Central Nervous System Antigens Research Articles

Cellular Contributions to Glymphatic and Lymphatic Waste Clearance in the Brain.

Cerebrospinal fluid (CSF) bathes and cushions the brain; however, it also serves a major role in the clearance of metabolic wastes and in the distribution of glucose, lipids, and amino acids. Unlike every other organ in the body, the brain parenchyma lacks a traditional lymphatic system to drain fluids and central nervous system (CNS) antigens. It was historically assumed that all brain wastes were removed by endogenous processing, such as phagocytosis and autophagy, while excess fluids drained directly into the blood. However, the twin discoveries of the glial-lymphatic (glymphatic) system and meningeal lymphatics have transformed our understanding of brain waste clearance. The glymphatic system describes the movement of fluids through the subarachnoid space (SAS), the influx along periarterial spaces into the brain parenchyma, and the ultimate efflux back into the SAS along perivenous spaces where it comes into direct contact with the meningeal lymphatics. The dura mater of the meninges contains a bona fide lymphatic network that can drain CSF that has entered the dura. Together, these pathways provide insights into the clearance of molecules and fluids from the brain, and show that the CNS is physically connected to the adaptive immune system. Here, we outline the glymphatic and lymphatic systems, and describe the cellular components that are important to their function.

Human stem cell-derived neurons and astrocytes to detect novel auto-reactive IgG response in immune-mediated neurological diseases.

Up to 46% of patients with presumed autoimmune limbic encephalitis are seronegative for all currently known central nervous system (CNS) antigens. We developed a cell-based assay (CBA) to screen for novel neural antibodies in serum and cerebrospinal fluid (CSF) using neurons and astrocytes derived from human-induced pluripotent stem cells (hiPSCs). Human iPSC-derived astrocytes or neurons were incubated with serum/CSF from 99 patients [42 with inflammatory neurological diseases (IND) and 57 with non-IND (NIND)]. The IND group included 11 patients with previously established neural antibodies, six with seronegative neuromyelitis optica spectrum disorder (NMOSD), 12 with suspected autoimmune encephalitis/paraneoplastic syndrome (AIE/PNS), and 13 with other IND (OIND). IgG binding to fixed CNS cells was detected using fluorescently-labeled antibodies and analyzed through automated fluorescence measures. IgG neuronal/astrocyte reactivity was further analyzed by flow cytometry. Peripheral blood mononuclear cells (PBMCs) were used as CNS-irrelevant control target cells. Reactivity profile was defined as positive using a Robust regression and Outlier removal test with a false discovery rate at 10% following each individual readout. Using our CBA, we detected antibodies recognizing hiPSC-derived neural cells in 19/99 subjects. Antibodies bound specifically to astrocytes in nine cases, to neurons in eight cases, and to both cell types in two cases, as confirmed by microscopy single-cell analyses. Highlighting the significance of our comprehensive 96-well CBA assay, neural-specific antibody binding was more frequent in IND (15 of 42) than in NIND patients (4 of 57) (Fisher's exact test, p = 0.0005). Two of four AQP4+ NMO and four of seven definite AIE/PNS with intracellular-reactive antibodies [1 GFAP astrocytopathy, 2 Hu+, 1 Ri+ AIE/PNS)], as identified in diagnostic laboratories, were also positive with our CBA. Most interestingly, we showed antibody-reactivity in two of six seronegative NMOSD, six of 12 probable AIE/PNS, and one of 13 OIND. Flow cytometry using hiPSC-derived CNS cells or PBMC-detected antibody binding in 13 versus zero patients, respectively, establishing the specificity of the detected antibodies for neural tissue. Our unique hiPSC-based CBA allows for the testing of novel neuron-/astrocyte-reactive antibodies in patients with suspected immune-mediated neurological syndromes, and negative testing in established routine laboratories, opening new perspectives in establishing a diagnosis of such complex diseases.

Skull bone marrow serves as a niche of adaptive immunity for CNS immunosurveillance

Abstract The central nervous system (CNS) has been considered as an ‘immune-privileged’ organ owing to limited graft- and cancer-rejection, as well as the absence of lymphocytes and lymphatics. However, recent findings unveiled that the immune system actively discerns the status of the CNS through the glymphatic system and meningeal lymphatics. There is a diverse immune repertoire in the CNS borders presenting antigen, affecting behaviors, and defending CNS tissues. Recent studies discovered the channels in the skull bone marrow (SBM), exchanging immune cells and cerebrospinal fluid (CSF). Consequently, molecular exchange and immune cell activation occur in the CNS border, including SBM, like mucosal tissues. Nevertheless, the mechanism responding to CNS antigens and the maintenance of tolerance is unclear. In this study, we noted greater activation and differentiation of T/ B cells in the SBM than dura mater and other BMs. SBM displayed premature features of lymphoid structures, encompassing Tfh, activated B cells, and antibody-secreting cells. We also observed that Tfh cells directly interacted with B cells and induced differentiation. Moreover, our observations indicated that skull T/B cells respond to CNS antigens, but not microbial/food antigen. Thus, our study suggests that the SBM is a niche for adaptive immune cells in response to CNS antigens. The SBM may sustain heightened inflammatory states to promptly counteract tumorigenesis and pathogen invasion, protecting CNS.

Complete Freund's adjuvant as a confounding factor in multiple sclerosis research.

Complete Freund's adjuvant (CFA) is used as a standard adjuvant for the induction of experimental autoimmune encephalomyelitis (EAE), the most commonly used animal model in multiple sclerosis studies. Still, CFA induces glial activation and neuroinflammation on its own and provokes pain. In addition, as CFA contains Mycobacteria, an immune response against bacterial antigens is induced in parallel to the response against central nervous system antigens. Thus, CFA can be considered as a confounding factor in multiple sclerosis-related studies performed on EAE. Here, we discuss the effects of CFA in EAE in detail and present EAE variants induced in experimental animals without the use of CFA. We put forward CFA-free EAE variants as valuable tools for studying multiple sclerosis pathogenesis and therapeutic approaches.

The prevalence of IgG antibodies against milk and milk antigens in patients with multiple sclerosis.

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system (CNS). The pathophysiology of MS is complex and is said to be influenced by multiple environmental determinants, including diet. We and others have previously demonstrated how consumption of bovine milk can aggravate disease severity in MS patients, which can be explained by molecular mimicry between milk antigens and those expressed within the CNS. In this study we set out to identify alternatives to drinking cow milk which might be less detrimental to MS patients who have a genetic predisposition towards developing antibody titers against bovine milk antigens that cross-react with CNS antigens. To this end, we screened 35 patients with MS and 20 healthy controls for their IgG reactivity against an array of animal-sourced milk, plant-based alternatives as well as individual antigens from bovine milk. We demonstrate that MS patients have a significantly higher IgG response to animal-sourced milk, especially cow milk, in comparison to healthy donors. We also show that the reactivity to cow milk in MS patients can be attributed to reactivity against different bovine milk antigens. Finally, our correlation data indicate the co-existence of antibodies to individual bovine milk antigens and their corresponding cross-reactive CNS antigens. Taken together, we suggest screening of blood from MS patients for antibodies against different types of milk and milk antigens in order to establish a personalized diet regimen.

Cladribine Effects on T and B Cells and T Cell Reactivity in Multiple Sclerosis.

Cladribine tablet therapy is an efficacious treatment for multiple sclerosis (MS), however, its mechanism of action on T and B cell subsets remains unclear. The purpose of this study was to investigate the treatment effects of cladribine on the peripheral pool of T and B cells subsets and reactivity toward central nervous system (CNS) antigens. In this cross-sectional exploratory study, frequencies and absolute counts of peripheral T and B cell subsets and B cell cytokine production from untreated patients with relapsing-remitting MS (RRMS) and patients treated with cladribine for 1 year were measured using flow cytometry. Autoreactivity was assessed using a FluoroSpot assay. We found that 1 year after initiation of cladribine treatment, a lower number of CD4+ T cells was persisting whereas CD19+ B cell counts were normalized compared to untreated patients with RRMS. Follicular helper T cells and their effecter subsets producing cytokines exerting distinct B cell helper activity were lower and, additionally, the peripheral B cell pool was skewed toward a naïve and anti-inflammatory phenotype. Finally, reactivity to the recently identified CNS-enriched autoantigen RAS guanyl-releasing protein 2 (RASGRP2), but not to myelin basic protein and myelin oligodendrocyte glycoprotein, was lower in cladribine-treated patients. Together, these investigations on T and B cell subsets suggest that cladribine treatment impairs the B-T cell crosstalk and reduces their ability to mediate pathogenic effector functions. This may result in specific reduction of autoreactivity to RASGRP2 which is expressed in B cells and brain tissue. ANN NEUROL 2023.

Meningeal lymphatic vasculature, a general target for glioblastoma therapy?

Glioblastoma (GBM) causes nearly universal mortality as a result of the failure of conventional therapies including surgical resection, targeted radiation therapy, and chemotherapy. An increasingly important treatment option is combining immunotherapy with other therapies in both preclinical and clinical studies. The central nervous system (CNS) has been historically considered an immune privileged area, but increasing evidence, including the recent rediscovery of meningeal lymphatic vessels (MLVs), has overturned this notion. MLVs are populated by multiple immune cells and connect the CNS to the periphery by draining cerebrospinal fluid with soluble CNS antigens and immune cells into cervical lymph nodes. In the past few years, more and more studies have indicated that MLVs are involved in the regulation of inflammation and the immune response in the pathogenesis of various CNS diseases including GBM. Here, we explore the critical interlinkages between MLVs and GBM therapies including chemotherapy, radiotherapy and immunotherapy, and propose the meningeal lymphatic vasculature as a general target for GBM therapy.

In silico prediction of the miRNAs targeting CYBRD1, SMAD1 and GNG12 genes in multiple sclerosis (MS)

MS is a devastating disease of the Central Nervous System (CNS) caused by autoimmune responses to CNS antigens such as myelin basic protein

Designing and Characterization of Tregitope-Based Multi-Epitope Vaccine Against Multiple Sclerosis: An Immunoinformatic Approach.

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system(CNS). It is widely accepted that the development and progression of MS result from aberrant activation of potentially encephalitogenic reactive-T cells against CNS antigens. The pathologic roles of both CD4+ (T helper; Th) and CD8+ T cells have been demonstrated in MS lesions. In the present work, we applied a series of bioinformatics tools to design a dendritic cell (DC)-targeting Tregitope-based multi-epitope vaccine for MS to induce tolerance in pathogenic myelin-specific T cells. The 3D structure of anti-DEC205 scFv and the remaining part of the vaccine were modeled by ROSIE Antibody server and ITASSER software, respectively. AIDA web server (ab initio domain assembly server) was applied to assemble two parts of the vaccine and build the full construct. Following modeled structure refinement and validation, physicochemical properties, and allergenicity of the vaccine were assessed. In the final step, in silico cloning was done to ensure high-level expression in the desired host. This vaccine consists of three main parts; 1) Anti-DEC205 scFv antibody, 2) multiepitope vaccine part composed of multiple pathogenic CD4+, and CD8+ T cell epitopes originated from multiple known antigens in MS patients, as well as T-regulatory (Treg)-inducing epitopes (Tregitopes), and 3) vasoactive intestinal peptide (VIP). All parts of the final vaccine were joined together with the help of proper linkers. After vaccine construction, the three-D structure, as well as different physicochemical and immunological features of the vaccine were predicted. Finally, in silico gene cloning was also carried out to assure efficient production of protein vaccine in Escherichia coli K12 expression strain. Computational study revealed that this vaccination can regulate MS disease progression and even relapse by harnessing pathogenic T cells.

Effects of biological sex and pregnancy in experimental autoimmune encephalomyelitis: It's complicated.

Experimental autoimmune encephalomyelitis (EAE) can be induced in many animal strains by inoculation with central nervous system antigens and adjuvant or by the passive transfer of lymphocytes reactive with these antigens and is widely used as an animal model for multiple sclerosis (MS). There are reports that female sex and pregnancy affect EAE. Here we review the effects of biological sex and the effects of pregnancy on the clinical features (including disease susceptibility) and pathophysiology of EAE. We also review reports of the possible mechanisms underlying these differences. These include sex-related differences in the immune system and in the central nervous system, the effects of hormones and the sex chromosomes and molecules unique to pregnancy. We also review sex differences in the response to factors that can modify the course of EAE. Our conclusion is that the effects of biological sex in EAE vary amongst animal models and should not be widely extrapolated. In EAE, it is therefore essential that studies looking at the effects of biological sex or pregnancy give full information about the model that is used (i.e. animal strain, sex, the inducing antigen, timing of EAE induction in relation to pregnancy, etc.). In addition, it would be preferable if more than one EAE model were used, to show if any observed effects are generalizable. This is clearly a field that requires further work. However, understanding of the mechanisms of sex differences could lead to greater understanding of EAE, and suggest possible therapies for MS.

Neuroimaging features in inflammatory myelopathies: A review.

Spinal cord involvement can be observed in the course of immune-mediated disorders. Although multiple sclerosis (MS) represents the leading cause of inflammatory myelopathy, an increasing number of alternative etiologies must be now considered in the diagnostic work-up of patients presenting with myelitis. These include antibody-mediated disorders and cytotoxic T cell-mediated diseases targeting central nervous system (CNS) antigens, and systemic autoimmune conditions with secondary CNS involvement. Even though clinical features are helpful to orient the diagnostic suspicion (e.g., timing and severity of myelopathy symptoms), the differential diagnosis of inflammatory myelopathies is often challenging due to overlapping features. Moreover, noninflammatory etiologies can sometimes mimic an inflammatory process. In this setting, magnetic resonance imaging (MRI) is becoming a fundamental tool for the characterization of spinal cord damage, revealing a pictorial scenario which is wider than the clinical manifestations. The characterization of spinal cord lesions in terms of longitudinal extension, location on axial plane, involvement of the white matter and/or gray matter, and specific patterns of contrast enhancement, often allows a proper differentiation of these diseases. For instance, besides classical features, such as the presence of longitudinally extensive spinal cord lesions in patients with aquaporin-4-IgG positive neuromyelitis optica spectrum disorder (AQP4+NMOSD), novel radiological signs (e.g., H sign, trident sign) have been recently proposed and successfully applied for the differential diagnosis of inflammatory myelopathies. In this review article, we will discuss the radiological features of spinal cord involvement in autoimmune disorders such as MS, AQP4+NMOSD, myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), and other recently characterized immune-mediated diseases. The identification of imaging pitfalls and mimics that can lead to misdiagnosis will also be examined. Since spinal cord damage is a major cause of irreversible clinical disability, the recognition of these radiological aspects will help clinicians achieve a correct and prompt diagnosis, treat early with disease-specific treatment and improve patient outcomes.

Autoantibodies against Central Nervous System Antigens and the Serum Levels of IL-32 in Patients with Schizophrenia

Background: Schizophrenia is a disease of the nervous system, and immune system disorders can affect its pathogenesis. Activation of microglia, proinflammatory cytokines, disruption of the blood-brain barrier due to inflammation, activation of autoreactive B cells, and consequently the production of autoantibodies against system antigens are among the immune processes involved in neurological diseases. Interleukin-32 (IL-32) is a proinflammatory cytokine that is essential in activating innate and adaptive immune responses. This study aimed to measure the serum level of IL-32 as well as the frequency of autoantibody positivity against several nervous system antigens in patients with schizophrenia. Material and Methods: This study was conducted on 40 patients with schizophrenia and 40 healthy individuals in the control group. Serum IL-32 levels were measured by ELISA. The frequency of autoantibodies against Hu, Ri, Yo, Tr, CV2, amphiphysin, SOX1, Zic4, ITPR1, CARP, glutamic acid decarboxylase GAD, recoverin, titin, and ganglioside antigens was measured by the indirect immunofluorescence method. Results: Serum IL-32 levels in patients with schizophrenia were significantly higher compared to the control group. The frequency of autoantibodies against GAD and RI antigens in patients with schizophrenia was significantly higher than in the control group. Autoantibodies were positive in 8 patients for GAD antigen and 5 patients for RI antigen. Autoantibodies were also positive in 2 patients for CV2, 1 patient for Hu, and 1 patient for CARP. Negative results were reported for other antigens. Conclusion: Our findings suggest that elevated the serum IL-32 level and autoantibodies against GAD and RI antigens may be a reflection of immune system dysregulation in patients with schizophrenia.

A Study of Autoantibodies against Some Central Nervous System Antigens and the IL-35 Serum Level in Schizophrenia.

Schizophrenia (SCZ) is a debilitating mental disorder with various causes involving complex interactions between genetic factors and environmental agents. The immune system plays a vital role in the pathology and function of the nervous system. Interleukin 35(IL-35) is a regulatory and anti-inflammatory cytokine that can prevent autoimmune and inflammatory diseases. This study aimed to investigate the role of autoantibodies against some central nervous system (CNS) antigens and IL-35 serum levels in patients with Schizophrenia. This case-control study involved 80 participants. The serum levels of IL-35 were measured by enzyme-linked immunosorbent assay and the autoantibodies in the CNS by indirect immunofluorescence assay (IFA). The serum levels of IL-35 were decreased in patient groups compared to healthy subjects. Autoantibodies against N-methyl-D-aspartate receptor (NMDAR) and myelin-associated glycoprotein (MAG) were positive in 15% (6/40) and 7.5% (3/40), respectively; however, no antibodies against myelin, aquaporin-4 (AQP4), myelin oligodendrocyte glycoprotein (MOG),voltage-gated potassium channel (VGKC), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPAR), γ-butyric acid receptor type B1 γ-butyric acid receptor type B1 (GABABR), antidipeptidyl peptidase-like protein-6 (DPPX), immunoglobulin-like cell adhesion molecule 5 (IgLON5), Glycine receptor (R) and acetylcholine receptor (Ach R) were detected (No statistics were computed). We found that decreased serum IL-35 levels and the existence autoantibodies against NMDAR antigen may contribute to the pathogenesis of SCZ.

Humoral immunity at the brain borders in homeostasis.

The meninges encase the brain and spinal cord and house a variety of immune cells, including developing and mature B cells, and antibody-secreting plasma cells. In homeostasis, these cells localize around the dural venous sinuses, providing a defense 'zone' to protect the brain and spinal cord from blood-borne pathogens. Dural plasma cells predominantly secrete IgA antibodies, and some originate from the gastrointestinal tract, with the number and antibody isotype shaped by the gut microbiome. For developing B cells arriving from the adjacent bone marrow, the dura provides a site to tolerize against central nervous system antigens. In this review, we will discuss our current understanding of meningeal humoral immunity in homeostasis.

Serum autoantibodyome reveals that healthy individuals share common autoantibodies

SUMMARYAutoantibodies are a hallmark of both autoimmune disease and cancer, but they also occur in healthy individuals. Here, we perform a meta-analysis of nine datasets and focus on the common autoantibodies shared by healthy individuals. We report 77 common autoantibodies based on the protein microarray data obtained from probing 182 healthy individual sera on 7,653 human proteins and an additional 90 healthy individual sera on 1,666 human proteins. There is no gender bias; however, the number of autoantibodies increase with age, plateauing around adolescence. We use a bioinformatics pipeline to determine possible molecular-mimicry peptides that can contribute to the elicitation of these common autoantibodies. There is enrichment of intrinsic properties of proteins like hydrophilicity, basicity, aromaticity, and flexibility for common autoantigens. Subcellular localization and tissue-expression analysis reveal that several common autoantigens are sequestered from the circulating autoantibodies.

The human anti-ganglioside GM1 autoantibody response following traumatic and surgical central nervous system insults

Predictors of the central nervous system (CNS) directed autoantibody response after acute CNS injury are poorly understood. We analyzed titers of IgG and IgM autoantibodies to ganglioside GM1 in serial serum specimens collected from human patients following acute spinal cord injury (SCI), traumatic brain injury (TBI) and brain tumor resection. We also assessed putative predictors of the autoantibody titers. We enrolled 19 patients with acute SCI, 14 patients with acute severe TBI, and 19 patients undergoing brain tumor resection. We also enrolled 25 control subjects. Some SCI, TBI and tumor patients exhibited elevated IgG titers as compared with control values; some SCI and TBI patients exhibited an acute peak in IgG titers, most commonly 14 days after insult. Some clinical and radiographic measures of injury severity correlated with IgG titer elevation in SCI and TBI patients but not tumor patients. Our study demonstrates that diverse CNS insults are followed by increased IgG autoimmune antibody titers to the CNS antigen ganglioside GM1, however the response inherent to each insult type is unique. IgG autoimmune antibody titers to GM1 merit further study as a biomarker of traumatic injury severity that can be measured in delayed fashion after CNS insult. These human data help to inform which patients with CNS insults are at risk for CNS-directed autoimmunity as well as the time course of the response.

Antibody cross-reactivity between casein and myelin-associated glycoprotein results in central nervous system demyelination

Multiple sclerosis (MS) is a neuroinflammatory demyelinating disease of the central nervous system (CNS) with a high socioeconomic relevance. The pathophysiology of MS, which is both complex and incompletely understood, is believed to be influenced by various environmental determinants, including diet. Since the 1990s, a correlation between the consumption of bovine milk products and MS prevalence has been debated. Here, we show that C57BL/6 mice immunized with bovine casein developed severe spinal cord pathology, in particular, demyelination, which was associated with the deposition of immunoglobulin G. Furthermore, we observed binding of serum from casein-immunized mice to mouse oligodendrocytes in CNS tissue sections and in culture where casein-specific antibodies induced complement-dependent pathology. We subsequently identified myelin-associated glycoprotein (MAG) as a cross-reactive antigenic target. The results obtained from the mouse model were complemented by clinical data showing that serum samples from patients with MS contained significantly higher B cell and antibody reactivity to bovine casein than those from patients with other neurologic diseases. This reactivity correlated with the B cell response to a mixture of CNS antigens and could again be attributed to MAG reactivity. While we acknowledge disease heterogeneity among individuals with MS, we believe that consumption of cow’s milk in a subset of patients with MS who have experienced a previous loss of tolerance to bovine casein may aggravate the disease. Our data suggest that patients with antibodies to bovine casein might benefit from restricting dairy products from their diet.

The role of NK and NKT cells in the pathogenesis and improvement of multiple sclerosis following disease-modifying therapies.

BackgroundMultiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system (CNS) that T cells become autoreactive by recognizing CNS antigens. Both innate and adaptive immune systems are involved in the pathogenesis of MS. In recent years, the impact of innate immune cells on MS pathogenesis has received more attention. CD56bright NK cells, as an immunoregulatory subset of NK cells, can increase the production of cytokines that modulate adaptive immune responses, whereas CD56dim NK cells are more active in cytolysis functions. These two main subsets of NK cells may have different effects on the onset or progression of MS. Invariant NKT (iNKT) cells are other immune cells involved in the control of autoimmune diseases; however, variant NKT (vNKT) cells, despite limited information, could play a role in MS remission via an immunoregulatory pathway.AimWe aimed to evaluate the influence of MS therapeutic agents on NK and NKT cells and NK cell subtypes.Materials and MethodsThe possible mechanism of each MS therapeutic agent has been presented here, focusing on the effects of different disease‐modifying therapies on the number of NK and NKT subtypes.ResultsExpansion of CD56bright NK cells, reduction in the CD56dim cells, and enhancement in NKT cells are the more important innate immune cells alterations following the disease‐modifying therapies.ConclusionExpansion of CD56bright NK cells or reduction in the CD56dim cells has been associated with a successful response to different treatments in MS. iNKT and vNKT cells could have beneficial effects on MS improving. It seems that they are enhanced due to some of MS drugs, leading to disease improvement. However, a reduction in the number of NKT cells could be due to the adverse effects of some of MS drugs on the bone marrow.

The meninges—a cradle and school for nurturing and educating developing B cells

B cell development is thought to be limited to the bone marrow. In this issue of Immunity, Wang etal. find that the meninges, the membranes that surround the brain and spinal cord, contain developing B cells, and they provide evidence that the B cells are there to be tolerized to central nervous system antigens.

DuraBle tolerance to CNS antigens.

B cell development occurs in the meninges of mice and primates, and central nervous system antigen–specific B cells are negatively selected there but not in bone marrow.