Evaluation of CD137 and CD137L Transcript Levels and the Serum sCD137 in Immune-mediated Polyneuropathy.

Background: Abnormal humoral and cellular immune responses have been reported in immune-mediated polyneuropathies. CD137, as a costimulatory molecule and a TNF receptor superfamily member, has been demonstrated to have a key role in the pathogenesis of many autoimmune as well as inflammatory disorders. Objective: To evaluate the transcripts levels of CD137, its ligand (CD137L), and the serum levels of soluble CD137 (sCD137) in patients with immune-mediated polyneuropathy. Methods: A total of 45 patients and 46 sex and age-matched healthy individuals were enrolled in the study. CD137 and CD137L transcript levels were assessed by the Real-Time PCR, and the serum level of sCD137 was measured using the ELISA technique. The Bayesian regression model was used for statistical analysis at the 0.05 significance level in R 4.1.0 statistical environment. Results: Transcript levels of the CD137 and CD137L were higher in polyneuropathy patients in comparison with the healthy subjects (P=0.006 for both). Conversely, the mean level of sCD137 was significantly lower in the sera of patients compared to the controls (P<0.001). Conclusion: Our findings point to the possible role of CD137 and CD137L in immune-mediated polyneuropathy pathogenesis. More investigations are required to clarify the exact contributions of the mentioned molecules to the pathogenesis of immune-mediated polyneuropathies.

Anti-C2 Antibody ARGX-117 Inhibits Complement in a Disease Model for Multifocal Motor Neuropathy.

BACKGROUND AND OBJECTIVES: To determine the role of complement in the disease pathology of multifocal motor neuropathy (MMN), we investigated complement activation, and inhibition, on binding of MMN patient-derived immunoglobulin M (IgM) antibodies in an induced pluripotent stem cell (iPSC)-derived motor neuron (MN) model for MMN. METHODS: iPSC-derived MNs were characterized for the expression of complement receptors and membrane-bound regulators, for the binding of circulating IgM anti-GM1 from patients with MMN, and for subsequent fixation of C4 and C3 on incubation with fresh serum. The potency of ARGX-117, a novel inhibitory monoclonal antibody targeting C2, to inhibit fixation of complement was assessed. RESULTS: iPSC-derived MNs moderately express the complement regulatory proteins CD46 and CD55 and strongly expressed CD59. Furthermore, MNs express C3aR, C5aR, and complement receptor 1. IgM anti-GM1 antibodies in serum from patients with MMN bind to MNs and induce C3 and C4 fixation on incubation with fresh serum. ARGX-117 inhibits complement activation downstream of C4 induced by patient-derived anti-GM1 antibodies bound to MNs. DISCUSSION: Binding of IgM antibodies from patients with MMN to iPSC-derived MNs induces complement activation. By expressing complement regulatory proteins, particularly CD59, MNs are protected against complement-mediated lysis. Yet, because of expressing C3aR, the function of these cells may be affected by complement activation upstream of membrane attack complex formation. ARGX-117 inhibits complement activation upstream of C3 in this disease model for MMN and therefore represents an intervention strategy to prevent harmful effects of complement in MMN.

Anti-contactin-1 Antibodies Affect Surface Expression and Sodium Currents in Dorsal Root Ganglia.

BACKGROUND AND OBJECTIVES: As autoantibodies to contactin-1 from patients with chronic inflammatory demyelinating polyradiculoneuropathy not only bind to the paranodes where they are supposed to cause conduction failure but also bind to other neuronal cell types, we aimed to investigate the effect of anti-contactin-1 autoantibodies on contactin-1 surface expression in cerebellar granule neurons, dorsal root ganglion neurons, and contactin-1-transfected human embryonic kidney 293 cells. METHODS: Immunocytochemistry including structured illumination microscopy and immunoblotting was used to determine expression levels of contactin-1 and/or sodium channels after long-term exposure to autoantibodies from 3 seropositive patients. For functional analysis of sodium channels, whole-cell recordings of sodium currents were performed on dorsal root ganglion neurons incubated with anti-contactin-1 autoantibodies. RESULTS: We found a reduction in contactin-1 expression levels on dorsal root ganglion neurons, cerebellar granule neurons, and contactin-1-transfected human embryonic kidney 293 cells and decreased dorsal root ganglion sodium currents after long-term exposure to anti-contactin-1 autoantibodies. Sodium channel density did not decrease. DISCUSSION: Our results demonstrate a direct effect of anti-contactin-1 autoantibodies on the surface expression of contactin-1 and sodium currents in dorsal root ganglion neurons. This may be the pathophysiologic correlate of sensory ataxia reported in these patients.

Autoimmune glial fibrillary acidic protein astrocytopathy mimicking acute disseminated encephalomyelitis: A case report.

INTRODUCTION: Autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy is an increasingly recognized type of steroid-responsive autoimmune disease of the nervous system. Defined in 2016, it is associated with the presence of anti-GFAP immunoglobulinG in the serum or cerebrospinal fluid (CSF) of affected patients. PATIENT CHARACTERISTICS: Herein, we report a case of acute neurological symptoms, including headache, fever, confusion, and paralysis of the lower extremities. CSF analysis revealed lymphocytic pleocytosis and elevated protein levels, indicating acute disseminated encephalomyelitis, and the patient was given immunotherapy. Cranial magnetic resonance imaging showed multifocal T2/fluid-attenuated inversion recovery hyperintense signal changes in the periventricular white matter, and electromyography testing showed changes consistent with severe sensorimotor neuropathy, indicating the involvement of the brain and peripheral nerves. DIAGNOSES: Finally, a diagnosis of autoimmune GFAP astrocytopathy was confirmed due to the presence of GFAP-immunoglobulinG in the patient's CSF. INTERVENTIONS: The patient was treated with one course of intravenous immunoglobulin therapy, then followed with intravenous methylprednisolone (1.0 g/d for 3 days) and oral prednisolone. OUTCOMES: At 1 week after intravenous immunoglobulin therapy, his level of consciousness improved. However, flaccid paralysis persisted without substantial improvement. CONCLUSION: In conclusion, the provision of an accurate early diagnosis and appropriate treatment are crucial for improving the prognosis of patients with autoimmune GFAP astrocytopathy. Further, this case highlights the importance of recognizing the role of peripheral nerve involvement in GFAP autoimmunity.

Chronic Immune-Mediated Polyneuropathies.

This article discusses the chronic immune-mediated polyneuropathies, a broad category of acquired polyneuropathies that encompasses chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), the most common immune-mediated neuropathy, the CIDP variants, and the vasculitic neuropathies. Polyneuropathies associated with rheumatological diseases and systemic inflammatory diseases, such as sarcoidosis, will also be briefly covered. These patients' history, examination, serum studies, and electrodiagnostic studies, as well as histopathological findings in the case of vasculitis, confirm the diagnosis and differentiate them from the more common length-dependent polyneuropathies. Prompt identification and initiation of treatment is imperative for these chronic immune-mediated polyneuropathies to prevent disability and even death.

Acupuncture for HIV-associated distal symmetric peripheral neuropathy: A protocol for systematic review and meta-analysis.

BACKGROUND: Human immunodeficiency virus (HIV)-associated distal symmetric peripheral neuropathy (DSPN) is one of the most frequent neurological complications of HIV infection, and causes pain and dysaesthesias in millions globally. Many individuals with this infection report using acupuncture to manage their symptoms, but evidence supporting the use of acupuncture is limited. This systematic review will assess the effectiveness and safety of acupuncture for patients with HIV-associated DSPN. METHODS: Databases including MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, Scopus, Web of science, AMED (Allied and Complementary Medicine), the Chinese Biomedical Literature Database, the China National Knowledge Infrastructure, Wanfang Database, VIP Database and clinical trials registers (the WHO International Clinical Trials Registry Platform portal and www.ClinicalTrials.gov) will be electronically searched from inception to December 1, 2020. All randomized controlled trials in English or Chinese without restriction on publication status will be included. Selection of studies, extraction of data, and assessment of studies quality will be independently performed by 2 reviewers. The primary outcome measure will be the change in pain intensity assessed by validated scales. Secondary outcomes include change in neurologic summary scores, quality of life, physical function evaluated by admitted tools, and adverse events related to acupuncture reported in the included trials. If possible, a meta-analysis will be conducted to provide an estimate of the pooled treatment effect using Review Manager 5.3 statistical software. Otherwise, qualitative descriptive analysis will be given. The results will be presented as the risk ratio for binary data and the mean difference (MD) or standardized MD for continuous data. RESULTS: The results of the systematic review will be disseminated via publication in a peer-reviewed journal and presented at a relevant conference. CONCLUSION: This review will be the first review entirely focused on assessing the effectiveness and safety of acupuncture for HIV-associated DSPN. PROSPERO REGISTRATION NUMBER: CRD42020210994.

Clinical features with anti fibroblast growth factor receptor 3 (FGFR3) antibody-related polyneuropathy: a retrospective study.

BACKGROUND: Despite its initial association with sensory neuropathies, anti-fibroblast growth factor receptor 3 (FGFR3) antibodies have been since reported with a broad range of neuropathies and clinical features. The aim of the study is to report the clinical and electro diagnostic findings in a cohort of patients with sensory or sensorimotor polyneuropathy and anti-FGFR3 antibodies. METHODS: We performed a retrospective chart review to assess the clinical characteristics of patients with sensory or sensorimotor neuropathy related to FGFR3 antibodies. Descriptive statistics were reported using frequencies and percentages for categorical variables and median and interquartile range (IQR) for continuous variables. RESULTS: This study included 14 patients (9 women) with a median age of 51.9 years (IQR 48-57). The most common presenting symptoms were painful paresthesia (100%), gait instability (42.9%), constitutional symptoms (42.9%), and autonomic symptoms (28.6%). Onset of symptoms was chronic (≥12 weeks) in eight patients (57.1%). Examination showed a distal loss of sensation to pin prick (100%), as well as impaired vibration sensation (78.6%) and proprioception (35.7%), in the distal extremities. We also observed mild weakness in the distal lower-extremities (42.9%). Three patients (21.4%) had trigeminal neuralgia, three patients (21.4%) had co-existing autoimmune disease, and one patient (7.1%) had a history of renal cell carcinoma. The mean titer of FGFR3 antibody was 14,285.71 (IQR 5000-16,750). All 14 patients produced normal results in the neuropathy workup. Nerve conduction study and electromyography showed sensory axonal neuropathy in four patients (28.6%), sensorimotor axonal neuropathy in seven patients (50%), and a normal result in three patients (21.4%). For those with a normal NCS/EMG, a skin biopsy showed a non-length-dependent small fiber neuropathy. CONCLUSIONS: Neuropathy related to FGFR3 antibodies can potentially involve small and large fibers, sensory and motor fibers, and even the trigeminal nerve, which contributes to a highly variable clinical presentation.

Autologous Bone Marrow Mononuclear Cell Transplantation Therapy Improved Symptoms in Patients with Refractory Diabetic Sensorimotor Polyneuropathy via the Mechanisms of Paracrine and Immunomodulation: A Controlled Study.

TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR-TRC-12002570.URL: http://www.chictr.org.cn/showproj.aspx?proj=6981.

Immune-Mediated Neuropathies.

The immune-mediated neuropathies are a broad category of diseases differentiated by time course, affected nerve fibers, and disease associations. This article spans the common, well-defined inflammatory demyelinating polyradiculoneuropathies (Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy) to the rarer, acquired demyelinating neuropathy variants (Miller-Fisher syndrome and multifocal motor neuropathy), vasculitic neuropathies, and sensory neuronopathies (dorsal root ganglionopathies). These case studies illustrate the characteristic clinical patterns of the immune-mediated neuropathies encountered in neurologic practice. Recommendations for diagnostic evaluation and treatment approach accompany each case. Prompt recognition of these disorders is imperative; delays in treatment may result in prolonged morbidity and permanent disability.

Management challenges for chronic dysimmune neuropathies during the COVID-19 pandemic.

Since March 2020, the COVID-19 pandemic has led to the need to re-think the delivery of services to patients with chronic dysimmune neuropathies. Telephone/video consultations have become widespread but have compounded concerns about objective evaluation. Therapeutic decisions need, more than ever before, to be considered in the best interests of both patients, and society, while not denying function-preserving/restoring treatment. Immunoglobulin therapy and plasma exchange, for those treated outside of the home, expose patients to the hazards of hospital or outpatient infusion centers. Steroid therapy initiation and continuation pose increased infectious risk. Immunosuppressant therapy similarly becomes highly problematic, with the risks of treatment continuation enhanced by uncertainties regarding duration of the pandemic. The required processes necessitate considerable time and effort especially as resources and staff are re-deployed to face the pandemic, but are essential for protecting this group of patients and as an integral part of wider public health actions.

The Bruton tyrosine kinase inhibitor ibrutinib improves anti-MAG antibody polyneuropathy.

OBJECTIVE: To assess whether neuropathy with anti-myelin-associated glycoprotein (MAG) antibody may improve after treatment with ibrutinib, an oral inhibitor of Bruton tyrosine kinase, we prospectively treated with ibrutinib a cohort of 3 patients with anti-MAG neuropathy and Waldenström macroglobulinemia (WM). METHODS: All 3 patients underwent bone marrow biopsy showing WM, with MYD88 L265P mutated and CXCR4S338X wild type, and were started on ibrutinib 420 mg/die. Patients were assessed at baseline, at 3-6-9 months, and at 12 months in 2 patients with a longer follow-up, using Inflammatory Neuropathy Cause and Treatment (INCAT) Disability Score, INCAT sensory sum score, and Medical Research Council sum score. The modified International Cooperative Ataxia Rating Scale was performed in 2 patients, whereas it was not used in the patient with Parkinson disease as a major comorbidity. Responders were considered the patients improving by at least one point in 2 clinical scales. RESULTS: All the patients reported an early and subjective benefit, consistent with the objective improvement, especially of the sensory symptoms as shown by clinical scales. Treatment was well tolerated. CONCLUSION: These preliminary data point to a possible efficacy of ibrutinib in anti-MAG antibody neuropathy, which is the most common disabling paraproteinemic neuropathy, where active treatment is eagerly needed. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that for patients with anti-MAG antibody neuropathy, ibrutinib improves neuropathy symptoms.

GFAP IgG associated inflammatory polyneuropathy.

BACKGROUND: GFAP (glial fibrillary acidic protein)-IgG is predominantly associated with meningoencephalomyelitis, and neuropathy presentations are rare. METHODS: We reviewed clinical, electrodiagnostic and histopathological presentations of GFAP-IgG associated peripheral neuropathy. RESULTS: We identified six cases, five of whom had peripheral neuropathy as the initial presentation. Acute/subacute polyradicluoneuropathy or proximal nerve involvement was a common presentation. Three had demyelinating neuropathies on electrophysiological studies. Nerve biopsies (n = 2) demonstrated T-cell predominant perivascular inflammatory collections, and all patients with clinical follow up responded favorably to immunotherapy. CONCLUSION: GFAP neuropathy represents a potentially treatable immune-mediated neuropathy and can occur with or without co-existing meningoencephalomyelitis.

Immune-mediated inflammatory polyneuropathy overlapping Charcot-Marie-Tooth 1B.

Charcot Marie Tooth (CMT) due to myelin protein zero (MPZ) mutations, may cause a wide variation of phenotypes, depending on the localization of the mutation within the gene. Among the most common phenotypes are: an infantile onset disease with extremely slow nerve conduction velocities (CMT1B) and an adult onset phenotype with nerve velocities in the axonal range (CMT2I). We reported a patient with CMT1B (MPZ p.Ser63del mutation) which developed an overlapping immune mediated polyradiculoneuropathy with recurrent episodes of quadriparesis and cranial nerve involvement. We observed reversible conduction block on serial neurophysiologic studies, non-uniform demyelination and good clinical response to prednisone and cyclophosphamide, as evidenced by objective functional recovery. Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)-like characteristics have not yet been described associated with a MPZ p.Ser63del mutation. This description adds evidence indicating that a defective structural myelin protein may predispose peripheral nerves to immune attacks.

Antibodies against nodo-paranodal proteins are not present in genetic neuropathies.

OBJECTIVE: To study the presence of nodal and paranodal immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies in patients with genetic neuropathies. METHODS: A total of 108 patients with genetic neuropathies from 3 different centers were included. The presence of IgG and IgM antibodies against neurofascin-155 (NF155), nodal neurofascin (NF186 and NF140), and contactin-1 (CNTN1) were investigated with a cell-based assay (CBA) using immunocytochemistry in transfected HEK293 cells. Sera with positive or uncertain results were further tested by ELISA and immunohistochemistry in pig teased-nerve fibers. RESULTS: Six patients with Charcot-Marie-Tooth disease (CMT) had an uncertain staining pattern for IgM against nodal neurofascin that was not confirmed by ELISA. Two patients with CMT had an uncertain staining pattern for IgG against nodal neurofascin that was not confirmed by ELISA or immunohistochemistry. One patient with CMT with a confirmed GJB1 mutation tested positive for IgG against NF155 by CBA and ELISA (1/900), but was not confirmed by immunohistochemistry and was ultimately classified as negative. CONCLUSIONS: Antibodies against nodal or paranodal antigens were not detected in our cohort of patients with CMT, as previously reported. Some patients may falsely test positive for any of the techniques; confirmatory techniques should be incorporated into the routine testing.

Demyelinating polyneuropathy in goats lacking prion protein.

Studies in mice with ablation of Prnp, the gene that encodes the cellular prion protein (PrPC ), have led to the hypothesis that PrPC is important for peripheral nerve myelin maintenance. Here, we have used a nontransgenic animal model to put this idea to the test; namely, goats that, due to a naturally occurring nonsense mutation, lack PrPC . Teased nerve fiber preparation revealed a demyelinating pathology in goats without PrPC . Affected nerves were invaded by macrophages and T cells and displayed vacuolated fibers, shrunken axons, and onion bulbs. Peripheral nerve lipid composition was similar in young goats with or without PrPC , but markedly different between corresponding groups of adult goats, reflecting the progressive nature of the neuropathy. This is the first report of a subclinical demyelinating polyneuropathy caused by loss of PrPC function in a nontransgenic mammal.

Anti-MAG IgM: differences in antibody tests and correlation with clinical findings.

OBJECTIVES: Anti-myelin-associated glycoprotein (MAG) antibody is associated with clinically heterogeneous polyneuropathies. Our purpose was to compare neuropathy phenotypes identified by different anti-MAG tests' results. METHODS: Cohort study: Sera from 40 neuropathy anti-MAG EIA positive patients were tested for anti-MAG by Western blot (WB), for anti-peripheral nerve myelin (PNM) on monkey nerve by immunofluorescence assay (IFA), and for anti-HNK1 on rat CNS slices by IFA. Anti-sulfatide antibodies, for comparison, were also tested by EIA. RESULTS: Among 40 anti-MAG EIA positive sera, 85% also had anti-PNM IFA reactivity and 67.5% bind HNK1 on rat CNS. Anti-HNK1 positive patients had the classical predominantly distal acquired demyelinating symmetric (DADS) neuropathy with a benign course, while anti-PNM positive but anti-HNK1 negative patients had predominantly axonal neuropathy with a high frequency of anti-sulfatide reactivity and the worst long-term prognosis. Anti-MAG EIA positive patients without anti-PNM or anti-HNK1 IFA reactivity had a CIDP-like polyneuropathy. CONCLUSION: Different methods to test for anti-MAG antibodies identify different clinical and electrophysiological findings, as well as long-term outcome. HNK1 reactivity is the strongest marker of DADS.

Outcomes after single-cycle rituximab monotherapy in patients with anti-MAG polyneuropathy: A bi-center experience with an average follow-up of 11 years.

Rituximab is efficacious in myelin-associated glycoprotein (MAG) polyneuropathy, but the question on timing of retreatments is open. We studied 21 anti-MAG polyneuropathy patients who responded to a first cycle of rituximab, were followed-up for an average of 11.2 years, and were retreated only when relapsing. Baseline serum B-cell-activating factor (BAFF) levels were measured. Clinical improvements lasted on average 6 years, and as many as 71% of the patients resulted long-lasting responders. Severity of disease and high serum BAFF levels (cut-off ≥860 pg/mL for relapse risk) at onset seemed to predict worse prognosis. Measurements of these variables could help deal with the issue of maintenance rituximab therapy in MAG polyneuropathy.

Elimination of activating Fcγ receptors in spontaneous autoimmune peripheral polyneuropathy model protects from neuropathic disease.

Spontaneous autoimmune peripheral polyneuropathy (SAPP) is a reproducible mouse model of chronic inflammatory peripheral neuropathy in female non-obese diabetic mice deficient in co-stimulatory molecule, B7-2 (also known as CD86). There is evidence that SAPP is an interferon-γ, CD4+ T-cell-mediated disorder, with autoreactive T-cells and autoantibodies directed against myelin protein zero involved in its immunopathogenesis. Precise mechanisms leading to peripheral nerve system inflammation and nerve injury including demyelination in this model are not well defined. We examined the role of activating Fc-gamma receptors (FcγRs) by genetically ablating Fcγ-common chain (Fcer1g) shared by all activating FcγRs in the pathogenesis of this model. We have generated B7-2/ Fcer1g-double null animals for these studies and found that the neuropathic disease is substantially ameliorated in these animals as assessed by behavior, electrophysiology, immunocytochemistry, and morphometry. Our current studies focused on characterizing systemic and endoneurial inflammation in B7-2-null and B7-2/ Fcer1g-double nulls. We found that accumulation of endoneurial inflammatory cells was significantly attenuated in B7-2/ Fcer1g-double nulls compared to B7-2-single nulls. Whereas, systemically the frequency of CD4+ regulatory T cells and expression of immunosuppressive cytokine, IL-10, were significantly enhanced in B7-2/ Fcer1g-double nulls. Overall, these findings suggest that elimination of activating FcγRs modulate nerve injury by altering endoneurial and systemic inflammation. These observations raise the possibility of targeting activating FcγRs as a treatment strategy in acquired inflammatory demyelinating neuropathies.