Minireview: autoimmune responses to myelin proteolipid protein

Sex, aging and immunity in multiple sclerosis and experimental autoimmune encephalomyelitis: An intriguing interaction

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) with a profound neurodegenerative component early in the disease pathogenesis. Age is a factor with a well-described effect on the primary disease phenotype, namely, the relapsing-remitting vs. the primary progressive disease. Moreover, aging is a prominent factor contributing to the transition from relapsing-remitting MS (RRMS) to secondary progressive disease. However, sex also seems to, at least in part, dictate disease phenotype and evolution, as evidenced in humans and in animal models of the disease. Sex-specific gene expression profiles have recently elucidated an association with differential immunological signatures in the context of experimental disease. This review aims to summarize current knowledge stemming from experimental autoimmune encephalomyelitis (EAE) models regarding the effects of sex, either independently or as a factor combined with aging, on disease phenotype, with relevance to the immune system and the CNS.

Therapeutic intervention in relapsing autoimmune demyelinating disease through induction of myelin-specific regulatory CD8 T cell responses

Multiple Sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system (CNS). We have shown that CNS-specific CD8 T cells (CNS-CD8) possess a disease suppressive function in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). Previous studies have focused on the role of these cells predominantly in chronic models of disease, but the majority of MS patients present with a relapsing-remitting disease course. In this study, we evaluated the therapeutic role of CD8 T cells in the context of relapsing-remitting disease (RR-EAE), using SJL mice. We found that PLP_178-191- and MBP_84-104-CD8 ameliorated disease severity in an antigen-specific manner. In contrast, PLP_139-151-CD8 did not suppress disease. PLP_178-191-CD8 were able to reduce the number of relapses even when transferred during ongoing disease. We further ascertained that the suppressive subset of CD8 T cells was contained within the CD25 ⁺ CD8 T cell compartment post-in vitro activation with PLP_178-191. Using Listeria monocytogenes (LM) encoding CNS antigens to preferentially prime suppressive CD8 T cells in vivo, we show that LM infection induced disease suppressive CD8 T cells that protected and treated PLP_178-191 disease. Importantly, a combination of PLP_178-191-CD8 transfer boosted by LM-PLP_175-194 infection effectively treated ongoing disease induced by a non-cognate peptide (PLP_139-151), indicating that this approach could be effective even in the context of epitope spreading. These data support a potential immunotherapeutic strategy using CD8 transfer and/or LM vaccination to boost disease regulatory CD8 T cells.

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Adoptive transfer of CD8 T cells ameliorates RR-EAE in an antigen specific manner .

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Listeria monocytogenes (LM) can be used to prime disease-ameliorating CD8 T cells in RR-EAE .

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Activated CD25 ⁺ CD8 T cells preferentially harbor the disease-suppressive activity .

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Relapses in RR-EAE can be curbed using a dual strategy of CD8 T cell transfer and LM boosting .

Imaging Axonal Degeneration and Repair in Preclinical Animal Models of Multiple Sclerosis

Multiple sclerosis (MS) is a central nervous system (CNS) disease characterized by chronic neuroinflammation, demyelination, and axonal damage. Infiltration of activated lymphocytes and myeloid cells are thought to be primarily responsible for white matter damage and axonopathy. Over time, this neurologic damage manifests clinically as debilitating motor and cognitive symptoms. Existing MS therapies focus on symptom relief and delay of disease progression through reduction of neuroinflammation. However, long-term strategies to remyelinate, protect, or regenerate axons have remained elusive, posing a challenge to treating progressive forms of MS. Preclinical mouse models and techniques, such as immunohistochemistry, flow cytometry, and genomic and proteomic analysis have provided advances in our understanding of discrete time-points of pathology following disease induction. More recently, in vivo and in situ two-photon (2P) microscopy has made it possible to visualize continuous real-time cellular behavior and structural changes occurring within the CNS during neuropathology. Research utilizing 2P imaging to study axonopathy in neuroinflammatory demyelinating disease has focused on five areas: (1) axonal morphologic changes, (2) organelle transport and health, (3) relationship to inflammation, (4) neuronal excitotoxicity, and (5) regenerative therapies. 2P imaging may also be used to identify novel therapeutic targets via identification and clarification of dynamic cellular and molecular mechanisms of axonal regeneration and remyelination. Here, we review tools that have made 2P accessible for imaging neuropathologies and advances in our understanding of axonal degeneration and repair in preclinical models of demyelinating diseases.

Immunization with a peptide of Semliki Forest virus promotes remyelination in experimental autoimmune encephalomyelitis

Remyelination is one of the elusive topics in treatment of multiple sclerosis (MS). Our previous studies have shown that Semliki Forest virus (SFV)-infected δ-knock-out (KO) mice did not exhibit the extensive remyelination, seen in wild type (WT) B6 mice, after viral clearance and demyelination. The Remyelination in SFV-infected WT mice started on day 15 and was completed by day 35 post-infection (pi), whereas the KO mice remained partially demyelinated through day 42 pi. Treatment with E2 peptide2 in incomplete Freund's adjuvant (IFA), resulted in higher antibody production and earlier remyelination in SFV-infected KO (day 28 pi), than WT mice. This finding suggested that anti-E2 peptide2 antibody could play a part in remyelination. In the current study, the effect of E2 peptide2 treatment was evaluated in the experimental autoimmune encephalomyelitis (EAE) model. Mice with established EAE were treated with E2 peptide2 in IFA to develop antibody. Treated EAE mice made significantly higher anti-E2 peptide2 antibody than untreated EAE group. Average clinical disease scores were significantly lower in peptide treated compared to untreated EAE mice. Furthermore, histopathological and immunohistochemical studies demonstrated increased remyelinating areas and higher number of activated oligodendrocytes and astrocytes, in treated compared to untreated EAE groups. Moreover, the anti-E2 peptide2 antibody showed higher binding to the myelinated areas of treated than untreated EAE mice. We conclude that treatment with, or antibody to, SFV E2 peptide2 triggers some mechanism that promotes remyelination.

Immune checkpoints in central nervous system autoimmunity

A number of autoimmune diseases, including multiple sclerosis, are mediated by self-reactive T cells that have escaped the deletional mechanisms of central tolerance. Usually, these T cells are kept at bay through peripheral tolerance mechanisms, including regulation through coinhibitory receptors and suppression by regulatory T cells. However, if these mechanisms fail, self-reactive T cells are activated and autoimmune responses ensue. This review outlines how the coinhibitory receptors CTLA-4 (cytotoxic T-lymphocyte antigen-4), PD-1 (programed death-1), Tim-3 (T-cell immunoglobulin- and mucin domain-containing molecule 3), and TIGIT (T-cell immunoreceptor with immunoglobulin and ITIM domains) act at different checkpoints to inhibit autoreactive T cells and suppress the development of central nervous system autoimmunity. Loss of each of these receptors predisposes to autoimmunity, indicating a non-redundant role in maintaining peripheral tolerance. At the same time, their functional patterns seem to overlap to a large degree. Therefore, we propose that only the concerted action of a combination of inhibitory receptors is able to maintain peripheral tolerance and prevent autoimmunity.

The structural and functional role of myelin fast-migrating cerebrosides: pathological importance in multiple sclerosis

A family of neutral glycosphingolipids containing a 3-O-acetyl-sphingosine galactosylceramide (3-SAG) has been characterized. Seven new derivatives of galactosylceramide (GalCer), designated as fast-migrating cerebrosides (FMCs) by TLC retention factor, have been identified. The simplest compounds - FMC-1 and FMC-2 - of this series have been characterized as the 3-SAG containing nonhydroxy and hydroxy fatty acyl, respectively. The next two - FMC-3 and FMC-4 - add 6-O-acetyl-galactose and the most complex glycosphingolipids, FMC-5, -6 and -7, are 2,3,4,6-tetra-O-acetyl-3-SAG. These hydrophobic myelin lipid biomarkers coappear with GalCer during myelinogenesis and disappear along with GalCer in de- or dys-myelinating disorders. Myelin lipid antigens, including FMCs, are keys to myelin biology, opening the possibility of new and novel immune modulatory tools for treatment of autoimmune diseases including multiple sclerosis.

Experimental autoimmune encephalomyelitis as a testing paradigm for adjuvants and vaccines

Experimental autoimmune encephalomyelitis (EAE) is an experimental model for multiple sclerosis. EAE can be induced by inoculation with central nervous system (CNS) proteins or peptides emulsified in complete Freund's adjuvant. Protection from EAE, enhancement of EAE or subclinical priming for EAE can occur as a result of either live viral infection or DNA immunization with molecular mimics of CNS proteins or peptides. Here we review the published data describing modulation of EAE through administration of various CNS proteins/peptides introduced via live virus or plasmid DNA and modulation of EAE through choice of adjuvant (immunostimulating agents).

Studies in the modulation of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), an experimental model for multiple sclerosis, can be induced through inoculation with several different central nervous system (CNS) proteins or peptides. Modulation of EAE, resulting in either protection from EAE or enhancement of EAE, can also be accomplished through either vaccination or DNA immunization with molecular mimics of self-CNS proteins. Previously published data on this method of EAE modulation will be reviewed. New data is presented, which demonstrates that EAE can also be modulated through the administration of the beta-(1,3)-D-glucan, curdlan. Dendritic cells stimulated by curdlan are involved in the differentiation of the interleukin-17 producing subset of CD4(+) T cells that are recognized effector cells in EAE. Using two different systems to study the effects of curdlan on EAE, it was found that curdlan increased the incidence of EAE and/or the severity of the disease course.

Lipid autoreactivity in multiple sclerosis

Lipids comprise over 70% of the myelin sheath but have been largely underinvestigated as autoantigens in multiple sclerosis (MS). This paper cites evidence for the involvement of lipid autoreactivity in MS and details how self lipid cross-reactivity may also contribute to the development of type 1 diabetes and autoimmune thyroid disorders (both of which have been associated with MS). A further analysis of myelin chemistry suggests several mechanisms by which infection may contribute to etiology and trigger lipid autoreactivity via molecular mimicry. This analysis may aid the development of new therapies for autoimmune diseases.

Molecular and immunogenic features of myelin lipids: incitants or modulators of multiple sclerosis?

Myelin lipids have long been thought to play intriguing roles in the pathogenesis of multiple sclerosis (MS). This review summarizes current understanding of the molecular basis of MS with emphasis on the: (i.) physico-chemical properties, organization and accessibility of the lipids and their distribution within the myelin multilayer; (ii.) characterization of myelin lipid structures, and structure-function relationships relevant to MS mechanisms, and; (iii.) immunogenic and other features of lipids in MS including molecular mimicry, lipid enzyme genetic knockouts, glycolipid-reactive NKT cells, and monoclonal antibody-induced remyelination. New findings associate anti-lipid antibodies with pathophysiological biomarkers and suggest clinical utility. The structure of CD1d-lipid complexed with the lipophilic invariant T cell receptor (iTCR) may be crucial to understanding MS pathogenesis, and design of lipid antigen-specific therapeutics. Novel immuno-modulatory tools for treatment of autoimmune diseases including MS in which there is both constraint of inflammation and stimulation of remyelination are now emerging.

Repeated 0.5-Gy gamma irradiation attenuates experimental autoimmune encephalomyelitis with up-regulation of regulatory T cells and suppression of IL17 production

We recently reported attenuation of autoimmune disease by low-dose gamma irradiation (repeated doses of 0.5 Gy) in MRL-lpr/ lpr mice. Here we studied the effect of low-dose gamma irradiation on experimental autoimmune encephalomyelitis (EAE), which is a rodent model of multiple sclerosis. SJL/J mice were immunized with myelin basic protein for the induction of EAE and were exposed to 0.5 Gy gamma rays once a week for 4 weeks. Radiation suppressed incidence and disease severity scores and delayed the onset of pathological changes. Pro-inflammatory cytokines (IFN-gamma and IL6), autoantibody and CD8+ cytotoxic T cells are involved in the appearance of EAE. Radiation suppressed the increases in these cytokines and the autoantibody production and blocked the increase in the population of CD8+ cytotoxic T cells. Production of IL17 by Th17 cells and/or gammadelta T cells, which plays a crucial role in EAE, was also significantly suppressed by radiation. Furthermore, a significant increase in regulatory T cells, which are involved in suppression of autoimmune disease, was found in irradiated EAE mice. These data suggest that low-dose gamma irradiation attenuates EAE through suppression of pro-inflammatory cytokines, reduction of cytotoxic T cells and induction of regulatory T cells.

Myelin oligodendrocyte glycoprotein-specific T and B cells cooperate to induce a Devic-like disease in mice

Multiple sclerosis (MS) is a clinically and pathologically heterogeneous inflammatory/demyelinating disease of the CNS. In the MS variant Devic disease, lesions are predominantly found in the optic nerves and spinal cord but not the brain. The immunological bases of the different forms of MS are unknown. We previously generated myelin oligodendrocyte glycoprotein-specific (MOG-specific) TCR transgenic mice (TCRMOG mice; also referred to as 2D2 mice) and reported that a large proportion of these mice develop spontaneous isolated optic neuritis. We have now crossed the TCRMOG mice with MOG-specific Ig heavy-chain knock-in mice (IgHMOG mice; also referred to as Th mice), in which one-third of the B cells are specific for MOG. In these mice, MOG-specific B cells are very efficient in presenting MOG to the transgenic T cells and undergo class switching to IgG1 in the presence of the transgenic T cells. Sixty percent of TCRMOG x IgHMOG mice spontaneously developed a severe form of experimental autoimmune encephalomyelitis (EAE). Histological examination of the CNS revealed a selective distribution of meningeal and parenchymal inflammatory lesions in the spinal cord and optic nerves. Thus, CNS antigen-specific T and B cells cooperate to induce a distinct clinicopathologic EAE pattern that closely replicates human Devic disease.

Cell-based gene therapy experiments in murine experimental autoimmune encephalomyelitis

With the ultimate goal of developing a novel treatment for multiple sclerosis (MS), we have developed a cell-based gene therapy protocol for the treatment of murine experimental autoimmune encephalomyelitis (EAE), a powerful animal model for MS. We have determined that transduced fibroblasts secreting encephalogenic epitopes, when injected into mice with EAE, cause a striking abrogation of disease. Both myelin basic protein (MBP) and proteolipid protein mini-gene constructs expressed in syngeneic fibroblast cells were capable of ameliorating ongoing EAE induced by MBP protein. These experiments are crucial since they suggest that not all encephalogenic epitopes need be secreted for the control of disease. We also demonstrate the success of this protocol when transduced syngeneic, and most importantly, allogeneic cells are sequestered within an implantable chamber. Furthermore, we find that through modifying antigen expression by changing the signal sequence of the mini-gene construct, we were able to significantly reduce the dose of cells required for treatment. These improvements to the mini-gene delivery system are critical for the eventual translation of our protocol to the clinic.

Delineation of the minimal encephalitogenic epitope of proteolipid protein peptide(91-110) and critical residues required for induction of EAE in HLA-DR3 transgenic mice

Previously, we have reported that proteolipid protein (PLP) peptide 91-110 can induce experimental autoimmune encephalomyelitis (EAE) in HLA-DR3 transgenic (tg) mice. Here we, report that residues spanning 97-108 are the minimal epitope required for induction of EAE in DR3 mice. Utilizing a series of alanine-substituted peptides, positions 99, 101, 102, 103, 104, and 106 are identified as residues necessary for an immune response. Further analysis indicated that amino acid isoleucine (99), aspartate (102) and lysine (104) are anchor residues facilitating binding to HLA-DR3 molecules. These results may have applications in the future design of peptide based immunotherapy.

The Myelin-Associated Oligodendrocytic Basic Protein Region MOBP15–36 Encompasses the Immunodominant Major Encephalitogenic Epitope(s) for SJL/J Mice and Predicted Epitope(s) for Multiple Sclerosis-Associated HLA-DRB1*1501

Autoimmune response to the myelin-associated oligodendrocytic basic protein (MOBP), a CNS-specific myelin constituent, was recently suggested to play a role in the pathogenesis of multiple sclerosis (MS). The pathogenic autoimmune response to MOBP and the associated pathology in the CNS have not yet been fully investigated. In this study, we have characterized the clinical manifestations, pathology, T cell epitope-specificity, and TCRs associated with experimental autoimmune encephalomyelitis (EAE) induced in SJL/J mice with recombinant mouse MOBP (long isoform, 170 aa). Analysis of encephalitogenic MOBP-reactive T cells for reactivity to overlapping MOBP peptides defined MOBP15-36 as their major immunodominant epitope. Accordingly, MOBP15-36 was demonstrated to be the major encephalitogenic MOBP epitope for SJL/J mice, inducing severe/chronic clinical EAE associated with intense perivascular and parenchymal infiltrations, widespread demyelination, axonal loss, and remarkable optic neuritis. Molecular modeling of the interaction of I-A(s) with MOBP15-36, together with analysis of the MOBP15-36-specific T cell response to truncated peptides, suggests MOBP20-28 as the core sequence for I-A(s)-restricted recognition of the encephalitogenic region MOBP15-36. Although highly focused in their epitope specificity, the encephalitogenic MOBP-reactive T cells displayed a widespread usage of TCR Vbeta genes. These results would therefore favor epitope-directed, rather than TCR-targeted, approaches to therapy of MOBP-associated pathogenic autoimmunity. Localization by molecular modeling of a potential HLA-DRB1*1501-associated MOBP epitope within the encephalitogenic MOBP15-36 sequence suggests the potential relevance of T cell reactivity against MOBP15-36 to MS. The reactivity to MOBP15-36 detected in MS shown here and in another study further emphasizes the potential significance of this epitope for MS.

Gene therapy in a murine model for clinical application to multiple sclerosis

Female SJL/J mice, suffering from experimental autoimmune encephalomyelitis (EAE), were injected with 1 x 10(7) cells from a syngeneic fibroblast line transduced with a retroviral vector designed to encode proteolipid protein (101-157) targeted for secretion. A striking abrogation of both clinical and histological signs of disease resulted. The treatment was efficacious when given after the first or the third relapses, protected naive mice from challenge with spinal cord homogenate, and was dose dependent. This strategy was devised to provide a systemic, antigen-specific signal to pathogenic T cells in the absence of costimulation and, hence, render them anergic. Cytokine analyses of brain and spinal cord lymphocytes demonstrate that the treatment induces an antiinflammatory Th2 profile, indicating that this antigen-specific therapy acts by a cytokine-induced pathway. This study was designed for translation to the clinic. We envision using allogeneic transduced fibroblasts, encapsulated in a chamber, to deliver the antigen-specific signal. This will enable us to use one therapeutic cell line for all patients and to remove the device should the therapy exacerbate disease.

Insights into the immunopathogenesis of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). Significant progress has been made in our understanding of the etiology of MS. MS is widely believed to be an autoimmune disease that results from aberrant immune responses to CNS antigens. T cells are considered to be crucial in orchestrating an immunopathological cascade that results in damage to the myelin sheath. This review summarizes the currently available data supporting the idea that myelin reactive T cells are actively involved in the immunopathogenesis of MS. Some of the therapeutic strategies for MS are discussed with a focus on immunotherapies that aim to specifically target the myelin reactive T cells.

Granulocyte macrophage colony-stimulating factor: a new putative therapeutic target in multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis, can be induced by immunization with a number of myelin antigens. In particular, myelin oligodendrocyte glycoprotein, a central nervous system (CNS)-specific antigen expressed on the myelin surface, is able to induce a paralytic MS-like disease with extensive CNS inflammation and demyelination in several strains of animals. Although not well understood, the egress of immune cells into the CNS in EAE is governed by a complex interplay between pro and antiinflammatory cytokines and chemokines. The hematopoietic growth factor, granulocyte macrophage colony-stimulating factor (GM-CSF), is considered to play a central role in maintaining chronic inflammation. The present study was designed to investigate the previously unexplored role of GM-CSF in autoimmune-mediated demyelination. GM-CSF(-/)- mice are resistant to EAE, display decreased antigen-specific proliferation of splenocytes, and fail to sustain immune cell infiltrates in the CNS, thus revealing key activities for GM-CSF in the development of inflammatory demyelinating lesions and control of migration and/or proliferation of leukocytes within the CNS. These results hold implications for the pathogenesis of inflammatory and demyelinating diseases and may provide the basis for more effective therapies for inflammatory diseases, and more specifically for multiple sclerosis.

Expression of Golli mRNA during development in primary immune lymphoid organs of the rat

The gene-of-the-oligodendrocyte lineage (Golli)-MBP transcription unit contains three Golli-specific exons together with eight exons of the "classical" myelin basic protein (MBP) gene, yielding alternatively spliced proteins which share amino acid sequence with MBP. Unlike MBP, a late antigen expressed only in the nervous system, Golli gene products are expressed pre- and post-natally at many sites. In this study, we determined the sequence of Golli in rat by RT-PCR and 5' RACE and showed that Golli sequences are expressed in primary lymphoid organs as early as e16.5, which could explain the anergic rat T cell response we previously observed in Golli-induced meningitis.

Isolation of CD45RO+, memory T cells recognizing proteolipid protein from neurologically normal subjects

Previous studies provide evidence for in vivo activation of MBP-reactive T cells in subjects with multiple sclerosis. In general, in vivo activation occurs less frequently in healthy control subjects. In the current study we examined the T cell response to proteolipid protein in PBMC isolated from 9 control subjects. We used CD45 isotypes as markers for memory and naïve T cells to assess in vivo activation of CD4+ T cells reactive with PLP. In contrast to the results obtained using MBP, we found that approximately 50% of PLP-reactive T cells were derived from the CD45RO+ memory subpopulation of T cells isolated from these control subjects. These results indicate that some myelin-reactive T cells have undergone activation in vivo in neurologically intact individuals. This suggests that immunoregulatory mechanisms may be present that prevent overt disease in spite of in vivo activation of PLP-reactive T cells.

Immune responses against the myelin/oligodendrocyte glycoprotein in experimental autoimmune demyelination

Myelin/oligodendrocyte glycoprotein (MOG) is a surface-exposed antigen of myelin and an important target for autoimmune responses which mediate inflammatory demyelination in the central nervous system. Experimentally, MOG induces strong pathogenic T cell responses in many strains of laboratory animals. Immunological studies in humans also identify MOG as a surprisingly prevalent antigenic molecule among the myelin proteins. In addition, the encephalitogenic properties of MOG are linked to the induction of antibody responses which have been demonstrated to directly promote central nervous system demyelination, a hallmark neuropathological feature in disorders such as human multiple sclerosis. Factors responsible for autoimmunity to MOG likely include genetic influences as well as other mechanisms, which are the subject of intense investigation. This article reviews experimental data currently available on specificity and pathogenic roles of T cell and antibody responses against MOG, which have implications relevant to multiple sclerosis and related disorders.

Cytotoxic T lymphocyte antigen-4 (CTLA-4) regulates the size, reactivity, and function of a primed pool of CD4+ T cells

We examined how cytotoxic T lymphocyte antigen-4 (CTLA-4) regulates heterogeneous CD4(+) T cell responses by using experimental autoimmune encephalomyelitis (EAE), a CD4(+) T cell-mediated disease that is subject to regulation by CTLA-4. Disease incidence and severity were used as measures of in vivo CD4(+) T cell responses. The frequency, cytokine production, and reactivity of primed T cells were determined from animals immunized with proteolipid protein (PLP)-139-151 (disease agonist), PLP-Q (disease antagonist), or both peptides, and treated with control or anti-CTLA-4 antibody to analyze the responding population. CTLA-4 blockade exacerbated disease in PLP-139-151-primed animals and overcame disease antagonism in coimmunized animals, but did not permit disease induction in PLP-Q-primed animals. Experimental autoimmune encephalomyelitis enhancement was associated with increased frequencies of cytokine-producing cells and increased ratios of IFN-gamma to IL-4 secretors responsive to PLP-139-151. Priming with PLP-Q elicited IL-4 and IL-2, but not IFN-gamma secretors cross-reactive with PLP-139-151. Strikingly, CTLA-4 blockade was found to decrease rather than increase the frequencies of cross-reactive IL-4 and IL-2 secretors. Thus, CTLA-4 engagement limits the size, but increases the breadth, of reactivity of a primed pool of CD4(+) T cells, consequently regulating its function.

ICAM-1 expression in autoimmune encephalitis visualized using magnetic resonance imaging

The expression of leukocyte adhesion molecules in the intact brains of mice with experimental autoimmune encephalitis (EAE) was visualized by Magnetic Resonance Imaging (MRI) through the use of a new, target-specific MR contrast agent. Antibody-conjugated paramagnetic liposomes (ACPLs) were designed to achieve in vivo targeting of molecules expressed on vascular endothelium, while providing sufficient signal enhancement at these sites for detection by MRI. ACPLs targeted to intercellular adhesion molecule-1 (ICAM-1), an endothelial leukocyte receptor upregulated on cerebral microvasculature during EAE, were administered to diseased mice. Fluorescence microscopy confirmed that fluorescently-tagged ACPLs were localized to central nervous system (CNS) microvasculature in a pattern consistent with ICAM-1 upregulation described immunohistochemically. High resolution MRI of mouse brains ex vivo demonstrated that ACPL binding conferred significant enhancement of signal intensity (SI) as compared to control images. These results suggest that ACPLs can be used as MRI contrast agents to visualize specific molecules expressed on vascular endothelium during disease.

Hla-DR2-restricted responses to proteolipid protein 95-116 peptide cause autoimmune encephalitis in transgenic mice

In multiple sclerosis (MS) patients who carry the Class II major histocompatibility (MHC) type HLA-DR2, T cells specific for amino acids 95-116 in the proteolipid protein (PLP) are activated and clonally expanded. However, it remains unclear whether these autoreactive T cells play a pathogenic role or, rather, protect against the central nervous system (CNS) damage. We have addressed this issue, using mice transgenic for the human MHC class II region carrying the HLA-DR2 (DRB1* 1502) haplotype. After stimulating cultured lymph node cells repeatedly with PLP95-116, we generated 2 HLA-DR2-restricted, PLP95-116-specific T-cell lines (TCLs) from the transgenic mice immunized with this portion of PLP. The TCLs were CD4+ and produced T-helper 1 (Th1) cytokines in response to the peptide. These TCLs were adoptively transferred into RAG-2/2 mice expressing HLA-DR2 (DRG1* 1502) molecules. Mice receiving 1 of the TCLs developed a neurological disorder manifested ataxic movement without apparent paresis on day 3, 4, or 5 after cell transfer. Histological examination revealed inflammatory foci primarily restricted to the cerebrum and cerebellum, in association with scattered demyelinating lesions in the deep cerebral cortex. These results support a pathogenic role for PLP95-116-specific T cells in HLA-DR2+ MS patients, and shed light on the possible correlation between autoimmune target epitope and disease phenotype in human CNS autoimmune diseases.

Experimental autoimmune encephalomyelitis induced in B6.C-H-2bm12 mice by myelin oligodendrocyte glycoprotein: effect of MHC class II mutation on immunodominant epitope selection and fine epitope specificity of encephalitogenic T cells

The effect of the bm12 mutation on susceptibility to MOG-induced EAE, TCR repertoire and fine epitope specificity of the encephalitogenic T-cells, was assessed. prMOG35-55 was encephalitogenic for H-2bm12 and H-2b mice. Despite only minor differences in TCRVbeta expression and fine epitope specificity, H-2bm12/ and H-2b/prMOG35-55-specific T-cells failed to recognize Ab/prMOG35-55 and Abm12/prMOG35-55, respectively. rhMOG-induced EAE was milder in H-2bm12 mice, possibly as a result of co-dominant responses to prMOG35-55 and to the non-encephalitogenic pMOG94-116, rather than a single dominant response to prMOG35-55 in H-2b mice.

Molecular mimicry between a viral peptide and a myelin oligodendrocyte glycoprotein peptide induces autoimmune demyelinating disease in mice

Semliki Forest Virus (SFV) induces an encephalomyelitis followed by demyelination in the brains of C57Bl6/J (B6) mice. To investigate the role of molecular mimicry in the pathogenesis of postviral demyelination, alignment algorithms were used and amino acid homologies between immunogenic epitopes of SFV and myelin autoantigens, myelin basic protein (MBP), myelin proteolipid protein (PLP) and myelin oligodendrocyte glycoprotein (MOG) were identified. Immunization of B6 mice with SFV proteins induced significant lymphocyte proliferation to SFV E2 peptides and to MOG peptide, 18-32 (which had molecular mimicry with E2 115-129), but not to MBP or PLP peptides. Both MOG 18-32 and E2 115-129, induced a later-onset chronic EAE-like disease that correlated with the presence of multifocal vacuolation in the CNS white matter. This histopathology was reminiscent of the secondary demyelination seen following SFV infection. Serum antibody responses to the peptides appeared late after immunizations and some samples cross-reacted with other myelin peptides, as well as with the mimicked MOG peptides. These findings suggest that following a CNS viral infection, antibody response to an epitope of virus that exhibits molecular mimicry with a peptide of MOG may contribute to autoimmune mediated injury to CNS myelin.

Antigen presenting capacity of brain microvasculature in altered peptide ligand modulation of experimental allergic encephalomyelitis

Co-immunization with an altered peptide ligand (LR) partially protects SJL mice from proteolipid protein peptide 139-151-induced experimental allergic encephalomyelitis [Kuchroo, V.K., Greer, J.M., Kaul, D., Ishioka, G.Y., Franco, A., Sette, A., Sobel, R.A., Lees, M.B., 1994. A single TCR antagonist peptide inhibits experimental allergic encephalomyelitis mediated by a diverse T cell repertoire. J. Immunol. 153, 3326-3336; Santambrogio, L., Lees, M.B., Sobel, R.A., 1998. Altered peptide ligand modulation of experimental allergic encephalomyelitis: immune responses within the CNS. J. Neuroimmunol. 81, 1-13]. Clinical protection was noted despite extensive central nervous system inflammation observed after co-immunization with native and altered peptides. To extend our previous reports on this model, we now compare MHC class II expression and antigen presenting cell activity of cells associated with the blood-brain barrier in diseased and protected mice. Immunohistochemical studies identified MHC class II products on both the endothelial and microglial/macrophage populations. Ex vivo experiments suggested a correlation between the reduced clinical disease observed in the co-immunized mice and the antigen presenting activity of cells at the blood-brain barrier. The results suggest that antigen presenting activity is primarily mediated by macrophage-lineage cells of the central nervous system.

Magnetic resonance imaging of PLP-induced experimental allergic encephalomyelitis in Lewis rats

An in vivo magnetic resonance (MR) imaging study was performed on experimental allergic encephalomyelitis (EAE) induced in Lewis rats through proteolipid protein (PLP). PLP was solubilized in water or in an aqueous solution of 1% 10-tridecyl ether (TDE), a non-ionic detergent used in membrane protein research. All 16 rats immunized with 500 microg of TDE-solubilized PLP developed clinical signs and MR abnormalities fully comparable to those observed in MBP-induced EAE. Total paraplegia was observed in 12.5% of rats, mild or moderate paraparesis in 68.8% of rats and tail paralysis in the remaining 18.7% of rats. Whereas only 37.5% of the eight rats immunized with 500 microg of water-solubilized PLP developed minor clinical signs (tail weakness or paralysis). Our observations confirm that the difficulties encountered when trying to induce EAE by means of PLP arise from the highly hydrophobic nature of this protein. Accordingly, if a reproducible model is to be developed, it seems more judicious to use non-ionic detergents in both the extraction and solubilization phases of PLP preparation, this would allow maximal solubilization of the protein while avoiding aggregates, which may otherwise form during either of the PLP preparation.

IL-10 Is Critical in the Regulation of Autoimmune Encephalomyelitis as Demonstrated by Studies of IL-10- and IL-4-Deficient and Transgenic Mice

Experimental autoimmune encephalomyelitis (EAE) and other organ-specific autoimmune diseases are induced by autoantigen-specific Th1 cells. In contrast, transfer of autoantigen-reactive Th2 cells that produce IL-4 and IL-10 can prevent and/or reverse EAE. The relative roles of these two Th2 cytokines in the regulation of EAE has not been evaluated. Utilizing IL-4 and IL-10 knockout mice deficient for these cytokines and IL-10 and IL-4 transgenic mice overexpressing these cytokines, we demonstrate that IL-10-deficient mice (IL-10−/−) are more susceptible and develop a more severe EAE when compared with IL-4-deficient mice (IL-4−/−) or wild-type mice. T cells from IL-10−/− mice exhibit a stronger Ag-specific proliferation, produce more proinflammatory cytokines (IFN-γ and TNF-α) when stimulated with an encephalitogenic peptide, and induce very severe EAE upon transfer into wild-type mice. In contrast, while IL-4 transgenic mice develop similar disease compared with their nontransgenic littermates, mice transgenic for IL-10 are completely resistant to the development of EAE. Taken together, our data suggest that IL-10 plays a more critical role in the regulation of EAE by regulating autopathogenic Th1 responses.

T-cell responses to myelin antigens in multiple sclerosis; relevance of the predominant autoimmune reactivity to myelin oligodendrocyte glycoprotein

Until recently, the search for the 'culprit' autoantigen towards which deleterious autoimmunity is directed in multiple sclerosis (MS) centered mostly on myelin basic protein (MBP) and proteolipid (PLP), the two most abundant protein components of central nervous system (CNS) myelin, the target tissue for the autoimmune attack in MS. Although such research has yielded important data, furthering our understanding of the disease and opening avenues for possible immune-specific therapeutic approaches, attempts to unequivocally associate MS with MBP or PLP as primary target antigens in the disease have not been successful. This has led in recent years to a new perspective in MS research, whereby different CNS antigens are being investigated for their possible role in the initiation or progression of MS. Interesting studies in laboratory animals show that T-cells directed against certain non-myelin-specific CNS antigens are able to cause inflammation of the CNS, albeit without expression of clinical disease. However, reactivity to these antigens by MS T-cells has not been demonstrated. Conversely, reactivity by MS T-cells to non-myelin-specific antigens such as heat shock proteins, could be observed, but the pathogenic potential of such reactivity has not been corroborated with the encephalitogenicity of the antigen. More relevant to MS pathogenesis may be, as we outlined in this review, the autoimmune reactivity directed against minor myelin proteins, in particular the CNS-specific myelin oligodendrocyte glycoprotein (MOG). Here, we review the current knowledge gathered on T-cell reactivity to possible target antigens in MS in the context of their encephalitogenic potential, and underline the facets which make MOG a highly relevant contender as primary target antigen in MS, albeit not necessarily the only one.

A history of proteolipids: a personal memoir

This review is a personal memoir of the history of proteolipids and is limited to aspects of the field with which the author has been involved in one way or another. The discovery of proteolipids was a serendipitous observation made in the course of the study of sulfatides. Initial focus was on the chemical characterization of brain proteolipids, their behavior under different conditions and their identification as the major protein of CNS myelin. The sequence of PLP was obtained using solid phase protein sequencing techniques. This, in turn, made possible a new era in which biochemical, cellular and molecular approaches could be applied to address new questions about PLP. Identification of genetic defects in the PLP molecule and its regulation has contributed to understanding myelin biology. Studies of the encephalitogenic activity of PLP in animal models have influenced the views of inflammatory processes in multiple sclerosis. Despite remarkable progress, much remains to be learned about the structure and function of PLP.

Predominance of the autoimmune response to myelin oligodendrocyte glycoprotein (MOG) in multiple sclerosis: reactivity to the extracellular domain of MOG is directed against three main regions

Our previous analysis of the T cell reactivity to myelin antigens in a group of 24 patients with multiple sclerosis (MS) and 16 control individuals revealed that the autoimmune response to myelin oligodendrocyte glycoprotein (MOG) predominates in MS over that to myelin basic protein (MBP), proteolipid protein or myelin-associated glycoprotein, suggesting a prevalent role for the autoimmune response to MOG in the pathogenesis of MS. Using a recombinant human MOG (rhMOG) preparation corresponding to the extracellular immunoglobulin-like domain of the MOG molecule, we have now analyzed another group of 52 MS patients and 49 control individuals for reactivity of their peripheral blood lymphocytes (PBL) to rhMOG and to MBP concomitantly. Of the 52 MS patients tested 24 responded to MOG and 10 out of 49 responded to MBP, whereas only 5 MOG-reactive and 4 MBP-reactive control individuals were detected out of the 49 tested. These results are therefore highly confirmatory of the predominant reactivity to MOG in MS. The analysis of the primary proliferative response to 11 synthetic overlapping peptides (phMOG) spanning the extracellular domain of human MOG by PBL from 9 MS patients and 15 control individuals (9 healthy controls and 6 patients with neurological diseases other than MS) further supports a prevalent role for the autoimmune response to MOG in MS, as only 1 of the 15 controls tested showed reactivity to any of the phMOG, whilst 5 out of the 9 patients studied reacted to at least 1 of the phMOG. PBL from 10 MS patients, and from 4 controls, were selected in vitro with each of the phMOG. Of the 10 patients studied 7 reacted to at least 1 phMOG upon secondary stimulation and the reactivity was mostly directed to epitopes localized within three main regions (amino acids 1-22, 34-56 and 64-96), as was observed for the primary response of PBL. The predominant response to MOG of PBL from MS patients as demonstrated in two separate studies using native MOG and rhMOG as antigens, and the high incidence of reactivity of these PBL compared to the lack of response to phMOG by control PBL, emphasize the relevance of MOG in MS pathogenesis and support a primary role for the autoimmune T cell response to MOG in disease development.

Immune tolerance mediated by recombinant proteolipid protein prevents experimental autoimmune encephalomyelitis

Proteolipid protein (PLP), a transmembrane protein expressed only in the central nervous system (CNS), is a candidate target autoantigen for autoimmune-mediated demyelination. We have evaluated the effect of a recombinant form of the PLP protein, delta PLP4, in a murine model of experimental autoimmune encephalomyelitis (EAE). PLP-specific T-cell responses were observed following immunization of SJL/J, PL/J and SWR mice with delta PLP4, demonstrating processing of the protein to several distinct antigenic epitopes. Clinical EAE associated with inflammation and demyelination in the CNS also developed after sensitization of mice with delta PLP4 in adjuvant. Conversely, tolerance to delta PLP4 in adult mice and prevention of PLP peptide 139-151-induced EAE was induced by intravenous injection of soluble delta PLP4. The prevention of disease onset was paralleled by a significant reduction in demyelination and CNS inflammatory cell infiltration and diminished PLP139-151-specific T-cell proliferative responses. These results are consistent with the establishment of peripheral T-cell tolerance and reinforce the notion that recombinant myelin antigens and intravenous tolerance induction may prove useful in the modulation of the human demyelinating disease, multiple sclerosis (MS).

A T cell receptor antagonist peptide induces T cells that mediate bystander suppression and prevent autoimmune encephalomyelitis induced with multiple myelin antigens

Experimental autoimmune encephalomyelitis (EAE) induced with myelin proteolipid protein (PLP) residues 139-151 (HSLGKWLGHPDKF) can be prevented by treatment with a T cell receptor (TCR) antagonist peptide (L144/R147) generated by substituting at the two principal TCR contact residues in the encephalitogenic peptide. The TCR antagonist peptide blocks activation of encephalitogenic Th1 helper cells in vitro, but the mechanisms by which the antagonist peptide blocks EAE in vivo are not clear. Immunization with L144/R147 did not inhibit generation of PLP-(139-151)-specific T cells in vivo. Furthermore, preimmunization with L144/R147 protected mice from EAE induced with the encephalitogenic peptides PLP-(178-191) and myelin oligodendrocyte protein (MOG) residues 92-106 and with mouse myelin basic protein (MBP). These data suggest that the L144/R147 peptide does not act as an antagonist in vivo but mediates bystander suppression, probably by the generation of regulatory T cells. To confirm this we generated T cell lines and clones from animals immunized with PLP-(139-151) plus L144/R147. T cells specific for L144/R147 peptide were crossreactive with the native PLP-(139-151) peptide, produced Th2/Th0 cytokines, and suppressed EAE upon adoptive transfer. These studies demonstrate that TCR antagonist peptides may have multiple biological effects in vivo. One of the principal mechanisms by which these peptides inhibit autoimmunity is by the induction of regulatory T cells, leading to bystander suppression of EAE. These results have important implications for the treatment of autoimmune diseases where there are autopathogenic responses to multiple antigens in the target organ.

Enhancement of EAE and induction of autoantibodies to T-cell epitopes in mice infected with a recombinant vaccinia virus encoding myelin proteolipid protein

SJL/J mice were infected with a recombinant vaccinia virus encoding myelin proteolipid protein (PLP) (VVplp). Antibody responses to whole PLP and to encephalitogenic peptides, p139-151, p178-191 or p104-117 were measured after vaccination and following challenge with these three PLP peptides. Competitive ELISAs showed that antibodies to p139-151 and p178-191 represented the majority of antibodies in the anti-PLP antibody response following VVplp vaccination, since the antibodies to intact PLP could be inhibited 56, 35 and 1%, respectively, by p139-151, p178-191 and p104-117. After peptide challenge, epitope specific anti-peptide antibodies were enhanced. These anti-peptide antibodies also reacted with the intact PLP molecule. Interestingly, the mean titer of anti-p139-151 antibody in p139-151 challenged mice was significantly higher than that observed for anti-p178-191 in p178-191 and for anti-p104-117 in p104-117 challenged mice. Following peptide challenge, the anti-PLP IgG response shifted from an IgG1 to an IgG2a and 2b phenotype. In these mice, both the clinical disease and histological pattern of experimental allergic encephalomyelitis (EAE) were enhanced. The enhancement was most pronounced in the pathologic scores in the p139-151 challenged group followed by p104-117 challenged mice. Thus, humoral immune responses to PLP encephalitogenic peptides can be generated with virus encoding a self central nervous system (CNS) protein.

Specific blockade of CTLA-4/B7 interactions results in exacerbated clinical and histologic disease in an actively-induced model of experimental allergic encephalomyelitis

In addition to an antigen-specific signal, T cell activation requires an antigen-independent costimulatory signal provided by interaction of CD28 with B7 (CD80 and CD86) on the APC. By blocking B7 interactions, previous studies demonstrated the requirement for costimulation in the induction of experimental allergic encephalomyelitis (EAE). Recent studies suggest that unlike CD28, CTLA-4 (a second B7 ligand) delivers an inhibitory signal. To address the regulatory role of CTLA-4 in EAE, we used an antibody directed against CTLA-4 administered at the time of disease induction. This resulted in a significantly more severe clinical course and more inflammatory and demyelinating lesions in the CNS of anti-CTLA-4-treated mice. These data suggest that CTLA-4-mediated inhibitory signals can regulate the clinical severity and histologic parameters of neuroautoimmune disease.

Prior exposure to superantigen can inhibit or exacerbate autoimmune encephalomyelitis: T-cell repertoire engaged by the autoantigen determines clinical outcome

Experimental allergic encephalomyelitis (EAE) is inducible in experimental animals immunized with myelin basic protein (MBP), proteolipid protein (PLP) or their peptides. We compared T-cell responses to encephalitogenic epitopes of PLP(43-64) and MBP(Ac1-11) in a single mouse strain, (PL/J x SJL)F1. MBP(1-11)-specific T-cell hybridomas expressed predominantly TCR V beta 8 or V beta 4, while PLP(43-64)-specific hybridomas expressed a diverse TCR repertoire. To analyze the biologic significance of the TCR repertoire (limited vs. diverse) to disease susceptibility, we pretreated mice with a superantigen (SEB), and then induced disease with these autoantigens. Mice injected with SEB and immunized with MBP(Ac1-11) showed significant inhibition of EAE, whereas SEB-pretreated mice immunized with PLP(43-64) had an increased severity of EAE and developed a chronic disease. These data demonstrate that prior exposure to microbial superantigens can significantly alter the autoimmune disease course depending upon the TCR repertoire used by the autoantigen.

Treatment of experimental encephalomyelitis with a novel chimeric fusion protein of myelin basic protein and proteolipid protein

It has been shown that peripheral T cell tolerance can be induced by systemic antigen administration. We have been interested in using this phenomenon to develop antigen-specific immunotherapies for T cell-mediated autoimmune diseases. In patients with the demyelinating disease multiple sclerosis (MS), multiple potentially autoantigenic epitopes have been identified on the two major proteins of the myelin sheath, myelin basic protein (MBP) and proteolipid protein (PLP). To generate a tolerogenic protein for the therapy of patients with MS, we have produced a protein fusion between the 21.5-kD isoform of MBP (MBP21.5) and a genetically engineered form of PLP (deltaPLP4). In this report, we describe the effects of treatment with this agent (MP4) on clinical disease in a murine model of demyelinating disease, experimental autoimmune encephalomyelitis (EAE). Treatment of SJL/J mice with MP4 after induction of EAE either by active immunization or by adoptive transfer of activated T cells completely prevented subsequent clinical paralysis. Importantly, the administration of MP4 completely suppressed the development of EAE initiated by the cotransfer of both MBP- and PLP-activated T cells. Prevention of clinical disease after the intravenous injection of MP4 was paralleled by the formation of long-lived functional peptide-MHC complexes in vivo, as well as by a significant reduction in both MBP- and PLP-specific T cell proliferative responses. Mice treated with MP4 were resistant to disease when rechallenged with an encephalitogenic PLP peptide emulsified in CFA, indicating that MP4 administration had a prolonged effect in vivo. Administration of MP4 was also found to markedly ameliorate the course of established clinical disease. Finally, MP4 therapy was equally efficacious in mice defective in Fas expression. These results support the conclusion that MP4 protein is highly effective in suppressing disease caused by multiple neuroantigen epitopes in experimentally induced demyelinating disease.

Delineation of the minimal encephalitogenic epitope within the immunodominant region of myelin oligodendrocyte glycoprotein: diverse V beta gene usage by T cells recognizing the core epitope encephalitogenic for T cell receptor V beta b and T cell receptor V beta a H-2b mice

The nature of the autoimmune T cell response to myelin oligodendrocyte glycoprotein (MOG), recently recognized as a potential target antigen in multiple sclerosis (MS), has not yet been characterized, in contrast to the T cell reactivity to other potential target antigens in MS such as myelin basic protein and proteolipid protein. Here, we show that the encephalitogenicity of the recombinant Ig-like domain of human MOG is associated, in H-2 b mice, with an immunodominant T cell reactivity against a single region of MOG spanning amino acids 35-55, accounting for the previously reported strong encephalitogenic activity of pMOG 35-55. A single injection of pMOG 35-55 with or without administration of pertussis toxin was sufficient to induce severe clinical experimental autoimmune encephalomyelitis (EAE) in H-2 b mice. Encephalitogenic pMOG 35-55-specific T cell lines derived from C3H.SW (V beta b) mice were diverse in their TCR V beta gene usage (V beta 1, V beta 6, V beta 8 and V beta 15), although V beta 8.2 was most predominantly expressed (48%). However, V beta 8 + T cells may only be part of the encephalitogenic MOG-specific T cell repertoire in H-2 b mice, as demonstrated by the susceptibility of C57L (V beta a) mice to disease induced by pMOG 35-55. Encephalitogenic T cell lines from V beta a mice were also diverse in their TCR V beta gene usage (V beta 1, V beta 2, V beta 6, V beta 14 and V beta 16). Such a heterogeneous TCT V beta gene expression by pMOG 35-55/I-A b-reactive T cells from both V beta a and V beta b H-2 b mice suggested multiple epitopes within pMOG 35-55. Analysis of the pattern of reactivity by pMOG 35-55-reactive T cells to a set of truncated peptides was not commensurate with independent nested epitopes, but revealed a requirement for recognition of a core sequence, YRSPFSRVV (pMOG 40-48). However, optimal stimulation was obtained with longer peptides, with each additional amino acid flanking either the N or the C terminus differentially increasing the stimulatory capacity of pMOG 40-48. Nonetheless, pMOG 40-48 was the minimal encephalitogenic epitope for both V beta a and V beta b mice. Thus, the T cell reactivity against the immunodominant encephalitogenic region of MOG is characterized by a diverse V beta gene usage and a requirement for the same core epitope. This pattern of reactivity may favor epitope-directed, rather than TCR-targeted, approaches to immunospecific therapy for MOG-related autoimmune disease.

Copolymer 1 inhibits chronic relapsing experimental allergic encephalomyelitis induced by proteolipid protein (PLP) peptides in mice and interferes with PLP-specific T cell responses

Copolymer 1 (Cop 1) is a synthetic amino acid copolymer effective in suppression of experimental allergic encephalomyelitis (EAE) and developed as a candidate drug for multiple sclerosis (MS). In the present study, we induced chronic relapsing (CR)-EAE in (SJL/J X BALB/c)F1 mice by either whole spinal cord homogenate or two synthetic peptides of proteolipid protein (PLP), p139-151 and p178-191. When Cop 1 was added to the encephalitogenic inoculum, mice were almost completely resistant to disease induction. T cell lines to p139-151 and p178-191 were specific to these peptides. Their antigen-specific responses were inhibited by Cop 1 in a dose-dependent manner, while their polyclonal response to the superantigen staphylococcal enterotoxin A (SEA) was not affected by Cop 1. Using biotinylated PLP derivatives, we demonstrated that the two PLP peptides bound to I-A(s) molecules, and that their binding was completely inhibited by unlabelled Cop 1. Furthermore, Cop 1 could displace the PLP peptides from the MHC binding site. These results support the potential of Cop 1 as a broad-spectrum drug for MS.

An altered peptide ligand mediates immune deviation and prevents autoimmune encephalomyelitis

In experimental autoimmune encephalomyelitis (EAE) induced with myelin proteolipid protein (PLP) peptide 139-151, we have previously shown that the disease is mediated by Th1 cells, which recognize tryptophan 144 as the primary TCR contact point. Here we describe an altered peptide ligand (APL), generated by a single amino acid substitution (tryptophan to glutamine) at position 144 (Q144), which inhibits the development of EAE induced with the native PLP 139-151 peptide (W144). We show that the APL induces T cells that are cross-reactive with the native peptide and that these cells produce Th2 (IL-4 and IL-10) and Th0 (IFN gamma and IL-10) cytokines. Adoptive transfer of T cell lines generated with the APL confer protection from EAE. These data show that changing a single amino acid in an antigenic peptide can significantly influence T cell differentiation and suggest that immune deviation may be one of the mechanisms by which APLs can inhibit an autoimmune disease.

A myelin oligodendrocyte glycoprotein peptide induces typical chronic experimental autoimmune encephalomyelitis in H-2b mice: fine specificity and T cell receptor V beta expression of encephalitogenic T cells

A predominant response to myelin oligodendrocyte glycoprotein (MOG) was recently observed in patients with multiple sclerosis (MS). To study the possible pathogenic role of T cell response to MOG in MS, we have investigated the encephalitogenic potential of MOG. Synthetic MOG peptides, pMOG 1-21, 35-55, 67-87, 104-117 and 202-218, representing predicted T cell epitopes, were injected into C57BL/6J and C3H.SW (H-2b) mice. The mice developed significant specific T cell responses to pMOG 1-21, pMOG 35-55 and pMOG 104-117. However, pMOG 35-55 was the only MOG peptide which could induce neurological impairment. The highly reproducible disease was chronic, with ascending paralysis and neuropathology comparable with those observed in experimental autoimmune encephalomyelitis (EAE) induced by myelin basic protein or proteolipid protein, except that in H-2b mice the disease was consistently non-remitting. These features differ markedly from those which we recently observed in PL (H-2u) mice with pMOG 35-55-induced disease. In PL mice, pMOG 35-55-induces atypical chronic relapsing EAE, the expression and progression of which are unpredictable. Hence, in different mouse strains, the same MOG peptide can induce typical EAE characterized by ascending paralysis, or atypical EAE with unpredictable clinical signs. pMOG 35-55-specific T cells from H-2b mice recognized an epitope within amino acids 40-55 of the MOG molecule, and pMOG 40-55-reactive T cell lines were encephalitogenic upon transfer into syngeneic recipients. The encephalitogenic pMOG 35-55-reactive C57BL/6J T cell lines expressed V beta 1, V beta 6, V beta 8, V beta 14 and V beta 15 gene segments, and the pMOG 35-55-reactive C3H.SW T cell lines expressed V beta 1, V beta 2, V beta 6, V beta 8, V beta 10, V beta 14, and V beta 15 gene segments. However, in both mouse strains, the utilization of the V beta 8 gene product was predominant (40-43%). The highly reproducible encephalitogenic activity of pMOG 35-55 strongly suggests a pathogenic role for T cell reactivity to MOG in MS and supports the possibility that MOG may also be a primary target antigen in the disease.