Targeting B cells to modify MS, NMOSD, and MOGAD: Part 2

Case report: paraneoplastic cerebellar degeneration associated with anti-Yo antibody successfully treated with ofatumumab

Paraneoplastic cerebellar degeneration (PCD) with anti-Yo antibodies represents a rare immune-mediated paraneoplastic neurological syndrome. Its diagnosis and management remain clinically challenging. Here, we present a case of PCD with confirmed anti-Yo antibodies, validated through anti-cerebellar degeneration protein 2 (CDR2) and anti-CDR2-like antibodies detection, which demonstrated a favorable response to ofatumumab therapy. The patient initially manifested with dizziness, nystagmus, dysarthria, and ataxia. Initial testing revealed weakly positive anti-Yo antibodies, accompanied by positive serum tissue-based assay result for cerebellum. Following one course of intravenous immunoglobulin and methylprednisolone pulse therapy, improvement of the patient's dizziness was observed. Oral prednisone was prescribed for maintenance therapy. However, after discharge, the patient experienced progressive deterioration of symptoms, including worsening dizziness, dysarthria, and limb ataxia. Upon readmission to our hospital, further immunological testing confirmed the presence of anti-CDR2 and anti-CDR2-like antibodies. When a second course of methylprednisolone pulse therapy proved ineffective, treatment was switched to ofatumumab. After two doses, the patient achieved partial symptomatic relief.

HLA-transgenic mouse models to study autoimmune central nervous system diseases

It is known that certain human leukocyte antigen (HLA) genes are associated with autoimmune central nervous system (CNS) diseases, such as multiple sclerosis (MS), but their exact role in disease susceptibility and etiopathogenesis remains unclear. The best studied HLA-associated autoimmune CNS disease is MS, and thus will be the primary focus of this review. Other HLA-associated autoimmune CNS diseases, such as autoimmune encephalitis and neuromyelitis optica will be discussed. The lack of animal models to accurately capture the complex human autoimmune response remains a major challenge. HLA transgenic (tg) mice provide researchers with powerful tools to investigate the underlying mechanisms promoting susceptibility and progression of HLA-associated autoimmune CNS diseases, as well as for elucidating the myelin epitopes potentially targeted by T cells in autoimmune disease patients. We will discuss the potential role(s) of autoimmune disease-associated HLA alleles in autoimmune CNS diseases and highlight information provided by studies using HLA tg mice to investigate the underlying pathological mechanisms and opportunities to use these models for development of novel therapies.

The real-world applicability of the 2023 international myelin oligodendrocyte glycoprotein antibody-associated disease criteria in a Latin American cohort

BACKGROUND AND PURPOSE

The diagnostic criteria for myelin oligodendrocyte glycoprotein antibody (MOG-IgG)-associated disease (MOGAD) were published in 2023. We aimed to determine the performance of the new criteria in Latin American (LATAM) patients compared with the 2018 criteria and explore the significance of MOG-IgG titers in diagnosis.

METHODS

We retrospectively reviewed the medical records of LATAM (Argentina, Chile, Brazil, Peru, Ecuador, and Colombia) adult patients with one clinical MOGAD event and MOG-IgG positivity confirmed by cell-based assay. Both 2018 and 2023 MOGAD criteria were applied, calculating diagnostic performance indicators.

RESULTS

Among 171 patients (predominantly females, mean age at first attack = 34.1 years, mean disease duration = 4.5 years), 98.2% patients met the 2018 criteria, and of those who did not fulfill diagnostic criteria (n = 3), all tested positive for MOG-IgG (one low-positive and two without reported titer). Additionally, 144 (84.2%) patients met the 2023 criteria, of whom 57 (39.5%) had MOG-IgG+ titer information (19 clearly positive and 38 low-positive), whereas 87 (60.5%) patients had no MOG-IgG titer. All 144 patients met diagnostic supporting criteria. The remaining 27 patients did not meet the 2023 MOGAD criteria due to low MOG-IgG (n = 12) or lack of titer antibody access (n = 15), associated with the absence of supporting criteria. The 2023 MOGAD criteria showed a sensitivity of 86% (95% confidence interval = 0.80-0.91) and specificity of 100% compared to the 2018 criteria.

CONCLUSIONS

These findings support the diagnostic utility of the 2023 MOGAD criteria in an LATAM cohort in real-world practice, despite limited access to MOG-IgG titration.

Global perspectives on the contribution of B cells to multiple sclerosis: an in-depth examination and evaluation

Background

Multiple sclerosis (MS) is a chronic, progressive autoimmune disease, with increasing attention on the role of B cells in its pathogenesis. Despite this growing interest, a comprehensive analysis of research trends and emerging foci on B cells in MS is currently lacking. In this research, we utilize a bibliometric approach to visualize and analyze research trends and focal points in this field, offering a valuable reference for future mechanistic studies in MS.

Methods

We retrieved bibliometric data from the Web of Science Core Collection (WOSCC) for articles published between 2014 and 2023. VOSviewer 1.6.18 and CiteSpace 5.7R3 were used for co-authorship, co-occurrence, and citation analyses to identify key researchers, institutions, countries, and emerging themes in B cell research related to MS.

Results

The analysis examined 5,578 articles published in 1,041 journals by 5,337 institutions globally. The United States leads in publication output, with Amit Bar-Or identified as the most influential author, and Frontiers in Immunology as the top journal in the field. Research has increasingly focused on the complex role of B cells in MS, particularly their involvement in the central nervous system (CNS) and mechanisms of anti-B cell therapy. Recent trends point to a growing focus on meningeal inflammation, kinase inhibitors, and Epstein-Barr virus, signaling a shift in research priorities.

Conclusion

This bibliometric analysis highlights pivotal research trends, key contributors, and emerging areas of interest in B cell research in MS from 2013 to 2024. The findings underscore the growing recognition of the multifaceted role of B cells in MS pathogenesis, particularly their involvement in the CNS compartment and the potential of targeted therapies. The study identifies meningeal inflammation, Epstein-Barr virus infection, and kinase inhibitors as promising avenues for future research. The analyses driving the in-depth exploration of B cell mechanisms in MS and the development of novel diagnostic and therapeutic strategies provide researchers in the MS field with a comprehensive and objective perspective, serving as a valuable reference for accelerating the translation of basic research findings into clinical applications.

Case report: Identification of Hepatitis B Virus in the cerebrospinal fluid of neuromyelitis optica spectrum disorders and successful treatment with ofatumumab and inebilizumab

Neuromyelitis optica spectrum disorder (NMOSD) is a rare demyelinating disease of the central nervous system primarily affecting the optic nerves, spinal cord, and brainstem. Viral infection may trigger NMOSD. Here, we report the case of a 34-year-old female presenting with a range of symptoms including nausea, vomiting, dysphagia, choking, and fatigue with unsteady gait, diplopia, hearing loss, left-sided facial paralysis, breathing difficulties, and hoarseness of voice. Her HBV DNA concentration, as determined by quantitative PCR analysis, exceeded 5×107 IU/ml in serum and 4.48×102 IU/ml in CSF. Next-generation sequencing of CSF revealed 1,528 HBV sequences in DNA analysis and 6 sequences in RNA analysis. Serum aquaporin-4 antibody (AQP4-Ab) titer was 1:10, and the CSF titer was 1:3.2. Brain magnetic resonance imaging showed high signal intensities in the brain stem, medulla oblongata, and left middle cerebellar peduncle with mild restricted-diffusion. The patient received antiviral and hepatoprotective medications before the high-dose methylprednisolone pulse therapy. However, the patient did not respond well to the first-line treatment. Subsequently, the patient received ofatumumab and inebilizumab. Throughout the follow-up period, there was a gradual improvement in her neurological symptoms, with no reactivation of hepatitis B or deterioration of liver function observed. Thereby, to the best of our knowledge, we report the first case of successful treatment with ofatumumab and inebilizumab in a patient with NMOSD concurrent with HBV infection.

Monoclonal antibody therapies for aquaporin-4-immunoglobulin G-positive neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein antibody-associated disease

Monoclonal antibody therapies mark the new era of targeted treatment for relapse prevention in aquaporin-4 (AQP4)-immunoglobulin G (IgG)-positive neuromyelitis optica spectrum disorder (AQP4-IgG+NMOSD). For over a decade, rituximab, an anti-CD20 B-cell-depleting agent, had been the most effectiveness treatment for AQP4-IgG+NMOSD. Tocilizumab, an anti-interleukin-6 receptor, was also observed to be effective. In 2019, several randomized, placebo-controlled trials were completed that demonstrated the remarkable efficacy of eculizumab (anti-C5 complement inhibitor), inebilizumab (anti-CD19 B-cell-depleting agent), and satralizumab (anti-interleukin-6 receptor), leading to the Food and Drug Administration (FDA) approval of specific treatments for AQP4-IgG+NMOSD for the first time. Most recently, ravulizumab (anti-C5 complement inhibitor) was also shown to be highly efficacious in an open-label, external-controlled trial. Although only some patients with myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) warrant immunotherapy, there is currently no FDA-approved treatment for relapse prevention in MOGAD. Observational studies showed that tocilizumab was associated with a decrease in relapses, whereas rituximab seemed to have less robust effectiveness in MOGAD compared to AQP4-IgG+NMOSD. Herein, we review the evidence on the efficacy and safety of each monoclonal antibody therapy used in AQP4-IgG+NMOSD and MOGAD, including special considerations in children and women of childbearing potential.

Neuromyelitis Optica Spectrum Disorders: Clinical Perspectives, Molecular Mechanisms, and Treatments

Neuromyelitis optica (NMO) is a rare autoimmune inflammatory disorder affecting the central nervous system (CNS), specifically the optic nerve and the spinal cord, with severe clinical manifestations, including optic neuritis (ON) and transverse myelitis. Initially, NMO was wrongly understood as a condition related to multiple sclerosis (MS), due to a few similar clinical and radiological features, until the discovery of the AQP4 antibody (NMO-IgG/AQP4-ab). Various etiological factors, such as genetic-environmental factors, medication, low levels of vitamins, and others, contribute to the initiation of NMO pathogenesis. The autoantibodies against AQP4 target the AQP4 channel at the blood–brain barrier (BBB) of the astrocyte end feet, which leads to high permeability or leakage of the BBB that causes more influx of AQP4-antibodies into the cerebrospinal fluid (CSF) of NMO patients. The binding of AQP4-IgG onto the AQP4 extracellular epitopes initiates astrocyte damage through complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC). Thus, a membrane attack complex is formed due to complement cascade activation; the membrane attack complex targets the AQP4 channels in the astrocytes, leading to astrocyte cell damage, demyelination of neurons and oligodendrocytes, and neuroinflammation. The treatment of NMOSD could improve relapse symptoms, restore neurological functions, and alleviate immunosuppression. Corticosteroids, apheresis therapies, immunosuppressive drugs, and B cell inactivating and complement cascade blocking agents have been used to treat NMOSD. This review intends to provide all possible recent studies related to molecular mechanisms, clinical perspectives, and treatment methodologies of the disease, particularly focusing on recent developments in clinical criteria and therapeutic formulations.

B cell targeted therapies in inflammatory autoimmune disease of the central nervous system

Cumulative evidence along several lines indicates that B cells play an important role in the pathological course of multiple sclerosis (MS), neuromyelitisoptica spectrum disorders (NMOSD) and related CNS diseases. This has prompted extensive research in exploring the utility of targeting B cells to contain disease activity in these disorders. In this review, we first recapitulate the development of B cells from their origin in the bone marrow to their migration to the periphery, including the expression of therapy-relevant surface immunoglobulin isotypes. Not only the ability of B cells to produce cytokines and immunoglobulins seems to be essential in driving neuroinflammation, but also their regulatory functions strongly impact pathobiology. We then critically assess studies of B cell depleting therapies, including CD20 and CD19 targeting monoclonal antibodies, as well as the new class of B cell modulating substances, Bruton´s tyrosinekinase (BTK) inhibitors, in MS, NMOSD and MOGAD.

The Potential Pathogenicity of Myelin Oligodendrocyte Glycoprotein Antibodies in the Optic Pathway

BACKGROUND

Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) is an acquired inflammatory demyelinating disease with optic neuritis (ON) as the most frequent clinical symptom. The hallmark of the disease is the presence of autoantibodies against MOG (MOG-IgG) in the serum of patients. Whereas the role of MOG in the experimental autoimmune encephalomyelitis animal model is well-established, the pathogenesis of the human disease and the role of human MOG-IgG is still not fully clear.

EVIDENCE ACQUISITION

PubMed was searched for the terms "MOGAD," "optic neuritis," "MOG antibodies," and "experimental autoimmune encephalomyelitis" alone or in combination, to find articles of interest for this review. Only articles written in English language were included and reference lists were searched for further relevant papers.

RESULTS

B and T cells play a role in the pathogenesis of human MOGAD. The distribution of lesions and their development toward the optic pathway is influenced by the genetic background in animal models. Moreover, MOGAD-associated ON is frequently bilateral and often relapsing with generally favorable visual outcome. Activated T-cell subsets create an inflammatory environment and B cells are necessary to produce autoantibodies directed against the MOG protein. Here, pathologic mechanisms of MOG-IgG are discussed, and histopathologic findings are presented.

CONCLUSIONS

MOGAD patients often present with ON and harbor antibodies against MOG. Furthermore, pathogenesis is most likely a synergy between encephalitogenic T and antibody producing B cells. However, to which extent MOG-IgG are pathogenic and the exact pathologic mechanism is still not well understood.

Anti-BCMA CAR T-cell therapy CT103A in relapsed or refractory AQP4-IgG seropositive neuromyelitis optica spectrum disorders: phase 1 trial interim results

Chimeric antigen receptor (CAR) T-cell therapy that targets B-cell maturation antigen (BCMA) have great potentials in autoimmune diseases and could be novel therapeutics for relapsed/refractory neuromyelitis optica spectrum disorder (NMOSD). To evaluate the safety and efficacy of the CT103A, a self-developed BCMA-targeting CAR construct against BCMA, in patients with AQP4-IgG seropositive NMOSD, an ongoing, investigator-initiated, open-label, single-arm, phase 1 clinical trial is conducted at our center. In total, 12 patients were administered with a CAR-BCMA infusion. Ten of the 12 patients dosed were women (83.3%), with a median age of 49.5 years (range, 30-67). were The most common events of grade 3 or higher were hematologic toxic effects. Seven patients (58%) developed infections, but no grade 4 infections occurred. Cytokine release syndrome was reported in all patients with only events of grade 1 or 2 observed. During the follow-up of a median 5.5 months, 11 patients had no relapse; all patients generally reported improvement in disabilities and quality-of-life outcomes; 11 patients' AQP-4 antibodies in serum showed a downward trend by the cutoff date. CAR T-cell expansion was associated with responses, and persisted more than 6 months post-infusion in 17% of the patients. In summary, CAR T-cell therapy shows a manageable safety profile and therapeutic potentials for patients with relapsed/refractory AQP4-IgG seropositive NMOSD. Another expansion phase is currently underway to determine the safety and efficacy of CAR T-BCMA infusion in patients with other neuro-inflammatory diseases.

Intravenous ofatumumab treatment of multiple sclerosis and related disorders: An observational study

BACKGROUND

Ofatumumab is an anti-CD20 monoclonal antibody approved for subcutaneous administration for the treatment of relapsing multiple sclerosis (MS), but intravenously administered ofatumumab has been investigated in a phase 2 trial and used off-label. The objective of the present study was to assess disease activity and side effects in relation to longer-term intravenous ofatumumab treatment of MS and related disorders.

METHODS

We conducted a retrospective study of patients treated off-label with intravenous ofatumumab for MS, neuromyelitis optica spectrum disease (NMOSD) and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) at the Danish Multiple Sclerosis Center. Data was retrieved from the Danish Multiple Sclerosis Registry and through medical chart review.

RESULTS

Fifty patients were identified with a median treatment duration of 2.2 years. Annualized relapse rate decreased from 1.03 at baseline to 0.38 during ofatumumab treatment. At 24 months, the probability of having experienced a relapse was 55% and confirmed disability worsening 7%. Frequency of infusion-related reactions was 86% during the first infusion and 42% during the last infusion. Six experienced infections requiring hospitalization.

CONCLUSION

Our data indicate a reduction of relapse frequency, stabilization of disability worsening and an acceptable safety profile, although we observed a higher frequency of infusion reactions compared to data from other intravenously administered anti-CD20 monoclonal antibodies. The study supports a class effect of anti-CD20 monoclonal antibodies and the hypothesis that complement activation may be associated to a higher frequency of infusion related reactions.

Targeting B cell dysregulation with emerging therapies in autoimmune demyelinating disorders

The depletion of B cells has proven to be beneficial in the treatment of autoimmune demyelinating disorders. The high efficacy of these therapies has highlighted the importance of B cells in autoimmunity and prompted investigations into specific B cell subsets that may be aberrant. Recently, a rise in the trialling of alternative B cell-targeting therapies that inhibit targets such as Bruton's tyrosine kinase, interleukin-6 receptor and fragment crystallisable neonatal receptor has also been observed. These agents interfere with specific dysregulated functions of B cells in contrast to the broad removal of many B cell subsets with depletion agents. The therapeutic benefit of these emerging agents will help delineate the contributions of B cells in demyelinating disorders and holds great potential for future treatment.

Progress in treatment of neuromyelitis optica spectrum disorders (NMOSD): Novel insights into therapeutic possibilities in NMOSD

Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune inflammatory demyelinating disorder of the central nervous system (CNS), which is a severely disabling disorder leading to devastating sequelae or even death. Repeated acute attacks and the presence of aquaporin-4 immunoglobulin G (AQP4-IgG) antibody are the typical characteristics of NMOSD. Recently, the phase III trials of the newly developed biologicals therapies have shown their effectiveness and good tolerance to a certain extent when compared with the traditional therapy with the first- and second-line drugs. However, there is still a lack of large sample, double-blind, randomized, clinical studies to confirm their efficacy, safety, and tolerability. Especially, these drugs have no clear effect on NMOSD patients without AQP4-IgG and refractory patients. Therefore, it is of strong demand to further conduct large sample, double-blind, randomized, clinical trials, and novel therapeutic possibilities in NMOSD are discussed briefly here.

Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease (MOGAD): A Review of Clinical and MRI Features, Diagnosis, and Management

Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) is the most recently defined inflammatory demyelinating disease of the central nervous system (CNS). Over the last decade, several studies have helped delineate the characteristic clinical-MRI phenotypes of the disease, allowing distinction from aquaporin-4 (AQP4)-IgG-positive neuromyelitis optica spectrum disorder (AQP4-IgG+NMOSD) and multiple sclerosis (MS). The clinical manifestations of MOGAD are heterogeneous, ranging from isolated optic neuritis or myelitis to multifocal CNS demyelination often in the form of acute disseminated encephalomyelitis (ADEM), or cortical encephalitis. A relapsing course is observed in approximately 50% of patients. Characteristic MRI features have been described that increase the diagnostic suspicion (e.g., perineural optic nerve enhancement, spinal cord H-sign, T2-lesion resolution over time) and help discriminate from MS and AQP4+NMOSD, despite some overlap. The detection of MOG-IgG in the serum (and sometimes CSF) confirms the diagnosis in patients with compatible clinical-MRI phenotypes, but false positive results are occasionally encountered, especially with indiscriminate testing of large unselected populations. The type of cell-based assay used to evaluate for MOG-IgG (fixed vs. live) and antibody end-titer (low vs. high) can influence the likelihood of MOGAD diagnosis. International consensus diagnostic criteria for MOGAD are currently being compiled and will assist in clinical diagnosis and be useful for enrolment in clinical trials. Although randomized controlled trials are lacking, MOGAD acute attacks appear to be very responsive to high dose steroids and plasma exchange may be considered in refractory cases. Attack-prevention treatments also lack class-I data and empiric maintenance treatment is generally reserved for relapsing cases or patients with severe residual disability after the presenting attack. A variety of empiric steroid-sparing immunosuppressants can be considered and may be efficacious based on retrospective or prospective observational studies but prospective randomized placebo-controlled trials are needed to better guide treatment. In summary, this article will review our rapidly evolving understanding of MOGAD diagnosis and management.

Failure of alemtuzumab therapy in three patients with MOG antibody associated disease

BACKGROUND

Myelin Oligodendrocyte Glycoprotein antibody-associated disease (MOGAD) is most classically associated in both children and adults with phenotypes including bilateral and recurrent optic neuritis (ON) and transverse myelitis (TM), with the absence of brain lesions characteristic of multiple sclerosis (MS). ADEM phenotype is the most common presentation of MOGAD in children. However, the presence of clinical phenotypes including unilateral ON and short TM in some patients with MOGAD may lead to their misdiagnosis as MS. Thus, clinically and radiologically, MOGAD can mimic MS and clinical vigilance is required for accurate diagnostic workup.

CASE PRESENTATION

We present three cases initially diagnosed as MS and then treated with alemtuzumab. Unexpectedly, all three patients did quite poorly on this medication, with a decline in their clinical status with worsening of expanded disability status scale (EDSS) and an increasing lesion load on magnetic resonance imaging of the brain. Subsequently, all three cases were found to have anti-MOG antibody in their serum.

CONCLUSIONS

These cases highlight that if a patient suspected to have MS does not respond to conventional treatments such as alemtuzumab, a search for alternative diagnoses such as MOG antibody disease may be warranted.

The risk of infections for multiple sclerosis and neuromyelitis optica spectrum disorder disease-modifying treatments: Eighth European Committee for Treatment and Research in Multiple Sclerosis Focused Workshop Review. April 2021

Over the recent years, the treatment of multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) has evolved very rapidly and a large number of disease-modifying treatments (DMTs) are now available. However, most DMTs are associated with adverse events, the most frequent of which being infections. Consideration of all DMT-associated risks facilitates development of risk mitigation strategies. An international focused workshop with expert-led discussions was sponsored by the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) and was held in April 2021 to review our current knowledge about the risk of infections associated with the use of DMTs for people with MS and NMOSD and corresponding risk mitigation strategies. The workshop addressed DMT-associated infections in specific populations, such as children and pregnant women with MS, or people with MS who have other comorbidities or live in regions with an exceptionally high infection burden. Finally, we reviewed the topic of DMT-associated infectious risks in the context of the current SARS-CoV-2 pandemic. Herein, we summarize available evidence and identify gaps in knowledge which justify further research.

Cerebrospinal fluid biomarkers and cognitive functions at multiple sclerosis diagnosis

Cognitive impairment (CI) is a frequent and disabling symptom in Multiple Sclerosis (MS). Axonal damage may contribute to CI development from early stages. Nevertheless, no biomarkers are at the moment available to track CI in MS patients. We aimed to explore the correlation of cerebrospinal fluid (CSF) axonal biomarkers, in particular: light-chain neurofilaments (NFL), Tau, and Beta-amyloid protein (Abeta) in MS patients with CI at the diagnosis. 62 newly diagnosed MS patients were enrolled, and cognition was evaluated using the Brief International Cognitive Assessment for MS (BICAMS) battery. CSF NFL, Abeta, and Tau levels were determined with commercial ELISA. Patients with CI (45.1%) did not differ for demographic, clinical, and MRI characteristics (except for lower educational level), but they displayed greater neurodegeneration, exhibiting higher mean CSF Tau protein (162.1 ± 52.96 pg/ml versus 132.2 ± 63.86 pg/ml p:0.03). No differences were observed for Abeta and NFL. The number of impaired tests and Tau were significantly correlated (r:0.32 p:0.01). Tau was higher in particular in patients with slowed information processing speed (IPS) (p:0.006) and a linear regression analysis accounting for EDSS, MRI, and MS subtype confirmed Tau as a weak predictor of IPS and cognitive impairment. In conclusion, CI has an important burden on the quality of life of MS patients and should be looked for even at diagnosis. Axonal damage biomarkers, and in particular Tau, seem to reflect cognition impairment in the early stages.

What's new in neuromyelitis optica spectrum disorder treatment?

Optic neuritis, an optic nerve inflammatory disease presenting with acute unilateral or bilateral visual loss, is one of the core symptoms of neuromyelitis optica spectrum disorder (NMOSD). The diagnosis of NMOSD-related optic neuritis is challenging, and it is mainly based on clinical presentation, optical coherence tomography, magnetic resonance imaging scans, and the status of serum aquaporin-4 antibodies. In the pathogenesis, aquaporin-4 antibodies target astrocytes in the optic nerves, spinal cord and some specific regions of the brain eliciting a devastating autoimmune response. Current pharmacological interventions are directed against various steps within the immunological response, notably the terminal complement system, B-cells, and the pro-inflammatory cytokine Interleukin 6 (IL6). Conventional maintenance therapies were off-label uses of the unspecific immunosuppressants azathioprine and mycophenolate mofetil as well as the CD20 specific antibody rituximab and the IL6 receptor specific antibody tocilizumab. Recently, four phase III clinical trials demonstrated the safety and efficacy of the three novel biologics eculizumab, inebilizumab, and satralizumab. These monoclonal antibodies are directed against the complement system, CD19 B-cells and the IL6 receptor, respectively. All three have been approved for NMOSD in the US and several other countries worldwide and thus provide convincing treatment options.

Secondary Immunodeficiency and Risk of Infection Following Immune Therapies in Neurology

Secondary immunodeficiencies (SIDs) are acquired conditions that may occur as sequelae of immune therapy. In recent years a number of disease-modifying therapies (DMTs) has been approved for multiple sclerosis and related disorders such as neuromyelitis optica spectrum disorders, some of which are frequently also used in- or off-label to treat conditions such as chronic inflammatory demyelinating polyneuropathy (CIDP), myasthenia gravis, myositis, and encephalitis. In this review, we focus on currently available immune therapeutics in neurology to explore their specific modes of action that might contribute to SID, with particular emphasis on their potential to induce secondary antibody deficiency. Considering evidence from clinical trials as well as long-term observational studies related to the patients' immune status and risks of severe infections, we delineate long-term anti-CD20 therapy, with the greatest data availability for rituximab, as a major risk factor for the development of SID, particularly through secondary antibody deficiency. Alemtuzumab and cladribine have relevant effects on circulating B-cell counts; however, evidence for SID mediated by antibody deficiency appears limited and urgently warrants further systematic evaluation. To date, there has been no evidence suggesting that treatment with fingolimod, dimethyl fumarate, or natalizumab leads to antibody deficiency. Risk factors predisposing to development of SID include duration of therapy, increasing age, and pre-existing low immunoglobulin (Ig) levels. Prevention strategies of SID comprise awareness of risk factors, individualized treatment protocols, and vaccination concepts. Immune supplementation employing Ig replacement therapy might reduce morbidity and mortality associated with SIDs in neurological conditions. In light of the broad range of existing and emerging therapies, the potential for SID warrants urgent consideration among neurologists and other healthcare professionals.

Neuromyelitis optica spectrum disorders: from pathophysiology to therapeutic strategies

Neuromyelitis optica (NMO) is a chronic inflammatory autoimmune disease of the central nervous system (CNS) characterized by acute optic neuritis (ON) and transverse myelitis (TM). NMO is caused by a pathogenic serum IgG antibody against the water channel aquoporin 4 (AQP4) in the majority of patients. AQP4-antibody (AQP4-ab) presence is highly specific, and differentiates NMO from multiple sclerosis. It binds to AQP4 channels on astrocytes, triggering activation of the classical complement cascade, causing granulocyte, eosinophil, and lymphocyte infiltration, culminating in injury first to astrocyte, then oligodendrocytes followed by demyelination and neuronal loss. NMO spectrum disorder (NMOSD) has recently been defined and stratified based on AQP4-ab serology status. Most NMOSD patients experience severe relapses leading to permanent neurologic disability, making suppression of relapse frequency and severity, the primary objective in disease management. The most common treatments used for relapses are steroids and plasma exchange.Currently, long-term NMOSD relapse prevention includes off-label use of immunosuppressants, particularly rituximab. In the last 2 years however, three pivotal clinical trials have expanded the spectrum of drugs available for NMOSD patients. Phase III studies have shown significant relapse reduction compared to placebo in AQP4-ab-positive patients treated with satralizumab, an interleukin-6 receptor (IL-6R) inhibitor, inebilizumab, an antibody against CD19⁺ B cells; and eculizumab, an antibody blocking the C5 component of complement. In light of the new evidence on NMOSD pathophysiology and of preliminary results from ongoing trials with new drugs, we present this descriptive review, highlighting promising treatment modalities as well as auspicious preclinical and clinical studies.

Cladribine suppresses disease activity in neuromyelitis optica spectrum disorder: a 2-year follow-up study

BACKGROUND AND PURPOSE

Neuromyelitis optica spectrum disorder (NMOSD) is a difficult condition to treat. Cladribine selectively and transiently depletes B and T lymphocytes, leading to long-lasting immune reconstitution. This report describes observations from 24 months of follow-up after cladribine in NMOSD patients.

METHODS

This is a retrospective analysis of a case series including 12 seropositive patients with NMOSD. Patients were given cladribine by subcutaneous injections in a series of several 2-day cycles of 20 mg administered at intervals of 4-6 weeks. Thus, the full treatment course delivered a cumulative bioavailable dose similar to that approved for treatment of multiple sclerosis. Annualized relapse rate (ARR), disability (Expanded Disability Status Scale [EDSS] score) and safety in the 24 months preceding and the 24 months following the initiation of cladribine treatment were assessed.

RESULTS

The mean ARR in the 24 months preceding cladribine treatment was 1.04 (95% confidence interval [CI] 0.67-1.62). The mean ARR in the 24 months following initiation of cladribine treatment was 0.21 (95% CI 0.08-0.56). The ratio in the rate of events post versus prior cladribine initiation was 0.20 (95% CI 0.07-0.59) and highly significant (p = 0.0073). The EDSS score did not change over the follow-up period (2.5 ± 1.7; mean ± SD) compared to baseline (2.5 ± 1.5; mean ± SD). No serious adverse events considered to be linked to cladribine were observed during follow-up.

CONCLUSIONS

Cladribine was safe in NMOSD patients over a 2-year observation period. Cladribine treatment was associated with clinical stabilization, as evidenced by significantly decreased ARR and no progression of EDSS score.

The Impact of COVID-19 on Patients With Neuromyelitis Optica Spectrum Disorder Beyond Infection Risk

There is an increasing need for better understanding of the impact of coronavirus disease 2019 (COVID-19) on patients with neuromyelitis optica spectrum disorder (NMOSD). A few pilot studies have investigated COVID-19 infections in NMOSD, but few studies have addressed disease activity and immune status of these patients during the pandemic. We carried out a cross-sectional study to examine immune status, relapses, and COVID-19 infections in a cohort of NMOSD patients using an electronic patient registry (MSNMOBase) for multiple sclerosis and related disorders. An online questionnaire was administered to all NMOSD patients in the registry from January 1, 2011, to June 1, 2020. Clinical demographic characteristics, immune status, relapses, treatments, COVID-19 infections, and preventive measures were evaluated. Of the 752 registered patients, 535 (71.1%) with qualified data were included. A total of 486 used preventive therapies during the pandemic, including mycophenolate mofetil (71.2%), azathioprine (13.3%), and other immunosuppressants (6.4%). Neither median immune cell counts nor immunoglobulin levels (p > 0.05) were significantly different between patients with or without immunosuppression. During the pandemic, no patients were diagnosed with COVID-19, and the majority (>95%) took one or more effective protective measures (e.g., wearing a mask and social distancing). However, a significantly higher annualized relapse rate (ARR) was observed in the 33 patients with treatment interruptions due to the pandemic compared to before it (p < 0.05), whereas ARR changes were not found in patients with continuous treatments or those without treatments (p > 0.05). Interruption frequency was significantly higher in patients with relapses compared to those without (34.9 vs. 15.7%, p < 0.01). For stable NMOSD patients during the pandemic, the risk of relapse due to treatment interruption may be higher than the risk of COVID-19 infection when protective measures are used, and continuous relapse-prevention treatments may be necessary.

Anti-aquaporin 4 IgG Is Not Associated With Any Clinical Disease Characteristics in Neuromyelitis Optica Spectrum Disorder

Background: Neuromyelitis optica spectrum disorder (NMOSD) is a clinically defined, inflammatory central nervous system (CNS) disease of unknown cause, associated with humoral autoimmune findings such as anti-aquaporin 4 (AQP4)-IgG. Recent clinical trials showed a benefit of anti-B cell and anti-complement-antibodies in NMOSD, suggesting relevance of anti-AQP4-IgG in disease pathogenesis. Objective: AQP4-IgG in NMOSD is clearly defined, yet up to 40% of the patients are negative for AQP4-IgG. This may indicate that AQP4-IgG is not disease-driving in NMOSD or defines a distinct patient endotype. Methods: We established a biobank of 63 clinically well-characterized NMOSD patients with an extensive annotation of 351 symptoms, patient characteristics, laboratory results and clinical scores. We used phylogenetic clustering, heatmaps, principal component and longitudinal causal interference analyses to test for the relevance of anti-AQP4-IgG. Results: Anti-AQP4-IgG was undetectable in 29 (46%) of the 63 NMOSD patients. Within anti-AQP4-IgG-positive patients, anti-AQP4-IgG titers did not correlate with clinical disease activity. Comparing anti-AQP4-IgG-positive vs. -negative patients did not delineate any clinically defined subgroup. However, anti-AQP4-IgG positive patients had a significantly (p = 0.022) higher rate of additional autoimmune diagnoses. Conclusion: Our results challenge the assumption that anti-AQP4-IgG alone plays a disease-driving role in NMOSD. Anti-AQP4-IgG might represent an epiphenomenon associated with NMOSD, may represent one of several immune mechanisms that collectively contribute to the pathogenesis of this disease or indeed, anti-AQP4-IgG might be the relevant factor in only a subgroup of patients.

The role and mechanisms of Microglia in Neuromyelitis Optica Spectrum Disorders

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune neurological disease that can cause blindness and disability. As the major mediators in the central nervous system, microglia plays key roles in immunological regulation in neuroinflammatory diseases, including NMOSD. Microglia can be activated by interleukin (IL)-6 and type I interferons (IFN-Is) during NMOSD, leading to signal transducer and activator of transcription (STAT) activation. Moreover, complement C3a secreted from activated astrocytes may induce the secretion of complement C1q, inflammatory cytokines and progranulin (PGRN) by microglia, facilitating injury to microglia, neurons, astrocytes and oligodendrocytes in an autocrine or paracrine manner. These processes involving activated microglia ultimately promote the pathological course of NMOSD. In this review, recent research progress on the roles of microglia in NMOSD pathogenesis is summarized, and the mechanisms of microglial activation and microglial-mediated inflammation, and the potential research prospects associated with microglial activation are also discussed.