Role of costimulatory pathways in the pathogenesis of multiple sclerosis and experimental autoimmune encephalomyelitis

Immune Checkpoint Inhibitor-Associated Cutaneous Adverse Events: Mechanisms of Occurrence

Immunotherapy, particularly that based on blocking checkpoint proteins in many tumors, including melanoma, Merkel cell carcinoma, non-small cell lung cancer (NSCLC), triple-negative breast (TNB cancer), renal cancer, and gastrointestinal and endometrial neoplasms, is a therapeutic alternative to chemotherapy. Immune checkpoint inhibitor (ICI)-based therapies have the potential to target different pathways leading to the destruction of cancer cells. Although ICIs are an effective treatment strategy for patients with highly immune-infiltrated cancers, the development of different adverse effects including cutaneous adverse effects during and after the treatment with ICIs is common. ICI-associated cutaneous adverse effects include mostly inflammatory and bullous dermatoses, as well as severe cutaneous side reactions such as rash or inflammatory dermatitis encompassing erythema multiforme; lichenoid, eczematous, psoriasiform, and morbilliform lesions; and palmoplantar erythrodysesthesia. The development of immunotherapy-related adverse effects is a consequence of ICIs' unique molecular action that is mainly mediated by the activation of cytotoxic CD4+/CD8+ T cells. ICI-associated cutaneous disorders are the most prevalent effects induced in response to anti-programmed cell death 1 (PD-1), anti-cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), and anti-programmed cell death ligand 1 (PD-L1) agents. Herein, we will elucidate the mechanisms regulating the occurrence of cutaneous adverse effects following treatment with ICIs.

Treated and Untreated Primary Progressive Multiple Sclerosis: Walkthrough Immunological Changes of Monocytes and T Regulatory Cells

The objective of this study was to investigate regulatory T cells (Tregs) and monocytes; specifically, the expression of CTLA-4 (CD152) and FOXP3+ in CD4+CD25+ Tregs and the expression of CD40+ and CD192+ monocyte subpopulations in subjects with primary progressive multiple sclerosis (PPMS). Immunological analysis was conducted on peripheral blood samples collected from the 28 PPMS subjects (15 treated with ocrelizumab and 13 untreated PPMS subjects) and 10 healthy control subjects (HCs). The blood samples were incubated with antihuman CD14, CD16, CD40, and CD192 antibodies for monocytes and antihuman CD4, CD25, FOXP3, and CTLA-4 antibodies for lymphocytes. The study results showed that in comparison to HCs both ocrelizumab treated (N = 15) and untreated (N = 13) PPMS subjects had significantly increased percentages of CTLA-4+ and FOXP3+ in CD4+CD25+ Tregs. Further, ocrelizumab treated PPMS subjects, compared to the untreated ones, had significantly decreased percentages of CD192+ and CD40+ nonclassical monocytes. Increased percentages of CTLA-4+ and FOXP3+ in CD4+CD25+ Tregs in both ocrelizumab treated and untreated PPMS subjects indicates the suppressive (inhibitory) role of Tregs in abnormal immune responses in PPMS subjects. Decreased percentages of CD40+ and CD192+ non-classical CD14+CD16++ monocytes for treated compared to untreated PPMS subjects suggests a possible role for ocrelizumab in dampening CNS inflammation.

Expression of CD40 and CD192 in Classical Monocytes in Multiple Sclerosis Patients Assessed with Transcranial Magnetic Stimulation

Expression of CD40 and CD192 markers in different monocyte subpopulations has been reported to be altered in people with MS (pwMS). Also, functional connectivity of the corticospinal motor system pathway alterations has been proved by transcranial magnetic stimulation (TMS). The study objective was to investigate the expression of CD40 and CD192 in classical (CD14++CD16-), intermediate CD14++CD16+ and non-classical (CD14+CD16++) blood monocyte subpopulations in pwMS, undergoing neurophysiological TMS assessment of the corticospinal tract integrity by recording motor-evoked potentials (MEPs). Radiological examination on lesion detection with MRI was performed for 23 patients with relapsing-remitting MS treated with teriflunomide. Then, immunological analysis was conducted on peripheral blood samples collected from the patients and 10 healthy controls (HC). The blood samples were incubated with anti-human CD14, CD16, CD40 and CD192 antibodies. Next, pwMS underwent neurological testing of functional disability (EDSS) and TMS assessment with recording MEPs from upper and lower extremity muscles. The results show that in comparison to HC subjects, both pwMS with normal and altered MEP findings (prolonged MEP latency or absent MEP response) had significantly decreased surface receptor expression measured (MFIs) of CD192 and increased CD40 MFI in classical monocytes, and significantly increased percentages of classical and total monocytes positive for CD40. Knowing CD40's pro-inflammatory action, and CD192 as a molecule that enables the passing of monocytes into the brain, decreased CD192 in classical monocytes could represent a beneficial anti-inflammatory parameter.

Proteomic analyses of smear-positive/negative tuberculosis patients uncover differential antigen-presenting cell activation and lipid metabolism

Background

Tuberculosis (TB) remains a major global health concern, ranking as the second most lethal infectious disease following COVID-19. Smear-Negative Pulmonary Tuberculosis (SNPT) and Smear-Positive Pulmonary Tuberculosis (SPPT) are two common types of pulmonary tuberculosis characterized by distinct bacterial loads. To date, the precise molecular mechanisms underlying the differences between SNPT and SPPT patients remain unclear. In this study, we aimed to utilize proteomics analysis for identifying specific protein signatures in the plasma of SPPT and SNPT patients and further elucidate the molecular mechanisms contributing to different disease pathogenesis.

Methods

Plasma samples from 27 SPPT, 37 SNPT patients and 36 controls were collected and subjected to TMT-labeled quantitative proteomic analyses and targeted GC-MS-based lipidomic analysis. Ingenuity Pathway Analysis (IPA) was then performed to uncover enriched pathways and functionals of differentially expressed proteins.

Results

Proteomic analysis uncovered differential protein expression profiles among the SPPT, SNPT, and Ctrl groups, demonstrating dysfunctional immune response and metabolism in both SPPT and SNPT patients. Both groups exhibited activated innate immune responses and inhibited fatty acid metabolism, but SPPT patients displayed stronger innate immune activation and lipid metabolic inhibition compared to SNPT patients. Notably, our analysis uncovered activated antigen-presenting cells (APCs) in SNPT patients but inhibited APCs in SPPT patients, suggesting their critical role in determining different bacterial loads/phenotypes in SNPT and SPPT. Furthermore, some specific proteins were detected to be involved in the APC activation/acquired immune response, providing some promising therapeutic targets for TB.

Conclusion

Our study provides valuable insights into the differential molecular mechanisms underlying SNPT and SPPT, reveals the critical role of antigen-presenting cell activation in SNPT for effectively clearing the majority of Mtb in bodies, and shows the possibility of APC activation as a novel TB treatment strategy.

Immune Regulatory Functions of Macrophages and Microglia in Central Nervous System Diseases

Macrophages can be characterized as a very multifunctional cell type with a spectrum of phenotypes and functions being observed spatially and temporally in various disease states. Ample studies have now demonstrated a possible causal link between macrophage activation and the development of autoimmune disorders. How these cells may be contributing to the adaptive immune response and potentially perpetuating the progression of neurodegenerative diseases and neural injuries is not fully understood. Within this review, we hope to illustrate the role that macrophages and microglia play as initiators of adaptive immune response in various CNS diseases by offering evidence of: (1) the types of immune responses and the processes of antigen presentation in each disease, (2) receptors involved in macrophage/microglial phagocytosis of disease-related cell debris or molecules, and, finally, (3) the implications of macrophages/microglia on the pathogenesis of the diseases.

Comparison of OX40 expression in patients with multiple sclerosis and neuromyelitis optica as an approach to diagnosis

BACKGROUND

Previous studies have shown that CD134 (OX40) co-stimulation is involved in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) models and the antigen is expressed within multiple sclerosis lesions in humans. OX40 (CD134) is thought to be a secondary co-stimulatory immune checkpoint molecule that is expressed by T cells. This study aimed to evaluate the mRNA expression of OX40 and its serum levels in the peripheral blood of patients with Multiple Sclerosis (MS) or Neuromyelitis Optica (NMO).

METHODS

Patients with MS (n = 60), NMO (n = 20), and 20 healthy subjects were recruited from Sina Hospital, Tehran, Iran. The diagnoses were confirmed by a specialist in clinical neurology. Peripheral venous blood was obtained from all subjects, and mRNA quantification of OX40 was conducted using real-time PCR. Serum samples were also obtained and the concentration of OX40 was determined using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

There was a significant correlation between the mRNA expression and serum levels of OX40 and disability as assessed using the expanded disability status scale (EDSS) in the patients with MS, but not in the patients with NMO. Expression of OX40 mRNA was significantly higher in the peripheral blood of MS patients compared to healthy individuals and NMO patients (*P < 0.05). In addition, serum OX40 concentrations were also significantly higher in patients with MS patients compared with healthy subjects (9.08 ± 2.48 vs. 1.49 ± 0.54 ng/ml; P = 0.041).

CONCLUSIONS

It appears that an increased expression of OX40 may be associated with the hyperactivation of T cells in patients with MS, and this may play a role in the pathogenesis of the disease.

Ocrevus reduces TH40 cells, a biomarker of systemic inflammation, in relapsing multiple sclerosis (RMS) and in progressive multiple sclerosis (PMS)

Treating MS has been difficult. One successful drug is Ocrelizumab (anti-CD20), used for the chronic relapsing MS (RMS) and the progressive MS (PMS) forms. TH40 cells are pathogenic effector T cells that increase in percentage and numbers during chronic inflammation. Here we show that in the earliest MS course, clinically isolated syndrome (CIS), TH40 cells expand in number. In PMS TH40 cell numbers remain expanded demonstrating sustained chronic inflammation. In RMS TH40 cells were found in CSF and express CD20. Ocrelizumab reduced TH40 cells to healthy control levels in patients. During treatment inflammatory cytokine producing TH40 cells were decreased.

Molecular and spatial heterogeneity of microglia in Rasmussen encephalitis

Rasmussen encephalitis (RE) is a rare childhood neurological disease characterized by progressive unilateral loss of function, hemispheric atrophy and drug-resistant epilepsy. Affected brain tissue shows signs of infiltrating cytotoxic T-cells, microglial activation, and neuronal death, implicating an inflammatory disease process. Recent studies have identified molecular correlates of inflammation in RE, but cell-type-specific mechanisms remain unclear. We used single-nucleus RNA-sequencing (snRNA-seq) to assess gene expression across multiple cell types in brain tissue resected from two children with RE. We found transcriptionally distinct microglial populations enriched in RE compared to two age-matched individuals with unaffected brain tissue and two individuals with Type I focal cortical dysplasia (FCD). Specifically, microglia in RE tissues demonstrated increased expression of genes associated with cytokine signaling, interferon-mediated pathways, and T-cell activation. We extended these findings using spatial proteomic analysis of tissue from four surgical resections to examine expression profiles of microglia within their pathological context. Microglia that were spatially aggregated into nodules had increased expression of dynamic immune regulatory markers (PD-L1, CD14, CD11c), T-cell activation markers (CD40, CD80) and were physically located near distinct CD4+ and CD8+ lymphocyte populations. These findings help elucidate the complex immune microenvironment of RE.

The long and winding road: From mouse linkage studies to a novel human therapeutic pathway in type 1 diabetes

Autoimmunity involves a loss of immune tolerance to self-proteins due to a combination of genetic susceptibility and environmental provocation, which generates autoreactive T and B cells. Genetic susceptibility affects lymphocyte autoreactivity at the level of central tolerance (e.g., defective, or incomplete MHC-mediated negative selection of self-reactive T cells) and peripheral tolerance (e.g., failure of mechanisms to control circulating self-reactive T cells). T regulatory cell (Treg) mediated suppression is essential for controlling peripheral autoreactive T cells. Understanding the genetic control of Treg development and function and Treg interaction with T effector and other immune cells is thus a key goal of autoimmunity research. Herein, we will review immunogenetic control of tolerance in one of the classic models of autoimmunity, the non-obese diabetic (NOD) mouse model of autoimmune Type 1 diabetes (T1D). We review the long (and still evolving) elucidation of how one susceptibility gene, Cd137, (identified originally via linkage studies) affects both the immune response and its regulation in a highly complex fashion. The CD137 (present in both membrane and soluble forms) and the CD137 ligand (CD137L) both signal into a variety of immune cells (bi-directional signaling). The overall outcome of these multitudinous effects (either tolerance or autoimmunity) depends upon the balance between the regulatory signals (predominantly mediated by soluble CD137 via the CD137L pathway) and the effector signals (mediated by both membrane-bound CD137 and CD137L). This immune balance/homeostasis can be decisively affected by genetic (susceptibility vs. resistant alleles) and environmental factors (stimulation of soluble CD137 production). The discovery of the homeostatic immune effect of soluble CD137 on the CD137-CD137L system makes it a promising candidate for immunotherapy to restore tolerance in autoimmune diseases.

Immunological Subsets Characterization in Newly Diagnosed Relapsing-Remitting Multiple Sclerosis

Objectives

Using flow cytometry, we characterized myeloid, B, and T cells in patients recently diagnosed with relapsing–remitting multiple sclerosis (RRMS) naive to disease-modifying therapies (DMTs).

Methods

This prospective case–control study was conducted in the tertiary MS center of Catania, Italy. Demographic/clinical data and peripheral bloods were collected from 52 naive patients recently diagnosed with RRMS and sex/age-matched healthy controls (HCs) in a 2:1 ratio. We performed flow cytometry on isolated peripheral blood mononuclear cells to assess immune cell subsets differences between RMMS patients and HCs. We explored the biomarker potential of cell subsets using receiver operating characteristic (ROC) curves and relative area under the curve (AUC) analyses.

Results

Monocytic myeloid-derived suppressor cells (Mo-MDSCs CD14+/HLADR^−/low) and inflammatory monocytes (CD14+CD16+) displayed higher frequencies in RRMS patients when compared with HCs (p <.05). A lower percentage of B-unswitched memory cells was observed in RRMS patients when compared with HCs (p = .026). T cells had a higher frequency of T-helper CD4+ cells and their subset, CD4+CD161+, in RRMS patients when compared with HCs (p <.001). ROC analyses revealed an AUC >70% for Mo-MDSCs CD14+/HLADR^−/low and inflammatory CD14+CD16+, T-helper CD3+CD4+, and T-helper CD4+CD161+.

Conclusions

Patients with a recent RRMS diagnosis and naive to DMTs, showed peculiar myeloid, B-, and T-cell immunophenotypes.

Immune Checkpoint Ligand Bioengineered Schwann Cells as Antigen-Specific Therapy for Experimental Autoimmune Encephalomyelitis

Failure to establish immune tolerance leads to the development of autoimmune disease. The ability to regulate autoreactive T cells without inducing systemic immunosuppression represents a major challenge in the development of new strategies to treat autoimmune disease. Here, a translational method for bioengineering programmed death-ligand 1 (PD-L1)- and cluster of differentiation 86 (CD86)-functionalized mouse Schwann cells (SCs) to prevent and ameliorate multiple sclerosis (MS) in established mouse models of chronic and relapsing-remitting experimental autoimmune encephalomyelitis (EAE) is described. It is shown that the intravenous (i.v.) administration of immune checkpoint ligand functionalized mouse SCs modifies the course of disease and ameliorates EAE. Further, it is found that such bioengineered mouse SCs inhibit the differentiation of myelin-specific helper T cells into pathogenic T helper type-1 (Th 1) and type-17 (Th 17) cells, promote the development of tolerogenic myelin-specific regulatory T (Treg ) cells, and resolve inflammatory central nervous system microenvironments without inducing systemic immunosuppression.

Cladribine Alters Immune Cell Surface Molecules for Adhesion and Costimulation: Further Insights to the Mode of Action in Multiple Sclerosis

Cladribine (CLAD) is a deoxyadenosine analogue prodrug which is given in multiple sclerosis (MS) as two short oral treatment courses 12 months apart. Reconstitution of adaptive immune function following selective immune cell depletion is the presumed mode of action. In this exploratory study, we investigated the impact of CLAD tablets on immune cell surface molecules for adhesion (CAMs) and costimulation (CoSs) in people with MS (pwMS). We studied 18 pwMS who started treatment with CLAD and 10 healthy controls (HCs). Peripheral blood mononuclear cells were collected at baseline and every 3 months throughout a 24-month period. We analysed ICAM-1, LFA-1, CD28, HLADR, CD154, CD44, VLA-4 (CD49d/CD29), PSGL-1 and PD-1 with regard to their expression on B and T cells (T helper (Th) and cytotoxic T cells (cT)) and surface density (mean fluorescence intensity, MFI) by flow cytometry. The targeted analysis of CAM and CoS on the surface of immune cells in pwMS revealed a higher percentage of ICAM-1 (B cells, Th, cT), LFA-1 (B cells, cT), HLADR (B cells, cT), CD28 (cT) and CD154 (Th). In pwMS, we found lower frequencies of Th and cT cells expressing PSGL-1 and B cells for the inhibitory signal PD-1, whereas the surface expression of LFA-1 on cT and of HLADR on B cells was denser. Twenty-four months after the first CLAD cycle, the frequencies of B cells expressing CD44, CD29 and CD49d were lower compared with the baseline, together with decreased densities of ICAM-1, CD44 and HLADR. The rate of CD154 expressing Th cells dropped at 12 months. For cT, no changes were seen for frequency or density. Immune reconstitution by oral CLAD was associated with modification of the pro-migratory and -inflammatory surface patterns of CAMs and CoSs in immune cell subsets. This observation pertains primarily to B cells, which are key cells underlying MS pathogenesis.

Macrophage CD40 signaling drives experimental autoimmune encephalomyelitis

The costimulatory CD40L-CD40 dyad plays a major role in multiple sclerosis (MS). CD40 is highly expressed on MHCII+ B cells, dendritic cells and macrophages in human MS lesions. Here we investigated the role of the CD40 downstream signaling intermediates TNF receptor-associated factor 2 (TRAF2) and TRAF6 in MHCII+ cells in experimental autoimmune encephalomyelitis (EAE). Both MHCII-CD40-Traf2-/- and MHCII-CD40-Traf6-/- mice showed a reduction in clinical signs of EAE and prevented demyelination. However, only MHCII-CD40-Traf6-/- mice displayed a decrease in myeloid and lymphoid cell infiltration into the CNS that was accompanied by reduced levels of TNF-α, IL-6 and IFN-γ. As CD40-TRAF6 interactions predominantly occur in macrophages, we subjected CD40flfl LysMcre mice to EAE. This myeloid-specific deletion of CD40 resulted in a significant reduction in EAE severity, reduced CNS inflammation and demyelination. In conclusion, the CD40-TRAF6 signaling pathway in MHCII+ cells plays a key role in neuroinflammation and demyelination during EAE. Concomitant with the fact that CD40-TRAF6 interactions are predominant in macrophages, depletion of myeloid CD40 also reduces neuroinflammation. CD40-TRAF6 interactions thus represent a promising therapeutic target for MS. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

GBR 830, an anti-OX40, improves skin gene signatures and clinical scores in patients with atopic dermatitis

BACKGROUND

GBR 830 is a humanized mAb against OX40, a costimulatory receptor on activated T cells. OX40 inhibition might have a therapeutic role in T cell-mediated diseases, including atopic dermatitis (AD).

OBJECTIVE

This exploratory phase 2a study investigated the safety, efficacy, and tissue effects of GBR 830 in patients with AD.

METHODS

Patients with moderate-to-severe AD (affected body surface area, ≥10%; Eczema Area and Severity Index score, ≥12; and inadequate response to topical treatments) were randomized 3:1 to 10 mg/kg intravenous GBR 830 or placebo on day 1 (baseline) and day 29. Biopsy specimens were collected (n = 40) at days 1, 29, and 71. Primary end points included treatment-emergent adverse events (TEAEs) and changes from baseline in biomarkers (epidermal hyperplasia/cytokines) at days 29 and 71.

RESULTS

GBR 830 was well tolerated, with equal TEAE distribution (GBR 830, 63.0% [29/46]; placebo, 63.0% [10/16]). One serious TEAE in the GBR 830 group was deemed unrelated to study drug. At day 71, the proportion of intent-to-treat subjects achieving 50% or greater improvement in Eczema Area and Severity Index score was greater with GBR 830 (76.9% [20/26]) versus placebo (37.5% [3/8]). GBR 830 induced significant progressive reductions in T_H1 (IFN-γ/CXCL10), T_H2 (IL-31/CCL11/CCL17), and T_H17/T_H22 (IL-23p19/IL-8/S100A12) mRNA expression in lesional skin. Significant progressive reductions until day 71 in the drug group were seen in OX40⁺ T cells and OX40L⁺ dendritic cells (P < .001). Hyperplasia measures (thickness/keratin 16/Ki67) showed greater reductions with GBR 830 (P < .001).

CONCLUSIONS

Two doses of GBR 830 administered 4 weeks apart were well tolerated and induced significant progressive tissue and clinical changes until day 71 (42 days after the last dose), highlighting the potential of OX40 targeting in patients with AD.

Subsets of activated monocytes and markers of inflammation in incipient and progressed multiple sclerosis

Multiple sclerosis (MS) is an immune mediated, inflammatory and demyelinating disease of the central nervous system (CNS). Substantial evidence points toward monocytes and macrophages playing prominent roles early in disease, mediating both pro- and anti-inflammatory responses. Monocytes are subdivided into three subsets depending on the expression of CD14 and CD16, representing different stages of inflammatory activation. To investigate their involvement in MS, peripheral blood mononuclear cells from 40 patients with incipient or progressed MS and 20 healthy controls were characterized ex vivo. In MS samples, we demonstrate a highly significant increase in nonclassical monocytes (CD14+CD16++), with a concomitant significant reduction in classical monocytes (CD14++CD16-) compared with healthy controls. Also, a significant reduction in the surface expression of CD40, CD163, and CD192 was found, attributable to the upregulation of the nonclassical monocytes. In addition, significantly increased levels of human endogenous retrovirus (HERV) envelope (Env) epitopes, encoded by both HERV-H/F and HERV-W, were specifically found on nonclassical monocytes from patients with MS; emphasizing their involvement in MS disease. In parallel, serum and cerebrospinal fluid (CSF) samples were analyzed for soluble biomarkers of inflammation and neurodegeneration. For sCD163 versus CD163, no significant correlations were found, whereas highly significant correlations between levels of soluble neopterine and the intermediate monocyte (CD14++CD16+) population was found, as were correlations between levels of soluble osteopontin and the HERV Env expression on nonclassical monocytes. The results from this study emphasize the relevance of further focus on monocyte subsets, particularly the nonclassical monocytes in monitoring of inflammatory diseases.

Inhibition of CD40-TRAF6 interactions by the small molecule inhibitor 6877002 reduces neuroinflammation

BACKGROUND

The influx of leukocytes into the central nervous system (CNS) is a key hallmark of the chronic neuro-inflammatory disease multiple sclerosis (MS). Strategies that aim to inhibit leukocyte migration across the blood-brain barrier (BBB) are therefore regarded as promising therapeutic approaches to combat MS. As the CD40L-CD40 dyad signals via TNF receptor-associated factor 6 (TRAF6) in myeloid cells to induce inflammation and leukocyte trafficking, we explored the hypothesis that specific inhibition of CD40-TRAF6 interactions can ameliorate neuro-inflammation.

METHODS

Human monocytes were treated with a small molecule inhibitor (SMI) of CD40-TRAF6 interactions (6877002), and migration capacity across human brain endothelial cells was measured. To test the therapeutic potential of the CD40-TRAF6-blocking SMI under neuro-inflammatory conditions in vivo, Lewis rats and C57BL/6J mice were subjected to acute experimental autoimmune encephalomyelitis (EAE) and treated with SMI 6877002 for 6 days (rats) or 3 weeks (mice).

RESULTS

We here show that a SMI of CD40-TRAF6 interactions (6877002) strongly and dose-dependently reduces trans-endothelial migration of human monocytes. Moreover, upon SMI treatment, monocytes displayed a decreased production of ROS, tumor necrosis factor (TNF), and interleukin (IL)-6, whereas the production of the anti-inflammatory cytokine IL-10 was increased. Disease severity of EAE was reduced upon SMI treatment in rats, but not in mice. However, a significant reduction in monocyte-derived macrophages, but not in T cells, that had infiltrated the CNS was eminent in both models.

CONCLUSIONS

Together, our results indicate that SMI-mediated inhibition of the CD40-TRAF6 pathway skews human monocytes towards anti-inflammatory cells with reduced trans-endothelial migration capacity, and is able to reduce CNS-infiltrated monocyte-derived macrophages during neuro-inflammation, but minimally ameliorates EAE disease severity. We therefore conclude that SMI-mediated inhibition of the CD40-TRAF6 pathway may represent a beneficial treatment strategy to reduce monocyte recruitment and macrophage activation in the CNS and has the potential to be used as a co-treatment to combat MS.

Oral administration of the nitroxide radical TEMPOL exhibits immunomodulatory and therapeutic properties in multiple sclerosis models

Therapies with both immunomodulatory and neuroprotective properties are thought to have the greatest promise in reducing the severity and progression of multiple sclerosis (MS). Several reactive oxygen (ROS) and reactive nitrogen species (RNS) are implicated in inflammatory-mediated damage to the central nervous system (CNS) in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) is a stable nitroxide radical with potent antioxidant activity. The goal of our studies was to investigate the immunomodulatory effects and therapeutic potential of orally-delivered TEMPOL in the mouse EAE model. Mice receiving TEMPOL chow ad libitum for 2weeks prior to induction of active EAE showed delayed onset and reduced incidence of disease compared to control-fed animals. Reduced disease severity was associated with limited microglial activation and fewer inflammatory infiltrates. TEMPOL's effects were immunomodulatory, not immunosuppressive: T cells produced less interferon-γ and tumor necrosis factor-α, and TEMPOL-fed mice exhibited a shift towards T_H2-type antibody responses. Both myeloid and myeloid-dendritic cells of TEMPOL-fed EAE animals had significantly lower levels of MHC class II expression than controls; CD40 was also significantly reduced. TEMPOL administration was associated with an enrichment of CD8⁺ T cell populations and CD4⁺FoxP₃⁺ regulatory populations. TEMPOL reduced the severity of clinical disease when administered after the induction of disease, and also after the onset of clinical symptoms. To exclude effects on T cell priming in vivo, TEMPOL was tested with the passive transfer of encephalitogenic T cells and was found to reduce the incidence and peak severity of disease. Protection was associated with reduced infiltrates and a relative sparing of neurofilaments and axons. The ability of oral TEMPOL to reduce inflammation and axonal damage and loss demonstrate both anti-inflammatory and protective properties, with significant promise for the treatment of MS and related neurological disorders.

Translational utility of experimental autoimmune encephalomyelitis: recent developments

Multiple sclerosis (MS) is a complex autoimmune condition with firmly established genetic and environmental components. Genome-wide association studies (GWAS) have revealed a large number of genetic polymorphisms in the vicinity of, and within, genes that associate to disease. However, the significance of these single-nucleotide polymorphisms in disease and possible mechanisms of action remain, with a few exceptions, to be established. While the animal model for MS, experimental autoimmune encephalomyelitis (EAE), has been instrumental in understanding immunity in general and mechanisms of MS disease in particular, much of the translational information gathered from the model in terms of treatment development (glatiramer acetate and natalizumab) has been extensively summarized. In this review, we would thus like to cover the work done in EAE from a GWAS perspective, highlighting the research that has addressed the role of different GWAS genes and their pathways in EAE pathogenesis. Understanding the contribution of these pathways to disease might allow for the stratification of disease subphenotypes in patients and in turn open the possibility for new and individualized treatment approaches in the future.

The effect of single course high dose dexamethasone on CD28/CTLA-4 balance in the treatment of patients with newly diagnosed primary immune thrombocytopenia

To evaluate the effect of a single course of high dose dexamethasone (HD-DXM) on CD28 and CTLA-4 expression in patients with newly-diagnosed primary immune thrombocytopenia (ITP). Twenty-8 ITP patients (18 females and 10 males, age range 18–65 years, median age 38.5 years) enrolled in this study and 26 healthy volunteers (19 women and 7 men, age range 16–66 years, median age 37 years) served as a control group. The patients were treated with HD-DXM (40 mg/day) for 4 consecutive days. CD28 and CTLA-4 expression was assessed by flow cytometry once-monthly for 6 months. Plasma levels of the cytokines IFN-γ and IL-10 were determined by enzyme-linked immunosorbent assay. One month after treatment, a platelet response was observed in 23 (82%) of the patients. The response rates over the next 5 months were 71%, 57%, 53%, 46%, and 39%, chronologically. We observed a significant decrease in CD28 expression after the first month (34.7 ± 4.8% vs. 44.5 ± 4.4% before treatment), after which the CD28 levels gradually increased. In contrast, CTLA-4 expression increased after the first month (3.2 ± 0.5% vs. 0.8 ± 0.4 before treatment), after which the CTLA-4 levels gradually decreased. Similar dynamic changes were seen in the levels of IFN-γ and IL-10. The dynamic changes of CD28 and CTLA-4 were consistent with those of IFN-γ and IL-10 and with the effectiveness of HD-DXM in the treatment of ITP. Our results suggest that a disturbed CD28/CTLA-4 balance may contribute to the immunopathogenesis of ITP.

Can we switch microglia's phenotype to foster neuroprotection? Focus on multiple sclerosis

Microglia cells, the resident innate immune cells in the brain, are highly active, extending and retracting highly motile processes through which they continuously survey their microenvironment for 'danger signals' and interact dynamically with surrounding cells. Upon sensing changes in their central nervous system microenvironment, microglia become activated, undergoing morphological and functional changes. Microglia activation is not an 'all-or-none' process, but rather a continuum depending on encountered stimuli, which is expressed through a spectrum of molecular and functional phenotypes ranging from so-called 'classically activated', with a highly pro-inflammatory profile, to 'alternatively activated' associated with a beneficial, less inflammatory, neuroprotective profile. Microglia activation has been demonstrated in most neurological diseases of diverse aetiology and has been implicated as a contributor to neurodegeneration. The possibility to promote microglia's neuroprotective phenotype has therefore become a therapeutic goal. We have focused our discussion on the role of microglia in multiple sclerosis, a prototype of inflammatory, demyelinating, neurodegenerative disease, and on the effect of currently approved or on-trial anti-inflammatory therapeutic strategies that might mediate neuroprotection at least in part through their effect on microglia by modifying their behaviour via a switch of their functional phenotype from a detrimental to a protective one. In addition to pharmaceutical approaches, such as treatment with glatiramer acetate, interferon-β, fingolimod or dimethyl fumarate, we address the alternative therapeutic approach of treatment with mesenchymal stem cells and their potential role in neuroprotection through their 'calming' effect on microglia.

Pathogenesis of pediatric multiple sclerosis

Onset of multiple sclerosis in childhood occurs in 3-5% of patients. There is limited, but growing knowledge about the underlying pathobiology of pediatric MS. It is crucial to better understand this area in order to address central questions in the field: 1) Can pediatric multiple sclerosis inform us about factors related to disease initiation and propagation? 2) What are the biomarkers of disease course in pediatric multiple sclerosis; 3) Does pediatric multiple sclerosis pathogenesis differ from adult-onset multiple sclerosis; 4) How can we optimize treatment in pediatric demyelinating diseases? 5) Can pediatric multiple sclerosis provide insights into the environmental risk factors for multiple sclerosis in general? Here we review the current knowledge of the pathogenesis of multiple sclerosis in children, and address the five questions raised above.

Uncovering the genetic architecture of multiple sclerosis

Multiple sclerosis (MS) is a disease in which genetic, environmental, and stochastic factors interact to trigger an inflammatory disease of the CNS that also has a neurodegenerative component. Over the past 3 years, progress in high-throughput technologies and analysis methods has synergized with the collaborative efforts of investigators studying MS genetics to enable the discovery of more than a dozen genes involved in making individuals susceptible to MS. These genes are beginning to suggest molecular pathways that may be particularly vulnerable to genetic variation in MS. Soon, a comprehensive map of common genetic variants affecting MS susceptibility will be assembled, and communal efforts will need to focus on the more challenging issue of understanding the genetic architecture of disease course and treatment response in MS. Early efforts integrating different dimensions of information, including genomics, imaging, transcriptomics, and proteomics, with precise phenotypic data from clinicians illustrate the way forward for prognostic algorithms in MS and suggest that these approaches will yield a new series of insights in the next decade.

The CD4+ T-cell subset lacking expression of the CD28 costimulatory molecule is expanded and shows a higher activation state in multiple sclerosis

Multiple sclerosis (MS) is a chronic debilitating disease, in which T-cells are considered to play a pivotal role. CD28 is the quintessential costimulatory molecule on T-cells and its expression declines progressively with repeated stimulations, leading to the generation of CD28(-) T-cells. Our aim was to examine whether CD4(+)CD28(-) T-cells were enriched in MS patients, and characterize the phenotype of this subset in MS patients and healthy controls (HC). All these changes could provide these CD4(+)CD28(-) T-cell characteristics that might be involved in the pathogenesis of MS, turning this T-cell subset into a potential target for future therapeutic strategies.

Imbalance in T-cell and cytokine profiles in patients with relapsing-remitting multiple sclerosis

Multiple sclerosis (MS) is characterized by autoimmune attack leading to demyelination of the white matter in the central nervous system with devastating clinical consequences. Several immune-mediated destruction mechanisms were previously proposed including different T-cell subsets but complex view on immune system function in patients with MS is missing. In the present study, T-lymphocyte populations and pro-inflammatory as well as suppressive cytokine profiles were evaluated in detail in previously untreated patients with relapsing-remitting MS (RRMS). CD4(+) and CD8(+) naïve, central memory (Tcm), effector memory (Tem), terminal effector memory (Ttem), CD4(+) regulatory T-cells (Treg) and CD8(+) T-suppressor cells (Ts) were analysed using flow cytometry, and levels of ten plasma cytokines were determined using fluorescent bead-based immunoassay. We evaluated two groups of RRMS with minor (n=33) and major (n=25) clinical impairment and compared them with healthy controls (n=40) in order to detect any correlation between severity of MS clinical symptoms and immune disturbances. Significant differences were noted in CD4(+)CD45RA(+)CCR7(+) naïve T-cells, CD4(+)CD45RO(+)CCR7(-) and CD8(+)CD45RO(+)CCR7(-) Tem cells, while no differences were recognized in Tcm, Ttem, Treg and Ts cells in RRMS patients. Nine out of ten studied cytokines were disturbed in plasma samples of patients with RRMS. In conclusion, we demonstrate complex immune dysbalances in untreated MS patients.

Taenia crassiceps infection abrogates experimental autoimmune encephalomyelitis

Helminth infections induce strong immunoregulation that can modulate subsequent pathogenic challenges. Taenia crassiceps causes a chronic infection that induces a Th2-biased response and modulates the host cellular immune response, including reduced lymphoproliferation in response to mitogens, impaired antigen presentation and the recruitment of suppressive alternatively activated macrophages (AAMФ). In this study, we aimed to evaluate the ability of T. crassiceps to reduce the severity of experimental autoimmune encephalomyelitis (EAE). Only 50% of T. crassiceps-infected mice displayed EAE symptoms, which were significantly less severe than uninfected mice. This effect was associated with both decreased MOG-specific splenocyte proliferation and IL-17 production and limited leukocyte infiltration into the spinal cord. Infection with T. crassiceps induced an anti-inflammatory cytokine microenvironment, including decreased TNF-α production and high MOG-specific production of IL-4 and IL-10. While the mRNA expression of TNF-α and iNOS was lower in the brain of T. crassiceps-infected mice with EAE, markers for AAMФ were highly expressed. Furthermore, in these mice, there was reduced entry of CD3(+)Foxp3(-) cells into the brain. The T. crassiceps-induced immune regulation decreased EAE severity by dampening T cell activation, proliferation and migration to the CNS.

Characterization of human platelet binding of recombinant T cell receptor ligand

Background

Recombinant T cell receptor ligands (RTLs) are bio-engineered molecules that may serve as novel therapeutic agents for the treatment of neuroinflammatory conditions such as multiple sclerosis (MS). RTLs contain membrane distal α1 plus β1 domains of class II major histocompatibility complex linked covalently to specific peptides that can be used to regulate T cell responses and inhibit experimental autoimmune encephalomyelitis (EAE). The mechanisms by which RTLs impede local recruitment and retention of inflammatory cells in the CNS, however, are not completely understood.

Methods

We have recently shown that RTLs bind strongly to B cells, macrophages, and dendritic cells, but not to T cells, in an antigenic-independent manner, raising the question whether peripheral blood cells express a distinct RTL-receptor. Our study was designed to characterize the molecular mechanisms by which RTLs bind human blood platelets, and the ability of RTL to modulate platelet function.

Results

Our data demonstrate that human blood platelets support binding of RTL. Immobilized RTL initiated platelet intracellular calcium mobilization and lamellipodia formation through a pathway dependent upon Src and PI3 kinases signaling. The presence of RTL in solution reduced platelet aggregation by collagen, while treatment of whole blood with RTL prolonged occlusive thrombus formation on collagen.

Conclusions

Platelets, well-known regulators of hemostasis and thrombosis, have been implicated in playing a major role in inflammation and immunity. This study provides the first evidence that blood platelets express a functional RTL-receptor with a putative role in modulating pathways of neuroinflammation.

Role of platelets in neuroinflammation: a wide-angle perspective

OBJECTIVES

This review summarizes recent developments in platelet biology relevant to neuroinflammatory disorders. Multiple sclerosis (MS) is taken as the "Poster Child" of these disorders but the implications are wide. The role of platelets in inflammation is well appreciated in the cardiovascular and cancer research communities but appears to be relatively neglected in neurological research.

ORGANIZATION

After a brief introduction to platelets, topics covered include the matrix metalloproteinases, platelet chemokines, cytokines and growth factors, the recent finding of platelet PPAR receptors and Toll-like receptors, complement, bioactive lipids, and other agents/functions likely to be relevant in neuroinflammatory diseases. Each section cites literature linking the topic to areas of active research in MS or other disorders, including especially Alzheimer's disease.

CONCLUSION

The final section summarizes evidence of platelet involvement in MS. The general conclusion is that platelets may be key players in MS and related disorders, and warrant more attention in neurological research.

B7-H1 restricts neuroantigen-specific T cell responses and confines inflammatory CNS damage: implications for the lesion pathogenesis of multiple sclerosis

The co-inhibitory B7-homologue 1 (B7-H1/PD-L1) influences adaptive immune responses and has been proposed to contribute to the mechanisms maintaining peripheral tolerance and limiting inflammatory damage in parenchymal organs. To understand the B7-H1/PD1 pathway in CNS inflammation, we analyzed adaptive immune responses in myelin oligodendrocyte glycoprotein (MOG)(35-55)-induced EAE and assessed the expression of B7-H1 in human CNS tissue. B7-H1(-/-) mice exhibited an accelerated disease onset and significantly exacerbated EAE severity, although absence of B7-H1 had no influence on MOG antibody production. Peripheral MOG-specific IFN-gamma/IL-17 T cell responses occurred earlier and enhanced in B7-H1(-/-) mice, but ceased more rapidly. In the CNS, however, significantly higher numbers of activated neuroantigen-specific T cells persisted during all stages of EAE. Experiments showing a direct inhibitory role of APC-derived B7-H1 on the activation of MOG-specific effector cells support the assumption that parenchymal B7-H1 is pivotal for delineating T cell fate in the target organ. Compatible with this concept, our data investigating human brain tissue specimens show a strong up-regulation of B7-H1 in lesions of multiple sclerosis. Our findings demonstrate the critical importance of B7-H1 as an immune-inhibitory molecule capable of down-regulating T cell responses thus contributing to the confinement of immunopathological damage.

Distinct functions of autoreactive memory and effector CD4+ T cells in experimental autoimmune encephalomyelitis

The persistence of human autoimmune diseases is thought to be mediated predominantly by memory T cells. We investigated the phenotype and migration of memory versus effector T cells in vivo in experimental autoimmune encephalomyelitis (EAE). We found that memory CD4(+) T cells up-regulated the activation marker CD44 as well as CXCR3 and ICOS, proliferated more and produced more interferon-gamma and less interleukin-17 compared to effector T cells. Moreover, adoptive transfer of memory T cells into T cell receptor (TCR)alphabeta(-/-) recipients induced more severe disease than did effector CD4(+) T cells with marked central nervous system inflammation and axonal damage. The uniqueness of disease mediated by memory T cells was confirmed by the differential susceptibility to immunomodulatory therapies in vivo. CD28-B7 T cell costimulatory signal blockade by CTLA4Ig suppressed effector cell-mediated EAE but had minimal effects on disease induced by memory cells. In contrast, ICOS-B7h blockade exacerbated effector T cell-induced EAE but protected from disease induced by memory T cells. However, blockade of the OX40 (CD134) costimulatory pathway ameliorated disease mediated by both memory and effector T cells. Our data extend the understanding of the pathogenicity of autoreactive memory T cells and have important implications for the development of novel therapies for human autoimmune diseases.

Effects of interferon-β on co-signaling molecules: upregulation of CD40, CD86 and PD-L2 on monocytes in relation to clinical response to interferon-β treatment in patients with multiple sclerosis

Interferon-beta (IFN-β) reduces disease activity in a subgroup of patients with relapsing remitting multiple sclerosis (MS). The mechanism of action as well as the pathophysiological basis of responsiveness to IFN-β is not well understood. Since T-cell activation plays an important part in the pathophysiology of MS, we here investigated the effect of IFN-β on the expression of co-signaling pathways (CD28—CD80/CD86, CD154—CD40, ICOS—ICOSL, PD-1—PD-L1/2) in MS patients and correlated the results with the clinical response to IFN-β in individual patients. Expression of co-signaling molecules was measured by flow cytometry in vitro on peripheral blood mononuclear cells after incubation with IFN-β, and in vivo in whole blood samples of 32 untreated and 24 IFN-β treated MS patients, including 13 patients longitudinal. IFN-β treatment induced upregulation of CD40, CD80, CD86, PD-L1 and PD-L2 on monocytes as well as PD-L1 on CD4+-T-cells in vitro and in vivo. IFN-β treated MS patients were grouped into responders and non-responders on the basis of Kurtzkés EDSS (expanded disability status scale) progression and relapse rate. Upregulation of CD40, CD86 and PD-L2 on monocytes was associated with treatment response to IFN-β ( P < 0.001, P = 0.028 and P = 0.028, respectively). Our results show that IFN-β upregulates co-stimulatory as well as co-inhibitory molecules in vitro and in vivo implicating that modulation of the balance between positive and negative co-stimulatory signals might be an important part of the mechanism of action of IFN-β in MS. Upregulation of the expression of CD40, CD86 and PD-L2 may be useful as a predictive marker for clinical response to IFN-β treatment at early timepoints during IFN-β therapy. Multiple Sclerosis 2008; 14: 166—176. http://msj.sagepub.com

Differential engagement of Tim-1 during activation can positively or negatively costimulate T cell expansion and effector function

It has been suggested that T cell immunoglobulin mucin (Tim)-1 expressed on T cells serves to positively costimulate T cell responses. However, crosslinking of Tim-1 by its ligand Tim-4 resulted in either activation or inhibition of T cell responses, thus raising the issue of whether Tim-1 can have a dual function as a costimulator. To resolve this issue, we tested a series of monoclonal antibodies specific for Tim-1 and identified two antibodies that showed opposite functional effects. One anti–Tim-1 antibody increased the frequency of antigen-specific T cells, the production of the proinflammatory cytokines IFN-γ and IL-17, and the severity of experimental autoimmune encephalomyelitis. In contrast, another anti–Tim-1 antibody inhibited the generation of antigen-specific T cells, production of IFN-γ and IL-17, and development of autoimmunity, and it caused a strong Th2 response. Both antibodies bound to closely related epitopes in the IgV domain of the Tim-1 molecule, but the activating antibody had an avidity for Tim-1 that was 17 times higher than the inhibitory antibody. Although both anti–Tim-1 antibodies induced CD3 capping, only the activating antibody caused strong cytoskeletal reorganization and motility. These data indicate that Tim-1 regulates T cell responses and that Tim-1 engagement can alter T cell function depending on the affinity/avidity with which it is engaged.

The role of CD4 T cells in the pathogenesis of multiple sclerosis

T lymphocytes play a central role in the pathogenesis of multiple sclerosis (MS) (Zhang et al., 1992). Both CD4+ and CD8+ T cells have been demonstrated in MS lesions, with CD4+ T cells predominating in acute lesions and CD8+ T cells being observed more frequently in chronic lesions (Raine, 1994). Additionally, T cells are found in all four of the described histopathologic subtypes of MS (Lucchinetti et al., 2000). Activated myelin-reactive CD4+ T cells are present in the blood and cerebrospinal fluid (CSF) of MS patients; in contrast, only nonactivated myelin-reactive T cells are present in the blood of controls (Zhang et al., 1994). The success of several T-cell-targeted therapies in MS reinforces the importance of the role of the T cell in MS pathogenesis. Here, we outline basic concepts in CD4+ T-cell immunology and summarize the current understanding of the role of CD4+ T cells in the pathogenesis of MS.

PD-1/PD-L1, but not PD-1/PD-L2, interactions regulate the severity of experimental autoimmune encephalomyelitis

Interactions between PD-1 and its two differentially expressed ligands, PD-L1 and PD-L2, attenuate T cell activation and effector function. To determine the role of these molecules in autoimmune disease of the CNS, PD-1-/-, PD-L1-/- and PD-L2-/- mice were generated and immunized to induce experimental autoimmune encephalomyelitis (EAE). PD-1-/- and PD-L1-/- mice developed more severe EAE than wild type and PD-L2-/- mice. Consistent with this, PD-1-/- and PD-L1-/- cells produced elevated levels of the pro-inflammatory cytokines IFN-gamma, TNF, IL-6 and IL-17. These results demonstrate that interactions between PD-1/PD-L1, but not PD-1/PDL-2, are crucial in attenuating T cell responses in EAE.

CD40 expression by microglial cells is required for their completion of a two-step activation process during central nervous system autoimmune inflammation

Microglial cells are monocytic lineage cells that reside in the CNS and have the capacity to become activated during various pathological conditions. Although it was demonstrated that activation of microglial cells could be achieved in vitro by the engagement of CD40-CD40L interactions in combination with proinflammatory cytokines, the exact factors that mediate activation of microglial cells in vivo during CNS autoimmunity are ill-defined. To investigate the role of CD40 in microglial cell activation during experimental autoimmune encephalomyelitis (EAE), we used bone marrow chimera mice that allowed us to distinguish microglial cells from peripheral macrophages and render microglial cells deficient in CD40. We found that the first step of microglial cell activation was CD40-independent and occurred during EAE onset. The first step of activation consisted of microglial cell proliferation and up-regulation of the activation markers MHC class II, CD40, and CD86. At the peak of disease, microglial cells underwent a second step of activation, which was characterized by a further enhancement in activation marker expression along with a reduction in proliferation. The second step of microglial cell activation was CD40-dependent and the failure of CD40-deficient microglial cells to achieve a full level of activation during EAE was correlated with reduced expansion of encephalitogenic T cells and leukocyte infiltration in the CNS, and amelioration of clinical symptoms. Thus, our findings demonstrate that CD40 expression on microglial cells is necessary to complete their activation process during EAE, which is important for disease progression.

Effects of sex hormones on costimulatory molecule expression in multiple sclerosis

Sex hormones play a central role as modulators of immune responses and autoimmune diseases. We hypothesized that suppression of MS disease during pregnancy may be mediated by sex steroid hormones via regulation of costimulatory molecules such as CD40L or CD80/CD86 (B7-1/B7-2). We tested two sex hormones that are implicated in immune suppression during pregnancy: estriol and progesterone. We also examined whether this regulation is gender-specific or disease-related. PBMC from untreated relapsing remitting multiple sclerosis (RR MS) patients and controls were examined for expression of T cell and monocyte costimulatory molecules following mitogen stimulation in the presence or absence of sex hormones. In the absence of hormones, we confirmed that mitogen stimulation induced significantly more CD40L on the surface of CD4(+)T cells in MS patients compared to controls, and we extend these findings by showing there were no gender differences in induction of CD40L. Although supra-physiologic doses of hormones mildly suppressed CD40L expression on activated T cells, in vitro exposure to typical pregnancy-related physiologic doses of estriol or progesterone showed very little or no suppression of CD40L. On monocytes, neither estriol nor progesterone significantly altered the expression of CD80/CD86. These results suggest that physiologic doses of estriol or progesterone cannot alter CD40L on T cells or CD80/CD86 on monocytes sufficiently to explain the improvement observed in MS during pregnancy. Thus, although amelioration of MS and other autoimmune diseases during pregnancy is thought to be due to increased sex hormones, the present results do not support a role for suppression of costimulation via estriol or progesterone.

Vitamin K2 ameliorates experimental autoimmune encephalomyelitis in Lewis rats

Vitamin K2 (VK2), which has been in wide use for the management of hypoprothrombinemia and osteoporosis in Japan, was tested for its efficacy on experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). The severity of EAE was significantly ameliorated by the prophylactic administration of VK2, though it was not effective when given after the onset. Inflammatory cellular infiltration and the expression of both MHC class II and inducible nitric oxide synthase (iNOS) were reduced in the spinal cords of VK2-treated rats with EAE. The inhibitory effect of VK2 on the iNOS expression in glial cells was also observed in vitro. Considering the long use of VK2 without noticeable untoward effects, it may be applicable to the patients with MS.

Immunology of multiple sclerosis

Multiple sclerosis (MS) develops in young adults with a complex predisposing genetic trait and probably requires an inciting environmental insult such as a viral infection to trigger the disease. The activation of CD4+ autoreactive T cells and their differentiation into a Th1 phenotype are a crucial events in the initial steps, and these cells are probably also important players in the long-term evolution of the disease. Damage of the target tissue, the central nervous system, is, however, most likely mediated by other components of the immune system, such as antibodies, complement, CD8+ T cells, and factors produced by innate immune cells. Perturbations in immunomodulatory networks that include Th2 cells, regulatory CD4+ T cells, NK cells, and others may in part be responsible for the relapsing-remitting or chronic progressive nature of the disease. However, an important paradigmatic shift in the study of MS has occurred in the past decade. It is now clear that MS is not just a disease of the immune system, but that factors contributed by the central nervous system are equally important and must be considered in the future.

Therapeutic peptidomimetic strategies for autoimmune diseases: costimulation blockade*

Cognate interactions between immune effector cells and antigen-presenting cells (APCs) govern immune responses. Specific signals occur between the T-cell receptor peptide and APCs and nonspecific signals between pairs of costimulatory molecules. Costimulation signals are required for full T-cell activation and are assumed to regulate T-cell responses as well as other aspects of the immune system. As new discoveries are made, it is becoming clear how important these costimulation interactions are for immune responses. Costimulation requirements for T-cell regulation have been extensively studied as a way to control many autoimmune diseases and downregulate inflammatory reactions. The CD28:B7 and the CD40:CD40L families of molecules are considered to be critical costimulatory molecules and have been studied extensively. Blocking the interaction between these molecules results in a state of immune unresponsiveness termed 'anergy'. Several different strategies for blockade of these interactions are explored including monoclonal antibodies (mAbs), Fab fragments, chimeric, and/or fusion proteins. We developed novel, immune-specific approaches that interfere with these interactions. Using experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis mediated by central nervous system (CNS)-specific T-cells, we developed a multi-targeted approach that utilizes peptides for blockade of costimulatory molecules. We designed blocking peptide mimics that retain the functional binding area of the parent protein while reducing the overall size and are thus capable of blocking signal transduction. In this paper, we review the role of costimulatory molecules in autoimmune diseases, two of the most well-studied costimulatory pathways (CD28/CTLA-4:B7 and CD40:CD40L), and the advantages of peptidomimetic approaches. We present data showing the ability of peptide mimics of costimulatory molecules to suppress autoimmune disease and propose a mechanism for disease suppression.