anti-MAG IgM Research Articles

A novel cell-based immunofluorescence assay for the detection of autoantibodies to myelin-associated glycoprotein.

Peripheral neuropathy with antibodies to myelin-associated glycoprotein (MAG) is an autoimmune demyelinating disorder of the peripheral nervous system caused by pathogenic IgM recognizing the human natural killer-1 glycoepitope expressed on MAG. This study aimed to analyze the performance of a new indirect immunofluorescence cell-based assay (CBA, EUROIMMUN) for the detection of anti-MAG IgM. Antibody reactivity was determined in sera from 95 patients with clinical and neurophysiological evidence of anti-MAG-associated neuropathy and in control samples from 55 patients with other forms of peripheral neuropathy. Compared to the results of the gold standard method (ELISA, Bühlmann) and using samples at a dilution of 1:100, the CBA had a sensitivity of 98.9% and a specificity of 100% (PPV 100%, NPV 98.2%). In conclusion, the CBA allows the detection of antibodies to MAG using an easy and standardized technique, and it presents a sensitive and specific alternative to the more time-consuming ELISA. Larger studies are needed to address anti-MAG titer monitoring in parallel with clinical activity.

Prospective Study of Acalabrutinib with Rituximab in Patients with Symptomatic Anti-MAG Mediated IgM Peripheral Neuropathy

Background: Peripheral neuropathy (PN) occurs in 20-25% of patients with an IgM paraprotein and up to 50% of these patients have an anti-myelin associated glycoprotein (MAG) antibody which is frequently associated with sensory ataxia and distal limb weakness negatively affecting function and quality of life. While rituximab is active, its activity is limited as a monotherapy and often associated with an IgM flare that can potentiate PN. BTK-inhibitors can block rituximab-associated IgM flare and are proven to markedly reduce serum IgM in Waldenström's Macroglobulinemia (WM). We therefore initiated this trial to evaluate a novel treatment for anti-MAG PN. Methods: We initiateda prospective, single-arm phase II study of acalabrutinib and rituximab (NCT05065554). Patients with an anti-MAG antibody with an IgM monoclonal gammopathy or WM; and a predominantly sensory demyelinating PN with a modified Rankin score of ≥1 with progressive symptoms or a score of ≥2 are eligible. Treatment consists of continuous oral acalabrutinib (100 mg twice daily) with rituximab weekly in cycles 1 and 4. Each cycle is 28 days. The primary endpoint is to evaluate the hematologic response rate. The key secondary endpoint is to evaluate the proportion of patients that achieve improvement or stability in PN based on the Inflammatory Rasch-built Overall Disability Scale (I-RODS) patient-reported disability scale. Additional secondary neurologic endpoints include the Inflammatory Neuropathy Cause and Treatment (INCAT) disability score, MRC distal sum score, INCAT sensory sum score, and a neuropathy-specific quality of life scale (IN-QOL). We hypothesize that 75% of participants (H1) will have a hematologic response versus a null (H0) of 50% or lower. With 33 evaluable patients, there will be 82% power to detect a significant difference with an alpha (2-sided) of 0.04. Results: Eight patients, including 4 females, have enrolled as of July 1, 2023. The median age is 70 years (range 65-76), and median ECOG is 1. Median I-RODS score at baseline was 41 (range 23-48; 48 = no disability). All patients have an IgM kappa paraprotein with median baseline serum IgM of 975 mg/dL (range 226-2137), kappa free light chain of 28 mg/L (range 16-47), and M-spike of 0.6 g/dL (range 0.17-1.1). Anti-MAG antibody titer range is 1:70,000 to 1:819,200 IU/L. Bone marrow biopsy showed no disease in 4 patients, a clonal plasma cell population in 1 patient, and lymphoplasmacytic infiltrate in 3 patients. No adenopathy or splenomegaly were detected on baseline CT scans. Six patients (75%) are MYD88 mutated and none CXCR4 mutated. Five patients had prior rituximab therapy and two received prior IVIG. With a median time on treatment of 175 days (range 28-510), the overall response rate among 7 evaluable patients using IWWM-11 criteria was 86%. Categorical responses include 2 very good partial responses (≥90% decrease in IgM, or normalization of IgM with persistent IgM monoclonal protein); 1 partial response (≥50% but <90% decrease in IgM); 3 minor responses (≥25% but <50% decrease in IgM) and 1 stable disease. Four of 7 patients (57%) had improvement in the I-RODS score. Median improvement was 0.5 points (range -4 to 11). One patient was removed from the trial after 28 days due to grade 3 elevation in ALT. Two other reversible grade 3 adverse events occurred including rituximab related infusion reaction and syncope unrelated to treatment. Conclusions: The combination of acalabrutinib and rituximab has demonstrated activity in this first prospective study that is evaluating BTK-inhibition with CD20 directed therapy in patients with IgM related anti-MAG PN. Hematologic responses occurred in 86% of patients and 57% had an improvement in the I-RODS score. Treatment is well tolerated. Additional data from more detailed neurologic assessments are forthcoming. The trial continues to enroll patients. Our findings provide a framework to develop novel, more effective treatment options for anti-MAG PN.

Rapidly Progressive AIDP Secondary To Waldenström’s Macroglobulinemia, A Rare Cause With Fatal Respiratory Depression And Autonomic Instability (P10-5.001)

<h3>Objective:</h3> To report a rare case of AIDP secondary to Waldenström’s Macroglobulinemia <h3>Background:</h3> Acute inflammatory demyelinating polyneuroradiculopathy (AIDP) is a rare complication of Waldenström’s Macroglobulinemia (WM). Typical findings are a slowly progressive neuropathy, thought to be mediated through autoantibodies. Anti-myelin-associated glycoprotein (MAG) antibodies are found in 50% of patients with WM and neuropathy. A rapidly progressing course can result in fatal respiratory depression and cardiac arrhythmias. <h3>Design/Methods:</h3> Information regarding patient obtained via retrospective review of electronic medical records. <h3>Results:</h3> This is a 77 year-old male with chronic WM presenting with rapidly progressive appendicular weakness over several days. Neurologic exam was notable for diffuse areflexia, appendicular weakness (MRC Grade 1–2 of 5), and globally reduced sensation. Initially, no bulbar weakness was noted but as symptoms progressed patient required intubation on hospital day #2. MRI brain was unremarkable, however, MRI lumbosacral spine showed enhancement of nerve. Plasma levels of Anti-MAG IgM antibody (1:102400) were substantially elevated. CSF analysis showed elevated protein (55), glucose (40), and 76 nucleated cells (70% lymphocytes). Electromyography and nerve conduction studies revealed temporal dispersion, reduced motor unit recruitment and rapid firing in all muscles. Patient was treated with intravenous immunoglobulins (IVIG) 2g/kg over 5 days followed by plasma exchange when IVIG had no effect. The patient’s hospital course was complicated by severe autonomic instability with periods of bradycardia necessitating atropine and percutaneous pacing. The patient also suffered pneumonia and eventually required tracheostomy and feeding tube placement. After a prolonged ICU course, the family eventually decided to change code status to do not resuscitate and patient expired on Hospital Day #19 following an episode of bradycardia refractory to atropine. <h3>Conclusions:</h3> Waldenström’s Macroglobulinemia is an unusual etiology of AIDP. This case revealed the treatment challenges of AIDP including respiratory depression and autonomic instability. <b>Disclosure:</b> Dr. Yu has nothing to disclose. Dr. Munir has nothing to disclose. The institution of Dr. Mohney has received research support from NIH.

Serum neurofilament light chain, contactin-1 and complement activation in anti-MAG IgM paraprotein-related peripheral neuropathy

IntroductionIn anti-myelin-associated glycoprotein IgM paraprotein-related peripheral neuropathy (anti-MAG PN), there is a lack of reliable biomarkers to select patients eligible for therapy and for evaluating treatment effects, both in routine practice and in clinical trials. Neurofilament light chain (NfL) and contactin-1 (CNTN1) can serve as markers of axonal and paranodal damage. Complement activation is involved in the pathogenesis in anti-MAG PN. We, therefore, hypothesized that serum NfL, CNTN1, C3b/c and C4b/c may function as biomarkers of disease activity in anti-MAG PN.MethodsIn this prospective cohort study, we included 24 treatment-naïve patients with anti-MAG PN (mean age 69 years, 57% male) that had IgM paraproteinemia, a high IgM MAG-antibody, and clinical diagnosis of anti-MAG PN by a neurologist specialized in peripheral nerve disorders. We measured serum NfL, CNTN1, C3b/c and C4b/c, reference values were based on healthy controls. As controls, 10 treatment-naïve patients with IgM Monoclonal gammopathy of undetermined significance (MGUS) or Waldenström’s Macroglobulinemia (mean age 69 years, 60% male) without signs of neuropathy were included (non-PN).ResultsNfL, CNTN1 levels in serum were mostly normal in anti-MAG PN patients and comparable to non-PN patients. C3b/c and C4b/c levels were normal in anti-MAG PN patients.ConclusionOur results do not support serum NfL, CNTN1, and C3b/c and C4b/c as potential biomarkers in anti-MAG PN, although we cannot exclude that subgroups or subtle abnormalities could be found in a much larger cohort with longitudinal follow-up.

Complex Autoantibody Responses Occur following Moderate to Severe Traumatic Brain Injury

Abstract Most of the variation in outcome following severe traumatic brain injury (TBI) remains unexplained by currently recognized prognostic factors. Neuroinflammation may account for some of this difference. We hypothesized that TBI generated variable autoantibody responses between individuals that would contribute to outcome. We developed a custom protein microarray to detect autoantibodies to both CNS and systemic Ags in serum from the acute-phase (the first 7 d), late (6–12 mo), and long-term (6–13 y) intervals after TBI in human patients. We identified two distinct patterns of immune response to TBI. The first was a broad response to the majority of Ags tested, predominantly IgM mediated in the acute phase, then IgG dominant at late and long-term time points. The second was responses to specific Ags, most frequently myelin-associated glycopeptide (MAG), which persisted for several months post-TBI but then subsequently resolved. Exploratory analyses suggested that patients with a greater acute IgM response experienced worse outcomes than predicted from current known risk factors, suggesting a direct or indirect role in worsening outcome. Furthermore, late persistence of anti-MAG IgM autoantibodies correlated with raised serum neurofilament light concentrations at these time points, suggesting an association with ongoing neurodegeneration over the first year postinjury. Our results show that autoantibody production occurs in some individuals following TBI, can persist for many years, and is associated with worse patient outcome. The complexity of responses means that conventional approaches based on measuring responses to single antigenic targets may be misleading.

Selective inhibition of anti-MAG IgM autoantibody binding to myelin by an antigen-specific glycopolymer.

Anti‐myelin‐associated glycoprotein (MAG) neuropathy is a disabling autoimmune peripheral neuropathy that is caused by circulating monoclonal IgM autoantibodies directed against the human natural killer‐1 (HNK‐1) epitope. This carbohydrate epitope is highly expressed on adhesion molecules such as MAG, a glycoprotein present in myelinated nerves. We previously showed the therapeutic potential of the glycopolymer poly(phenyl disodium 3‐O‐sulfo‐β‐d‐glucopyranuronate)‐(1→3)‐β‐d‐galactopyranoside (PPSGG) in selectively neutralizing anti‐MAG IgM antibodies in an immunological mouse model and ex vivo with sera from anti‐MAG neuropathy patients. PPSGG is composed of a biodegradable backbone that multivalently presents a mimetic of the HNK‐1 epitope. In this study, we further explored the pharmacodynamic properties of the glycopolymer and its ability to inhibit the binding of anti‐MAG IgM to peripheral nerves. The polymer selectively bound anti‐MAG IgM autoantibodies and prevented the binding of patients’ anti‐MAG IgM antibodies to myelin of non‐human primate sciatic nerves. Upon PPSGG treatment, neither activation nor inhibition of human and murine peripheral blood mononuclear cells nor alteration of systemic inflammatory markers was observed in mice or ex vivo in human peripheral blood mononuclear cells. Intravenous injections of PPSGG to mice immunized against the HNK‐1 epitope removed anti‐MAG IgM antibodies within less than 1 hr, indicating a fast and efficient mechanism of action as compared to a B‐cell depletion with anti‐CD20. In conclusion, these observations corroborate the therapeutic potential of PPSGG for an antigen‐specific treatment of anti‐MAG neuropathy. Read the Editorial Highlight for this article on page 465.

A sugar‐coated strategy to treat a rare neurologic disease provides a blueprint for a decoy glycan therapeutic and a potential vaccine for CoViD‐19

In a rare neurologic disease known as IgM monoclonal gammopathy the immune system targets a sulfated trisaccharide known as the Human Natural Killer‐1 (HNK‐1) epitope that comprises a constituent of the myelin sheath known as MAG (myelin‐associated glycoprotein). This Editorial highlights a study by Aliu and colleagues in the current issue of the Journal of Neurochemistry, in which the investigators constructed a biodegradable poly‐l‐lysine backbone with multiple copies of this sulfated HNK‐1 trisaccharide. This decoy, poly(phenyl disodium 3‐O‐sulfo‐β‐d‐glucopyranuronate)‐(1→3)‐β‐d‐galactopyranoside, known as PPSGG, removed anti‐MAG IgM autoantibodies from the blood, while not activating the immune system. These findings provide a path for the selective removal of a pathogenic set of antibodies that target the myelin sheath resulting in neuropathy. These findings are applicable to a parallel strategy for the generation of polysaccharides similar to those present in the receptor‐binding domain of CoViD‐19, which might inhibit viral adhesion to its receptor, the angiotensin‐converting enzyme‐2 (ACE2) protein, thereby impairing cellular uptake of the virus itself. The deployment of complex polysaccharides that mimic actual COVID19 polysaccharides on the spike protein may also provide a feasible structural basis for a vaccine. Carbohydrate mimics, if conjugated to a carrier or backbone, might provoke an immune response to the spike protein. A vaccine that targets critical carbohydrates on COVID19, and then neutralizes the virus would recapitulate a successful strategy employed in other microbial vaccines, like the pneumococcal vaccines and the meningococcal vaccines. These vaccines direct an immune response to complex carbohydrates and successfully prevent life‐threatening disease. This paper provides lessons from a rare neurologic disease that may teach us strategies applicable to a global pandemic.

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

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. 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. 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. 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.

Serum cytokine patterns in immunoglobulin m monoclonal gammopathy-associated polyneuropathy.

Polyneuropathy with immunoglobulin M monoclonal gammopathy (IgM-PNP) is associated with the presence of IgM antibodies against nerve constituents such as myelin associated glycoprotein (MAG) and gangliosides. To test whether B-cell-stimulating cytokines are increased in IgM-PNP, we measured serum concentrations of 11 cytokines in 81 patients with IgM-PNP and 113 controls. Median interleukin (IL)-6 concentrations were higher in patients with IgM-PNP, and median IL-10 concentrations were higher in the subgroup with anti-MAG IgM antibodies. These serum concentrations were not increased in 110 patients with multifocal motor neuropathy. Median IL-6 and IL-10 serum concentrations differ between patients with anti-MAG neuropathy and other patients with IgM-PNP compared with healthy and neuropathy controls. These differences may indicate differences in immune-mediated disease mechanisms. Muscle Nerve 59:694-698, 2019.

Anti-MAG neuropathy: Role of IgM antibodies, the paranodal junction and juxtaparanodal potassium channels

ObjectiveTo improve understanding of disease pathophysiology in anti-myelin-associated glycoprotein (anti-MAG) neuropathy to guide further treatment approaches. MethodsAnti-MAG neuropathy patients underwent clinical assessments, nerve conduction and excitability studies, and ultrasound assessment. ResultsPatients demonstrated a distinctive axonal excitability profile characterised by a reduction in superexcitability [MAG: −14.2 ± 1.6% vs healthy controls (HC): −21.8 ± 1.2%; p < 0.01] without alterations in most other excitability parameters. Mathematical modelling of nerve excitability recordings suggested that changes in axonal function could be explained by a 72.5% increase in juxtaparanodal fast potassium channel activation and an accompanying hyperpolarization of resting membrane potential (by 0.3 mV) resulting in a 94.2% reduction in discrepancy between anti-MAG data and the healthy control model. Superexcitability changes correlated strongly with clinical and neurophysiological parameters. Furthermore, structural assessments demonstrated a proximal pattern of nerve enlargement (C6 nerve root cross-sectional area: 15.9 ± 8.1 mm2 vs HC: 9.1 ± 2.3 mm2; p < 0.05). ConclusionsThe imaging and neurophysiological results support the pathogenicity of anti-MAG IgM. Widening between adjacent loops of paranodal myelin due to antibodies would expand the pathway from the node to the juxtaparanode, increasing activation of juxtaparanodal fast potassium channels, thereby impairing saltatory conduction. SignificancePotassium channel blockers may prove beneficial in restoring conduction closer to its normal state and improving nerve function in anti-MAG neuropathy.

Selective in vivo removal of pathogenic anti-MAG autoantibodies, an antigen-specific treatment option for anti-MAG neuropathy

Anti-MAG (myelin-associated glycoprotein) neuropathy is a disabling autoimmune peripheral neuropathy caused by monoclonal IgM autoantibodies that recognize the carbohydrate epitope HNK-1 (human natural killer-1). This glycoepitope is highly expressed on adhesion molecules, such as MAG, present in myelinated nerve fibers. Because the pathogenicity and demyelinating properties of anti-MAG autoantibodies are well established, current treatments are aimed at reducing autoantibody levels. However, current therapies are primarily immunosuppressive and lack selectivity and efficacy. We therefore hypothesized that a significant improvement in the disease condition could be achieved by selectively neutralizing the pathogenic anti-MAG antibodies with carbohydrate-based ligands mimicking the natural HNK-1 glycoepitope 1. In an inhibition assay, a mimetic (2, mimHNK-1) of the natural HNK-1 epitope blocked the interaction of MAG with pathogenic IgM antibodies from patient sera but with only micromolar affinity. Therefore, considering the multivalent nature of the MAG-IgM interaction, polylysine polymers of different sizes were substituted with mimetic 2. With the most promising polylysine glycopolymer PL84(mimHNK-1)45 the inhibitory effect on patient sera could be improved by a factor of up to 230,000 per epitope, consequently leading to a low-nanomolar inhibitory potency. Because clinical studies indicate a correlation between the reduction of anti-MAG IgM levels and clinical improvement, an immunological surrogate mouse model for anti-MAG neuropathy producing high levels of anti-MAG IgM was developed. The observed efficient removal of these antibodies with the glycopolymer PL84(mimHNK-1)45 represents an important step toward an antigen-specific therapy for anti-MAG neuropathy.

Humoral response against myelin associated glycoprotein reflects oligodendroglial degeneration in Parkinson's disease.

Identification of disease-specific diagnostic and prognostic biomarkers which would enable early detection and follow-up of Parkinson's disease (PD) is a crucial problem. Recently, we confirmed the presence of adaptive immune response against different glial-derived antigens in PD. The aim of the study was to assess humoral response against myelin-associated glycoprotein (MAG) on a larger group of PD patients. IgM autoantibodies against MAG were measured by an ELISA system in 66 PD patients and 66 control subjects. The study confirmed a significantly increased production of anti-MAG IgM antibodies in parkinsonian patients (p<0.05). No correlations were found between anti-MAG IgM antibody titers and disease severity measured on the Hoehn-Yahr scale, MMSE or age of PD onset (p>0.05). The results provide evidence for activation of humoral response against MAG in PD patients, but argue against the utility of anti-MAG antibodies as biomarkers of disease severity. The results additionally indicate the potential protective role of autoimmunity in maintaining the body's homeostasis, which may involve the clearance of abnormal proteins. Further studies are necessary to confirm the role of anti-MAG antibodies as biomarkers of PD, especially in relation to other neurodegenerative disorders.

Long‐term efficacy of rituximab in IgM anti‐myelin‐associated glycoprotein neuropathy: RIMAG follow‐up study

The Rituximab vs. Placebo in Polyneuropathy Associated With Anti-MAG IgM Monoclonal Gammopathy (RIMAG) study showed no improvement using the inflammatory neuropathy cause and treatment sensory score (ISS) as primary outcome in patients with IgM anti-myelin-associated glycoprotein neuropathy (IgM anti-MAG neuropathy) treated with rituximab, when compared with placebo. However, some secondary outcomes seemed to improve in the per protocol analysis. Patients from one participating center in the RIMAG study underwent a new evaluation after a median follow-up of 6 (interquartile range (IQR) 4.9; 6.5) years, using the same outcome measures used in the original study. Data were recorded in seven rituximab patients (group 1) and in eight placebo patients (group 2). In group 2, six of eight patients received immunotherapy during follow-up, while only two of seven did in group 1. No significant change was observed in either the ISS or the secondary outcomes in both groups, with the exception of worsening in the 10-m walk time in group 2 (p = 0.016). The RIMAG follow-up study failed to find any significant change in most outcome measures in patients from the RIMAG study, some of them having received new immunotherapies. This study stresses the lack of useful clinical scales sensitive enough to capture small, even meaningful, improvement in IgM anti-MAG neuropathy.

Can Antibodies Against Glial Derived Antigens be Early Biomarkers of Hippocampal Demyelination and Memory Loss in Alzheimer's Disease?

Alzheimer's disease (AD) is known to exhibit well characterized pathologies including the extracellular accumulation of amyloid plaques, intra-axonal presence of neurofibrillary tangles, and glial hypertrophy. Nevertheless, the nature of myelin pathology in AD has not been well studied. Recent studies on animal models of AD, however, revealed focal demyelination within amyloid-β plaques in hippocampus. In a view of this finding, we decided to assess humoral response against proteins of myelin sheath in AD, in the hope of identifying early biomarkers of memory loss and neuropathological process characteristic of AD. We assessed antibodies levels against proteins of the myelin sheath: myelin oligodendrocyte glycoprotein (MOG), myelin basic protein (MBP), myelin-associated glycoprotein (MAG), and proteolipoprotein (PLP) in sera of 26 AD patients and 26 healthy controls, using commercially available ELISA system (Mediagnost, Germany). In the AD patient subgroup, significantly higher titers were observed for all types of assessed IgG autoantibodies compared to healthy control subjects (anti-MOG, anti-MAG, anti-MBP, anti-PLP). The titers of most of the investigated IgM antibodies were also higher in AD patients (p < 0.05), with the exception of anti-MAG IgM antibodies (p > 0.05). The study provides the evidence for the significantly increased production of autoantibodies against proteins of myelin sheath in AD. These results can be of importance in the light of emerging data from animal models of AD, indicating early demyelination of hippocampal region. Further studies on larger population are necessary to confirm whether these autoantibodies could serve as early biomarkers of AD in humans.

Diagnostic Utility of Auto Antibodies in Inflammatory Nerve Disorders

A wide range of autoantibodies have been described in immune-mediated nerve disorders that target glycans borne by glycolipids and glycoproteins enriched in the peripheral nerves. Their use as diagnostic biomarkers is very widespread, despite some limitations on sensitivity and specificity, and the lack of standardized assays and access to quality assurance schemes. Although many methods have been applied to measurement, ELISA, in the form of commercial kits or in-house assays, still remains the most widely available and convenient assay methodology.Some antibodies have a particularly robust and widely appreciated clinical significance. Thus, the anti-MAG IgM antibodies that are found in IgM paraprotein related neuropathies define a relatively uniform clinical and prognostic phenotype. IgG antibodies against gangliosides GM1 and GD1a are strongly associated with motor axonal variants of Guillain-Barré syndrome, and anti-GQ1b with Miller Fisher syndrome. In other chronic neuropathies, antibodies against disialylated gangliosides including GD1b and GD3 are detected in ataxic neuropathies, usually associated with an IgM paraprotein, and antibodies against GM1 and the complex GM1:GalC are frequently found in multifocal motor neuropathy. Unfortunately, autoantibodies strongly associated with the diagnosis of chronic inflammatory demyelinating polyneuropathies and with demyelinating forms of GBS are still lacking.Identification of autoantibodies that map onto a specific clinical phenotype not only allows for improved classification, but also provides better understanding of the pathophysiology of inflammatory neuropathies and the potential for therapeutic interventions.

Acute neurological worsening after Rituximab treatment in patients with anti-MAG neuropathy

BackgroundPatients with peripheral neuropathy and anti-MAG monoclonal IgM may respond to Rituximab, a humanized monoclonal anti-CD20 antibody. MethodsWe report on three patients with peripheral neuropathy and anti-MAG monoclonal IgM who deteriorated under Rituximab and reviewed seven previously published cases. ResultsWorsening was acute and severe, and occurred during the treatment period. All the patients improved after deterioration but at final evaluation only one was improved comparatively to baseline, five were worsened and four were stabilized. Deterioration was not clearly associated with an increase of the anti-MAG antibody titer. Two patients received Rituximab prior or after the course which induced worsening without adverse reaction. ConclusionAlthough rare, acute worsening of the neuropathy can occur after Rituximab. The deterioration is however reversible within some weeks to several months.

Clinical, electrophysiological and immunological study of peripheral nerves in Egyptian patients with monoclonal gammopathies

Monoclonal antibodies are found in approximately 10% of patients with peripheral neuropathy (PN) of unknown etiology. Several autoantibodies, including anti-MAG (myelin-associated glycoprotein) antibodies, have been reported to induce neuropathy. It has been suggested that over 50% of patients with PN and IgM monoclonal gammopathy (MG) have anti-MAG IgM antibodies in their sera. This work aimed at studying the frequency and characteristics of PN in a group of Egyptian patients with MGs and to estimate the serum level of anti-MAG antibodies and its relationship to peripheral nerve dysfunction. Forty patients with MGs were enrolled in the study. Their mean age was 56.65±8.55years. There were 17 males and 23 females. Patients were subjected to complete general and neurological examination, laboratory investigations including serum LDH, β2 microglobulin, serum protein electrophoresis, urinary Bence-Jones protein, bone marrow aspiration and/or trephine biopsy, quantitative estimation of serum IgM and IgG by nephelometry, detection of anti-MAG antibodies by indirect immunofluorescence, radiological assessment and nerve conduction study of both upper and lower limbs. Clinical and electrophysiological evidences of PN were found in 32 (80%) out of the 40 patients with MG. Twenty-five patients (62.5%) had distal symmetrical polyneuropathy and seven (17.5%) had mononeuritis or mononeuritis multiplex. The majority of patients (65%) had sensory or predominantly sensorimotor polyneuropathy. The neuropathy was mainly demyelinating in 22 patients (55%) and axonal in the other 10 (25%) patients. Anti-MAG antibodies were positive in nine patients (22.5%) and six of them (66.6%) had PN. The latter was predominantly demyelinating motor neuropathy in 4 and axonal in the remaining 2. However, the relationship between the presence of anti-MAG antibodies and the development and type of PN was not statistically significant. Anti-MAG showed significant association with IgM level (P=0.003**) and the MG subtypes: Waldenström's macroglobulinemia (WM) and monoclonal gammopathy of undetermined significance (MGUS) (P=0.004**). The present study showed high frequency (>60%) of distal symmetrical polyneuropathy in Egyptian patients with MG. The neuropathy was predominantly sensory and demyelinating. Anti-MAG antibodies were detected only in 22.5% of the patients, especially those with WM and MGUS and were associated with more motor and demyelinating neuropathy. We recommend that patients with chronic polyneuropathies should be evaluated for underlying plasma cell dyscrasia.

Anti-myelin associated glycoprotein antibodies recognize HNK-1 epitope on CNS

Antibodies to myelin-associated glycoprotein (MAG) are associated with demyelinating polyneuropathy and are specific for the HNK-1 epitope. To test if anti-MAG IgM recognize HNK-1 on CNS, sera from 20 patients and 238 controls were tested on rat slices by indirect immunofluorescence (IIF). IgM from anti-MAG positive patients, but not from control sera, stained rat brain with perineuronal or neuropil pattern, depending on the CNS region. IIF titers significantly correlated with ELISA anti-MAG titers. The staining of patients’ sera were inhibited by mouse anti-HNK-1 monoclonal antibody. Our results demonstrate that anti-MAG IgM recognizes HNK-1 outside the peripheral nerve myelin carriers.

Anti-MAG Neuropathy: a Single Center Retrospective Study In 61 Patients

AbstractAbstract 3951 Background:Polyneuropathy is the most frequent neurological complication in Waldenstrom macroglobulinemia (WM). Most patients have an insidiously progressive distal symmetric sensorimotor and ataxic neuropathy due to a monoclonal immunoglobulin M anti-myelin-associated glycoprotein (MAG). There is still no treatment reference today. Recent studies underline the interest of Rituximab (RTX) but its efficacy is not yet proven. In order to identify the interest of immunotherapy, we performed a retrospective study in 61 patients with anti-MAG over a period of 12 years. Methods:All patients underwent neurological, biological (anti-MAG antibodies, IgM serum) and electrophysiological examination before and after each treatment. Clinically, patients were considered to be improved if they had a decrease of at least two points on the INCAT sensory sum score and/or a decrease of 20 mm on the visual analogue scale and/or motor strength improvement by at least two MRC points in the ankle dorsiflexor. Biologically, response anti-MAG antibodies and IgM serum were considered to be improved if their level was diminished by half. Electrophysiological studies were performed using standard procedures. Results:A total of 61 patients were analyzed. The median age at onset was 64 years (range 33–84), median serum IgM concentration 4.6 g/L (0-17), median anti-MAG antibodies 49900 BTU (23000>70000), RANKIN score 1 (35 patients), 2(20 patients), 3(6 patients). Twenty-five patients had WM with lymphoplasmacytic cells bone marrow infiltration. None of the patients had criteria for therapy initiation according to the 2th international workshop except symptomatic or evolving neuropathy. In first line, 45 patients were treated with Chlorambucil (CBL) (8 improved, 28 were stabilised, 9 worsened), 16 patients were treated with RTX alone (9) or in combination (7) (11 improved, 2 were stabilised, 3 worsened). RTX gave a significant higher response rate compared with CBL (p=2×10-4). With a median follow up of 96 months, 15 patients treated with CBL relapsed. Only one patient treated with RTX relapsed but the median follow up was not reached (60 months follow up). In the CBL group, 15 patients were treated at relapse with RTX and 11 improved, 3 were stabilised, 1 worsened. The average time follow up of the 2nd response was 48 months. Twelve patients in failure were treated with RTX: 8 improved, 1 was stabilised, 3 failed with an average follow up of 48 months. There was no significant difference between anti-MAG antibodies level before and after treatment (p=0.64) in patients in response but a low IgM level was associated with response to treatment (p<0.029). Conclusion:In first line, RTX alone or in combination is associated with a higher response rate than CBL. For patients who relapsed after CHL, patients favourably responded to RTX with an average time follow up of 48 months. IgM level is a prognosis factor (p<0.029) for clinical response to treatment. To better define the efficacy of RTX in this setting, results of a french randomized study comparing RTX to placebo are pending. Disclosures:Choquet:Roche: Consultancy. Leblond:ROCHE: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MUNDIPHARMA: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; GENZYME: Membership on an entity's Board of Directors or advisory committees; CELGENE: Membership on an entity's Board of Directors or advisory committees; JANSSEN: Membership on an entity's Board of Directors or advisory committees.

Antigenic Determinants in IgM Paraprotein-Related Neuropathies

The association of neuropathy with IgM paraprotein has been known for several years, but only recently the pathogenetic relevance of this association has been clarified. Reactivity of the paraprotein with several neural antigens has been reported even if their pathogenetic relevance is not always clear. IgM binding to the Myelin-associated glycoprotein (MAG) is associated with a homogeneous demyelinating neuropathy, deposits of the paraprotein and complement on nerve myelin, and improvement concomitantly to anti-MAG IgM reduction. In particular, treatment with rituximab durably improved the neuropathy in two thirds of the patients, particularly those with moderately increased anti-MAG titres, which might be more easily reduced by this treatment. Several other IgM reactivities with nerve antigens have been reported in these patients, including several gangliosides and sulfatide even if, with the only exceptions of anti-sulfatide and anti-GQ1b ganglioside reactivities, their possible pathogenetic relevance remains to be established.