Interferon-β inhibits toll-like receptor 9 processing in multiple sclerosis

Antigen-specific immunotherapy via delivery of tolerogenic dendritic cells for multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system resulting from loss of immune tolerance. Many disease-modifying therapies for MS have broad immunosuppressive effects on peripheral immune cells, but this can increase risks of infection and attenuate vaccine-elicited immunity. A more targeted approach is to re-establish immune tolerance in an autoantigen-specific manner. This review discusses methods to achieve this, focusing on tolerogenic dendritic cells. Clinical trials in other autoimmune diseases also provide learnings with regards to clinical translation of this approach, including identification of autoantigen(s), selection of appropriate patients and administration route and frequency.

Tolerogenic Nano-/Microparticle Vaccines for Immunotherapy

Autoimmune diseases, allergies, transplant rejections, generation of antidrug antibodies, and chronic inflammatory diseases have impacted a large group of people across the globe. Conventional treatments and therapies often use systemic or broad immunosuppression with serious efficacy and safety issues. Tolerogenic vaccines represent a concept that has been extended from their traditional immune-modulating function to induction of antigen-specific tolerance through the generation of regulatory T cells. Without impairing immune homeostasis, tolerogenic vaccines dampen inflammation and induce tolerogenic regulation. However, achieving the desired potency of tolerogenic vaccines as preventive and therapeutic modalities calls for precise manipulation of the immune microenvironment and control over the tolerogenic responses against the autoantigens, allergens, and/or alloantigens. Engineered nano-/microparticles possess desirable design features that can bolster targeted immune regulation and enhance the induction of antigen-specific tolerance. Thus, particle-based tolerogenic vaccines hold great promise in clinical translation for future treatment of aforementioned immune disorders. In this review, we highlight the main strategies to employ particles as exciting tolerogenic vaccines, with a focus on the particles' role in facilitating the induction of antigen-specific tolerance. We describe the particle design features that facilitate their usage and discuss the challenges and opportunities for designing next-generation particle-based tolerogenic vaccines with robust efficacy to promote antigen-specific tolerance for immunotherapy.

The function of astrocytes and their role in neurological diseases

Astrocytes have countless links with neurons. Previously, astrocytes were only considered a scaffold of neurons; in fact, astrocytes perform a variety of functions, including providing support for neuronal structures and energy metabolism, offering isolation and protection and influencing the formation, function and elimination of synapses. Because of these functions, astrocytes play an critical role in central nervous system (CNS) diseases. The regulation of the secretiory factors, receptors, channels and pathways of astrocytes can effectively inhibit the occurrence and development of CNS diseases, such as neuromyelitis optica (NMO), multiple sclerosis, Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease. The expression of aquaporin 4 in AS is directly related to NMO and indirectly involved in the clearance of Aβ and tau proteins in AD. Connexin 43 has a bidirectional effect on glutamate diffusion at different stages of stroke. Interestingly, astrocytes reduce the occurrence of PD through multiple effects such as secretion of related factors, mitochondrial autophagy and aquaporin 4. Therefore, this review is focused on the structure and function of astrocytes and the correlation between astrocytes and CNS diseases and drug treatment to explore the new functions of astrocytes with the astrocytes as the target. This, in turn, would provide a reference for the development of new drugs to protect neurons and promote the recovery of nerve function.

Enhancing the functionality of self-assembled immune signals using chemical crosslinks

Multiple sclerosis (MS) is an autoimmune disease that develops when dysfunctional autoreactive lymphocytes attack the myelin sheath in the central nervous system. There are no cures for MS, and existing treatments are associated with unwanted side effects. One approach for treating MS is presenting distinct immune signals (i.e., self-antigen and immunomodulatory cues) to innate and adaptive immune cells to engage multiple signaling pathways involved in MS. We previously developed immune polyelectrolyte multilayer (iPEM) complexes built through layer-by-layer deposition of self-antigen - myelin oligodendrocyte glycoprotein (MOG) - and toll-like receptor antagonist, GpG to treat MS. Here, glutaraldehyde-mediated stable cross-links were integrated into iPEMs to load multiple classes of therapeutics. These cross-linked iPEMs maintain their immunological features, including the ability of GpG to blunt toll-like-receptor 9 signaling and MOG to expand T cells expressing myelin-specific T cell receptors. Lastly, we show that these functional assemblies can be loaded with a critical class of drug - mTOR inhibitors - associated with inducing regulatory T cells. These studies demonstrate the ability to incorporate small molecule drugs in reinforced self-assembled immune signals juxtaposed at high densities. This precision technology contributes new technologies that could drive antigen-specific immune response by simultaneously modulating innate and adaptive immunity.

Analysis of Differential TLR Activation in a Mouse Model of Multiple Sclerosis

Multiple sclerosis (MS) is a neurodegenerative and autoimmune disease affecting the central nervous system (CNS). The precise etiology of MS is still undeciphered, and signs and symptoms of the disease are varied and complex, ranging from axonal degeneration, synaptic, and neuronal loss to demyelination. Inflammation plays a critical role in determining the onset and the progression of MS, but there is still a lot of information missing before scientists come to understand what are the factors that contribute to the establishment of the neuroinflammation. Thus, various murine models, each representative of a specific hallmark of MS, are used to study the processes underlying the pathogenetic mechanisms of the disease in an attempt to find effective drugs for its treatment. Among the many causes of MS, viral infections appear to be one of the most prominent ones. In this scenario, the comprehension of the role of receptors activated upon the recognition of viral, and in general microbial, components in determining onset and progression of the neuroinflammation is of paramount importance. Toll-like receptors (TLRs) are evolutionarily conserved receptors that recognize several pathogen-associated molecular patterns (PAMPs), common structures of the pathogens, or the damage caused by the pathogens within the host. TLRs are thus directly involved in the regulation of inflammatory reactions and in the activation of the innate and, subsequently, the adaptive immune responses crucial for the elimination of infectious pathogens. The role of TLR activation in the development of MS is widely studied in various murine models of MS, as well as in MS patients. In this chapter, we will summarize the current knowledge about the contribution of TLRs to the development or progression of MS, and we will illustrate different methods commonly used for the investigation of the role of different TLRs in various murine models of the disease.

The immunology of multiple sclerosis

Our incomplete understanding of the causes and pathways involved in the onset and progression of multiple sclerosis (MS) limits our ability to effectively treat this complex neurological disease. Recent studies explore the role of immune cells at different stages of MS and how they interact with cells of the central nervous system (CNS). The findings presented here begin to question the exclusivity of an antigen-specific cause and highlight how seemingly distinct immune cell types can share common functions that drive disease. Innovative techniques further expose new disease-associated immune cell populations and reinforce how environmental context is critical to their phenotype and subsequent role in disease. Importantly, the differentiation of immune cells into a pathogenic state is potentially reversible through therapeutic manipulation. As such, understanding the mechanisms that provide plasticity to causal cell types is likely key to uncoupling these disease processes and may identify novel therapeutic targets that replace the need for cell ablation.

Immune cells transcriptome-based drug repositioning for multiple sclerosis

Objective

Finding target genes and target pathways of existing drugs for drug repositioning in multiple sclerosis (MS) based on transcriptomic changes in MS immune cells.

Materials and Methods

Based on transcriptome data from Gene Expression Omnibus (GEO) database, differentially expressed genes (DEGs) in MS patients without treatment were identified by bioinformatics analysis according to the type of immune cells, as well as DEGs in MS patients before and after drug administration. Hub target genes of the drug for MS were analyzed by constructing the protein-protein interaction network, and candidate drugs targeting 2 or more hub target genes were obtained through the connectivity map (CMap) database and Drugbank database. Then, the enriched pathways of MS patients without treatment and the enriched pathways of MS patients before and after drug administration were intersected to obtain the target pathways of the drug for MS, and the candidate drugs targeting 2 or more target pathways were obtained through Kyoto Encyclopedia of Genes and Genomes (KEGG) database.

Results

We obtained 50 hub target genes for CD4⁺ T cells in Fingolimod for MS, 15 hub target genes for Plasmacytoid dendritic cells (pDCs) and 7 hub target genes for Peripheral blood mononuclear cells (PBMC) in interferon-β (IFN-β) for MS. 6 candidate drugs targeting two or more hub targets (Fostamatinib, Copper, Artenimol, Phenethyl isothiocyanate, Aspirin and Zinc) were obtained. In addition, we obtained 4 target pathways for CD19⁺ B cells and 15 target pathways for CD4⁺ T cells in Fingolimod for MS, 7 target pathways for pDCs and 6 target pathways for PBMC in IFN-β for MS, most of which belong to the immune system and viral infectious disease pathways. We obtained 69 candidate drugs targeting two target pathways.

Conclusion

We found that applying candidate drugs that target both the “PI3K-Akt signaling pathway” and “Chemokine signaling pathway” (e.g., Nemiralisib and Umbralisib) or applying tyrosine kinase inhibitors (e.g., Fostamatinib) may be potential therapies for the treatment of MS.

Role of Toll-Like Receptors in Neuroimmune Diseases: Therapeutic Targets and Problems

Toll-like receptors (TLRs) are a class of proteins playing a key role in innate and adaptive immune responses. TLRs are involved in the development and progression of neuroimmune diseases via initiating inflammatory responses. Thus, targeting TLRs signaling pathway may be considered as a potential therapy for neuroimmune diseases. However, the role of TLRs is elusive and complex in neuroimmune diseases. In addition to the inadequate immune response of TLRs inhibitors in the experiments, the recent studies also demonstrated that partial activation of TLRs is conducive to the production of anti-inflammatory factors and nervous system repair. Exploring the mechanism of TLRs in neuroimmune diseases and combining with developing the emerging drug may conquer neuroimmune diseases in the future. Herein, we provide an overview of the role of TLRs in several neuroimmune diseases, including multiple sclerosis, neuromyelitis optica spectrum disorder, Guillain-Barré syndrome and myasthenia gravis. Emerging difficulties and potential solutions in clinical application of TLRs inhibitors will also be discussed.

Cerebrospinal fluid inflammatory biomarkers predicting interferon-beta response in MS patients

Background and Aims:

Interferon beta (IFNb) is a safe first-line drug commonly used for relapsing-remitting (RR)-MS. Nevertheless, a considerable proportion of patients do not respond to IFNb treatment. Therefore, until now, a number of studies have investigated various markers that could predict the patients who would respond to IFNb therapy. The objective of this study was to identify reliable biomarkers to predict the efficacy of IFNb treatment in MS.

Methods:

In a group of 116 patients with clinically isolated syndrome (CIS) and RR-MS, we explored the association between CSF detectability of a large set of proinflammatory and anti-inflammatory molecules at the time of diagnosis and response to IFNb after the first year of treatment. The absence of clinical relapses, radiological activity and disability progression (NEDA-3) was assessed at the end of 1-year follow up. The results were compared with those obtained in additional groups of CIS and RR-MS patients treated with other first-line drugs (dimethyl fumarate and glatiramer acetate).

Results:

CSF undetectability of macrophage inflammatory protein (MIP)-1α was the main predictor of reaching NEDA-3 status after 1 year of IFNb treatment. Moreover, detectable platelet-derived growth factor (PDGF) was associated with higher probability of reaching NEDA-3. Conversely, no associations with the CSF molecules were found in the two other groups of patients treated either with dimethyl fumarate or with glatiramer acetate.

Conclusion:

MIP-1α and PDGF could potentially represent suitable CSF biomarkers able to predict response to IFNb in MS.

Inflammatory Role of TLR-MyD88 Signaling in Multiple Sclerosis

Multiple sclerosis (MS) is a neuro-autoimmune and neurodegenerative disorder leading to chronic inflammation, demyelination, axonal, and neuronal loss in the central nervous system (CNS). Despite intense research efforts, the pathogenesis of MS still remains unclear. Toll-like receptors (TLRs) are a family of type I transmembrane receptors that play a crucial role in the innate immune response. Myeloid differentiation factor 88 (MyD88) is the adaptor of major TLRs. It has been widely considered that the TLR-MyD88 signaling pathway plays an important role in the occurrence and development of autoimmune disease. Data have revealed that the TLR-MyD88 signaling may be involved in the pathogenesis of MS and experimental autoimmune encephalomyelitis (EAE), an animal model for MS, by regulating the antigen presentation of dendritic cells, the integrity of blood-brain barrier (BBB), and the activation of T cells and B cells. Here, we summarize the role of TLRs and MyD88 in MS and discuss the possible therapies that are based on these molecules.

Toll-like receptors in the pathogenesis of neuroinflammation

Toll-like receptors (TLRs) are discovered as crucial pattern recognition receptors (PRRs) involved in the recognition of pathogen-associated molecular patterns (PAMPs). Later studies showed their involvement in the recognition of various damage/danger-associated molecular patterns (DAMPs) generated by host itself. Thus, TLRs are capable of recognizing wide-array of patterns/molecules derived from pathogens and host as well and initiating a proinflammatory immune response through the activation of NF-κB and other transcription factors causing synthesis of proinflammatory molecules. The process of neuroinflammation is seen under both sterile and infectious inflammatory diseases of the central nervous system (CNS) and may lead to the development of neurodegeneration. The present article is designed to highlight the importance of TLRs in the pathogenesis of neuroinflammation under diverse conditions. TLRs are expressed by various immune cells present in CNS along with neurons. However out of thirteen TLRs described in mammals, some are present and active in these cells, while some are absent and are described in detail in main text. The role of various immune cells present in the brain and their role in the pathogenesis of neuroinflammation depending on the type of TLR expressed is described. Thereafter the role of TLRs in bacterial meningitis, viral encephalitis, stroke, Alzheimer's disease (AD), Parkinson's disease (PD), and autoimmune disease including multiple sclerosis (MS) is described. The article is designed for both neuroscientists needing information regarding TLRs in neuroinflammation and TLR biologists or immunologists interested in neuroinflammation.

Engineering release kinetics with polyelectrolyte multilayers to modulate TLR signaling and promote immune tolerance

Autoimmune disorders, such as multiple sclerosis and type 1 diabetes, occur when immune cells fail to recognize "self" molecules. Recently, studies have revealed aberrant inflammatory signaling through pathogen sensing pathways, such as toll-like receptors (TLRs), during autoimmune disease. Therapeutic inhibition of these pathways might attenuate disease development, skewing disease-causing inflammatory cells towards cell types that promote tolerance. Delivering antagonistic ligands to a TLR upstream of an inflammatory signaling cascade, TLR9, has demonstrated exciting potential in a mouse model of MS; however, strategies that enable sustained delivery could reduce the need for repeated administration or enhance therapeutic efficacy. We hypothesized that GpG - an oligonucleotide TLR9 antagonist - which is inherently anionic, could be self-assembled into polyelectrolyte multilayers (PEMs) with a cationic, degradable poly(β-amino ester) (Poly1). We hypothesized that degradable Poly1/GpG PEMs could promote sustained release of GpG and modulate inflammatory immune cell functions. Here we demonstrate layer-by-layer assembly of degradable PEMs, as well as subsequent degradation and release of GpG. Following assembly and release, GpG maintains the ability to reduce dendritic cell activation and inflammatory cytokine secretion, restrain TLR9 signaling, and polarize myelin specific T cells towards regulatory phenotypes and functions in primarily immune cells. These results indicate that degradable PEMs may be able to promote tolerogenic immune function in the context of autoimmunity.

Engineering self-assembled materials to study and direct immune function

The immune system is an awe-inspiring control structure that maintains a delicate and constantly changing balance between pro-immune functions that fight infection and cancer, regulatory or suppressive functions involved in immune tolerance, and homeostatic resting states. These activities are determined by integrating signals in space and time; thus, improving control over the densities, combinations, and durations with which immune signals are delivered is a central goal to better combat infectious disease, cancer, and autoimmunity. Self-assembly presents a unique opportunity to synthesize materials with well-defined compositions and controlled physical arrangement of molecular building blocks. This review highlights strategies exploiting these capabilities to improve the understanding of how precisely-displayed cues interact with immune cells and tissues. We present work centered on fundamental properties that regulate the nature and magnitude of immune response, highlight pre-clinical and clinical applications of self-assembled technologies in vaccines, cancer, and autoimmunity, and describe some of the key manufacturing and regulatory hurdles facing these areas.

Design of Polyelectrolyte Multilayers to Promote Immunological Tolerance

Recent studies demonstrate that excess signaling through inflammatory pathways (e.g., toll-like receptors, TLRs) contributes to the pathogenesis of human autoimmune diseases, including lupus, diabetes, and multiple sclerosis (MS). We hypothesized that codelivery of a regulatory ligand of TLR9, GpG oligonucleotide, along with myelin-the "self" molecule attacked in MS-might restrain the pro-inflammatory signaling typically present during myelin presentation, redirecting T cell differentiation away from inflammatory populations and toward tolerogenic phenotypes such as regulatory T cells. Here we show that myelin peptide and GpG can be used as modular building blocks for co-assembly into immune polyelectrolyte multilayers (iPEMs). These nanostructured capsules mimic attractive features of biomaterials, including tunable cargo loading and codelivery, but eliminate all carriers and synthetic polymers, components that often exhibit intrinsic inflammatory properties that could exacerbate autoimmune disease. In vitro, iPEMs assembled from myelin and GpG oligonucleotide, but not myelin and a control oligonucleotide, restrain TLR9 signaling, reduce dendritic cell activation, and polarize myelin-specific T cells toward tolerogenic phenotype and function. In mice, iPEMs blunt myelin-triggered inflammatory responses, expand regulatory T cells, and eliminate disease in a common model of MS. Finally, in samples from human MS patients, iPEMs bias myelin-triggered immune cell function toward tolerance. This work represents a unique opportunity to use PEMs to regulate immune function and promote tolerance, supporting iPEMs as a carrier-free platform to alter TLR function to reduce inflammation and combat autoimmunity.

Close Encounters of the First Kind: Innate Sensors and Multiple Sclerosis

Although autoimmune diseases by definition imply adaptive immune system pathologies, growing evidence points to the relevance of innate receptors in modulating the initiation and progression of the autoreactive response. Multiple sclerosis (MS) is a chronic autoimmune disease characterised by central nervous system (CNS) demyelination, inflammation and axonal damage, in which the role of several pathogens such as herpes viruses have long been described as potential triggers. Encounters of these pathogens with altered innate receptors in susceptible individuals might drive pathological autoreactivity and inflammation, overcoming tolerance and causing subsequent CNS damage. In particular, functional and genetic studies reveal that Toll-like receptor (TLR) 2 and the Nod-like receptor (NLR) P3 could be involved in MS pathogenesis, whereas TLR3, the triggering receptor expressed on myeloid cells (TREM)-2 and the C-type lectin receptors (CLRs) MBL and MASP-3 would have a putative protective role. A better understanding of these interactions will provide important insights into the aetiopathogenesis of MS and could help design potential targets for novel therapies.

Immunologic and MRI markers of the therapeutic effect of IFN-β-1a in relapsing-remitting MS

OBJECTIVES

To assess potential roles of effector cells and immunologic markers in demyelinating CNS lesion formation, and their modulation by interferon β-1a (IFN-β-1a).

METHODS

Twenty-three patients with relapsing-remitting multiple sclerosis (RRMS) received IFN-β-1a for 6 months. Immunologic marker results were correlated with brain MRI lesion volumes, and volumes of normal-appearing brain tissue (NABT) with decreasing or increasing voxel-wise magnetization transfer ratio (VW-MTR), suggestive of demyelination and remyelination, respectively.

RESULTS

Baseline expression of Th22 cell transcription factor aryl hydrocarbon receptor (AHR) and interleukin (IL)-17F, and percentages of IL-22-expressing CD4(+) and CD8(+) cells, were significantly higher in patients vs 15 healthy controls; IL-4 in CD4(+) cells was lower. Baseline percentage of IL-22-producing CD8(+) cells positively correlated with T2 lesion volumes, while percentage of IL-17A-producing CD8(+) cells positively correlated with T2 and T1 lesion volumes. IFN-β-1a induced reductions in transcription factor AHR, T-bet, and retinoic acid-related orphan nuclear hormone receptor C (RORc) gene expression, while it increased GATA3's expression in CD4(+) cells. Percentages of IL-22-, IL-17A-, and IL-17F-expressing T cells significantly decreased following treatment. Increased percentages of IL-10-expressing CD4(+) and CD8(+) cells correlated with greater NABT volume with increasing VW-MTR, while decreased percentage of IL-17F-expressing CD4(+) cells positively correlated with decreased NABT volume with decreasing VW-MTR.

CONCLUSIONS

Findings indicate that IFN-β-1a suppresses Th22 and Th17 cell responses, which were associated with decreased MRI-detectable demyelination.

CLASSIFICATION OF EVIDENCE

This pilot study provides Class III evidence that reduced Th22 and Th17 responses are associated with decreased demyelination following IFN-β-1a treatment in patients with RRMS.

IFN-β Therapy Regulates TLR7-Mediated Response in Plasmacytoid Dendritic Cells of Multiple Sclerosis Patients Influencing an Anti-Inflammatory Status

Plasmacytoid dendritic cells (pDCs) display altered immune-phenotype in multiple sclerosis (MS) patients and are found actively recruited in postmortem MS brain lesions, implying that their immune regulation may represent an important aspect of MS pathogenesis. Because of the reported Toll-like receptor 7 (TLR7) implication in autoimmunity, in this study we characterized how IFN-β therapy impacts on pDC activation to TLR7 triggering in MS patients, aspect only poorly investigated so far. In vivo IFN-β administration regulates pDC functions in TLR7-treated peripheral blood mononuclear cell (PBMC) cultures differently from what is observed in isolated cells, suggesting that IFN-β may activate inhibitory mechanisms in MS peripheral blood involved in turning off pDC response to dampen the ongoing inflammation. Indeed, IL-10, a key regulatory cytokine found increased upon TLR7 stimulation in in vivo IFN-β-exposed PBMCs, directly reduced pDC-mediated IFN-α production. IFN-β therapy also shaped T-cell responses by decreasing TLR7-induced pDC maturation and inducing T-cell inhibitory molecules. Accordingly, raised pDC-induced IL-27 and decreased IL-23 expression, together with high IL-10 level, contribute to inhibit Th17 cell differentiation. Our study uncovered a role for IFN-β in the regulation of TLR7-mediated pDC responses in MS toward an anti-inflammatory phenotype opening new opportunities to better understand mechanisms of action of this drug in controlling MS immunopathogenesis.

The conundrum of interferon-β non-responsiveness in relapsing-remitting multiple sclerosis

A series of controlled clinical trials have shown that exogenous interferon-beta (IFN-β) benefits patients with relapsing-remitting multiple sclerosis (RRMS) by reducing relapse rate, disability progression, and the formation of new brain and spinal cord lesions on magnetic resonance imaging (MRI) scans. Unfortunately, however, the effectiveness of IFN-β is limited in this setting by the occurrence of treatment non-responsiveness in nearly 25% of patients. Furthermore, clinicians who care for RRMS patients remain unable to accurately identify IFN-β non-responders prior to the initiation of therapy, causing delays in the use of alternative treatments and sometimes requiring that patients turn to medications with more significant side effects to control their disease. Progress has been made toward understanding how both endogenous and exogenous IFN-β act to slow RRMS as well as the related mouse model, experimental autoimmune encephalomyelitis (EAE). Most studies point to its inhibitory actions on circulating immune cells as being important for suppressing both disorders, but multiple potential target cells and inflammatory pathways have been implicated and those essential to confer its benefits remain undefined. This review focuses on the role of both endogenous and exogenous IFN-β in RRMS, paying particular attention to the issue of why certain individuals appear refractory to its disease-modifying effects. A continued goal in this field remains the identification of a convenient biomarker that accurately predicts IFN-β treatment non-responsiveness in individual RRMS patients. Development of such an assay will allow clinicians to customize therapy for patients with this complex disorder.

Cell-based modulation of autoimmune responses in multiple sclerosis and experimental autoimmmune encephalomyelitis: therapeutic implications

Multiple sclerosis (MS) is a prototypic autoimmune inflammatory disorder of the central nervous system (CNS). MS pathogenesis is a complex phenomenon that is influenced by genetic and environmental factors that lead to the dysregulation of immune homeostasis and tolerance. It has been shown that pathogenic T lymphocyte subsets, such as T helper 1 (Th1) and Th17 cells, play a crucial role in the autoimmune cascade influencing disease initiation, progression and subsequent tissue damage during MS. On the other hand, several mechanisms have been described in both patients and animal models of MS with the potential to modulate myelin-specific autoimmune responses and to facilitate amelioration of disease pathology. To this end, regulatory T cells (Tregs) are considered to be a powerful cell subset not only in the maintenance of homeostasis but also in the re-establishment of tolerance. Along these lines, other cell subsets such as dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs), γδ T cells and natural killer (NK) cells have been shown to regulate the autoimmune response in the CNS under certain circumstances. This review will attempt to summarize the relevant knowledge of the regulatory mechanisms exerted by immune cells in MS that could hold the promise for the design of novel therapeutic strategies.

Decreased Dicer expression is linked to increased expression of co-stimulatory molecule CD80 on B cells in multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is an immune-mediated inflammatory disease of the central nervous system. B cells have been strongly implicated in disease pathogenesis based on clinical trials with B-cell ablation. There is a growing body of evidence linking microRNAs with regulation of the immune system. Dicer, a key enzyme involved in microRNA biogenesis, is necessary for normal B-cell function.

OBJECTIVE

We aimed to determine whether Dicer expression is impaired in B cells and is linked to increased expression co-stimulatory molecules in patients with MS.

METHODS

B cells were separated from blood samples of MS patients and healthy subjects. Expression of Dicer and co-stimulatory molecules CD80 and CD86 was tested. The effect of Dicer modulation on CD80 and CD86 expression in B cells was studied.

RESULTS

Dicer expression was decreased in B cells but not in monocytes of patients with MS compared with healthy subjects. CD80 and CD86 expression was increased on B cells of MS patients compared with healthy subjects. Inhibition of Dicer expression in B cells by small interfering RNA led to increased expression of CD80.

CONCLUSION

Dicer expression is decreased and is mechanistically linked to increased expression of co-stimulatory molecule CD80 in B cells of patients with MS. This may contribute to activation of immune responses in MS.

IFN-β and multiple sclerosis: cross-talking of immune cells and integration of immunoregulatory networks

Multiple sclerosis (MS) is characterized by autoimmune inflammation affecting the central nervous system and subsequent neurodegeneration. Historically, damage was thought to be mediated exclusively by auto-antigen-activated pro-inflammatory T cells. However, more recently, we are gaining increasing knowledge on the pathogenic role played in MS by B cells, dendritic cells and monocytes. IFN-β therapy was one the first approved therapy for MS for its ability to reduce relapse rate and MRI lesion activity and to significantly decrease risk of disability progression. IFN-β-mediated mechanisms of action, even if not completely understood, mainly rely on its multifaceted pleiotropic effects resulting in sustained anti-inflammatory properties directed toward almost every immune cell type. Here, we will discuss in detail literature data characterizing the pathogenic activity of the different immune cell subsets involved in MS pathogenesis and how IFN-β therapy regulates their function by modulating bystander responses. We believe that the effectiveness of this drug in MS treatment, even if in use for a long time, can unveil new insights on this disease and still teach a lesson to researchers in the MS field.

MMP-9 expression is increased in B lymphocytes during multiple sclerosis exacerbation and is regulated by microRNA-320a

B cells are necessary to maintain disease activity in relapsing multiple sclerosis (MS) and produce matrix metallopeptidase-9 (MMP-9), which disrupts the blood-brain barrier. MMP-9 protein expression was increased and expression of microRNA-320a (miR-320a), which targets MMP-9 mRNA, was significantly decreased in B lymphocytes of MS patients during a disease relapse compared to remission. Functional significance of these findings was demonstrated by transfecting human B lymphocytes with miR-320a inhibitor, which led to increased MMP-9 expression and secretion. In summary, expression of miR-320a is decreased in B cells of MS patients and may contribute to increased blood-brain barrier permeability and neurological disability.

IFN-β and multiple sclerosis: from etiology to therapy and back

Several immunomodulatory treatments are currently available for relapsing-remitting forms of multiple sclerosis (RRMS). Interferon beta (IFN) was the first therapeutic intervention able to modify the course of the disease and it is still the most used first-line treatment in RRMS. Though two decades have passed since IFN-β was introduced in the management of MS, it remains a valid approach because of its good benefit/risk profile. This is witnessed by new efforts of pharmaceutical industry to improve this line: a PEGylated form of subcutaneous IFN-β 1a, (Plegridy(®)) with a longer half-life, has been recently approved in RRMS. This review will survey the various stages of the use of type I IFN in MS, with special attention to the effect of the treatment on the supposed viral etiologic factors associated to the disease. The antiviral activities of IFN (that initially prompted its use as immunomodulatory agent in MS), and the mounting evidences in favor of a viral etiology in MS, allowed us to outline a re-appraisal from etiology to therapy and back.

Accumulation and therapeutic modulation of 6-sulfo LacNAc(+) dendritic cells in multiple sclerosis

Objective:

To examine the potential role of 6-sulfo LacNAc⁺ (slan) dendritic cells (DCs) displaying pronounced proinflammatory properties in the pathogenesis of multiple sclerosis (MS).

Methods:

We determined the presence of slanDCs in demyelinated brain lesions and CSF samples of patients with MS. In addition, we explored the impact of methylprednisolone, interferon-β, glatiramer acetate, or natalizumab on the frequency of blood-circulating slanDCs in patients with MS. We also evaluated whether interferon-β modulates important proinflammatory capabilities of slanDCs.

Results:

SlanDCs accumulate in highly inflammatory brain lesions and are present in the majority of CSF samples of patients with MS. Short-term methylprednisolone administration reduces the percentage of slanDCs in blood of patients with MS and the proportion of tumor necrosis factor-α– or CD150-expressing slanDCs. Long-term interferon-β treatment decreases the percentage of blood-circulating slanDCs in contrast to glatiramer acetate or natalizumab. Furthermore, interferon-β inhibits the secretion of proinflammatory cytokines by slanDCs and their capacity to promote proliferation and differentiation of T cells.

Conclusion:

Accumulation of slanDCs in highly inflammatory brain lesions and their presence in CSF indicate that slanDCs may play an important role in the immunopathogenesis of MS. The reduction of blood-circulating slanDCs and the inhibition of their proinflammatory properties by methylprednisolone and interferon-β may contribute to the therapeutic efficiency of these drugs in patients with MS.

Immunomodulatory activity of interferon-beta

Multiple sclerosis (MS) is a complex disorder of the central nervous system that appears to be driven by a shift in immune functioning toward excess inflammation that results in demyelination and axonal loss. Beta interferons were the first class of disease-modifying therapies to be approved for patients with MS after treatment with this type I interferon improved the course of MS on both clinical and radiological measures in clinical trials. The mechanism of action of interferon-beta appears to be driven by influencing the immune system at many levels, including antigen-presenting cells, T cells, and B cells. One effect of these interactions is to shift cytokine networks in favor of an anti-inflammatory effect. The pleiotropic mechanism of action may be a critical factor in determining the efficacy of interferon-beta in MS. This review will focus on select immunological mechanisms that are influenced by this type I cytokine.

Plasmacytoid dendritic cells and autoimmune inflammation

Plasmacytoid dendritic cells (pDC) are a sub-population of dendritic cells (DC) that produce large amounts of type I interferon (IFN) in response to nucleic acids that bind and activate toll-like-receptor (TLR)9 and TLR7. Type I IFN can regulate the function of B, T, DC, and natural killer (NK) cells and can also alter the residence time of leukocytes within lymph nodes. Activated pDC can also function as antigen presenting cells (APC) and have the potential to prime and differentiate T cells into regulatory or inflammatory effector cells, depending on the context. In this review we discuss pDC ontogeny, function, trafficking, and activation. We will also examine how pDC can potentially be involved in regulating immune responses in the periphery as well as within the central nervous system (CNS) during multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE).

Targeting innate receptors with MIS416 reshapes Th responses and suppresses CNS disease in a mouse model of multiple sclerosis

Modification of the innate immune cell environment has recently been recognized as a viable treatment strategy for reducing autoimmune disease pathology. MIS416 is a microparticulate immune response modifier that targets myeloid cells, activating cytosolic receptors NOD2 and TLR9, and has completed a phase 1b/2a trial for the treatment of secondary progressive multiple sclerosis. Using a mouse model of multiple sclerosis, we are investigating the pathways by which activation of TLR9 and NOD2 may modify the innate immune environment and the subsequent T cell-mediated autoimmune responses. We have found that MIS416 has profound effects on the Th subset balance by depressing antigen-specific Th1, Th17, and Th2 development. These effects coincided with an expansion of specific myeloid subpopulations and increased levels of MIS416-stimulated IFN-γ by splenocytes. Additionally, systemic IFN-γ serum levels were enhanced and correlated strongly with disease reduction, and the protective effect of MIS416 was abrogated in IFN-γ-deficient animals. Finally, treatment of secondary progressive MS patients with MIS416 similarly elevated the levels of IFN-γ and IFN-γ-associated proteins in the serum. Together, these studies demonstrate that administration of MIS416, which targets innate cells, reshapes autoimmune T cell responses and leads to a significant reduction in CNS inflammation and disease.

Multiple sclerosis: modulation of toll-like receptor (TLR) expression by interferon-β includes upregulation of TLR7 in plasmacytoid dendritic cells

Interferon-β is an established treatment for patients with multiple sclerosis (MS) but its mechanisms of action are not well understood. Viral infections are a known trigger of MS relapses. Toll-like receptors (TLRs) are key components of the innate immune system, which sense conserved structures of viruses and other pathogens. Effects of interferon-β on mRNA levels of all known human TLRs (TLR1-10) and the TLR adaptor molecule MyD88 were analyzed in peripheral blood mononuclear cells (PBMCs) of healthy donors by quantitative real-time PCR and by transcriptome analysis in PBMCs of 25 interferon-β-treated patients with relapsing-remitting MS. Regulation of TLR protein expression by interferon-β was investigated by flow cytometry of leukocyte subsets of healthy subjects and of untreated, interferon-β-, or glatiramer acetate-treated patients with MS. Interferon-β specifically upregulated mRNA expression of TLR3, TLR7, and MyD88 and downregulated TLR9 mRNA in PBMCs of healthy donors as well as in PBMCs of patients with MS. Plasmacytoid dendritic cells (pDCs) were identified as the major cell type responding to interferon-β with increased expression of TLR7 and MyD88 protein. In line with this, expression of TLR7 protein was increased in pDCs of interferon-β-treated, but not untreated or glatiramer acetate-treated patients with MS. Interferon-β-induced upregulation of TLR7 in pDCs is of functional relevance since pre-treatment of PBMCs with interferon-β resulted in a strongly increased production of interferon-α upon stimulation with the TLR7 agonist loxoribine. Flow cytometry confirmed pDCs as the cellular source of interferon-α production induced by activation of TLR7. Thus, upregulation of TLR7 in pDCs and a consequently increased activation of pDCs by TLR7 ligands represents a novel immunoregulatory mechanism of interferon-β. We hypothesize that this mechanism could contribute to a reduction of virus-triggered relapses in patients with MS.

Innate immune responses in the CNS: role of toll-like receptors, mechanisms, and therapeutic opportunities in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS), which is considered immune-mediated. Our knowledge of innate immune mechanisms in the CNS and their implications for pathogenesis and treatment of multiple sclerosis (MS) are limited, particularly if compared with the body of literature on adaptive immune mechanisms. There is, however, growing understanding of the workings of the innate immune system and accordingly, of its potential role in driving immune-mediated pathology. Such mechanisms will be discussed in this review along with potential therapeutic opportunities. These may require blocking pathogenic innate immunity and in some cases, promoting its protective effects.

Plasmacytoid dendritic cells and immunotherapy in multiple sclerosis

Plasmacytoid dendritic cells (pDCs) are specialized APCs implicated in the pathogenesis of many human diseases. Compared with other peripheral blood mononuclear cells, pDCs express a high level of TLR9, which recognizes viral DNA at the initial phase of viral infection. Upon stimulation, these cells produce large amounts of type I interferon and other proinflammatory cytokines and are able to prime T lymphocytes. Thus, pDCs regulate innate and adaptive immune responses. This article reviews select aspects of pDC biology relevant to the disease pathogenesis and immunotherapy in multiple sclerosis. Many unresolved questions remain in this area, promising important future discoveries in pDC research.

Role of toll-like receptors in multiple sclerosis

Multiple Sclerosis (MS) is an autoimmune disease in which Central Nervous System (CNS) lesions result from perivascular immune cell infiltration associated with damage to myelin, oligodendrocytes and neurons. CNS autoimmunity and its regulation are dominated by the inflammatory cytokines IL17 and IFNγ, and the opposing regulatory cytokines IL10 and the type I IFNs. Toll-like receptors (TLR) play a critical role in modulating cytokine and chemokine secretion in response to exogenous Pathogen Associated to Molecular Patterns and endogenous Danger-Associated to Molecular Patterns. Here, we systematically examine the evidence that TLR play a major role in the initiation disease, the triggering of relapses, and regulation of CNS damage. Data from human studies are supported analyses of a variety of animal models, including Experimental Autoimmune Encephalomyelitis in TLR-deficient mice.

Dendritic cells in multiple sclerosis: key players in the immunopathogenesis, key players for new cellular immunotherapies?

Many studies have demonstrated the role of the adaptive immune system in the pathogenesis of multiple sclerosis (MS). Recent data suggest that dendritic cells (DCs), which are innate immune cells, also contribute to the pathogenesis of MS. In patients with MS, DCs are abundantly present in brain lesions, and display an altered phenotype and/or function as compared with this in healthy controls. DCs are thus in the position to pathologically influence the effector function of (auto-reactive) T and B cells. Interestingly, current first-line immunomodulating therapies for MS have been shown to restore DC phenotype and function, albeit in a non-specific manner. To date, clinical trials using agents specifically targeting DC function are ongoing. Moreover, several studies worldwide are currently investigating possible strategies to develop tolerogenic DCs. This review focuses on the phenotypic and functional alterations of conventional DCs and plasmacytoid DCs in patients with MS. Furthermore, we discuss how existing immunomodulating therapies for MS patients affect DC function and address future perspectives in the development of immunotherapies specifically targeting DCs.

Multiple sclerosis-linked and interferon-beta-regulated gene expression in plasmacytoid dendritic cells

The cause of multiple sclerosis (MS) is not known and the mechanism of interferon-beta, a disease-modifying treatment, is not well-understood. We studied gene expression in plasmacytoid dendritic cells (pDCs), antigen-presenting cells implicated in MS pathogenesis. PDCs were separated from healthy donors and MS patients at two time points: before and after initiation of treatment with interferon-beta. Expression of selected MS-linked and interferon-beta-regulated genes was validated with single assays. We have identified 60 genes which were abnormally expressed in MS patients and were corrected after treatment. These genes could be studied as potential MS biomarkers and possible therapeutic targets in MS.

Pharmacogenomics and multiple sclerosis: moving toward individualized medicine

Notwithstanding the availability of disease-modifying treatments including interferon-β, glatiramer acetate, and natalizumab, a considerable proportion of multiple sclerosis (MS) patients experience continued progression of disease, clinical relapses, disease activity on MRI, and adverse effects. Application of gene expression, proteomic or genomic approaches is universally accepted as a suitable strategy toward the identification of biomarkers with predictive value for beneficial/poor clinical response to therapy and treatment risks. This review focuses on recent progress in research on the pharmacogenomics of disease-modifying therapies for MS. Although MS drug response biomarkers are not yet routinely implemented in the clinic, the diversity of reported, promising molecular markers is rapidly increasing. Even though most of these markers await further validation, given time, this research is likely to empower neurologists with an enhanced armamentarium to facilitate rational decisions on therapy and patient management.

Outcomes of toll-like receptors' antagonism in steroid-resistant optic neuritis; a pilot study

BACKGROUND

To investigate the safety and outcomes of off-label immunomodulator Mycobacterium w. (Mw), a TLR 9 antagonist in steroid-resistant idiopathic unilateral optic neuritis.

METHODS

Case series. Eight patients with documented idiopathic unilateral optic neuritis who did not improve with methyl prednisolone followed by oral steroids as per the Optic Neuritis Treatment Trial (ONTT) were administered Mw 5 ml in 500 ml normal saline, 30 days after the last of dose of steroids had been administered. The dose was repeated at 3 months. Outcome measures monitoring the change in the best-corrected visual acuity (BCVA), pupillary reaction, colour vision, visual field (VF) examination (when possible), fundus examination and photography, visually evoked potential (VEP) testing. BCVA, pupillary reaction, and color vision were monitored immediately prior to steroid therapy, on days 1 and 7 post steroid therapy, pre Mw administration (i.e., 30 days after the last dose of steroids had been completed) and post Mw administration on days 1, 7, 30, 90, 120 and 180. VF, VEP and fundus photography was performed immediately prior to steroid administration, 30 days after the last dose of steroids (i.e., immediately prior to Mw), and days 30, 90,120 and 180 post Mw administration.

RESULTS

There were five females and three males in an age range of 30-54 years. Six patients were available for follow-up at 6 months. All patients showed improvement in visual acuity, colour vision & pupillary reaction. Visual field monitoring was possible in four patients; all four had a centrocecal scotoma that persisted post steroid therapy but resolved 1 month post Mw therapy. Three out of five patients who had disc edema were available for all follow-ups, and showed resolution of disc edema post Mw therapy. The disc edema had persisted post steroid therapy. No adverse events were seen. The 2nd dose did not improve any of the said parameters. There was no recurrence of the disease up to the end of the follow-up period.

CONCLUSIONS

Mw appears to improve steroid resistant optic neuritis; future randomized clinical trials would help affirm this observation.

The mechanism of action of interferon-β in relapsing multiple sclerosis

Multiple sclerosis (MS) is characterized by autoimmune inflammation and subsequent neurodegeneration. It is believed that early in the disease course, proinflammatory T cells that are activated in the periphery by antigen presentation cross the blood-brain barrier (BBB) into the CNS directed by various chemotaxic agents. However, to date, there has been no formal demonstration of a specific precipitating antigen. Once inside the CNS, activated T cells including T helper-1 (T(h)1), T(h)17, γδ and CD8+ types are believed to secrete proinflammatory cytokines. Decreased levels of T(h)2 cells also correlate with relapses and disease progression in MS, since T(h)2-derived cytokines are predominantly anti-inflammatory. In healthy tissue, inflammatory effects are opposed by specific subsets of regulatory T cells (T(regs)) including CD4+, CD25+ and FoxP3+ cells that have the ability to downregulate the activity of proinflammatory T cells, allowing repair and recovery to generally follow inflammatory insult. Given their function, the pathogenesis of MS most likely involves deficits of T(reg) function, which allow autoimmune inflammation and resultant neurodegeneration to proceed relatively unchecked. Interferons (IFNs) are naturally occurring cytokines possessing a wide range of anti-inflammatory properties. Recombinant forms of IFNβ are widely used as first-line treatment in relapsing forms of MS. The mechanism of action of IFNβ is complex, involving effects at multiple levels of cellular function. IFNβ appears to directly increase expression and concentration of anti-inflammatory agents while downregulating the expression of proinflammatory cytokines. IFNβ treatment may reduce the trafficking of inflammatory cells across the BBB and increase nerve growth factor production, leading to a potential increase in neuronal survival and repair. IFNβ can also increase the number of CD56bright natural killer cells in the peripheral blood. These cells are efficient producers of anti-inflammatory mediators, and may have the ability to curb neuron inflammation. The mechanistic effects of IFNβ manifest clinically as reduced MRI lesion activity, reduced brain atrophy, increased time to reach clinically definite MS after the onset of neurological symptoms, decreased relapse rate and reduced risk of sustained disability progression. The mechanism of action of IFNβ in MS is multifactorial and incompletely understood. Ongoing and future studies will increase our understanding of the actions of IFNβ on the immune system and the CNS, which will in turn aid advances in the management of MS.