Central Nervous System Autoimmunity Research Articles

Platelets in Multiple Sclerosis: Early and Central Mediators of Inflammation and Neurodegeneration and Attractive Targets for Molecular Imaging and Site-Directed Therapy.

Platelets are clearly central to thrombosis and hemostasis. In addition, more recently, evidence has emerged for non-hemostatic roles of platelets including inflammatory and immune reactions/responses. Platelets express immunologically relevant ligands and receptors, demonstrate adhesive interactions with endothelial cells, monocytes and neutrophils, and toll-like receptor (TLR) mediated responses. These properties make platelets central to innate and adaptive immunity and potential candidate key mediators of autoimmune disorders. Multiple sclerosis (MS) is the most common chronic autoimmune central nervous system (CNS) disease. An association between platelets and MS was first indicated by the increased adhesion of platelets to endothelial cells. This was followed by reports identifying structural and functional changes of platelets, their chronic activation in the peripheral blood of MS patients, platelet presence in MS lesions and the more recent revelation that these structural and functional abnormalities are associated with all MS forms and stages. Investigations based on the murine experimental autoimmune encephalomyelitis (EAE) MS model first revealed a contribution to EAE pathogenesis by exacerbation of CNS inflammation and an early role for platelets in EAE development via platelet-neuron and platelet-astrocyte associations, through sialated gangliosides in lipid rafts. Our own studies refined and extended these findings by identifying the critical timing of platelet accumulation in pre-clinical EAE and establishing an initiating and central rather than merely exacerbating role for platelets in disease development. Furthermore, we demonstrated platelet-neuron associations in EAE, coincident with behavioral changes, but preceding the earliest detectable autoreactive T cell accumulation. In combination, these findings establish a new paradigm by asserting that platelets play a neurodegenerative as well as a neuroinflammatory role in MS and therefore, that these two pathological processes are causally linked. This review will discuss the implications of these findings for our understanding of MS, for future applications for imaging toward early detection of MS, and for novel strategies for platelet-targeted treatment of MS.

Persistence of self-reactive CD8+ T cells in the CNS requires TOX-dependent chromatin remodeling

Self-reactive CD8+ T cells are important mediators of progressive tissue damage in autoimmune diseases, but the molecular program underlying these cells’ functional adaptation is unclear. Here we characterize the transcriptional and epigenetic landscape of self-reactive CD8+ T cells in a mouse model of protracted central nervous system (CNS) autoimmunity and compare it to populations of CNS-resident memory CD8+ T cells emerging from acute viral infection. We find that autoimmune CD8+ T cells persisting at sites of self-antigen exhibit characteristic transcriptional regulation together with distinct epigenetic remodeling. This self-reactive CD8+ T cell fate depends on the transcriptional regulation by the DNA-binding HMG-box protein TOX which remodels more than 400 genomic regions including loci such as Tcf7, which is central to stemness of CD8+ T cells. Continuous exposure to CNS self-antigen sustains TOX levels in self-reactive CD8+ T cells, whereas genetic ablation of TOX in CD8+ T cells results in shortened persistence of self-reactive CD8+ T cells in the inflamed CNS. Our study establishes and characterizes the genetic differentiation program enabling chronic T cell-driven immunopathology in CNS autoimmunity.

IL-17 controls central nervous system autoimmunity through the intestinal microbiome.

Interleukin-17A- (IL-17A) and IL-17F-producing CD4+ T helper cells (TH17 cells) are implicated in the development of chronic inflammatory diseases, such as multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). TH17 cells also orchestrate leukocyte invasion of the central nervous system (CNS) and subsequent tissue damage. However, the role of IL-17A and IL-17F as effector cytokines is still confused with the encephalitogenic function of the cells that produce these cytokines, namely, TH17 cells, fueling a long-standing debate in the neuroimmunology field. Here, we demonstrated that mice deficient for IL-17A/F lose their susceptibility to EAE, which correlated with an altered composition of their gut microbiota. However, loss of IL-17A/F in TH cells did not diminish their encephalitogenic capacity. Reconstitution of a wild-type-like intestinal microbiota or reintroduction of IL-17A specifically into the gut epithelium of IL-17A/F-deficient mice reestablished their susceptibility to EAE. Thus, our data demonstrated that IL-17A and IL-17F are not encephalitogenic mediators but rather modulators of intestinal homeostasis that indirectly alter CNS-directed autoimmunity.

Current concepts on communication between the central nervous system and peripheral immunity via lymphatics: what roles do lymphatics play in brain and spinal cord disease pathogenesis?

The central nervous system (CNS) lacks conventional lymphatics within the CNS parenchyma, yet still maintains fluid homeostasis and immunosurveillance. How the CNS communicates with systemic immunity has thus been a topic of interest for scientists in the past century, which has led to several theories of CNS drainage routes. In addition to perineural routes, rediscoveries of lymphatics surrounding the CNS in the meninges revealed an extensive network of lymphatics, which we now know play a significant role in fluid homeostasis and immunosurveillance. These meningeal lymphatic networks exist along the superior sagittal sinus and transverse sinus dorsal to the brain, near the cribriform plate below the olfactory bulbs, at the base of the brain, and surrounding the spinal cord. Inhibition of one or all of these lymphatic networks can reduce CNS autoimmunity in a mouse model of multiple sclerosis (MS), while augmenting these lymphatic networks can improve immunosurveillance, immunotherapy, and clearance in glioblastoma, Alzheimer's disease, traumatic brain injury, and cerebrovascular injury. In this review, we will provide historical context of how CNS drainage contributes to immune surveillance, how more recently published studies fit meningeal lymphatics into the context of CNS homeostasis and neuroinflammation, identify the complex dualities of lymphatic function during neuroinflammation and how therapeutics targeting lymphatic function may be more complicated than currently appreciated, and conclude by identifying some unresolved questions and controversies that may guide future research.

Dysregulated follicular regulatory T cells and antibody responses exacerbate experimental autoimmune encephalomyelitis

BackgroundFollicular regulatory T (TFR) cells are essential for the regulation of germinal center (GC) response and humoral self-tolerance. Dysregulated follicular helper T (TFH) cell-GC-antibody (Ab) response secondary to dysfunctional TFR cells is the root of an array of autoimmune disorders. The contribution of TFR cells to the pathogenesis of multiple sclerosis (MS) and murine experimental autoimmune encephalomyelitis (EAE) remains largely unclear.MethodsTo determine the impact of dysregulated regulatory T cells (Tregs), TFR cells, and Ab responses on EAE, we compared the MOG-induced EAE in mice with a FoxP3-specific ablation of the transcription factor Blimp1 to control mice. In vitro co-culture assays were used to understand how Tregs and Ab regulate the activity of microglia and central nervous system (CNS)-infiltrating myeloid cells.ResultsMice with a FoxP3-specific deletion of Blimp1 developed severe EAE and failed to recover compared to control mice, reflecting conversion of Tregs into interleukin (IL)-17A/granulocyte-macrophage colony-stimulating factor (GM-CSF)-producing effector T cells associated with increased TFH-Ab responses, more IgE deposition in the CNS, and inability to regulate CNS CD11b+ myeloid cells. Notably, serum IgE titers were positively correlated with EAE scores, and culture of CNS CD11b+ cells with sera from these EAE mice enhanced their activation, while transfer of Blimp1-deficient TFR cells promoted Ab production, activation of CNS CD11b+ cells, and EAE.ConclusionsBlimp1 is essential for the maintenance of TFR cells and Ab responses in EAE. Dysregulated TFR cells and Ab responses promote CNS autoimmunity.

NMDA and AMPA Receptor Autoantibodies in Brain Disorders: From Molecular Mechanisms to Clinical Features.

The role of autoimmunity in central nervous system (CNS) disorders is rapidly expanding. In the last twenty years, different types of autoantibodies targeting subunits of ionotropic glutamate receptors have been found in a variety of patients affected by brain disorders. Several of these antibodies are directed against NMDA receptors (NMDAR), mostly in autoimmune encephalitis, whereas a growing field of research has identified antibodies against AMPA receptor (AMPAR) subunits in patients with different types of epilepsy or frontotemporal dementia. Several in vitro and in vivo studies performed in the last decade have dramatically improved our understanding of the molecular and functional effects induced by both NMDAR and AMPAR autoantibodies at the excitatory glutamatergic synapse and, consequently, their possible role in the onset of clinical symptoms. In particular, the method by which autoantibodies can modulate the localization at synapses of specific target subunits leading to functional impairments and behavioral alterations has been well addressed in animal studies. Overall, these preclinical studies have opened new avenues for the development of novel pharmacological treatments specifically targeting the synaptic activation of ionotropic glutamate receptors.

Modeling a complex disease: Multiple sclerosis-Update 2020.

Multiple sclerosis (MS) is a complex inflammatory disease of the central nervous system (CNS) with an unknown etiology. Thereby, MS is not a uniform disease but rather represents a spectrum of disorders, where each aspect needs to be modeled with specific requirements-for a systematic overview see our previous issue of this review (Kurschus, Wortge, & Waisman, 2011). However, there is broad consensus about the critical involvement of the immune system in the disease pathogenesis. To better understand how the immune system contributes to CNS autoimmunity, the model of experimental autoimmune encephalomyelitis (EAE) was developed. EAE can be induced in susceptible animals in many different ways, with the most popular protocol involving the activation of self-reactive T cells by a peptide based on the myelin oligodendrocyte glycoprotein sequence. In the last 10 years this model has led to major advances in our understanding of the immune system, especially the nature of IL-17-producing T cells (Th17 cells), host-microbiome interactions, the gut-brain axis and how the immune system can cause damage in different regions of the brain and the spinal cord. This update summarizes some of the main achievements in the field in the last 10 years.

IMMU-28. INDUCTION OF TERTIARY LYMPHOID STRUCTURE-LIKE T-CELL CLUSTERS BY DELIVERY OF A NOVEL GENE COMBINATION INTO AN IMMUNOCOMPETENT MOUSE MODEL OF GLIOBLASTOMA

Abstract The lack of conventional lymphatic drainage to and from the brain parenchyma restricts the capacity of the peripheral immune system to recognize and respond to glioma antigens. In some peripheral solid tumor types and central nervous system autoimmunity, the spontaneous development of tertiary lymphoid structures (TLS) with varying degrees of organization have been observed in human patients and mice following chronic inflammation. In the cancer setting, presence of TLS are generally associated with improved prognosis, especially when they are characterized by intratumoral infiltration of CD8+ T-cells. We aimed to induce the development of TLS in vivo, utilizing our SB28 glioblastoma model which is sparsely infiltrated by lymphocytes. As a proof-of-concept study, we stably transduced SB28 with a combination of several TLS-stimulating factors that we’ve identified and injected these cells into the brain parenchyma of syngeneic C57BL/6J mice. A combination of the chemoattractant and lymphoid follicle-stimulating cytokines LIGHT, CCL21, IL-7, and IL-17 produced substantial infiltration of CD8+CD3+ T-cells into the tumor and nearby parenchyma. However, this combination was also associated with accelerated tumor growth. A modified gene combination including LIGHT, CCL21, and IL-7 promoted CD8+CD3+ T-cell infiltration by flow cytometry, T-cell clustering by immunofluorescence analysis, and inhibited tumor burden compared with the control as measured by bioluminescent imaging. There was also evidence of increased lymphatic vasculature around the margins of T-cell clustering as demonstrated by LYVE-1 staining. Together, these analyses highlight a role for these factors in stimulating the recruitment and clustering of T-cell to the glioblastoma microenvironment in a TLS-like phenomenon. Future studies will evaluate whether the recruitment of other lymphocytes and stromal cells to these TLS-like clusters can promote T-cell memory and persistence. Ultimately, we aim to provide these factors utilizing a gene delivery method that will prove translatable to the clinic and complementary to existing T-cell therapies.

Interferon-γ/Interleukin-27 Axis Induces Programmed Death Ligand 1 Expression in Monocyte-Derived Dendritic Cells and Restores Immune Tolerance in Central Nervous System Autoimmunity.

Antigen (Ag)-specific tolerance induction by intravenous (i. v.) injection of high-dose auto-Ags has been explored for therapy of autoimmune diseases, including multiple sclerosis (MS). It is thought that the advantage of such Ag-specific therapy over non-specific immunomodulatory treatments would be selective suppression of a pathogenic immune response without impairing systemic immunity, thus avoiding adverse effects of immunosuppression. Auto-Ag i.v. tolerance induction has been extensively studied in experimental autoimmune encephalomyelitis (EAE), an animal model of MS, and limited clinical trials demonstrated that it is safe and beneficial to a subset of MS patients. Nonetheless, the mechanisms of i.v. tolerance induction are incompletely understood, hampering the development of better approaches and their clinical application. Here, we describe a pathway whereby auto-Ag i.v. injected into mice with ongoing clinical EAE induces interferon-gamma (IFN-γ) secretion by auto-Ag-specific CD4+ T cells, triggering interleukin (IL)-27 production by conventional dendritic cells type 1 (cDC1). IL-27 then, via signal transducer and activator of transcription 3 activation, induces programmed death ligand 1 (PD-L1) expression by monocyte-derived dendritic cells (moDCs) in the central nervous system of mice with EAE. PD-L1 interaction with programmed cell death protein 1 on pathogenic CD4+ T cells leads to their apoptosis/anergy, resulting in disease amelioration. These findings identify a key role of the IFN-γ/IL-27/PD-L1 axis, involving T cells/cDC1/moDCs in the induction of i.v. tolerance.

Using data science for medical decision making case: role of gut microbiome in multiple sclerosis

BackgroundA decade ago, the advancements in the microbiome data sequencing techniques initiated the development of research of the microbiome and its relationship with the host organism. The development of sophisticated bioinformatics and data science tools for the analysis of large amounts of data followed. Since then, the analyzed gut microbiome data, where microbiome is defined as a network of microorganisms inhabiting the human intestinal system, has been associated with several conditions such as irritable bowel syndrome - IBS, colorectal cancer, diabetes, obesity, and metabolic syndrome, and lately in the study of Parkinson’s and Alzheimer’s diseases as well. This paper aims to provide an understanding of differences between microbial data of individuals who have been diagnosed with multiple sclerosis and those who were not by exploiting data science techniques on publicly available data.MethodsThis study examines the relationship between multiple sclerosis (MS), an autoimmune central nervous system disease, and gut microbial community composition, using the samples acquired by 16s rRNA sequencing technique. We have used three different sets of MS samples sequenced during three independent studies (Jangi et al, Nat Commun 7:1–11, 2016), (Miyake et al, PLoS ONE 10:0137429, 2015), (McDonald et al, Msystems 3:00031–18, 2018) and this approach strengthens our results. Analyzed sequences were from healthy control and MS groups of sequences. The extracted set of statistically significant bacteria from the (Jangi et al, Nat Commun 7:1–11, 2016) dataset samples and their statistically significant predictive functions were used to develop a Random Forest classifier. In total, 8 models based on two criteria: bacteria abundance (at six taxonomic levels) and predictive functions (at two levels), were constructed and evaluated. These include using taxa abundances at different taxonomy levels as well as predictive function analysis at different hierarchical levels of KEGG pathways.ResultsThe highest accuracy of the classification model was obtained at the genus level of taxonomy (76.82%) and the third hierarchical level of KEGG pathways (70.95%). The second dataset’s 18 MS samples (Miyake et al, PLoS ONE 10:0137429, 2015) and 18 self-reported healthy samples from the (McDonald et al, Msystems 3:00031–18, 2018) dataset were used to validate the developed classification model. The significance of this step is to show that the model is not overtrained for a specific dataset but can also be used on other independent datasets. Again, the highest classification model accuracy for both validating datasets combined was obtained at the genus level of taxonomy (70.98%) and third hierarchical level of KEGG pathways (67.24%). The accuracy of the independent set remained very relevant.ConclusionsOur results demonstrate that the developed classification model provides a good tool that can be used to suggest the presence or absence of MS condition by collecting and analyzing gut microbiome samples. The accuracy of the model can be further increased by using sequencing methods that allow higher taxa resolution (i.e. shotgun metagenomic sequencing).

C-Jun N-Terminal Kinase as a Therapeutic Target in Experimental Autoimmune Encephalomyelitis.

c-Jun N-terminal kinase (JNK) is upregulated during multiple sclerosis relapses and at the peak of experimental autoimmune encephalomyelitis (EAE). We aim to investigate the effects of pharmacological pan-JNK inhibition on the course of myelin oligodendrocyte glycoprotein (MOG35-55) EAE disease using in vivo and in vitro experimental models. EAE was induced in female C57BL/6JRj wild type mice using MOG35-55. SP600125 (SP), a reversible adenosine triphosphate competitive pan-JNK inhibitor, was then given orally after disease onset. Positive correlation between SP plasma and brain concentration was observed. Nine, but not three, consecutive days of SP treatment led to a significant dose-dependent decrease of mean cumulative MOG35-55 EAE severity that was associated with increased mRNA expression of interferon gamma (INF-γ) and tumor necrosis factor alpha (TNF-α) in the spinal cord. On a histological level, reduced spinal cord immune cell-infiltration predominantly of CD3+ T cells as well as increased activity of Iba1+ cells were observed in treated animals. In addition, in vitro incubation of murine and human CD3+ T cells with SP resulted in reduced T cell apoptosis and proliferation. In conclusion, our study demonstrates that pharmacological pan-JNK inhibition might be a treatment strategy for autoimmune central nervous system demyelination.

Quantifying immunoregulation by autoantigen‐specific T‐regulatory type 1 cells in mice with simultaneous hepatic and extra‐hepatic autoimmune disorders

Nanoparticles (NPs) displaying autoimmune disease-relevant peptide-major histocompatibility complex class II molecules (pMHCII-NPs) trigger cognate T-regulatory type 1 (Tr1)-cell formation and expansion, capable of reversing organ-specific autoimmune responses. These pMHCII-NPs that display epitopes from mitochondrial protein can blunt the progression of both autoimmune hepatitis (AIH) and experimental autoimmune encephalomyelitis (EAE) in mice carrying either disease. However, with co-morbid mice having both diseases, these pMHCII-NPs selectively treat AIH. In contrast, pMHCII-NPs displaying central nervous system (CNS)-specific epitopes can efficiently treat CNS autoimmunity, both in the absence and presence of AIH, without having any effects on the progression of the latter. Here, we develop a compartmentalized population model of T-cells in co-morbid mice to identify the mechanisms by which Tr1 cells mediate organ-specific immunoregulation. We perform time-series simulations and bifurcation analyses to study how varying physiological parameters, including local cognate antigenic load and rates of Tr1-cell recruitment and retention, affect T-cell allocation and Tr1-mediated immunoregulation. Various regimes of behaviour, including 'competitive autoimmunity' where pMHCII-NP-treatment fails against both diseases, are identified and compared with experimental observations. Our results reveal that a transient delay in Tr1-cell recruitment to the CNS, resulting from inflammation-dependent Tr1-cell allocation, accounts for the liver-centric effects of AIH-specific pMHCII-NPs in co-morbid mice as compared with mice exclusively having EAE. They also suggest that cognate autoantigen expression and local Tr1-cell retention are key determinants of effective regulatory-cell function. These results thus provide new insights into the rules that govern Tr1-cell recruitment and their autoregulatory function.

Visualizing the Central Nervous System: Imaging Tools for Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorders.

Multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD) are autoimmune central nervous system conditions with increasing incidence and prevalence. While MS is the most frequent inflammatory CNS disorder in young adults, NMOSD is a rare disease, that is pathogenetically distinct from MS, and accounts for approximately 1% of demyelinating disorders, with the relative proportion within the demyelinating CNS diseases varying widely among different races and regions. Most immunomodulatory drugs used in MS are inefficacious or even harmful in NMOSD, emphasizing the need for a timely and accurate diagnosis and distinction from MS. Despite distinct immunopathology and differences in disease course and severity there might be considerable overlap in clinical and imaging findings, posing a diagnostic challenge for managing neurologists. Differential diagnosis is facilitated by positive serology for AQP4-antibodies (AQP4-ab) in NMOSD, but might be difficult in seronegative cases. Imaging of the brain, optic nerve, retina and spinal cord is of paramount importance when managing patients with autoimmune CNS conditions. Once a diagnosis has been established, imaging techniques are often deployed at regular intervals over the disease course as surrogate measures for disease activity and progression and to surveil treatment effects. While the application of some imaging modalities for monitoring of disease course was established decades ago in MS, the situation is unclear in NMOSD where work on longitudinal imaging findings and their association with clinical disability is scant. Moreover, as long-term disability is mostly attack-related in NMOSD and does not stem from insidious progression as in MS, regular follow-up imaging might not be useful in the absence of clinical events. However, with accumulating evidence for covert tissue alteration in NMOSD and with the advent of approved immunotherapies the role of imaging in the management of NMOSD may be reconsidered. By contrast, MS management still faces the challenge of implementing imaging techniques that are capable of monitoring progressive tissue loss in clinical trials and cohort studies into treatment algorithms for individual patients. This article reviews the current status of imaging research in MS and NMOSD with an emphasis on emerging modalities that have the potential to be implemented in clinical practice.

The impact of regional astrocyte interferon-\u03b3 signaling during chronic autoimmunity: a novel role for the immunoproteasome

BackgroundIn early autoimmune neuroinflammation, interferon (IFN)γ and its upregulation of the immunoproteasome (iP) is pathologic. However, during chronic multiple sclerosis (MS), IFNγ has protective properties. Although dysregulation of the iP has been implicated in neurodegeneration, its function remains to be fully elucidated. Here, we demonstrate that IFNγ signaling in regional astrocytes induces the iP and promotes protection of the CNS during chronic autoimmunity.MethodsIn a multiple sclerosis (MS) brain, we evaluated mRNA expression and labeled postmortem MS brainstem and spinal cord for iP subunits and indicators of oxidative stress. Primary regional human astrocytes were analyzed for iP regulation and function by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), Western blot, OxyBlot, and reactive oxygen species and caspase activity detection assays. Following immunization with myelin oligodendrocyte glycoprotein (MOG)35-55, the role of IFNγ signaling and the iP during chronic experimental autoimmune encephalomyelitis (EAE) were assessed using pharmacologic inhibition of the iP and genetic interruption of IFNγ signaling specifically in astrocytes. Central nervous system (CNS) tissues were analyzed by immunohistochemistry (IHC) and immunofluorescence, and cell-specific colocalization was quantified.ResultsIn MS tissue, iP expression was enhanced in the spinal cord compared to brainstem lesions, which correlated with a decrease in oxidative stress. In vitro, IFNγ stimulation enhanced iP expression, reduced reactive oxygen species burden, and decreased oxidatively damaged and poly-ubiquitinated protein accumulation preferentially in human spinal cord astrocytes, which was abrogated with the use of the iP inhibitor, ONX 0914. During the chronic phase of an MS animal model, EAE, ONX 0914 treatment exacerbated the disease and led to increased oxidative stress and poly-ubiquitinated protein buildup. Finally, mice with astrocyte-specific loss of the IFNγ receptor exhibited worsened chronic EAE associated with reduced iP expression, enhanced lesion size and oxidative stress, and poly-ubiquitinated protein accumulation in astrocytes.ConclusionsTaken together, our data reveal a protective role for IFNγ in chronic neuroinflammation and identify a novel function of the iP in astrocytes during CNS autoimmunity.

Activin-A limits Th17 pathogenicity and autoimmune neuroinflammation via CD39 and CD73 ectonucleotidases and Hif1-α–dependent pathways

In multiple sclerosis (MS), Th17 cells are critical drivers of autoimmune central nervous system (CNS) inflammation and demyelination. Th17 cells exhibit functional heterogeneity fostering both pathogenic and nonpathogenic, tissue-protective functions. Still, the factors that control Th17 pathogenicity remain incompletely defined. Here, using experimental autoimmune encephalomyelitis, an established mouse MS model, we report that therapeutic administration of activin-A ameliorates disease severity and alleviates CNS immunopathology and demyelination, associated with decreased activation of Th17 cells. In fact, activin-A signaling through activin-like kinase-4 receptor represses pathogenic transcriptional programs in Th17-polarized cells, while it enhances antiinflammatory gene modules. Whole-genome profiling and in vivo functional studies revealed that activation of the ATP-depleting CD39 and CD73 ectonucleotidases is essential for activin-A-induced suppression of the pathogenic signature and the encephalitogenic functions of Th17 cells. Mechanistically, the aryl hydrocarbon receptor, along with STAT3 and c-Maf, are recruited to promoter elements on Entpd1 and Nt5e (encoding CD39 and CD73, respectively) and other antiinflammatory genes, and control their expression in Th17 cells in response to activin-A. Notably, we show that activin-A negatively regulates the metabolic sensor, hypoxia-inducible factor-1α, and key inflammatory proteins linked to pathogenic Th17 cell states. Of translational relevance, we demonstrate that activin-A is induced in the CNS of individuals with MS and restrains human Th17 cell responses. These findings uncover activin-A as a critical controller of Th17 cell pathogenicity that can be targeted for the suppression of autoimmune CNS inflammation.

MicroRNA-92a controls the balance between inflammatory and regulatory T cells in CNS autoimmunity

Abstract Multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), are mediated by dysregulated autoreactive T cell responses in the central nervous system (CNS). This dysregulation consists of an imbalance between inflammatory T helper cells, such as Th17 cells, and Foxp3+ T regulatory cells (Tregs). MicroRNAs (miRNAs), a class of small non-coding RNAs, are known to play a key role in immune function, and to be dysregulated in EAE and MS. However, identifying specific miRNA pathways that directly connect clinical activity with immune mechanisms in CNS autoimmunity has been a challenge. Previous work has identified miR-92a as one of the most significantly elevated miRNAs in the sera of MS patients, which positively correlates with neurological symptoms and brain atrophy. We now report a major functional role for miR-92a in CNS autoimmunity. MiR-92a is increased during EAE, and its loss strikingly attenuates clinical disease. This attenuation is accompanied by reduced Th17 and increased Treg cells in the CNS. Mechanistically, we found that T cell-intrinsic miR-92a inhibits the development and function of Treg cells while promoting those of Th17 cells by targeting Foxo1, a key transcription factor in T helper cell biology. Preclinical administration of miR-92a inhibitor phenocopies miR-92a loss and ameliorates EAE. Analogous to mice, miR-92a is significantly elevated in MS patient T cells, and reciprocally regulates human Treg and Th17 differentiation. These findings suggest miR-92a skews the Treg/Th17 balance to promote CNS autoimmunity, and that miR-92a silencing may be of therapeutic benefit for MS patients.

The role of myeloid cell-specific ten eleven translocase 2 (TET2) in regulation of neuroinflammation

Abstract Multiple Sclerosis (MS), is an inflammatory demyelinating disease of the central nervous system (CNS) believed to be autoimmune in etiology. Analysis of legions from MS patients, as well as studies in Experimental Autoimmune Encephalomyelitis (EAE), a murine model of MS, have indicated that myeloid cells play a critical role in the pathogenesis of CNS autoimmunity. Recently, Ten-Eleven Translocation 2 (TET2) was identified as a susceptibility locus for MS. TET2 is a Fe(III), α-ketoglutarate dependent enzyme that catalyzes the oxidation of methylated cytosine to 5′-hydroxymethyl cytosine (5hmC), a stable epigenetic mark. There is growing evidence that TET2 acts as a negative regulator of myeloid cell activation. Further, TET2 and 5hmC are reduced in peripheral blood mononuclear cells of MS patients compared with healthy volunteers. The objective of the current study is to investigate the hypothesis that reductions of TET2 expression and activity in myeloid cells is a critical step in the development of pro-inflammatory myeloid cells during CNS autoimmunity. Our laboratory has found that Tet2 transcripts levels and 5hmC content are reduced in CNS-infiltrating myeloid cells at the peak of EAE compared with the onset or late stages. Adoptive transfer of encephalitogenic CD4+ Th17 cells into Tet2−/+ mice lead to an exacerbated clinical course compared with their Tet2+/+ counterparts. Our data suggests that TET2 expression and activity is dysregulated in myeloid cells and limits neuroinflammation and chronic neurological disability. Interventions that promote Tet2 expression in myeloid cells may ameliorate EAE and, by extension, MS.

Myelin-specific CD8 T cells require IFNγ responsiveness to optimally suppress CNS autoimmunity

Abstract 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 central nervous system (CNS) myelin-specific CD8 T cells unexpectedly harbor striking 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 (EAE). We have recently shown this depends on PLP-CD8 elaborating IFNγ and perforin in a coordinated suppression program over time. However, the cellular target and downstream effects of CD8 T cell-elaborated IFNγ remains poorly understood. Here, we show that while WT PLP-CD8 were robustly suppressive in IFNγR-deficient mice, IFNγR-deficient PLP-CD8 exhibited defective suppression in WT mice. Further, compared to WT counterparts, IFNγR-deficient PLP-CD8 were defective in suppressing disease in IFNγ-deficient recipients, a scenario in which the only IFNγ WT PLP-CD8 “see” is their own. These data indicate that myelin-specific CD8 T cells must sense their own IFNγ in an autocrine/paracrine manner to optimally perform autoregulatory function in vivo. Further mechanistic dissection showed that IFNγR-deficient PLP-CD8 exhibited altered degranulation/granzyme profiles, altered migration in recipients, and potential deficits in killing capacity. Collectively, this work suggests that myelin-specific CD8 T cells require IFNγ-responsiveness to optimally regulate CNS autoimmunity and may help elucidate future adoptive immunotherapeutic approaches in MS.

Angiopoietin-2 blockade ameliorates autoimmune neuroinflammation by inhibiting leukocyte recruitment into the CNS.

Angiopoietin-2 (Ang2), a ligand of the endothelial Tie2 tyrosine kinase, is involved in vascular inflammation and leakage in critically ill patients. However, the role of Ang2 in demyelinating central nervous system (CNS) autoimmune diseases is unknown. Here, we report that Ang2 is critically involved in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), a rodent model of multiple sclerosis. Ang2 expression was induced in CNS autoimmunity, and transgenic mice overexpressing Ang2 specifically in endothelial cells (ECs) developed a significantly more severe EAE. In contrast, treatment with Ang2-blocking Abs ameliorated neuroinflammation and decreased spinal cord demyelination and leukocyte infiltration into the CNS. Similarly, Ang2-binding and Tie2-activating Ab attenuated the development of CNS autoimmune disease. Ang2 blockade inhibited expression of EC adhesion molecules, improved blood-brain barrier integrity, and decreased expression of genes involved in antigen presentation and proinflammatory responses of microglia and macrophages, which was accompanied by inhibition of α5β1 integrin activation in microglia. Taken together, our data suggest that Ang2 provides a target for increasing Tie2 activation in ECs and inhibiting proinflammatory polarization of CNS myeloid cells via α5β1 integrin in neuroinflammation. Thus, Ang2 targeting may serve as a therapeutic option for the treatment of CNS autoimmune disease.

Interleukin-17A Serves a Priming Role in Autoimmunity by Recruiting IL-1β-Producing Myeloid Cells that Promote Pathogenic T Cells

Interleukin-17A (IL-17A) is a major mediator of tissue inflammation in many autoimmune diseases. Anti-IL-17A is an effective treatment for psoriasis and is showing promise in clinical trials in multiple sclerosis. In this study, we find that IL-17A-defective mice or mice treated with anti-IL-17A at induction of experimental autoimmune encephalomyelitis (EAE) are resistant to disease and have defective priming of IL-17-secreting γδ T (γδT17) cells and Th17 cells. However, Tcells from Il17a-/- mice induce EAE in wild-type mice following invitro culture with autoantigen, IL-1β, and IL-23. Furthermore, treatment with IL-1β or IL-17A at induction of EAE restores disease in Il17a-/- mice. Importantly, mobilization of IL-1β-producing neutrophils and inflammatory monocytes and activation of γδT17 cells is reduced in Il17a-/- mice. Our findings demonstrate that a key function of IL-17A in central nervous system (CNS) autoimmunity is to recruit IL-1β-secreting myeloid cells that prime pathogenic γδT17 and Th17 cells.