Relapsing Experimental Allergic Encephalomyelitis Research Articles

CD80 Blockade Enhance Glucocorticoid-Induced Leucine Zipper Expression and Suppress Experimental Autoimmune Encephalomyelitis

Designing mimetic of the interface functional groups of known receptor-ligand complexes is an attractive strategy for developing potential therapeutic agents that interfere with target protein-protein interactions. The CD80/CD86-CD28/CD152 costimulatory interactions transmit signals for CD4(+) T cell activation and suppression and are critically involved in the initiation, progression, and reactivation of the immunopathology in multiple sclerosis. Differences in the pattern, levels, and kinetics of expression of CD80/CD86 molecules in conjunction with differences in the strength of the signals delivered upon binding CD28 or CD152 determine the outcome of the immune response. A temporal up-regulation of surface expression of CD80 relative to CD86 on APCs and CNS-infiltrating cells has been shown to correlate with disease progression in experimental autoimmune encephalomyelitis an animal model for multiple sclerosis. Hence blockade of the CD80 costimulatory axis has therapeutic potential in multiple sclerosis. In this study, we report the efficacy of a novel CD80-blocking agent CD80-competitive antagonist peptide (CD80-CAP) in suppressing clinical disease and relapse in experimental autoimmune encephalomyelitis. The CD80-CAP mediates protection by inhibiting proinflammatory cytokines and skewing toward anti-inflammatory response presumably by enhancing the expression of glucocorticoid-induced leucine zipper in activated CD4(+) T cells.

Role of pathogenic T cells and autoantibodies in relapse and progression of myelin oligodendrocyte glycoprotein‐induced autoimmune encephalomyelitis in LEW.1AV1 rats

Accumulating evidence suggests that T cells and autoantibodies reactive with myelin oligodendrocyte glycoprotein (MOG) play a critical role in the pathogenesis of multiple sclerosis (MS). In the present study, we have tried to elucidate the pathomechanisms of development and progression of the disease by analysing T cells and autoantibodies in MOG-induced rat experimental autoimmune encephalomyelitis (EAE), which exhibits various clinical subtypes mimicking MS. Analysis using overlapping peptides revealed that encephalitogenic epitopes resided in peptide 7 (P7, residue 91-108) and P8 (residue 103-125) of MOG. Immunization with MOGP7 and MOGP8 induced relapsing-remitting or secondary progressive EAE. T cells taken from MOG-immunized and MOGP7-immunized rats responded to MOG and MOGP7 and sera from MOG-immunized rats reacted to MOG and MOGP1. Significant epitope spreading was not observed at either T-cell or antibody levels. Interestingly, sera from MOGP7-immunized rats with clinical signs did not react to MOG and MOG peptides throughout the observation period, suggesting that disease development and relapse in MOGP7-induced EAE occur without autoantibodies. However, MOGP7 immunization with adoptive transfer of anti-MOG antibodies aggravated the clinical course of EAE only slightly. Analysis of antibodies against conformational epitope (cme) suggests that anti-MOG(cme) may play a role in the pathogenicity of anti-MOG antibodies. Collectively, these findings demonstrated that relapse of a certain type of MOG-induced EAE occurs without autoantibodies but that autoantibodies may play a role in disease progression. Relapses and the progression of MS-mimicking EAE are differently immunoregulated so immunotherapy should be designed appropriately on the basis of precise information.

Evaluating potential therapies for bladder dysfunction in a mouse model of multiple sclerosis with high-resolution ultrasonography

Background In multiple sclerosis (MS), demyelinating and neurodegenerative lesions develop throughout the central nervous system, which result in a loss of neurotransmission. As a result, people with MS exhibit a wide range of symptoms including dysfunction of the bladder, which can lead to urinary incontinence or retention. Such signs can develop in animal models of MS. Current assessments of bladder properties in animal models are generally invasive, electrophysiological techniques. Objective The use of a non-invasive, ultrasound system for measuring bladder volume in a mouse model of MS. Methods Chronic relapsing experimental autoimmune encephalomyelitis was induced in mice. The bladder volume was assessed using ultrasonography, during the disease course and following therapy with bethanechol chloride. Results It was demonstrated that volumes obtained ultrasonically positively-correlated (r = 0.960) with the urine volumes obtained by manual expression. It was also shown for the first time that bladder size increased significantly in mice with residual neurological deficit. Indeed, this increase in bladder size showed a strong, positive-correlation (r = 0.951) with the hind limb spasticity. Following treatment with bethanechol chloride, bladder volume significantly decreased in mice with chronic experimental autoimmune encephalomyelitis. Conclusion This study demonstrates a novel outcome measure in experimental MS that allows; repeated, non-invasive, high resolution ultrasonic monitoring of bladder function.

Circulating Ly-6C+ myeloid precursors migrate to the CNS and play a pathogenic role during autoimmune demyelinating disease

AbstractMature myeloid cells (macrophages and CD11b+ dendritic cells) form a prominent component of neuroinflammatory infiltrates in multiple sclerosis and experimental autoimmune encephalomyelitis (EAE). The mechanism by which these cells are replenished during relapsing and chronic neuroinflammation is poorly understood. Here we demonstrate that CD11b+CD62L+Ly6Chi monocytes with colony-forming potential are mobilized into the bloodstream by a granulocyte-macrophage colony-stimulating factor-dependent pathway immediately before EAE relapses. Circulating Ly6Chi monocytes traffic across the blood-brain barrier, up-regulate proinflammatory molecules, and differentiate into central nervous system dendritic cells and macrophages. Enrichment of Ly6Chi monocytes in the circulating pool is associated with an earlier onset and increased severity of clinical EAE. Our studies indicate that granulocyte-macrophage colony-stimulating factor–driven release of Ly6Chi precursors from the bone marrow prevents exhaustion of central nervous system myeloid populations during relapsing or chronic autoimmune demyelination, suggesting a novel pathway for therapeutic targeting.

Surgical excision of CNS‐draining lymph nodes reduces relapse severity in chronic‐relapsing experimental autoimmune encephalomyelitis

Despite lack of classical lymphatic vessels in the central nervous system (CNS), cells and antigens do reach the CNS-draining lymph nodes. These lymph nodes are specialized to mediate mucosal immune tolerance, but can also generate T- and B-cell immunity. Their role in multiple sclerosis and experimental autoimmune encephalomyelitis (EAE) therefore remains elusive. We hypothesized that drainage of CNS antigens to the CNS-draining lymph nodes is vital for the recurrent episodes of CNS inflammation. To test this, we surgically removed the superficial cervical lymph nodes, deep cervical lymph nodes, and the lumbar lymph nodes prior to disease induction in three mouse EAE models, representing acute, chronic, and chronic-relapsing EAE. Excision of the CNS-draining lymph nodes in chronic-relapsing EAE reduced and delayed the relapse burden and EAE pathology within the spinal cord, which suggests initiation of CNS antigen-specific immune responses within the CNS-draining lymph nodes. Indeed, superficial cervical lymph nodes from EAE-affected mice demonstrated proliferation against the immunizing peptide, and the deep cervical lymph nodes, lumbar lymph nodes, and spleen demonstrated additional proliferation against other myelin antigen epitopes. This indicates that intermolecular epitope spreading occurs and that CNS antigen-specific immune responses are differentially generated within the different CNS-draining lymphoid organs. Proliferation of splenocytes from lymphadenectomized and sham-operated mice against the immunizing peptide was similar. These data suggest a role for CNS-draining lymph nodes in the induction of detrimental immune responses in EAE relapses, and conclusively demonstrate that the tolerance-inducing capability of cervical lymph nodes is not involved in EAE.

The acute and chronic phases of chronic relapsing experimental autoimmune encephalomyelitis (CR EAE) are ameliorated by the peroxynitrite decomposition catalyst, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinatoiron (III) chloride, (FeTPPS)

There is increasing evidence that the oxidative radical, peroxynitrite (ONOO −), is involved in the pathogenesis of inflammatory diseases including multiple sclerosis and the animal counterpart, experimental autoimmune encephalomyelitis (EAE). Compounds that impede the actions of ONOO − have proved useful in the control of EAE. In particular, catalytic isomerisation of ONOO − to inactive nitrate, through the use of metalloporphyrins, curtails the cellular response to inflammatory stimuli and halts the progression of neuroinflammation during EAE. The present study examined the pharmacological effects of the metalloporphyrin and ONOO − decomposition catalyst 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinatoiron(III)chloride (FeTPPS) on the acute and relapse phases of chronic relapsing (CR) EAE. Administration of FeTPPS to CR EAE-inoculated Biozzi mice commenced either therapeutically and immediately prior to the emergence of acute or relapse symptoms, or prophylactically, from the onset of remission of acute neurological signs. Drug therapy reduced acute and relapse symptoms but, and in contrast to the former phase, was of limited benefit in preventing histological changes during the latter stage of disease. In contrast, prophylactic FeTPPS was effective in limiting CNS pathology and neurological deficits. The findings confirm the inhibitory effects of FeTPPS on acute stage EAE. Moreover, the study extends previous observations by verifying compound efficacy on relapsing disease. Use of metalloporphyrins, such as FeTPPS, again highlights the important role played by ONOO − in the development of inflammatory diseases such as EAE.

PD‐1 ligands expressed on myeloid‐derived APC in the CNS regulate T‐cell responses in EAE

Disease progression in experimental autoimmune encephalomyelitis (EAE) is regulated by programmed death receptor 1 (PD-1) and its ligands, B7-H1 (programmed death ligand 1 (PD-L1)) and B7-DC (PD-L2). B7-H1 and B7-DC have negative regulatory effects upon binding PD-1 on activated T cells and B7-H1 deficiency increases severity of both diabetes and EAE. However, the role of PD-L expression on different APC in the CNS in regulating local T-cell function during relapsing EAE has not been examined. Our data show that the majority of CNS CD4+ T cells isolated during acute EAE are PD-1+, and T cells specific for relapse-associated epitopes express PD-1 upon antigen stimulation in the CNS. B7-H1 and B7-DC are differentially expressed on discrete APC populations in the inflamed CNS. B7-H1 and PD-1 have mainly inhibitory functions on CNS T cells. B7-H1 negatively regulates the stimulation of activated PD-1+ T(H) cells, in co-cultures with microglia and different CNS-infiltrating APC presenting endogenously processed peptides. The preponderance of IFN-gamma+ versus IL-17+ T cells in the CNS of B7-H1(-/-) mice suggests that B7-H1 more selectively suppresses T(H)-1 than T(H)-17 responses in vivo. In contrast, blockade of B7-DC has less pronounced regulatory effects. Overall, the results demonstrate that B7-H1 expressed by CNS myeloid APC negatively regulates T-cell activation during acute relapsing EAE.

Blockade of cytosolic phospholipase A 2α prevents experimental autoimmune encephalomyelitis and diminishes development of Th1 and Th17 responses

Cytosolic phospholipase A 2α (cPLA 2α) is the rate-limiting enzyme for release of arachidonic acid, which is converted primarily to prostaglandins via the cyclooxygenase (COX) 1/2 pathways, and leukotrienes via the 5-lipoxygenase (LO) pathway. We utilized inhibitors of cPLA 2α, COX-1/2 and 5-LO to determine the potential roles of these enzymes in development of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Blocking cPLA 2α prevented EAE development and greatly reduced antigen-induced production of Th1-type cytokines and IL-17. Blocking COX-1/2 delayed onset and reduced severity of EAE, and reduced production of Th1-type cytokines, but not IL-17. Blocking 5-LO delayed onset and reduced cumulative severity of EAE, but did not reduce production of Th1-type cytokines or IL-17. Finally, blockade of cPLA 2α from the onset of clinical EAE reduced duration of EAE relapses. Therefore, cPLA 2α represents a potential therapeutic target for treatment of MS.

Macrophages in T cell line-mediated, demyelinating, and chronic relapsing experimental autoimmune encephalomyelitis in Lewis rats.

About 50% of the mononuclear cells in the perivascular lesions in the central nervous system (CNS) of rats suffering from experimental allergic encephalomyelitis (EAE) are blood-borne macrophages. In this study we investigated the role of these macrophages in different variants of EAE, using a liposome-mediated macrophage depletion technique. Intravenously injected liposomes containing dichloromethylene diphosphonate (Cl2MDP) are ingested by macrophages and cause temporary and selective elimination of these cells. Macrophage depletion during EAE induced by a T cell line specific for myelin basic protein (MBP; T cell-EAE) suppresses development of neurological signs of EAE. T cell-EAE with pronounced demyelination as induced by an additionally injected MoAb directed against myelin oligodendrocyte glycoprotein (MOG) was also significantly ameliorated after macrophage depletion. During chronic relapsing EAE (CR-EAE) the occurrence of relapses was prevented or suppressed, provided that the liposomes were injected before the initiation of a putative relapse. A chronic progressive course of CR-EAE was not modified by Cl2MDP containing liposome treatment. Histologic examination of the CNS of liposome-treated animals confirmed decreased infiltration of macrophages into the parenchyma in the rats with T cell and AD-EAE, whereas T cells were still present.

Stem cell based delivery of IFN-β reduces relapses in experimental autoimmune encephalomyelitis

Interferon-beta (IFN-β), an approved treatment of multiple sclerosis (MS), produces only partial clinical responses. IFN-β therapy has been limited by its short serum half-life and limited ability to cross the blood brain barrier. We have developed a means of delivering the IFN-β gene both systemically and into the central nervous system (CNS) using bone marrow stem cells (BMSCs) as a vehicle and examined the therapeutic efficacy of this approach in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. A retroviral expression vector (pLXSN-IFNβ) was used to stably transfect virus producer PA317 cells to generate retrovirus containing the IFN-β gene which then was used to transduce BMSCs. IFN-β engineered BMSCs were transplanted (i.v.) into mice that then were immunized with proteolipoprotein (PLP) to initiate EAE. IFN-β-engineered BMSCs transplanted mice showed a significant inhibition of EAE onset, and the overall clinical severity was less compared to control groups. IFN-β delivery strongly reduced infiltration of mononuclear cells possibly by inhibiting cell adhesion molecules. Reduced demyelination and increased remyelination were also observed in the IFN-β treated group. Furthermore, inhibition of the pro-inflammatory cytokines TNF-α, IFN-γ and IL-12 and enhanced expression of the anti-inflammatory cytokines IL-10, IL-4 and TGF-β was observed in CNS tissue. In addition, mice receiving IFN-β had reduced apoptosis and increases in growth promoting factors including BDNF, CNTF, PDGF and VEGF. These results suggest that BMSCs can be used as vehicles to deliver the IFN-β into the CNS. This is a potentially novel therapeutic approach which might be used in MS and other diseases of the CNS in which drug access is limited.

The Th17–ELR+ CXC chemokine pathway is essential for the development of central nervous system autoimmune disease

The ELR+ CXC chemokines CXCL1 and CXCL2 are up-regulated in the central nervous system (CNS) during multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). However, their functional significance and the pathways regulating their expression are largely unknown. We show that transfer of encephalitogenic CD4+ Th17 cells is sufficient to induce CXCL1 and CXCL2 transcription in the spinal cords of naive, syngeneic recipients. Blockade or genetic silencing of CXCR2, a major receptor for these chemokines in mice, abrogates blood–brain barrier (BBB) breakdown, CNS infiltration by leukocytes, and the development of clinical deficits during the presentation as well as relapses of EAE. Depletion of circulating polymorphonuclear leukocytes (PMN) had a similar therapeutic effect. Furthermore, injection of CXCR2+ PMN into CXCR2−/− mice was sufficient to restore susceptibility to EAE. Our findings reveal that a Th17–ELR+ CXC chemokine pathway is critical for granulocyte mobilization, BBB compromise, and the clinical manifestation of autoimmune demyelination in myelin peptide–sensitized mice, and suggest new therapeutic targets for diseases such as MS.

Different clinical course of experimental autoimmune encephalomyelitis (EAE) in neurointermediate pituitary lobectomized (NIL) plus adrenalectomized (ADX) Lewis and Wistar rats

We have described that NIL Lewis rats develop mild signs of acute EAE with no changes in the HPA axis activity. Lewis and Wistar rats develop EAE, but differences in the HPA axis response to EAE exist between them. This suggests a different strain‐specific role of corticosterone (CO) in the immunoregulation of the EAE. Here we study the effects of CO and neurohypophyseal (NH) hormones deficiency (NIL) on the EAE. Rats from both strains were sham operated (SHAM) or NIL. Three weeks after surgeries rats were immunized with an encephalitogenic emulsion, and clinical course of EAE registered before and after ADX (performed at 27 day post‐immunization (DPI)). SHAM animals of both strains developed similar transient paralytic scores of EAE (10–20 DPI). In both strains, NIL induced decreased scores of the EAE. In Wistar SHAM ADX and NIL ADX groups no relapses of EAE occurred, whereas in Lewis SHAM ADX and NIL ADX groups a prompt and worse relapse of the EAE occurred, similar to the observed in the acute paralysis.Conclusions: 1) In NIL Wistar and Lewis groups, decreased severity of the EAE is under the NH hormones control, 2) In Wistar rats CO‐independent mechanisms protect against the EAE relapses, 3) In Lewis rats CO is required to protect against the EAE relapses, 4) Although NH hormones and CO participate in the immunopathology of the EAE it seems that they work through different mechanisms.

Autoimmune-induced preferential depletion of myelin-associated glycoprotein (MAG) is genetically regulated in relapsing EAE (B6 × SJL) F1 mice

BackgroundExperimental autoimmune encephalomyelitis (EAE) is commonly used to investigate mechanisms of autoimmune-mediated damage to oligodendrocytes, myelin, and axons in multiple sclerosis (MS). Four distinct autoimmune mechanisms with subsequently distinct patterns of demyelination have been recognized in acute MS lesions. EAE correlates for those distinct patterns of MS lesions are unknown. An excessive loss of myelin-associated glycoprotein (MAG), as a result of distal oligodendrogliopathy, is found exclusively in the subtype III lesion. We sought to answer if types of demyelination in acute lesions during onset and relapse of EAE can replicate the specific patterns observed in MS acute lesions.MethodsIn parental H-2b (C57BL/6, B6) and hybrid H-2b/s [(B6 × SJL) F1] EAE mice, we examined spinal cord levels of MOG, MAG, and myelin basic protein (MBP), and compared to levels of axonal neurofilament (NF160) to assess axonal function, and levels of PARPp85 as an indicator of irreversible apoptosis.ResultsDuring disease onset, levels of MOG significantly dropped in both strains, although more profoundly in H-2b/s mice. Levels of MOG recovered in relapsing mice of both strains. Regulation of MAG was dissimilar to MOG. Modest loss of MAG was found at disease onset in both strains of mice. Unexpectedly, in relapsing H-2b/s mice, a major depletion of MAG and NF160, accompanied with sharp elevation of PARPp85 levels, was measured. PARPp85 immunoreactivity was observed in cytoplasm and nuclei of some MBP containing cells.ConclusionTaken together, our results show genetically controlled distinct patterns of MOG and MAG depletion, in MOG35–55 induced EAE in H-2b and H-2b/s mice. The data also suggest distinctive immune regulation of acute lesions that develop in relapsing compared to disease onset. A profound depletion of MAG, concomitant with marked depletion of axonal NF160, and sharp elevation of PARPp85 levels, occurred exclusively in relapsing H-2b/s mice. Our findings suggest concurrence of sharp decrease of MAG levels, axonal dysfunction and irreversible apoptosis with severe relapsing disease in H-2b/s mice. We propose that MOG-induced EAE in H-2b/s mice may prove as a useful model in studying mechanisms, which govern autoimmune-induced preferential loss of MAG, and its impact on oligodendroglial pathology.

Disease Progression After Bone Marrow Transplantation in a Model of Multiple Sclerosis Is Associated With Chronic Microglial and Glial Progenitor Response

Multiple sclerosis (MS), the most common nontraumatic cause of neurologic disability in young adults in economically developed countries, is characterized by inflammation, gliosis, demyelination, and neuronal degeneration in the CNS. Bone marrow transplantation (BMT) can suppress inflammatory disease in a majority of patients with MS but retards clinical progression only in patients treated in the early stages of the disease. Here, we applied BMT in a mouse model of neuroinflammation, experimental autoimmune encephalomyelitis (EAE), and investigated the kinetics of reconstitution of the immune system in the periphery and in the CNS using bone marrow cells isolated from syngeneic donors constitutively expressing green fluorescent protein. This approach allowed us to dissect the contribution of donor cells to the turnover of resident microglia and to the pathogenesis of observed disease relapses after BMT. BMT effectively blocked or delayed EAE development when mice were treated early in the course of the disease but was without effect in mice with chronic disease. We found that there is minimal overall replacement of host microglia with donor cells in the CNS and that newly transplanted cells do not appear to contribute to disease progression. In contrast, EAE relapses are accompanied by the robust activation of endogenous microglial and macroglial cells, which further involves the maturation of endogenous Olig2 glial progenitor cells into reactive astrocytes through the cytoplasmic translocation of Olig2 and the expression of CD44 on the cellular membrane. The observed maturation of large numbers of reactive astrocytes from glial progenitors and the chronic activation of host microglial cells have relevance for our understanding of the resident glial response to inflammatory injury in the CNS. Our data indicate that reactivation of a local inflammatory process after BMT is sustained predominantly by endogenous microglia/macrophages.

Expression of Chemokine Receptors CCR7 and CCR8 in the CNS During ChREAE

Chemokines and their receptors are important players in organism homeostasis, development and immune response to inflammatory stimuli. It has been recently confirmed that they are also involved in the development of several autoimmune diseases. In this study, we analysed the expression of two recently identified CC chemokine receptors, CCR7 and CCR8, in the central nervous system (CNS) and in peripheral tissues during chronic relapsing experimental autoimmune encephalomyelitis (ChREAE) -- an animal model of the human demyelinating disease multiple sclerosis (MS). We observed upregulation of both chemokine receptors in the CNS during the first and second attacks of ChREAE, whereas disease remission was characterized by a lower expression of those receptors. An analysis of the kinetics of CCR7 and CCR8 expression in the CNS during the first attack of the disease showed a constant increase in the first few days after the onset of clinical signs. This expression correlated with the clinical severity of ChREAE. CCR7-positive mononuclear cells were detected mostly in perivascular inflammatory cuffs in the CNS. In peripheral tissues (the spleen and kidneys) expression of both receptors was not upregulated during active ChREAE. These findings suggest that CCR7 and CCR8 may play a significant role in the pathogenesis of EAE and probably MS.

Th17 and Th1 responses directed against the immunizing epitope, as opposed to secondary epitopes, dominate the autoimmune repertoire during relapses of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory demyelinating disease with similarities to multiple sclerosis (MS). It has been suggested that relapses of EAE and MS may be associated with, and even driven by, T cells specific for novel epitopes that are primed during the course of tissue destruction in the target organ or in secondary lymphoid tissues. We show, however, that IFNgamma and IL-17 responses against the immunizing epitope remain dominant through out the course of multiphasic EAE. Furthermore, induction of tolerance against a putative secondary epitope did not prevent clinical relapses.

T Cell Repertoire Diversity Is Required for Relapses in Myelin Oligodendrocyte Glycoprotein-Induced Experimental Autoimmune Encephalomyelitis

Comparison of TCRalphabeta repertoires of myelin oligodendrocyte glycoprotein (MOG)-specific T lymphocytes in C57BL/6 and TdT-deficient littermates (TdT(-/-)) generated during experimental autoimmune encephalomyelitis (EAE) highlights a link between a diversified TCRalphabeta repertoire and EAE relapses. At the onset of the disease, the EAE-severity is identical in TdT(+/-) and TdT(-/-) mice and the neuropathologic public MOG-specific T cell repertoires express closely similar public Valpha-Jalpha and Vbeta-Jbeta rearrangements in both strains. However, whereas TdT(+/+) and TdT(+/-) mice undergo successive EAE relapses, TdT(-/-) mice recover definitively and the lack of relapses does not stem from dominant regulatory mechanisms. During the first relapse of the disease in TdT(+/-) mice, new public Valpha-Jalpha and Vbeta-Jbeta rearrangements emerge that are distinct from those detected at the onset of the disease. Most of these rearrangements contain N additions and are found in CNS-infiltrating T lymphocytes. Furthermore, CD4(+) T splenocytes bearing these rearrangements proliferate to the immunodominant epitope of MOG and not to other immunodominant epitopes of proteolipid protein and myelin basic protein autoantigens, excluding epitope spreading to these myelin proteins. Thus, in addition to epitope spreading, a novel mechanism involving TCRalphabeta repertoire diversification contributes to autoimmune progression.

Antigen Presentation in the CNS by Myeloid Dendritic Cells Drives Progression of Relapsing Experimental Autoimmune Encephalomyelitis

Chronic progression of relapsing experimental autoimmune encephalomyelitis (R-EAE), a mouse model of multiple sclerosis (MS), is dependent on the activation of T cells to endogenous myelin epitopes, that is, epitope spreading. This review focuses on the cellular and molecular mechanisms underlying the process of epitope spreading. Surprisingly, activation of naïve T cells to endogenous myelin epitopes in SJL mice undergoing R-EAE occurs directly in the central nervous system (CNS), a site generally perceived to be immunologically privileged. Determination of the antigen presentation capacity of antigen-presenting cell (APC) populations purified from the CNS of mice with established R-EAE shows that peripherally derived CD11b(+)CD11c(+)CD45(hi) myeloid dendritic cells (mDCs) most efficiently present endogenous myelin antigens to activate both preactivated effector myelin-specific T cells and naïve T cells. The mDCs, which drive epitope spreading, preferentially polarize pathogenic Th17 responses correlating with their enhanced expression of TGF-beta1, IL-6, and IL-23. Both B220(+)CD11c(+) plasmacytoid (pDCs) and CD8alpha(+)CD11c(+) (CD8 DCs) were superior to CD11b(+)CD11c(-)CD45(hi) macrophages, but less efficient than mDCs at presenting endogenous peptide to induce Th17 cells. In contrast, CNS-resident CD11b(+)CD11c(-)CD45(low) microglia purified from the inflamed CNS were found to be largely incapable of activating either naïve or effector T cells.

In vivo monitoring the fate of Cy5.5-Tat labeled T lymphocytes by quantitative near-infrared fluorescence imaging during acute brain inflammation in a rat model of experimental autoimmune encephalomyelitis

T cells and macrophages directed against myelin proteins orchestrate the inflammation process in multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). So far, assessment of macrophages infiltration or structural alterations has been achieved by in vivo imaging. In this work, we show the infiltration of Cy5.5-labeled T lymphocytes into the brains of EAE rats by reflectance near-infrared fluorescence imaging. T lymphocytes were labeled with Cy5.5-Tat and administered intravenously to naïve or EAE animals. The highest fluorescence signal was observed for EAE animals, which received myelin-activated T cells during the acute phase of the disease. The temporal profile of fluorescence in this group paralleled the pattern of neurological impairment during the acute phase, the remittance and first relapses of EAE. No disease specific fluorescence pattern was observed for EAE animals, which received naïve T cells. However, uptake of Cy5.5-Tat by scavenger cells (e.g. macrophages) following death of labeled T cells in vivo prevents prolonged longitudinal studies. Our work demonstrates that Cy5.5-Tat labeling of T cells is suitable for in vivo fluorescence imaging of inflammation initiation in the EAE model. This approach may particularly be useful for evaluation of novel anti-inflammatory therapies .

Monomeric DR2/MOG-35–55 recombinant TCR ligand treats relapses of experimental encephalomyelitis in DR2 transgenic mice

Treatment of human autoimmune diseases such as multiple sclerosis (MS) will likely require agents that can prevent or reverse the inflammatory process that results in clinical relapses and disease progression. We evaluated the ability of a newly designed monomeric recombinant TCR ligand (RTL342M) containing HLA-DR2 peptide-binding domains covalently linked to MOG-35–55 peptide to prevent and treat both the initial episode and subsequent relapses of experimental autoimmune encephalomyelitis (EAE) in HLA-DR2 transgenic mice. Single doses of RTL342M given either i.v. or s.c. to HLA-DR2 mice produced a rapid (within 24 h) and dose-dependent reversal of clinical signs of paralytic EAE, and even a single dose ≤ 2 μg could produce a significant treatment effect. Multiple daily doses were even more effective than the same total amount of RTL given as a single dose. By establishing the minimal effective dose, we determined that RTLs may be 50 times more potent than molar equivalent doses of myelin peptide alone. RTL342M given prior to induction of EAE prevented disease in most mice, and the remainder could be successfully retreated with RTL. Most important for clinical application, RTL342M was highly effective for treating EAE relapses when given periodically prior to the relapse or even after relapses had occurred. These data demonstrate the rapid and potent clinical effects of RTL342M at disease onset and during relapses in EAE and establish important principles governing the application of this novel approach as a possible therapy for patients with MS.