title: Mycobacterium bovis Δmce2 double deletion mutant protects cattle against challenge with virulent M. bovis.
abstract: A Mycobacterium bovis strain deleted in mce2A and mce2B genes (M. bovis Δmce2) was tested as an experimental vaccine in cattle challenged with a virulent M. bovis strain. Three-and-a-half-month old calves (n = 5 to 6 per group) were vaccinated and challenged with a virulent strain of M. bovis by the intratracheal route 9 weeks after vaccination. A non-vaccinated group and a group vaccinated with BCG were included as controls. Blood samples were collected to measure IFN-γ by an interferon-gamma release assay (IGRA), cytometry and cytokine responses of bovine purified protein derivative (PPD) restimulated peripheral blood mononuclear cells (PBMCs). The IGRA test showed IFN-γ values similar to pre-vaccination except for the animals vaccinated with M. bovis Δmce2, where a significant increase was observed at 30 days post-vaccination. The expression of IL-2R on CD4(+) cells in response to PPD from the animals vaccinated with Δmce2 increased at 15 days post-vaccination compared to cells from non-vaccinated group. Vaccination of cattle with M. bovis Δmce2 induced the highest (P < 0.05) expression of IFN-γ and IL-17 mRNA upon PPD stimulation of PBMCs compared to vaccination with BCG or that for the non-vaccinated group. There was a weak positive correlation between the production of these proinflammatory cytokines post-vaccination and reduced pathology scores post-challenge. The animals were euthanized and necropsied 100 days after challenge. The group vaccinated with M. bovis Δmce2 displayed a significantly lower histopathological score for lesions in lungs and pulmonary lymph nodes than for the other groups (P < 0.05). A marked positive reaction to tuberculin intradermal test was observed post-vaccination in animals vaccinated with M. bovis Δmce2 compared to those vaccinated with BCG or the non-vaccinated group. In contrast, after challenge, non-vaccinated animals had greater skin test responses than the vaccinated animals. In summary, M. bovis Δmce2 is a promising vaccine candidate to control M. bovis pathogenesis in cattle.
authors.affiliation: Instituto de Biotecnología, INTA, N. Repetto y De los Reseros, 1686 Hurlingham, Buenos Aires, Argentina.
authors.forename: Federico Carlos
authors.initials: FC
authors.lastname: Blanco
authors.forename: María Verónica
authors.initials: MV
authors.lastname: Bianco
authors.forename: Sergio
authors.initials: S
authors.lastname: Garbaccio
authors.forename: Virginia
authors.initials: V
authors.lastname: Meikle
authors.forename: María José
authors.initials: MJ
authors.lastname: Gravisaco
authors.forename: Valeria
authors.initials: V
authors.lastname: Montenegro
authors.forename: Edgar
authors.initials: E
authors.lastname: Alfonseca
authors.forename: Mahavir
authors.initials: M
authors.lastname: Singh
authors.forename: Soledad
authors.initials: S
authors.lastname: Barandiaran
authors.forename: Ana
authors.initials: A
authors.lastname: Canal
authors.forename: Lucas
authors.initials: L
authors.lastname: Vagnoni
authors.forename: Bryce Malcom
authors.initials: BM
authors.lastname: Buddle
authors.forename: Fabiana
authors.initials: F
authors.lastname: Bigi
authors.forename: Angel
authors.initials: A
authors.lastname: Cataldi
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics* / Q000276:immunology; D001500:BCG Vaccine; D058491:Bacterial Load; D001426:Bacterial Proteins / Q000235:genetics* / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002417:Cattle; D016207:Cytokines / Q000096:biosynthesis / Q000097:blood / Q000235:genetics; D017353:Gene Deletion; D007371:Interferon-gamma / Q000096:biosynthesis; D059425:Interferon-gamma Release Tests / Q000379:methods; D008213:Lymphocyte Activation / Q000276:immunology; D016131:Lymphocyte Subsets / Q000276:immunology; D009163:Mycobacterium bovis / Q000235:genetics* / Q000472:pathogenicity; D014373:Tuberculin / Q000276:immunology; D014374:Tuberculin Test; D032581:Tuberculosis Vaccines / Q000276:immunology*; D014380:Tuberculosis, Bovine / Q000276:immunology / Q000382:microbiology / Q000473:pathology / Q000517:prevention & control*; D014613:Vaccines, Attenuated / Q000276:immunology; D014774:Virulence
chemical_list: D000942:Antigens, Bacterial; D001500:BCG Vaccine; D001426:Bacterial Proteins; D016207:Cytokines; D014373:Tuberculin; D032581:Tuberculosis Vaccines; D014613:Vaccines, Attenuated; C443482:mce2 protein, Mycobacterium tuberculosis; D007371:Interferon-gamma