Immunopathogenesis of multiple sclerosis: concepts and controversies

Oral administration of procyanidin B2 3,3"-di-O-gallate ameliorates experimental autoimmune encephalomyelitis through immunosuppressive effects on CD4+ T cells by regulating glycolysis

Multiple Sclerosis (MS) is a chronic autoimmune disease of the central nervous system caused by the excessive activation of T cells. Procyanidins are polyphenols that exhibit anti-inflammatory activity. Procyanidin B2 (PCB2) gallate [specifically, PCB2 3,3″-di-O-gallate (PCB2DG)] inhibits cytokine production in T cells by suppressing the acceleration of glycolysis. In this study, we determined the effect of PCB2DG on T cell-mediated autoimmune disease in vivo. We examined the immunosuppressive effects of PCB2DG using an experimental autoimmune encephalomyelitis (EAE) model, which is a classic animal model for MS. Our results indicated that the clinical score for EAE symptoms improved significantly following the oral administration of PCB2DG. This effect was associated with the suppression of T cell-mediated cytokines (e.g., IFN-γ, TNF-α, and IL-17) and infiltrating T cells into the spinal cord, which ameliorated spinal cord injury. In addition, spleen cell culture experiments revealed that the increase of T cell-mediated pro-inflammatory cytokines in EAE mice was significantly decreased following PCB2DG treatment. We further analyzed the glycolytic activity of spleen cells to identify the mechanism of the immunosuppressive effects of PCB2DG. The production of lactate and the expression of glycolytic enzymes and transporters were increased following EAE induction, but not in PCB2DG-treated EAE mice. Collectively, our results indicate that a dietary polyphenol, which has a unique structure, improves the onset of EAE symptoms and inhibits the excessive activation of T cells by influencing glycolysis.

Calming Down Mast Cells with Ketotifen: A Potential Strategy for Multiple Sclerosis Therapy?

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) characterized by extensive inflammation, demyelination, axonal loss and gliosis. Evidence indicates that mast cells contribute to immunopathogenesis of both MS and experimental autoimmune encephalomyelitis (EAE), which is the most employed animal model to study this disease. Considering the inflammatory potential of mast cells, their presence at the CNS and their stabilization by certain drugs, we investigated the effect of ketotifen fumarate (Ket) on EAE development. EAE was induced in C57BL/6 mice by immunization with MOG35-55 and the animals were injected daily with Ket from the seventh to the 17th day after disease induction. This early intervention with Ket significantly reduced disease prevalence and severity. The protective effect was concomitant with less NLRP3 inflammasome activation, rebalanced oxidative stress and also reduced T cell infiltration at the CNS. Even though Ket administration did not alter mast cell percentage at the CNS, it decreased the local CPA3 and CMA1 mRNA expression that are enzymes typically produced by these cells. Evaluation of the CNS-barrier permeability indicated that Ket clearly restored the permeability levels of this barrier. Ket also triggered an evident lymphadenomegaly due to accumulation of T cells that produced higher levels of encephalitogenic cytokines in response to in vitro stimulation with MOG. Altogether these findings reinforce the concept that mast cells are particularly relevant in MS immunopathogenesis and that Ket, a known stabilizer of their activity, has the potential to be used in MS control.

Interleukin-7 is required for CD4(+) T cell activation and autoimmune neuroinflammation

IL-7 is known to be vital for T cell homeostasis but has previously been presumed to be dispensable for TCR-induced activation. Here, we show that IL-7 is critical for the initial activation of CD4(+) T cells in that it provides some of the necessary early signaling components, such as activated STAT5 and Akt. Accordingly, short-term in vivo IL-7Rα blockade inhibited the activation and expansion of autoantigen-specific CD4(+) T cells and, when used to treat experimental autoimmune encephalomyelitis (EAE), prevented and ameliorated disease. Our studies demonstrate that IL-7 signaling is a prerequisite for optimal CD4(+) T cell activation and that IL-7R antagonism may be effective in treating CD4(+) T cell-mediated neuroinflammation and other autoimmune inflammatory conditions.

Uses of complementary and alternative medicine in multiple sclerosis

Multiple sclerosis (MS) is a chronic, disabling, recurrent demyelination of the central nervous system (CNS). It could affect different regions in the brain and spinal cord, and according to the domain which is affected, it could cause different symptoms such as motor, sensory, or visual impairment; fatigue; bowel, bladder, and sexual dysfunction; cognitive impairment; and depression. MS patients also face reduced quality of life. Drugs that are used in MS are not fully efficient and patients suffer from many symptoms and adverse effects. Today there is an increasing trend of using complementary and alternative medicine (CAM). People are more likely to use this type of treatment. Using appropriate lifestyle and CAM therapy can subside some of the symptoms and could improve the quality of life in these patients. Many people with MS explore CAM therapies for their symptoms. This review is aimed to introduce CAM therapies that could be used in MS patients.

The retrovirus/superantigen hypothesis of multiple sclerosis

The pathogenesis of multiple sclerosis (MS) is as yet unknown. Commonly, MS is assumed to be due to an autoimmune inflammation of the central nervous system (CNS). Neurodegeneration is regarded to be a secondary reaction. This concept is increasingly being challenged. Human endogenous retroviruses (HERV) that could be locally activated in the CNS have been proposed as an alternative concept. HERV-encoded envelope proteins (env) can act as strong immune stimulators (superantigens). Thus, slow disease progression following neurodegeneration might be induced by re-activation of HERV expression directly, while relapses in parallel to inflammation might be secondary to the expression of HERV-encoded superantigens. It has been shown previously that T-cell superantigens are capable to induce a cellular inflammatory reaction in the CNS of experimental animals similar to that in MS. Furthermore, B-cell superantigens have been shown to activate blood leucocytes in vitro to produce immunoglobulin in an oligoclonal manner. It remains to be established, whether the outlined hypothesis accords with all known features of MS. Furthermore, anti-HERV agents may be taken into consideration to enrich and improve MS therapy.

Disease-modifying treatments for progressive multiple sclerosis

The last 20 years have seen major progress in the treatment of relapsing-remitting multiple sclerosis (RRMS) using a variety of drugs targeting immune dysfunction. In contrast, all clinical trials of such agents in primary progressive multiple sclerosis (PPMS) have failed and there is limited evidence of their efficacy in secondary progressive disease. Evolving concepts of the complex interplay between inflammatory and neurodegenerative processes across the course of multiple sclerosis (MS) may explain this discrepancy. This paper will provide an up-to-date overview of the rationale and results of the published clinical trials that have sought to alter the trajectory of both primary and secondary MS, considering studies involving drugs with a primary immune target and also those aiming for neuroprotection. Future areas of study will be discussed, building on these results combined with the experience of treating RRMS and new concepts emerging from laboratory science and animal models.

Dynamics of B-Cell Populations in CSF and Blood in Patients Treated with a Combination of Rituximab and Mitoxantrone

Background. Mitoxantrone (MTX) and Rituximab (RTX) are successfully used for treatment of multiple sclerosis (MS) and can be combined to increase efficacy. Objective. We used MTX, RTX, and methylprednisolone in a single combined regiment and observed patients prospectively. Methods. We present results of observational pilot study of combined therapy of RTX and MTX in 28 patients with active MS. Therapeutic protocol consisted of two infusions within 14 days. First infusion was 1000 mg methylprednisolone (MP) IV, 1000 mg RTX IV, and 20 mg MTX IV. On day 14, 1000 mg MP IV and 1000 mg RTX IV were given. Patients were followed prospectively from 12 to 48 months. Results and Conclusion. There were no relapses among all 28 patients during the observation period. B-cell depletion of CD19+ and CD19+/CD27+ memory B-cell subpopulation in both compartments was confirmed in all patients at 6 months. We found a more rapid reconstitution of B cells in the CSF than in the peripheral blood and longstanding depression of CD19+CD27+ memory B-cell. Conclusion. Effectiveness of combined regimen of RTX and MTX could be related to longstanding depletion of CD19+CD27+ memory B-cell subset.

Hyaluronan anchored to activated CD44 on central nervous system vascular endothelial cells promotes lymphocyte extravasation in experimental autoimmune encephalomyelitis

The extravasation of lymphocytes across central nervous system (CNS) vascular endothelium is a key step in inflammatory demyelinating diseases including multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). The glycosaminoglycan hyaluronan (HA) and its receptor, CD44, have been implicated in this process but their precise roles are unclear. We find that CD44(-/-) mice have a delayed onset of EAE compared with wild type animals. Using an in vitro lymphocyte rolling assay, we find that fewer slow rolling (<1 μm/s) wild type (WT) activated lymphocytes interact with CD44(-/-) brain vascular endothelial cells (ECs) than with WT ECs. We also find that CD44(-/-) ECs fail to anchor HA to their surfaces, and that slow rolling lymphocyte interactions with WT ECs are inhibited when the ECs are treated with a pegylated form of the PH20 hyaluronidase (PEG-PH20). Subcutaneous injection of PEG-PH20 delays the onset of EAE symptoms by ~1 day and transiently ameliorates symptoms for 2 days following disease onset. These improved symptoms correspond histologically to degradation of HA in the lumen of CNS blood vessels, decreased demyelination, and impaired CD4(+) T-cell extravasation. Collectively these data suggest that HA tethered to CD44 on CNS ECs is critical for the extravasation of activated T cells into the CNS providing new insight into the mechanisms promoting inflammatory demyelinating disease.

Immune modulation by chondroitin sulfate and its degraded disaccharide product in the development of an experimental model of multiple sclerosis

Clinical symptoms in MOG-induced EAE mice significantly exacerbated following chondroitin sulfate A (CS-A) injection, whereas administration of a degraded product, CSPG-DS, caused dramatic inhibition of EAE development. Also, administration of CSPG-DS but not CS-A, after the onset of clinical symptoms of EAE, was able to suppress the disease. Further studies demonstrated that CS-A up-regulated STAT4 expression and thus, induced IFN-gamma production and Th1 CD4 T cell differentiation. CS-A also up-regulated STAT3 and IL-23 expression and thus increased IL-17 producing T cells. CSPG-DS treatment both in vivo and in vitro decreased TNFalpha production from splenocytes. In vitro and in vivo studies indicated that CSPG-DS treatment in EAE mice significantly blocked migration of lymphocytes, whereas CS-A treatment increased lymphocyte infiltration in the brain.

The double-edged sword of autoimmunity: lessons from multiple sclerosis

The relationship between immune responses to self-antigens and autoimmune disease is unclear. In contrast to its animal model experimental autoimmune encephalomyelitis (EAE), which is driven by T cell responses to myelin antigens, the target antigen of the intrathecal immune response in multiple sclerosis (MS) has not been identified. Although the immune response in MS contributes significantly to tissue destruction, the action of immunocompetent cells within the central nervous system (CNS) may also hold therapeutic potential. Thus, treatment of MS patients with glatiramer acetate triggers a protective immune response. Here we review the immunopathogenesis of MS and some recent findings on the mechanism of glatiramer acetate (GA).

The idiotype connection: linking infection and multiple sclerosis

B cells present idiotopes (Id) from their B cell receptor to Id-specific CD4(+) T cells. Chronic Id-driven T-B cell collaboration can cause autoimmune disease in mice. We propose that Id-driven T-B cell collaboration mediates the development of multiple sclerosis by perpetuating immune responses initiated against infectious agents. During germinal centre reactions, B cells express a multitude of mutated Ids. While most mutations lead to decreased affinity and deletion of the B cell, some B cells could be rescued by Id-specific T cells. Such Id-connected T-B cell pairs might initiate inflammatory foci in the central nervous system. This model may explain the intrathecal synthesis of low-avidity IgG against viruses, and the synthesis of oligoclonal IgG with unknown specificity in multiple sclerosis.

Protective and detrimental immunity: lessons from stiff person syndrome and multiple sclerosis

BACKGROUND

The immune system may attack the brain and cause inflammatory disorders like multiple sclerosis (MS). On the other hand, the immune system may protect and support neurons.

METHODS

There are two obstacles to study this paradox in humans. First, the target antigens in many human central nervous system (CNS) disorders are unknown. Second, it is often difficult to separate pathogenic from protective events, as well as primary from secondary phenomena. Idiopathic stiff person syndrome (SPS) circumvents the first obstacle, because most patients secrete antibodies against glutamic acid decarboxylase (GAD) 65. The immune response against glatiramer acetate (GA) may circumvent the second obstacle. Migration of activated T helper cells to the intrathecal compartment could be a common denominator in GA treatment and SPS.

RESULTS

We here discuss recent results on T cells in MS and SPS, showing that GAD65-specific and GA-reactive lymphocytes in the cerebrospinal fluid are not a simple reflection of those in blood.

CONCLUSION

The rules and mechanisms governing T cell selection and maintenance in the CNS may provide a key to the understanding of protective and detrimental aspects of CNS immunity.

The histopathology of grey matter demyelination in multiple sclerosis

Multiple sclerosis (MS) is characterized by focal demyelinating lesions in white matter (WM) and grey matter (GM) of the central nervous system. Results of studies using quantitative magnetic resonance imaging techniques indicate that GM MS pathology has a significant impact on clinical symptoms and disability in MS, and may occur partly independently of WM pathology. Subpial cerebral and cerebellar cortexes are predilection sites for demyelination in MS. Significant neuronal and axonal pathology has been detected in GM MS lesions. The pathology of MS lesions is location-dependent; there is less pronounced inflammation in GM lesion areas than in WM lesions. The presence and extent of GM lesions has recently been correlated to meningeal inflammation, and cells infected with the Epstein-Barr virus have been detected in meningeal infiltrates, suggesting a role of meningeal inflammation in cortical lesion pathogenesis.

Interleukin-4 as a neuromodulatory cytokine: roles and signaling in the nervous system

Although interleukin (IL)-4 is described as a prototypical anti-inflammatory cytokine, in recent years its role as a neuromodulatory cytokine has been extensively discussed. This review highlights the pivotal contributions of IL-4 during the development and normal physiology of neural cells as well as IL-4 connections with the pathophysiology of degenerative or inflammatory processes observed in the central and peripheral nervous system.

High-dose cyclophosphamide in the treatment of multiple sclerosis

High dose cyclophosphamide (HDC) has been successfully used for the treatment of a variety of autoimmune diseases. In this study, we sought to determine whether the use of high dose cyclophosphamide provided stabilization of relapsing remitting MS (RRMS), secondary progressive MS (SPMS), or primary progressive MS (PPMS). The parameters evaluated were EDSS scores, lesion load and brain volumes by MRI and frequency of relapses. Twenty-three patients underwent immunoablative therapy with HDC and were followed for 3.5 years. Nine were relapsing remitting (RRMS), 11 secondary progressive (SPMS), and 3 primary progressive (PPMS). Four of 9 RRMS have had no clinical progression up to 3.5 years following treatment. Three of 9 patients maintained a normal neurologic examination with improved EDSS scores. Seven of the nine RRMS patients had reduction in flare frequency which was maintained for 3.5 years following treatment or no immunomodulating agents. Subgroup analysis in the RRMS patients of lesion load and brain parenchymal volume revealed a favorable trend in these parameters which did not reach statistical significance. The treatment was generally ineffective for SPMS and failed in the 2 PPMS patients. HDC was well tolerated, demonstrated a good safety profile and had minimal adverse effects. These results along with previous reports suggest that early use of HDC therapy in RRMS is promising.

Multiple sclerosis: immunopathogenesis and controversies in defining the cause

PURPOSE OF REVIEW

Multiple sclerosis is a major cause of neurological disability in Western societies. The most important reason for the limited success obtained in the treatment and prevention so far is most likely related to the limited knowledge about its cause and pathogenesis. This paper discusses recent progress and controversies in the understanding of the pathogenesis and cause of multiple sclerosis.

RECENT FINDINGS

Both T helper cells type 1 (Th1 cells), Th17 cells, cytotoxic T cells, B cells and regulatory T cells are involved in the inflammatory process. Axonal loss seems to be driven by inflammation during the early stages of disease but may become independent of inflammation at later stages. The target antigen of the immune response has not been identified. Weak genetic association has been established in two cytokine receptors, whereas increasing female: male ratio support the importance of environmental risk factors. A substantial proportion of intrathecal B cells are infected with Epstein-Barr virus.

SUMMARY

Multiple sclerosis is a complex disease and calls for integrated efforts from immunology, epidemiology, neuroscience and genetics. In particular, the immunological implications of environmental risk factors such as vitamin D desufficiency, smoking and Epstein-Barr virus infection need to be explored.

Autoantibodies and neurodegeneration in multiple sclerosis

Neurodegeneration develops in association with inflammation and demyelination in multiple sclerosis. Available data suggest that the progressive neuroaxonal loss begins in the earliest stages of the disease and underlies the accumulation of clinical disability. The loss of neurons and their processes is driven by a complex molecular mechanism involving cellular and humoral immune histotoxicity, demyelination, reduced neurotrophic support, metabolic impairment, and altered intracellular processes. Here we survey available data concerning the role of autoreactive immunoglobulins in neurotoxicity. A better understanding of molecular pathways leading to immune-mediated neurodegeneration may have key importance in the successful treatment of the disease.