CD8(+) T Cells Are Required For Glatiramer Acetate Therapy in Autoimmune Demyelinating Disease

Drug repurposing for neurodegenerative diseases

Neurodegenerative diseases (NDDs) are neuronal problems that include the brain and spinal cord and result in loss of sensory and motor dysfunction. Common NDDs include Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), Multiple Sclerosis (MS), and Amyotrophic Lateral Sclerosis (ALS) etc. The occurrence of these diseases increases with age and is one of the challenging problems among elderly people. Though, several scientific research has demonstrated the key pathologies associated with NDDs still the underlying mechanisms and molecular details are not well understood and need to be explored and this poses a lack of effective treatments for NDDs. Several lines of evidence have shown that NDDs have a high prevalence and affect more than a billion individuals globally but still, researchers need to work forward in identifying the best therapeutic target for NDDs. Thus, several researchers are working in the directions to find potential therapeutic targets to alter the disease pathology and treat the diseases. Several steps have been taken to identify the early detection of the disease and drug repurposing for effective treatment of NDDs. Moreover, it is logical that current medications are being evaluated for their efficacy in treating such disorders; therefore, drug repurposing would be an efficient, safe, and cost-effective way in finding out better medication. In the current manuscript we discussed the utilization of drugs that have been repurposed for the treatment of AD, PD, HD, MS, and ALS.

Beneficial Effects of Plant Oils Supplementation on Multiple Sclerosis: A Comprehensive Review of Clinical and Experimental Studies

Multiple sclerosis disease (MS) is a 38.5 chronic neurological autoimmune disease that affects the nervous system, and its incidence is increasing globally. At present, there is no cure for this disease, and with its severity and disabling variety, it is important to search for possibilities that could help to slow its progression. It is recognized that the mechanisms of MS pathology, its development and degree of activity can be affected by dietary factors. In this review, the beneficial health effects of 10 plants oils-mainly seed oils, including pomegranate seed oil, sesame oil, acer truncatum bunge seed oil, hemp seeds oil, evening primrose seed oil, coconut oil, walnut oil, essential oil from Pterodon emarginatus seeds, flaxseed oil and olive oil-on MS are discussed. The literature data indicate that plant oils could be effective for the treatment of MS and its related symptoms primarily through reducing inflammation, promoting remyelination, immunomodulation and inhibiting oxidative stress. Plant oils may potentially reduce MS progression. Longitudinal research including a larger sample size with a longer duration is essential to confirm the findings from the selected plant oils. Moreover, new plant oils should be studied for their potential MS benefit.

Prophylactic Glatiramer Acetate Treatment Positively Attenuates Spontaneous Opticospinal Encephalomyelitis

Background: Glatiramer acetate (GA) is a well-established treatment option for patients with clinically isolated syndrome and relapsing-remitting multiple sclerosis (MS) with few side effects. The double transgenic mouse model spontaneous opticospinal encephalomyelitis (OSE), based on recombinant myelin oligodendrocyte glycoprotein_35-55 reactive T and B cells, mimicks features of chronic inflammation and degeneration in MS and related disorders. Here, we investigated the effects of prophylactic GA treatment on the clinical course, histological alterations and peripheral immune cells in OSE. Objective: To investigate the effects of prophylactic glatiramer acetate (GA) treatment in a mouse model of spontaneous opticospinal encephalomyelitis (OSE). Methods: OSE mice with a postnatal age of 21 to 28 days without signs of encephalomyelitis were treated once daily either with 150 µg GA or vehicle intraperitoneally (i. p.). The animals were scored daily regarding clinical signs and weight. The animals were sacrificed after 30 days of treatment or after having reached a score of 7.0 due to animal care guidelines. We performed immunohistochemistry of spinal cord sections and flow cytometry analysis of immune cells. Results: Preventive treatment with 150 µg GA i. p. once daily significantly reduced clinical disease progression with a mean score of 3.9 ± 1.0 compared to 6.2 ± 0.7 in control animals (p < 0.01) after 30 d in accordance with positive effects on weight (p < 0.001). The immunohistochemistry showed that general inflammation, demyelination or CD11c⁺ dendritic cell infiltration did not differ. There was, however, a modest reduction of the Iba1⁺ area (p < 0.05) and F4/80⁺ area upon GA treatment (p < 0.05). The immune cell composition of secondary lymphoid organs showed a trend towards an upregulation of regulatory T cells, which lacked significance. Conclusions: Preventive treatment with GA reduces disease progression in OSE in line with modest effects on microglia/macrophages. Due to the lack of established prophylactic treatment options for chronic autoimmune diseases with a high risk of disability, our study could provide valuable indications for translational medicine.

Increased Percentage of CD8+CD28- Regulatory T Cells With Fingolimod Therapy in Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Fingolimod, an oral therapy for MS, decreases expression of membrane S1P1 receptors on CD4⁺ memory cells, causing their retention and deactivation in lymph nodes. We determined fingolimod effects on the number and proportion of potentially CNS-damaging CD8⁺CD28⁺ cytolytic T lymphocyte cells (CTLs) and on MS-depleted and dysfunctional CD8⁺CD28^- anti-inflammatory suppressor/regulatory T cells (Treg) and on CD8⁺ T-cell expression of the CD69 activation/lymph node retention protein in MS.

METHODS

CD8, CD28, CD4, and CD69 expression on peripheral blood mononuclear cells was measured with flow cytometry. In vitro concanavalin A (ConA) activation of T cells, including CD8⁺CD28^- cells, was used to mimic inflammation.

RESULTS

Fifty-nine patients with MS, 35 therapy-naive (16 clinically stable; 19 exacerbating) and 24 fingolimod-treated (19 clinically stable; 5 exacerbating), and 26 matched healthy controls (HCs) were compared. In therapy-naive patients, the CD8⁺ Treg percent of total lymphocytes was only 1/4 of HC levels. In fingolimod-treated patients, however, CD8⁺ Treg percentages rose to 2.5-fold higher than in HC and 10-fold higher than in therapy-naive MS. With fingolimod therapy, in contrast, CD8⁺ CTL levels were less than half of levels in HCs and therapy-naive patients. In HCs and all MS, activation with ConA strongly induced CD69 expression on CD4⁺ cells and induced 3-fold higher CD69 levels on CD8⁺ CTL than on CD8⁺ Treg. Fingolimod and analogs in vitro did not modify lymphocyte CD69 expression. Lower levels of CD69 on CD8⁺ Treg than on CTL may allow easier Treg egress from lymph nodes and enhance control of peripheral inflammation. In vitro activation reduced the already low CD8⁺ Treg population in therapy-naive MS, but only slightly altered Treg levels in fingolimod-treated MS.

DISCUSSION

Fingolimod therapy markedly increases the percentage of CD8⁺ Treg in MS, reversing the low CD8⁺ Treg:CTL ratio seen in untreated MS. The increase in immune regulatory cells has potential therapeutic benefit in MS. Activation in vitro depletes CD8⁺CD28⁺CTL in patients with MS; the loss is more pronounced in older patients with MS. This suggests that inflammation can disrupt the tenuous immune regulation in MS, especially in older patients.

Patients With Severe Multiple Sclerosis Exhibit Functionally Altered CD8+ Regulatory T Cells

BACKGROUND AND OBJECTIVES

Multiple sclerosis (MS) is a chronic inflammatory and demyelinating disease of the CNS. Studies of immune dysfunction in MS have mostly focused on CD4⁺ Tregs, but the role of CD8⁺ Tregs remains largely unexplored. We previously evidenced the suppressive properties of rat and human CD8⁺CD45RC^low/neg Tregs from healthy individuals, expressing Forkhead box P3 (FOXP3) and acting through interferon-gamma (IFN-γ), transforming growth factor beta (TGFβ), and interleukin-34 (IL-34). secretions to regulate immune responses and control diseases such as transplant rejection. To better understand CD8⁺CD45RC^low/neg Tregs contribution to MS pathology, we further investigated their phenotype, function, and transcriptome in patients with MS.

METHODS

We enrolled adults with relapsing-remitting MS and age-matched and sex-matched healthy volunteers (HVs). CD8⁺ T cells were segregated based on low or lack of expression of CD45RC. First, the frequency in CSF and blood, phenotype, transcriptome, and function of CD8⁺CD45RC^low and ^neg were investigated according to exacerbation status and secondarily, according to clinical severity based on the MS severity score (MSSS) in patients with nonexacerbating MS. We then induced active MOG_35-55 EAE in C57Bl/6 mice and performed adoptive transfer of fresh and expanded CD8⁺CD45RC^neg Tregs to assess their ability to mitigate neuroinflammation in vivo.

RESULTS

Thirty-one untreated patients with relapsing-remitting MS were compared with 40 age-matched and sex-matched HVs. We demonstrated no difference of CSF CD8⁺CD45RC^low and CD8⁺CD45RC^neg proportions, but blood CD8⁺CD45RC^low frequency was lower in patients with MS exacerbation when compared with that in HVs. CD8⁺CD45RC^neg Tregs but not CD8⁺CD45RC^low showed higher suppressive capacities in vitro in MS patients with exacerbation than in patients without acute inflammatory attack. In vitro functional assays showed a compromised suppression capacity of CD8⁺CD45RC^low Tregs in patients with nonexacerbating severe MS, defined by the MSSS. We then characterized murine CD8⁺CD45RC^neg Tregs and demonstrated the potential of CD45RC^neg cells to migrate to the CNS and mitigate experimental autoimmune encephalomyelitis in vivo.

DISCUSSION

Altogether, these results suggest a defect in the number and function of CD8⁺CD45RC^low Tregs during MS relapse and an association of CD8⁺CD45RC^low Tregs dysfunction with MS severity. Thus, CD8⁺CD45RC^low/neg T cells might bring new insights into the pathophysiology and new therapeutic approaches of MS.

Neuroinflammation: Extinguishing a blaze of T cells

Inflammation is a biological process that dynamically alters the surrounding microenvironment, including participating immune cells. As a well-protected organ surrounded by specialized barriers and with immune privilege properties, the central nervous system (CNS) tightly regulates immune responses. Yet in neuroinflammatory conditions, pathogenic immunity can disrupt CNS structure and function. T cells in particular play a key role in promoting and restricting neuroinflammatory responses, while the inflamed CNS microenvironment can influence and reshape T cell function and identity. Still, the contraction of aberrant T cell responses within the CNS is not well understood. Using autoimmunity as a model, here we address the contribution of CD4 T helper (Th) cell subsets in promoting neuropathology and disease. To address the mechanisms antagonizing neuroinflammation, we focus on the control of the immune response by regulatory T cells (Tregs) and describe the counteracting processes that preserve their identity under inflammatory challenges. Finally, given the influence of the local microenvironment on immune regulation, we address how CNS-intrinsic signals reshape T cell function to mitigate abnormal immune T cell responses.

Dietary Isoflavones Alter Gut Microbiota and Lipopolysaccharide Biosynthesis to Reduce Inflammation

The etiopathogenesis of multiple sclerosis (MS) is strongly affected by environmental factors such as diet and the gut microbiota. An isoflavone-rich (ISO) diet was previously shown to reduce the severity of MS in the animal model experimental autoimmune encephalomyelitis (EAE). Translation of this concept to clinical trial where dietary isoflavones may be recommended for MS patients will require preliminary evidence that providing the isoflavone-rich diet to people with MS (PwMS) who lack phytoestrogen-metabolizing bacteria has beneficial effects. We have previously shown that the gut microbiota of PwMS resembles the gut microbiota of mice raised under a phytoestrogen-free (phyto-free) diet in that it lacks phytoestrogen-metabolizing bacteria. To investigate the effects of phytoestrogens on the microbiota inflammatory response and EAE disease severity we switched the diet of mice raised under a phyto-free (PF) diet to an isoflavone-rich diet. Microbiota analysis showed that the change in diet from one that is ISO to one that is PF reduces beneficial bacteria such as Bifidobacterium species. In addition we observed functional differences in lipopolysaccharide (LPS) biosynthesis pathways. Moreover LPS extracted from feces of mice fed an ISO diet induced increased production of anti-inflammatory cytokines from bone marrow-derived macrophages relative to fecal-LPS isolated from mice fed a PF diet. Eventually mice whose diet was switched from a PF diet to an ISO diet trended toward reduced EAE severity and mortality. Overall we show that an isoflavone-rich diet specifically modulates LPS biosynthesis of the gut microbiota imparts an anti-inflammatory response and decreases disease severity.

Manifestation of Susac syndrome during interferon beta-1a and glatiramer acetate treatment for misdiagnosed multiple sclerosis: a case report

Background

Susac syndrome (SS) is characterized by the triad of encephalopathy, branch retinal artery occlusion, and sensorineural hearing loss. However, the diagnosis of SS remains difficult because the clinical triad rarely occurs at disease onset, and symptom severity varies. SS symptoms often suggest other diseases, in particular multiple sclerosis (MS), which is more common. Misdiagnosing SS as MS may cause serious complications because MS drugs, such as interferon beta-1a, can worsen the course of SS. This case report confirms previous reports that the use of interferon beta-1a in the course of misdiagnosed MS may lead to exacerbation of SS. Moreover, our case report shows that glatiramer acetate may also exacerbate the course of SS. To the best of our knowledge, this is the first reported case of exacerbation of SS by glatiramer acetate.

Case presentation

We present a case report of a patient with a primary diagnosis of MS who developed symptoms of SS during interferon beta-1a treatment for MS; these symptoms were resolved after the discontinuation of the treatment. Upon initiation of glatiramer acetate treatment, the patient developed the full clinical triad of SS. The diagnosis of MS was excluded, and glatiramer acetate therapy was discontinued. The patient’s neurological state improved only after the use of a combination of corticosteroids, intravenous immunoglobulins, and azathioprine.

Conclusions

The coincidence of SS signs and symptoms with treatment for MS, first with interferon beta-1a and then with glatiramer acetate, suggests that these drugs may influence the course of SS. This case report indicates that treatment with glatiramer acetate may modulate or even exacerbate the course of SS.

Isoflavone diet ameliorates experimental autoimmune encephalomyelitis through modulation of gut bacteria depleted in patients with multiple sclerosis

The gut microbiota is a potential environmental factor that influences the development of multiple sclerosis (MS). We and others have demonstrated that patients with MS and healthy individuals have distinct gut microbiomes. However, the pathogenic relevance of these differences remains unclear. Previously, we showed that bacteria that metabolize isoflavones are less abundant in patients with MS, suggesting that isoflavone-metabolizing bacteria might provide protection against MS. Here, using a mouse model of MS, we report that an isoflavone diet provides protection against disease, which is dependent on the presence of isoflavone-metabolizing bacteria and their metabolite equol. Notably, the composition of the gut microbiome in mice fed an isoflavone diet exhibited parallels to healthy human donors, whereas the composition in those fed an isoflavone-free diet exhibited parallels to patients with MS. Collectively, our study provides evidence that dietary-induced gut microbial changes alleviate disease severity and may contribute to MS pathogenesis.

Encephalitogenic and Regulatory CD8 T Cells in Multiple Sclerosis and Its Animal Models

Multiple sclerosis (MS), a neuroinflammatory disease that affects millions worldwide, is widely thought to be autoimmune in etiology. Historically, research into MS pathogenesis has focused on autoreactive CD4 T cells because of their critical role in the animal model, experimental autoimmune encephalomyelitis, and the association between MS susceptibility and single-nucleotide polymorphisms in the MHC class II region. However, recent studies have revealed prominent clonal expansions of CD8 T cells within the CNS during MS. In this paper, we review the literature on CD8 T cells in MS, with an emphasis on their potential effector and regulatory properties. We discuss the impact of disease modifying therapies, currently prescribed to reduce MS relapse rates, on CD8 T cell frequency and function. A deeper understanding of the role of CD8 T cells in MS may lead to the development of more effective and selective immunomodulatory drugs for particular subsets of patients.

CD8+ T cells: The past and future of immune regulation

Regulation of the adaptive immune response is critical for health. Regulatory activity can be found in multiple components of the immune system, however, the focus on particular components of the immune regulatory network has left many aspects of this critical immune component understudied. Here we review the evidence for activities of CD8+ T cells in immune homeostasis and regulation of autoimmune reactivity. The heterogeneous nature of identified CD8+ cell types are examined, and common phenotypes associated with functional activities are defined. The varying types of antigen signal crucial for CD8+ T cell regulatory activity are identified and the implications of these activation pathways for control of adaptive responses is considered. Finally, the promising capacity for transgenic antigen receptor directed cytotoxicity as a mechanism for modulation of autoimmunity is detailed.

Immune Autoregulatory CD8 T Cells Require IFN-γ Responsiveness to Optimally Suppress Central Nervous System Autoimmunity

Investigating the complex cellular interplay controlling immunopathogenic and immunoregulatory responses is critical for understanding multiple sclerosis (MS) and for developing successful immunotherapies. Our group has demonstrated that CNS myelin-specific CD8 T cells unexpectedly harbor immune regulatory capacity in both mouse and human. In particular, PLP178-191-specific CD8 T cells (PLP-CD8) robustly suppress the MS mouse model experimental autoimmune encephalomyelitis. We have recently shown that this depends on PLP-CD8 elaborating IFN-γ and perforin in a coordinated suppression program over time. However, the cellular target and downstream effects of CD8 T cell-derived IFN-γ remains poorly understood. In this study, we show that although wild-type (WT) PLP-CD8 were robustly suppressive in IFN-γR-deficient mice, IFN-γR-deficient PLP-CD8 exhibited suboptimal suppression in WT mice. Compared with WT counterparts, IFN-γR-deficient PLP-CD8 were defective in suppressing disease in IFN-γ-deficient recipients, a scenario in which the only IFN-γ available to WT PLP-CD8 is that which they produce themselves. Further, we found that IFN-γR-deficient PLP-CD8 exhibited altered granzyme/IFN-γ profiles, altered migration in recipients, and deficits in killing capacity in vivo. Collectively, this work suggests that IFN-γ responsiveness allows myelin-specific CD8 T cells to optimally perform autoregulatory function in vivo. These insights may help elucidate future adoptive immunotherapeutic approaches for MS patients.

Scoring disease in an animal model of multiple sclerosis using a novel infrared-based automated activity-monitoring system

Multiple sclerosis (MS) is a chronic demyelinating disorder of the central nervous system (CNS). Its corresponding animal model, experimental autoimmune encephalomyelitis (EAE), is widely used to understand disease pathogenesis and test novel therapeutic agents. However, existing methods to score EAE disease severity are subjective and often vary between individual researchers, making it difficult to translate findings across different studies. An enhanced automated method of disease scoring would eliminate subjectivity and reduce operator-dependent errors. Here, we used an Infra-Red Activity Monitoring System (IRAMS) to measure murine locomotor activity as a surrogate measure of disease severity and compared it to standard EAE scoring methods. In mice immunized with CNS-specific myelin antigens, we observed an inverse correlation between disease severity and mouse activity, with the IRAMS showing enhanced disease scoring compared to standard EAE scoring methods. Relative to standard EAE scoring methods, IRAMS showed comparable measurement of disease relapses and remissions in the SJL/J-relapsing-remitting model of EAE, and could comparably assess the therapeutic efficiency of the MS drug, Copaxone (Glatiramer acetate-GA). Thus, the IRAMS is a method to measure disease severity in EAE without subjective bias and is a tool to consistently assess the efficacy of novel therapeutic agents for MS.

Prevotella histicola, A Human Gut Commensal, Is as Potent as COPAXONE® in an Animal Model of Multiple Sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system. We and others have shown that there is enrichment or depletion of some gut bacteria in MS patients compared to healthy controls (HC), suggesting an important role of the gut bacteria in disease pathogenesis. Thus, specific gut bacteria that are lower in abundance in MS patients could be used as a potential treatment option for this disease. In particular, we and others have shown that MS patients have a lower abundance of Prevotella compared to HC, whereas the abundance of Prevotella is increased in patients that receive disease-modifying therapies such as Copaxone® (Glatiramer acetate-GA). This inverse correlation between the severity of MS disease and the abundance of Prevotella suggests its potential for use as a therapeutic option to treat MS. Notably we have previously identified a specific strain, Prevotella histicola (P. histicola), that suppresses disease in the animal model of MS, experimental autoimmune encephalomyelitis (EAE) compared with sham treatment. In the present study we analyzed whether the disease suppressing effects of P. histicola synergize with those of the disease-modifying drug Copaxone® to more effectively suppress disease compared to either treatment alone. Treatment with P. histicola was as effective in suppressing disease as treatment with Copaxone®, whereas the combination of P. histicola plus Copaxone® was not more effective than either individual treatment. P. histicola-treated mice had an increased frequency and number of CD4⁺FoxP3⁺ regulatory T cells in periphery as well as gut and a decreased frequency of pro-inflammatory IFN-γ and IL17-producing CD4 T cells in the CNS, suggesting P. histicola suppresses disease by boosting anti-inflammatory immune responses and inhibiting pro-inflammatory immune responses. In conclusion, our study indicates that the human gut commensal P. histicola can suppress disease as efficiently as Copaxone® and may provide an alternative treatment option for MS patients.

Innate, innate-like and adaptive lymphocytes in the pathogenesis of MS and EAE

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) in which the immune system damages the protective insulation surrounding the nerve fibers that project from neurons. A hallmark of MS and its animal model, experimental autoimmune encephalomyelitis (EAE), is autoimmunity against proteins of the myelin sheath. Most studies in this field have focused on the roles of CD4⁺ T lymphocytes, which form part of the adaptive immune system as both mediators and regulators in disease pathogenesis. Consequently, the treatments for MS often target the inflammatory CD4⁺ T-cell responses. However, many other lymphocyte subsets contribute to the pathophysiology of MS and EAE, and these subsets include CD8⁺ T cells and B cells of the adaptive immune system, lymphocytes of the innate immune system such as natural killer cells, and subsets of innate-like T and B lymphocytes such as γδ T cells, natural killer T cells, and mucosal-associated invariant T cells. Several of these lymphocyte subsets can act as mediators of CNS inflammation, whereas others exhibit immunoregulatory functions in disease. Importantly, the efficacy of some MS treatments might be mediated in part by effects on lymphocytes other than CD4⁺ T cells. Here we review the contributions of distinct subsets of lymphocytes on the pathogenesis of MS and EAE, with an emphasis on lymphocytes other than CD4⁺ T cells. A better understanding of the distinct lymphocyte subsets that contribute to the pathophysiology of MS and its experimental models will inform the development of novel therapeutic approaches.

The Evolving Mechanisms of Action of Glatiramer Acetate

Glatiramer acetate (GA) is a synthetic amino acid copolymer that is approved for treatment of relapsing remitting multiple sclerosis (RRMS) and clinically isolated syndrome (CIS). GA reduces multiple sclerosis (MS) disease activity and has shown comparable efficacy with high-dose interferon-β. The mechanism of action (MOA) of GA has long been an enigma. Originally, it was recognized that GA treatment promoted expansion of GA-reactive T-helper 2 and regulatory T cells, and induced the release of neurotrophic factors. However, GA treatment influences both innate and adaptive immune compartments, and it is now recognized that antigen-presenting cells (APCs) are the initial cellular targets for GA. The anti-inflammatory (M2) APCs induced following treatment with GA are responsible for the induction of anti-inflammatory T cells that contribute to its therapeutic benefit. Here, we review studies that have shaped our current understanding of the MOA of GA.

Role of perforin secretion from CD8+ T-cells in neuronal cytotoxicity in multiple sclerosis

OBJECTIVES

Multiple sclerosis (MS) is the most prevalent autoimmune disease of the central nervous system, and is characterized by inflammation and myelin damage. The immune system initiates the autoimmune response, although the mechanisms of neuronal damage have not been elucidated. The purpose of the present study was to investigate autoreactive CD4+ and CD8⁺ T lymphocytes, in conjunction with other inflammatory cells and cytokines in active MS lesions.

METHODS

EAE animal models was established by plantar injections of MBP (200 μg per rat). Purified CD4+ or CD8+ T-cells were isolated from heparinized peripheral blood (EAE animals and control animals) via negative selection. To examine effects of presence of autoreactive CD4+ and CD8+ T lymphocytes, we carried out ELISA, Western blot analysis and TUNEL. In addition, we examined the direct effects of various factors on neuronal cell death using MTT assay.

RESULTS

The data revealed that CD8+ T-cells were more toxic to neurons compared to CD4+ T-cells, in both the MBP and EAE conditions. Bax was greater increased when neurons were co-cultured with CD8+ T-cells in the MBP group. There is a significant increase in IL-17 secretion by CD4+ T-cells in both the MBP group and EAE group. Neuronal viability were affected by Perforin (1.5 μg/mL).

CONCLUSION

The present study extends previous research by demonstrating the role of CD8+ T-cells in MS and supports perforin secretion by CD8+ T-cells as a potential therapeutic factor. Furthermore, we determined that CD4⁺ T-cells can enhance CD8⁺ T-cell neuronal cytotoxicity via induction of intense inflammation.

Targeting Non-classical Myelin Epitopes to Treat Experimental Autoimmune Encephalomyelitis

Qa-1 epitopes, the peptides that bind to non-classical major histocompatibility complex Ib Qa-1 molecules and are recognized by Qa-1-restricted CD8+ regulatory T (Treg) cells, have been identified in pathogenic autoimmune cells that attack myelin sheath in experimental autoimmune encephalomyelitis (EAE, an animal model for multiple sclerosis [MS]). Additionally, immunization with such epitopes ameliorates the EAE. However, identification of such epitopes requires knowledge of the pathogenic autoimmune cells which are largely unknown in MS patients. Hence, we asked whether the CD8+ Treg cells could directly target the myelin sheath to ameliorate EAE. To address this question, we analyzed Qa-1 epitopes in myelin oligodendrocyte glycoprotein (MOG that is a protein in myelin sheath). Here, we report identification of a MOG-specific Qa-1 epitope. Immunization with this epitope suppressed ongoing EAE, which was abrogated by CD8+ T cell depletion. Additionally, the epitope immunization activated the epitope-specific CD8+ T cells which specifically accumulated in the CNS-draining cervical lymph nodes. Finally, CD8+ T cells primed by the epitope immunization transferred EAE suppression. Hence, this study reveals a novel regulatory mechanism mediated by the CD8+ Treg cells. We propose that immunization with myelin-specific HLA-E epitopes (human homologues of Qa-1 epitopes) is a promising therapy for MS.

Characteristics of HLA-E Restricted T-Cell Responses and Their Role in Infectious Diseases

Human HLA-E can, in addition to self-antigens, also present pathogen-derived sequences, which elicit specific T-cell responses. T-cells recognize their antigen presented by HLA-E highly specifically and have unique functional and phenotypical properties. Pathogen specific HLA-E restricted CD8+ T-cells are an interesting new player in the field of immunology. Future work should address their exact roles and relative contributions in the immune response against infectious diseases.

CD8(+) T-Cells as Immune Regulators of Multiple Sclerosis

The vast majority of studies regarding the immune basis of MS (and its animal model, EAE) have largely focused on CD4(+) T-cells as mediators and regulators of disease. Interestingly, CD8(+) T-cells represent the predominant T-cell population in human MS lesions and are oligoclonally expanded at the site of pathology. However, their role in the autoimmune pathologic process has been both understudied and controversial. Several animal models and MS patient studies support a pathogenic role for CNS-specific CD8(+) T-cells, whereas we and others have demonstrated a regulatory role for these cells in disease. In this review, we describe studies that have investigated the role of CD8(+) T-cells in MS and EAE, presenting evidence for both pathogenic and regulatory functions. In our studies, we have shown that cytotoxic/suppressor CD8(+) T-cells are CNS antigen-specific, MHC class I-restricted, IFNγ- and perforin-dependent, and are able to inhibit disease. The clinical relevance for CD8(+) T-cell suppressive function is best described by a lack of their function during MS relapse, and importantly, restoration of their suppressive function during quiescence. Furthermore, CD8(+) T-cells with immunosuppressive functions can be therapeutically induced in MS patients by glatiramer acetate (GA) treatment. Unlike CNS-specific CD8(+) T-cells, these immunosuppressive GA-induced CD8(+) T-cells appear to be HLA-E restricted. These studies have provided greater fundamental insight into the role of autoreactive as well as therapeutically induced CD8(+) T-cells in disease amelioration. The clinical implications for these findings are immense and we propose that this natural process can be harnessed toward the development of an effective immunotherapeutic strategy.

Autoregulatory CD8 T cells depend on cognate antigen recognition and CD4/CD8 myelin determinants

Objective:

To determine the antigenic determinants and specific molecular requirements for the generation of autoregulatory neuroantigen-specific CD8⁺ T cells in models of multiple sclerosis (MS).

Methods:

We have previously shown that MOG35-55-specific CD8⁺ T cells suppress experimental autoimmune encephalomyelitis (EAE) in the C57BL/6 model. In this study, we utilized multiple models of EAE to assess the ability to generate autoregulatory CD8⁺ T cells.

Results:

We demonstrate that alternative myelin peptides (PLP178-191) and other susceptible mouse strains (SJL) generated myelin-specific CD8⁺ T cells, which were fully capable of suppressing disease. The disease-ameliorating function of these cells was dependent on the specific cognate myelin antigen. Generation of these autoregulatory CD8⁺ T cells was not affected by thymic selection, but was dependent on the presence of both CD4⁺ and CD8⁺ T-cell epitopes in the immunizing encephalitogenic antigen.

Conclusions:

These studies show that the generation of autoregulatory CD8⁺ T cells is a more generalized, antigen-specific phenomenon across multiple neuroantigens and mouse strains, with significant implications in understanding disease regulation.

Stage-Specific Role of Interferon-Gamma in Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis

The role of interferon (IFN)-γ in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), has remained as an enigmatic paradox for more than 30 years. Several studies attribute this cytokine a prominent proinflammatory and pathogenic function in these pathologies. However, accumulating evidence shows that IFN-γ also plays a protective role inducing regulatory cell activity and modulating the effector T cell response. Several innate and adaptive immune cells also develop opposite functions strongly associated with the production of IFN-γ in EAE. Even the suppressive activity of different types of regulatory cells is dependent on IFN-γ. Interestingly, recent data supports a stage-specific participation of IFN-γ in EAE providing a plausible explanation for previous conflicting results. In this review, we will summarize and discuss such literature, emphasizing the protective role of IFN-γ on immune cells. These findings are fundamental to understand the complex role of IFN-γ in the pathogenesis of these diseases and can provide basis for potential stage-specific therapy for MS targeting IFN-γ-signaling or IFN-γ-producing immune cells.

Immune regulation of multiple sclerosis by CD8+ T cells

The role of CD8+ T cells in the process of autoimmune pathology has been both understudied and controversial. Multiple sclerosis (MS) is an inflammatory, demyelinating disorder of the central nervous system (CNS) with underlying T cell-mediated immunopathology. CD8+ T cells are the predominant T cells in human MS lesions, showing oligoclonal expansion at the site of pathology. It is still unclear whether these cells represent pathogenic immune responses or disease-regulating elements. Through studies in human MS and its animal model, experimental autoimmune encephalomyelitis (EAE), we have discovered two novel CD8+ T cell populations that play an essential immunoregulatory role in disease: (1) MHC class Ia-restricted neuroantigen-specific "autoregulatory" CD8+ T cells and (2) glatiramer acetate (GA/Copaxone(®)) therapy-induced Qa-1/HLA-E-restricted GA-specific CD8+ T cells. These CD8+ Tregs suppress proliferation of pathogenic CD4+ CD25- T cells when stimulated by their cognate antigens. Similarly, CD8+ Tregs significantly suppress EAE when transferred either pre-disease induction or during peak disease. The mechanism of disease inhibition depends, at least in part, on an antigen-specific, contact-dependent process and works through modulation of CD4+ T cell responses as well as antigen-presenting cells through a combination of cytotoxicity and cytokine-mediated modulation. This review provides an overview of our understanding of CD8+ T cells in immune-mediated disease, focusing particularly on our findings regarding regulatory CD8+ T cells both in MS and in EAE. Clinical relevance of these novel CD8-regulatory populations is discussed, providing insights into a potentially intriguing, novel therapeutic strategy for these diseases.

Multiple sclerosis: the role of melatonin and N-acetylserotonin

Multiple sclerosis (MS) is an immune mediated disorder that is under intensive investigation in an attempt to improve on available treatments. Many of the changes occurring in MS, including increased mitochondrial dysfunction, pain reporting and depression may be partly mediated by increased indoleamine 2,3-dioxygenase, which drives tryptophan to the production of neuroregulatory tryptophan catabolites and away from serotonin, N-acetylserotonin and melatonin production. The consequences of decreased melatonin have classically been attributed to circadian changes following its release from the pineal gland. However, recent data shows that melatonin may be produced by all mitochondria containing cells to some degree, including astrocytes and immune cells, thereby providing another important MS treatment target. As well as being a powerful antioxidant, anti-inflammatory and antinociceptive, melatonin improves mitochondrial functioning, partly via increased oxidative phosphorylation. Melatonin also inhibits demyelination and increases remyelination, suggesting that its local regulation in white matter astrocytes by serotonin availability and apolipoprotein E4, among other potential factors, will be important in the etiology, course and treatment of MS. Here we review the role of local melatonin and its precursors, N-acetylserotonin and serotonin, in MS.

Cytosolic DNA sensing via the stimulator of interferon genes adaptor: Yin and Yang of immune responses to DNA

DNA is immunogenic and many cells express cytosolic DNA sensors that activate the stimulator of interferon genes (STING) adaptor to trigger interferon type I (IFN-β) release, a potent immune activator. DNA sensing to induce IFN-β triggers host immunity to pathogens but constitutive DNA sensing can induce sustained IFN-β release that incites autoimmunity. Here, we focus on cytosolic DNA sensing via the STING/IFN-β pathway that regulates immune responses. Recent studies reveal that cytosolic DNA sensing via the STING/IFN-β pathway induces indoleamine 2,3 dioxygenase (IDO), which catabolizes tryptophan to suppress effector and helper T-cell responses and activate Foxp3-lineage CD4(+) regulatory T (Treg) cells. During homeostasis, and in some inflammatory settings, specialized innate immune cells in the spleen and lymph nodes may ingest and sense cytosolic DNA to reinforce tolerance that prevents autoimmunity. However, malignancies and pathogens may exploit DNA-induced regulatory responses to suppress natural and vaccine-induced immunity to malignant and infected cells. In this review, we discuss the biologic significance of regulatory responses to DNA and novel approaches to exploit DNA-induced immune responses for therapeutic benefit. The ability of DNA to drive tolerogenic or immunogenic responses highlights the need to evaluate immune responses to DNA in physiologic settings relevant to disease progression or therapy.

Disease exacerbation of multiple sclerosis is characterized by loss of terminally differentiated autoregulatory CD8+ T cells

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system (CNS). Although its etiology remains unknown, pathogenic T cells are thought to underlie MS immune pathology. We recently showed that MS patients harbor CNS-specific CD8+ Tregs that are deficient during disease relapse. We now demonstrate that CNS-specific CD8+ Tregs were cytolytic and could eliminate pathogenic CD4+ T cells. These CD8+ Tregs were present primarily in terminally differentiated (CD27-, CD45RO-) subset and their suppression was IFNγ, perforin and granzyme B-dependent. Interestingly, MS patients with acute relapse displayed a significant loss in terminally differentiated CD8+ T cells, with a concurrent loss in expression of perforin and granzyme B. Pre-treatment of exacerbation-derived CD8+ T cells with IL-12 significantly restored suppressive capability of these cells through upregulation of granzyme B. Our studies uncover immune-suppressive mechanisms of CNS-specific CD8+ Tregs, and may contribute to design of novel immune therapies for MS.