title: Experimental infection of lambs with C and S-type strains of Mycobacterium avium subspecies paratuberculosis: immunological and pathological findings.
abstract: The two main genotypes of recognized isolates of Mycobacterium avium subsp. paratuberculosis (Map) are cattle (C) and sheep (S) strains. An experimental infection was conducted to establish the effect of Map strain on the pathogenesis of ovine paratuberculosis. Twenty-four out of thirty 1.5-month-old Assaf lambs were divided into 4 groups of 6 and infected orally with three low passage field isolates, two of S- (22G and the pigmented Ovicap49) and one of C- (764) type, and the reference K-10 strain (C type). The remaining six animals were unchallenged controls. Animals were euthanized at 150 and 390 days post-infection (dpi). Throughout the experiment, the peripheral immune response was assessed and histological and molecular (PCR) studies were conducted on samples of intestine and related lymphoid tissue. Specific antibody and IFN-γ production was significantly higher in animals infected with the C strains, while no consistent IFN- γ responses were observed in the S-type strain infected groups. A positive intradermal skin test response was detected in all infected groups. Lambs infected with S-type strains had granulomatous lesions restricted to the lymphoid tissue with no differences in the lesion intensity over time. In both C-type strain groups, lesions were more severe at 150 dpi while at 390 dpi lesions, characterized by well-demarcated granulomas with fibrosis, decreased in severity. Only infected lambs were positive to PCR. These results suggest that the strain of Map has a strong influence over the immune and pathological responses developed by the host. Lesions induced by C-type strains in lambs show a regressive character and tend to decrease as the infection progresses.
authors.forename: Miguel
authors.initials: M
authors.lastname: Fernández
authors.forename: Julio
authors.initials: J
authors.lastname: Benavides
authors.forename: Iker A
authors.initials: IA
authors.lastname: Sevilla
authors.forename: Miguel
authors.initials: M
authors.lastname: Fuertes
authors.forename: Pablo
authors.initials: P
authors.lastname: Castaño
authors.forename: Laetitia
authors.initials: L
authors.lastname: Delgado
authors.forename: J Francisco
authors.initials: JF
authors.lastname: García Marín
authors.forename: Joseba M
authors.initials: JM
authors.lastname: Garrido
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Ferreras
authors.affiliation: Departamento de Sanidad Animal, Instituto de Ganadería de Montaña (CSIC-ULE), Facultad de Veterinaria, Universidad de León, Campus de Vegazana s/n, León 24071, Spain. vperp@unileon.es.
authors.forename: Valentín
authors.initials: V
authors.lastname: Pérez
mesh_terms: D000818:Animals; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D007111:Immunity, Cellular; D007371:Interferon-gamma / Q000097:blood; D059425:Interferon-gamma Release Tests / Q000662:veterinary; D007422:Intestines / Q000276:immunology; D007428:Intradermal Tests / Q000662:veterinary; D008221:Lymphoid Tissue / Q000276:immunology; D016927:Mycobacterium avium subsp. paratuberculosis / Q000235:genetics / Q000502:physiology*; D010283:Paratuberculosis / Q000276:immunology* / Q000473:pathology* / Q000821:virology; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011897:Random Allocation; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology* / Q000473:pathology* / Q000821:virology
chemical_list: D007371:Interferon-gamma