Novel small molecule IL-6 inhibitor suppresses autoreactive Th17 development and promotes Treg development.

Multiple sclerosis (MS) is the leading cause of non-traumatic neurological disability in the United States in young adults, but current treatments are only partially effective, making it necessary to develop new, innovative therapeutic strategies. Myelin-specific interleukin (IL)-17-producing T helper type 17 (Th17) cells are a major subset of CD4 T effector cells (Teff ) that play a critical role in mediating the development and progression of MS and its mouse model, experimental autoimmune encephalomyelitis (EAE), while regulatory T cells (Treg ) CD4 T cells are beneficial for suppressing disease. The IL-6/signal transducer and activator of transcription 3 (STAT-3) signaling pathway is a key regulator of Th17 and Treg cells by promoting Th17 development and suppressing Treg development. Here we show that three novel small molecule IL-6 inhibitors, madindoline-5 (MDL-5), MDL-16 and MDL-101, significantly suppress IL-17 production in myelin-specific CD4 T cells in a dose-dependent manner in vitro. MDL-101 showed superior potency in suppressing IL-17 production compared to MDL-5 and MDL-16. Treatment of myelin-specific CD4 T cells with MDL-101 in vitro reduced their encephalitogenic potential following their subsequent adoptive transfer. Furthermore, MDL-101 significantly suppressed proliferation and IL-17 production of anti-CD3-activated effector/memory CD45RO+ CD4+ human CD4 T cells and promoted human Treg development. Together, these data demonstrate that these novel small molecule IL-6 inhibitors have the potential to shift the Teff  : Treg balance, which may provide a novel therapeutic strategy for ameliorating disease progression in MS.

Impact of suppressing retinoic acid-related orphan receptor gamma t (ROR)γt in ameliorating central nervous system autoimmunity.

Multiple sclerosis (MS) is an immune-mediated chronic central nervous system (CNS) disease affecting more than 400 000 people in the United States. Myelin-reactive CD4 T cells play critical roles in the formation of acute inflammatory lesions and disease progression in MS and experimental autoimmune encephalomyelitis (EAE), a well-defined mouse model for MS. Current MS therapies are only partially effective, making it necessary to develop more effective therapies that specifically target pathogenic myelin-specific CD4 T cells for MS treatment. While suppressing T-bet, the key transcription factor in T helper type 1 (Th1) cells, has been demonstrated to be beneficial in prevention and treatment of EAE, the therapeutic potential of retinoic acid-related orphan receptor gamma t (ROR)γt, the key transcription factor for Th17 cells, has not been well-characterized. In this study, we characterized the correlation between RORγt expression and other factors affecting T cell encephalitogenicity and evaluated the therapeutic potential of targeting RORγt by siRNA inhibition of RORγt. Our data showed that RORγt expression correlates with interleukin (IL)-17 production, but not with the encephalitogenicity of myelin-specific CD4 T cells. IL-23, a cytokine that enhances encephalitogenicity, does not enhance RORγt expression significantly. Additionally, granulocyte-macrophage colony-stimulating factor (GM-CSF) levels, which correlate with the encephalitogenicity of different myelin-specific CD4 T cell populations, do not correlate with RORγt. More importantly, inhibiting RORγt expression in myelin-specific CD4 T cells with an siRNA does not reduce disease severity significantly in adoptively transferred EAE. Thus, RORγt is unlikely to be a more effective therapeutic target for ameliorating pathogenicity of encephalitogenic CD4 T cells.

Autonomic regulation of neuroimmunological responses: implications for multiple sclerosis.

The expression of neural regulatory molecules by immune cells that infiltrate the nervous system upon injury may be a mechanism for cross regulation between the nervous system and the immune system. Several lines of evidence implicate nerve growth factor signaling through its receptors as a potential source of communication between the two systems. The expression of beta-adrenergic receptors and sympathetic innervation of lymphoid organs represents another example of communication between the immune and the nervous system. In this review, we discuss mechanisms of how factors in common between the nervous system and the immune system may result in regulatory circuits which are important in both healthy and diseased states. These studies may have relevance for a number of inflammatory conditions in humans, including multiple sclerosis.

Role of nerve growth factor in experimental autoimmune encephalomyelitis.

The expression of neural regulatory molecules by immune cells that infiltrate the nervous system upon injury may be a mechanism for cross-regulation between the nervous system and the immune system. Several lines of evidence implicate nerve growth factor (NGF) signaling through its receptors (TrkA and p75(NGFR)) as a potential source of communication between the two systems. We observed changes in NGF mRNA expression and protein secretion by T lymphocytes polarized toward the Th2 phenotype. The presence of NGF did not affect T cell proliferation or cytokine production in vitro. Mice treated with NGF by i. p. injection following induction of experimental autoimmune encephalomyelitis, an inflammatory, demyelinating disease of the central nervous system, showed a delayed onset of disease and lower clinical scores during the course of disease. These data suggest a role for NGF signaling in the regulation of the immune response, possibly by enhancing sympathetic innervation of lymphoid tissues.

Developmentally regulated gene expression of Th2 cytokines in the brain.

Given the critical role of cytokines in the regulation of an inflammatory response, we investigated whether certain cytokines are expressed in the brains of normal mice during maturation that could contribute to the immune-privileged nature of the CNS or potentially influence an immune-mediated illness such as experimental allergic encephalomyelitis. The gene expression of IFN gamma (Th1 cytokine) and IL-4 (Th2 cytokine) was analyzed in the brain of several strains of mice. IFN gamma was not detectable. However, IL-4 was present in the brains of neonatal mice, but not adult mice. Resident CNS cells are believed to be the source of the IL-4, because mice deficient in T cells (SCID and RAG2-/-) expressed the IL-4 gene in the CNS. Further analysis indicated that the gene expression of the Th2 cytokine transcription factor, GATA-3, correlated with IL-4 and IL-10 expression in the brain. Since GATA-3-deficient mice have an abnormal CNS, brain-derived Th2 cytokines may play an important role in CNS development, as well as potentially contribute to the immune-privileged nature of the brain.

The role of CTLA-4 in tolerance induction and T cell differentiation in experimental autoimmune encephalomyelitis: i.p. antigen administration.

Recent evidence suggests that co-stimulation provided by B7 molecules through CTLA-4 is important in establishing peripheral tolerance. In the present study, we examined the kinetics of tolerance induction and T cell differentiation following i.p. administration of myelin basic protein (MBP) Ac1-11 in mice transgenic for a TCR V(beta)8.2 gene derived from an encephalitogenic T cell clone specific for MBP Ac1-11. Examination of the lymph node cell response after antigen administration demonstrated a dependence on CTLA-4 for i.p. tolerance induction. Examination of splenocyte responses suggested that i.p. antigen administration induced a T(h)2 response, which was potentiated by anti-CTLA-4 administration. Interestingly, i.p. tolerance was able to inhibit the induction of experimental autoimmune encephalomyelitis and anti-CTLA-4 administration did not alter this phenotype, suggesting that CTLA-4 blockade did not block tolerance induction. Thus, T cell differentiation and the dependence on CTLA-4 for tolerance induction following i.p. antigen administration differs between lymph node and spleen in a model of organ-specific autoimmunity.

The role of CTLA-4 in tolerance induction and ttigen administration cell differentiation in experimental autoimmune encephalomyelitis: i. v. antigen administration.

Interactions between B7 molecules on antigen-presenting cells and CTLA-4 on T cells have been shown to be important in establishing tolerance. In the present study, we examined the kinetics of tolerance induction following i.v. administration of myelin basic protein (MBP) Ac1-11 in mice transgenic for a TCR V(beta)8.2 gene derived from an encephalitogenic T cell clone specific for MBP Ac1-11. Examination of the lymph node cell (LNC) response 10 days after antigen administration demonstrated an accentuation of i.v. tolerance induction with anti-CTLA-4 blockade. Anergy was induced in splenocytes by i.v. antigen administration as shown by a decrease in MBP-specific proliferation and IL-2 production, and anti-CTLA-4 potentiated this effect. In addition, i.v. antigen plus anti-CTLA-4 and complete Freund's adjuvant was not encephalitogenic. Interestingly, i.v. tolerance (a single injection) did not inhibit experimental autoimmune encephalomyelitis (EAE) and anti-CTLA-4 administration did not alter this phenotype. These results suggest that while the majority of MBP-specific T cells are tolerized by i.v. antigen and that this process is potentiated by anti-CTLA-4 administration, a population of T cells remains that is quite efficient in mediating EAE.

Regulation of experimental autoimmune encephalomyelitis with insulin-like growth factor (IGF-1) and IGF-1/IGF-binding protein-3 complex (IGF-1/IGFBP3).

Insulin-like growth factor (IGF)-1 is a cytokine that promotes oligodendrocyte development and myelin production. This study investigated whether treatment of chronic, relapsing murine experimental autoimmune encephalomyelitis (EAE) with IGF-1 or IGF-1 associated with its binding protein, IGFBP3, altered the course of disease. Administration of IGF-1/IGFBP3 (1-100 mg/kg per day) delayed the onset of disease in a dose-dependent manner and histologic examination showed a delay in inflammatory cells entering the central nervous system. However, once signs of EAE developed, disease was enhanced in the mice that had been given the highest dose of IGF-1/IGFBP3. Treatment with IGF-1/IGFBP3 after the onset of signs resulted in a severe relapse. Administration of free IGF-1 (10 mg/kg per day) provided mild protection when given before disease onset, but did not significantly alter the course of disease if given after disease onset. Possible mechanisms that could explain the altered disease in IGF-1/IGFBP3-treated mice included (a) IGF-1/IGFBP3 administration delayed the onset of EAE by downregulating ICAM-1 gene expression in the central nervous system, and (b) IGF-1/IGFBP3 treatment of EAE resulted in more severe disease due to enhanced expansion of encephalitogenic T cells. Although IGF-1 may enhance remyelination, these results indicate that administration of IGF-1 associated with IGFBP3 may also accentuate autoimmune demyelinating disease.

Decreased dependence of myelin basic protein-reactive T cells on CD28-mediated costimulation in multiple sclerosis patients. A marker of activated/memory T cells.

Although multiple sclerosis (MS) patients and healthy individuals have similar frequencies of myelin basic protein (MBP)-specific T cells, the activation state of these cells has not been well characterized. Therefore, we investigated the dependence of MBP-reactive T cells on CD28-mediated costimulation in MS patients, healthy controls, and stroke patients. MBP-reactive T cells from healthy controls and stroke patients failed to proliferate efficiently when costimulation was blocked using anti-CD28, consistent with a naive T cell response. In contrast, MBP-specific T cell proliferation was not inhibited, or was only partially inhibited when CD28-mediated costimulation was blocked in MS patients. Blockade of CD28 failed to inhibit tetanus toxoid-specific T cell proliferation in both the controls and MS patients, demonstrating that memory cells are not dependent on CD28-mediated costimulation. Limiting dilution analysis indicated that the frequency of MBP-reactive T cells was significantly decreased in healthy controls compared with MS patients when CD28-mediated costimulation was blocked. These data suggest that MBP-reactive T cells are more likely to have been activated in vivo and/or differentiated into memory T cells in MS patients compared with controls, indicating that these cells may be participating in the pathogenesis of MS.

Longitudinal study of myelin basic protein-specific T-cell receptors during the course of multiple sclerosis.

This study analyzed the stability of the myelin basic protein (MBP)-specific T-cell receptor (TCR) repertoire during the course of multiple sclerosis (MS) in three patients who were monitored for three years by gadolinium-enhanced magnetic resonance imaging. Bulk-culture T-cell lines (TCLs) were generated from 3-4 time points for each patient, including times of active and quiescent disease. TCR analysis of these TCLs indicated that both the V alpha and V beta usage was similar over time for each patient. Sequencing of TCRs demonstrated conserved complementarity-determining region 3 (CDR3) sequences within TCLs that expressed the same V alpha segment over time, although the J alpha usage was different for each TCR. This indicates that the population of MBP-reactive T-cells is changing during the course of MS, but that host and/or environmental factors may be selecting T-cells with particular MHC/peptide binding domains.