Antibodies produced by clonally expanded plasma cells in multiple sclerosis cerebrospinal fluid

Should We Consider Neurodegeneration by Itself or in a Triangulation with Neuroinflammation and Demyelination? The Example of Multiple Sclerosis and Beyond

Neurodegeneration is preeminent in many neurological diseases, and still a major burden we fail to manage in patient's care. Its pathogenesis is complicated, intricate, and far from being completely understood. Taking multiple sclerosis as an example, we propose that neurodegeneration is neither a cause nor a consequence by itself. Mitochondrial dysfunction, leading to energy deficiency and ion imbalance, plays a key role in neurodegeneration, and is partly caused by the oxidative stress generated by microglia and astrocytes. Nodal and paranodal disruption, with or without myelin alteration, is further involved. Myelin loss exposes the axons directly to the inflammatory and oxidative environment. Moreover, oligodendrocytes provide a singular metabolic and trophic support to axons, but do not emerge unscathed from the pathological events, by primary myelin defects and cell apoptosis or secondary to neuroinflammation or axonal damage. Hereby, trophic failure might be an overlooked contributor to neurodegeneration. Thus, a complex interplay between neuroinflammation, demyelination, and neurodegeneration, wherein each is primarily and secondarily involved, might offer a more comprehensive understanding of the pathogenesis and help establishing novel therapeutic strategies for many neurological diseases and beyond.

Pathogenic myelin-specific antibodies in multiple sclerosis target conformational proteolipid protein 1-anchored membrane domains

B cell clonal expansion and cerebrospinal fluid (CSF) oligoclonal IgG bands are established features of the immune response in multiple sclerosis (MS). Clone-specific recombinant monoclonal IgG1 Abs (rAbs) derived from MS patient CSF plasmablasts bound to conformational proteolipid protein 1 (PLP1) membrane complexes and, when injected into mouse brain with human complement, recapitulated histologic features of MS pathology: oligodendrocyte cell loss, complement deposition, and CD68+ phagocyte infiltration. Conformational PLP1 membrane epitopes were complex and governed by the local cholesterol and glycolipid microenvironment. Abs against conformational PLP1 membrane complexes targeted multiple surface epitopes, were enriched within the CSF compartment, and were detected in most MS patients, but not in inflammatory and noninflammatory neurologic controls. CSF PLP1 complex Abs provide a pathogenic autoantibody biomarker specific for MS.

Neuronal binding by antibodies can be influenced by low pH stress during the isolation procedure

Low pH stress and its influence on antibody binding is a common consideration among chemists, but is only recently emerging as a consideration in Immunological studies. Antibody characterizations in Multiple Sclerosis (MS), an autoimmune disease of the Central Nervous System (CNS) has revealed that antibodies in the cerebrospinal fluid (CSF) of patients with Multiple Sclerosis bind to myelin-related and non-myelin antigen targets. Many laboratories have used molecular biology techniques to generate recombinant human antibodies (rhAbs) expressed by individual B cells from healthy donors and patients with systemic autoimmune disease to identify antigen targets. This approach has been adapted within the Neuroimmunology research community to investigate antigen targets of individual B cells in the CSF of MS patients. Our laboratory determines which antibodies to clone based on their immunogenetics and this method enriches for cloning of rhAbs that bind to neurons. However, newer technologies to assist in purification of these rhAbs from culture supernatants use an acidic elution buffer which may enhance low pH stress on the antibody structure. Our laboratory routinely uses a basic elution buffer to purify rhAbs from culture supernatants to avoid low pH stress to the antibody structure. Our goal was to investigate whether acidic elution of our rhAbs using Next Generation Chromatography would impact the rhAbs' ability to bind neurons. The limited data presented here for two neuron-binding rhAbs tested indicated that acidic elution buffers used during rhAb purification impacted the ability of rhAbs with low CDR3 charge to maintain binding to neuronal targets. Reproducibility in a larger panel of rhAbs and factors underlying these observations remain untested.

Smouldering Lesion in MS: Microglia, Lymphocytes and Pathobiochemical Mechanisms

Multiple sclerosis (MS) is an immune-mediated, chronic inflammatory, demyelinating, and neurodegenerative disease of the central nervous system (CNS). Immune cell infiltration can lead to permanent activation of macrophages and microglia in the parenchyma, resulting in demyelination and neurodegeneration. Thus, neurodegeneration that begins with acute lymphocytic inflammation may progress to chronic inflammation. This chronic inflammation is thought to underlie the development of so-called smouldering lesions. These lesions evolve from acute inflammatory lesions and are associated with continuous low-grade demyelination and neurodegeneration over many years. Their presence is associated with poor disease prognosis and promotes the transition to progressive MS, which may later manifest clinically as progressive MS when neurodegeneration exceeds the upper limit of functional compensation. In smouldering lesions, in the presence of only moderate inflammatory activity, a toxic environment is clearly identifiable and contributes to the progressive degeneration of neurons, axons, and oligodendrocytes and, thus, to clinical disease progression. In addition to the cells of the immune system, the development of oxidative stress in MS lesions, mitochondrial damage, and hypoxia caused by the resulting energy deficit and iron accumulation are thought to play a role in this process. In addition to classical immune mediators, this chronic toxic environment contains high concentrations of oxidants and iron ions, as well as the excitatory neurotransmitter glutamate. In this review, we will discuss how these pathobiochemical markers and mechanisms, alone or in combination, lead to neuronal, axonal, and glial cell death and ultimately to the process of neuroinflammation and neurodegeneration, and then discuss the concepts and conclusions that emerge from these findings. Understanding the role of these pathobiochemical markers would be important to gain a better insight into the relationship between the clinical classification and the pathomechanism of MS.

Sphingosylphosphorylcholine inhibits plasma cell differentiation and ameliorates experimental autoimmune encephalomyelitis

Introduction

Multiple sclerosis (MS) is a potentially disabling disease that damages the brain and spinal cord, inducing paralysis of the body. While MS has been known as a T-cell mediated disease, recent attention has been drawn to the involvement of B cells in its pathogenesis. Autoantibodies from B cells are closely related with the damage lesion of central nervous system and worse prognosis. Therefore, regulating the activity of antibody secreting cell could be related with the severity of the MS symptoms.

Methods

Total mouse B cells were stimulated with LPS to induce their differentiation into plasma cells. The differentiation of plasma cells was subsequently analyzed using flow cytometry and quantitative PCR analysis. To establish an experimental autoimmune encephalomyelitis (EAE) mouse model, mice were immunized with MOG^35-55/CFA emulsion.

Results

In this study, we found that plasma cell differentiation was accompanied by upregulation of autotaxin, which converts sphingosylphosphorylcholine (SPC) to sphingosine 1-phosphate in response to LPS. We observed that SPC strongly blocked plasma cell differentiation from B cells and antibody production in vitro. SPC downregulated LPS-stimulated IRF4 and Blimp 1, which are required for the generation of plasma cells. SPC-induced inhibitory effects on plasma cell differentiation were specifically blocked by VPC23019 (S1PR1/3 antagonist) or TY52159 (S1PR3 antagonist), but not by W146 (S1PR1 antagonist) and JTE013 (S1PR2 antagonist), suggesting a crucial role of S1PR3 but not S1PR1/2 in the process. Administration of SPC against an EAE mouse model significantly attenuated the symptoms of disease, showing decreased demyelinated areas of the spinal cord and decreased numbers of cells infiltrated into the spinal cord. SPC markedly decreased plasma cell generation in the EAE model, and SPC-induced therapeutic effects against EAE were not observed in μMT mice.

Conclusion

Collectively, we demonstrate that SPC strongly inhibits plasma cell differentiation, which is mediated by S1PR3. SPC also elicits therapeutic outcomes against EAE, an experimental model of MS, suggesting SPC as a new material to control MS.

Single-cell transcriptomics combined with proteomics of intrathecal IgG reveal transcriptional heterogeneity of oligoclonal IgG-secreting cells in multiple sclerosis

The phenotypes of B lineage cells that produce oligoclonal IgG in multiple sclerosis have not been unequivocally determined. Here, we utilized single-cell RNA-seq data of intrathecal B lineage cells in combination with mass spectrometry of intrathecally synthesized IgG to identify its cellular source. We found that the intrathecally produced IgG matched a larger fraction of clonally expanded antibody-secreting cells compared to singletons. The IgG was traced back to two clonally related clusters of antibody-secreting cells, one comprising highly proliferating cells, and the other consisting of more differentiated cells expressing genes associated with immunoglobulin synthesis. These findings suggest some degree of heterogeneity among cells that produce oligoclonal IgG in multiple sclerosis.

MOGAD patient autoantibodies induce complement, phagocytosis, and cellular cytotoxicity

Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) is an inflammatory demyelinating CNS condition characterized by the presence of MOG autoantibodies. We sought to investigate whether human MOG autoantibodies are capable of mediating damage to MOG-expressing cells through multiple mechanisms. We developed high-throughput assays to measure complement activity (CA), complement-dependent cytotoxicity (CDC), antibody-dependent cellular phagocytosis (ADCP), and antibody-dependent cellular cytotoxicity (ADCC) of live MOG-expressing cells. MOGAD patient sera effectively mediate all of these effector functions. Our collective analyses reveal that (a) cytotoxicity is not incumbent on MOG autoantibody quantity alone; (b) engagement of effector functions by MOGAD patient serum is bimodal, with some sera exhibiting cytotoxic capacity while others did not; (c) the magnitude of CDC and ADCP is elevated closer to relapse, while MOG-IgG binding is not; and (d) all IgG subclasses can damage MOG-expressing cells. Histopathology from a representative MOGAD case revealed congruence between lesion histology and serum CDC and ADCP, and we identified NK cells, mediators of ADCC, in the cerebrospinal fluid of relapsing patients with MOGAD. Thus, MOGAD-derived autoantibodies are cytotoxic to MOG-expressing cells through multiple mechanisms, and assays quantifying CDC and ADCP may prove to be effective tools for predicting risk of future relapses.

Understanding humoral immunity and multiple sclerosis severity in Black, and Latinx patients

People identified with Black/African American or Hispanic/Latinx ethnicity are more likely to exhibit a more severe multiple sclerosis disease course relative to those who identify as White. While social determinants of health account for some of this discordant severity, investigation into contributing immunobiology remains sparse. The limited immunologic data stands in stark contrast to the volume of clinical studies describing ethnicity-associated discordant presentation, and to advancement made in our understanding of MS immunopathogenesis over the past several decades. In this perspective, we posit that humoral immune responses offer a promising avenue to better understand underpinnings of discordant MS severity among Black/African American, and Hispanic/Latinx-identifying patients.

Neuro-immune crosstalk in depressive symptoms of multiple sclerosis

Depressive disorders can occur in up to 50% of people with multiple sclerosis in their lifetime. If left untreated, comorbid major depressive disorders may not spontaneously remit and is associated with an increased morbidity and mortality. Conversely, epidemiological evidence supports increased psychiatric visit as a significant prodromal event prior to diagnosis of MS. Are there common molecular pathways that contribute to the co-development of MS and psychiatric illnesses? We discuss immune cells that are dysregulated in MS and how such dysregulation can induce or protect against depressive symptoms. This is not meant to be a comprehensive review of all molecular pathways but rather a framework to guide future investigations of immune responses in depressed versus euthymic people with MS. Currently, there is weak evidence supporting the use of antidepressant medication in comorbid MS patients. It is our hope that by better understanding the neuroimmune crosstalk in the context of depression in MS, we can enhance the potential for future therapeutic options.

Specific myeloid signatures in peripheral blood differentiate active and rare clinical phenotypes of multiple sclerosis

Current understanding of Multiple Sclerosis (MS) pathophysiology implicates perturbations in adaptive cellular immune responses, predominantly T cells, in Relapsing-Remitting forms (RRMS). Nevertheless, from a clinical perspective MS is a heterogeneous disease reflecting the heterogeneity of involved biological systems. This complexity requires advanced analysis tools at the single-cell level to discover biomarkers for better patient-group stratification. We designed a novel 44-parameter mass cytometry panel to interrogate predominantly the role of effector and regulatory subpopulations of peripheral blood myeloid subsets along with B and T-cells (excluding granulocytes) in MS, assessing three different patient cohorts: RRMS, PPMS (Primary Progressive) and Tumefactive MS patients (TMS) (n=10, 8, 14 respectively). We further subgrouped our cohort into inactive or active disease stages to capture the early underlying events in disease pathophysiology. Peripheral blood analysis showed that TMS cases belonged to the spectrum of RRMS, whereas PPMS cases displayed different features. In particular, TMS patients during a relapse stage were characterized by a specific subset of CD11c+CD14+ CD33+, CD192+, CD172+-myeloid cells with an alternative phenotype of monocyte-derived macrophages (high arginase-1, CD38, HLA-DR-low and endogenous TNF-a production). Moreover, TMS patients in relapse displayed a selective CD4 T-cell lymphopenia of cells with a Th2-like polarised phenotype. PPMS patients did not display substantial differences from healthy controls, apart from a trend toward higher expansion of NK cell subsets. Importantly, we found that myeloid cell populations are reshaped under effective disease-modifying therapy predominantly with glatiramer acetate and to a lesser extent with anti-CD20, suggesting that the identified cell signature represents a specific therapeutic target in TMS. The expanded myeloid signature in TMS patients was also confirmed by flow cytometry. Serum neurofilament light-chain levels confirmed the correlation of this myeloid cell signature with indices of axonal injury. More in-depth analysis of myeloid subsets revealed an increase of a subset of highly cytolytic and terminally differentiated NK cells in PPMS patients with leptomeningeal enhancement (active-PPMS), compared to those without (inactive-PPMS). We have identified previously uncharacterized subsets of circulating myeloid cells and shown them to correlate with distinct disease forms of MS as well as with specific disease states (relapse/remission).

Pathogenic autoantibodies in multiple sclerosis - from a simple idea to a complex concept

The role of autoantibodies in multiple sclerosis (MS) has been enigmatic since the first description, many decades ago, of intrathecal immunoglobulin production in people with this condition. Some studies have indicated that MS pathology is heterogeneous, with an antibody-associated subtype - characterized by B cells (in varying quantities), antibodies and complement - existing alongside other subtypes with different pathologies. However, subsequent evidence suggested that some cases originally diagnosed as MS with autoantibody-mediated demyelination were more likely to be neuromyelitis optica spectrum disorder or myelin oligodendrocyte glycoprotein antibody-associated disease. These findings raise the important question of whether an autoantibody-mediated MS subtype exists and whether pathogenic MS-associated autoantibodies remain to be identified. Potential roles of autoantibodies in MS could range from specific antibodies defining the disease to a non-disease-specific amplification of cellular immune responses and other pathophysiological processes. In this Perspective, we review studies that have attempted to identify MS-associated autoantibodies and provide our opinions on their possible roles in the pathophysiology of MS.

Reemergence of pathogenic, autoantibody-producing B cell clones in myasthenia gravis following B cell depletion therapy

Myasthenia gravis (MG) is an autoantibody-mediated autoimmune disorder of the neuromuscular junction. A small subset of patients (<10%) with MG, have autoantibodies targeting muscle-specific tyrosine kinase (MuSK). MuSK MG patients respond well to CD20-mediated B cell depletion therapy (BCDT); most achieve complete stable remission. However, relapse often occurs. To further understand the immunomechanisms underlying relapse, we studied autoantibody-producing B cells over the course of BCDT. We developed a fluorescently labeled antigen to enrich for MuSK-specific B cells, which was validated with a novel Nalm6 cell line engineered to express a human MuSK-specific B cell receptor. B cells (≅ 2.6 million) from 12 different samples collected from nine MuSK MG patients were screened for MuSK specificity. We successfully isolated two MuSK-specific IgG4 subclass-expressing plasmablasts from two of these patients, who were experiencing a relapse after a BCDT-induced remission. Human recombinant MuSK mAbs were then generated to validate binding specificity and characterize their molecular properties. Both mAbs were strong MuSK binders, they recognized the Ig1-like domain of MuSK, and showed pathogenic capacity when tested in an acetylcholine receptor (AChR) clustering assay. The presence of persistent clonal relatives of these MuSK-specific B cell clones was investigated through B cell receptor repertoire tracing of 63,977 unique clones derived from longitudinal samples collected from these two patients. Clonal variants were detected at multiple timepoints spanning more than five years and reemerged after BCDT-mediated remission, predating disease relapse by several months. These findings demonstrate that a reservoir of rare pathogenic MuSK autoantibody-expressing B cell clones survive BCDT and reemerge into circulation prior to manifestation of clinical relapse. Overall, this study provides both a mechanistic understanding of MuSK MG relapse and a valuable candidate biomarker for relapse prediction.

Aberrant Immunoglobulin G Glycosylation in Multiple Sclerosis

A hallmark of the inflammatory response in multiple sclerosis (MS) is the presence of intrathecal Immunoglobulin G (IgG) antibodies and oligoclonal bands (OCBs). The biological activity of IgGs is modulated by changes in glycosylation. Using multiple immunoassays with common lectins for sialylation and galactosylation, we investigated levels of IgG glycosylation in 28 MS and 37 control sera as well as paired CSF and serum. We demonstrated the presence of significantly lower levels of IgG sialylation in MS CSF compared to paired serum. Further, we showed that in MS there was no correlation between sialylated IgG and total IgG antibodies, or between sialylated IgG in CSF and serum. ELISA with native IgG antibodies showed significantly higher levels of sialylated and galactosylated IgG in MS compared to other neurological disorders and normal healthy controls. We conclude that lower levels of sialylated intrathecal IgG and higher levels of serum IgG galactosylation in MS may play significant role in disease pathogenesis. The unique IgG glycosylation profiles suggest a complexed nature of the IgG antibodies which may influence its effector functions in MS.

The Neuroimmunology of Multiple Sclerosis: Fictions and Facts

There have been tremendous advances in the neuroimmunology of multiple sclerosis over the past five decades, which have led to improved diagnosis and therapy in the clinic. However, further advances must take into account an understanding of some of the complex issues in the field, particularly an appreciation of "facts" and "fiction." Not surprisingly given the incredible complexity of both the nervous and immune systems, our understanding of the basic biology of the disease is very incomplete. This lack of understanding has led to many controversies in the field. This review identifies some of these controversies and facts/fictions with relation to the basic neuroimmunology of the disease (cells and molecules), and important clinical issues. Fortunately, the field is in a healthy transition from excessive reliance on animal models to a broader understanding of the disease in humans, which will likely lead to many improved treatments especially of the neurodegeneration in multiple sclerosis (MS).

An appraisal of antigen identification and IgG effector functions driving host immune responses in multiple sclerosis

Increased immunoglobulin G (IgG) antibodies and oligoclonal bands (OCB) are the most characteristic features of multiple sclerosis (MS), a neuroinflammatory demyelinating disease with neurodegeneration at chronic stages. OCB are shown to be associated with disease activity and brain atrophy. Despite intensive research over the last several decades, the antigen specificities of the IgG in MS have remained elusive. We present evidence which supports that intrathecal IgG is not driven by antigen-stimulation, therefore provide reasoning for failed MS antigen identification. Further, the presence of co-deposition of IgG and activated complement products in MS lesions suggest that the IgG effector functions may play a critical role in disease pathogenesis.

B-cell depletion therapy for multiple sclerosis

Since the initial observation of increased immunoglobulin concentrations in the cerebrospinal fluid of multiple sclerosis (MS) patients in the 1940s, B cells have been considered to participate in the pathology of MS through the production of autoantibodies reactive against central nervous system antigens. However, it is now recognized that B cells contribute to MS relapses via antibody-independent activities, including the presentation of antigens to T cells and the release of pro-inflammatory cytokines. In addition, the recent identification of B cell-rich follicle-like structures in the meninges of progressive MS patients suggests that the pathogenic roles of B cells also exist at the progressive phase of this disease. Recently, large-scale clinical trials have demonstrated the efficacy of B-cell depletion therapy using anti-CD20 antibodies in relapsing as well as primary progressive MS. B-cell depletion therapy has become an essential treatment option for MS based on its unique benefit to risk balance in relapsing MS, and because it is the only drug that has been shown to be effective in primary progressive MS to date.

Elevated Concentrations of Soluble Fas and FasL in Multiple Sclerosis Patients with Antinuclear Antibodies

Antinuclear antibodies (ANA) are currently considered as an epiphenomenon of apoptotic processes, possibly in control of autoreactivity in patients with multiple sclerosis (MS). Apoptosis of reactive lymphocytes by the Fas/FasL system is described as an effective control mechanism for autoreactivity in MS. We aimed to provide a context to the potential link between ANA and peripheral lymphocyte apoptosis in MS. The presence of ANA was detected in sera by immunofluorescence assay, and concentrations of sFas and sFasL were determined in the sera of 44 and cerebrospinal fluid (CSF) of 11 relapsing-remitting (RR) MS patients using cytometric bead-based array, and their association with the disease characteristics was determined. ANA were detected in the sera of 43.2% of RRMS patients, and their frequency was the highest in patients with disease duration of less than one year (88,89%). In addition, the number of experienced relapses was lower in ANA-positive patients. Concentrations of sFasL were inversely associated with patients' expanded disability status scale (EDSS) scores. Low concentrations of both soluble factors strongly discriminated patients with moderate to severe disability, from patients with mild or absent disability only in a group of patients with prolonged disease duration (>10 years). Both soluble mediators were significantly higher in ANA-positive patients. FasL concentrations were inversely associated with the number of relapses. There is a potential link between the presence of ANA and peripheral lymphocyte apoptosis mediated by Fas/FasL system in MS, whose precise role and significance needs to be determined by future mechanistic studies.

Regulation of neuroinflammation by B cells and plasma cells

The remarkable success of anti-CD20 B cell depletion therapies in reducing the burden of multiple sclerosis (MS) disease has prompted significant interest in how B cells contribute to neuroinflammation. Most focus has been on identifying pathogenic CD20⁺ B cells. However, an increasing number of studies have also identified regulatory functions of B lineage cells, particularly the production of IL-10, as being associated with disease remission in anti-CD20-treated MS patients. Moreover, IL-10-producing B cells have been linked to the attenuation of inflammation in experimental autoimmune encephalomyelitis (EAE), the animal model of MS. In addition to IL-10-producing B cells, antibody-producing plasma cells (PCs) have also been implicated in suppressing neuroinflammation. This review will examine regulatory roles for B cells and PCs in MS and EAE. In addition, we speculate on the involvement of regulatory PCs and the cytokine BAFF in the context of anti-CD20 treatment. Lastly, we explore how the microbiota could influence anti-inflammatory B cell behavior. A better understanding of the contributions of different B cell subsets to the regulation of neuroinflammation, and factors that impact the development, maintenance, and migration of such subsets, will be important for rationalizing next-generation B cell-directed therapies for the treatment of MS.

The Role of Antibodies in the Pathogenesis of Multiple Sclerosis

The presence of persistent intrathecal oligoclonal immunoglobulin G (IgG) bands (OCBs) and lesional IgG deposition are seminal features of multiple sclerosis (MS) disease pathology. Despite extensive investigations, the role of antibodies, the products of mature CD19⁺ B cells, in disease development is still controversial and under significant debate. Recent success of B cell depletion therapies has revealed that CD20⁺ B cells contribute to MS pathogenesis via both antigen-presentation and T-cell-regulation. However, the limited efficacy of CD20⁺ B cell depletion therapies for the treatment of progressive MS indicates that additional mechanisms are involved. In this review, we present findings suggesting a potential pathological role for increased intrathecal IgGs, the relation of circulating antibodies to intrathecal IgGs, and the selective elevation of IgG1 and IgG3 subclasses in MS. We propose a working hypothesis that circulating B cells and antibodies contribute significantly to intrathecal IgGs, thereby exerting primary and pathogenic effects in MS development. Increased levels of IgG1 and IgG3 antibodies induce potent antibody-mediated cytotoxicity to central nervous system (CNS) cells and/or reduce the threshold required for antigen-driven antibody clustering leading to optimal activation of immune responses. Direct proof of the pathogenic roles of antibodies in MS may provide opportunities for novel blood biomarker identification as well as strategies for the development of effective therapeutic interventions.

Cerebrospinal Fluid IgM Levels in Association With Inflammatory Pathways in Multiple Sclerosis Patients

Background

Intrathecal immunoglobulin M (IgM) synthesis has been demonstrated in the early disease stages of multiple sclerosis (MS) as a predictor factor of a worsening disease course. Similarly, increased cerebrospinal fluid (CSF) molecules related to B-cell intrathecal activity have been associated with a more severe MS progression. However, whether CSF levels of IgM are linked to specific inflammatory and clinical profile in MS patients at the time of diagnosis remains to be elucidated.

Methods

Using customized Bio-Plex assay, the protein levels of IgG, IgA, IgM, and of 34 other inflammatory molecules, related to B-cell, T-cell, and monocyte/macrophage activity, were analyzed in the CSF of 103 newly diagnosed relapsing–remitting MS patients and 36 patients with other neurological disorders. CSF IgM levels were also correlated with clinical and neuroradiological measures [advanced 3-T magnetic resonance imaging (MRI) parameters], at diagnosis and after 2 years of follow-up.

Results

A 45.6% increase in CSF IgM levels was found in MS patients compared to controls (p = 0.013). CSF IgM levels correlated with higher CSF levels of CXCL13 (p = 0.039), CCL21 (p = 0.023), interleukin 10 (IL-10) (p = 0.025), IL-12p70 (p = 0.020), CX3CL1 (p = 0.036), and CHI3L1 (p = 0.048) and were associated with earlier age of patients at diagnosis (p = 0.008), white matter lesion (WML) number (p = 0.039) and disease activity (p = 0.033) after 2 years of follow-up.

Conclusion

IgMs are the immunoglobulins mostly expressed in the CSF of naive MS patients compared to other neurological conditions at the time of diagnosis. The association between increased CSF IgM levels and molecules related to both B-cell immunity (IL-10) and recruitment (CXCL13 and CCL21) and to macrophage/microglia activity (IL-12p70, CX3CL1, and CHI3L1) suggests possible correlation between humoral and innate intrathecal immunity in early disease stage. Furthermore, the association of IgM levels with WMLs and MS clinical and MRI activity after 2 years supports the idea of key role of IgM in the disease course.

Recombinant antibodies derived from laser captured single plasma cells of multiple sclerosis brain identified phage peptides which may be used as tools for characterizing intrathecal IgG response

Oligoclonal bands and increased IgG antibody levels can be detected in the cerebrospinal fluid in vast majority of patients with Multiple Sclerosis (MS). However, the antigenic specificity of oligoclonal IgG has yet to be determined. Using laser capture microdissection, we isolated single CD38+ plasma cells from lesion areas in two autopsy MS brains, and generated three recombinant antibodies (rAbs) from clonally expanded plasma cells. Panning phage-displayed random peptide libraries was carried out to determine peptide antigen specificities of these MS brain rAbs. We identified 25 high affinity phage peptides from which 5 peptides are unique. Database searches revealed that they shared sequence homologies with Epstein-Barr nuclear antigens 4 and 6, as well as with other viral proteins. Significantly, these peptides were recognized by intrathecal IgG and oligoclonal IgG bands in other MS patients. Our results demonstrate that functional recombinant antibodies can be generated from clonally expanded plasma cells in MS brain lesions by laser capture microdissection, and that these MS brain rAbs have the potential for determining the targets of intrathecal IgG and oligoclonal bands.

CD4+ T Cells in the Blood of MS Patients Respond to Predicted Epitopes From B cell Receptors Found in Spinal Fluid

B cells are important pathogenic players in multiple sclerosis (MS), but their exact role is not known. We have previously demonstrated that B cells from cerebrospinal fluid (CSF) of MS patients can activate T cells that specifically recognize antigenic determinants (idiotopes) from their B cell receptors (BCRs). The aim of this study was to evaluate whether in silico prediction models could identify antigenic idiotopes of immunoglobulin heavy-chain variable (IGHV) transcriptomes in MS patients. We utilized a previously assembled dataset of CSF IGHV repertoires from MS patients. To guide selection of potential antigenic idiotopes, we used in silico predicted HLA-DR affinity, endosomal processing, as well as transcript frequency from nine MS patients. Idiotopes with predicted low affinity and low likelihood of cathepsins cleavage were inert controls. Peripheral blood mononuclear cells from these patients were stimulated with the selected idiotope peptides in presence of anti-CD40 for 12 h. T cells were then labeled for activation status with anti-CD154 antibodies and CD3+CD4+ T cells phenotyped as memory (CD45RO+) or naïve (CD45RO-), with potential for brain migration (CXCR3 and/or CCR6 expression). Anti-CD14 and -CD8 were utilized to exclude monocytes and CD8+ T cells. Unstimulated cells or insulin peptides were negative controls, and EBNA-1 peptides or CD3/CD28 beads were positive controls. The mean proportion of responding memory CD4+ T cells from all nine MS patients was significantly higher for idiotope peptides with predicted high HLA-DR affinity and high likelihood of cathepsin cleavage, than toward predicted inert peptides. Responses were mainly observed toward peptides affiliated with the CDR3 region. Activated memory CD4+ T cells expressed the chemokine receptor CCR6, affiliated with a Th17 phenotype and allowing passage into the central nervous system (CNS). This in vitro study suggests that that antigenic properties of BCR idiotopes can be identified in silico using HLA affinity and endosomal processing predictions. It further indicates that MS patients have a memory T cell repertoire capable of recognizing frequent BCR idiotopes found in endogenous CSF, and that these T cells express chemokine receptors allowing them to reach the CSF B cells expressing these idiotopes.

Oligoclonal IgG antibodies in multiple sclerosis target patient-specific peptides

IgG oligoclonal bands (OCBs) are present in the cerebrospinal fluid (CSF) of more than 95% of patients with multiple sclerosis (MS), and are considered to be the immunological hallmark of disease. However, the target specificities of the IgG in MS OCBs have remained undiscovered. Nevertheless, evidence that OCBs are associated with increased levels of disease activity and disability support their probable pathological role in MS. We investigated the antigen specificity of individual MS CSF IgG from 20 OCB-positive patients and identified 40 unique peptides by panning phage-displayed random peptide libraries. Utilizing our unique techniques of phage-mediated real-time Immuno-PCR and phage-probed isoelectric focusing immunoblots, we demonstrated that these peptides were targeted by intrathecal oligoclonal IgG antibodies of IgG1 and IgG3 subclasses. In addition, we showed that these peptides represent epitopes sharing sequence homologies with proteins of viral origin, and proteins involved in cell stress, apoptosis, and inflammatory processes. Although homologous peptides were found within individual patients, no shared peptide sequences were found among any of the 42 MS and 13 inflammatory CSF control specimens. The distinct sets of oligoclonal IgG-reactive peptides identified by individual MS CSF suggest that the elevated intrathecal antibodies may target patient-specific antigens.

Identification of novel non-myelin biomarkers in multiple sclerosis using an improved phage-display approach

Although the etiology of multiple sclerosis is not yet understood, it is accepted that its pathogenesis involves both autoimmune and neurodegenerative processes, in which the role of autoreactive T-cells has been elucidated. Instead, the contribution of humoral response is still unclear, even if the presence of intrathecal antibodies and B-cells follicle-like structures in meninges of patients has been demonstrated. Several myelin and non-myelin antigens have been identified, but none has been validated as humoral biomarker. In particular autoantibodies against myelin proteins have been found also in healthy individuals, whereas non-myelin antigens have been implicated in neurodegenerative phase of the disease.

To provide further putative autoantigens of multiple sclerosis, we investigated the antigen specificity of immunoglobulins present both in sera and in cerebrospinal fluid of patients using phage display technology in a new improved format. A human brain cDNA phage display library was constructed and enriched for open-read-frame fragments. This library was selected against pooled and purified immunoglobulins from cerebrospinal fluid and sera of multiple sclerosis patients. The antigen library was also screened against an antibody scFv library obtained from RNA of B cells purified from the cerebrospinal fluid of two relapsing remitting patients. From all biopanning a complex of 14 antigens were identified; in particular, one of these antigens, corresponding to DDX24 protein, was present in all selections. The ability of more frequently isolated antigens to discriminate between sera from patients with multiple sclerosis or other neurological diseases was investigated. The more promising novel candidate autoantigens were DDX24 and TCERG1. Both are implicated in RNA modification and regulation which can be altered in neurodegenerative processes. Therefore, we propose that they could be a marker of a particular disease activity state.

Role of B cells and antibodies in multiple sclerosis

Multiple sclerosis (MS) is a chronically progressive auto-immune mediated inflammatory demyelinating disease of the central nervous system (CNS) which manifests as disturbances in sensorimotor function and cognitive impairment. Although believed to be a T-cell mediated disease, the role of B cells has recently become a central issue in MS pathogenesis. Both antibody dependent and independent theories have been suggested to play a role in the initiation of inflammatory demyelination. Antibody dependent mechanisms include formation of autoantibodies targeting specific tissues in the CNS and B cell antigen presentation to T cells, leading to subsequent activation and cytokine secretion. Antibody independent mechanisms entail formation of ectopic lymphoid structures, cytokine production and secretion of neurotoxic factors. Moreover, breach of peripheral tolerance mechanisms due to disturbances in regulatory T cell functioning has also been described. B cell depletion through anti-CD20 monoclonal antibody utilization and other immunomodulatory therapies have been promising in reducing episodes of relapse and slowing progression, further strengthening the concept that B cells and antibodies are significant players in formation of brain lesions in MS.

Impact of B cells to the pathophysiology of multiple sclerosis

Introduction

Multiple sclerosis (MS) is a chronic autoimmune disorder that affects the central nervous system and compromises the health and well-being of millions of people worldwide. B cells have been linked to MS and its progression. This review aimed to determine the role of B cells in MS development.

Methods

Articles used in this review were obtained from PubMed, LILACS, and EBSCO. The search terms and phrases included “multiple sclerosis,” “MS,” “B-Cells,” “pathogenesis,” and “development.” Original research studies and articles on MS and B cells published between 2007 and 2018 were included.

Results

Results from the selected articles showed a significant connection between B cell groups and MS. B cells act as a significant source of plasma cells, which generate antibodies while also regulating autoimmune processes and T cell production. In addition, B cells regulate the release of molecules that affect the proinflammatory actions of other immune cells.

Discussion

B cells play key roles in immune system functioning and MS. The findings of this review illustrate the complex nature of B cell actions, their effects on the autoimmune system, and the method by which they contribute to MS pathogenesis.

Conclusion

Previous research implicates biological, genetic, and environmental factors in MS pathogenesis. This review suggests that B cells contribute to MS development and advancement by influencing and regulating autoimmune processes such as T cell production and APC activity.

Characterization of pathogenic monoclonal autoantibodies derived from muscle-specific kinase myasthenia gravis patients

Myasthenia gravis (MG) is a chronic autoimmune disorder characterized by muscle weakness and caused by pathogenic autoantibodies that bind to membrane proteins at the neuromuscular junction. Most patients have autoantibodies against the acetylcholine receptor (AChR), but a subset of patients have autoantibodies against muscle-specific tyrosine kinase (MuSK) instead. MuSK is an essential component of the pathway responsible for synaptic differentiation, which is activated by nerve-released agrin. Through binding MuSK, serum-derived autoantibodies inhibit agrin-induced MuSK autophosphorylation, impair clustering of AChRs, and block neuromuscular transmission. We sought to establish individual MuSK autoantibody clones so that the autoimmune mechanisms could be better understood. We isolated MuSK autoantibody-expressing B cells from 6 MuSK MG patients using a fluorescently tagged MuSK antigen multimer, then generated a panel of human monoclonal autoantibodies (mAbs) from these cells. Here we focused on 3 highly specific mAbs that bound quantitatively to MuSK in solution, to MuSK-expressing HEK cells, and at mouse neuromuscular junctions, where they colocalized with AChRs. These 3 IgG isotype mAbs (2 IgG4 and 1 IgG3 subclass) recognized the Ig-like domain 2 of MuSK. The mAbs inhibited AChR clustering, but intriguingly, they enhanced rather than inhibited MuSK phosphorylation, which suggests an alternative mechanism for inhibiting AChR clustering.

A fluorescent tetrameric antigen allows isolation of human myasthenia gravis monoclonal antibodies that interrupt acetylcholine receptor signaling.

An automated microfluidic system for selection of aptamer probes against ovarian cancer tissues

Because of the difficulty of treatment in its latest stages, cancer is among the leading causes of death worldwide. Therefore, high-affinity and specificity biomarkers are still in demand for many cancer types, and the utility of aptamers to serve in this regard has been explored recently. Although a process known as "systematic evolution of ligands by exponential enrichment" (SELEX) has been used to generate aptamer-based cancer biomarkers, this approach is complicated, time-consuming, and labor-intensive. An automated microfluidic system was consequently developed herein to screen ovarian cancer-specific aptamers via on-chip SELEX with clinical cancer tissue samples. The integrated microfluidic system consisted of an integrated microfluidic chip, a temperature control module equipped with 12 thermoelectric coolers, and a flow control module for controlling 36 electromagnetic valves such that the entire, tissue-based SELEX process could be fully automated and carried out within 15 h. Highly specific ovarian cancer aptamers with high affinity (dissociation constant of 129 nM) to their cellular targets were screened with this system. Given the comparable specificity to their much more expensive antibody counterparts, these aptamers, when used in conjunction with the developed microfluidic system, may be used to diagnose ovarian cancer in its earliest stages.

G1m1 predominance of intrathecal virus-specific antibodies in multiple sclerosis

We have previously shown that plasmablasts of the G1m1 allotype of IgG1 are selectively enriched in the cerebrospinal fluid of G1m1/G1m3 heterozygous patients with multiple sclerosis, whereas both allotypes are equally used in neuroborreliosis. Here, we demonstrate a strong preference for the G1m1 allotype in the intrathecal humoral immune responses against measles, rubella, and varicella zoster virus in G1m1/G1m3 heterozygous multiple sclerosis patients. Conversely, intrathecally synthesized varicella zoster virus‐specific IgG1 in varicella zoster virus meningoencephalitis comprised both allotypes. This implies that G1m1 B cells are selected to the central nervous system of multiple sclerosis patients regardless of specificity and suggests that an antigen‐independent mechanism could drive the intrathecal humoral immune response.

Emerging Role of Follicular T Helper Cells in Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disorder where both T cells and B cells are implicated in pathology. However, it remains unclear how these two distinct populations cooperate to drive disease. There is ample evidence from studies in both MS patients and mouse models that Th17, B cells, and follicular T helper (TFH) cells contribute to disease. This review article describes the literature that identifies mechanisms by which Th17, TFH, and B cells cooperatively drive disease activity in MS and experimental autoimmune encephalomyelitis (EAE). The curation of this literature has identified that central nervous system (CNS) infiltrating TFH cells act with TH17 cell to contribute to an inflammatory B cell response in neuroinflammation. This demonstrates that TFH cells and their products are promising targets for therapies in MS.

Distinct patterns of glia repair and remyelination in antibody-mediated demyelination models of multiple sclerosis and neuromyelitis optica

Multiple sclerosis (MS) and neuromyelitis optica (NMO) are inflammatory demyelinating disorders of the central nervous system with evidence of antibody-mediated pathology. Using ex vivo organotypic mouse cerebellar slice cultures, we have demonstrated that recombinant antibodies (rAbs) cloned from cerebrospinal fluid plasmablasts of MS and NMO patients target myelin- and astrocyte-specific antigens to induce disease-specific oligodendrocyte loss and myelin degradation. In this study, we examined glial cell responses and myelin integrity during recovery from disease-specific antibody-mediated injury. Following exposure to MS rAb and human complement (HC) in cerebellar explants, myelinating oligodendrocytes repopulated the demyelinated tissue and formed new myelin sheaths along axons. Remyelination was accompanied by pronounced microglial activation. In contrast, following treatment with NMO rAb and HC, there was rapid regeneration of astrocytes and pre-myelinating oligodendrocytes but little formation of myelin sheaths on preserved axons. Deficient remyelination was associated with progressive axonal loss and the return of microglia to a resting state. Our results indicate that antibody-mediated demyelination in MS and NMO show distinct capacities for recovery associated with differential injury to adjacent axons and variable activation of microglia. Remyelination was rapid in MS rAb plus HC-induced demyelination. By contrast, oligodendrocyte maturation and remyelination failed following NMO rAb-mediated injury despite the rapid restoration of astrocytes and preservation of axons in early lesions.

Glucose-regulated protein 78 autoantibody associates with blood-brain barrier disruption in neuromyelitis optica

Neuromyelitis optica (NMO) is an inflammatory disorder mediated by antibodies to aquaporin-4 (AQP4) with prominent blood-brain barrier (BBB) breakdown in the acute phase of the disease. Anti-AQP4 antibodies are produced mainly in the periphery, yet they target the astrocyte perivascular end feet behind the BBB. We reasoned that an endothelial cell-targeted autoantibody might promote BBB transit of AQP4 antibodies and facilitate NMO attacks. Using monoclonal recombinant antibodies (rAbs) from patients with NMO, we identified two that strongly bound to the brain microvascular endothelial cells (BMECs). Exposure of BMECs to these rAbs resulted in nuclear translocation of nuclear factor κB p65, decreased claudin-5 protein expression, and enhanced transit of macromolecules. Unbiased membrane proteomics identified glucose-regulated protein 78 (GRP78) as the rAb target. Using immobilized GRP78 to deplete GRP78 antibodies from pooled total immunoglobulin G (IgG) of 50 NMO patients (NMO-IgG) reduced the biological effect of NMO-IgG on BMECs. GRP78 was expressed on the surface of murine BMECs in vivo, and repeated administration of a GRP78-specific rAb caused extravasation of serum albumin, IgG, and fibrinogen into mouse brains. Our results identify GRP78 antibodies as a potential component of NMO pathogenesis and GRP78 as a candidate target for promoting central nervous system transit of therapeutic antibodies.

B-cell Therapy for Multiple Sclerosis: Entering an era

Monoclonal antibodies that target CD20 expressing B cells represent an important new treatment option for patients with multiple sclerosis (MS). B-cell-depleting therapy is highly effective against relapsing forms of the disease and is also the first treatment approach proven to protect against disability worsening in primary progressive MS. Moreover, evolving clinical experience with B-cell therapy, combined with a more sophisticated understanding of humoral immunity in preclinical models and in patients with MS, has led to major progress in deciphering the immune pathogenesis of MS. Here, we review the nuanced roles of B cells in MS autoimmunity, the clinical data supporting use of ocrelizumab and other anti-CD20 therapies in the treatment of MS, as well as safety and practical considerations for prescribing. Last, we summarize remaining unanswered questions regarding the proper role of anti-CD20 therapy in MS, its limitations, and the future landscape of B-cell-based approaches to treatment. Ann Neurol 2018;83:13-26.

Intrathecal oligoclonal bands synthesis in multiple sclerosis: is it always a prognostic factor?

BACKGROUND

Oligoclonal IgM (OCMB) and IgG (OCGB) bands were found to be associated with poor multiple sclerosis (MS) prognosis.

OBJECTIVE

We aimed to evaluate the prognostic value of OCMB/OCGB in a cohort of Sardinian MS patients.

MATERIALS AND METHODS

We recruited patients from the University of Cagliari. They underwent lumbar puncture for diagnostic purposes. Demographic and the following clinical data were recorded: clinical course; time to reach EDSS 3 and 6; EDSS at last follow-up; and MS treatments. The influence of gender, clinical course, age at onset, treatments, and OCGB/OCMB on reaching EDSS 3 was analysed using Cox regression. Kaplan-Meier curves were used to study the time to reach EDSS 3 considering OCMB/OCGB and therapies.

RESULTS

The enrolled number of subjects was 503. The variables influencing the achievement of EDSS 3.0 were: male gender (p = 0.005); progressive course (p = 0.001); age at onset (p < 0.001); and disease-modifying drugs (p < 0.001). The OCGB/OCMB status was not significant. Kaplan-Meier analysis showed no difference in time to reach EDSS 3 for patients with and without OCGB or OCMB in both treated and non-treated groups.

CONCLUSION

Our study did not confirm the poor prognostic value of OCMB/OCGB. These results may be influenced by the peculiar genetic background associated with the risk of MS in Sardinians.

In Silico Prediction Analysis of Idiotope-Driven T-B Cell Collaboration in Multiple Sclerosis

Memory B cells acting as antigen-presenting cells are believed to be important in multiple sclerosis (MS), but the antigen they present remains unknown. We hypothesized that B cells may activate CD4⁺ T cells in the central nervous system of MS patients by presenting idiotopes from their own immunoglobulin variable regions on human leukocyte antigen (HLA) class II molecules. Here, we use bioinformatics prediction analysis of B cell immunoglobulin variable regions from 11 MS patients and 6 controls with other inflammatory neurological disorders (OINDs), to assess whether the prerequisites for such idiotope-driven T–B cell collaboration are present. Our findings indicate that idiotopes from the complementarity determining region (CDR) 3 of MS patients on average have high predicted affinities for disease associated HLA-DRB1*15:01 molecules and are predicted to be endosomally processed by cathepsin S and L in positions that allows such HLA binding to occur. Additionally, complementarity determining region 3 sequences from cerebrospinal fluid (CSF) B cells from MS patients contain on average more rare T cell-exposed motifs that could potentially escape tolerance and stimulate CD4⁺ T cells than CSF B cells from OIND patients. Many of these features were associated with preferential use of the IGHV4 gene family by CSF B cells from MS patients. This is the first study to combine high-throughput sequencing of patient immune repertoires with large-scale prediction analysis and provides key indicators for future in vitro and in vivo analyses.

Ocrelizumab: a B-cell depleting therapy for multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is the most common neurological disease responsible for early disability in the young working population. In the last two decades, based on retrospective/prospective data, the use of disease-modifying therapies has been shown to slow the rate of disability progression and prolonged the time to conversion into secondary-progressive MS (SPMS). However, despite the availability of several approved therapies, disability progression cannot be halted significantly in all MS patients. Areas covered: This article reviews the immunopathology of the B-cells, and their role in pathogenesis of MS and their attractiveness as a potential therapeutic target in MS. The review focuses on the recently published ocrelizumab phase III trials in terms of its efficacy, safety, and tolerability as well as its future considerations. Expert opinion: B lymphocyte cell depletion therapy offers a compelling and promising new option for MS patients. Nonetheless, there is a need for heightened vigilance and awareness in detecting potential long-term consequences that currently remain unknown.

Galectin-8 as an immunosuppressor in experimental autoimmune encephalomyelitis and a target of human early prognostic antibodies in multiple sclerosis

Galectin-8 (Gal-8) is a member of a glycan-binding protein family that regulates the immune system, among other functions, and is a target of antibodies in autoimmune disorders. However, its role in multiple sclerosis (MS), an autoimmune inflammatory disease of the central nervous system (CNS), remains unknown. We study the consequences of Gal-8 silencing on lymphocyte subpopulations and the development of experimental autoimmune encephalitis (EAE), to then assess the presence and clinical meaning of anti-Gal-8 antibodies in MS patients. Lgals8/Lac-Z knock-in mice lacking Gal-8 expression have higher polarization toward Th17 cells accompanied with decreased CCR6⁺ and higher CXCR3⁺ regulatory T cells (Tregs) frequency. These conditions result in exacerbated MOG_35-55 peptide-induced EAE. Gal-8 eliminates activated Th17 but not Th1 cells by apoptosis and ameliorates EAE in C57BL/6 wild-type mice. β-gal histochemistry reflecting the activity of the Gal-8 promoter revealed Gal-8 expression in a wide range of CNS regions, including high expression in the choroid-plexus. Accordingly, we detected Gal-8 in human cerebrospinal fluid, suggesting a role in the CNS immune-surveillance circuit. In addition, we show that MS patients generate function-blocking anti-Gal-8 antibodies with pathogenic potential. Such antibodies block cell adhesion and Gal-8-induced Th17 apoptosis. Furthermore, circulating anti-Gal-8 antibodies associate with relapsing-remitting MS (RRMS), and not with progressive MS phenotypes, predicting clinical disability at diagnosis within the first year of follow-up. Our results reveal that Gal-8 has an immunosuppressive protective role against autoimmune CNS inflammation, modulating the balance of Th17 and Th1 polarization and their respective Tregs. Such a role can be counteracted during RRMS by anti-Gal-8 antibodies, worsening disease prognosis. Even though anti-Gal-8 antibodies are not specific for MS, our results suggest that they could be a potential early severity biomarker in RRMS.

Effector and regulatory B cells in Multiple Sclerosis

The role of B cells in the pathogenesis of Multiple Sclerosis (MS), an autoimmune neurodegenerative disease, is becoming eminent in recent years, but the specific contribution of the distinct B cell subsets remains to be elucidated. Several B cell subsets have shown regulatory, anti-inflammatory capacities in response to stimuli in vitro, as well as in the animal model of MS: Experimental Autoimmune Encephalomyelitis (EAE). However, the functional role of the B regulatory cells (Bregs) in vivo and specifically in the human disease is yet to be clarified. In the present review, we have summarized the updated information on the roles of effector and regulatory B cells in MS and the immune-modulatory effects of MS therapeutic agents on their phenotype and function.

Myelin-specific multiple sclerosis antibodies cause complement-dependent oligodendrocyte loss and demyelination

Intrathecal immunoglobulin G (IgG) synthesis, cerebrospinal fluid (CSF) oligoclonal IgG bands and lesional IgG deposition are seminal features of multiple sclerosis (MS) disease pathology. Both the specific targets and pathogenic effects of MS antibodies remain poorly characterized. We produced IgG1 monoclonal recombinant antibodies (rAbs) from clonally-expanded plasmablasts recovered from MS patient CSF. Among these were a subset of myelin-specific MS rAbs. We examined their immunoreactivity to mouse organotypic cerebellar slices by live binding and evaluated tissue injury in the presence and absence of human complement. Demyelination, glial and neuronal viability, and complement pathway activation were assayed by immunofluorescence microscopy and compared to the effects of an aquaporin-4 water channel (AQP4)-specific rAb derived from a neuromyelitis optica (NMO) patient. MS myelin-specific rAbs bound to discrete surface domains on oligodendrocyte processes and myelinating axons. Myelin-specific MS rAbs initiated complement-dependent cytotoxicity to oligodendrocytes and induced rapid demyelination. Demyelination was accompanied by increased microglia activation; however, the morphology and survival of astrocytes, oligodendrocyte progenitors and neurons remained unaffected. In contrast, NMO AQP4-specific rAb initiated complement-dependent astrocyte damage, followed by sequential loss of oligodendrocytes, demyelination, microglia activation and neuronal death. Myelin-specific MS antibodies cause oligodendrocyte loss and demyelination in organotypic cerebellar slices, which are distinct from AQP4-targeted pathology, and display seminal features of active MS lesions. Myelin-specific antibodies may play an active role in MS lesion formation through complement-dependent mechanisms.

BAFF Index and CXCL13 levels in the cerebrospinal fluid associate respectively with intrathecal IgG synthesis and cortical atrophy in multiple sclerosis at clinical onset

BACKGROUND

B lymphocytes are thought to play a relevant role in multiple sclerosis (MS) pathology. The in vivo analysis of intrathecally produced B cell-related cytokines may help to clarify the mechanisms of B cell recruitment and immunoglobulin production within the central nervous system (CNS) in MS.

METHODS

Paired cerebrospinal fluid (CSF) and serum specimens from 40 clinically isolated syndrome suggestive of MS or early-onset relapsing-remitting MS patients (CIS/eRRMS) and 17 healthy controls (HC) were analyzed for the intrathecal synthesis of IgG (quantitative formulae and IgG oligoclonal bands, IgGOB), CXCL13, BAFF, and IL-21. 3D-FLAIR, 3D-DIR, and 3D-T1 MRI sequences were applied to evaluate white matter (WM) and gray matter (GM) lesions and global cortical thickness (gCTh).

RESULTS

Compared to HC, CIS/eRRMS having IgGOB (IgGOB+, 26 patients) had higher intrathecal IgG indexes (p < 0.01), lower values of BAFF Index (11.9 ± 6.1 vs 17.5 ± 5.2, p < 0.01), and higher CSF CXCL13 levels (27.7 ± 33.5 vs 0.9 ± 1.5, p < 0.005). In these patients, BAFF Index but not CSF CXCL13 levels inversely correlated with the intrathecal IgG synthesis (r > 0.5 and p < 0.05 for all correlations). CSF leukocyte counts were significantly higher in IgGOB+ compared to IgGOB- (p < 0.05) and HC (p < 0.01), and correlated to CSF CXCL13 concentrations (r 0.77, p < 0.001). The gCTh was significantly lower in patients with higher CSF CXCL13 levels (2.41 ± 0.1 vs 2.49 ± 0.1 mm, p < 0.05), while no difference in MRI parameters of WM and GM pathology was observed between IgGOB+ and IgGOB-.

CONCLUSIONS

The intrathecal IgG synthesis inversely correlated with BAFF Index and showed no correlation with CSF CXCL13. These findings seem to indicate that intrathecally synthesized IgG are produced by long-term PCs that have entered the CNS from the peripheral blood, rather than produced by PCs developed in the meningeal follicle-like structures (FLS). In this study, CXCL13 identifies a subgroup of MS patients characterized by higher leukocyte counts in the CSF and early evidence of cortical thinning, further suggesting a role for this chemokine as a possible marker of disease severity.

Peripheral VH4+ plasmablasts demonstrate autoreactive B cell expansion toward brain antigens in early multiple sclerosis patients

Plasmablasts are a highly differentiated, antibody secreting B cell subset whose prevalence correlates with disease activity in Multiple Sclerosis (MS). For most patients experiencing partial transverse myelitis (PTM), plasmablasts are elevated in the blood at the first clinical presentation of disease (known as a clinically isolated syndrome or CIS). In this study we found that many of these peripheral plasmablasts are autoreactive and recognize primarily gray matter targets in brain tissue. These plasmablasts express antibodies that over-utilize immunoglobulin heavy chain V-region subgroup 4 (VH4) genes, and the highly mutated VH4+ plasmablast antibodies recognize intracellular antigens of neurons and astrocytes. Most of the autoreactive, highly mutated VH4+ plasmablast antibodies recognize only a portion of cortical neurons, indicating that the response may be specific to neuronal subgroups or layers. Furthermore, CIS-PTM patients with this plasmablast response also exhibit modest reactivity toward neuroantigens in the plasma IgG antibody pool. Taken together, these data indicate that expanded VH4+ peripheral plasmablasts in early MS patients recognize brain gray matter antigens. Peripheral plasmablasts may be participating in the autoimmune response associated with MS, and provide an interesting avenue for investigating the expansion of autoreactive B cells at the time of the first documented clinical event.

Inebilizumab, a B Cell-Depleting Anti-CD19 Antibody for the Treatment of Autoimmune Neurological Diseases: Insights from Preclinical Studies

Exaggerated or inappropriate responses by B cells are an important feature in many types of autoimmune neurological diseases. The recent success of B-cell depletion in the treatment of multiple sclerosis (MS) has stimulated the development of novel B-cell-targeting therapies with the potential for improved efficacy. CD19 has emerged as a promising target for the depletion of B cells as well as CD19-positive plasmablasts and plasma cells. Inebilizumab (MEDI-551), an anti-CD19 antibody with enhanced antibody-dependent cell-mediated cytotoxicity against B cells, is currently being evaluated in MS and neuromyelitis optica. This review discusses the role of B cells in autoimmune neurological disorders, summarizes the development of inebilizumab, and analyzes the recent results for inebilizumab treatment in an autoimmune encephalitis mouse model. The novel insights obtained from these preclinical studies can potentially guide future investigation of inebilizumab in patients.

Viral Infection of the Central Nervous System Exacerbates Interleukin-10 Receptor Deficiency-Mediated Colitis in SJL Mice

Theiler´s murine encephalomyelitis virus (TMEV)-infection is a widely used animal model for studying demyelinating disorders, including multiple sclerosis (MS). The immunosuppressive cytokine Interleukin (IL)-10 counteracts hyperactive immune responses and critically controls immune homeostasis in infectious and autoimmune disorders. In order to investigate the effect of signaling via Interleukin-10 receptor (IL-10R) in infectious neurological diseases, TMEV-infected SJL mice were treated with IL-10R blocking antibody (Ab) in the acute and chronic phase of the disease. The findings demonstrate that (i) Ab-mediated IL-10 neutralization leads to progressive colitis with a reduction in Foxp3+ regulatory T cells and increased numbers of CD8+CD44+ memory T cells as well as activated CD4+CD69+ and CD8+CD69+ T cells in uninfected mice. (ii) Concurrent acute TMEV-infection worsened enteric disease-mediated by IL-10R neutralization. Virus-triggered effects were associated with an enhanced activation of CD4+ T helper cells and CD8+ cytotoxic T lymphocytes and augmented cytokine expression. By contrast, (iii) IL-10R neutralization during chronic TMEV-infection was not associated with enhanced peripheral immunopathology but an increased CD3+ T cell influx in the spinal cord. IL-10R neutralization causes a breakdown in peripheral immune tolerance in genetically predisposed mice, which leads to immune-mediated colitis, resembling inflammatory bowel disease. Hyperactive immune state following IL-10R blockade is enhanced by central nervous system-restricted viral infection in a disease phase-dependent manner.