The initiation of the autoimmune response in multiple sclerosis

Dynamical footprint of cross-reactivity in a human autoimmune T-cell receptor

The present work focuses on the dynamical aspects of cross-reactivity between myelin based protein (MBP) self-peptide and two microbial peptides (UL15, PMM) for Hy.1B11 T-cell receptor (TCR). This same TCR was isolated from a patient suffering from multiple sclerosis (MS). The study aims at highlighting the chemical interactions underlying recognition mechanisms between TCR and the peptides presented by Major Histocompatibility Complex (MHC) proteins, which form a crucial component in adaptive immune response against foreign antigens. Since the ability of a TCR to recognize different peptide antigens presented by MHC depends on its cross-reactivity, we used molecular dynamics methods to obtain atomistic detail on TCR-peptide-MHC complexes. Our results show how the dynamical basis of Hy.1B11 TCR’s cross-reactivity is rooted in a similar bridging interaction pattern across the TCR-peptide-MHC interface. Our simulations confirm the importance of TCR CDR3α E98 residue interaction with MHC and a predominant role of P6 peptide residue in MHC binding affinity. Altogether, our study provides energetic and dynamical insights into factors governing peptide recognition by the cross-reactive Hy.1B11 TCR, found in MS patient.

Daclizumab high-yield process in the treatment of relapsing-remitting multiple sclerosis

Daclizumab is a humanized monoclonal antibody that binds to the α subunit (CD25) of the interleukin-2 receptor and favorably modulates the immune environment in multiple sclerosis (MS). Blockage of CD25, among other effects, causes expansion and enhanced function of regulatory CD56^bright natural killer cells, which seems to be the leading mechanism of action in MS. Phase II and III clinical trials have demonstrated that monthly subcutaneous injections of daclizumab high yield process (DAC HYP) 150 mg in patients with relapsing MS led to a significant reduction of annualized relapse rate and decreased number of contrast-enhanced lesions on brain magnetic resonance imaging. Treatment with DAC HYP had efficacy superior to treatment with weekly injections of interferon β1a. This review summarizes the development of and clinical experience with daclizumab in MS.

A Preliminary Comparative Assessment of the Role of CD8+ T Cells in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis and Multiple Sclerosis

Background. CD8+ T cells have putative roles in the regulation of adaptive immune responses during infection. The purpose of this paper is to compare the status of CD8+ T cells in Multiple Sclerosis (MS) and Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME). Methods. This preliminary investigation comprised 23 CFS/ME patients, 11 untreated MS patients, and 30 nonfatigued controls. Whole blood samples were collected from participants, stained with monoclonal antibodies, and analysed on the flow cytometer. Using the following CD markers, CD27 and CD45RA (CD45 exon isoform 4), CD8+ T cells were divided into naïve, central memory (CM), effector memory CD45RA− (EM), and effector memory CD45RA+ (EMRA) cells. Results. Surface expressions of BTLA, CD127, and CD49/CD29 were increased on subsets of CD8+ T cells from MS patients. In the CFS/ME patients CD127 was significantly decreased on all subsets of CD8+ T cells in comparison to the nonfatigued controls. PSGL-1 was significantly reduced in the CFS/ME patients in comparison to the nonfatigued controls. Conclusions. The results suggest significant deficits in the expression of receptors and adhesion molecules on subsets of CD8+ T cells in both MS and CFS/ME patients. These deficits reported may contribute to the pathogenesis of these diseases. However, larger sample size is warranted to confirm and support these encouraging preliminary findings.

Activating receptor NKG2D targets RAE-1-expressing allogeneic neural precursor cells in a viral model of multiple sclerosis

Transplantation of major histocompatibility complex-mismatched mouse neural precursor cells (NPCs) into mice persistently infected with the neurotropic JHM strain of mouse hepatitis virus (JHMV) results in rapid rejection that is mediated, in part, by T cells. However, the contribution of the innate immune response to allograft rejection in a model of viral-induced neurological disease has not been well defined. Herein, we demonstrate that the natural killer (NK) cell-expressing-activating receptor NKG2D participates in transplanted allogeneic NPC rejection in mice persistently infected with JHMV. Cultured NPCs derived from C57BL/6 (H-2(b) ) mice express the NKG2D ligand retinoic acid early precursor transcript (RAE)-1 but expression was dramatically reduced upon differentiation into either glia or neurons. RAE-1(+) NPCs were susceptible to NK cell-mediated killing whereas RAE-1(-) cells were resistant to lysis. Transplantation of C57BL/6-derived NPCs into JHMV-infected BALB/c (H-2(d) ) mice resulted in infiltration of NKG2D(+) CD49b(+) NK cells and treatment with blocking antibody specific for NKG2D increased survival of allogeneic NPCs. Furthermore, transplantation of differentiated RAE-1(-) allogeneic NPCs into JHMV-infected BALB/c mice resulted in enhanced survival, highlighting a role for the NKG2D/RAE-1 signaling axis in allograft rejection. We also demonstrate that transplantation of allogeneic NPCs into JHMV-infected mice resulted in infection of the transplanted cells suggesting that these cells may be targets for infection. Viral infection of cultured cells increased RAE-1 expression, resulting in enhanced NK cell-mediated killing through NKG2D recognition. Collectively, these results show that in a viral-induced demyelination model, NK cells contribute to rejection of allogeneic NPCs through an NKG2D signaling pathway.

Role of the blood-brain barrier in multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system associated with demyelination and axonal loss eventually leading to neurodegeneration. MS exhibits many of the hallmarks of an inflammatory autoimmune disorder including breakdown of the blood-brain barrier (BBB). The BBB is a complex organization of cerebral endothelial cells, pericytes and their basal lamina, which are surrounded and supported by astrocytes and perivascular macrophages. In pathological conditions, lymphocytes activated in the periphery infiltrate the central nervous system to trigger a local immune response that ultimately damages myelin and axons. Cytotoxic factors including pro-inflammatory cytokines, proteases, and reactive oxygen and nitrogen species accumulate and may contribute to myelin destruction. Dysregulation of the BBB and transendothelial migration of activated leukocytes are among the earliest cerebrovascular abnormalities seen in MS brains and parallel the release of inflammatory cytokines. In this review we establish the importance of the role of the BBB in MS. Improvements in our understanding of molecular mechanism of BBB functioning in physiological and pathological conditions could lead to improvement in the quality of life of MS patients.

Mechanisms of action of ACTH in the management of relapsing forms of multiple sclerosis

Acute and subacute inflammation, the mechanisms by which demyelination and axonal loss occur in multiple sclerosis (MS), result from the migration of activated immune cells into the central nervous system parenchyma. The triggering antigen is unknown, but the process involves deregulated immune response of T and B lymphocytes, macrophages, and mediators with expansion of autoreactive T cells creating a shift in the balance of pro- and anti-inflammatory cytokines favoring inflammation. Ongoing disease activity and exacerbations early in the course of relapsing-remitting MS may prevent full remission and propagate future progressive disability. A key strategy of immune therapy is timely initiation of treatment to achieve remission, followed by maintenance of remission. In this context, treatment with high-dose methylprednisolone (MP) is currently recommended to induce a faster recovery from a clinical exacerbation that results from an acute inflammatory attack. Adrenocorticotropic hormone (ACTH or corticotropin) gel is an alternative for patients who do not respond to or do not tolerate corticosteroids. ACTH is a universal agonist in the melanocortin (MC) system and, as such, among other functions, stimulates the adrenal cortex to produce cortisol. MCs are a family of peptides that includes ACTH and other MC peptides. This system has five classes of receptors, all of which show a strong affinity for ACTH, suggesting a more complex and dynamic mechanism than only inducing endogenous corticosteroid production. ACTH and MCs regulate processes relevant to MS, including anti-inflammatory and immunomodulatory functions involving lymphocytes, macrophages, the sympathetic nervous system involved in inflammatory processes, and reduction of pro-inflammatory cytokines. The clinical implications of the mechanistic differences between corticosteroid and ACTH gel treatment remain to be elucidated. Recent data show that patients experiencing an acute exacerbation, who previously had suboptimal response to or were unable to tolerate MP treatment, showed positive clinical outcomes with fewer adverse events with ACTH gel.

Immunology and oxidative stress in multiple sclerosis: clinical and basic approach

Multiple sclerosis (MS) exhibits many of the hallmarks of an inflammatory autoimmune disorder including breakdown of the blood-brain barrier (BBB), the recruitment of lymphocytes, microglia, and macrophages to lesion sites, the presence of multiple lesions, generally being more pronounced in the brain stem and spinal cord, the predominantly perivascular location of lesions, the temporal maturation of lesions from inflammation through demyelination, to gliosis and partial remyelination, and the presence of immunoglobulin in the central nervous system and cerebrospinal fluid. Lymphocytes activated in the periphery infiltrate the central nervous system to trigger a local immune response that ultimately damages myelin and axons. Pro-inflammatory cytokines amplify the inflammatory cascade by compromising the BBB, recruiting immune cells from the periphery, and activating resident microglia. inflammation-associated oxidative burst in activated microglia and macrophages plays an important role in the demyelination and free radical-mediated tissue injury in the pathogenesis of MS. The inflammatory environment in demyelinating lesions leads to the generation of oxygen- and nitrogen-free radicals as well as proinflammatory cytokines which contribute to the development and progression of the disease. Inflammation can lead to oxidative stress and vice versa. Thus, oxidative stress and inflammation are involved in a self-perpetuating cycle.

Degenerate T-cell receptor recognition, autoreactive cells, and the autoimmune response in multiple sclerosis

Multiple sclerosis (MS) is the leading cause of disability in the young adult population. While the immunopathogenetic mechanisms that drive the disease have been extensively studied, the autoantigens that trigger the chronic central nervous system inflammation are still not identified. Flexibility/ degeneracy of the T-cell receptor (TCR) in antigen recognition could have a physiological role in thymic selection and the development of comprehensive TCR repertoire and protection from infections. Here, the author explores the possibility that such flexibility/degeneracy may also play a role in the induction of autoimmune diseases. Major histocompatibility complex (MHC) class II alleles of the DR2 haplotype DR2a (DRB5*0101) and DR2b (DRB1*1501) are genes associated with an increased risk for MS in Caucasian populations. Peptide binding to the MHC molecule is a prerequisite for recognition by TCRs, whereby the CD4+ T-cell response is restricted by specific MHC class II DR molecules. To selectively expand and characterize DR2-restricted T-cells with degenerate TCR (TCR(deg)), the authors designed MHC class II DR2-anchored peptide mixtures, which preferentially bind to the DR2a and DR2b antigen-presenting molecules. Peptides in these mixtures have specific amino acids in the DR2 binding positions but have randomized amino acids at all other positions of the peptide. Due to the low concentration of individual peptides in these mixtures/libraries, the authors assume that only T-cells with TCR(deg) will proliferate in response to these mixtures. The authors have recently identified an increased DR2 restricted TCR(deg) T-cell frequency in MS patients in comparison to healthy controls, their cross-reactivity to myelin basic protein, and the secretion of proinflammatory cytokines, all of which suggest that these cells may play a role in the development of the autoimmune response in MS.

A systematic review of oral methotrexate for multiple sclerosis

Oral methotrexate is a potent immunosuppressant, which could have a beneficial effect on relapse rates and delay disease progression in multiple sclerosis (MS). We performed a systematic review of all randomized controlled trials of oral methotrexate for MS. Of the two randomized controlled trials identified, one was excluded due to its allocation concealment and definition of a relapse and time to sustained disease progression. The other trial studied 60 participants with progressive MS only. This trial reported a non-significant reduction in sustained Expanded Disability Status Scale (EDSS) progression and number of relapses in favour of methotrexate therapy. There were no data on relapse rate and no difference in time to first relapse. Minor side-effects were reported in both methotrexate (87.1%) and placebo groups (89.7%), but there were no major side-effects. Further trials are required in both relapsing-remitting and progressive groups to establish the role of oral methotrexate in MS.

Immunomodulatory effects of 3-hydroxy-3-methylglutaryl coenzyme-A reductase inhibitors, potential therapy for relapsing remitting multiple sclerosis

This study characterized immunomodulatory targets of statins in humans and their potential for treatment of relapsing remitting multiple sclerosis (RR MS). Statins inhibited the proliferative response of mononuclear cells. Simvastatin, the statin with the strongest antiproliferative effect, inhibited IFN-gamma-induced expression of MHC class II DR on monocytes and decreased their antigen presenting capacity. As for T lymphocytes, it inhibited their activation and expression of the Th1 lineage differentiation markers. Simvastatin inhibited IFN-gamma, TNF-alpha, and IL-2 secretion, as well as the expression of T-bet, a transcription factor that regulates Th1 cell differentiation.

The pathogenesis of multiple sclerosis: relating human pathology to experimental studies

Multiple sclerosis (MS) is a complex disease of unknown etiology. A careful study of the pathology of its component elements in relation to relevant experimental models has helped to understand some of the mechanisms that might be present in the disease. However, the autoimmune nature of the disease has recently come under question and there is a growing recognition of the importance of axonal, cortical, and white matter changes in the genesis and evolution of the lesions, their clinical diagnostic characteristics, and their response to treatment. This review highlights the emerging issues in MS from experimental, imaging and clinical perspectives.

Trigeminal neuralgia in a patient with multiple sclerosis and chronic inflammatory demyelinating polyneuropathy

BACKGROUND

Trigeminal neuralgia (TN) is characterized by unilateral, severe, brief, stabbing, recurrent pain in the distribution of one or more branches of the fifth cranial nerve. Symptomatic or secondary TN involves TN-like pain that develops owing to a central nervous system lesion (benign or malignant) or to multiple sclerosis (MS).

CASE DESCRIPTION

The authors present a report of a unique case of a 43-year-old patient with unilateral TN, MS and concomitant chronic inflammatory demyelinating polyneuropathy. The facial pain preceded any other manifestations of the systemic disorders, and only after repeated neurological examinations were these diagnoses established.

CLINICAL IMPLICATIONS

Magnetic resonance imaging of the brain and repeated neurological evaluations should be implemented in all patients with TN to rule out the presence of underlying disease. The dental practitioner should be familiar with TN to avoid unnecessary dental interventions and ensure prompt initiation of appropriate treatment.