Induction of gut regulatory CD39+ T cells by teriflunomide protects against EAE

Efficient enzyme-free method to assess the development and maturation of the innate and adaptive immune systems in the mouse colon

Researchers who aim to globally analyze the gastrointestinal immune system via flow cytometry have many protocol options to choose from, with specifics generally tied to gut wall layers of interest. To get a clearer idea of the approach we should use on full-thickness colon samples from mice, we first undertook a systematic comparison of three tissue dissociation techniques: two based on enzymatic cocktails and the other one based on manual crushing. Using flow cytometry panels of general markers of lymphoid and myeloid cells, we found that the presence of cell-surface markers and relative cell population frequencies were more stable with the mechanical method. Both enzymatic approaches were associated with a marked decrease of several cell-surface markers. Using mechanical dissociation, we then developed two minimally overlapping panels, consisting of a total of 26 antibodies, for serial profiling of lymphoid and myeloid lineages from the mouse colon in greater detail. Here, we highlight how we accurately delineate these populations by manual gating, as well as the reproducibility of our panels on mouse spleen and whole blood. As a proof-of-principle of the usefulness of our general approach, we also report segment- and life stage-specific patterns of immune cell profiles in the colon. Overall, our data indicate that mechanical dissociation is more suitable and efficient than enzymatic methods for recovering immune cells from all colon layers at once. Additionally, our panels will provide researchers with a relatively simple tool for detailed immune cell profiling in the murine gastrointestinal tract, regardless of life stage or experimental conditions.

Impact of Disease-Modifying Therapies on Gut-Brain Axis in Multiple Sclerosis

Multiple sclerosis is a chronic, autoimmune-mediated, demyelinating disease whose pathogenesis remains to be defined. In past years, in consideration of a constantly growing number of patients diagnosed with multiple sclerosis, the impacts of different environmental factors in the pathogenesis of the disease have been largely studied. Alterations in gut microbiome composition and intestinal barrier permeability have been suggested to play an essential role in the regulation of autoimmunity. Thus, increased efforts are being conducted to demonstrate the complex interplay between gut homeostasis and disease pathogenesis. Numerous results confirm that disease-modifying therapies (DMTs) used for the treatment of MS, in addition to their immunomodulatory effect, could exert an impact on the intestinal microbiota, contributing to the modulation of the immune response itself. However, to date, the direct influence of these treatments on the microbiota is still unclear. This review intends to underline the impact of DMTs on the complex system of the microbiota-gut-brain axis in patients with multiple sclerosis.

Teriflunomide modulates both innate and adaptive immune capacities in multiple sclerosis

BACKGROUND

Teriflunomide (TER) (Aubagio™) is an FDA-approved disease-modifying therapy (DMT) for relapsing-remitting multiple sclerosis (RRMS). The mechanism of action of TER is thought to be related to the inhibition of dihydroorotate dehydrogenase (DHODH), a key mitochondrial enzyme in the de novo pyrimidine synthesis pathway required by rapidly dividing lymphocytes. Several large pivotal studies have established the efficacy and safety of TER in patients with RRMS. Despite this, little is known about how the adaptive and innate immune cell subsets are affected by the treatment in patients with MS.

METHODS

We recruited 20 patients with RRMS who were newly started on TER and performed multicolor flow cytometry and functional assays on peripheral blood samples. A paired t-test was used for the statistical analysis and comparison.

RESULTS

Our data showed that TER promoted a tolerogenic environment by shifting the balance between activated pathogenic and naïve or immunosuppressive immune cell subsets. In our cohort, TER increased the expression of the immunosuppressive marker CD39 on regulatory T cells (Tregs) while it decreased the expression of the activation marker CXCR3 on CD4⁺ T helper cells. TER treatment also reduced switched memory (sm) B cells while it increased naïve B cells and downregulated the expression of co-stimulatory molecules CD80 and CD86. Additionally, TER reduced the percentage and absolute numbers of natural killer T (NKT) cells, as well as the percentage of natural killer (NK) cells and showed a trend toward reducing the CD56^dim NK pathogenic subset.

CONCLUSION

TER promotes the tolerogenic immune response and suppresses the pathogenic immune response in patients with RRMS.

Repurposing MS immunotherapies for CIDP and other autoimmune neuropathies: unfulfilled promise or efficient strategy?

Despite advances in the treatment of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and other common autoimmune neuropathies (AN), still-many patients with these diseases do not respond satisfactorily to the available treatments. Repurposing of disease-modifying therapies (DMTs) from other autoimmune conditions, particularly multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD), is a promising strategy that may accelerate the establishment of novel treatment choices for AN. This approach appears attractive due to homologies in the pathogenesis of these diseases and the extensive post-marketing experience that has been gathered from treating MS and NMOSD patients. The idea is also strengthened by a number of studies that explored the efficacy of DMTs in animal models of AN but also in some CIDP patients. We here review the available preclinical and clinical data of approved MS therapeutics in terms of their applicability to AN, especially CIDP. Promising therapeutic approaches appear to be B cell-directed and complement-targeting strategies, such as anti-CD20/anti-CD19 agents, Bruton's tyrosine kinase inhibitors and anti-C5 agents, as they exert their effects in the periphery. This is a major advantage because, in contrast to MS, their action in the periphery is sufficient to exert significant immunomodulation.

Effect of IL-27, Teriflunomide and Retinoic Acid and Their Combinations on CD4+ T Regulatory T Cells-An In Vitro Study

The principal goal of the study was to verify the concept of pharmacological induction of Foxp3⁺CD25⁺CD4⁺ T regulatory (Treg) cells which will additionally be characterized by a highly suppressive phenotype, i.e., by extensive CD25 and CD39 expression and IL-10 and TGF-β production. Stimulated and unstimulated murine lymphocytes were exposed to IL-27, teriflunomide (TER), and all trans retinoic acid (ATRA) alone and to their combinations. The study demonstrated that: (a) IL-27 alone induced CD39 expression on Treg cells and the generation of Tr1 cells; (b) TER alone induced Foxp3-expressing CD4⁺ T cells and up-regulated density of CD25 on these cells; TER also induced the ability of Treg cells to TGF-β production; (c) ATRA alone induced CD39 expression on Treg cells. The experiments revealed a strong superadditive effect between IL-27 and ATRA with respect to increasing CD39 expression on Treg cells. Moreover, IL-27 and ATRA in combination, but not alone, induced the ability of Treg cells to IL-10 production. However, the combination of IL-27, TER, and ATRA did not induce the generation of Treg cell subset with all described above features. This was due to the fact that TER abolished all listed above desired effects induced by IL-27 alone, ATRA alone, and their combination. IL-27 alone, ATRA alone, and their combination affected TER-induced effects to a lesser extent. Therefore, it can be concluded that in the aspect of pharmacological induction of Treg cells with a highly suppressive phenotype, the triple combination treatment with TER, IL-27, and ATRA does not provide any benefits over TER alone or dual combination including IL-27 and ATRA.

The adenosinergic signaling in the pathogenesis and treatment of multiple sclerosis

Multiple sclerosis (MS) is a highly disabling, progressive neurodegenerative disease with no curative treatment available. Although significant progress has been made in understanding how MS develops, there remain aspects of disease pathogenesis that are yet to be fully elucidated. In this regard, studies have shown that dysfunctional adenosinergic signaling plays a pivotal role, as patients with MS have altered levels adenosine (ADO), adenosine receptors and proteins involved in the generation and termination of ADO signaling, such as CD39 and adenosine deaminase (ADA). We have therefore performed a literature review regarding the involvement of the adenosinergic system in the development of MS and propose mechanisms by which the modulation of this system can support drug development and repurposing.

Hydroxycarboxylic Acid Receptor 2, a Pleiotropically Linked Receptor for the Multiple Sclerosis Drug, Monomethyl Fumarate. Possible Implications for the Inflammatory Response

Monomethyl fumarate (MMF), metabolite of dimethyl fumarate (DMF), an immunosuppressive drug approved for the treatment of multiple sclerosis (MS), is a potent agonist for hydroxycarboxylic acid receptor 2 (HCAR2), eliciting signals that dampen cell activation or lead to inflammation such as the skin flushing reaction that is one of the main side effects of the treatment, together with gastrointestinal inflammation. Our aim is to further understand the molecular basis underlying these differential effects of the drug. We have used wild-type and HCAR2 knock-out mice to investigate, in vitro and ex vivo under steady-state and pathological conditions, the HCAR2-mediated signaling pathways activated by MMF in dendritic cells (DC), which promote differentiation of T cells, and in intestinal epithelial cells (IEC) where activation of a pro-inflammatory pathway, such as the cyclooxygenase-2 pathway involved in skin flushing, could underlie gastrointestinal side effects of the drug. To understand how DMF treatment might impact on gut inflammation induced by experimental autoimmune encephalomyelitis (EAE), the animal model for MS, we have used 3D X-ray phase contrast tomography and flow cytometry to monitor possible intestinal alterations at morphological and immunological levels, respectively. We show that HCAR2 is a pleiotropically linked receptor for MMF, mediating activation of different pathways leading to different outcomes in different cell types, depending on experimental in-vitro and in-vivo conditions. In the small intestine of EAE-affected mice, DMF treatment affected migration of tolerogenic DC from lamina propria to mesenteric lymph nodes, and/or reverted their profile to pro-inflammatory, probably as a result of reduced expression of aldehyde dehydrogenase and transforming growth factor beta as well as the inflammatory environment. Nevertheless, DMF treatment did not amplify the morphological alterations induced by EAE. On the basis of our further understanding of MMF signaling through HCAR2, we suggest that the pleiotropic signaling of fumarate via HCAR2 should be addressed for its pharmaceutical relevance in devising new lead compounds with reduced inflammatory side effects.

ILC3, a Central Innate Immune Component of the Gut-Brain Axis in Multiple Sclerosis

Gut immune cells have been increasingly appreciated as important players in the central nervous system (CNS) autoimmunity in animal models of multiple sclerosis (MS). Among the gut immune cells, innate lymphoid cell type 3 (ILC3) is of special interest in MS research, as they represent the innate cell counterpart of the major pathogenic cell population in MS, i.e. T helper (Th)17 cells. Importantly, these cells have been shown to stimulate regulatory T cells (Treg) and to counteract pathogenic Th17 cells in animal models of autoimmune diseases. Besides, they are also well known for their ability to stabilize the intestinal barrier and to shape the immune response to the gut microbiota. Thus, proper maintenance of the intestinal barrier and the establishment of the regulatory milieu in the gut performed by ILC3 may prevent activation of CNS antigen-specific Th17 cells by the molecular mimicry. Recent findings on the role of ILC3 in the gut-CNS axis and their relevance for MS pathogenesis will be discussed in this paper. Possibilities of ILC3 functional modulation for the benefit of MS patients will be addressed, as well.

Teriflunomide inhibits activation-induced CD25 expression on T cells and may affect Foxp3-expressing regulatory T cells

Teriflunomide (TER) is an immunomodulatory agent. Although the first reports on the use of TER in dogs have already appeared, immune mechanisms underlying the immunomodulatory effect of TER do not seem to have been fully elucidated yet. There were two aspects of this study. First, further insight into the mode of action of TER was gained by investigating its effect on the expression of IL-2 receptor α-chain (CD25) and Forkhead box P3 (Foxp3) by CD4⁺ and CD8⁺ T cells and apoptosis of these cells. Second, in view in the earlier lack of data on the effect of TER on T cells in dogs, the results of this study filled in this gap. TER at a concentration which can be achieved in vivo prevented or reduced the activation-induced CD25 expression on CD4⁺ and CD8⁺ T cells, respectively. Taking into consideration the role of CD25 in T cell proliferation, this effect may constitute an additional mechanism responsible for the antiproliferative effect of the drug. Under stimulation conditions, TER induced Foxp3 expression in Foxp3-negative CD4⁺ and CD8⁺ T cells, while down-regulating it under unstimulated conditions. These results suggest that TER may generate iTreg cells, but this process requires cell activation. TER was not found to affect on the absolute count and apoptosis of CD4⁺ and CD8⁺ T cells. The results suggest that the impairment of CD25 expression during T cell activation and generation of iTreg cells may constitute additional mechanisms, besides the principal one, underlying the immunomodulatory effect of TER.

Microbiome in Multiple Sclerosis; Where Are We, What We Know and Do Not Know

An increase of multiple sclerosis (MS) incidence has been reported during the last decade, and this may be connected to environmental factors. This review article aims to encapsulate the current advances targeting the study of the gut-brain axis, which mediates the communication between the central nervous system and the gut microbiome. Clinical data arising from many research studies, which have assessed the effects of administered disease-modifying treatments in MS patients to the gut microbiome, are also recapitulated.

Induction of Regulatory Properties in the Intestinal Immune System by Dimethyl Fumarate in Lewis Rat Experimental Autoimmune Neuritis

Objective: Dimethyl fumarate (DMF) exerts immunomodulatory and neuroprotective effects in the animal model of experimental autoimmune neuritis (EAN) in the Lewis rat. DMF has been shown to modulate gut microbiota in veterinary medicine, however the effects of oral DMF on the gut-associated lymphoid tissue (GALT) remain unknown. Methods: Lewis rats were treated orally twice daily with DMF up to day 10 after immunization with immunogenic P2 peptide. Histological, flow cytometric and RT-PCR analyses of the GALT (intraepithelial layer, lamina propria, and Peyer patches) in duodenum, jejunum, and ileum were performed ex vivo. Moreover, cell transfer experiments were used to examine the protective effects of GALT regulatory T cells of the Peyer patches. Results: In the upper layers of duodenum, DMF induced a reduction of the toll-like receptor 4 (TLR4) mRNA expression. This was combined by a decrease of the pro-inflammatory lamina propria IFN-γ mRNA expression. In the ileum, we detected an immunoregulatory phenotype characterized by an increase of FoxP3 mRNA expression and of the nuclear factor (erythroid-derived-2)- like 2 (Nrf2) downstream molecule heme oxygenase-1 (HO-1) mRNA. Finally, CD4⁺ CD25⁺ regulatory T cells were increased in the Peyer patches. In vivo, the protective effect of these regulatory cells was verified by cell transfer into recipient EAN rats. Conclusions: Our results identified a novel immunomodulatory effect of DMF through the different regions and layers of the small intestine, which led to an increase of regulatory T cells, exerting a protective role in experimental neuritis.

The intestinal barrier in multiple sclerosis: implications for pathophysiology and therapeutics

Biological barriers are essential for the maintenance of homeostasis in health and disease. Breakdown of the intestinal barrier is an essential aspect of the pathophysiology of gastrointestinal inflammatory diseases, such as inflammatory bowel disease. A wealth of recent studies has shown that the intestinal microbiome, part of the brain-gut axis, could play a role in the pathophysiology of multiple sclerosis. However, an essential component of this axis, the intestinal barrier, has received much less attention. In this review, we describe the intestinal barrier as the physical and functional zone of interaction between the luminal microbiome and the host. Besides its essential role in the regulation of homeostatic processes, the intestinal barrier contains the gut mucosal immune system, a guardian of the integrity of the intestinal tract and the whole organism. Gastrointestinal disorders with intestinal barrier breakdown show evidence of CNS demyelination, and content of the intestinal microbiome entering into the circulation can impact the functions of CNS microglia. We highlight currently available studies suggesting that there is intestinal barrier dysfunction in multiple sclerosis. Finally, we address the mechanisms by which commonly used disease-modifying drugs in multiple sclerosis could alter the intestinal barrier and the microbiome, and we discuss the potential of barrier-stabilizing strategies, including probiotics and stabilization of tight junctions, as novel therapeutic avenues in multiple sclerosis.

Immunological Aspects of Approved MS Therapeutics

Multiple sclerosis (MS) is the most common neurological immune-mediated disease leading to disability in young adults. The outcome of the disease is unpredictable, and over time, neurological disabilities accumulate. Interferon beta-1b was the first drug to be approved in the 1990s for relapsing-remitting MS to modulate the course of the disease. Over the past two decades, the treatment landscape has changed tremendously. Currently, more than a dozen drugs representing 1 substances with different mechanisms of action have been approved (interferon beta preparations, glatiramer acetate, fingolimod, siponimod, mitoxantrone, teriflunomide, dimethyl fumarate, cladribine, alemtuzumab, ocrelizumab, and natalizumab). Ocrelizumab was the first medication to be approved for primary progressive MS. The objective of this review is to present the modes of action of these drugs and their effects on the immunopathogenesis of MS. Each agent's clinical development and potential side effects are discussed.

Manipulation of Gut Microbiota Influences Immune Responses, Axon Preservation, and Motor Disability in a Model of Progressive Multiple Sclerosis

Gut microbiota dysbiosis has been implicated in MS and other immune diseases, although it remains unclear how manipulating the gut microbiota may affect the disease course. Using a well-established model of progressive MS triggered by intracranial infection with Theiler's murine encephalomyelitis virus (TMEV), we sought to determine whether dysbiosis induced by oral antibiotics (ABX) administered on pre-symptomatic and symptomatic phases of the disease influences its course. We also addressed the effects of microbiota recolonization after ABX withdrawn in the presence or absence of probiotics. Central and peripheral immunity, plasma acetate and butyrate levels, axon damage and motor disability were evaluated. The cocktail of ABX prevented motor dysfunction and limited axon damage in mice, which had fewer CD4⁺ and CD8⁺ T cells in the CNS, while gut microbiota recolonization worsened motor function and axonal integrity. The underlying mechanisms of ABX protective effects seem to involve CD4⁺CD39⁺ T cells and CD5⁺CD1d⁺ B cells into the CNS. In addition, microglia adopted a round amoeboid morphology associated to an anti-inflammatory gene profile in the spinal cord of TMEV mice administered ABX. The immune changes in the spleen and mesenteric lymph nodes were modest, yet ABX treatment of mice limited IL-17 production ex vivo. Collectively, our results provide evidence of the functional relevance of gut microbiota manipulation on the neurodegenerative state and disease severity in a model of progressive MS and reinforce the role of gut microbiota as target for MS treatment.

Modulating acute neuroinflammation in intracerebral hemorrhage: the potential promise of currently approved medications for multiple sclerosis

The secondary inflammatory injury following intracerebral hemorrhage (ICH) results in increased morbidity and mortality. White blood cells have been implicated as critical mediators of this inflammatory injury. Currently, no medications have been clinically proven to ameliorate or beneficially modulate inflammation, or to improve outcomes by any mechanism, following ICH. However, other neuroinflammatory conditions, such as multiple sclerosis, have approved pharmacologic therapies that modulate the inflammatory response and minimize the damage caused by inflammatory cells. Thus, there is substantial interest in existing therapies for neuroinflammation and their potential applicability to other acute neurological diseases such as ICH. In this review, we examined the mechanism of action of twelve currently approved medications for multiple sclerosis: alemtuzumab, daclizumab, dimethyl fumarate, fingolimod, glatiramer acetate, interferon beta-1a, interferon beta-1b, mitoxantrone, natalizumab, ocrelizumab, rituximab, teriflunomide. We analyzed the existing literature pertaining to the effects of these medications on various leukocytes and also with emphasis on mechanisms of action during the acute period following initiation of therapy. As a result, we provide a valuable summary of the current body of knowledge regarding these therapies and evidence that supports or refutes their likely promise for treating neuroinflammation following ICH.

Regulatory B and T lymphocytes in multiple sclerosis: friends or foes?

Current clinical experience with immunomodulatory agents and monoclonal antibodies in principle has established the benefit of depleting lymphocytic populations in relapsing–remitting multiple sclerosis (RRMS). B and T cells may exert multiple pro-inflammatory actions, but also possess regulatory functions making their role in RRMS pathogenesis much more complex. There is no clear correlation of Tregs and Bregs with clinical features of the disease. Herein, we discuss the emerging data on regulatory T and B cell subset distributions in MS and their roles in the pathophysiology of MS and its murine model, experimental autoimmune encephalomyelitis (EAE). In addition, we summarize the immunomodulatory properties of certain MS therapeutic agents through their effect on such regulatory cell subsets and their relevance to clinical outcomes.

Regulatory T cells in multiple sclerosis and myasthenia gravis

Multiple sclerosis (MS) is a chronic debilitating disease of the central nervous system primarily mediated by T lymphocytes with specificity to neuronal antigens in genetically susceptible individuals. On the other hand, myasthenia gravis (MG) primarily involves destruction of the neuromuscular junction by antibodies specific to the acetylcholine receptor. Both autoimmune diseases are thought to result from loss of self-tolerance, which allows for the development and function of autoreactive lymphocytes. Although the mechanisms underlying compromised self-tolerance in these and other autoimmune diseases have not been fully elucidated, one possibility is numerical, functional, and/or migratory deficits in T regulatory cells (Tregs). Tregs are thought to play a critical role in the maintenance of peripheral immune tolerance. It is believed that Tregs function by suppressing the effector CD4+ T cell subsets that mediate autoimmune responses. Dysregulation of suppressive and migratory markers on Tregs have been linked to the pathogenesis of both MS and MG. For example, genetic abnormalities have been found in Treg suppressive markers CTLA-4 and CD25, while others have shown a decreased expression of FoxP3 and IL-10. Furthermore, elevated levels of pro-inflammatory cytokines such as IL-6, IL-17, and IFN-γ secreted by T effectors have been noted in MS and MG patients. This review provides several strategies of treatment which have been shown to be effective or are proposed as potential therapies to restore the function of various Treg subsets including Tr1, iTr35, nTregs, and iTregs. Strategies focusing on enhancing the Treg function find importance in cytokines TGF-β, IDO, interleukins 10, 27, and 35, and ligands Jagged-1 and OX40L. Likewise, strategies which affect Treg migration involve chemokines CCL17 and CXCL11. In pre-clinical animal models of experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune myasthenia gravis (EAMG), several strategies have been shown to ameliorate the disease and thus appear promising for treating patients with MS or MG.

The chicken or the egg dilemma: intestinal dysbiosis in multiple sclerosis

Recent findings suggest that the intestinal microbiota of patients suffering from relapsing remitting multiple sclerosis (MS) shows changes on the relative abundances of archaeal and bacterial genera. Although the richness and overall structure of the microbiota may be similar compared to the intestinal microbiota of healthy controls, elevated and reduced frequencies suggest a dysbiotic microbiota in MS. Over the past decade experimental evidence obtained in murine models of the disease highlighted the important relevance of the microbiota in the regulation of the immune system and in the severity of the disease. More recent findings on peripheral immune cells derived from human MS patients support the initial observations that changes in the microbiota may affect immunological pathways that could exacerbate disease. However, important questions remain to be answered. For instance, it is unclear whether dysbiosis precedes disease or, if in the contrary, an autoimmune disease such as MS can lead to gut dysbiosis. In this brief discussion, we speculate about this later possibility based on findings observed in murine models of disease. Further human studies are needed to answer the dilemma and determine specific immunomodulatory pathways that could have an impact on the therapeutic approaches to treat MS.

From Leflunomide to Teriflunomide: Drug Development and Immunosuppressive Oral Drugs in the Treatment of Multiple Sclerosis

BACKGROUND

Immunosuppressive drugs have been used in the treatment of multiple sclerosis (MS) for a long time. Today, orally available second generation immunosuppressive agents have been approved or are filed for licensing as MS therapeutics. Due to semi-selective targeting of cellular processes, these second-generation immunosuppressive compounds might rather be immunomodulatory. For example, Teriflunomide inhibits the de novo pyrimidine synthesis and thus only targets rapidly proliferating cells, including lymphocytes. It is used as first line disease modifying therapy (DMT) in relapsing-remitting MS (RRMS).

METHODS

Review of online content related to oral immunosuppressants in MS with an emphasis on Teriflunomide.

RESULTS

Teriflunomide and Cladribine are second-generation immunosuppressants that are efficient in the treatment of MS patients. For Teriflunomide, a daily dose of 14 mg reduces the annualized relapse rate (ARR) by more than 30% and disability progression by 30% compared to placebo. Cladribine reduces the ARR by about 50% compared to placebo but has not yet been licensed due to unresolved safety concerns. We also discuss the significance of older immunosuppressive compounds including Azathioprine, Mycophenolate mofetile, and Cyclophosphamide in current MS therapy.

CONCLUSION

Teriflunomide has shown a favorable safety and efficacy profile in RRMS and is a therapeutic option for a distinct group of adult patients with RRMS.