The role of costimulation in autoimmune demyelination

Vitamin D as a Risk Factor for Multiple Sclerosis: Immunoregulatory or Neuroprotective?

Vitamin D insufficiency during childhood has been linked to the development of multiple sclerosis (MS), typically an adult-onset inflammatory demyelinating disease of the central nervous system (CNS). Since vitamin D was known to have immunoregulatory properties on both innate and adaptive immunity, it was hypothesized that low vitamin D resulted in aberrant immune responses and the development of MS. However, vitamin D receptors are present on many cell types, including neurons, oligodendrocytes, astrocytes and microglia, and vitamin D has profound effects on development and function of the CNS. This leads to the possibility that low vitamin D may alter the CNS in a manner that makes it vulnerable to inflammation and the development of MS. This review analysis the role of vitamin D in the immune and nervous system, and how vitamin D insufficiency in children may contribute to the development of MS.

Acute CNS demyelination in a subject with cerebellar ataxia following the first dose of COVID-19 vaccine; a case report

Vaccination-induced demyelination is a rare, unusual side effect of certain vaccines which can cause significant damage to patient's sensory-motor abilities within days. Although COVID-19 vaccines go through rigorous clinical trials before they are injected to the general population, certain unexpected side effects remain inevitable. We herein describe a case of a 42-year-old woman who experienced acute demyelination 10 days after the Oxford-AstraZeneca vaccination. To the best of our knowledge, this is the first case of such nature and severity described regarding COVID-19 vaccines' side effects.

Emerging Therapeutics for Immune Tolerance: Tolerogenic Vaccines, T cell Therapy, and IL-2 Therapy

Autoimmune diseases affect roughly 5-10% of the total population, with women affected more than men. The standard treatment for autoimmune or autoinflammatory diseases had long been immunosuppressive agents until the advent of immunomodulatory biologic drugs, which aimed at blocking inflammatory mediators, including proinflammatory cytokines. At the frontier of these biologic drugs are TNF-α blockers. These therapies inhibit the proinflammatory action of TNF-α in common autoimmune diseases such as rheumatoid arthritis, psoriasis, ulcerative colitis, and Crohn's disease. TNF-α blockade quickly became the "standard of care" for these autoimmune diseases due to their effectiveness in controlling disease and decreasing patient's adverse risk profiles compared to broad-spectrum immunosuppressive agents. However, anti-TNF-α therapies have limitations, including known adverse safety risk, loss of therapeutic efficacy due to drug resistance, and lack of efficacy in numerous autoimmune diseases, including multiple sclerosis. The next wave of truly transformative therapeutics should aspire to provide a cure by selectively suppressing pathogenic autoantigen-specific immune responses while leaving the rest of the immune system intact to control infectious diseases and malignancies. In this review, we will focus on three main areas of active research in immune tolerance. First, tolerogenic vaccines aiming at robust, lasting autoantigen-specific immune tolerance. Second, T cell therapies using Tregs (either polyclonal, antigen-specific, or genetically engineered to express chimeric antigen receptors) to establish active dominant immune tolerance or T cells (engineered to express chimeric antigen receptors) to delete pathogenic immune cells. Third, IL-2 therapies aiming at expanding immunosuppressive regulatory T cells in vivo.

Immune profile of an atypical EAE model in marmoset monkeys immunized with recombinant human myelin oligodendrocyte glycoprotein in incomplete Freund's adjuvant

Background

Experimental autoimmune encephalomyelitis (EAE) in the common marmoset monkey (Callithrix jacchus) is a relevant preclinical model for translational research into immunopathogenic mechanisms operating in multiple sclerosis (MS). Prior studies showed a core pathogenic role of T and B cells specific for myelin oligodendrocyte glycoprotein (MOG). However, in those studies, the quality of the response against MOG epitopes was strongly biased by bacterial antigens in the complete Freund’s adjuvant (CFA), in which the immunizing recombinant human (rh) MOG protein had been formulated. In response to the need of a more refined EAE model, we have tested whether disease could also be induced with rhMOG in incomplete Freund’s adjuvant (IFA).

Method

Marmosets were immunized with rhMOG emulsified in IFA in the dorsal skin. Monkeys that did not develop neurological deficit were given booster immunizations at 28-day interval with the same antigen preparation. In a second experiment, three marmoset twin pairs were sensitized against MOG peptides in IFA to study a possibility for suppressive activity towards pathogenic T cells directed against the encephalitogenic epitope MOG40-48.

Results

Despite the absence of strong danger signals in the rhMOG/IFA inoculum, all monkeys developed clinically evident EAE symptoms. Moreover, in all monkeys, demyelinated lesions were present in the white matter and in two cases also in the cortical grey matter. Immune profiling at height of the disease showed a dominant T cell response against the overlapping peptides 14–36 and 24–46, but reactivity against the pathogenically most relevant peptide 34–56 was conspicuously absent. In the second experiment, there was an indication for a possible suppressive mechanism.

Conclusions

Immunization of marmoset monkeys with rhMOG in IFA elicits clinical EAE in all animals. Moreover, rhMOG contains pathogenic and regulatory epitopes, but the pathogenic hierarchy of rhMOG epitopes is strongly influenced by the adjuvant in which the protein is formulated.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0378-5) contains supplementary material, which is available to authorized users.

R-flurbiprofen attenuates experimental autoimmune encephalomyelitis in mice

R-flurbiprofen is the non-cyclooxygenase inhibiting R-enantiomer of the non-steroidal anti-inflammatory drug flurbiprofen, which was assessed as a remedy for Alzheimer's disease. Because of its anti-inflammatory, endocannabinoid-modulating and antioxidative properties, combined with low toxicity, the present study assessed R-flurbiprofen in experimental autoimmune encephalomyelitis (EAE) models of multiple sclerosis in mice. Oral R-flurbiprofen prevented and attenuated primary progressive EAE in C57BL6/J mice and relapsing-remitting EAE in SJL mice, even if the treatment was initiated on or after the first flare of the disease. R-flurbiprofen reduced immune cell infiltration and microglia activation and inflammation in the spinal cord, brain and optic nerve and attenuated myelin destruction and EAE-evoked hyperalgesia. R-flurbiprofen treatment increased CD4(+)CD25(+)FoxP3(+) regulatory T cells, CTLA4(+) inhibitory T cells and interleukin-10, whereas the EAE-evoked upregulation of pro-inflammatory genes in the spinal cord was strongly reduced. The effects were associated with an increase of plasma and cortical endocannabinoids but decreased spinal prostaglandins, the latter likely due to R to S inversion. The promising results suggest potential efficacy of R-flurbiprofen in human MS, and its low toxicity may justify a clinical trial.

Effect of interferon beta-1a on B7.1 and B7.2 B-cell expression and its impact on T-cell proliferation

The effect of pharmacologically relevant doses of interferon (IFN) β-1a on B-cell expression of B7.1 and B7.2 was investigated. Culture of peripheral blood mononuclear cells with IFN β-1a 100 IU/mL decreased B-cell expression of B7.1 and increased B7.2 expression. Interleukin-10 in B cells was significantly enhanced by IFN β-1a. Anti-CD3 and anti-CD28 monoclonal antibody-mediated T-cell proliferations were partially suppressed in the presence of B cells pretreated with IFN β-1a. These data suggest that IFN β-1a and B cells can interact to play a beneficial role in the treatment of multiple sclerosis.

Development of experimental autoimmune encephalomyelitis critically depends on CD137 ligand signaling

Multiple sclerosis (MS) is a degenerative autoimmune disease of the CNS. Experimental autoimmune encephalomyelitis (EAE) is a commonly used murine model for MS. Here we report that CD137 ligand (CD137L, 4-1BB ligand, TNFS9), a member of the TNF superfamily, is critical for the development of EAE. EAE symptoms were significantly ameliorated in CD137L(-/-) mice. In the absence of CD137L, myelin oligodendrocyte glycoprotein (MOG)-specific T-cells secreted lower levels of T(h)1/T(h)17 cell-associated cytokines. MOG-specific T-cells also trafficked less efficiently to the CNS in CD137L(-/-) mice, possibly as a consequence of reduced expression of vascular cell adhesion molecule-1 (VCAM-1), which regulates leukocyte extravasation. Thus, CD137L regulates many functions of MOG-specific T-cells that contribute to EAE and may represent a novel therapeutic target for the treatment of MS.

Differential levels of resistance to disease induction and development of relapsing experimental autoimmune encephalomyelitis in two H-2b-restricted mouse strains

Besides the major histocompatibility complex (MHC) genes, background genes are believed to influence the encephalitogenicity of SJL(H-2(s)) and B10.S (H-2(s)) mice responding to myelin basic protein (MBP). A new mouse strain was constructed to study the effects of the SJL genetic background in mice responding to H-2(b)-restricted neuroantigens. Although the SJL.B (H-2(b)) mouse remained resistant to MBP in active EAE induction, the disease severity was uniformly higher in MOG-induced active EAE and in MBP-induced adoptive EAE when compared to those of B6 (H-2(b)) mice. Treatment of mice with anti-CD25 antibodies prior to immunization caused 60% of SJL.B mice to become susceptible to MBP-induced EAE while only 14% of B6 mice were converted. In addition, MOG-induced EAE in SJL.B mice followed a remitting-relapsing disease course while B6 mice only exhibited monophasic or chronic episodes. The new SJL.B mouse strain provides a valuable tool for studying EAE resistance and remitting-relapsing disease in H-2(b) mice.

Enteroglial cells act as antigen-presenting cells in chagasic megacolon

Chagas disease is one of the most serious parasitic diseases of Latin America, with a social and economic impact far outweighing the combined effects of other parasitic diseases such as malaria, leishmaniasis, and schistosomiasis. In the chronic phase of this disease, the destruction of enteric nervous system components leads to megacolon development. Besides neurons, the enteric nervous system is constituted by enteric glial cells, representing an extensive but relatively poorly described population within the gastrointestinal tract. Several lines of evidence suggest that enteric glial cells represent an equivalent of central nervous system astrocytes. Previous data suggest that enteric glia and neurons are active in the enteric nervous system during intestinal inflammatory and immune responses. To evaluate whether these cells act as antigen-presenting cells, we investigated the expression of molecules responsible for activation of T cells, such as HLA-DR complex class II and costimulatory molecules (CD80 and CD86), by neurons and enteric glial cells. Our results indicate that only enteric glial cells of chagasic patients with megacolon express HLA-DR complex class II and costimulatory molecules, and hence they present the attributes necessary to act as antigen-presenting cells.

Models of autoimmune demyelination in the central nervous system: on the way to translational medicine

Multiple sclerosis (MS) is the most common neurologic disease of young adults. In the recent years, our understanding on disease pathomechanisms has considerably improved and new therapies have emerged. Yet a cure for this devastating disorder is still a far cry away and human resources on ex vivo specimens are limited. More than 70 years after its first description, experimental autoimmune encephalomyelitis (EAE) remains an important tool to understand concepts of T cell mediated autoimmunity as well as the roles of the innate and the humoral immune systems. Some EAE models also well reflect mechanisms of tissue damage including demyelination, axonal injury and also cortical changes. A limitation of the classical EAE model is a neglect of CD8 T cell mediated immune mechanisms. Moreover, well characterized models for primary progressive MS or demyelination patterns involving primary oligodendrocyte dystrophy are still not available. Yet many current therapeutic concepts including glatiramer acetate or natalizumab stem from their successful first application in EAE models. New strategies include the widespread use of conditional knockout mice to understand the cell-type specific function of single genes, innovative approaches to establish models on the roles of B cells and CD8 T cells as well as on the relation of inflammation to primary degeneration. In summary, EAE models continue to play an important role in neuroimmunology thereby also stimulating research in other fields of the neurosciences and immunobiology.

Update on inflammation, neurodegeneration, and immunoregulation in multiple sclerosis: therapeutic implications

Multiple sclerosis (MS) is an inflammatory, demyelinating, and neurodegenerative disease of the central nervous system of uncertain etiology. There is consensus that a dysregulated immune system plays a critical role in the pathogenesis of MS; therefore, we aim to summarize current hypotheses concerning the complex cellular and molecular interactions involved in the immunopathology of MS. Although CD4+ T lymphocytes have long been implicated in the immunopathology of MS, the role of other T-cell subtypes has been recognized. CD4+ and CD8+ cells have been isolated from different locations within MS lesions and gamma/delta T cells have been isolated from early MS lesions. The prevalent dogma has been that CD4+ TH1 cells release cytokines and mediators of inflammation that may cause tissue damage, although CD4+ TH2 cells may be involved in modulation of these effects. Recent evidence, however, suggests that additional T-cell subsets play a prominent role in MS immunopathology: TH17 cells, CD8+ effector T cells, and CD4+CD25+ regulatory T cells. In addition, laboratory and clinical data are accumulating on the prominent role of B lymphocytes and antigen-presenting cells in MS pathogenesis. On the basis of these observations, new therapeutic approaches for MS will need to focus on resetting multiple components of the immune system.

High-dose cyclophosphamide in the treatment of multiple sclerosis

High dose cyclophosphamide (HDC) has been successfully used for the treatment of a variety of autoimmune diseases. In this study, we sought to determine whether the use of high dose cyclophosphamide provided stabilization of relapsing remitting MS (RRMS), secondary progressive MS (SPMS), or primary progressive MS (PPMS). The parameters evaluated were EDSS scores, lesion load and brain volumes by MRI and frequency of relapses. Twenty-three patients underwent immunoablative therapy with HDC and were followed for 3.5 years. Nine were relapsing remitting (RRMS), 11 secondary progressive (SPMS), and 3 primary progressive (PPMS). Four of 9 RRMS have had no clinical progression up to 3.5 years following treatment. Three of 9 patients maintained a normal neurologic examination with improved EDSS scores. Seven of the nine RRMS patients had reduction in flare frequency which was maintained for 3.5 years following treatment or no immunomodulating agents. Subgroup analysis in the RRMS patients of lesion load and brain parenchymal volume revealed a favorable trend in these parameters which did not reach statistical significance. The treatment was generally ineffective for SPMS and failed in the 2 PPMS patients. HDC was well tolerated, demonstrated a good safety profile and had minimal adverse effects. These results along with previous reports suggest that early use of HDC therapy in RRMS is promising.

Immunological features of alpha-synuclein in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized pathologically by the presence, in the brain, of intra-cellular protein inclusions highly enriched in aggregated α-synuclein (αSyn), known as Lewy bodies. The onset of PD is accompanied by a local immune reaction in regions of the brain affected by the inclusions, although the mechanism that leads to pathogenesis is far from clear. It is, however, established that disease onset and progression are characterized by sustained activation of microglia, which is linked to significant dopaminergic neuron loss in the substantia nigra. A recent body of evidence indicates that aggregated or modified αSyn can indeed trigger the activation of microglia, inducing a lethal cascade of neuroinflammation and eventually, neuronal loss, pointing at aggregated and modified forms of αSyn as a primary cause of PD pathogenesis. By releasing toxic factors, or by phagocy-tosing neighbouring cells, activated microglia and astrocytes may form a self-perpetuating cycle for neuronal degeneration. Additional findings suggest a link between αSyn and humoural-mediated mechanisms in PD. In this review, we attempt to recapitulate our current understanding of PD physiopathology focused on αSyn and its links with the immune system, as well as of novel and promising therapeutic avenues for the treatment of PD and of other synucleinopathies.

Treatment with type I interferons induces a regulatory T cell subset in peripheral blood mononuclear cells from multiple sclerosis patients

Type I Interferon (IFN-alpha/beta) therapy has altered the natural course of multiple sclerosis. In this paper we evaluate the possible molecular mechanisms involved in the in vitro effects of IFN-alpha/beta on peripheral blood mononuclear cells from patients with clinically definite Relapsing-Remitting Multiple Sclerosis. The total RNA from IFN-alpha, IFN-beta treated cells and untreated cells was extracted and amplified for CD86, CD28, CTLA-4, TNF-alpha, IFN-gamma, CCL2, CCR5, IL-13, MMP-9, TIMP-1, CD25, TGF-beta, IL-10 and the transcriptional factor Foxp3 by Reverse Transcription-Polymerase Chain Reaction and the CD4+CD25high subset was evaluated using flow cytometry. In general, there were no significant differences concerning the modulation of the genes studied in the response to IFN-alpha and IFN-beta treatments, which suggest a similar mechanism of action for both interferons. However, we found a significant increment in IFN-gamma expression after IFN-alpha but not after IFN-beta treatments. The in vitro treatment of mononuclear cells from multiple sclerosis patients with both interferons significantly increased the CD25 mRNA. Furthermore, we observed a CD25/Foxp3 correlation and an increment of the CD4+CD25high subset, indicating that the induction of regulatory T cells could be a crucial mechanism involved in the type I interferon effects.

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

Autoantibodies to alpha-synuclein in inherited Parkinson's disease

Neurodegeneration in Parkinson's disease (PD) is accompanied by a local immune reaction in the affected brain regions. It is well established that alpha-synuclein is directly implicated in the pathogenesis of PD. Development of the disease is often associated with changes of expression and cellular compartmentalisation of this protein; moreover, its oligomers or protofibrils are often released to the CSF and plasma of patients. Aggregated alpha-synuclein can trigger the activation of microglia; however, its capacity to induce production of specific autoantibodies (AAb) has not been assessed. In this study, we examined the presence of AAb against synuclein family members in the peripheral blood serum of PD patients and control individuals. Presence of AAb against beta-synuclein or gamma-synuclein showed no association with PD. Multi-epitopic AAb against alpha-synuclein were detected in 65% of all patients tested and their presence strongly correlated with an inherited mode of the disease but not with other disease-related factors. The frequency of the presence of AAb in the studied group of patients with sporadic form of PD was not significantly different from the frequency in the control group but very high proportion (90%) of patients with familial form of the disease were positive for AAb against alpha-synuclein. We hypothesise that these AAb could be involved in pathogenesis of the inherited form of PD.

Role of CD28 in fatal autoimmune disorder in scurfy mice

Scurfy mice develop CD4 T-cell-mediated lymphoproliferative disease leading to death within 4 weeks of age. The scurfy mutation causes loss of function of the foxp3 gene (foxp3(sf)), which is essential for development and maintenance of naturally occurring regulatory CD4 T cells (nTregs). In humans, mutations of the foxp3 gene cause immune dysregulation, polyendocrinopathy, enteropathy, and X-linked syndrome (IPEX). In most patients with IPEX and also in scurfy mice, T cells show hyperreactivity and levels of Th1- and Th2-associated cytokines are substantially elevated. We report that removal of CD28 expression rescued scurfy mice from early death. Longer-term surviving CD28-deficient scurfy mice still had lymphoproliferative disorder, but their CD4 T cells showed decreased interferon-gamma and no sign of interleukin-4 or interleukin-10 hyperproduction. Furthermore, injection of CTLA4-Ig to block CD28-B7 interactions substantially improved the survival of scurfy mice by blocking effector T-cell differentiation. These data support the hypothesis that CD28-B7 interactions play a critical role in the etiology of lethal autoimmune disease in scurfy mice by stimulating the differentiation of antigen-activated naive T cells into effector T cells.

Increased Soluble 4-1BB Ligand (4-1BBL) Levels in Peripheral Blood of Patients with Multiple Sclerosis

4-1BB ligand (4-1BBL; CD137L) is a member of the tumour necrosis factor superfamily expressed primarily on antigen presenting cells such as B cells, macrophages and dendritic cells. Its engagement with the receptor 4-1BB (CD137) has been shown to promote T-cell activation and regulate proliferation and survival of T cells. The role of the costimulatory molecule in multiple sclerosis (MS) remains unclear. In this study, the expression of 4-1BBL and soluble 4-1BBL (s4-1BBL) protein levels were analysed in peripheral blood of MS patients. Compared with healthy controls, MS patients had an increase in both plasma s4-1BBL protein levels and expression of 4-1BBL in CD14(+) monocytes. In contrast, myelin basic protein-reactive T-cell proliferation was not found to be inhibited by the use of an anti-4-1BBL antibody. The elevated s4-1BBL protein levels in the MS patients may function as a self-regulatory mechanism of 4-1BB/4-1BBL interaction and costimulation.

A PD-1 polymorphism is associated with disease progression in multiple sclerosis

T cells are considered to play a pivotal role in orchestrating the self-reactive immune responses in multiple sclerosis (MS). Programmed death 1 (PD-1) is a member of the B7/CD28 superfamily of costimulatory molecules exerting inhibitory functions on T cells. Recently, an intronic 7146G/A polymorphism within the PD-1 gene was described and suggested to be associated with autoimmunity. We investigated whether this genetic polymorphism is a genetic modifier for risk and progression of MS. Blood samples from 939 German MS patients (mean age, 39 years; range, 13-71; 566 patients [60%] with relapsing-remitting MS, 279 (30%) with secondary, and 94 (10%) with primary progressive MS) and 272 healthy white controls were tested. Genotyping was performed by polymerase chain reaction and restriction enzyme digestion; results were confirmed by automatic sequencing. A significant association of the mutated allele with a progressive disease course was detected (44% 7146G vs 56% 7146A, chi(2) p = 0.002). Consequences of the PD-1 mutation for T-cell function were assessed ex vivo in some patients using microsphere-stimulated peripheral blood lymphocytes and purified CD4 cells. Importantly, PD-1-mediated inhibition of T-cell cytokine secretion (interferon-gamma) is impaired in patients carrying the PD-1 polymorphism. In conclusion, our data suggest that PD-1 polymorphism is a genetic modifier of the progression of MS, possibly through inducing a partial defect in PD-1-mediated inhibition of T-cell activation.

Interferon-beta enhances monocyte and dendritic cell expression of B7-H1 (PD-L1), a strong inhibitor of autologous T-cell activation: relevance for the immune modulatory effect in multiple sclerosis

Antigen-presenting cells (APC) are considered to play a critical role in promoting the (re)activation of potentially autoreactive T cells in multiple sclerosis (MS), an inflammatory demyelinating disorder of the central nervous system (CNS). B7-H1 (PD-L1) is a novel member of the B7 family proteins which exert costimulatory and immune regulatory functions. Here we characterize the expression and functional activity of B7-H1 expressed on monocytes and dendritic cells (DC) of healthy donors and MS patients. B7-H1 is constitutively expressed on monocytes and differentially matured DC, but not on B cells. IFN-beta, the principle immune modulatory agent used for the treatment of MS, strongly enhances B7-H1 expression on monocytes and semi-matured DC, but not B cells, in vitro. Importantly, B7-H1 expressed on APC strongly inhibits autologous CD4 T-cell activation. Neutralization of B7-H1 on monocytes or differentially matured monocyte-derived DC markedly increases the secretion of the pro-inflammatory cytokines, IFN-gamma and IL-2, T-cell proliferation, and the expression of T-cell activation markers. B7-H1 exhibits strong inhibitory effects when expressed on monocytes, immature or semi-mature DC, but less so when expressed on fully matured DC. B7-H1-dependent immune inhibition is in part mediated by CD4/CD25+ regulatory T cells. There is no difference in the baseline expression levels of monocytic B7-H1 between untreated MS patients and healthy donors. However, both groups show a significant concentration-dependent up-regulation of B7-H1 mRNA and protein in response to IFN-beta in vitro. Serial measurements of B7-H1 mRNA in MS patients before and 6 months after initiation of IFN-beta therapy corroborated the relevance of these results in vivo: Nine of nine patients showed a significant increase in B7-H1 mRNA levels after 6 months of IFN-beta therapy (median 1.04 vs. 8.78; p<0.05, two-sided t-test). Accordingly, protein expression of B7-H1 on monocytes was up-regulated after 24 h of IFN-beta application. In summary, B7-H1 expressed on APC acts as a strong inhibitor of autologous CD4 T-cell activation and may thus contribute to the maintenance of peripheral immune tolerance. IFN-beta up-regulates B7-H1 in vitro and in MS patients in vivo and might represent a novel mechanism how IFN-beta acts as a negative modulator on APC T-cell interactions in the periphery.

Beta 2-adrenoceptor involvement in inflammatory demyelination and axonal degeneration in multiple sclerosis

Relapses of multiple sclerosis (MS) are considered to be the clinical expression of acute T-cell-mediated inflammatory demyelinating lesions disseminated in the CNS, whereas disease progression seems to result from widespread axonal degeneration. The pathophysiology of both disease components is incompletely understood. Astrocytes in MS lack beta(2)-adrenoceptors, which via cAMP-mediated processes inhibit the expression of major histocompatibility (MHC) class II molecules and stimulate glycogenolysis in normal conditions. In a pro-inflammatory CNS environment this beta(2)-adrenoceptor defect might allow astrocytes to transform into facultative antigen-presenting cells that can initiate the inflammatory cascade. The same receptor defect might impair astrocytic glycogenolysis, which normally generates lactate that is transported to axons as an energy source. Failure of axonal energy metabolism might result in axonal degeneration through mechanisms that involve intra-axonal accumulation of Ca(2+) ions and mitochondrial dysfunction. If this hypothesis is correct, therapies designed to elevate cAMP levels in astrocytes should reduce or prevent both relapses and progression of MS.

The active metabolite of leflunomide, an immunosuppressive agent, reduces mechanical sensitivity in a rat mononeuropathy model

Recent work has supported a key role for spinal cytokines and glial activation in the development and maintenance of persistent neuropathic pain after peripheral nerve injury. This study was undertaken to determine whether the active metabolite of leflunomide (A77 1726), an anti-inflammatory and immunosuppressive agent, could attenuate persistent mechanical allodynia in a rodent L5 spinal nerve transection model. A77 1726 was administered daily intraperitoneally (0.01 to 10 mg/kg) beginning 1 day before nerve transection. In a separate experiment, A77 1726 was administered daily intrathecally (0.001 to 10 microg in 40 microL) beginning 1 hour before nerve transection. Both systemic and centrally administered A77 1726 significantly reduced mechanical allodynia across the time course of the study (P < .05). A77 1726 attenuated glial activation on day 10 after transection at doses that reduced mechanical sensitivity. In addition, central A77 1726 administration decreased spinal expression of major histocompatibility complex class II. Spinal interleukin-6 levels were unaffected by A77 1726 treatment. This study provides further evidence implicating a contribution of spinal glial activation in the development and maintenance of persistent neuropathic pain. Furthermore, this study reports that systemic and central administration of the active metabolite of leflunomide, an immunosuppressive agent used for the treatment of rheumatoid arthritis, produces an antiallodynic action in a rodent mononeuropathy model.

Break of neonatal Th1 tolerance and exacerbation of experimental allergic encephalomyelitis by interference with B7 costimulation

Ig-PLP1 is an Ig chimera expressing proteolipid protein-1 (PLP1) peptide corresponding to aa residues 139-151 of PLP. Newborn mice given Ig-PLP1 in saline on the day of birth and challenged 7 wk later with PLP1 peptide in CFA develop an organ-specific neonatal immunity that confers resistance against experimental allergic encephalomyelitis. The T cell responses in these animals comprise Th2 cells in the lymph node and anergic Th1 lymphocytes in the spleen. Intriguingly, the anergic splenic T cells, although nonproliferative and unable to produce IFN-gamma or IL-4, secrete significant amounts of IL-2. In this work, studies were performed to determine whether costimulation through B7 molecules plays any role in the unusual form of splenic Th1 anergy. The results show that engagement of either B7.1 or B7.2 with anti-B7 Abs during induction of EAE in adult mice that were neonatally tolerized with Ig-PLP1 restores and exacerbates disease severity. At the cellular level, the anergic splenic T cells regain the ability to proliferate and produce IFN-gamma when stimulated with Ag in the presence of either anti-B7.1 or anti-B7.2 Ab. However, such restoration was abolished when both B7.1 and B7.2 molecules were engaged simultaneously, indicating that costimulation is necessary for reactivation. Surprisingly, both anti-B7.1 and anti-B7.2 Abs triggered splenic dendritic cells to produce IL-12, a key cytokine required for restoration of the anergic T cells. Thus, recovery from neonatally induced T cell anergy requires B7 molecules to serve double functions, namely, costimulation and induction of cytokine production by APCs.

Disease-modifying therapies in multiple sclerosis: an update on recent and ongoing trials and future strategies

Multiple sclerosis (MS) is the prototype inflammatory autoimmune disorder of the central nervous system and the most common cause of neurological disability in young adults exhibiting considerable clinical, radiological and pathological heterogeneity. Novel insights in the immunopathological processes, advances in biotechnology, development of powerful magnetic resonance imaging technologies together with improvements in clinical trial design led to a variety of evaluable therapeutic approaches. Therapy has changed dramatically over the past decade, yielding significant progress for the treatment of relapsing-remitting and secondary progressive MS. A substantial number of pivotal and preliminary reports continue to demonstrate encouraging new evidence that advances are being made in the care of MS patients. This review summarises recent progress with currently available disease-modifying therapies and - on the basis of present immunopathogenetic concepts - outlines ongoing studies as well as future treatment strategies.

IL-1 receptor-associated kinase 1 regulates susceptibility to organ-specific autoimmunity

Infections often precede the development of autoimmunity. Correlation between infection with a specific pathogen and a particular autoimmune disease ranges from moderately strong to quite weak. This lack of correspondence suggests that autoimmunity may result from microbial activation of a generic, as opposed to pathogen-specific host-defense response. The Toll-like receptors, essential to host recognition of microbial invasion, signal through a common, highly conserved pathway, activate innate immunity, and control adaptive immune responses. To determine the influence of Toll/IL-1 signaling on the development of autoimmunity, the responses of wild-type (WT) mice and IL-1R-associated kinase 1 (IRAK1)-deficient mice to induction of experimental autoimmune encephalomyelitis were compared. C57BL/6 and B6.IRAK1-deficient mice were immunized with MOG 35-55/CFA or MOG 35-55/CpG DNA/IFA. WT animals developed severe disease, whereas IRAK1-deficient mice were resistant to experimental autoimmune encephalomyelitis, exhibiting little or no CNS inflammation. IRAK1-deficient T cells also displayed impaired Th1 development, particularly during disease induction, despite normal TCR signaling. These results suggest that IRAK1 and the Toll/IL-1 pathway play an essential role in T cell priming, and demonstrate one means through which innate immunity can control subsequent development of autoimmunity. These findings may also help explain the association between antecedent infection and the development or exacerbations of some autoimmune diseases.

Reactive astrocytes in chronic active lesions of multiple sclerosis express co-stimulatory molecules B7-1 and B7-2

Astrocytes in active lesions of multiple sclerosis (MS) express major histocompatibility (MHC) class II molecules, and may play an important role in the presentation of antigen to myelin-specific T cells.However, it has been postulated that astrocytes are unable to act as antigen-presenting cells (APCs) because they would lack the B7 co-stimulatory molecules to activate these T cells. By using double labeling immunofluorescence staining, we demonstrate that reactive astrocytes in chronic active plaques of multiple sclerosis express the co-stimulatory molecules B7-1 and B7-2, and hence have the necessary attributes to act as antigen-presenting cells.

Differential expression of MHC class II and B7 costimulatory molecules by microglia in rodent gliomas

To assess the immune function of microglia and macrophages in brain tumors, the expression of MHC class II and B7 costimulatory molecules in three rodent glioma models was examined. Microglia and macrophages, which accounted for 5-12% of total cells, expressed B7.1 and MHC class II molecules in the C6 and 9L tumors, but not RG2 gliomas. Interestingly, the expression of B7.1 and MHC class II molecules by microglia and macrophage was associated with an increase in the number of tumor-infiltrating lymphocytes in C6 and 9L tumors. B7.2 expression, which was present at low levels on microglia and macrophages in normal brain, did not significantly change in tumors. Interestingly, the expression of all three surface antigens increased after microglia were isolated from intracranial C6 tumors and cultured for a short period of time. We conclude that microglia immune activity may be suppressed in gliomas and directly correlates to the immunogenecity of experimental brain tumors.

Immunological indicators of disease activity and prognosis in multiple sclerosis

The need to ensure an accurate diagnosis and proper treatment for multiple sclerosis patients, considering the various clinical and immunopathological subtypes of the disease, requires the identification of biomarkers that measure disease activity and predict the course of disease development in individual patients. Moreover, the identification of effective indicators will lead not only to optimized patient treatment but also to the development of better tools for evaluating clinical trials. Recent studies focusing on the identification of possible immunological markers in multiple sclerosis will be reviewed.

Peroxisome proliferator-activated receptor-gamma agonist 15-deoxy-Delta(12,14)-prostaglandin J(2) ameliorates experimental autoimmune encephalomyelitis

Peroxisome proliferator-activated receptors (PPAR) are members of a nuclear hormone receptor superfamily that includes receptors for steroids, retinoids, and thyroid hormone, all of which are known to affect the immune response. Previous studies dealing with PPAR-gamma expression in the immune system have been limited. Recently, PPAR-gamma was identified in monocyte/macrophage cells. In this study we examined the role of PPAR-gamma in experimental autoimmune encephalomyelitis (EAE), an animal model for the human disease multiple sclerosis. The hypothesis we are testing is whether PPAR-gamma plays an important role in EAE pathogenesis and whether PPAR-gamma ligands can inhibit the clinical expression of EAE. Initial studies have shown that the presence of the PPAR-gamma ligand 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ2) inhibits the proliferation of Ag-specific T cells from the spleen of myelin basic protein Ac(1-11) TCR-transgenic mice. 15d-PGJ2 suppressed IFN-gamma, IL-10, and IL-4 production by both Con A- and myelin basic protein Ac(1-11) peptide-stimulated lymphocytes as determined by ELISA and ELISPOT assay. Culture of encephalitogenic T cells with 15d-PGJ2 in the presence of Ag reduced the ability of these cells to adoptively transfer EAE. Examination of the target organ, the CNS, during the course of EAE revealed expression of PPAR-gamma in the spinal cord inflammatory infiltrate. Administration of 15d-PGJ2 before and at the onset of clinical signs of EAE significantly reduced the severity of disease. These results suggest that PPAR-gamma ligands may be a novel therapeutic agent for diseases such as multiple sclerosis.

Costimulation of memory T-cells by ICOS: a potential therapeutic target for autoimmunity?

Approaches that target costimulatory receptors are independent of T-cell receptor specificity and may be useful for T-cell-mediated diseases in which the antigens involved are not well defined. However, the proper costimulatory pathways need to be targeted. For example, therapies for human T-cell-mediated diseases need to be effective against previously activated memory cells. In this review, we use autoimmune demyelination as a paradigm for established immune-mediated pathogenesis. Studies with the human disease multiple sclerosis and the rodent model experimental autoimmune encephalomyelitis have suggested that the effectiveness of CD28 blockade, as a therapeutic strategy for established autoimmune demyelination, may be limited. ICOS, a receptor that appears to be involved in the costimulation of previously activated T-cells, may be an attractive alternative.

Complexities of CD28/B7: CTLA-4 costimulatory pathways in autoimmunity and transplantation

Recent advances in the understanding of T cell activation have led to new therapeutic approaches in the treatment of immunological disorders. One attractive target of intervention has been the blockade of T cell costimulatory pathways, which result in more selective effects on only those T cells that have encountered specific antigen. In fact, in some instances, costimulatory pathway antagonists can induce antigen-specific tolerance that prevents the progression of autoimmune diseases and organ graft rejection. In this review, we summarize the current understanding of these complex costimulatory pathways including the individual roles of the CD28, CTLA-4, B7-1 (CD80), and B7-2 (CD86) molecules. We present evidence that suggests that multiple mechanisms contribute to CD28/B7-mediated T cell costimulation in disease settings that include expansion of activated pathogenic T cells, differentiation of Th1/Th2 cells, and the migration of T cells into target tissues. Additionally, the negative regulatory role of CTLA-4 in autoimmune diseases and graft rejection supports a dynamic but complex process of immune regulation that is prominent in the control of self-reactivity. This is most apparent in regulation of the CD4(+)CD25(+)CTLA-4(+) immunoregulatory T cells that control multiple autoimmune diseases. The implications of these complexities and the potential for use of these therapies in clinical immune intervention are discussed.