Failed B cell survival factor trials support the importance of memory B cells in multiple sclerosis

Clinical trials are probably the most informative experiments to help an understanding of multiple sclerosis (MS) biology. Recent successes with CD20‐depleting antibodies have focused attention towards B cell subsets as important mediators in MS. The trial of tabalumab (NTC00882999), which inhibits B cell activation factor (BAFF), is reported and reviewed and this trial is contrasted with the trial on the inhibition of a proliferation‐inducing ligand (APRIL) and BAFF using atacicept (NCT00642902). Both tabalumab and atacicept induce depletion of mature B cells and inhibit antibody formation, but they fail to deplete memory B cells and do not inhibit relapsing MS. Atacicept is reported to augment memory B cell responses and may precipitate relapse, suggesting the importance of APRIL. However, BAFF inhibition can enhance peripheral blood memory B cell responses, which was not associated with augmented relapse. Although other interpretations are possible, these data further support the hypothesis that memory B cells may be of central importance in relapsing MS, as they are the major CD20+ B cell subset expressing APRIL receptors. They also suggest that quantitative and/or qualitative differences in B cell responses or other factors, such as an immune‐regulatory effect associated with APRIL, may be important in determining whether MS reactivates following neutralization of peripheral B cell maturation and survival factors.     

B cells in multiple sclerosis therapy—A comprehensive review

For decades, B cells were ignored in multiple sclerosis (MS) pathogenesis, and the disease was always regarded as a T cell‐mediated disorder. Recent evidence shows that there is an antigen‐driven B‐cell response in the central nervous system of patients with MS, and memory B cells/plasma cells are detectable in MS lesions. The striking efficacy of B cell‐depleting therapies in reducing the inflammatory activity of the disease highlights that B cells may play more pathogenetic roles than expected. B cells express several unique characteristic markers on their surface, for example, CD19, CD20 molecules, that provide selective targets for monoclonal antibodies. In this respect, several B cell‐targeted therapies emerged, including anti‐CD20 antibodies (rituximab, ocrelizumab, and ofatumumab), anti‐CD19 antibody (inebilizumab), and agents targeting the BAFF/APRIL signaling pathway (atacicept, belimumab, and LY2127399). In this review, we discuss, in detail, the immunobiology of B cells and their protective and destructive roles in MS pathogenesis. In the second part, we list the completed and ongoing clinical trials investigating the safety and efficacy of B cell‐related monoclonal antibodies in MS.     

A differential diagnosis of central nervous system demyelination: beyond multiple sclerosis

Although multiple sclerosis (MS) is the most common demyelinating disorder of the central nervous system (CNS), it lacks any definitive diagnostic test. Instead, diagnosis of MS primarily depends upon clinical criteria, supported by abnormalities characteristic of MS on para-clinical investigations including magnetic resonance imaging of the brain and spine, in the absence of an alternative explanation for underlying neurologic symptoms. While many of the potential disorders that may mimic MS in routine clinical practice are either extremely rare, or associated with specific and characteristic distinguishing diagnostic features, some inflammatory demyelinating disorders of the CNS may be particularly challenging to distinguish from MS, especially during initial presentation. In particular, acute disseminated encephalomyelitis, neuromyelitis optica, and idiopathic transverse myelitis may closely resemble MS, impeding prompt and accurate diagnosis. In this review, we describe the clinical features, diagnosis, pathology, and treatment of these other CNS demyelinating disorders. In addition, we review relevant features of other CNS inflammatory disorders that may mimic MS, including Sj?gren's syndrome, systemic lupus erythematosus, Beh?et's disease, and primary CNS vasculitis.     

A sulfatide-reactive human monoclonal antibody obtained from a multiple sclerosis patient selectively binds to the surface of oligodendrocytes

In a previous paper, we described the production of a sulfatide-reactive IgM antibody-secreting B cell line that was obtained by Epstein-Barr virus transformation of peripheral B cells from a patient with multiple sclerosis (MS) (Uhlig and Dernick, 1989). In the present study, we demonstrate that this human monoclonal antibody (humAb) DS1F8 selectively binds to the surface of living oligodendrocytes in mixed brain cell cultures of newborn rats. Since a mouse mAb reactive with sulfatide was shown to inhibit oligodendrocyte progenitor differentiation, autoantibodies with binding specificities similar to DS1F8 could play a role in the demyelinating process in the CNS.     

B cells as therapeutic targets in autoimmune neurological disorders

B cells have a fundamental role in the pathogenesis of various autoimmune neurological disorders, not only as precursors of antibody-producing cells, but also as important regulators of the T-cell activation process through their participation in antigen presentation, cytokine production, and formation of ectopic germinal centers in the intermeningeal spaces. Two B-cell trophic factors-BAFF (B-cell-activating factor) and APRIL (a proliferation-inducing ligand)-and their receptors are strongly upregulated in many immunological disorders of the CNS and PNS, and these molecules contribute to clonal expansion of B cells in situ. The availability of monoclonal antibodies or fusion proteins against B-cell surface molecules and trophic factors provides a rational approach to the treatment of autoimmune neurological diseases. This article reviews the role of B cells in autoimmune neurological disorders and summarizes the experience to date with rituximab, a B-cell-depleting monoclonal antibody against CD20, for the treatment of relapsing-remitting multiple sclerosis, autoimmune neuropathies, neuromyelitis optica, paraneoplastic neurological disorders, myasthenia gravis, and inflammatory myopathies. It is expected that ongoing controlled trials will establish the efficacy and long-term safety profile of anti-B-cell agents in several autoimmune neurological disorders, as well as exploring the possibility of a safe and synergistic effect with other immunosuppressants or immunomodulators.     

BAFF is up-regulated in central nervous system of neuro-Behçet's disease

We report that B cell-activating factor of the tumor necrosis factor family (BAFF) is expressed in central nervous system (CNS) of neuro-Beh?et's disease (NBD). This study investigated BAFF and BAFF-R (BAFF receptor) in NBD, compared to multiple sclerosis (MS) and to non inflammatory neurological diseases (NIND). Cerebrospinal fluid (CSF) was used to determine the level of BAFF messenger RNA (mRNA) and the level of BAFF-R mRNA in unfractionated cells. A sandwich ELISA was used to quantify soluble BAFF protein levels in serum and in CSF. BAFF and BAFF-R expression in CSF were increased in NBD and MS patients compared to NIND patients. RNA levels of BAFF and BAFF-R were significantly correlated in NBD and MS patients. Serum sBAFF levels were increased in NBD and MS patients, but did not correlate with BAFF expression in CSF. CNS-produced BAFF may support inflammatory cell survival in NBD.     

Demyelinating experimental allergic encephalomyelitis (EAE) in the rat: treatment with a monoclonal antibody against activated T cells

We used a new version of experimental autoimmune encephalomyelitis (EAE) in the rat to investigate immunotherapy of demyelination during autoimmune disease of the central nervous system (CNS). Encephalitis was induced by immunization of rats with myelin basic protein (MBP), and demyelination by systemic injection of a monoclonal antibody, 8-18C5, specific for a myelin/oligodendrocyte glycoprotein (MOG). Antibody injection resulted in hyperacute disease progression and extensive demyelination throughout the CNS. Immunotherapy of antibody-induced demyelination was possible with another monoclonal antibody, pta-3, specific for activated rat T cells. These findings demonstrate the synergy of T cell-mediated and antibody-dependent processes in rat CNS demyelination in vivo. Histologically, immunotherapy reduced the numbers of meningeal mononuclear cell inflammatory foci, but not parenchymal inflammation in the early phase of demyelinating disease. Animals which had received pta-3 antibody had less inflammation than untreated rats in the convalescent phase. Multiple pta-3 treatments most effectively suppressed inflammation. Furthermore, antibody-treated rats with demyelination developed a series of neurologic signs, including pronounced spasticity; that were not observed in control EAE rats and thus appears to be associated with the demyelinating process.     

Demyelination in the central nervous system mediated by an anti-oligodendrocyte antibody

The factors responsible for the major demyelinating disease of the central nervous system (CNS), multiple sclerosis, are poorly defined. Although T-cell-mediated immune responses play a pivotal role in establishing the inflammatory response, humoral factors also may be critical in disease progress. We have isolated a mouse monoclonal antibody (mAb 2B10) that recognizes a cell-surface molecule expressed exclusively by rat oligodendrocytes, the cells responsible for the formation and maintenance of CNS myelin. In cultures of neonatal rat spinal cord, mAb 2B10 specifically mediated oligodendrocyte cell death in the absence of complement. In the current study, mAb 2B10–producing hybridoma cells were implanted into adult rat brain ventricles, and the effect of mAb 2B10 on CNS cytoarchitecture was examined. In the optic nerves of mAb 2B10–treated animals, there was significant focal myelin degeneration near the optic chiasm. Axons in the myelin degenerate regions were largely healthy. There was no significant infiltration of hematopoietic-derived cells into the affected regions, but microglia were activated focally and phagocytosed the collapsed myelin. This study demonstrates that an antibody directed against myelin-forming cells induces CNS demyelination and supports the hypothesis that autoantibodies may play a role in CNS demyelinating diseases. J. Neurosci. Res. 54:158–168, 1998. © 1998 Wiley-Liss, Inc.     

Clustering of organ-specific autoimmunity: a case presentation of multiple sclerosis and connective tissue disorders

Multiple sclerosis (MS) is the most common demyelinating disease caused by an autoimmune inflammatory process in the central nervous system (CNS) and is associated with aberrant immune response to myelin selfantigens. Coexistence of MS with other autoimmune disorders, including connective tissue disorders including systemic lupus erythematosus, rheumatoid arthritis, Sjögren’s syndrome and scleroderma have been reported previously. In the present article we report the coexistence of MS, familial mediterranean fever and ankylosing spondylitis in a patient and review the clinical presentation, neurologic findings, cerebrospinal fluid and radiologic characteristics and treatment options. We further discuss the immunopathogenetic mechanisms for a possible association between MS and autoimmune disorders.     

Cerebrospinal BAFF and Epstein-Barr virus-specific oligoclonal bands in multiple sclerosis and other inflammatory demyelinating neurological diseases

We measured circulating serum and cerebrospinal fluid (CSF) concentrations of B lymphocyte activating factor of the tumour necrosis factor superfamily (BAFF), and determined total and Epstein-Barr virus (EBV)-specific oligoclonal IgG bands (OCBs) in 43 patients with multiple sclerosis (MS), 23 patients with other inflammatory demyelinating neurological diseases, and 20 patients with non-inflammatory neurological diseases. Serum and CSF BAFF concentrations did not differ in the three studied groups. In MS, the highest BAFF concentrations were found in the CSF samples with more than 6 OCBs (233.1 ± 129.5 vs 79.2 ± 51.6 pg/mL in the samples with less than 7 OCBs, p<0.0001). Irrespectively from BAFF levels, EBV-specific OCBs were detected in MS and in the other non-inflammatory and inflammatory demyelinating neurological diseases, with a similar frequency, and as a 'mirror pattern' in 30 of 33 EBV-specific OCB-positive cases (p<0.0001). These results indicate that circulating CSF BAFF concentrations cannot help differentiate MS from other inflammatory demyelinating neurological diseases, but positively associates with the qualitative expression of elevated intrathecal IgG production in MS, and that the oligoclonal EBV-specific antibody response, when present, is mostly systemic in all the studied neurological patients, and not preferentially restricted to MS.     

Autoimmunity in multiple sclerosis

Multiple sclerosis reportedly coexists with disorders of autoimmune origin. The prevalence with which such disorders occur in the MS population has not been adequately investigated. We reviewed the medical records of 828 patients with definite MS and found that 4.8% had a past or present associated disorder in which autoimmune mechanisms presumably play a role. The cumulative prevalence of these disorders was no higher than that estimated for the general population. Serum from 105 patients, without clinical evidence of an associated autoimmune disorder, was tested for the presence of antinuclear, thyroid, parietal cell, smooth muscle, and mitochondrial antibodies. A significantly higher prevalence (p less than 0.01) of generally low titers of one or more autoantibodies was found in serum from the MS group, compared with a control group of 105 patients with other neurologic disorders. The increased frequency of serum autoantibodies probably reflects the existence of a nonspecific B cell overactivity in MS.     

Expression of CD5 on B lymphocytes correlates with disease activity in patients with multiple sclerosis

There is growing evidence that implicates B lymphocytes and their products in the pathogenesis of multiple sclerosis (MS). A subpopulation of B lymphocytes expressing the CD5 antigen are involved in several autoimmune disorders through the release of autoantibodies. In this study, we used three-color flow cytometry to examine the expression of CD5 antigen on B lymphocytes from patients with relapsing-remitting MS, and correlated this expression with features of disease activity and circulating levels of autoantibodies against myelin basic protein. CD5 expression on B lymphocytes was significantly higher in patients with active MS when compared to patients with clinically stable MS or those with inflammatory or noninflammatory neurologic disorders. CD5(+) B lymphocytes from patients with active MS correlated significantly with the number of gadolinium-enhancing MRI lesions, and inversely with disease duration. The expression of CD5 on B lymphocytes in MS patients also correlated with circulating levels antibodies against myelin basic protein. Results presented here indicate that clinically active MS is associated with an expanded population of peripheral CD5(+) B lymphocytes.     

Chemokines and chemokine receptors in the pathogenesis of multiple sclerosis

In recent years we have seen growing evidence for the role of chemokines in the pathogenesis of several infectious and non-infectious inflammatory CNS disease states, including Multiple Sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE). An increase in proinflammatory chemokines has been associated with demyelinating lesions and clinical neurological dysfunction in patients with MS; these chemokines could be potential targets for MS therapy. Besides a clearly defined role in mediating leukocyte migration, these and other chemokines may act as immunoregulatory molecules in the driving to Th1/Th2 responses, switch of cytokine profiles, and the induction of tolerance. Since chemokine receptors have now been identified on macrophages, microglia, astrocytes, and endothelial cells as well as neurons in the CNS, chemokine/receptor interactions may mediate functional responses in a variety of CNS cell types during the course of inflammatory disease states. Therefore, clarification of the roles of chemokines and their receptors in the pathogenesis of EAE and MS will be useful in establishing immunotherapeutic strategies for these neurological autoimmune disorders.     

Apoptosis of inflammatory cells in immune control of the nervous system: role of glia

The elimination of inflammatory cells within the central nervous system (CNS) by apoptosis plays an important role in protecting the CNS from immune-mediated damage. T cells, B cells, macrophages, and microglia all undergo apoptosis in the CNS. The apoptotic elimination of CNS-reactive T cells is particularly important, as these cells can recruit and activate other inflammatory cells. T-cell apoptosis contributes to the resolution of CNS inflammation and clinical recovery from attacks of experimental autoimmune encephalomyelitis (EAE), an animal model of the demyelinating disease multiple sclerosis (MS). T-cell apoptosis in the CNS in EAE occurs in both an antigen-specific and an antigen-nonspecific manner. In antigen-specific T-cell apoptosis, it is proposed that T cells that recognize their antigen in the CNS, such as CNS-reactive T cells, are deleted by the process of activation-induced apoptosis after activation of the T-cell receptor. This may result from the ligation of T-cell death receptors (such as CD95 (Fas) or tumor necrosis factor (TNF) receptor 1) by CD95 ligand (CD95L) or TNF expressed by the same T cell or possibly by microglia, astrocytes or neurons. Inadequate costimulation of the T cell by antigen-presenting glial cells may render T cells susceptible to activation-induced apoptosis. T cells expressing CD95 may also die in an antigen-nonspecific manner after interacting with glial cells expressing CD95L. Other mechanisms for antigen-nonspecific T-cell apoptosis include the endogenous release of glucocorticosteroids, deprivation of interleukin-2, and the release of nitric oxide by macrophages or glia. Apoptosis of autoreactive T cells in the CNS is likely to be important in preventing the development of autoimmune CNS diseases such as MS.     

DNA-based vaccines: the future of multiple sclerosis therapy?

Multiple sclerosis (MS) is the most common human inflammatory, demyelinating and degenerative disorder of the CNS. Based mostly on work in experimental autoimmune encephalomyelitis, CD4(+) T cells were long thought to play the crucial role in MS pathogenesis. Only more recently has it been recognized that other effector cell types, including CD8(+) T cells, gammadelta-T cells and B lymphocytes may also have an important role in disease initiation and perpetuation. The expression of soluble inflammatory mediators, including cytokines and free radicals, may be one of the late pathways mediating CNS tissue damage. In addition, in virtually all patients with MS, an oligoclonal banding pattern of antibodies can be detected in the cerebrospinal fluid (CSF). However, the cause of MS still remains unknown. Specifically, no single foreign or self antigen has been identified to account for clinical disease activity or the presence of surrogate disease markers. All approved pharmacotherapies have anti-inflammatory or immunoregulatory properties and work in early stages of the disease. In a recent clinical trial, BHT-3009, a DNA vaccine encoding full-length human myelin basic protein, was tested in patient with MS. BHT-3009 was safe and well tolerated. In addition, immunization with BHT-3009 induced anti-inflammatory antigen-specific immune changes consisting of a marked decrease in T-cell proliferation of IFN gamma production and a reduction in titers of myelin-specific autoantibodies in the CSF. This review will discuss these intriguing observations and the overall potential of DNA vaccination in MS.     

Evidence for central nervous system demyelination in chronic inflammatory demyelinating polyradiculoneuropathy

It is unclear whether sporadic reports of concurrent multiple sclerosis (MS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) represent coincidence or whether these two demyelinating disorders are pathogenically related. We utilized the sensitivity of magnetic resonance imaging (MRI) in detecting central nervous system (CNS) lesions to investigate 16 patients with CIDP. Six of the 16 had periventricular, subcortical, and brainstem white matter lesions indistinguishable from those seen in MS. Three of these patients had definite clinical and laboratory evidence of MS; three others with abnormal MRIs had no findings indicative of CNS disease. Previous reports have indicated that a significant number of MS patients have peripheral nerve demyelination. Our study suggests that many CIDP patients have concurrent CNS demyelination. Taken together, these observations support the existence of a central-peripheral inflammatory demyelinating syndrome. Whether this combined demyelinating syndrome lies on a spectrum between MS and CIDP or is a separate pathogenic entity will require further investigation.     

Expression of B-cell-activating factor of the TNF family (BAFF) and its receptors in multiple sclerosis

The role of B cells and antibodies in the pathogenesis of multiple sclerosis (MS) is controversial. We investigated the expression of B-cell-activating factor of the tumor necrosis factor family (BAFF), a protein indispensable for B-cell survival, and of its three receptors in MS patients and controls. BAFF mRNA levels in monocytes, and BAFF-receptor mRNA in B and T cells, were higher in patients than in healthy controls; yet, BAFF protein levels in cerebrospinal fluid and plasma were similar in patients and headache controls. In addition, each MS disease course was associated with a unique expression pattern for all four molecules.     

Candidate autoantigens in multiple sclerosis.

Multiple sclerosis is an inflammatory demyelinating CNS disease of putatively autoimmune origin. Novel models of experimental autoimmune encephalomyelitis (EAE) have demonstrated that T cells specific for various myelin and even nonmyelin proteins are potentially encephalitogenic. The encephalitogenic T cell response directed against different CNS antigens not only determines the lesional topography of CNS inflammation but also the composition of the inflammatory infiltrates. The heterogeneity of the lesional distribution seen in EAE might therefore be useful for the understanding of the various clinical subtypes seen in MS. In this review the possible candidate autoantigens in MS are discussed with special regard to the human T cell and B cell responses against various myelin and nonmyelin proteins.