OBJECTIVE:To evaluate the presence of IgM and IgG antibodies in the serum of patients with chronic idiopathic axonal polyneuropathy (CIAP) and gluten neuropathy (GN) using a newly developed microarray technique. METHODS:Sera from 42 CIAP patients, 32 GN patients, and 79 healthy controls were tested for IgM and IgG antibodies against 16 single glycolipids and their 120 heteromeric complexes. Positivity rates were analyzed using the 95th percentile from controls. RESULTS:IgM positivity against 8 heteromeric complexes was more frequent in CIAP patients (16.7% to 28.6%) compared to controls, while GN patients showed higher rates (18.8% to 46.9%) across 15 complexes. GN patients had a higher rate of IgM positivity against the GM2:GT1b complex than CIAP patients (46.9% vs. 21.4%). IgG antibodies against seven antigens were also more prevalent in CIAP (16.7% to 26.2%) and GN patients (18.8% to 28.1%) than controls. GN patients showed a higher rate of IgG positivity against the GM1:Sulfatide complex than CIAP patients (15.6% vs. 0%). CONCLUSIONS:This is the first study to report increased antibody detection rates against peripheral nerve glycolipids, both individually and in complexes. The findings suggest that a significant proportion of CIAP and GN patients may have an autoimmune pathogenesis, potentially targetable by immunotherapy.

BACKGROUND:Zika produced the highest increase in the incidence of Guillain-Barré syndrome (GBS) in Latin America in the last decade. The Neuroinfections Emerging in the Americas Study (NEAS) was established in 2016 to investigate the association of emerging infectious disorders with GBS in Colombia. The present study assessed the role of preceding infections, including arboviruses and other pathogens, as risk factors for GBS. METHODS:A case-control study was conducted prospectively between June 2016 and December 2019 in 5 Colombian cities. We recruited newly diagnosed patients with GBS and a house control plus an age and season-matched-hospital control per case. Clinical information, blood, CSF, and urine samples were used to diagnose bacterial and viral infections. Anti-glycolipid antibodies were identified in serum. Statistical analyses were performed using conditional logistic regression. FINDINGS:Fifty-seven patients with GBS, 66·7% male, 52 years of median age, were recruited along with 77 (55 house and 22 hospital) controls. GBS was associated with presenting diarrhea (adjusted OR 10·94; 95% CI 1·8-66·29; p=0·009) and a history of recent upper respiratory tract infection (aOR 13·91; 95% CI 2·38-81·1 p=0·003). Specific recent infections did not significantly differ between cases and controls, but the number of infections was associated with GBS (aOR=1·77 95% CI 1·04-3·01 p=0·03). C. jejuni (74%), M. pneumoniae (23%), and Chikungunya (7%) were the most frequent infections. Anti-glycolipid IgG against GM1 and their heterodimer complexes were identified to be associated with GBS. CONCLUSIONS:After the Zika epidemic, infections causing diarrhea and upper respiratory diseases contributed to the burden of GBS in Colombia. Prevention and control of food-borne pathogens could reduce the incidence of GBS in Colombia.

ABSTRACT Background and Aims Reliable detection of antibodies against nodal targets is vital for the diagnosis of autoimmune nodopathies. The performance characteristics of recently developed in‐house assays are unknown. We compared testing at four centres. Methods Each submitted 29–40 serum samples to a coordinating centre from one of three groups: (1) autoimmune nodopathy patients, with positive nodal/paranodal antibodies; (2) seronegative patients with other inflammatory neuropathies, and (3) healthy individuals or those with other neurological diseases. The coordinating centre recoded all samples and returned 160 identical aliquots to each testing centre for blinded testing. Once data from all centres had been received by the coordinating centre, unblinded results were returned for analysis. Sensitivity was defined by the proportion of group 1 samples returned as positive. Accuracy was defined as 0.075(sensitivity) + 0.925(specificity). Results Centres performed various combinations of ELISA, cell‐based (CBAs) and teased‐nerve fibre assays. All labs produced highly accurate results (96%–100%) and concordance for the overall result across at least 3 or all 4 test centres was observed for 98% and 89% of the samples respectively. However, 10/30 individual assays (6/14 CBAs and 4/16 ELISAs) were less than 90% sensitive. Only 3 assays had more than 1 false positive result (2 ELISAs and 1 CBA). Combining different assay modalities to produce an overall result did not improve accuracy. Inter‐laboratory consistency in the determination of antibody subclasses was poor. Interpretation Although most samples were correctly categorised in all 4 centres, the use of a specific test modality or multiple tests did not guarantee accuracy. Early and repeated interlaboratory testing with sharing of samples is important to understand test performance and reproducibility, identify areas for improvement and maintain consistency. To aid this, we provide detailed methods for the best performing tests. Further standardisation of antibody subclass determination is required.

The neuromuscular junction (NMJ) is a highly reliable synapse to carry the control of the motor commands of the nervous system over the muscles. Its development, organization, and synaptic properties are highly structured and regulated to support such reliability and efficacy. Yet, the NMJ is also highly plastic, able to react to injury, and able to adapt to changes. This balance between structural stability and synaptic efficacy on one hand and structural plasticity and repair on another hand is made possible by perisynaptic Schwann cells (PSCs), glial cells at this synapse. They regulate synaptic efficacy and structural plasticity of the NMJ in a dynamic, bidirectional manner owing to their ability to decode synaptic transmission and by their interactions with trophic-related factors. Alteration of these fundamental roles of PSCs is also important in the maladapted response of NMJs in various diseases and in aging.

Guillain-Barré syndrome is an acute polyradiculoneuropathy in which preceding infections often elicit the production of antibodies that target peripheral nerve antigens, principally gangliosides. Anti-ganglioside antibodies are thought to play a key role in the clinical diversity of the disease and can be helpful in clinical practice. Extensive research into clinical associations of individual anti-ganglioside antibody specificities has been performed. Recent research has highlighted glycolipid complexes, glycolipid combinations that may alter antibody binding, as targets. In this study, we investigated antibody reactivity patterns to glycolipids and glycolipid complexes using combinatorial array, in relation to clinical features in Guillain-Barré syndrome. In total, 1413 patients from the observational International Guillain-Barré syndrome Outcome Study (0-91 years, 60.3% male) and 1061 controls (healthy, family, infectious, vaccination, other neurological disease) were included. Acute-phase sera from patients were screened for IgM, IgG, and IgA reactivity against 15 glycolipids and one phospholipid and their heteromeric complexes, similarly to archived control sera. Antibody specificities and reactivity patterns were analysed in relation to clinical features. Of all patients, 1309 (92.6%) were positive for at least one anti-glycolipid (complex) antibody. Anti-GM1 and anti-GQ1b (complex) antibodies best distinguished motor Guillain-Barré syndrome and Miller Fisher syndrome from controls, with antibodies to glycolipid complexes outperforming antibodies to single glycolipids. Three models consisting of anti-glycolipid (complex) antibodies distinguished patients with Guillain-Barré syndrome, the motor variant, and Miller Fisher syndrome from controls with high sensitivity and specificity, performing better than antibodies to single glycolipids used in clinical practice. Seven patient clusters with particular antibody reactivity patterns were identified. These clusters were distinguished by geographical region, clinical variants, preceding Campylobacter jejuni infection, electrophysiological subtypes, the Medical Research Council sum score at study entry, and the ability to walk 10 m unaided at 26 weeks. Two patient clusters with distinct anti-GM1 (complex) reactivity (broad versus restricted) differed in frequency of the axonal subtype. In cumulative incidence analyses, 15 anti-glycolipid (complex) antibodies were associated with the time required to regain the ability to walk 10 m unaided. After adjustment for known prognostic factors, IgG anti-GQ1b:GM4, GQ1b:PS and GQ1b:Sulfatide remained associated with faster recovery. Addition of anti-glycolipid antibodies to clinical prognostic models slightly improved their discriminative capacity, though insufficiently to improve the models. Measurement of anti-glycolipid antibodies by combinatorial array increases the diagnostic yield compared to assaying single glycolipids, identifies clinically relevant antibody reactivity patterns to glycolipids and glycolipid complexes, and may be useful in outcome prediction in Guillain-Barré syndrome.

Triple-negative breast cancer (TNBC), which constitutes 10–20 percent of all breast cancers, is aggressive, has high metastatic potential, and carries a poor prognosis due to limited treatment options. LT-IIc, a member of the type II subfamily of ADP-ribosylating—heat-labile enterotoxins that bind to a distinctive set of cell-surface ganglioside receptors—is cytotoxic toward TNBC cell lines, but has no cytotoxic activity for non-transformed breast epithelial cells. Here, primary TNBC cells, isolated from resected human tumors, showed an enhanced cytotoxic response specifically toward LT-IIc, in contrast to other enterotoxins that were tested. MDA-MB-231 cells, a model for TNBC, were used to evaluate potential mechanisms of cytotoxicity by LT-IIc, which induced elevated intracellular cAMP and stimulated the cAMP response element-binding protein (CREB) signaling pathway. To dissect the role of ADP-ribosylation, cAMP induction, and ganglioside ligation in the cytotoxic response, MDA-MB-231 cells were exposed to wild-type LT-IIc, the recombinant B-pentamer of LT-IIc that lacks the ADP-ribosylating A polypeptide, or mutants of LT-IIc with an enzymatically inactivated A1-domain. These experiments revealed that the ADP-ribosyltransferase activity of LT-IIc was nonessential for inducing the lethality of MDA-MB-231 cells. In contrast, a mutant LT-IIc with an altered ganglioside binding activity failed to trigger a cytotoxic response in MDA-MB-231 cells. Furthermore, the pharmacological inhibition of ganglioside expression protected MDA-MB-231 cells from the cytotoxic effects of LT-IIc. These data establish that ganglioside ligation, but not the induction of cAMP production nor ADP-ribosyltransferase activity, is essential to initiating the LT-IIc-dependent cell death of MDA-MB-231 cells. These experiments unveiled previously unknown properties of LT-IIc and gangliosides in signal transduction, offering the potential for the targeted treatment of TNBC, an option that is desperately needed.

Importance The temporal association between the occurrence of neurological diseases, many autoimmune diseases, and vaccination against SARS-CoV-2 has been topically interesting and remains hotly debated both in the medical literature and the clinic. Given the very low incidences of these events both naturally occurring and in relation to vaccination, it is challenging to determine with certainty whether there is any causative association and most certainly what the pathophysiology of that causation could be. Observations Data from international cohorts including millions of vaccinated individuals suggest that there is a probable association between the adenovirus-vectored vaccines and Guillain-Barré syndrome (GBS). Further associations between other SARS-CoV-2 vaccines and GBS or Bell palsy have not been clearly demonstrated in large cohort studies, but the possible rare occurrence of Bell palsy following messenger RNA vaccination is a topic of interest. It is also yet to be clearly demonstrated that any other neurological diseases, such as central nervous system demyelinating disease or myasthenia gravis, have any causative association with vaccination against SARS-CoV-2 using any vaccine type, although it is possible that vaccination may rarely trigger a relapse or worsen symptoms or first presentation in already-diagnosed or susceptible individuals. Conclusions and Relevance The associated risk between SARS-CoV-2 vaccination and GBS, and possibly Bell palsy, is slight, and this should not change the recommendation for individuals to be vaccinated. The same advice should be given to those with preexisting neurological autoimmune disease.

e17551 Background: Tumor-marker gangliosides (TMGs) have enormous potential for early-stage cancer detection as diagnostic biomarkers despite being relatively understudied in this context. AOA Dx is focused on the analytical development of three separate platforms for the quantitation of TMGs in human serum. The development of these platforms for TMG quantitation may allow for the identification of diagnostic signatures for early-stage cancer detection. Methods: First, we are developing a pipeline of antibody-based assays to target TMGs. To aid in development of multiple immunoassays, we collected specificity and affinity data on commercial and proprietary antibodies targeting TMGs using glycoarrays. We are also currently using two immune-based platforms to target TMGs. We have developed an enzyme-linked immunosorbent assay (ELISA) and we have implemented high-performance thin-layer chromatography (HPTLC) to detect individual and total gangliosides. Additionally, we are applying both targeted and untargeted mass spectrometry to human serum from confirmed cancer diagnoses. Results: The specificity and affinity data from the glycoarrays confirm that our TMG antibodies have negligible cross-reactivity and are suitable for diagnostic platform development. Additionally, our developed ELISA allows for the quantification of TMGs in diverse and complex matrices including human serum and plasma, cell lines, and exosomes. HPTLC also detects individual and total gangliosides in each of these matrices, which allows for high-throughput analysis for TMG quantitation. Finally, the application of both targeted and untargeted mass spectrometry has identified multiple TMGs characterized by unique lipid tails. Notably, MS analysis shows that the serum of melanoma and ovarian cancer patients exhibited significantly increased levels of several ganglioside species compared to age-matched healthy serum, further highlighting the potential of TMGs as a promising avenue for cancer diagnosis. Further experiments will focus on refining all platforms. We will also expand the demographic representation of our human serum sample cohort to confirm the initial findings from our mass spectrometry experiments and continue to use this platform to identify additional TMGs of interest. Conclusions: AOA Dx is advancing the development of a multi-platform approach for the detection of TMGs. Our objective is the identification of a diagnostic disease signature for early-stage cancer detection. The validation of this type of diagnostic panel would allow for expedited diagnosis and treatment of cancers currently diagnosed at late stages, ultimately reducing healthcare costs and increasing survival rates. Future research will aim to validate these biomarkers in independent prospective studies.

Recent work identified anti-GM2 and anti-GalNAc-GD1a IgG ganglioside antibodies as biomarkers in dogs clinically diagnosed with acute canine polyradiculoneuritis, in turn considered a canine equivalent of Guillain-Barre syndrome. This study aims to investigate the serum prevalence of similar antibodies in cats clinically diagnosed with immune-mediated polyneuropathies. The sera from 41 cats clinically diagnosed with immune-mediated polyneuropathies (IPN), 9 cats with other neurological or neuromuscular disorders (ONM) and 46 neurologically normal cats (CTRL) were examined for the presence of IgG antibodies against glycolipids GM1, GM2, GD1a, GD1b, GalNAc-GD1a, GA1, SGPG, LM1, galactocerebroside and sulphatide. A total of 29/41 IPN-cats had either anti-GM2 or anti-GalNAc-GD1a IgG antibodies, with 24/29 cats having both. Direct comparison of anti-GM2 (sensitivity: 70.7%; specificity: 78.2%) and anti-GalNAc-GD1a (sensitivity: 70.7%; specificity: 70.9%) antibodies narrowly showed anti-GM2 IgG antibodies to be the better marker for identifying IPN-cats when compared to the combined ONM and CTRL groups (P = .049). Anti-GA1 and/or anti-sulphatide IgG antibodies were ubiquitously present across all sample groups, whereas antibodies against GM1, GD1a, GD1b, SGPG, LM1 and galactocerebroside were overall only rarely observed. Anti-GM2 and anti-GalNAc-GD1a IgG antibodies may serve as serum biomarkers for immune-mediated polyneuropathies in cats, as previously observed in dogs and humans.

Leonhard et al. analyzed the pattern of preceding infections in a large cohort of 768 patients with Guillain-Barré syndrome (GBS) from 19 countries spread over 5 continents.1 To some extent, this study is biased because the majority of the patients were from temperate regions and testing for preceding infections was limited to only 5 microorganisms ( Campylobacter jejuni , hepatitis E virus, Mycoplasma pneumoniae , cytomegalovirus, and Epstein-Barr virus). The burden of infections varies significantly across tropical and temperate regions, with arboviral infections being quite prevalent in the tropics. Dengue, chikungunya, Japanese encephalitis, and zika have consistently been associated with GBS.2-4

Background and Objectives Recent outbreaks of Zika virus (ZIKV) in South and Central America have highlighted significant neurologic side effects. Concurrence with the inflammatory neuropathy Guillain-Barré syndrome (GBS) is observed in 1:4,000 ZIKV cases. Whether the neurologic symptoms of ZIKV infection are immune mediated is unclear. We used rodent and human live cellular models to screen for anti-peripheral nerve reactive IgG and IgM autoantibodies in the sera of patients with ZIKV with and without GBS. Methods In this study, 52 patients with ZIKV-GBS were compared with 134 ZIKV-infected patients without GBS and 91 non-ZIKV controls. Positive sera were taken forward for target identification by immunoprecipitation and mass spectrometry, and candidate antigens were validated by ELISA and cell-based assays. Autoantibody reactions against glycolipid antigens were also screened on an array. Results Overall, IgG antibody reactivities to rat Schwann cells (SCs) (6.5%) and myelinated cocultures (9.6%) were significantly higher, albeit infrequent, in the ZIKV-GBS group compared with all controls. IgM antibody immunoreactivity to dorsal root ganglia neurones (32.3%) and SCs (19.4%) was more frequently observed in the ZIKV-GBS group compared with other controls, whereas IgM reactivity to cocultures was as common in ZIKV and non-ZIKV sera. Strong axonal-binding ZIKV-GBS serum IgG antibodies from 1 patient were confirmed to react with neurofascin 155 and 186. Serum from a ZIKV-infected patient without GBS displayed strong myelin-binding and putative antilipid antigen reaction characteristics. There was, however, no significant association of ZIKV-GBS with any known antiglycolipid antibodies. Discussion Autoantibody responses in ZIKV-GBS target heterogeneous peripheral nerve antigens suggesting heterogeneity of the humoral immune response despite a common prodromal infection.

Axon degeneration accounts for the poor clinical outcome in Guillain‐Barré syndrome (GBS), yet no treatments target this key pathogenic stage. Animal models demonstrate anti‐ganglioside antibodies (AGAb) induce axolemmal complement pore formation through which calcium flux activates the intra‐axonal calcium‐dependent proteases, calpains. We previously showed protection of axonal components using soluble calpain inhibitors in ex vivo GBS mouse models, and herein, we assess the potential of axonally‐restricted calpain inhibition as a neuroprotective therapy operating in vivo. Using transgenic mice that over‐express the endogenous human calpain inhibitor calpastatin ( hCAST ) neuronally, we assessed distal motor nerve integrity in our established GBS models. We induced immune‐mediated injury with monoclonal AGAb plus a source of human complement. The calpain substrates neurofilament and AnkyrinG, nerve structural proteins, were assessed by immunolabelling and in the case of neurofilament, by single‐molecule arrays (Simoa). As the distal intramuscular portion of the phrenic nerve is prominently targeted in our in vivo model, respiratory function was assessed by whole‐body plethysmography as the functional output in the acute and extended models. hCAST expression protects distal nerve structural integrity both ex and in vivo, as shown by attenuation of neurofilament breakdown by immunolabelling and Simoa. In an extended in vivo model, while mice still initially undergo respiratory distress owing to acute conduction failure, the recovery phase was accelerated by hCAST expression. Axonal calpain inhibition can protect the axonal integrity of the nerve in an in vivo GBS paradigm and hasten recovery. These studies reinforce the strong justification for developing further animal and human clinical studies using exogenous calpain inhibitors.

The major determinant of poor outcome in Guillain‐Barré syndrome (GBS) is axonal degeneration. Pathways leading to primary axonal injury in the motor axonal variant are well established, whereas mechanisms of secondary axonal injury in acute inflammatory demyelinating polyneuropathy (AIDP) are unknown. We recently developed an autoantibody‐and complement‐mediated model of murine AIDP, in which prominent injury to glial membranes at the node of Ranvier results in severe disruption to paranodal components. Acutely, axonal integrity was maintained, but over time secondary axonal degeneration occurred. Herein, we describe the differential mechanisms underlying acute glial membrane injury and secondary axonal injury in this model. Ex vivo nerve‐muscle explants were injured for either acute or extended periods with an autoantibody‐and complement‐mediated injury to glial paranodal membranes. This model was used to test several possible mechanisms of axon degeneration including calpain activation, and to monitor live axonal calcium signalling. Glial calpains induced acute disruption of paranodal membrane proteins in the absence of discernible axonal injury. Over time, we observed progressive axonal degeneration which was markedly attenuated by axon‐specific calpain inhibition. Injury was unaffected by all other tested methods of protection. Trans‐axolemmal diffusion of fluorescent proteins and live calcium imaging studies indirectly demonstrated the presence of nanoruptures in the axon membrane. This study outlines one mechanism by which secondary axonal degeneration arises in the AIDP variant of GBS where acute paranodal loop injury is prominent. The data also support the development of calpain inhibitors to attenuate both primary and secondary axonal degeneration in GBS.

AbstractThe involvement of the complement pathway in Guillain–Barré syndrome pathogenesis has been demonstrated in both patient biosamples and animal models. One proposed mechanism is that anti-ganglioside antibodies mediate neural membrane injury through the activation of complement and the formation of membrane attack complex pores, thereby allowing the uncontrolled influx of ions, including calcium, intracellularly. Calcium influx activates the calcium-dependent protease calpain, leading to the cleavage of neural cytoskeletal and transmembrane proteins and contributing to subsequent functional failure. Complement inhibition has been demonstrated to provide effective protection from injury in anti-ganglioside antibody-mediated mouse models of axonal variants of Guillain–Barré syndrome; however, the role of complement in the pathogenesis of demyelinating variants has yet to be established. Thus, it is currently unknown whether complement inhibition would be an effective therapeutic for Guillain–Barré syndrome patients with injuries to the Schwann cell membrane. To address this, we recently developed a mouse model whereby the Schwann cell membrane was selectively targeted with an anti-GM1 antibody resulting in significant disruption to the axo-glial junction and cytoplasmic paranodal loops, presenting as conduction block. Herein, we utilize this Schwann cell nodal membrane injury model to determine the relevance of inhibiting complement activation. We addressed the early complement component C2 as the therapeutic target within the complement cascade by using the anti-C2 humanized monoclonal antibody, ARGX-117. This anti-C2 antibody blocks the formation of C3 convertase, specifically inhibiting the classical and lectin complement pathways and preventing the production of downstream harmful anaphylatoxins (C3a and C5a) and membrane attack complexes. Here, we demonstrate that C2 inhibition significantly attenuates injury to paranodal proteins at the node of Ranvier and improves respiratory function in ex vivo and in vivo Schwann cell nodal membrane injury models. In parallel studies, C2 inhibition also protects axonal integrity in our well-established model of acute motor axonal neuropathy mediated by both mouse and human anti-GM1 antibodies. These data demonstrate that complement inhibition prevents injury in a Schwann cell nodal membrane injury model, which is representative of neuropathies associated with anti-GM1 antibodies, including Guillain–Barré syndrome and multifocal motor neuropathy. This outcome suggests that both the motor axonal and demyelinating variants of Guillain–Barré syndrome should be included in future complement inhibition clinical trials.

Glycolipids cluster in plasma membranes to form heterogenous patches. Whereas lectins and antibodies have been conventionally viewed as binding a single oligosaccharide head group, and assayed accordingly, it is increasingly evident that cis-interactions between glycan headgroups may form unique molecular shapes that either enhance or attenuate binding of antibodies and other proteins. Herein we describe a method for assaying antibody binding to heteromeric glycolipid complexes that allows rapid, simple, inexpensive and high-throughput assessment of binding events, focusing on autoantibodies present in human serum.