authors.initials: L
authors.lastname: Carrasco
authors.affiliation: Department of Anatomy and Comparative Pathology, Faculty of Veterinary Medicine, Campus Universitario de Rabanales, 'International Excellence Agrifood Campus, CeiA3', 14071 Córdoba, Spain.
authors.forename: Irene M
authors.initials: IM
authors.lastname: Rodríguez-Gómez
authors.affiliation: Department of Statistics, Econometrics, Operations Research, Business Organization and Applied Economics, Faculty of Law and Economics, 14071 Córdoba, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Caridad Y Ocerín
authors.affiliation: Department of Virology, Animal and Plant Health Agency, Addlestone, Surrey, KT15 3NB, United Kingdom; Department of Pathology and Infectious Diseases, School of Veterinary Medicine, University of Surrey, Guildford GU2 7TE, United Kingdom.
authors.forename: Simon P
authors.initials: SP
authors.lastname: Graham
authors.affiliation: Department of Virology, Animal and Plant Health Agency, Addlestone, Surrey, KT15 3NB, United Kingdom.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Frossard
authors.affiliation: Department of Virology, Animal and Plant Health Agency, Addlestone, Surrey, KT15 3NB, United Kingdom; Department of Pathology and Infectious Diseases, School of Veterinary Medicine, University of Surrey, Guildford GU2 7TE, United Kingdom.
authors.forename: Falko
authors.initials: F
authors.lastname: Steinbach
authors.affiliation: Department of Pathology and Infectious Diseases, School of Veterinary Medicine, University of Surrey, Guildford GU2 7TE, United Kingdom.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Salguero
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000378:metabolism; D001284:Atrophy / Q000503:physiopathology / Q000821:virology*; D016923:Cell Death; D016207:Cytokines / Q000378:metabolism; D008214:Lymphocytes / Q000166:cytology / Q000821:virology; D019318:Porcine Reproductive and Respiratory Syndrome / Q000503:physiopathology / Q000821:virology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000472:pathogenicity*; D013045:Species Specificity; D013552:Swine; D060168:Thymocytes / Q000166:cytology / Q000821:virology*; D013950:Thymus Gland / Q000473:pathology / Q000821:virology*
chemical_list: D000956:Antigens, Viral; D016207:Cytokines
keywords: Apoptosis; Cytokine; Depletion; PRRSV-1; Thymus; Virulence