ABSTRACT
4-1BB (CD137, TNFRSF9) is a costimulatory receptor expressed on several subsets of activated immune cells. Numerous studies of mouse and human T cells indicate that 4-1BB promotes cellular proliferation, survival, and cytokine production. 4-1BB agonist mAbs have demonstrated efficacy in prophylactic and therapeutic settings in both monotherapy and combination therapy tumor models and have established durable anti-tumor protective T-cell memory responses. PF-05082566 is a fully human IgG2 that binds to the extracellular domain of human 4-1BB with high affinity and specificity. In preclinical studies, this agonist antibody demonstrated its ability to activate NF-κB and induce downstream cytokine production, promote leukocyte proliferation, and inhibit tumor growth in a human PBMC xenograft tumor model. The mechanism of action and robust anti-tumor efficacy of PF-05082566 support its clinical development for the treatment of a broad spectrum of human malignancies.
Subject(s)
4-1BB Ligand/agonists , Antibodies, Monoclonal/therapeutic use , Immunoglobulin G/therapeutic use , T-Lymphocytes/immunology , 4-1BB Ligand/immunology , Animals , Antibodies, Monoclonal/immunology , Antibodies, Monoclonal, Humanized , Cell Line, Tumor , Cell Proliferation/drug effects , Female , Humans , Immunoglobulin G/immunology , Immunoglobulin G/pharmacology , Leukocytes, Mononuclear/drug effects , Leukocytes, Mononuclear/immunology , Lymphocyte Activation/drug effects , Lymphocyte Activation/immunology , Macaca fascicularis , Male , Mice , NF-kappa B/immunology , T-Lymphocytes/drug effects , Xenograft Model Antitumor AssaysABSTRACT
CD8+ cytotoxic T lymphocytes contribute to viral and autoimmune myocarditis and cardiac allograft rejection. The role of cytotoxic T-lymphocyte-associated antigen (CTLA)-4 as a negative regulator of CD4+ T cells is well defined, yet CTLA-4 regulation of CD8+ T cells is less clear. We studied CTLA-4 regulation of cytotoxic T lymphocytes in a transgenic model of CD8+ T-cell-mediated myocarditis. We generated CTLA-4(-/-) Rag 2(-/-) OT-1 mice, the CD8+ T cells of which express an ovalbumin (OVA) peptide-specific, class I major histocompatibility complex-restricted T-cell receptor. CTLA-4(-/-Tc12) OT-1 effectors, differentiated with interleukin-12 present, are hyperproliferative in vitro, compared with CTLA-4(+/+)Tc12 OT-1 controls. Transfer of low doses of CTLA-4(-/-Tc12) OT-1 cells to cMy-mOVA mice, which express OVA on cardiac myocytes, causes severe myocarditis, with 99% mortality, compared with no mortality after transfer of low doses of CTLA-4(+/+)Tc12 OT-1 cells. High doses of CTLA-4(+/+)Tc12 cells cause lethal myocarditis in cMy-mOVA mice, but high doses of CTLA-4(+/+)Tc0 CTL, generated without interleukin-12, are hypoproliferative within the cardiac-draining lymph node and do not significantly infiltrate the heart. In contrast, CTLA-4(-/-Tc0) cytotoxic T lymphocytes do proliferate in the cardiac-draining lymph node and diffusely infiltrate the heart. Nonetheless, high doses of CTLA-4(-/-Tc0) cells cause only limited tissue damage, and the disease is not lethal. These data show that CTLA-4 regulates myocarditic CD8+ T cell responses and that CTLA-4 deficiency partly overcomes a differentiation block that exists when naïve CD8+ T cells are stimulated without interleukin-12. Therefore, targeting CTLA-4 solely or in conjunction with interleukin-12 could influence effector CD8+ T cell responses in therapeutically beneficial ways.
Subject(s)
Antigens, CD/physiology , Antigens, Differentiation/physiology , Interleukin-12/physiology , Myocarditis/physiopathology , T-Lymphocytes, Cytotoxic/immunology , Adoptive Transfer , Animals , Antigens, CD/genetics , Antigens, Differentiation/genetics , CTLA-4 Antigen , Cell Differentiation , Cells, Cultured/drug effects , Cells, Cultured/immunology , Crosses, Genetic , Cytotoxicity, Immunologic , DNA-Binding Proteins/deficiency , DNA-Binding Proteins/genetics , Egg Proteins/immunology , Egg Proteins/pharmacology , Egg Proteins/toxicity , Interferon-gamma/metabolism , Lymph Nodes/pathology , Lymphocyte Activation , Lymphokines/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Models, Immunological , Myocarditis/immunology , Myocarditis/prevention & control , Ovalbumin/immunology , Ovalbumin/pharmacology , Ovalbumin/toxicity , Peptide Fragments , Specific Pathogen-Free Organisms , T-Lymphocytes, Cytotoxic/metabolismABSTRACT
Cardiac antigen-specific CD8(+) T cells are involved in the autoimmune component of human myocarditis. Here, we studied the differentiation and migration of pathogenic CD8(+) T cell effector cells in a new mouse model of autoimmune myocarditis. A transgenic mouse line was derived that expresses cardiac myocyte restricted membrane-bound ovalbumin (CMy-mOva). The endogenous adaptive immune system of CMy-mOva mice displays tolerance to ovalbumin. Adoptive transfer of naive CD8(+) T cells from the ovalbumin-specific T cell receptor-transgenic (TCR-transgenic) OT-I strain induces myocarditis in CMy-mOva mice only after subsequent inoculation with ovalbumin-expressing vesicular stomatitis virus (VSV-Ova). OT-I effector T cells derived in vitro in the presence or absence of IL-12 were adoptively transferred into CMy-mOva mice, and the consequences were compared. Although IL-12 was not required for the generation of cytolytic and IFN-gamma-producing effector T cells, only effectors primed in the presence of IL-12 infiltrated CMy-mOva hearts in significant numbers, causing lethal myocarditis. Furthermore, analysis of OT-I effectors collected from a mediastinal draining lymph node indicated that only effectors primed in vitro in the presence of IL-12 proliferated in vivo. These data demonstrate the importance of IL-12 in the differentiation of pathogenic CD8(+) T cells that can cause myocarditis.
