Relapsing Experimental Allergic Encephalomyelitis Research Articles

Targeting fibroblast growth factor-inducible-14 signaling protects from chronic relapsing experimental autoimmune encephalomyelitis

The TNF-related weak inducer of apoptosis (TWEAK) is a TNF family member mediating proinflammatory effects by its receptor fibroblast growth factor-inducible-14 (Fn14). We studied the role of TWEAK/Fn14 in experimental autoimmune encephalomyelitis (EAE) by protein vaccination with TWEAK and Fn14 and recombinant TWEAK-DNA, respectively. TWEAK-DNA vaccination worsened the clinical course of EAE and increased central nervous system (CNS) inflammation. TWEAK increased the secretion of CCL2 [monocyte chemotactic protein-1 (MCP-1)] by CNS endothelial cells and astrocytes in vitro, suggesting CCL2 as a critical mediator of TWEAKs proinflammatory effects. Vaccination with the extracellular domain of TWEAK or with Fn14 resulted in the induction of specific inhibitory antibodies and an amelioration of EAE signs in two different models in rats and mice. Spinal cord inflammatory infiltrates were significantly diminished. Purified IgG from TWEAK- or Fn14-vaccinated rats prevented TWEAK-induced production of CCL2 by endothelial cells. Blocking Fn14 signaling represents a novel approach with potential for the treatment of CNS autoimmunity.

Predictability of FTY720 efficacy in experimental autoimmune encephalomyelitis by in vivo macrophage tracking: clinical implications for ultrasmall superparamagnetic iron oxide-enhanced magnetic resonance imaging.

To examine the efficacy of FTY720 as a new agent to reduce inflammatory activity in an animal model of multiple sclerosis (MS) by in vivo macrophage tracking. FTY720 was used for treatment of rats in a model of chronic relapsing experimental autoimmune encephalomyelitis (EAE) at an oral dose of 0.3 mg/kg/day. Magnetic resonance imaging (MRI) based on in vivo tracking of macrophages labeled with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, immunohistological staining (IHC), and neurological readouts was used to study the burden of disease in treated and untreated animals. While untreated animals showed severe paralysis of the hind paws, intense accumulation of macrophages in brain tissue, and areas of blood-brain barrier (BBB) disruption, FTY720-treated animals displayed no signs of inflammatory activity or neurological impairment. These observations were made for both acute phase and first relapse. Tracking of macrophages by MRI provides direct evidence of the immunomodulatory efficacy of FTY720 in the EAE model and correlates well with neurological symptoms and histology.

Axonal protection using flecainide in experimental autoimmune encephalomyelitis

Axonal degeneration is a major cause of permanent neurological deficit in multiple sclerosis (MS), but no current therapies for the disease are known to be effective at axonal protection. Here, we examine the ability of a sodium channel-blocking agent, flecainide, to reduce axonal degeneration in an experimental model of MS, chronic relapsing experimental autoimmune encephalomyelitis (CR-EAE). Rats with CR-EAE were treated with flecainide or vehicle from either 3 days before or 7 days after inoculation (dpi) until termination of the experiment at 28 to 30 dpi. Morphometric examination of neurofilament-labeled axons in the spinal cord of CR-EAE animals showed that both flecainide treatment regimens resulted in significantly higher numbers of axons surviving the disease (83 and 98% of normal) compared with controls (62% of normal). These findings indicate that flecainide and similar agents may provide a novel therapy aimed at axonal protection in MS and other neuroinflammatory disorders.

Intracerebral expression of CXCL13 and BAFF is accompanied by formation of lymphoid follicle-like structures in the meninges of mice with relapsing experimental autoimmune encephalomyelitis

Given the abnormalities in B-cell activity occurring in the central nervous system (CNS) of patients with multiple sclerosis (MS), we have explored the possibility that CNS inflammation induced in mouse models of experimental autoimmune encephalomyelitis (EAE) triggers expression of molecules that control the development and functional organization of lymphoid follicles, the sites where B-cell responses are initiated. By reverse transcription–polymerase chain reaction (RT-PCR), we find that gene expression of CXCL13, a chemokine involved in B-cell recruitment into lymphoid follicles, and BAFF, a key regulator of B-cell survival, is markedly and persistently upregulated in the CNS of mice with relapsing-remitting and chronic-relapsing EAE. Using immunohistochemical techniques, we also show the presence of lymphoid follicle-like structures containing B cells and a reticulum of CXCL13 + and FDC-M1 + follicular dendritic cells within the meninges of several mice undergoing progressive relapsing EAE. These observations indicate that, under chronic inflammatory conditions, the less immunoprivileged meningeal compartment is the site where ectopic lymphoid follicles preferentially develop and where pathogenic B-cell responses could be sustained in autoimmune disorders of the CNS.

Differential effects of treatment with a small-molecule VLA-4 antagonist before and after onset of relapsing EAE

AbstractInteraction of very late antigen-4 (VLA-4) with its ligand vascular cell adhesion molecule-1 (VCAM-1) is required for central nervous system (CNS) migration of encephalitogenic T cells in relapsing experimental autoimmune encephalomyelitis (R-EAE). Anti-VLA-4 monoclonal antibody (mAb) treatment prior to EAE onset inhibits disease induction; however, treatment initiated after the appearance of clinical symptoms increases relapse rates, augments Th1 responses, and enhances epitope spreading perhaps due to the activation of costimulatory signals. To negate the potential costimulatory activity of intact anti-VLA-4, we examined the ability of BIO 5192, a small-molecule VLA-4 antagonist, to regulate active proteolipid protein 139-151 (PLP139-151)-induced R-EAE. BIO 5192 administered one week after peptide priming (ie, before clinical disease onset) delayed the clinical disease onset but led to severe disease exacerbation upon treatment removal. BIO 5192 treatment initiated during disease remission moderately enhanced clinical disease while mice were on treatment and also resulted in posttreatment exacerbation. Interestingly, BIO 5192 treatment begun at the peak of acute disease accelerated entrance into disease remission and inhibited relapses, but treatment removal again exacerbated disease. Enhanced disease was caused by the release of encephalitogenic cells from the periphery and the rapid accumulation of T cells in the CNS. Collectively, these results further demonstrate the complexity of VLA-4/VCAM interactions, particularly in a relapsing-remitting autoimmune disease. (Blood. 2003;102:4464-4471)

Efficient technique for immortalization of murine microglial cells relevant for studies in murine models of multiple sclerosis

Microglia are macrophage-like cells that populate the central nervous system (CNS) and become activated upon injury or infection. Microglia have been implicated as playing critical roles in various CNS diseases including multiple sclerosis (MS), a human autoimmune demyelinating disease, as well as in other neurodegenerative diseases. Two well-characterized models of MS, relapsing experimental autoimmune encephalomyelitis (R-EAE) and Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease, are inducible in SJL mice and model the relapsing–remitting and chronic-progressive forms of MS, respectively. These models are useful for the study of the mechanisms of initiation, progression, and therapy of the disease. Currently, a major limitation to studying the functions of microglia in these murine models of MS is the restricted number of cells capable of being isolated from the CNS of neonatal mice and propagated in culture. The current studies describe the preparation of SV-40 large T antigen-immortalized mouse microglia lines, M4T.4 and M4T.6, from the SJL/J mice. The immortalization technique was very efficient requiring only 6 weeks to develop long-term, highly replicating cell lines. The resulting microglia cell lines remain quiescent, but are induced to express various immune cytokines and to function as efficient antigen presenting cells upon activation with IFN-γ or infection with TMEV. Thus, the SV-40 large T antigen immortalized microglia lines react to innate and infectious stimuli similar to primary microglia isolated from neonatal mice, but are more easily maintained in culture. This technique should allow for the efficient cultivation of large numbers of microglial cells from a variety of disease-relevant mouse strains, including knock-out and transgenic mice.

MRI-based monitoring of inflammation and tissue damage in acute and chronic relapsing EAE.

Experimental autoimmune encephalomyelitis (EAE) is a commonly used animal model that in several respects mimics human multiple sclerosis (MS), and can be used to design or validate new strategies for treatment of this disease. In the present study, different MRI techniques (macrophage tracking based on labeling cells in vivo by ultrasmall particles of iron oxide (USPIO), blood-brain barrier (BBB) breakdown, and magnetization transfer imaging (MTI)), as well as immunohistological staining were used to study the burden of disease in Lewis rats immunized by guinea pig myelin. The resulting imaging data was compared with behavioral readouts. Animals were studied during the acute phase and the first relapse. Activated monocytes were detected during both episodes in the brain stem or cortex. These areas coincided in part with areas of BBB breakdown. Significant changes of the magnetization transfer ratios (MTRs) of up to 35% were observed in areas of USPIO accumulation. This suggests that infiltrating monocytes are the major source of demyelination in EAE, but monocyte infiltration and breakdown of the BBB are temporally or spatially independent inflammatory processes.

Chemokine upregulation follows cytokine expression in chronic relapsing experimental autoimmune encephalomyelitis.

Chronic relapsing experimental autoimmune encephalomyelitis (ChREAE) is an autoimmune disease of the central nervous system (CNS) induced by CNS myelin components. In the early active stage, both ChREAE and multiple sclerosis (MS) are characterized by the presence of perivascular inflammatory cuffs disseminated in the CNS. There is growing evidence that chemoattractant cytokines (chemokines) play an important role in this process. The main goal of the present study was to analyse the hypothesis that chemokine expression in the CNS during autoimmune inflammation is regulated by proinflammatory cytokines. To address this concept, we analysed temporal relations between chemokine and cytokine expression during ChREAE. Phasic upregulation of gene expression for chemokines T-cell activation gene 3 (TCA-3)/CCL1, monocyte chemoattractant protein-1 (MCP-1)/CCL2, macrophage inflammatory protein-1 alpha (MIP-1alpha)/CCL3, MIP-1beta/CCL4, regulated on activation normal T cell expressed and secreted (RANTES)/CCL5 and MIP-2/CXCL2-3 as well as cytokines tumour necrosis factor-alpha (TNF-alpha), -beta, LT-beta, interferon-gamma (IFN-gamma) and transforming growth factor-beta1 (TGF-beta1) in the CNS was observed during attacks of ChREAE. Expression of cytokines TNF-beta and LT-beta preceded, and the expression of TGF-beta1 followed chemokine upregulation. Our results suggest that chemokine expression during CNS autoimmune inflammation may be regulated by some proinflammatory cytokines.

Dendritic and Synaptic Pathology in Experimental Autoimmune Encephalomyelitis

Evidence has shown that excitotoxicity may contribute to the loss of central nervous system axons and oligodendrocytes in multiple sclerosis and experimental autoimmune encephalomyelitis (EAE). Because dendrites and synapses are vulnerable to excitotoxicity, we examined these structures in acute and chronic models of EAE. Immunostaining for microtubule-associated protein-2 showed that extensive dendritic beading occurred in the white matter of the lumbosacral spinal cord (LSSC) during acute EAE episodes and EAE relapses. Retrograde labeling confirmed that most motoneuron dendrites were beaded in the white matter of the LSSC in acute EAE. In contrast, only mild swelling was observed in the gray matter of the LSSC. Dendritic beading showed marked recovery during EAE remission and after EAE recovery. In addition, synaptophysin, synapsin I, and PSD-95 immunoreactivities were significantly reduced in both the gray and white matter of the LSSC during acute EAE episodes and EAE relapses, but showed partial recovery during EAE remission and after EAE recovery. Pathologically, both dendritic beading and the reduction in synaptic protein immunoreactivity were well correlated with inflammatory cell infiltration in the LSSC at different EAE stages. We propose that dendritic and synaptic damage in the spinal cord may contribute to the neurological deficits in EAE.

Regional and temporal expression patterns of interleukin-10, interleukin-10 receptor and adhesion molecules in the rat spinal cord during chronic relapsing EAE

Adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) mediate leukocyte infiltration into the CNS, in experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS). Because exogenous interleukin-10 (IL-10) inhibits ICAM-1 and VCAM-1 expression and clinical EAE, we hypothesize that endogenous IL-10 signaling may suppress expression of adhesion molecules. In a rat model of chronic relapsing EAE, expression levels of IL-10 and its receptor (IL-10R1), ICAM-1 and VCAM-1 mRNA in the spinal cord are markedly increased, whereas levels of IL-10 mRNA remain relatively low. The temporal pattern of mRNA and protein expression showed marked differences between spinal cord levels. During relapse, IL-10, IL-10R1, ICAM-1, VCAM-1 mRNA levels and neurological scores show positive correlations. We conclude that endogenous IL-10 is not a crucial factor inhibiting adhesion molecule expression in this model.

Epitope spreading is not required for relapses in experimental autoimmune encephalomyelitis.

The sequential emergence of specific T lymphocyte-mediated immune reactivity directed against multiple distinct myelin epitopes (epitope spreading) has been associated with clinical relapses in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Based on this association, an appealing and plausible model for immune-mediated progression of the advancing clinical course in MS and EAE has been proposed in which epitope spreading is the cause of clinical relapses in T cell-mediated CNS inflammatory diseases. However, the observed association between epitope spreading and disease progression is not universal, and absolute requirements for epitope spreading in progressive EAE have not been tested in the absence of multiple T cell specificities, because most prior studies have been conducted in immunocompetent mouse strains that possessed broad TCR repertoires. Consequently, the precise nature of a causal relationship between epitope spreading and disease progression remains uncertain. To determine whether relapsing or progressive EAE can occur in the absence of epitope spreading, we evaluated the course of disease in mice which possessed only a single myelin-specific TCR. These mice (transgenic/SCID +/+) exhibited a progressive and sometimes remitting/relapsing disease course in the absence of immune reactivity to multiple, spreading myelin epitopes. The results provide direct experimental evidence relevant to discussions on the mechanisms of disease progression in MS and EAE.

The new orally active immunoregulator laquinimod (ABR-215062) effectively inhibits development and relapses of experimental autoimmune encephalomyelitis

A new orally active drug, laquinimod (ABR-215062), was shown to completely inhibit the development of murine acute experimental autoimmune encephalomyelitis (EAE). Furthermore, leukocyte infiltration into the central nervous system (CNS) was abolished in the laquinimod-treated animals. By direct comparison based on dose and total exposure, laquinimod was approximately 20 times more potent than the immunomodulator roquinimex. Laquinimod also had clear therapeutic effect when given after clinical onset in a chronic relapsing EAE model. It therefore represents a new orally active immunoregulatory drug without general immunosuppressive properties for the treatment of the autoimmune disease multiple sclerosis.

Transient anti-CD154-mediated immunotherapy of ongoing relapsing experimental autoimmune encephalomyelitis induces long-term inhibition of disease relapses

Relapsing experimental autoimmune encephalomyelitis (R-EAE) is a Th1-mediated central nervous system (CNS) autoimmune disease with pathology similar to that of relapsing–remitting multiple sclerosis. Among recent therapeutic approaches to prevent or treat relapsing disease is the strategic blockade of the CD154–CD40 ligand pair interactions. We have previously shown that CD154 blockade at the peak of acute disease can, in the short term, inhibit spontaneous disease relapse and this is at least partly associated with the inhibition of T cell effector function and blockade of inflammatory cell recruitment to and/or retention in the CNS. However, little is understood about the long-term effects of CD154 blockade in the inhibition of immune responses to encephalitogenic antigens. Here we demonstrate that transient anti-CD154 blockade of CD154–CD40 interactions at the peak of acute phase of R-EAE resulted in significant long-term inhibition (by >80%) of clinical relapses and that clinical disease in those mice that did relapse was reduced in duration and severity compared to control antibody-treated mice. Additionally, we show that this strategy permanently inhibits DTH responses of T cells specific for relapse-associated encephalitogenic epitopes. Thus, transient CD154 blockade during ongoing disease has a long-term therapeutic efficacy in preventing disease relapses.

Upregulation of monocyte chemotactic protein-1 and CC chemokine receptor 2 in the central nervous system is closely associated with relapse of autoimmune encephalomyelitis in Lewis rats

Experimental autoimmune encephalomyelitis (EAE) is a disease model of multiple sclerosis (MS) that is characterized by remittance and relapse of the disease and autoimmune and demyelinating lesions in the central nervous system (CNS). To better understand the mechanism of disease relapse, we induced acute and chronic relapsing (CR)-EAE in Lewis rats and examined the differences between the two groups. An immunohistochemical study revealed that significantly higher numbers of macrophages infiltrated the spinal cord during the first and second attacks of CR-EAE than at the peak of acute EAE, whereas the number of infiltrating T cells was essentially the same in acute and CR-EAE. In accordance with this finding, monocyte chemoattractant protein-1 (MCP-1) mRNA, but not MIP-1α and RANTES mRNA, increased significantly in CR-EAE lesions rather than in acute EAE lesions. More importantly, the level of MCP-1 during the remission of CR-EAE was significantly higher than during the recovery phase of acute EAE, suggesting that this high level of MCP-1 in CR-EAE is associated with relapse of the disease. CC chemokine receptor 2 (CCR2), the main receptor for MCP-1, was expressed on astrocytes, macrophages and T cells and the number of positive cells was higher in CR-EAE than in acute EAE. Collectively, these findings suggest that high expression of MCP-1 and its receptor, CCR2, in the CNS play important roles in relapse of EAE.

Identification of autoimmune encephalomyelitis-associated common CDR3 sequences by CDR3 spectratyping and subsequent DNA hybridization

In previous studies, we demonstrated that T cell receptor (TCR) Vβ8.2 and Vβ10, both of which are frequently used by encephalitogenic T cells, spectratypes expand oligoclonally in spinal cord lesions of Lewis rats with experimental autoimmune encephalomyelitis (EAE) and that the DSSYEQYF and WDGSGNVLYF sequences are predominantly found in the complementarity-determining region 3 (CDR3) of spectratype-derived TCR clones. However, it is unknown whether these CDR3 sequences are used only by Vβ8.2- and Vβ10-positive T cells or by encephalitogenic T cells bearing Vβs other than these Vβs. The present study was undertaken to address this issue using a new approach, i.e. CDR3 spectratyping and subsequent DNA hybridization with several probes corresponding to various parts of the CDR3 region. Consequently, we found that probes specific for the Vβ8.2 spectratype-derived Dβ and Jβ2.7 hybridized only with the Vβ8.2 spectratype in acute EAE and with the Vβ8.2 and Vβ12 spectratypes in chronic relapsing EAE. Similarly, a probe specific for the Vβ10 spectratype-derived Dβ hybridized only with the Vβ10 spectratype in both acute and chronic relapsing EAE. In contrast, a probe specific for Jβ1.3 hybridized with several Vβ spectratypes including Vβ8.2 and Vβ10 only during the early stage of the disease. These findings suggest that T cells bearing a few Vβs with a limited number of the CDR3 sequences are activated in acute and chronic relapsing EAE induced in Lewis rats. Characterization of the CDR3 region of pathogenic TCR by this approach may be of value for the screening of autoimmune disease-associated TCR and for the development of TCR-based specific immunotherapy.

Pathological and regulatory effects of anti-myelin antibodies in experimental allergic encephalomyelitis in mice

Neurological deficit in experimental allergic encephalomyelitis (EAE) and multiple sclerosis (MS) is probably a consequence of synergy between T and B cell responses to CNS antigens. During the demyelinating phase of chronic relapsing EAE in ABH mice, anti-myelin oligodendrocyte glycoprotein (MOG) responses were increased compared to the inflammatory acute phase, but such levels did not correlate with the severity of clinical disease. The pathogenicity of antibodies (Ab) to MOG, myelin basic protein (MBP), proteolipid protein (PLP) and galactocerebroside (GalC) was investigated in vivo following injection at the onset of EAE. An IgG2a monoclonal Ab (mAb), clone Z12, directed to MOG augmented clinical disease and demyelination in ABH and C57BL/6 mice, but not MOG knock-out mice. No effect was observed with F(ab 2)′ fragments of Z12 or with the anti-MOG IgG1 mAbs, clones Y10 or 8–18C5. Cobra venom factor partially reduced the augmenting effect of mAb Z12 suggesting a role for complement. The pathogenic effect of anti-myelin Abs was not restricted to MOG since an anti-GalC mAb exacerbated inflammation in the CNS while an MBP mAb (clone 22) reduced clinical disease. Taken together, these data provide further evidence that myelin-reactive Abs generated during autoimmune neurological disease may play an important role not only in the pathogenesis of disease but also the regulation of myelin-targeted autoimmune disease.

Administration of agonistic anti-4-1BB monoclonal antibody leads to the amelioration of experimental autoimmune encephalomyelitis.

4-1BB, a member of the TNFR superfamily, is a costimulatory receptor primarily expressed on activated T cells. It has been shown that the administration of agonistic anti-4-1BB Abs enhances tumor immunity and allogenic immune responses. Paradoxically, we found that the administration of an agonistic anti-4-1BB mAb (2A) dramatically reduced the incidence and severity of experimental autoimmune encephalomyelitis (EAE). Adoptive transfer of T cells from such treated mice failed to induce EAE, whereas anti-4-1BB treatment following adoptive transfer of encephalitogenic T cells did not prevent EAE pathogenesis. These results suggest that anti-4-1BB treatment during the induction phase inhibits autoreactive T cell immune responses rather than preventing T cell trafficking into the CNS. This was substantiated by the observations that draining lymph node cells from anti-4-1BB-treated mice failed to respond to Ag stimulation in vitro. In addition, we found that such treatment initially promotes the activation and proliferation of Ag-specific CD4+ T cells but subsequently increases their probability of undergoing activation-induced cell death, thereby inhibiting effector T cell responses. More importantly, 2A treatment also inhibits the relapse of EAE in a clinically relevant murine model of multiple sclerosis. This study indicates that the agonistic Ab against 4-1BB can potentially be used as a novel immunotherapeutic agent for treating autoimmune diseases.

Normal Th1 development following long-term therapeutic blockade of CD154-CD40 in experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is a Th1-mediated demyelinating disease of the CNS with similarities to multiple sclerosis. We and others have shown that a short-term course of anti-CD154 mAb treatment to block CD154-CD40 interactions can be used to prevent or even treat ongoing PLP139-151-induced relapsing EAE. However, little is known of the long-term effects of CD154 blockade on the development of antigen-specific T cell function. Here, we show that short-term treatment with anti-CD154 at the time of PLP139-151/CFA immunization inhibits clinical disease for up to 100 days after immunization. At this point, comparable numbers of Th1 cells are observed in anti-CD154 and control Ig-treated mice, as assessed by antigen-specific ELISPOT assays. Thus, the long-term Th1/Th2 balance is largely unaffected. Inflammatory responses are diminished in anti-CD154-treated mice, as indicated by reduced in vivo delayed-type hypersensitivity and reduced levels of splenic IFN-gamma secretion in vitro. However, upon adoptive transfer of T cells isolated from the spleens of anti-CD154-treated mice, these cells contributed as effectively to clinical disease as those obtained from control-treated mice. Thus, anti-CD154 therapy leads to long-term therapeutic efficacy without exerting a long-term influence on Th1 development.

Normal Th1 development following long-term therapeutic blockade of CD154-CD40 in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a Th1-mediated demyelinating disease of the CNS with similarities to multiple sclerosis. We and others have shown that a short-term course of anti-CD154 mAb treatment to block CD154-CD40 interactions can be used to prevent or even treat ongoing PLP139-151–induced relapsing EAE. However, little is known of the long-term effects of CD154 blockade on the development of antigen-specific T cell function. Here, we show that short-term treatment with anti-CD154 at the time of PLP139-151/CFA immunization inhibits clinical disease for up to 100 days after immunization. At this point, comparable numbers of Th1 cells are observed in anti-CD154 and control Ig–treated mice, as assessed by antigen-specific ELISPOT assays. Thus, the long-term Th1/Th2 balance is largely unaffected. Inflammatory responses are diminished in anti-CD154–treated mice, as indicated by reduced in vivo delayed-type hypersensitivity and reduced levels of splenic IFN-γ secretion in vitro. However, upon adoptive transfer of T cells isolated from the spleens of anti-CD154–treated mice, these cells contributed as effectively to clinical disease as those obtained from control-treated mice. Thus, anti-CD154 therapy leads to long-term therapeutic efficacy without exerting a long-term influence on Th1 development.

Complexities of applying nasal tolerance induction as a therapy for ongoing relapsing experimental autoimmune encephalomyelitis (EAE) in DA rats.

EAE is an autoimmune disease of the central nervous system (CNS) that serves as an experimental model for the human inflammatory demyelinating disease multiple sclerosis (MS). Antigen-based immunotherapy including soluble antigen administration via feeding has been shown to be successful in treating EAE in rodents. In the present study, we explore nasal administration of small amounts of myelin basic protein (MBP) as a potential means of treatment of protracted, relapsing EAE (PR-EAE) in a novel DA rat system. We found that nasal administration of MBP prevented EAE induced with whole spinal cord homogenate + Freund's incomplete adjuvant (FIA), and strongly down-regulated levels of MBP-reactive interferon-gamma (IFN-gamma)-secreting Th1-like cells. However, in rats with ongoing PR-EAE receiving the same regimen of MBP, a trend of aggravated disease was recorded, in conjunction with augmented levels of MBP-reactive IFN-gamma-secreting Th1-like splenocytes during the acute phase of EAE. These data have implications for the clinical application of nasal tolerance to autoimmune diseases.