Frequency Of Autoreactive T Cells 3/5/2014. Circulation Of Activated Cells To The CNS

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1 Immune Basis of New MS Therapies Samia J Khoury, MD Director of Abou-Haidar Neuroscience Institute Director of Multiple Sclerosis Center Professor of Neurology AUBMC MS Center & Harvard Medical School SERUM Circulation Of Activated Cells To The CNS CNS Recruitment of Ag non-specific cells Demyelination Activated Cells CNS Ag-specific cell persists Interaction with endothelium Recirculates Non-CNS specific Cell Frequency Of Autoreactive T Cells T Cells recognizing MBP and PLP are present in normal individuals No difference in the frequency of these cells between MS patients and normal individuals The frequency of activated MBP, and PLP but not tetanus toxoid lines was significantly higher in MS patients 1

2 Activation Of T Cells Binding of TCR to Ag/APC leads to a series of intracellular events that result in transcription of a variety of genes by the T cell Signaling through the TCR is not sufficient for activation to occur. A second signal is required such as binding of CD28 to B7 molecules. How Do Autoreactive T Cells Become Activated Molecular mimicry: antigenic epitopes of an infectious agent mimic a self protein epitope. Superantigens: bind to Class II MHC and specific TCR Vβ segments and may occur during the course of a bacterial or viral infection. Observation in patients with MS: There is clonal expansion and persistence of autoreactive T cells 3) IL-12 APC 2) B7 CD28 THP 1) Engagement of T cell receptor by crossreactive microbial antigen autoreactive autoreactiv autoreactiv e TH1 e autoreactiv auto- TH1 e TH1 TH1 reactive 2

3 Activated Autoreactive T cells expressing VLA-4 adhere to endothelium via interactions with VCAM and enter into the tissue 2) B7 3) IL-12 CD28 1) Engagement of T cell receptor by crossreactive microbial antigen VCAM VLA-4 Inflammed Tissue Peripheral Immune System Activated autoråeactive T cells enter into tissue, recognize self antigen presented by local APC with costimulation and induce inflammation 2) B7 3) IL-12 CD28 auto-reactive TH P 1) Engagement of T cell receptor by crossreactive microbial antigen Peripheral Immune System IL-2 IFN-γ TNF-α autoreactive TH P autoreactive TH1 autoreactive TH1 autoreactive TH1 autoreactive TH 1 CD28 CD154 CD40 IL-12 B7 tissue APC autoantigens Tissue Damage Inflamed tissue becomes source of antigen, epitope spreading occurs 2) B7 3) IL-12 CD28 autoreactive A A autoreactive A TH 1 CD28 B7 tissue APC 1) Engagement of T cell receptor by crossreactive microbial antigen Peripheral Immune System autoreactive B CD28 B7 TH 1 IL-2 CD154 CD40 IFN-γ TNF-α IL-12 Epitope Spreading tissue APC autoantigens 3

4 Th subsets Awasthi, A. et al. Int. Immunol :dxp021v2-21; doi: /intimm/dxp021 Copyright restrictions may apply. A Model of Immune Mechanisms in MS: Overview Immune Status and Disease Course in MS Adaptive Immunity (Antigen-specific T cells, B cells) Relapsing-remitting GD enhancement 4

5 Immune Status and Disease Course in MS Innate Immunity (Microglia, monocytes, dendritic cells) Adaptive Immunity (Antigen-specific T cells, B cells) Disability GD enhancement Relapsing-remitting Secondary progressive Natalizumab (Tysabri) 3 of approximately 3000 treated patients (MS, Crohn s and RA) developed progressive multifocal leukoencephalopathy (PML). 2 of the cases were fatal. Crohn s patient - prior hx of Azathioprine treatment - fatal MS patient - treated with Natalizumab+Avonex - fatal MS patient - treated with Natalizumab+Avonex recovering resulted in the suspension of the drug - Feb FDA re-approved Tysabri in July 2006 Since reintroduction of Tysabri 56,500 patients have been treated and 10 cases of PML have been confirmed Natalizumab (Tysabri) - PML PML is a demyelinating disease of the CNS caused by lytic infection of oligodendrocytes by JC polyomavirus Primary JC viral infection occurs in childhood and is asymptomatic JC virus normally resides in the kidney and lymphoid organs Antibodies to JC virus are detectable in 50-70% of adults B cells may deliver the virus to the CNS PML can occur in immunocompromised patients (AIDS, immunosuppressive medications, transplant patients) No prior association of PML and MS Theories why Natalizumab treatment led to PML Reactivation of the virus in the periphery Organ-specific immunosuppression Generalized immunosuppression Suppression of immune surveillance in CNS by viral-reactive CD8+ cells Increased/dysregulated delivery of virus to the CNS 5

6 PML Risk Stratification Natalizumab treatment is associated with peripheral sequestration of proinflammatory T cells Baseline 12 Months IFN-γ TNF IL-17 Kivisakk et al. Neurology 2009;72: Fingolimod Synthetic analogue of fungal (Isaria sinclairii) metabolite ( Myoricin ) FTY720 Fujita et al. J Antibiot 1994;47:

7 Widespread Expression of S1PR Adaptive immunity depends on regular circulation of lymphocytes between blood and lymphoid tissue in the search for antigens. When an activating antigen is encountered in the lymph nodes, expression of S1P1 on T cells is transiently downregulated, allowing the T cells to remain in contact with antigen-presenting cells and to become activated. Retention in lymphoid tissues and recirculation of lymphocytes back to the blood circulation is regulated in part by a concentration gradient of S1P between lymphoid tissues and other tissues or body fluids, which is sensed through S1P1R expressed on lymphocytes Following activation, cell-surface expression of S1P1 is upregulated, allowing cells to respond to the S1P gradient and exit the lymph node S1P signaling regulates the egress of lymphocytes from LN 7

8 Fingolimod selectively retains only lymphocytes that regularly traffic through lymphoid tissues Fingolimod Mechanisms 8

9 Alemtuzumab Monoclonal Antibody for CD52 expressed on essentially all B and T cells, monocytes, macrophages, NK cells and some granulocytes Approved for B-CLL, Phase II for MS Benefits: 75% reduction in relapse rate compared to REBIF (IFN-β 1a) 60% reduction in risk of progression of disability Risks: Dosing halted due to 3 cases of confirmed ITP A separate study suggest high risk (30%) of Graves Disease Hematologic Toxicity: Pancytopenia Risk of Opportunistic Infections Phase 3 ongoing Alemtuzumab 9

10 Mechanisms of autoimmune disease emergence after Alemtuzumab Monocytes return to normal within 3 months B cell counts return to baseline numbers by 3 months and are then increased to about 124% of pre-treatment levels T cell counts recover much slower: depletion of CD4+ cells lasts a median of 61 months and of CD8+ cells for 30 months The observed enhanced antibody-mediated autoimmunity might be related to enhanced B cell function in the state of lymphopenia. Patients who developed autoimmunity were noted to have enhanced production of IL-21, that may promote autoimmunity by various mechanisms, such as TH17 induction, and promotion of B cell differentiation and antibody production Daclizumab Hypothesized Immunomodulatory Effect of Daclizumab Treatment 10

11 Additional mechanisms of Daclizumab anti-cd25 interferes with early dendritic cell-t cell interaction anti-cd25 treatment interferes with CD40L expression CD25high T regulatory (Treg) cells are slightly diminished in frequency and possibly also in their function Daclizumab high-yield process in RRMS (SELECT) Daclizumab high-yield process in RRMS (SELECT) 11

12 Dimethylfumarate-BG12 Immune Mechanisms of Dimethylfumarate Nrf-2 (nuclear factor E2(erythroid-derived 2)-related factor) which is released from binding to Keap-1 via the activity of fumarates. Nrf-2 in turn upregulates an array of antioxidative pathways such as increased glutathione levels. These also lead to an inhibition of the translocation of NF-κB into the nucleus Decreased expression of NF-κB-dependent genes that regulate the expression of a cascade of inflammatory cytokines, chemokines, and adhesion molecules. DMF can induce apoptosis in human T-cells may shift the cytokine profile from a TH1 to a TH2 profile. Effect of Dimethylfumarate on various cells Cell type Effect T cells B cells Dendritic Cells Glia Endothelial cells Apoptosis TH1 to TH2 shift Apoptosis Inhibition of differentiation Downregulation of TH1 response Inhibition of proinflammatory cytokines Inhibition of TNF-a, ICAM-1, E-selectin, VCAM-1 12

13 A. The initial MRI B & C. On follow-up 2 and 3 months later D. On follow-up at 3 months, enhancing lesions suggestive of the immune reconstitution inflammatory syndrome (IRIS). Terflunomide: Mechanism of Action TEMSO Trial N Engl J Med 2011;365:

14 TEMSO Trial N Engl J Med 2011;365: N Engl J Med 2011;365: Laquinimod Laquinimod is an orally administered compound that is structurally related to linomide Laquinimod appears to have some ability to penetrate the CNS, with 7% 8% penetrance reported in healthy SJL/N mice and 13% in EAE as measured by 14C labeled laquinimod The therapeutic mode of action of laquinimod in MS is not fully understood 14

15 B cell functions B cell directed therapies Therapeutic recombinant antibodies Nomenclature 15

16 PML Risk in Autoimmune Disease Therapy Estimated incidence 1 case per individuals with RA treated with Rituximab Worldwide, there were seventeen cases of PML that are potentially associated with MMF in lupus patients. Pre-B cells that harbor JCV in a latent state may be released into circulation to repopulate B-cell functions after differentiation 3 patients had JCV detected in paraffin-fixed bone marrow samples obtained years before rituximab administration. JCV latency may be more relevant for natalizumab-treated patients because CD34+ cells have been shown to mobilize into the peripheral circulation upon initiation of treatment Alemtuzumab The CAMMS223 Trial Investigators. N Engl J Med 2008;359:

17 The CAMMS223 Trial Investigators. N Engl J Med 2008;359: Laquinimod: Mechanisms of Action CTLA4Ig Inhibition of the Immune Response CD28 on the surface of T cells interacts with CD80 and CD86 on the surface of antigen presenting cells to provide a costimulatory signal 17

18 Mechanism of CTLA4Ig Inhibition of The Immune Response CTLA4Ig treatment in patients with MS An open-label, phase 1 clinical trial Th2/Th1 MBP (20µg/ml) BL 8D M1 M2 M3 CTLA-4Ig infusion Viglietta et al. Neurology 2008;71: ITN035AI Khoury - ACCLAIM - Phase II Trial A Phase II, Randomized, Double-Blind, Parallel Group, Placebo-Controlled, Multicenter Study to Evaluate the Safety and Efficacy of Abatacept (CTLA4-Ig) in Adults with Multiple Sclerosis The study is sponsored by the National Institute of Allergy and Infectious Diseases (a part of the National Institutes of Health) and the non-profit Immune Tolerance Network 18

19 Therapeutic Approaches for the Treatment of MS Decrease Th1/Th17 Induce Tregs Prevent lymphocyte trafficking Deplete B cells Affect innate immunity Provide neuroprotection Promote remyelination 19