Experimental autoimmune panencephalitis and uveoretinitis transferred to the Lewis rat by T lymphocytes specific for the S100 beta molecule, a calcium binding protein of astroglia

Comprehensive Update on Multiple Sclerosis-Associated Uveitis and New Epidemiological Insights from the United Kingdom

Multiple sclerosis (MS)-associated uveitis is characterised most frequently by bilateral intermediate uveitis with peripheral vascular leakage or panuveitis. The interesting association between these autoimmune diseases, which develop in two immune-privileged sites, places some undifferentiated uveitis patients at heightened risk of demyelination and clinical MS precipitation from the use of licensed anti-tumour necrosis factor α (TNFα) biologic therapy. However, their association may also open novel treatment avenues, considering the rapidly expanding arsenal of highly effective MS disease-modifying therapies. Here, we offer new data on MS-uveitis from the first national population-representative matched case-control and cohort study, using IQVIA medical research data (IMRD-UK), a primary care database of 11 million people. Amongst 25 thousand uveitis cases, patients with (any) uveitis are nearly three times more likely than matched controls to develop MS by 15 years follow-up (adjusted Hazard 2.7 (95% CI 2.1-3.6, p < 0.001)), but the proportion of MS-uveitis is low overall (0.72%, 180/24,895 uveitis cases). What tools might enhance MS risk stratification in uveitis patients in the future? In this comprehensive narrative review, we summarise primary observational data informing our epidemiological understanding of the association between MS and uveitis, and its variable clinical presentations, to highlight the state of play, and the important questions that remain in MS-uveitis.

Insights into multiple sclerosis-associated uveitis: a scoping review

PURPOSE

This paper is a scoping review of research on multiple sclerosis (MS)-associated uveitis to determine its epidemiology, pathophysiology, clinical features and treatment.

METHODS

A comprehensive search of the medical databases MEDLINE (PubMed), EMBASE, Web of Science and Cochrane was carried out on 25 November 2019, to identify papers published between 1980 and 2019 that focus on patients with MS-associated uveitis.

RESULTS

Based on large cohort studies (n ≥ 1000), the prevalence of uveitis in patients with MS is estimated to be 0.53-1.34% (mean = 0.83%), and MS is diagnosed in 0.52-3.20% (mean = 1.30%) of patients with uveitis. The condition is most frequent among middle-aged women. Patients usually complain of floaters and/or blurred vision, with bilateral intermediate uveitis (with retinal vasculitis) as the most frequent ophthalmological finding. Both MS and intermediate uveitis are associated with HLA-DRB1*15:01 and IL-2RA gene polymorphism rs2104286 A > G, suggesting a common genetic background. T cells, and possibly B cells, play an important role in both autoimmune disorders. Multiple sclerosis (MS)-related uveitis is classically treated as non-infectious uveitis, with corticosteroids as the first treatment step. Other treatments include immunosuppressants, cryotherapy, laser photocoagulation and vitrectomy. These treatment options have a limited, if any, effect on the course of MS and can be complicated by side-effects. As treatment strategies for MS have increased in the last decade, it would be interesting to evaluate the efficacy of these new treatments during the course of uveitis. Moreover, the correlation between retinal periphlebitis and MS could be established more accurately with the recently developed techniques of wide-field fluorescein angiography in a large cohort of MS patients.

CONCLUSION

MS-associated uveitis is a rare, highly discussed pathology about which much is still unknown. Large epidemiological studies and extrapolation of new MS treatments to this condition are warranted.

Astrocyte-microglia interaction drives evolving neuromyelitis optica lesion

Neuromyelitis optica (NMO) is a severe inflammatory autoimmune CNS disorder triggered by binding of an IgG autoantibody to the aquaporin 4 (AQP4) water channel on astrocytes. Activation of cytolytic complement has been implicated as the major effector of tissue destruction that secondarily involves myelin. We investigated early precytolytic events in the evolving pathophysiology of NMO in mice by continuously infusing IgG (NMO patient serum-derived or AQP4-specific mouse monoclonal), without exogenous complement, into the spinal subarachnoid space. Motor impairment and sublytic NMO-compatible immunopathology were IgG dose dependent, AQP4 dependent, and, unexpectedly, microglia dependent. In vivo spinal cord imaging revealed a striking physical interaction between microglia and astrocytes that required signaling from astrocytes by the C3a fragment of their upregulated complement C3 protein. Astrocytes remained viable but lost AQP4. Previously unappreciated crosstalk between astrocytes and microglia involving early-activated CNS-intrinsic complement components and microglial C3a receptor signaling appears to be a critical driver of the precytolytic phase in the evolving NMO lesion, including initial motor impairment. Our results indicate that microglia merit consideration as a potential target for NMO therapeutic intervention.

Intermediate uveitis associated with MS: Diagnosis, clinical features, pathogenic mechanisms, and recommendations for management

Uveitis is a major cause of visual impairment and blindness among working-age adults, accounting for 10% of legal blindness in the United States. Among people with MS, the prevalence of uveitis is 10 times higher than among the general population, and because MS and uveitis share similar genetic risk factors and immunologic effector pathways, it is not clear whether uveitis is one of the manifestations of MS or a coincident disorder. This uncertainty raises several diagnostic and management issues for clinicians who look after these patients, particularly with regard to recognizing visual symptoms resulting from demyelination, intraocular inflammation, or the visual complications of disease modifying drugs for MS, e.g., fingolimod. Likewise, management decisions regarding patients with uveitis are influenced by the risk of precipitating or exacerbating episodes of demyelination, e.g., following anti-tumor necrosis factor biologic therapy, and other neurologic complications of immunosuppressive treatments for uveitis. In this review, we explore the similarities in the pathophysiology, clinical features, and treatment of patients with uveitis and MS. Based on the latest evidence, we make a set of recommendations to help guide neurologists and ophthalmologists to best manage patients affected by both conditions.

Animal models of multiple sclerosis: Focus on experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a chronic, progressive disorder of the central nervous system (CNS) that affects more than two million people worldwide. Several animal models resemble MS pathology; the most employed are experimental autoimmune encephalomyelitis (EAE) and toxin- and/or virus-induced demyelination. In this review we will summarize our knowledge on the utility of different animal models in MS research. Although animal models cannot replicate the complexity and heterogeneity of the MS pathology, they have proved to be useful for the development of several drugs approved for treatment of MS patients. This review focuses on EAE because it represents both clinical and pathological features of MS. During the past decades, EAE has been effective in illuminating various pathological processes that occur during MS, including inflammation, CNS penetration, demyelination, axonopathy, and neuron loss mediated by immune cells.

Lewis Rat Model of Experimental Autoimmune Encephalomyelitis

In this unit, we describe in detail the most common methods used to break immunological tolerance for central myelin antigens and induce experimental autoimmune encephalomyelitis (EAE) in Lewis rats as an animal model of multiple sclerosis. The resulting disease course ranges from an acute monophasic disease to a chronic relapsing or chronic progressive course, which strongly resembles the human disease. These models enable the study of cellular and humoral autoimmunity against major antigenic epitopes of the myelin basic protein, myelin oligodendrocyte glycoprotein, or proteolipid protein. We provide an overview of common immunization protocols for induction of active and passive EAE, assessment and analysis of clinical score, preparation and purification of myelin basic protein, and derivation of neuroantigen-specific rat T cell lines. Finally, we describe the major clinical characteristics of these models. © 2017 by John Wiley & Sons, Inc.

Immune Regulation of Antibody Access to Neuronal Tissues

This review highlights recent advances in how the innate and adaptive immune systems control the blood-brain barrier (BBB) and the blood-nerve barrier (BNB). Interferons and TAM receptors play key roles in innate immune control of the BBB. Cells of the adaptive immune system, particularly CD4⁺ T cells, take distinct routes to enter neural tissues and mediate immune surveillance. Furthermore, T cell-mediated opening of the BBB and the BNB is crucial to allow antibody access and thereby block the replication of neurotropic viruses. Such novel insights gained from basic research provide key foundations for future design of therapeutic strategies - enabling antibody access to the brain may be key to cancer immunotherapy and to the use of vaccines against neurodegenerative conditions such as Alzheimer's disease.

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.

Could Intrathymic Injection of Myelin Basic Protein Suppress Inflammatory Response After Co-culture of T Lymphocytes and BV-2 Microglia Cells?

BACKGROUND

The interaction between activated microglia and T lymphocytes can yield abundant pro-inflammatory cytokines. Our previous study proved that thymus immune tolerance could alleviate the inflammatory response. This study aimed to investigate whether intrathymic injection of myelin basic protein (MBP) in mice could suppress the inflammatory response after co-culture of T lymphocytes and BV-2 microglia cells.

METHODS

Totally, 72 male C57BL/6 mice were randomly assigned to three groups (n = 24 in each): Group A: intrathymic injection of 100 μl MBP (1 mg/ml); Group B: intrathymic injection of 100 μl phosphate-buffered saline (PBS); and Group C: sham operation group. Every eight mice in each group were sacrificed to obtain the spleen at postoperative days 3, 7, and 14, respectively. T lymphocytes those were extracted and purified from the spleens were then co-cultured with activated BV-2 microglia cells at a proportion of 1:2 in the medium containing MBP for 3 days. After identified the T lymphocytes by CD3, surface antigens of T lymphocytes (CD4, CD8, CD152, and CD154) and BV-2 microglia cells (CD45 and CD54) were detected by flow cytometry. The expressions of pro-inflammatory factors of BV-2 microglia cells (interleukin [IL]-1β, tumor necrosis factor-α [TNF-α], and inducible nitric oxide synthase [iNOS]) were detected by quantitative real-time polymerase chain reaction (PCR). One-way analysis of variance (ANOVA) and the least significant difference test were used for data analysis.

RESULTS

The levels of CD152 in Group A showed an upward trend from the 3rd to 7th day, with a downward trend from the 7th to 14th day (20.12 ± 0.71%, 30.71 ± 1.14%, 13.50 ± 0.71% at postoperative days 3, 7, and 14, respectively, P < 0.05). The levels of CD154 in Group A showed a downward trend from the 3rd to 7th day, with an upward trend from the 7th to 14th day (10.00 ± 0.23%, 5.28 ± 0.69%, 14.67 ± 2.71% at postoperative days 3, 7, and 14, respectively, P < 0.05). The ratio of CD4+/CD8 + T in Group A showed a downward trend from the 3rd to 7th day, with the minimum at postoperative day 7, then an upward trend from the 7th to 14th day (P < 0.05). Meanwhile, the levels of CD45 and CD54 in Group A were found as the same trend as the ratio of CD4+/CD8 + T (CD45: 83.39 ± 2.56%, 82.74 ± 2.09%, 87.56 ± 2.11%; CD54: 3.80 ± 0.24%, 0.94 ± 0.40%, 3.41 ± 0.33% at postoperative days 3, 7, and 14, respectively, P < 0.05). The expressions of TNF-α, IL-1β, and iNOS in Group A were significantly lower than those in Groups B and C, and the values at postoperative day 7 were the lowest compared with those at postoperative days 3 and 14 (P < 0.05). No significant difference was found between Groups B and C.

CONCLUSIONS

Intrathymic injection of MBP could suppress the immune reaction that might reduce the secondary immune injury of brain tissue induced by an inflammatory response.

Early P2X7R-related astrogliosis in autoimmune encephalomyelitis

Astrocytes are the main cells responsible for maintenance of brain homeostasis. Undisturbed action and signaling with other cells are crucial for proper functioning of the central nervous system (CNS). Dysfunctional astrocytes may determine the degree of neuronal injury and are associated with several brain pathologies, among which are multiple sclerosis (MS) and the animal model of this disease which is known as experimental autoimmune encephalomyelitis (EAE). One of the many functions of astrocytes is their response to CNS damage when they undergo reactive gliosis. Our data reveal that activation of astrocytes occurs in forebrains of immunized rats at a very early stage of EAE, well before the symptomatic phase of the disease. We have noted enhanced expression of GFAP and S100β starting from day 4 post-immunization. Temporal coincidence between the expression of astrocyte activation markers and the expression of connexin 43 and purinergic P2X7 receptor (P2X7R) was also observed. Administration of Brilliant blue G, an antagonist of P2X7R, significantly decreases astrogliosis as confirmed by immunohistochemical analysis and observation of decreased levels of GFAP and S100β. The condition of the treated animals was improved and the neurological symptoms of the disease were alleviated. With the knowledge that cerebral astroglia represent the main source of ATP and glutamate which are potentially neurotoxic substances released through P2X7R and connexin hemichannels, we suggest that astroglia may be involved in pathogenesis of MS/EAE at a very early stage through the purinergic/glutamatergic mechanisms.

Neuropathology of autoimmune encephalitides

In recent years a large number of antibody-associated or antibody-defined encephalitides have been discovered. These conditions are often referred to as autoimmune encephalitides. The clinical features include prominent epileptic seizures, cognitive and psychiatric disturbance. These encephalitides can be divided in those with antibodies against intracellular antigens and those with antibodies against surface antigens. The discovery of new antibodies against targets on the surface of neurons is especially interesting since patients with such antibodies can be successfully treated immunologically. This chapter focuses on the pathology and the pathogenetic mechanisms involved in these encephalitides and discusses some of the questions that are raised in this exciting new field. It is important to realise, however, that because of the use of antibodies to diagnose the patients, and their improvement with treatment, there are relatively few biopsy or postmortem reports, limiting the neuropathological data and conclusions that can be drawn. For this reason we especially focus on the most frequent autoimmune encephalitides, those with antibodies to the NMDA receptor and with antibodies to the known protein components of the VGKC complex. Analysis of these encephalitides show completely different pathogenic mechanisms. In VGKC complex encephalitis, antibodies seem to bind to their target and activate complement, leading to destruction and loss of neurons. On the other hand, in NMDAR encephalitis, complement activation and neuronal degeneration seems to be largely absent. Instead, binding of antibodies leads to a decrease of NMDA receptors resulting in a hypofunction. This hypofunction offers an explanation for some of the clinical features such as psychosis and episodic memory impairment, but not for the frequent seizures. Thus, additional analysis of the few human brain specimens present and the use of specific animal models are needed to further understand the effects of these antibodies in autoimmune encephalitides.

Methods for Testing Immunological Factors

Hypersensitivity reactions can be elicited by various factors: either immunologically induced, i.e., allergic reactions to natural or synthetic compounds mediated by IgE, or non-immunologically induced, i.e., activation of mediator release from cells through direct contact, without the induction of, or the mediation through immune responses. Mediators responsible for hypersensitivity reactions are released from mast cells. An important preformed mediator of allergic reactions found in these cells is histamine. Specific allergens or the calcium ionophore 48/80 induce release of histamine from mast cells. The histamine concentration can be determined with the o-phthalaldehyde reaction.

Role of T cell-glial cell interactions in creating and amplifying central nervous system inflammation and multiple sclerosis disease symptoms

Multiple Sclerosis (MS) is an inflammatory disease of the Central Nervous System (CNS) that causes the demyelination of nerve cells and destroys oligodendrocytes, neurons and axons. Historically, MS has been thought of as a T cell-mediated autoimmune disease of CNS white matter. However, recent studies have identified gray matter lesions in MS patients, suggesting that CNS antigens other than myelin proteins may be involved during the MS disease process. We have recently found that T cells targeting astrocyte-specific antigens can drive unique aspects of inflammatory CNS autoimmunity, including the targeting of gray matter and white matter of the brain and inducing heterogeneous clinical disease courses. In addition to being a target of T cells, astrocytes play a critical role in propagating the inflammatory response within the CNS induced NF-κB signaling. Here, we will discuss the pathophysiology of CNS inflammation mediated by T cell—glial cell interactions and its contributions to CNS autoimmunity.

Characterization of the autoimmune response against the nerve tissue S100β in patients with type 1 diabetes

Type 1 diabetes results from destruction of insulin-producing beta cells in pancreatic islets and is characterized by islet cell autoimmunity. Autoreactivity against non-beta cell-specific antigens has also been reported, including targeting of the calcium-binding protein S100β. In preclinical models, reactivity of this type is a key component of the early development of insulitis. To examine the nature of this response in type 1 diabetes, we identified naturally processed and presented peptide epitopes derived from S100β, determined their affinity for the human leucocyte antigen (HLA)-DRB1*04:01 molecule and studied T cell responses in patients, together with healthy donors. We found that S100β reactivity, characterized by interferon (IFN)-γ secretion, is a characteristic of type 1 diabetes of varying duration. Our results confirm S100β as a target of the cellular autoimmune response in type 1 diabetes with the identification of new peptide epitopes targeted during the development of the disease, and support the preclinical findings that autoreactivity against non-beta cell-specific autoantigens may have a role in type 1 diabetes pathogenesis.

Autoimmune disease in the brain--how to spot the culprits and how to keep them in check

Current concepts attribute an early and central role for auto-aggressive, myelin-specific T-lymphocytes in the pathogenesis of multiple sclerosis. This view emerged from immunological and pathological findings in experimental autoimmune encephalitis, an animal model characterised by pathological lesions closely resembling the ones found in multiple sclerosis. Furthermore, therapeutic strategies targeting the functions of these encephalitogenic T cells which attenuate their pathogenicity such as glatiramer acetate or anti-VLA4 antibody treatments represent proven approaches in multiple sclerosis. Nonetheless, all therapies evaluated to date either insufficiently dampen down inflammation or completely block immune processes. For this reason, there is a need to identify new therapeutic targets. We have employed live intravital two-photon microscopy to learn more about the behaviour of T cells during the preclinical phase of EAE, when T cells acquire the properties required to invade their target organ. Furthermore, we were able to identify an unexpected locomotive behaviour of T cells at the blood-brain barrier, which occurs immediately before diapedesis and the induction of paralytic disease. Such studies might open new avenues for the treatment of CNS autoimmune diseases. Multiple sclerosis is considered to be an autoimmune disease in which self-reactive T cells enter the central nervous system (CNS) and create an inflammatory milieu that destroys myelin and neurons. Immunomodulatory strategies for the treatment of multiple sclerosis target this process by attempting to inactivate these auto-aggressive T cells. However, so far, these strategies have failed to extinguish disease activity completely. For this reason, there is a need to understand in more detail the mechanisms by which T cells become encephalitogenic, how they enter the nervous system, and what the signals are that guide them along this path. If these processes could be better understood, it may be possible to design more effective and specific therapies for multiple sclerosis. This article will give a brief overview about our recent findings obtained using intravital imaging of autoaggressive effector T cells in an experimental model of multiple sclerosis. This new technological approach might help to fill some gaps in the understanding of autoimmune pathogenesis of multiple sclerosis.

A study of experimental autoimmune encephalomyelitis in dogs as a disease model for canine necrotizing encephalitis

In the present study, the use of dogs with experimental autoimmune encephalomyelitis (EAE) as a disease model for necrotizing encephalitis (NE) was assessed. Twelve healthy dogs were included in this study. Canine forebrain tissues (8 g), including white and grey matter, were homogenized with 4 mL of phosphate-buffered saline for 5 min in an ice bath. The suspension was emulsified with the same volume of Freund's complete adjuvant containing 1 mg/mL of killed Mycobacterium tuberculosis H37Ra. Under sedation, each dog was injected subcutaneously with canine brain homogenate at four sites: two in the inguinal and two in the axillary regions. A second injection (booster) was administered to all the dogs using the same procedure 7 days after the first injection. Clinical assessment, magnetic resonance imaging, cerebrospinal fluid analyses, necropsies, and histopathological and immunohistochemical examinations were performed for the dogs with EAE. Out of the 12 animals, seven (58%) developed clinically manifest EAE at various times after immunization. Characteristics of canine EAE models were very similar to canine NE, suggesting that canine EAE can be a disease model for NE in dogs.

The molecular basis of neurodegeneration in multiple sclerosis

Studies aimed to elucidate the pathogenesis of the disease and to find new therapeutic options for multiple sclerosis (MS) patients heavily rely on experimental autoimmune encephalomyelitis (EAE) as a suitable experimental model. This strategy has been highly successful for the inflammatory component of the disease, but had so far little success in the development of neuroprotective therapies, which are also effective in the progressive stage of the disease. Here we discuss opportunities and limitations of EAE models for MS research and provide an overview on the complex mechanisms leading to demyelination and neurodegeneration in this disease. We suggest that the underlying mechanisms involve adaptive and innate immunity. However, mitochondrial injury, resulting in energy failure, is a key element of neurodegeneration in MS and is apparently driven by radical production in activated microglia.

Pathogenic T cell responses against aquaporin 4

Inflammatory lesions in the central nervous system of patients with neuromyelitis optica are characterized by infiltration of T cells and deposition of aquaporin-4-specific antibodies and complement on astrocytes at the glia limitans. Although the contribution of aquaporin-4-specific autoantibodies to the disease process has been recently elucidated, a potential role of aquaporin-4-specific T cells in lesion formation is unresolved. To address this issue, we raised aquaporin-4-specific T cell lines in Lewis rats and characterized their pathogenic potential in the presence and absence of aquaporin-4-specific autoantibodies of neuromyelitis optica patients. We show that aquaporin-4-specific T cells induce brain inflammation with particular targeting of the astrocytic glia limitans and permit the entry of pathogenic anti-aquaporin-4-specific antibodies to induce NMO-like lesions in spinal cord and brain. In addition, transfer of aquaporin-4-specific T cells provoked mild (subclinical) myositis and interstitial nephritis. We further show that the expression of the conformational epitope, recognized by NMO patient-derived aquaporin-4-specific antibodies is induced in kidney cells by the pro-inflammatory cytokine gamma-interferon. Our data provide further support for the view that NMO lesions may be induced by a complex interplay of T cell mediated and humoral immune responses against aquaporin-4.

Immunological basis for the development of tissue inflammation and organ-specific autoimmunity in animal models of multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is an animal model for multiple sclerosis (MS) that has shaped our understanding of autoimmune tissue inflammation in the central nervous system (CNS). Major therapeutic approaches to MS have been first validated in EAE. Nevertheless, EAE in all its modifications is not able to recapitulate the full range of clinical and histopathogenic aspects of MS. Furthermore, autoimmune reactions in EAE-prone rodent strains and MS patients may differ in terms of the relative involvement of various subsets of immune cells. However, the role of specific molecules that play a role in skewing the immune response towards pathogenic autoreactivity is very similar in mice and humans. Thus, in this chapter, we will focus on the identification of a novel subset of inflammatory T cells, called Th17 cells, in EAE and their interplay with other immune cells including protective regulatory T cells (T-regs). It is likely that the discovery of Th17 cells and their relationship with T-regs will change our understanding of organ-specific autoimmune diseases in the years to come.

Myelin-specific T cells also recognize neuronal autoantigen in a transgenic mouse model of multiple sclerosis

We describe here the paradoxical development of spontaneous experimental autoimmune encephalomyelitis (EAE) in transgenic mice expressing a myelin oligodendrocyte glycoprotein (MOG)-specific T cell antigen receptor (TCR) in the absence of MOG. We report that in Mog-deficient mice (Mog-/-), the autoimmune response by transgenic T cells is redirected to a neuronal cytoskeletal self antigen, neurofilament-M (NF-M). Although components of radically different protein classes, the cross-reacting major histocompatibility complex I-Ab-restricted epitope sequences of MOG35-55 and NF-M18-30 share essential TCR contact positions. This pattern of cross-reaction is not specific to the transgenic TCR but is also commonly seen in MOG35-55-I-Ab-reactive T cells. We propose that in the C57BL/6 mouse, MOG and NF-M response components add up to overcome the general resistance of this strain to experimental induction of autoimmunity. Similar cumulative responses against more than one autoantigen may have a role in spontaneously developing human autoimmune diseases.

Experimental autoimmune encephalomyelitis in the rat

There are several diverse rat models of experimental autoimmune encephalomyelitis (EAE) that can be used to investigate the pathogenesis and regulation of autoimmunity against CNS myelin. The disease course of these models ranges from an acute monophasic disease with limited demyelination to a chronic relapsing or chronic progressive course marked by severe demyelination. These models enable the study of encephalitogenic T cells and demyelinating antibody specific for major neuroantigens such as myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG), or proteolipid protein (PLP), among other important CNS autoantigens. Overall, this unit provides an overview of common methods for induction of active and passive EAE, assessment and analysis of clinical disease, preparation and purification of myelin basic protein, and derivation of neuroantigen-specific rat T cell lines. This unit also provides a brief discussion of the basic characteristics of these models.

Animal models of multiple sclerosis

Since its first description, experimental autoimmune encephalomyelitis, originally designated experimental allergic encephalitis (EAE), has been proposed as animal model to investigate pathogenetic hypotheses and test new treatments in the field of central nervous system inflammation and demyelination, which has become, in the last 30 years, the most popular animal model of multiple sclerosis (MS). This experimental disease can be obtained in all mammals tested so far, including nonhuman primates, allowing very advanced preclinical studies. Its appropriate use has led to the development of the most recent treatments approved for MS, also demonstrating its predictive value when properly handled. Some of the most exciting experiments validating the use of neural precursor cells (NPCs) as a potential therapeutic option in CNS inflammation have been performed in this model. We review here the most relevant immunological features of EAE in the different animal species and strains, and describe detailed protocols to obtain the three most common clinical courses of EAE in mice, with the hope to provide both cultural and practical basis for the use of this fascinating animal model.

The origin and application of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a model of the neuroimmune system responding to priming with central nervous system (CNS)-restricted antigens. It is an excellent model of post-vaccinal encephalitis and a useful model of many aspects of multiple sclerosis. EAE has been established in numerous species and is induced by priming with a large number of CNS-derived antigens. As a consequence, the pathogenesis, pathology and clinical signs vary significantly between experimental protocols. As I describe in this Timeline article, the reductionist approach taken in some lines of investigation of EAE resulted in a reliance on results obtained under a narrow range of conditions. Although such studies made important contributions to our molecular understanding of inflammation, T-cell activation, and MHC restriction, they did not advance as effectively our knowledge of the polyantigenic responses that usually occur in CNS immunopathology and autoimmunity.

Enolase and arrestin are novel nonmyelin autoantigens in multiple sclerosis

INTRODUCTION

Although myelin autoimmunity is known to be a major factor in the pathogenesis of multiple sclerosis (MS), the role of nonmyelin antigens is less clear. Given the complexity of this disease, it is possible that autoimmunity against nonmyelin antigens also has a pathogenic role. Autoantibodies against enolase and arrestin have previously been reported in MS patients. The T-cell response to these antigens, however, has not been established.

METHODS

Thirty-five patients with MS were recruited, along with thirty-five healthy controls. T-cell proliferative responses against non-neuronal enolase, neuron-specific enolase (NSE), retinal arrestin, beta-arrestin, and myelin basic protein were determined.

RESULTS

MS patients had a greater prevalence of positive T-cell proliferative responses to NSE, retinal arrestin, and beta-arrestin than healthy controls (p<0.0001). The proliferative response against NSE, retinal arrestin, and beta-arrestin correlated with the response against myelin basic protein (p < or = 0.004). Furthermore, the proliferative response against retinal arrestin was correlated to beta-arrestin (p<0.0001), whereas there was no such correlation between non-neuronal enolase and NSE (p = 0.23).

DISCUSSION

There is accumulating evidence to suggest that the pathogenesis of MS involves more than just myelin autoimmunity/destruction. Autoimmunity against nonmyelin antigens may be a component of this myriad of immunopathological events. NSE, retinal arrestin, and beta-arrestin are novel nonmyelin autoantigens that deserve further investigation in this respect. Autoimmunity against these antigens may be linked to neurodegeneration, defective remyelination, and predisposition to uveitis in multiple sclerosis. Further investigation of the role of these antigens in MS is warranted.

Cortical, subcortical and spinal alterations in neuroimmunological diseases

Inflammatory and immune mediated diseases of the nervous system are reflected by a broad spectrum of different clinical deficits. The reason for this is that inflammation may affect any part of the nervous system. Nevertheless, certain regions in the brain and spinal cord are more frequently affected than others. The topographical distribution of inflammatory lesions in the nervous system depends upon a large variety of different factors, which are different in the various infectious and autoimmune diseases. Aim of this short review is to discuss the main factors determining lesional topography in brain inflammation and to illustrate these patterns of tissue injury with clinical examples.

Polyreactive myelin oligodendrocyte glycoprotein antibodies: Implications for systemic autoimmunity in progressive experimental autoimmune encephalomyelitis

Two myelin oligodendrocyte glycoprotein (MOG92-106) monoclonal antibodies (mAbs) were produced from an A.SW mouse with progressive experimental autoimmune encephalomyelitis. Polyreactivity/specificity of the mAbs was demonstrated by ELISA. Functionality and a potential role in pathogenesis of systemic autoimmunity were demonstrated in vitro in a lymphocytotoxicity assay and in vivo upon injection into naïve mice. Injection of MOG mAb producing hybridomas into naïve mice resulted in immunoglobulin deposition in kidneys and liver. This model will be useful in determining whether transitional forms between CNS (organ)-specific and systemic autoimmune diseases exist, and whether progressive multiple sclerosis has features of a systemic autoimmune disease.

Enolase autoantibodies and retinal function in multiple sclerosis patients

BACKGROUND

Electroretinographic (ERG) abnormalities have been reported in multiple sclerosis (MS), as well as the presence of circulating antiretinal antibodies. We and others have reported cases of impaired vision and diminished ERGs in MS patients with alpha-enolase autoantibodies. Anti-enolase antibodies have been implicated in autoimmune retinopathy. We performed this study to further explore the relationship between antiretinal antibodies and ERG changes in patients with MS.

METHODS

Patients with clinically definite MS and normal visual acuity were recruited for this study, along with healthy controls. All patients and controls had ERG testing done according to ISCEV standards. Patient and control sera were analyzed for the presence of antiretinal antibodies using Western blot and ELISA techniques, and HLA class II typing was performed using polymerase chain reaction.

RESULTS

We found a statistically significant difference between MS patients and controls in the rod-cone b-wave implicit time (p < 0.005). We found autoantibodies against alpha-enolase in 38% of MS patients and 11% of controls (p < 0.02). There was no statistically significant difference between ERG parameters of MS patients with alpha-enolase autoantibodies compared to those without alpha-enolase antibodies. Furthermore, the presence of alpha-enolase did not associate with a particular HLA haplotype.

CONCLUSIONS

Factors affecting the retina other than alpha-enolase antibodies may account for the delayed rod-cone b-wave implicit times observed in MS patients in this study. Anti-enolase antibodies are likely an epiphenomenon of autoimmune disease, and are not causing retinopathy in MS patients with normal visual acuity. However, the possibility of rare cases of patients with pathogenic alpha-enolase autoantibodies can not be excluded. The pathogenic contribution of these antibodies in MS patients with visual impairment deserves further investigation.

Electroretinographic abnormalities in multiple sclerosis: possible role for retinal autoantibodies

BACKGROUND

Multiple sclerosis (MS) has been associated with inflammation of the uveal tract, suggesting an immunological link between the uvea and central nervous system (CNS) in this disease. The retina is embryologically derived from the CNS, and it is conceivable that retinal antigens may also be recognized by the immune system in MS. Electroretinographic abnormalities, as well as retinal autoantibodies, have previously been described in MS. We performed this study to further explore the possibility of retinal autoimmunity in MS.

METHODS

Thirty-four patients with clinically definite MS and thirty-seven healthy controls were recruited. All patients and controls had standard electroretinographic (ERG) testing done, as well as a brightflash ERG protocol to isolate rod photoreceptor function. Patient and control sera were analyzed for the presence of antiretinal antibodies using Western blot techniques.

RESULTS

We found statistically significant differences between MS patients and controls in four ERG parameters. In the MS group, implicit times of the rod-cone b-wave response, cone b-wave response, and rod photoreceptor response were increased. The amplitudes of the photopic oscillatory potentials were reduced in the MS group. Patients with the highest titres of retinal autoantibodies had delayed rod-cone b-wave implicit times and diminished photopic oscillatory potential amplitudes.

CONCLUSIONS

We report ERG evidence of retinal dysfunction in patients with MS. We also report the first use of the brightflash ERG protocol in MS, which demonstrated rod photoreceptor dysfunction. Patients with the highest antiretinal antibody titres had abnormal ERG recordings. Retinal autoimmunity is a possible explanation for these observed ERG abnormalities in MS patients.

Breaking ignorance: the case of the brain

Immunological self-tolerance is maintained through diverse mechanisms, including deletion of autoreactive immune cells following confrontation with autoantigen in the thymus or in the periphery and active suppression by regulatory cells. A third way to prevent autoimmunity is by hiding self tissues behind a tissue barrier impermeable for circulating immune cells. The latter mechanism has been held responsible for self-tolerance within the nervous tissue. Indeed, the nervous tissues enjoy a conditionally privileged immune status: they are normally unreachable for self-reactive T and B cells, they lack lymphatic drainage, and they are deficient in local antigen-presenting cells. Yet the immune system is by no means fully ignorant of the nervous structures. An ever-growing number of brain specific autoantigens is expressed within the thymus, which ensures an early confrontation with the unfolding T cell repertoire, and there is evidence that B cells also contact CNS-like structures outside of the brain. Then pathological processes such as neurodegeneration commonly lift the brain's immune privilege, shifting the local milieus from immune-hostile to immune-friendly. Finally, brain-reactive T cells, which abound in the healthy immune repertoire, but remain innocuous throughout life, can be activated and gain access to their target tissues. On their way, they take an ordered migration through peripheral lymphoid tissues and blood circulation, and undergo a profound reprogramming of their gene expression profile, which renders them fit to enter the nervous system and to interact with local cellule elements.

Spinal cord gray matter demyelination in multiple sclerosis-a novel pattern of residual plaque morphology

The extent and pattern of gray matter (GM) demyelination in the spinal cord in multiple sclerosis (MS) has not been examined in detail. Human autopsy material was obtained from 36 MS cases and 12 controls. Transverse sections were taken from five levels of the spinal cord (upper cervical, lower cervical, upper thoracic, lower thoracic and lumbar levels) and the extent of GM and white matter (WM) demyelination evaluated using proteolipid protein immunohistochemistry (IHC). The proportion of the GM that was demyelinated (33%) was significantly greater than the proportion of demyelinated WM (20%) (P < 0.0001). Similarly, demyelination was more extensive in the GM than in the WM at each of the five cord levels. The extent of GM demyelination was not significantly different between the five cord levels while WM demyelination was greatest at the upper cervical level. Morphologically, the borders of a proportion of the GM plaques show a strict respect for the GM/WM boundary. We demonstrate that extensive demyelination occurs in the GM of the spinal cord in MS. Myelin protein IHC reveals a novel pattern of residual plaque morphology challenging previous work suggesting that MS plaques display a total disregard for anatomical boundaries.

How special is a pathogenic CNS autoantigen? Immunization to many CNS self-antigens does not induce autoimmune disease

Recent work has shown neuro-protective effects of immunization with self-CNS antigens in animal models of Alzheimer's disease, prion diseases and CNS trauma. The major concern with such an approach is the inadvertent induction of autoimmune disease. The present work was initiated to study the incidence of autoimmune disease associated with the induction of T cell autoimmunity to a panel of 70 peptides derived from CNS proteins. Using a MHC class II motif developed in our laboratory to identify candidate peptides, we selected 70 peptides from 40 different CNS proteins. The proteins were selected randomly and represented various biological functions (surface receptors, structural proteins, synaptic proteins, neurodegeneration related proteins). Each peptide was emulsified in CFA and injected to autoimmune-prone Lewis rats. Immunogenicity was verified by peptide-specific LN cell proliferation. In addition, T cell lines were generated for many peptides and tested by adoptive transfer. Except for the previously reported pathogenicity of beta-synuclein, none of the 68 peptides from 39 proteins was found to induce CNS disease in recipient rats. These findings underscore the efficiency of immunological regulation in preventing CNS autoimmune disease, and confirm the uniqueness of the well-known pathogenic CNS auto-antigens.

Experimental allergic encephalomyelitis: a misleading model of multiple sclerosis

Despite many years of intensive research, multiple sclerosis (MS) defies understanding and treatment remains suboptimal. The prevailing hypothesis is that MS is immune mediated and that experimental allergic encephalomyelitis (EAE) is a suitable model to elucidate pathogenesis and devise therapy. This review examines critically the validity that EAE is an adequate and useful animal model of MS and finds credible evidence lacking. EAE represents more a model of acute central nervous system inflammation than the counterpart of MS. We propose to reconsider the utilization of EAE, especially when this model is used to define therapy. This will also force us to examine MS without the restraints imposed by EAE, as to what it is, rather than what it looks like.

Immunology of multiple sclerosis

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

Chronic recurrent autoimmune uveitis with progressive photoreceptor damage induced in rats by transfer of IRBP-specific T cells

Recurrent uveitis is a common cause of vision blindness. Using a rat model of chronic recurrent uveitis, we examined the relationship between clinical expression, pathological changes, and the heterogeneity of the disease. Chronic recurrent uveitis was induced by adoptive transfer of interphotoreceptor retinoid-binding protein (IRBP)-specific T cells in a total of more than 60 Lewis rats. In about 75% of cases recurrent uveitis was pathologically a chronic and progressive disease. The major pathological changes included the gradual loss of photoreceptor cells. However, disease progression did not always parallel the severity of ocular inflammation and clinical recurrent disease, with about a quarter showing no pathological damage in the eye.

The activation status of neuroantigen-specific T cells in the target organ determines the clinical outcome of autoimmune encephalomyelitis

The clinical picture of experimental autoimmune encephalomyelitis (EAE) is critically dependent on the nature of the target autoantigen and the genetic background of the experimental animals. Potentially lethal EAE is mediated by myelin basic protein (MBP)–specific T cells in Lewis rats, whereas transfer of S100β- or myelin oligodendrocyte glycoprotein (MOG)–specific T cells causes intense inflammatory response in the central nervous system (CNS) with minimal disease. However, in Dark Agouti rats, the pathogenicity of MOG-specific T cells resembles the one of MBP-specific T cells in the Lewis rat. Using retrovirally transduced green fluorescent T cells, we now report that differential disease activity reflects different levels of autoreactive effector T cell activation in their target tissue. Irrespective of their pathogenicity, the migratory activity, gene expression patterns, and immigration of green fluorescent protein⁺ T cells into the CNS were similar. However, exclusively highly pathogenic T cells were significantly reactivated within the CNS. Without local effector T cell activation, production of monocyte chemoattractants was insufficient to initiate and propagate a full inflammatory response. Low-level reactivation of weakly pathogenic T cells was not due to anergy because these cells could be activated by specific antigen in situ as well as after isolation ex vivo.

Multiple sclerosis: etiological mechanisms and future directions

Multiple sclerosis (MS) is a complex human autoimmune-type disease with a predominantly unknown etiology. Immunologic destruction of myelin basic protein (MBP) throughout the nervous system is the major pathology of multiple sclerosis. This review will attempt to update new information about basic mechanisms and therapeutic management of the disease. The significance of the structure of MBP is discussed with respect to the contribution of such structures to the disease process. A number of MBP peptides that serve as the immunodominant antigens in MS patients have been identified. These peptides have been studied in animal models for their antigenic characteristics and ability to induce disease. Evidence for genetic contributions is reviewed with multigenerational twin studies providing the best evidence for susceptible haplotypes. The role of microorganisms/viruses and environmental agents are discussed as potential etiological factors but are now thought to be of minor importance to the primary causal development of the disease. Of major consideration are immunological mechanisms that contribute to the development of autoimmunity. In particular, antigen expression, cytokine and leukocyte interactions, and regulatory T-cells are discussed. Particular attention is given to regulatory T-cells (Treg), which help balance/modulate other T-cells such as Th1 and Th2 cells, and how such Treg regulate autoimmunity is addressed. The importance of the role of Tregs is exemplified by the demonstration that administration of oral antigens can induce specific Tregs that counteract experimental autoimmune encephalomyelitis in animal models. The significance of animal studies to human multiple sclerosis is discussed. A potential role for natural antibodies and innate immune mechanisms to help provide resistance to disease development is also reviewed. Finally, a variety of therapeutic agents that have been and continue to be utilized for multiple sclerosis is reviewed. Trials with oral antigens, such as glatirmer acetate (copolymer 1) especially in combination with interferon-beta, have shown promise. Antibody therapy and bone marrow transplantation are also briefly discussed.

Molecular pathogenesis of neuroinflammation

The past few years have seen significant progress towards understanding the mechanisms of immune surveillance and inflammation in the nervous system. In this review, the milestones of scientific discovery in this field are discussed, and the strengths and limitations of the different ways of examining the molecular pathogenesis of neuro-inflammation examined. The review is limited to the inflammatory reactions of the central nervous system that occur in multiple sclerosis and experimental autoimmune encephalomyelitis.

The pathology and pathogenesis of retinal vasculitis

Retinal vasculitis is a rare, but potentially blinding intraocular inflammatory condition with diverse aetiology. Although commonly idiopathic, it has a strong association with systemic inflammatory diseases known to involve other areas of the central nervous system, most notably Behcet's disease, sarcoidosis, systemic lupus erythematosis and multiple sclerosis. This article describes the clinicopathologic features of retinal vasculitis and its visually damaging sequelae, reviewing available human histopathologic studies and work with experimental models to discuss the pathogenesis and immunopathology. Evidence indicates that noninfective retinal vasculitis is an autoimmune condition that may be induced by antecedent infection with microbes cross-reacting with putative autoantigens, influenced by genetic susceptibility of both HLA associations and cytokine polymorphisms. The growing understanding of the cellular mechanisms involved in the effector immune response is already providing a rationale for more specific therapeutic approaches.

Longitudinal study of chemokine receptor expression on peripheral lymphocytes in multiple sclerosis: CXCR3 upregulation is associated with relapse

The interaction between chemokines and their receptors leads to selective recruitment of cells to foci of inflammation. Cross-sectional studies have reported significantly different expression of chemokine receptors CXCR3, CCR5 and CCR2 on peripheral blood lymphocytes in multiple sclerosis (MS) compared with controls. Cells expressing these receptors are likely to play a pathogenic role as suggested by studies of experimental autoimmune encephalomyelitis. Also, immunogenetic studies of nonfunctional CCR5 receptors in MS patients, due to 32delta deletion, demonstrated a delay in time to next relapse. The aims of this study were to detect any changes in the serial expression of chemokine receptors CCR2, CCR3, CCR5 and CXCR3 on peripheral blood CD4+ lymphocytes from patients with MS and to correlate the changes with relapses. Upregulation of CXCR3 expression on peripheral blood CD4+ lymphocytes was associated with all relapses and CCR5 expression was significantly affected with all relapses. Clinical recovery, with or without intravenous methylprednisolone treatment, coincided with the return of CXCR3 towards baseline in all but one case. Fluctuation in the expression of CXCR3 and CCR5 was also significantly greater in clinically stable patients with MS compared with controls, which may be due to subclinical disease activity. These findings provide further support for the view that CXCR3 and CCR5 antagonists could have a therapeutic value in MS.

Clinical and experimental studies of autoimmune inner ear disease

Otolaryngologists have long sought to identify causes of sensorineural hearing loss that could be reversed by medical treatment. An increasing amount of clinical and experimental evidence indicates that this postulated entity is related to autoimmune inner ear disease. Because of the lack of well-defined detection methods for identifying autoimmune processes within the human inner ear and the fact that it is one of the few organs of the body not amenable to diagnostic biopsy there has been great interest in developing animal models that mimic clinical entities. Different models will be presented in this paper. The results of these studies should provide sufficient evidence to establish a clear position in mainstream immunology for the entity of autoimmune inner ear disease.

Oral tolerance for treating uveitis - new hope for an old immunological mechanism

Oral tolerance induction has evolved as an attractive approach for the treatment of autoimmune uveitis. This approach is effective and generally void of the side effects associated with conventional immunosuppression. Following uptake of soluble antigen via the gut mucosa a specific systemic tolerance is generated. Experimental autoimmune diseases such as uveitis can efficiently be treated when autoantigens are fed to animals. The immunological mechanisms of oral tolerance are not well understood but are thought to involve the recognition of tolerogenic epitopes, generation of suppressor T cells and altered regulation of selected cytokines. The dose, purity of the antigen (tissue extract vs. single peptide) and concomitant treatment with cytokines were evaluated with the aim to enhance oral tolerance. Immunomodulatory drugs can abrogate oral tolerance. This requires careful evaluation with respect to therapeutic approaches in patients. The first clinical trials for treatment of uveitis with oral retinal autoantigen or an HLA-peptide crossreactive with S-Antigen show a promising therapeutic effect and confirmed the safety of this approach.

Immunization with a cannabinoid receptor type 1 peptide results in experimental allergic meningocerebellitis in the Lewis rat: A model for cell-mediated autoimmune neuropathology

Neuronal elements are increasingly suggested as primary targets of an autoimmune attack in certain neurological and neuropsychiatric diseases. Type 1 cannabinoid receptors (CB1) were selected as autoimmune targets because they are predominantly expressed on neuronal surfaces in brain and display strikingly high protein levels in striatum, hippocampus, and cerebellum. Female Lewis rats were immunized with N-terminally acetylated peptides (50 or 400 microg per rat) of the extracellular domains of the rat CB1 and killed at various time points. Subsequent evaluation using immunohistochemistry and in situ hybridization showed dense infiltration of immune cells exclusively within the cerebellum, peaking 12-16 days after immunization with the CB1 peptide containing amino acids 9-25. The infiltrates clustered in meninges and perivascular locations in molecular and granular cell layers and were also scattered throughout the CB1-rich neuropil. They consisted primarily of CD4(+) and ED1(+) cells, suggestive of cell-mediated autoimmune pathology. There were no inflammatory infiltrates elsewhere in the brain or spinal cord. The results show that neuronal elements, such as neuronal cell-surface receptors, may be recognized as antigenic targets in a cell-mediated autoimmune attack and, therefore, support the hypothesis of cell-mediated antineuronal autoimmune pathology in certain brain disorders.

Experimental autoimmune uveitides: multiple antigens, diverse diseases

Human autoimmune uveitides are diverse and complex. Animal models have been developed for studying the pathogenesis of uveitis because of the difficulties in obtaining tissues from a patient's inflamed eye for experiments. There are animal models for experimental uveitis that provoke inflammation of different tissues of the eye and represent different forms of uveitis. Since inflammatory cells can infiltrate any part of the uvea and spill over to nonuveal tissues, such as retina, various antigens have been used to induce uveitis. Most of those models that represent autoimmune forms of uveitis are induced with proteins specific for photoreceptor cells (S-antigen, IRBP, rhodopsin, recoverin, phosducin). Nonretinal antigens, including melanin-associated proteins and myelin basic protein, are also good inducers of uveitis in animals.