Altered cerebrospinal fluid neurofilament light chain but not neurogranin levels are associated with response to ocrelizumab treatment in relapsing remitting multiple sclerosis: a preliminary study.

INTRODUCTION: Ocrelizumab is a CD20-targeting monoclonal antibody used for treatment of multiple sclerosis (MS). Serum and cerebrospinal fluid (CSF) neurofilament light chain (NFL) levels are reduced in MS patients under ocrelizumab treatment indicating a preventive action against neuro-axonal degeneration. Our aim, in this preliminary study, was to explore the impact of ocrelizumab treatment on synaptic integrity through assessment of neurogranin levels. METHODS: Thirteen relapsing-remitting multiple sclerosis (RRMS) patients resistant to first-line immunomodulating agents were enrolled and followed up for 24 months under ocrelizumab treatment. Disease activity was monitored by periodic EDSS, MSSS and cranial-spinal MRI assessments. No evidence of disease (NEDA)-3 activity was determined and CSF levels of NFL (marker of neuro-axonal integrity) and neurogranin (marker of synaptic integrity) were measured by ELISA at baseline and 12-month ocrelizumab treatment. RESULTS: Seven RRMS patients, who preserved NEDA-3 status during 24-month follow-up showed ≥30% NFL level decrease, whereas six patients with stable/increased NFL levels displayed relapse, MRI lesion or disability progression. Although most RRMS patients exhibited increased CSF levels of neurogranin under ocrelizumab treatment, patients with and without neurogranin level increase did not differ in terms of clinical features and NEDA-3 status. Baseline neurogranin levels negatively correlated with baseline EDSS scores. CONCLUSION: Our results confirm that NFL effectively monitors treatment response of RRMS patients under ocrelizumab treatment. Neurogranin does not appear to exhibit a similar benefit in screening of RRMS disease activity. Nevertheless, lower neurogranin levels are associated with increased disability in RRMS indicating a potential disease activity biomarker function.

Patients with restless legs syndrome exhibit reduced serum colony-stimulating factor-1, humanin-like 3 and 10 levels.

OBJECTIVE: The main pathophysiological mechanisms in restless legs syndrome (RLS) are known as genetic predisposition, brain iron deficiency, and dopaminergic dysfunction. While some genetic variants and polymorphisms were defined, the genetic basis and etiopathogenesis of RLS remain unclear. We aimed to identify new candidate genes and/or potential biomarkers associated with increased RLS risk. METHODS: Twenty-three patients with RLS, 30 patients with Parkinson's disease (PD), and 27 healthy controls were enrolled. Agilent Human 8X60K Oligo Microarray was used for the identification of gene expression levels in peripheral blood cells. Gene ontology (GO) analysis was used for functional annotation of differentially expressed genes (DEGs). Serum levels of selected DEGs were measured by ELISA for validation. RESULTS: Patients with RLS showed 30 downregulated DEGs compared to healthy controls. Two genes, MTRNR2L10 and MTRNR2L3, involved negative regulation of the execution phase of apoptosis were highlighted in GO analysis. These genes encode humanin-like 10 and 3, respectively, were encoded by these genes, and their levels, along with CSF-1, linked to neurodegeneration, were reduced in RLS patients. Humanin-like 10 and CSF-1 levels correlated with sleep efficiency and N2 sleep duration, while humanin-like 3 levels correlated with mean sleep oxygen saturation during sleep. CONCLUSION: Our study showed that several neuroprotective genes were downregulated in RLS, which may confer susceptibility to neuronal death associated with decreased sleep efficiency. Microarray results differed between RLS and PD patients, suggesting diverse pathogenetic mechanisms. CSF-1, which is involved in iron, dopamine metabolism, and blood oxygenation, appears to partake in RLS pathophysiology.

Autoimmune Encephalitis with Antibodies Against A-Amino-3hydroxy-5-Methyl-4-Isoxazolepropionic Acid Receptor and γ-Aminobutyric Acid-Beta Receptor: Case Report.

Introduction: Limbic encephalitis is a rapidly progressing disease that presents with seizures, psychiatric symptoms, and recent memory loss. Detection of more than one autoantibody is a rare condition in this disease where an underlying autoantibody is frequently detected. Although different autoantibodies have been reported in the literature, no case has been reported regarding the association of anti-γ-aminobutyric acid-beta-receptor (anti-GABABR) and anti-α-amino-3 hydroxy-5-methyl-4-isoxazolepropionic acid (anti-AMPAR). Case: In this presentation, a 46-year-old female patient with subacute development of short-term memory loss and behavioral symptoms will be described. Anti-GABABR and anti-AMPAR were positive in the anti-neuronal antibody panel sent from the cerebrospinal fluid and serum. Small cell lung cancer was detected as a result of malignancy screening tests. The patient's complaints and autoantibody positivity regressed after immunotherapy. Conclusion: In this case report, a case with coexistence of anti-GABABR and anti-AMPAR antibodies, which has not been previously reported in the literature, is described. As more cases with the coexistence of these two antibodies are detected, knowledge on clinical aspect, laboratory and treatment will increase.

Peripheral blood regulatory B and T cells are decreased in patients with focal epilepsy.

Patients with focal epilepsy of unknown cause (FEoUC) may display T cell infiltration in post-surgery brain specimens and increased serum levels of pro-inflammatory cytokines produced by B and T cells, indicating potential involvement of adaptive immunity. Our study aimed to investigate the peripheral blood distribution of B and T cell subgroups to find clues supporting the distinct organization of adaptive immunity in FEoUC. Twenty-two patients with FEoUC and 25 age and sex matched healthy individuals were included. Peripheral blood mononuclear cells were immunophenotyped by flow cytometry. Expression levels of anti-inflammatory cytokines and FOXP3 were measured by real-time PCR. Carboxyfluorescein succinimidyl ester (CFSE) proliferation assay was conducted using CD4+ T cells. Patients with FEoUC showed significantly decreased regulatory B (Breg), B1a, plasmablast and regulatory T (Treg) cell percentages, and increased switched memory B and Th17 cell ratios. Moreover, CD4+CD25+CD49d- Tregs of FEoUC patients displayed significantly reduced TGFB1 and FOXP3, but increased IL10 gene expression levels. CD4+ helper T cells of patients with FEoUC gave more exaggerated proliferation responses to phytohemagglutinin, anti-CD3 and anti-CD28 stimulation. Patients with FEoUC display increased effector lymphocyte, decreased regulatory lymphocyte ratios, and impaired Treg function and enhanced lymphocyte proliferation capacity. Overall, this pro-inflammatory phenotype lends support to the involvement of adaptive immunity in FEoUC.

Glycine Receptor ß-Targeting Autoantibodies Contribute to the Pathology of Autoimmune Diseases.

BACKGROUND AND OBJECTIVES: Stiff-person syndrome (SPS) and progressive encephalomyelitis with rigidity and myoclonus (PERM) are rare neurologic disorders of the CNS. Until now, exclusive GlyRα subunit-binding autoantibodies with subsequent changes in function and surface numbers were reported. GlyR autoantibodies have also been described in patients with focal epilepsy. Autoimmune reactivity against the GlyRß subunits has not yet been shown. Autoantibodies against GlyRα1 target the large extracellular N-terminal domain. This domain shares a high degree of sequence homology with GlyRß making it not unlikely that GlyRß-specific autoantibody (aAb) exist and contribute to the disease pathology. METHODS: In this study, we investigated serum samples from 58 patients for aAb specifically detecting GlyRß. Studies in microarray format, cell-based assays, and primary spinal cord neurons and spinal cord tissue immunohistochemistry were performed to determine specific GlyRß binding and define aAb binding to distinct protein regions. Preadsorption approaches of aAbs using living cells and the purified extracellular receptor domain were further used. Finally, functional consequences for inhibitory neurotransmission upon GlyRß aAb binding were resolved by whole-cell patch-clamp recordings. RESULTS: Among 58 samples investigated, cell-based assays, tissue analysis, and preadsorption approaches revealed 2 patients with high specificity for GlyRß aAb. Quantitative protein cluster analysis demonstrated aAb binding to synaptic GlyRß colocalized with the scaffold protein gephyrin independent of the presence of GlyRα1. At the functional level, binding of GlyRß aAb from both patients to its target impair glycine efficacy. DISCUSSION: Our study establishes GlyRß as novel target of aAb in patients with SPS/PERM. In contrast to exclusively GlyRα1-positive sera, which alter glycine potency, aAbs against GlyRß impair receptor efficacy for the neurotransmitter glycine. Imaging and functional analyses showed that GlyRß aAbs antagonize inhibitory neurotransmission by affecting receptor function rather than localization.

Electrodiagnostic methods to verify Guillain-Barré syndrome subtypes in Istanbul: A prospective multicenter study.

BACKGROUND AND AIMS: This study aimed to identify the clinical characteristics and electrodiagnostic subtypes of Guillain-Barré syndrome (GBS) in Istanbul. METHODS: Patients with GBS were prospectively recruited between April 2019 and March 2022 and two electrodiagnostic examinations were performed on each patient. The criteria of Ho et al., Hadden et al., Rajabally et al., and Uncini et al. were compared for the differentiation of demyelinating and axonal subtypes, and their relations with anti-ganglioside antibodies were analyzed. RESULTS: One hundred seventy-seven patients were included, 69 before the coronavirus disease 2019 pandemic (April 2019-February 2020) and 108 during the pandemic (March 2020-March 2022), without substantial changes in monthly frequencies. As compared with the criteria of Uncini et al., demyelinating GBS subtype diagnosis was more frequent according to the Ho et al. and Hadden et al. criteria (95/162, 58.6% vs. 110/174, 63.2% and 121/174, 69.5%, respectively), and less frequent according to Rajabally et al.'s criteria (76/174, 43.7%). Fourteen patients' diagnoses made using Rajabally et al.'s criteria were shifted to the other subtype with the second electrodiagnostic examination. Of the 106 analyzed patients, 22 had immunoglobulin G anti-ganglioside antibodies (14 with the axonal subtype). They had less frequent sensory symptoms (54.5% vs. 83.1%, p = 0.009), a more frequent history of previous gastroenteritis (54.5% vs. 22.9%, p = 0.007), and a more severe disease as compared with those without antibodies. INTERPRETATION: Serial electrodiagnostic examinations are more helpful for accurate subtype diagnosis of GBS because of the dynamic pathophysiology of the disease. We observed no significant increase in GBS frequency during the pandemic in this metropolis.

Disease activity in chronic inflammatory demyelinating polyneuropathy: association between circulating B-cell subsets, cytokine levels, and clinical outcomes.

Chronic inflammatory demyelinating polyneuropathy (CIDP), a common and treatable autoimmune neuropathy, is frequently misdiagnosed. The aim of this study is to evaluate the relationship between immunological markers and clinical outcome measures in a mixed cohort of patients with typical CIDP and CIDP variants at different disease stages. Twenty-three typical, 16 multifocal and five distal CIDP patients were included. Twenty-five sex and age-matched healthy controls and 12 patients with Charcot-Marie-Tooth type 1A (CMT1A) disease served as controls. Peripheral B-cell populations were analyzed by flow cytometry. IL6, IL10, TNFA mRNA and mir-21, mir-146a, and mir-155-5p expression levels were evaluated by real-time polymerase chain reaction in peripheral blood mononuclear cells (PBMC) and/or skin biopsy specimens. Results were then assessed for a possible association with clinical disability scores and intraepidermal nerve fiber densities (IENFD) in the distal leg. We detected a significant reduction in naive B cells (P ≤ 0.001), plasma cells (P ≤ 0.001) and regulatory B cells (P < 0.05), and an elevation in switched memory B cells (P ≤ 0.001) in CIDP compared to healthy controls. CMT1A and CIDP patients had comparable B-cell subset distribution. CIDP cases had significantly higher TNFA and IL10 gene expression levels in PBMC compared to healthy controls (P < 0.05 and P ≤ 0.01, respectively). IENFDs in the distal leg showed a moderate negative correlation with switched memory B-cell ratios (r = -0.51, P < 0.05) and a moderate positive correlation with plasma cell ratios (r = 0.46, P < 0.05). INCAT sum scores showed a moderate positive correlation with IL6 gene expression levels in PBMC (r = 0.54, P < 0.05). Altered B-cell homeostasis and IL10 and TNFA gene expression levels imply chronic antigen exposure and overactivity in the humoral immune system, and seem to be a common pathological pathway in both typical CIDP and CIDP variants.

Kelch-like Protein 11 (KLHL11) Antibodies in Children With Seizures of Undetermined Cause.

BACKGROUND/AIM: Kelch-like protein 11 (KLHL11)-antibody may be found in paraneoplastic neurological disorders presenting with epileptic seizures. The aim of this study was to investigate the prevalence and clinical significance of KLHL11-antibody in epilepsy. PATIENTS AND METHODS: Sera of 42 pediatric and 59 adult patients with seizures of undetermined cause were screened using a cell-based assay. RESULTS: KLHL11-antibody was found in three of 168 control patients with paraneoplastic neurological disorders and four pediatric patients (4-8-year-old, 2 boys/2 girls) with seizures of unknown cause presenting with myoclonic-atonic epilepsy, generalized epilepsy or childhood epilepsy with centrotemporal spikes. In these four cases, seizures continued for 2-7 months, responded promptly and favorably to conventional anti-seizure drugs and did not recur in follow-up durations ranging between 2-5 years. Patients had normal brain MRI findings and motor-mental development before and after seizures. KLHL11-antibody was not detected in adult epilepsy patients with undetermined cause, MOG antibody-positive patients and healthy controls. CONCLUSION: KLHL11-antibody may be detected in pediatric epilepsy patients with a relatively benign disease course.

[Cerebellar antibodies in post-stroke sera of acute ischemic stroke patients]. / Kisagyi antitestek akut ischaemiás stroke-on átesett betegek szérumában.

Background and purpose:

Although serum anti-neuronal antibodies are found in acute ischemic stroke (AIS) patients, it is not completely clear whether they are already present before the cerebrovascular event or emerge thereafter. 

Sera of 21 consecutive first-ever AIS patients were collected within the first day of AIS (baseline), as well as 1 and 6 months after AIS. Well-characterized and novel anti-neuronal antibodies were investigated by cell-based assays, immunoblotting and indirect immunohistochemistry.

None of the AIS sera collected at different time points showed well-characterized antibodies. In 7 patients, 1- and 6-month sera (but not baseline sera) showed IgG mostly reacting with soma and dendrites of cerebellar Purkinje cells. Antibody-positive patients did not differ in terms of clinical and etiological features.

Our results provide evidence for the antibody-triggering action of AIS. Although anti-cerebellar antibodies are not associated with the severity of stroke, they may potentially contribute to chronic post-stroke complications and disability.

Antibody induced seizure susceptibility and impaired cognitive performance in a passive transfer rat model of autoimmune encephalitis.

Objective: Autoimmune encephalitis (AE) is a distinct neuro-immunological disorder associated with the production of autoantibodies against neuronal proteins responsible for pharmacoresistant seizures, cognitive decline and behavioral problems. To establish the causal link between leucine-rich glioma inactivated 1 (LGI1) antibody and seizures, we developed an in-vivo antibody-mediated AE rat model in which serum antibodies (IgG) obtained from blood samples of leucine-rich glioma inactivated 1 (LGI1) protein antibody (IgG) positive encephalitis patients were passively transferred into non-epileptic Wistar rats. Serum IgG of N-methyl-d-aspartate receptor (NMDAR) antibody positive patients were used as positive control since the pathogenicity of this antibody has been previously shown in animal models. Methods: Total IgG obtained from the pooled sera of NMDAR and LGI1-IgG positive patients with epileptic seizures and healthy subjects was applied chronically every other day for 11 days into the cerebral lateral ventricle. Spontaneous seizure development was followed by electroencephalography. Behavioral tests for memory and locomotor activity were applied before and after the antibody infusions. Then, pentylenetetrazol (PTZ) was administered intraperitoneally to evaluate seizure susceptibility. Immunohistochemistry processed for assessment of hippocampal astrocyte proliferation and expression intensity of target NMDAR and LGI1 antigens. Results: No spontaneous activity was observed during the antibody infusions. PTZ-induced seizure stage was significantly higher in the NMDAR-IgG and LGI1-IgG groups compared to control. Besides, memory deficits were observed in the NMDAR and LGI1-IgG groups. We observed enhanced astrocyte proliferation in NMDAR- and LGI1-IgG groups and reduced hippocampal NMDAR expression in NMDAR-IgG group. Significance: These findings suggest that neuronal surface auto-antibody administration induces seizure susceptibility and disturbed cognitive performance in the passive transfer rat model of LGI1 AE, which could be a potential in-vivo model for understanding immune-mediated mechanisms underlying epileptogenesis and highlight the potential targets for immune-mediated seizures in AE patients.

Silencing of FCRLB by shRNA ameliorates MuSK-induced EAMG in mice.

INTRODUCTION: Muscle specific kinase (MuSK) antibody positive myasthenia gravis (MG) often presents with a severe disease course and resistance to treatment. Treatment-refractory patients may respond to B cell depleting treatment methods. Our aim was to investigate whether inhibition of Fc receptor-like B (FCRLB) could effectively suppress autoimmunity without diminishing B cell counts in animal model of MG, a classical antibody-mediated autoimmune disease. METHODS: Experimental autoimmune MG was induced in Balb/C mice with two s.c. immunizations with recombinant human MuSK in complete Freund's adjuvant. FCRLB was silenced with a lentiviral particle transported shRNA in myasthenic mice with a single i.p. injection during second MuSK-immunization. Control immunized mice received scrambled shRNA or saline. Mice were observed for clinical parameters for 28 days and at termination, anti-MuSK IgG, neuromuscular junction (NMJ) deposits, muscle AChR expression and lymph node B and T cell ratios were assessed by ELISA, immunofluorescence, immunoblotting and flow cytometry, respectively. RESULTS: FCRLB shRNA-treated mice showed no muscle weakness or weight loss at termination. Also, they exhibited higher grip strength and muscle AChR levels, lower anti-MuSK IgG and NMJ IgG/C3 levels than control mice. Flow cytometry analysis showed that ratios of major effector lymph node B and T cell populations were not altered by FCRLB silencing. However, regulatory T and CD19 + CD5+ B cell ratios were decreased in FCRLB shRNA-group. CONCLUSION: Our results provide evidence regarding involvement and therapeutic value of FCRLB in MuSK-MG. Silencing of FCRLB appears to substantially inhibit antibody production without interfering with survival of major lymphocyte populations.

Potential Role of Antibodies against Aquaporin-1 in Patients with Central Nervous System Demyelination.

Aquaporins (AQPs; AQP0-AQP12) are water channels expressed in many and diverse cell types, participating in various functions of cells, tissues, and systems, including the central nervous system (CNS). AQP dysfunction and autoimmunity to AQPs are implicated in several diseases. The best-known example of autoimmunity against AQPs concerns the antibodies to AQP4 which are involved in the pathogenesis of neuromyelitis optica spectrum disorder (NMOSD), an autoimmune astrocytopathy, causing also CNS demyelination. The present review focuses on the discovery and the potential role of antibodies against AQP1 in the CNS, and their potential involvement in the pathophysiology of NMOSD. We describe (a) the several techniques developed for the detection of the AQP1-antibodies, with emphasis on methods that specifically identify antibodies targeting the extracellular domain of AQP1, i.e., those of potential pathogenic role, and (b) the available evidence supporting the pathogenic relevance of AQP1-antibodies in the NMOSD phenotype.

Chloride intracellular channel protein-1 (CLIC1) antibody in multiple sclerosis patients with predominant optic nerve and spinal cord involvement.

INTRODUCTION: Antibodies to cell surface proteins of astrocytes have been described in chronic inflammatory demyelinating disorders (CIDD) of the central nervous system including multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD). Our aim was to identify novel anti-astrocyte autoantibodies in relapsing remitting MS (RRMS) patients presenting predominantly with spinal cord and optic nerve attacks (MS-SCON). METHODS: Sera of 29 MS-SCON patients and 36 healthy controls were screened with indirect immunofluorescence to identify IgG reacting with human astrocyte cultures. Putative target autoantigens were investigated with immunoprecipitation (IP) and liquid chromatography-mass/mass spectrometry (LC-MS/MS) studies using cultured human astrocytes. Validation of LC-MS/MS results was carried out by IP and ELISA. RESULTS: Antibodies to astrocytic cell surface antigens were detected in 5 MS-SCON patients by immunocytochemistry. LC-MS/MS analysis identified chloride intracellular channel protein-1 (CLIC1) as the single common membrane antigen in 2 patients with MS-SCON. IP experiments performed with the commercial CLIC1 antibody confirmed CLIC1-antibody. Home made ELISA using recombinant CLIC1 protein as the target antigen identified CLIC1 antibodies in 9/29 MS-SCON and 3/15 relapsing inflammatory optic neuritis (RION) patients but in none of the 30 NMOSD patients, 36 RRMS patients with only one or no myelitis/optic neuritis attacks and 36 healthy controls. Patients with CLIC1-antibodies showed trends towards exhibiting reduced disability scores. CONCLUSION: CLIC1-antibody was identified for the first time in MS and RION patients, confirming once again anti-astrocytic autoimmunity in CIDD. CLIC1-antibody may potentially be utilized as a diagnostic biomarker for differentiation of MS from NMOSD.

Increased neuropil antibody prevalence in COVID-19 patients with acute ischemic stroke.

OBJECTIVES: COVID-19 infection is associated with an increased risk of acute ischemic stroke (AIS). Although the underlying mechanisms are largely unknown, autoimmunity has been implicated as a potential role player. METHODS: To investigate the presence and clinical impact of neuronal cell surface antibodies in COVID-19 associated AIS, patients with COVID-19 pneumonia and AIS (n = 30), COVID-19 pneumonia without AIS (n = 32) and AIS without COVID-19 infection (n = 27) were recruited. Serum anti-neuronal antibodies directed against well-characterized and novel cell surface antibodies were evaluated by cell-based assays and indirect immunohistochemistry, respectively. RESULTS: None of the recruited patients displayed well-characterized neuronal cell surface antibodies. Ten patients in the COVID-19 pneumonia with AIS group and three patients in the COVID-19 pneumonia without AIS group exhibited antibodies to neuropil of hippocampus and cerebellum. Neuropil-antibody positive patients showed trends towards milder clinical severity and reduced blood levels of inflammation factors. CONCLUSION: Our results confirm the presence of neuropil antibodies in patients with COVID-19 infection and identify a putative antibody-driven association between AIS and COVID-19. The antigenic targets and potential pathogenic action of these antibodies need to be further explored.

Distribution of peripheral blood mononuclear cell subtypes in patients with West syndrome: Impact of synacthen treatment.

BACKGROUND: West Syndrome (WS) is an epileptic encephalopathy that typically occurs in infants and is characterized by hypsarrhythmia, infantile spasms, and neurodevelopmental impairment. Demonstration of autoantibodies and cytokines in some WS patients and favorable response to immunotherapy have implicated inflammation as a putative trigger of epileptiform activity in WS. Our aim was to provide additional support for altered inflammatory responses in WS through peripheral blood immunophenotype analysis. METHODS: Eight WS cases treated with synacthen and 11 age- and sex-matched healthy volunteers were included. Peripheral blood mononuclear cells (PBMC) were isolated and immunophenotyping was performed in pre-treatment baseline (8 patients) and 3 months post-treatment (6 patients) samples. The analysis included PBMC expressing NFκB transcription and NLRP3 inflammasome factors. RESULTS: In pre-treatment baseline samples, switched memory B cells (CD19+IgD-CD27+) were significantly reduced, whereas plasma cells (CD19+CD38+CD138+) and cytotoxic T cells (CD3+CD8+) were significantly increased. Regulatory T and B cell ratios were not significantly altered. Synacthen treatment only marginally reduced helper T cell ratios and did not significantly change other T, B, NK and NKT cell and monocyte ratios. CONCLUSIONS: Our findings lend further support for the involvement of inflammation-related mechanisms in WS. New-onset WS patients are inclined to display increased plasma cells in the peripheral blood. Synacthen treatment does not show a beneficial effect on most effector acquired and innate immunity subsets.

Serum CXCL5 as a biomarker in multiple sclerosis and neuromyelitis optica spectrum disorder.

OBJECTIVE: Our aim was to determine whether serum C-X-C motif chemokine 5 (CXCL5) may serve as a diagnostic biomarker for relapsing-remitting multiple sclerosis (RRMS) as well as a marker that can be used to predict treatment response. METHODS: CXCL5 levels were measured by ELISA in sera of 20 RRMS patients under fingolimod treatment, 10 neuromyelitis optica spectrum disorder (NMOSD) patients, 15 RRMS patients presenting predominantly with spinal cord and optic nerve attacks (MS-SCON), and 14 healthy controls. RESULTS: Fingolimod treatment significantly reduced CXCL5 levels. CXCL5 levels were comparable among NMOSD and MS-SCON patients. CONCLUSION: Fingolimod might regulate the innate immune system. Serum CXCL5 measurement does not differentiate between RRMS and NMOSD.

Serum IgG of patients with relapsing inflammatory optic neuropathy immunoreacts with Sox2-positive glial cells of the optic nerve.

BACKGROUND: Given the significance of glial cells in maintenance of neurons, antibodies directed against glial cells of the optic nerve might reasonably be expected to have a pathogenic impact in relapsing inflammatory optic neuropathy (RION). METHODS: We investigated IgG immunoreactive with the optic nerve tissue by indirect immunohistochemistry using sera of 20 RION patients. Commercial Sox2-antibody was used for double immunolabeling. RESULTS: Serum IgG of 5 RION patients reacted with cells aligned in the interfascicular regions of the optic nerve. IgG binding sites significantly co-localized with the Sox2-antibody. CONCLUSION: Our results suggest that a subset of RION patients may harbor anti-glial antibodies.

Glycine receptor autoantibody binding to the extracellular domain is independent from receptor glycosylation.

Glycine receptor (GlyR) autoantibodies are associated with stiff-person syndrome and the life-threatening progressive encephalomyelitis with rigidity and myoclonus in children and adults. Patient histories show variability in symptoms and responses to therapeutic treatments. A better understanding of the autoantibody pathology is required to develop improved therapeutic strategies. So far, the underlying molecular pathomechanisms include enhanced receptor internalization and direct receptor blocking altering GlyR function. A common epitope of autoantibodies against the GlyRα1 has been previously defined to residues 1A-33G at the N-terminus of the mature GlyR extracellular domain. However, if other autoantibody binding sites exist or additional GlyR residues are involved in autoantibody binding is yet unknown. The present study investigates the importance of receptor glycosylation for binding of anti-GlyR autoantibodies. The glycine receptor α1 harbors only one glycosylation site at the amino acid residue asparagine 38 localized in close vicinity to the identified common autoantibody epitope. First, non-glycosylated GlyRs were characterized using protein biochemical approaches as well as electrophysiological recordings and molecular modeling. Molecular modeling of non-glycosylated GlyRα1 did not show major structural alterations. Moreover, non-glycosylation of the GlyRα1N38Q did not prevent the receptor from surface expression. At the functional level, the non-glycosylated GlyR demonstrated reduced glycine potency, but patient GlyR autoantibodies still bound to the surface-expressed non-glycosylated receptor protein in living cells. Efficient adsorption of GlyR autoantibodies from patient samples was possible by binding to native glycosylated and non-glycosylated GlyRα1 expressed in living not fixed transfected HEK293 cells. Binding of patient-derived GlyR autoantibodies to the non-glycosylated GlyRα1 offered the possibility to use purified non-glycosylated GlyR extracellular domain constructs coated on ELISA plates and use them as a fast screening readout for the presence of GlyR autoantibodies in patient serum samples. Following successful adsorption of patient autoantibodies by GlyR ECDs, binding to primary motoneurons and transfected cells was absent. Our results indicate that the glycine receptor autoantibody binding is independent of the receptor's glycosylation state. Purified non-glycosylated receptor domains harbouring the autoantibody epitope thus provide, an additional reliable experimental tool besides binding to native receptors in cell-based assays for detection of autoantibody presence in patient sera.