Disrupted balance of T cells under natalizumab treatment in multiple sclerosis

Alterations of Thymus-Derived Tregs in Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Multiple sclerosis (MS) is considered a prototypic autoimmune disease of the CNS. It is the leading cause of chronic neurologic disability in young adults. Proinflammatory B cells and autoreactive T cells both play important roles in its pathogenesis. We aimed to study alterations of regulatory T cells (Tregs), which likely also contribute to the disease, but their involvement is less clear.

METHODS

By combining multiple experimental approaches, we examined the Treg compartments in 41 patients with relapsing-remitting MS and 17 healthy donors.

RESULTS

Patients with MS showed a reduced frequency of CD4+ T cells and Foxp3+ Tregs and age-dependent alterations of Treg subsets. Treg suppressive function was compromised in patients, who were treated with natalizumab, while it was unaffected in untreated and anti-CD20-treated patients. The changes in natalizumab-treated patients included increased proinflammatory cytokines and an altered transcriptome in thymus-derived (t)-Tregs, but not in peripheral (p)-Tregs.

DISCUSSION

Treg dysfunction in patients with MS might be related to an altered transcriptome of t-Tregs and a proinflammatory environment. Our findings contribute to a better understanding of Tregs and their subtypes in MS.

Natalizumab Treatment of Relapsing Remitting Multiple Sclerosis Has No Long-Term Effects on the Proportion of Circulating Regulatory T Cells

INTRODUCTION

Natalizumab (NTZ), a monoclonal antibody against the integrin α4β1 (VLA-4) found on activated T cells and B cells, blocks the interaction of this integrin with adhesion molecules of central nervous system (CNS) endothelial cells and lymphocyte migration through the blood-brain barrier, effectively preventing new lesion formation and relapses in multiple sclerosis (MS). Whether NTZ treatment has additional effects on the peripheral immune system cells, and how its actions compare with other MS disease-modifying treatments, have not been extensively investigated. In particular, its effect on the proportions of circulating regulatory T cells (Treg) is unclear.

METHODS

In this study, we investigated the effect of NTZ treatment in 12 patients with relapsing MS, at 6 and 12 months after the start of treatment. We evaluated the proportions of regulatory T cells (Treg), defined by flow cytometry as CD4+ CD25++ FoxP3+ cells and CD4+ CD25++ CD127- cells at these intervals. As an exploratory study, we also investigated the NTZ effects on the proportions of bulk T and B lymphocyte populations, and of those expressing novel the markers CD195 (CCR5), CD196 (CCR6), or CD161 (KLRB1), which are involved in MS pathogenesis but have been studied less in the context of MS treatment. The effects of NTZ were compared to those obtained with 11 patients under interferon-beta-1a (IFN-β1a) treatment, and against 9 healthy volunteers.

RESULTS

We observed a transient increment in the proportion of Treg cells at 6 months, which was not sustained at 12 months. We observed a reduction in the proportion of T cells expressing CD195 (CCR5) and CD161 (KLRB1) subsets of T cells.

CONCLUSION

We conclude that NTZ does not have an effect on the proportion of Treg cells over 1 year, but it may affect the expression of molecules important for some aspects MS pathogenesis, in a manner that is not shared with IFN-β1a.

Enhanced pathogenicity of Th17 cells due to natalizumab treatment: Implications for MS disease rebound

After natalizumab (NAT) cessation, some multiple sclerosis (MS) patients experience a severe disease rebound. The rebound pathophysiology is still unclear; however, it has been linked to interleukin-17-producing T-helper (Th17) cells. We demonstrate that during NAT treatment, MCAM+CCR6+Th17 cells gradually acquire a pathogenic profile, including proinflammatory cytokine production, pathogenic transcriptional signatures, brain endothelial barrier impairment, and oligodendrocyte damage via induction of apoptotic pathways. This is accompanied by an increase in Th17 cell frequencies in the cerebrospinal fluid of NAT-treated patients. Notably, Th17 cells derived from NAT-treated patients, who later developed a disease rebound upon treatment cessation, displayed a distinct transcriptional pathogenicity profile associated with altered migratory properties. Accordingly, increased brain infiltration of patient Th17 cells was illustrated in a humanized mouse model and brain histology from a rebound patient. Therefore, peripheral blood-accumulated MCAM+CCR6+Th17 cells might be involved in rebound pathophysiology, and monitoring of changes in Th17 cell pathogenicity in patients before/during NAT treatment cessation might enable rebound risk assessment in the future.

The Molecular Mechanisms Through Which Placental Mesenchymal Stem Cell-Derived Extracellular Vesicles Promote Myelin Regeneration

Multiple sclerosis (MS) is a debilitating degenerative disease characterized by an immunological attack on the myelin sheath leading to demyelination and axon degeneration. Mesenchymal stem/stromal cells (MSCs) and secreted extracellular vesicles (EVs) have become attractive targets as therapies to treat neurodegenerative diseases such as MS due to their potent immunomodulatory and regenerative properties. The placenta is a unique source of MSCs (PMSCs), demonstrates "fetomaternal" tolerance during pregnancy, and serves as a novel source of MSCs for the treatment of neurodegenerative diseases. PMSCs and PMSC-EVs have been shown to promote remyelination in animal models of MS, however, the molecular mechanisms by which modulation of autoimmunity and promotion of myelination occurs have not been well elucidated. The current review will address the molecular mechanisms by which PMSC-EVs can promote remyelination in MS.

Long-Term Suppression of Circulating Proinflammatory Cytokines in Multiple Sclerosis Patients Following Autologous Haematopoietic Stem Cell Transplantation

Autologous haematopoietic stem cell transplantation (AHSCT) is a therapeutic option for haematological malignancies, such as non-Hodgkin’s lymphoma (NHL), and more recently, for autoimmune diseases, such as treatment-refractory multiple sclerosis (MS). The immunological mechanisms underlying remission in MS patients following AHSCT likely involve an anti-inflammatory shift in the milieu of circulating cytokines. We hypothesised that immunological tolerance in MS patients post-AHSCT is reflected by an increase in anti-inflammatory cytokines and a suppression of proinflammatory cytokines in the patient blood. We investigated this hypothesis using a multiplex-ELISA assay to compare the concentrations of secreted cytokine in the peripheral blood of MS patients and NHL patients undergoing AHSCT. In MS patients, we detected significant reductions in proinflammatory T helper (Th)17 cytokines interleukin (IL)-17, IL-23, IL-1β, and IL-21, and Th1 cytokines interferon (IFN)γ and IL-12p70 in MS patients from day 8 to 24 months post-AHSCT. These changes were not observed in the NHL patients despite similar pre-conditioning treatment for AHSCT. Some proinflammatory cytokines show similar trends in both cohorts, such as IL-8 and tumour necrosis factor (TNF)-α, indicating a probable treatment-related AHSCT response. Anti-inflammatory cytokines (IL-10, IL-4, and IL-2) were only transiently reduced post-AHSCT, with only IL-10 exhibiting a significant surge at day 14 post-AHSCT. MS patients that relapsed post-AHSCT exhibited significantly elevated levels of IL-17 at 12 months post-AHSCT, unlike non-relapse patients which displayed sustained suppression of Th17 cytokines at all post-AHSCT timepoints up to 24 months. These findings suggest that suppression of Th17 cytokines is essential for the induction of long-term remission in MS patients following AHSCT.

Decreased Neurofilament L Chain Levels in Cerebrospinal Fluid and Tolerogenic Plasmacytoid Dendritic Cells in Natalizumab-Treated Multiple Sclerosis Patients - Brief Research Report

Background

Neurofilament Light (NfL) chain levels in both cerebrospinal fluid (CSF) and serum have been correlated with the reduction of axonal damage in multiple sclerosis (MS) patients treated with Natalizumab (NTZ). However, little is known about the function of plasmacytoid cells in NTZ-treated MS patients.

Objective

To evaluate CSF NfL, serum levels of soluble-HLA-G (sHLA-G), and eventual tolerogenic behavior of plasmacytoid dendritic cells (pDCs) in MS patients during NTZ treatment.

Methods

CSF NfL and serum sHLA-G levels were measured using an ELISA assay, while pDCs (BDCA-2⁺) were accessed through flow cytometry analyses.

Results

CSF levels of NfL were significantly reduced during NTZ treatment, while the serum levels of sHLA-G were increased. Moreover, NTZ treatment enhanced tolerogenic (HLA-G⁺, CD274⁺, and HLA-DR⁺) molecules and migratory (CCR7⁺) functions of pDCs in the peripheral blood.

Conclusion

These findings suggest that NTZ stimulates the production of molecules with immunoregulatory function such as HLA-G and CD274 programmed death-ligand 1 (PD-L1) which may contribute to the reduction of axonal damage represented by the decrease of NfL levels in patients with MS.

In Vivo Induction of Regulatory T Cells Via CTLA-4 Signaling Peptide to Control Autoimmune Encephalomyelitis and Prevent Disease Relapse

Regulatory T cells play a key role in immune tolerance to self-antigens, thereby preventing autoimmune diseases. However, no drugs targeting Treg cells have been approved for clinical trials yet. Here, a chimeric peptide is generated by conjugation of the cytoplasmic domain of CTLA-4 (ctCTLA-4) with dNP2 for intracellular delivery, dNP2-ctCTLA-4, and evaluated Foxp3 expression during Th0, Th1, Treg, and Th17 differentiation dependent on TGF-β. The lysine motif of ctCTLA-4, not tyrosine motif, is required for Foxp3 expression for Treg induction and amelioration of experimental autoimmune encephalomyelitis (EAE). Transcriptome analysis reveals that dNP2-ctCTLA-4-treated T cells express Treg transcriptomic patterns with properties of suppressive functions. In addition, the molecular interaction between the lysine motif of ctCTLA-4 and PKC-η is critical for Foxp3 expression. Although both CTLA-4-Ig and dNP2-ctCTLA-4 treatment in vivo ameliorated EAE progression, only dNP2-ctCTLA-4 requires Treg cells for inhibition of disease progression and prevention of relapse. Furthermore, the CTLA-4 signaling peptide is able to induce human Tregs in vitro and in vivo as well as from peripheral blood mononuclear cells (PBMCs) of multiple sclerosis patients. These results collectively suggest that the chimeric CTLA-4 signaling peptide can be used for successful induction of regulatory T cells in vivo to control autoimmune diseases, such as multiple sclerosis.

Cytokines and Transgenic Matrix in Autoimmune Diseases: Similarities and Differences

Autoimmune diseases are increasingly recognized as disease entities in which dysregulated cytokines contribute to tissue-specific inflammation. In organ-specific and multiorgan autoimmune diseases, the cytokine profiles show some similarities. Despite these similarities, the cytokines have different roles in the pathogenesis of different diseases. Altered levels or action of cytokines can result from changes in cell signaling. This article describes alterations in the JAK-STAT, TGF-β and NF-κB signaling pathways, which are involved in the pathogenesis of multiple sclerosis and systemic lupus erythematosus. There is a special focus on T cells in preclinical models and in patients afflicted with these chronic inflammatory diseases.

Natalizumab in Multiple Sclerosis Treatment: From Biological Effects to Immune Monitoring

Multiple sclerosis is a chronic demyelinating disease of the central nervous system (CNS) with an autoimmune component. Among the recent disease-modifying treatments available, Natalizumab, a monoclonal antibody directed against the alpha chain of the VLA-4 integrin (CD49d), is a potent inhibitor of cell migration toward the tissues including CNS. It potently reduces relapses and active brain lesions in the relapsing remitting form of the disease. However, it has also been associated with a severe infectious complication, the progressive multifocal leukoencephalitis (PML). Using the standard protocol with an injection every 4 weeks it has been shown by a close monitoring of the drug that trough levels soon reach a plateau with an almost saturation of the target cell receptor as well as a down modulation of this receptor. In this review, mechanisms of action involved in therapeutic efficacy as well as in PML risk will be discussed. Furthermore the interest of a biological monitoring that may be helpful to rapidly adapt treatment is presented. Indeed, development of anti-NAT antibodies, although sometimes unapparent, can be detected indirectly by normalization of CD49d expression on circulating mononuclear cells and might require to switch to another drug. On the other hand a stable modulation of CD49d expression might be useful to follow the circulating NAT levels and apply an extended interval dose scheme that could contribute to limiting the risk of PML.

An immunotherapy effect analysis in Rasmussen encephalitis

Background

Immune-mediated mechanisms substantially contribute to the Rasmussen encephalitis (RE) pathology, but for unknown reasons, immunotherapy is generally ineffective in patients who have already developed intractable epilepsy; overall laboratory data regarding the effect of immunotherapy on patients with RE are limited. We analyzed multiple samples from seven differently treated children with RE and evaluated the effects of immunotherapies on neuroinflammation. Immunotherapy was introduced to all patients at the time of intractable epilepsy and they all had to undergo hemispherothomy.

Methods

Immunohistochemistry, flow cytometry, Luminex multiplex bead and enzyme-linked immunosorbent assay techniques were combined to determine: 1) inflammatory changes and lymphocyte subpopulations in 45 brain tissues; 2) lymphocyte subpopulations and the levels of 12 chemokines/cytokines in 24 cerebrospinal fluid (CSF) samples and 30 blood samples; and 3) the dynamics of these parameters in four RE patients from whom multiple samples were collected.

Results

Sustained T cell-targeted therapy with cyclophosphamide, natalizumab, alemtuzumab, and intrathecal methotrexate (ITMTX), but not with azathioprine, substantially reduced inflammation in brain tissues. Despite the therapy, the distributions of CD8⁺ T cells and the levels of C-X-C motif ligand (CXCL) 10, CXCL13, and B cell activating factor (BAFF) in patients’ CSF remained increased compared to controls. A therapeutic approach combining alemtuzumab and ITMTX was the most effective in producing simultaneous reductions in histopathological inflammatory findings and in the numbers of activated CD8⁺ T cells in the brain tissue, as well as in the overall CD8⁺ T cell population and chemokine/cytokine production in the CSF.

Conclusions

We provide evidence that various T cell-targeted immunotherapies reduced inflammation in the brains of RE patients. The observation that intractable epilepsy persisted in all of the patients suggests a relative independence of seizure activity on the presence of T cells in the brain later in the disease course. Thus, new therapeutic targets must be identified. CXCL10, CXCL13 and BAFF levels were substantially increased in CSF from all patients and their significance in RE pathology remains to be addressed.

Blockade of VLA4 sensitizes leukemic and myeloma tumor cells to CD3 redirection in the bone marrow microenvironment

Redirecting T cells to specifically kill malignant cells has been validated as an effective anti-cancer strategy in the clinic with the approval of blinatumomab for acute lymphoblastic leukemia. However, the immunosuppressive nature of the tumor microenvironment potentially poses a significant hurdle to T cell therapies. In hematological malignancies, the bone marrow (BM) niche is protective to leukemic stem cells and has minimized the efficacy of several anti-cancer drugs. In this study, we investigated the impact of the BM microenvironment on T cell redirection. Using bispecific antibodies targeting specific tumor antigens (CD123 and BCMA) and CD3, we observed that co-culture of acute myeloid leukemia or multiple myeloma cells with BM stromal cells protected tumor cells from bispecific antibody-T cell-mediated lysis in vitro and in vivo. Impaired CD3 redirection cytotoxicity was correlated with reduced T cell effector responses and cell-cell contact with stromal cells was implicated in reducing T cell activation and conferring protection of cancer cells. Finally, blocking the VLA4 adhesion pathway in combination with CD3 redirection reduced the stromal-mediated inhibition of cytotoxicity and T cell activation. Our results lend support to inhibiting VLA4 interactions along with administering CD3 redirection therapeutics as a novel combinatorial regimen for robust anti-cancer responses.

Dawn of Monitoring Regulatory T Cells in (Pre-)clinical Studies: Their Relevance Is Slowly Recognised

Regulatory T cells (Tregs) have a prominent role in the control of immune homeostasis. Pharmacological impact on their activity or balance with effector T cells could contribute to (impaired) clinical responses or adverse events. Monitoring treatment-related effects on T cell subsets may therefore be part of (pre-)clinical studies for medicinal products. However, the extent of immune monitoring performed in studies for marketing authorisation and the degree of correspondence with data available in the public domain is not known. We evaluated the presence of T cell immunomonitoring in 46 registration dossiers of monoclonal antibodies indicated for immune-related disorders and published scientific papers. We found that the depth of Treg analysis in registration dossiers was rather small. Nevertheless, data on treatment-related Treg effects are available in public academia-driven studies (post-registration) and suggest that Tregs may act as a biomarker for clinical responses. However, public data are fragmented and obtained with heterogeneity of experimental approaches from a diversity of species and tissues. To reveal the potential added value of T cell (and particular Treg) evaluation in (pre-)clinical studies, more cell-specific data should be acquired, at least for medicinal products with an immunomodulatory mechanism. Therefore, extensive analysis of T cell subset contribution to clinical responses and the relevance of treatment-induced changes in their levels is needed. Preferably, industry and academia should work together to obtain these data in a standardised manner and to enrich our knowledge about T cell activity in disease pathogenesis and therapies. This will ultimately elucidate the necessity of T cell subset monitoring in the therapeutic benefit-risk assessment.

Exosomal miRNAs in central nervous system diseases: biomarkers, pathological mediators, protective factors and therapeutic agents

Exosomes are small bilipid layer-enclosed extracellular vesicles that can be found in tissues and biological fluids. As a key cell-to-cell and distant communication mediator, exosomes are involved in various central nervous system (CNS) diseases, potentially through transferring their contents such as proteins, lipids and nucleic acids to the target cells. Exosomal miRNAs, which are small non-coding RNAs in the exosomes, are known to be more stable than free miRNAs and therefore have lasting effects on disease-related gene expressions. There are distinct profiles of exosomal miRNAs in different types of CNS diseases even before the onset of irreversible neurological damages, indicating that exosomal miRNAs within tissues and biological fluids could serve as promising biomarkers. Emerging evidence has also demonstrated the pathological effects of several exosomal miRNAs in CNS diseases via specific modulation of disease-related factors. Moreover, exosomes carry therapeutically beneficial miRNAs across the blood-brain-barrier, which can be exploited as a powerful drug delivery tool to help alleviating multiple CNS diseases. In this review, we summarize the recent progress made in understanding the biological roles of exosomal miRNAs as potential diagnostic biomarkers, pathological regulators, and therapeutic targets/drugs for CNS diseases. A comprehensive discussion of the main concerns and challenges for the applications of exosomal miRNAs in the clinical setting is also provided.

Proportions of Th17 cells and Th17-related cytokines in neuromyelitis optica spectrum disorders patients: A meta-analysis

BACKGROUND

T helper (Th17) cells play an important role in many autoimmune diseases. In this meta-analysis, we aimed to specify the proportion of Th17 cells and the levels of Th17-related cytokines in neuromyelitis optica spectrum disorders (NMOSD) patients, we did this meta-analysis.

METHODS

Using previously reported data from PubMed, EMBASE, and Web of Science and Cochrane, we explored the proportion of Th17 cells in CD4⁺ T cells in peripheral blood (PB) and the level of Th17-related cytokines, such as interleukin (IL)1β, IL6, IL17, IL21, IL22, IL23 and transforming growth factor -beta (TGFβ), in cerebrospinal fluid (CSF), plasma, and serum in NMOSD patients compared to control group and multiple sclerosis (MS) patients.

RESULTS

In total, 38 trials were included for our analysis. Results showed that the proportion of Th17 cells was higher in NMOSD patients than in the control and MS groups. The levels of IL1β, IL6, IL17 and IL21 in CSF and plasma, and IL6, IL21, IL22, and IL23 in the serum were higher in NMOSD patients than in the control group. The levels of IL6 in CSF and serum and IL17 in plasma and serum were higher in NMOSD patients than in MS patients.

CONCLUSION

The proportion of Th17 cells and the levels of Th17-related cytokines was increased in NMOSD patients compared with the control group and MS patients. The results of this meta-analysis indicated that Th17 cells and Th17-associated cytokines may play an essential role in the pathogenesis of NMOSD. PROSPERO registration: CRD42019128785.

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.

Foxp3+ regulatory T cells expression in neuromyelitis optica spectrum disorders

BACKGROUND

Alterations in the frequency or function of regulatory T cells (Tregs), which play a critical role in the maintenance of peripheral immune tolerance, are known to be involved in the pathogenesis of several autoimmune diseases. Neuromyelitis optica spectrum disorders (NMOSD) are autoimmune inflammatory diseases of the central nervous system (CNS), of which the etiology and mechanisms underlying its development are not completely understood. Although there is increasing evidence for the involvement of effector T cells in NMOSD, no data are available regarding the role of Tregs in its pathogenesis.

AIM

The aim of this study was to investigate the mRNA expression level of regulatory T cell genes in NMOSD.

METHODS

We used gene expression array and RT-PCR analysis to study Treg cell genes in NMOSD RESULTS: A distinctive Treg gene signature in the peripheral blood of NMOSD patients is described, as well as significantly decreased FoxP3 mRNA expression in the peripheral blood mononuclear cells (PBMCs) of the patients vs that in the healthy controls (HCs) (NMOSD,1.8RQ vs HC, 6.8RQ, p = 0.01).

CONCLUSIONS

The present study shows downregulation at the mRNA expression level of a Treg key transcription factor FoxP3, in NMOSD. Exploration of Tregs function and interconnections in the peripheral immune system should advance our understanding of NMOSD pathogenesis.

Ozanimod for the treatment of relapsing remitting multiple sclerosis

INTRODUCTION

Ozanimod is a selective sphingosine 1-phosphate receptor 1 and 5 modulator under development by Celgene, for the treatment of relapsing remitting multiple sclerosis. Extensive clinical experience has become available for the related compound fingolimod, favoring the sphingosine 1-phosphate therapeutic concept. Off-target effects have been attributed to its low receptor specificity and have prompted the development of next generation sphingosine 1-phosphate receptor modulators. Areas covered: The authors evaluate the literature of ozanimod, using the PubMed database as well as repositories of the European Committee for Treatment and Research in Multiple Sclerosis and the American and European Academy of Neurology. Specifically, the authors cover and discuss the preclinical data on ozanimod, pharmacokinetics and dynamics, and data on efficacy and safety from the pivotal trials. Expert opinion: Superiority of ozanimod over intramuscular interferon β-1a with regard to reduction in annualized relapse rate and magnetic resonance imaging outcomes has been shown in two phase III trials. The beneficial effect on brain volume and gray matter loss are encouraging and in line with data on other newer immunomodulators. Ozanimod is a valuable contribution to the therapeutic armamentarium in MS, although the effect on disability progression is unclear and requires further investigations.

Reassessing B cell contributions in multiple sclerosis

There is growing recognition that B cell contributions to normal immune responses extend well beyond their potential to become antibody-producing cells, including roles at the innate-adaptive interface and their potential to modulate the responses of other immune cells such as T cells and myeloid cells. These B cell functions can have both pathogenic and protective effects in the context of central nervous system (CNS) inflammation. Here, we review recent advances in the field of multiple sclerosis (MS), which has traditionally been viewed as primarily a T cell-mediated disease, and we consider antibody-dependent and, particularly, emerging antibody-independent functions of B cells that may be relevant in both the peripheral and CNS disease compartments.

Aging and lymphocyte changes by immunomodulatory therapies impact PML risk in multiple sclerosis patients

New potent immunomodulatory therapies for multiple sclerosis (MS) are associated with increased risk for progressive multifocal leukoencephalopathy (PML). It is unclear why a subset of treated patients develops PML, but patient age has emerged as an important risk factor. PML is caused by the JC virus and aging is associated with immune senescence, which increases susceptibility to infection. With the goal of improving PML risk stratification, we here describe the lymphocyte changes that occur with disease-modifying therapies (DMTs) associated with high or moderate risk toward PML in MS patients, how these changes compare to immune aging, and which measures best correlate with risk. We reviewed studies examining how these therapies alter patient immune profiles, which revealed the induction of changes to lymphocyte number and/or function that resemble immunosenescence. Therefore, the immunosuppressive activity of these MS DMTs may be enhanced in the context of an immune system that is already exhibiting features of senescence.

The Role for Exosomal microRNAs in Disruption of Regulatory T Cell Homeostasis in Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, in which myelin and oligodendrocytes are the main targets recognized by inflammatory CD4⁺ T cells reactive to myelin peptides. Regulatory CD4⁺ T (Treg) cells normally keep homeostasis of the immune system by inhibiting detrimental effects of inflammatory T cells. However, Treg cells are reduced in patients with MS for unknown reason. This commentary highlights a novel function of circulating exosomes to inhibit the differentiation of Treg cells in MS. Our recent work has demonstrated that the circulating exosomes, a member of extracellular vesicles, of patients with MS exert this effect by transferring let-7i to naive CD4⁺ T cells. The transferred let-7i subsequently causes a decreased expression of insulin like growth factor 1 receptor (IGF1R) and transforming growth factor β receptor 1 (TGFBR1), leading to the inhibition of Treg cell differentiation. Thus, extrinsic microRNAs transferred by exosomes might have an active role in triggering autoimmune diseases. We hypothesize that extracellular vesicles including exosomes can be a communication tool between the gut microbiota and the host immune system. Further research in this area will expand the knowledge about the precise mechanism of autoimmune diseases and can lead to a new therapeutic approach.

Understanding Progressive Multifocal Leukoencephalopathy Risk in Multiple Sclerosis Patients Treated with Immunomodulatory Therapies: A Bird's Eye View

The increased use of newer potent immunomodulatory therapies for multiple sclerosis (MS), including natalizumab, fingolimod, and dimethyl fumarate, has expanded the patient population at risk for developing progressive multifocal leukoencephalopathy (PML). These MS therapies shift the profile of lymphocytes within the central nervous system (CNS) leading to increased anti-inflammatory subsets and decreased immunosurveillance. Similar to MS, PML is a demyelinating disease of the CNS, but it is caused by the JC virus. The manifestation of PML requires the presence of an active, genetically rearranged form of the JC virus within CNS glial cells, coupled with the loss of appropriate JC virus-specific immune responses. The reliability of metrics used to predict risk for PML could be improved if all three components, i.e., viral genetic strain, localization, and host immune function, were taken into account. Advances in our understanding of the critical lymphocyte subpopulation changes induced by these MS therapies and ability to detect viral mutation and reactivation will facilitate efforts to develop these metrics.

Circulating exosomes suppress the induction of regulatory T cells via let-7i in multiple sclerosis

Multiple sclerosis (MS) is a T cell-mediated autoimmune disease of the central nervous system. Foxp3⁺ regulatory T (Treg) cells are reduced in frequency and dysfunctional in patients with MS, but the underlying mechanisms of this deficiency are unclear. Here, we show that induction of human IFN-γ⁻IL-17A⁻Foxp3⁺CD4⁺ T cells is inhibited in the presence of circulating exosomes from patients with MS. The exosomal miRNA profile of patients with MS differs from that of healthy controls, and let-7i, which is markedly increased in patients with MS, suppresses induction of Treg cells by targeting insulin like growth factor 1 receptor (IGF1R) and transforming growth factor beta receptor 1 (TGFBR1). Consistently, the expression of IGF1R and TGFBR1 on circulating naive CD4⁺ T cells is reduced in patients with MS. Thus, our study shows that exosomal let-7i regulates MS pathogenesis by blocking the IGF1R/TGFBR1 pathway.

MiRNAs are small RNA molecules that can regulate gene expression. Here the authors show that expression of several exosomal miRNAs are altered in patients with multiple sclerosis, and that let-7i modulates regulatory T cell homeostasis to contribute to pathogenesis.

Role of Immunological Memory Cells as a Therapeutic Target in Multiple Sclerosis

Pharmacological targeting of memory cells is an attractive treatment strategy in various autoimmune diseases, such as psoriasis and rheumatoid arthritis. Multiple sclerosis is the most common inflammatory disorder of the central nervous system, characterized by focal immune cell infiltration, activation of microglia and astrocytes, along with progressive damage to myelin sheaths, axons, and neurons. The current review begins with the identification of memory cell types in the previous literature and a recent description of the modulation of these cell types in T, B, and resident memory cells in the presence of different clinically approved multiple sclerosis drugs. Overall, this review paper tries to determine the potential of memory cells to act as a target for the current or newly-developed drugs.

The Italian Pharmacovigilance Program: An Observational Study of Adverse Effects of Natalizumab in Multiple Sclerosis Therapy

Background

This study shows the results of a regional pharmacovigilance program on Natalizumab therapy in relapsing-remitting multiple sclerosis (RR-MS) patients after 3 years of experience.

Material/Methods

The primary objectives of this study were to estimate the incidence of expected and unexpected adverse effects correlated to Natalizumab therapy in a cohort of 88 RR-MS patients from Sicily, Italy, and to investigate the procedures adopted by the physicians to minimize the risk of developing severe adverse reactions correlated to Natalizumab therapy. Secondary objectives of this study were to evaluate the effectiveness of Natalizumab therapy for a careful examination of the risk/benefit ratio and to assess the actions undertaken in case of adverse reactions.

Results

Among 88 RR-MS patients, 55.68% did not report any type of adverse reaction, 35.22% showed expected adverse reactions (58.70% slight, 22.58% moderate, and 19.35% severe), and 9.10% showed unexpected adverse effects (62.50% slight, 25.00% moderate, and 12.50% severe). Approximately 4.54% of the patients treated with Natalizumab interrupted the therapy. Overall, among all patients, 56.62% showed ameliorated condition, 32.53% had stable disease condition, and 10.85% worsened.

Conclusions

We provide a short overview of evidence, which may be useful to better characterize the efficacy and potential adverse effects correlated to Natalizumab therapy.

Natalizumab Treatment Modulates Peroxisome Proliferator-Activated Receptors Expression in Women with Multiple Sclerosis

Peroxisome Proliferator-Activated Receptors (PPAR) are transcription factors suggested to be involved in inflammatory lesions of autoimmune encephalomyelitis and multiple sclerosis (MS). Our objective was to assess whether Natalizumab (NTZ) therapy is associated with alterations of PPAR expression in MS patients. We analyzed gene expression of PPAR in peripheral blood mononuclear cells (PBMC) as well as blood inflammatory markers in women with MS previously medicated with first-line immunomodulators (baseline) and after NTZ therapy. No differences in PPARα, PPARβ/δ, PPARγ, and CD36 mRNA expression were found in PBMC between patients under baseline and healthy controls. At three months, NTZ increased PPARβ/δ mRNA (p = 0.009) in comparison to baseline, while mRNA expression of PPARγ and CD36 (a well-known PPAR target gene) was lower in comparison to healthy controls (p = 0.026 and p = 0.028, resp.). Although these trends of alterations remain after six months of therapy, the results were not statistically significant. Osteopontin levels were elevated in patients (p = 0.002) and did not change during the follow-up period of NTZ treatment. These results suggest that PPAR-mediated processes may contribute to the mechanisms of action of NTZ therapy.

Three immune-mediated disease models induced by Theiler's virus: Multiple sclerosis, seizures and myocarditis

Theiler's murine encephalomyelitis virus (TMEV) infection has been used as a viral model for multiple sclerosis (MS), as TMEV can induce chronic inflammatory demyelinating lesions with viral persistence in the spinal cord of SJL/J mice. In contrast, when C57BL/6 mice are infected with TMEV, the mice can clear the virus from the central nervous system (CNS), without viral persistence or demyelination, but develop seizures and hippocampal sclerosis, which has been used as a viral model for seizures/epilepsy. In the two TMEV-induced CNS disease models, not only viral infection, but also immune responses contribute to the pathogenesis. Interestingly, acquired immunity plays an effector role in the MS model, whereas innate immunity appears to contribute to the development of seizures. Recently, we have established the third TMEV-induced disease model, a mouse model for viral myocarditis, using C3H mice. TMEV-induced myocarditis is a triphasic disease, which mimics human myocarditis; phase I, mediated by viral replication in the heart and innate immunity; phase II, mediated by acquired immunity; and phase III, resulted from cardiac fibrosis. The genetic susceptibility to the aforementioned three models (MS, seizures and myocarditis) differs among mouse strains. We have compared and contrasted the three models induced by one single pathogen, TMEV, particularly in regard to the roles of T helper cells and natural killer T cells, which will give an insight into how interactions between the immune system and the host's genetic background determine the tissue tropism of virus and the development of virus-induced organ-specific immunopathology.