Polyfunctional CD4 T cells in the response to bovine tuberculosis. (VET2P.1034)

Abstract

Abstract Polyfunctional CD4 T cells simultaneously produce interferon-gamma (IFN-γ), interleukin-2 (IL-2) and tumor necrosis factor-alpha (TNF-α) and play relevant roles in several chronic infections, including human TB and HIV. However, the assessment of this response in bovine infections was not feasible due to the lack of monoclonal antibodies that recognize bovine IL-2. Recently, an antibody specific for bovine IL-2 enabled the evaluation of polyfunctional T cells in cattle. The objective of the present study was to access antigen-specific polyfunctional ex vivo responses after aerosol Mycobacterium bovis infection of cattle. Peripheral blood mononuclear cells (PBMCs) were collected from infected cattle and stimulated with rESAT-6:CFP-10 (E:C), media or pokeweed (PWM) for 16 hours. After stimulation, the expression of CD4, CD45RO, CCR7, IL-2, IFN-γ, TNF-α and cell viability were evaluated. The ex vivo response to E:C consisted of 63% effectors (CD4+ CD45RO- CCR7-), 32% effector memory (CD4+ CD45RO+ CCR7-), and 9% central memory (CD4+ CD45RO+ CCR7+) phenotypes. In regard to the cytokine profile, 70% of cells producing cytokines expressed both IFN-γ and TNF-α, 31% expressed all three cytokines, 6% expressed both TNF-α and IL-2, and 3% expressed IL-2 and IFN-γ. Cells producing only IFN-γ, IL-2, or TNF-α represented, 5%, 8% and 1%, respectively. These findings demonstrate that the polyfunctional response consists mainly of effector cells co-producing IFN-γ and TNF-α.