Fryer, James P.

ABSTRACT Objective We sought to characterize the sixth most common finding in our neuroimmunological laboratory practice (tissue assay‐observed unclassified neural antibodies [UNAs]), combining protein microarray and phage immunoprecipitation sequencing (PhIP‐Seq). Methods Patient specimens (258; 133 serums; 125 CSF) meeting UNA criteria were profiled; October 2022–September 2023. Top‐ranking candidate antigens were validated in silico, by dual‐staining confocal microscopy, and ≥ 1 protein‐specific assay. Clinical data were reviewed. Results Among 21 patients, 11 autoantibodies were characterized (serum, 19; CSF, all 9 available). Autoantigens were CACNA1I, 1; CAMK2B, 2; CLIP2, 1; FMN2, 2; MAP1A, 2; MAP2, 5; NECAB1, 1; SNAP91, 3; SRCIN1, 1; SYNJ1, 1; SYT3, 2. Analytical validation was by confocal TIIFA (all), western blot (10/10 available), and cell‐based assay (5/5 performed). Clinical accompaniments were: encephalitis, 6; brainstem encephalitis, 2; encephalomyelitis, 2; cerebellar ataxia, 2; longitudinally extensive transverse myelitis (LETM), 2; sensory neuronopathy, 1; peripheral neuropathy, 4, and movement disorders, 2. Inflammatory MRI abnormalities were identified in 5/16 patients (31%) with CNS disorders: T2 signal change (2), LETM (2), leptomeningeal enhancement (1). Seven of 8 (88%) had inflammatory CSF (pleocytosis, 5 [median 25.5 cells, range 7–294]; elevated IgG index/synthesis rate, 4; CSF‐exclusive oligoclonal bands, 4). Six had paraneoplastic causation (lung cancer, 2; other, 4); 3 were postinfectious (1 each of COVID‐19, HSV‐1, and post‐Group A streptococcal infection). Of 9 immunotherapy‐treated patients, 5 improved. Interpretation UNAs are partly accounted for by a repertoire of diverse mostly intracellular synaptic antigens. Their characterization is expedited by protein arrays and PhIPSeq. Further individual studies are needed to assess them as disease biomarkers.

Abstract Background To develop and validate a sensitive live cell-binding assay using flow cytometry to detect a3ß4-ganglionic nicotinic acetylcholine receptor (gnAChR) antibodies for diagnosis of autoimmune autonomic ganglionopathy (AAG, a subset of autoimmune autonomic neuropathies). The current radioimmunoprecipitation assay (RIPA) method has high false positive rate and utilizes radioactivity. Methods HEK293 cells were transiently transfected to express human a3ß4-gnAChR subunits, along with NACHO and RIC3 chaperons, and GFP for detection. Transfected cells were treated with 1mM nicotine liquid for 18-22 hours prior to lifting cells for flow cytometry. The IBI (IgG Binding Index) was then calculated as the median fluorescence intensity (MFI) of AF647 of the a3ß4-gnAChR subunits expressing cells divided by the MFI of the AF647 HEK293 expressing cells. Humanized AChR-specific monoclonal antibody (mAb03) was used as a single-point calibrator. The cut-off index (COI) ratio is calculated by dividing the IBI obtained from a sample by the established IBI cut-off value of the mAB03 calibrator set by the assay. A ratio >1 indicates a positive result, while a ratio below 1 is negative. The study tested sera from 83 Mayo Clinic patients suspected of having autoimmune autonomic ganglionopathy (AAG), with a total of 100 samples collected over several years (40 from patients with clinically confirmed AAG, and 60 from patients without AAG), all previously positive for a3-gnAChR antibodies by RIPA. Additionally, 130 control samples were included: 90 from healthy individuals, 22 with hypergammaglobulinemia, and 18 with systemic lupus erythematosus. Results Median RIPA a3ß4-gnAChR value among 40 AAG patient samples was 2.58 nmol/L (range, 0.06-29.1 nmol/L) and among 60 non-AAG patients was 0.14 nmol/L (range, 0.01-4.43 nmol/L). The mAB03 calibrator median IBI value across assays was 2.1 (range, 1.6-2.7). The COI ratio was calculated using the calibrated IBI values. Thirty-eight of 40 AAG patient samples were considered positive, resulting in median IBI of 3.10 (range, 1.29-6.71); sensitivity 95%. None of non-AAG patients and controls were considered positive; median IBI of 0.38 (range, 0.14-0.51); specificity 100%. The two negative AAG patient samples (IBI, 0.43 and 0.43) were from patients in remission (treated with immune suppressants), and had RIPA titers of 0.06 nmol/L and 0.74 nmol/L. Conclusion The a3ß4-gnAChR-IgG flow cytometry assay has high sensitivity and specificity for AAG-related a3-AChR antibodies. It was able to distinguish AAG patients from non-AAG patients and controls effectively. The flow cytometry assay’s cut-off index ratio effectively identifies AAG patients while remaining negative for non-AAG and control samples.

Abstract Objectives γ‐Aminobutyric acid B receptor (GABA B R)‐IgG (immunoglobulin G) is an intermediate‐risk paraneoplastic autoantibody often associated with seizures. We aimed to assess the clinical and oncological features of GABA B R‐IgG autoimmune encephalitis (AE) and evaluate the performance of antibody testing. Methods Patients testing positive for GABA B R‐IgG in serum/cerebrospinal fluid (CSF) at Mayo Clinic Neuroimmunology Laboratory were identified. Archived sera were retested by cell‐based assay (CBA) at 1:100 and 1:200 dilutions. A live‐cell flow cytometry–based assay (LCFBA) was developed and validated using archived sera and CSF. True positivity included patients with classic presentations of GABA B R‐IgG AE or oncological explanations for antibody presence. Results Eighty‐six patients (median age 63 years; 43 female) presented with classic presentations of GABA B R‐IgG AE: encephalopathy with prominent seizures ( n = 55), status epilepticus ( n = 23), and rapidly progressive dementia ( n = 8). In addition, 44 patients (33%) had a false‐positive result for GABA B R‐IgG characterized by non‐specific symptoms/alternate diagnoses. Malignancy was identified in 78% of true‐positive patients, predominantly small cell lung carcinoma (SCLC). Testing serum at 1:100 dilution on CBA and using tissue immunofluorescence assay (IFA) in serum and CSF improved the identification of true‐positive patients ( p < 0.001). CBA at 1:100 dilution performed better than conventional CBA (at 1:10 dilution, p < 0.001) and tissue IFA ( p = 0.031). An in‐house LCFBA showed 100% sensitivity and specificity in CSF, performing similarly to conventional CBA ( p = 0.125) in CSF, but better than tissue IFA ( p = 0.031). Furthermore, serum LCFBA performed better than conventional CBA ( p = 0.022) and tissue IFA ( p = 0.006). LCFBA had the highest diagnostic accuracy and was closely followed by CBA at 1:100 dilution. Significance GABA B R‐IgG AE often presents as encephalopathy with seizures or status epilepticus in the context of an underlying SCLC. Multimodal evaluation using tissue IFA and fixed CBA at higher dilutions improves detection of true cases. LCFBA performs very well as a diagnostic test with very high sensitivity and specificity.

This case series examines long-term outcomes for 2 aquaporin-4-IgG (AQP4-IgG)–positive patients with neuromyelitis optica spectrum disorder (NMOSD) who underwent autologous hematopoietic stem cell transplantation with a nonmyeloablative conditioning regimen and rituximab.

AbstractObjectiveThis study aimed to evaluate the diagnostic accuracy of dried blood spot (DBS) compared with conventional serum Aquaporin‐4‐IgG (AQP4‐IgG) testing.MethodsProspective multicenter diagnostic study was conducted between April 2018 and October 2023 across medical centers in the United States, Uganda, and the Republic of Guinea. Neuromyelitis optica spectrum disorder (NMOSD) patients and controls collected blood on filter paper cards along with concurrent serum samples. These samples underwent analysis using flow cytometric live‐cell‐based assays (CBA) and enzyme‐linked immunosorbent assay (ELISA) to determine AQP4 serostatus. The accuracy of AQP4‐IgG detection between DBS and serum (gold standard) was compared.ResultsAmong 150 participants (47 cases, 103 controls), there was a strong correlation between DBS and serum samples (Spearman's correlation coefficient of 0.82). The AUC was 0.97 (95% CI: 0.92–0.99). AQP4‐IgG detection through DBS showed 87.0% sensitivity (95% CI: 0.74–0.95) and 100% specificity (95% CI: 0.96–1.00) using CBA, and 65.2% sensitivity (95% CI: 0.43–0.84) and 95.2% specificity (95% CI: 0.76–0.99) using ELISA. Serum ELISA demonstrated 69.6% sensitivity (95% CI: 0.47–0.87) and 98.4% specificity (95% CI: 0.91–0.99). The stability of DBS in detecting AQP4‐IgG persisted over 24 months for most cases.InterpretationThe DBS represents a viable alternative for detecting AQP4‐IgG in resource‐limited settings to diagnose NMOSD, offering high sensitivity and specificity comparable to serum testing. Moreover, DBS has low shipping costs, is easy to administer, and is suitable for point‐of‐care testing.

ObjectiveTo evaluate the cerebrospinal fluid (CSF) cytokine/chemokine profile of central nervous system (CNS) neurosarcoidosis (NS), and its utility in differential diagnosis, treatment, and prognostication.MethodsIn this case–control study, we validated 17 cytokines/chemokines (interleukin [IL]‐1‐beta, IL‐2, IL‐4, IL‐5, IL‐6, IL‐10, IL‐12p70, IL‐13, IL‐17A, BAFF, IL‐8/CXCL8, CXCL9, CXCL10, CXCL13, GM‐CSF, interferon‐gamma, and tumor necrosis factor [TNF]‐alpha) in a multiplexed automated immunoassay system (ELLA; Bio‐Techne, Minneapolis, MN, USA), and assessed them in CSF and serum of symptomatic patients with probable or definite CNS NS (01/2011–02/2023) with gadolinium enhancement and/or CSF pleocytosis. Patients with multiple sclerosis, primary CNS lymphoma, aquaporin‐4 immunoglobulin G positivity, non‐inflammatory disorders, and healthy individuals were used as controls.ResultsA total of 32 NS patients (59% women; median age, 59 years [19–81]) were included; concurrent sera were available in 12. CSF controls consisted of 26 multiple sclerosis, 8 primary CNS lymphoma, 84 aquaporin‐4 immunoglobulin G positive, and 34 patients with non‐inflammatory disorders. Gadolinium enhancement was present in 31 of 32 NS patients, and CSF pleocytosis in 27 of 32 (84%). CSF IL‐2, IL‐6, IL‐10, IL‐13, BAFF, IL‐8/CXCL8, CXCL9, CXCL10, CXCL13, GM‐CSF, interferon‐gamma, and TNF‐alpha levels were significantly higher in NS patients compared with non‐inflammatory controls (p ≤ 0.02); elevations were more common in CSF than serum. Concurrent elevation of IL‐6, CXCL9, CXCL10, GM‐CSF, interferon‐gamma, and TNF‐alpha was present in 18 of 32 NS patients, but only in 1 control. Elevated IL‐6, IL‐10, IL‐13, CXCL9, CXL10, GM‐CSF, and TNF‐alpha associated with measures of disease activity.InterpretationNS CSF cytokine/chemokine profiles suggest T cell (mainly T helper cell type 1), macrophage, and B‐cell involvement. These signatures aid in NS diagnosis, indicate disease activity, and suggest therapeutic avenues. ANN NEUROL 2024;96:704–714

Objective The aim of this study was to assess the diagnostic utility of cerebrospinal fluid (CSF) myelin oligodendrocyte glycoprotein antibodies (MOG‐IgG) testing. Methods We retrospectively identified patients for CSF MOG‐IgG testing from January 1, 1996, to May 1, 2023, at Mayo Clinic and other medical centers that sent CSF MOG‐IgG for testing including: controls, 282; serum MOG‐IgG positive MOG antibody‐associated disease (MOGAD), 74; serum MOG‐IgG negative high‐risk phenotypes, 73; serum false positive MOG‐IgG with alternative diagnoses, 18. A live cell‐based assay assessed CSF MOG‐IgG positivity (IgG‐binding‐index [IBI], ≥2.5) using multiple anti‐human secondary antibodies and end‐titers were calculated if sufficient sample volume. Correlation of CSF MOG‐IgG IBI and titer was assessed. Results The pan‐IgG Fc‐specific secondary was optimal, yielding CSF MOG‐IgG sensitivity of 90% and specificity of 98% (Youden's index 0.88). CSF MOG‐IgG was positive in: 4/282 (1.4%) controls; 66/74 (89%) serum MOG‐IgG positive MOGAD patients; and 9/73 (12%) serum MOG‐IgG negative patients with high‐risk phenotypes. Serum negative but CSF positive MOG‐IgG accounted for 9/83 (11%) MOGAD patients, and all fulfilled 2023 MOGAD diagnostic criteria. Subgroup analysis of serum MOG‐IgG low‐positives revealed CSF MOG‐IgG positivity more in MOGAD (13/16[81%]) than other diseases with false positive serum MOG‐IgG (3/15[20%]) ( p = 0.01). CSF MOG‐IgG IBI and CSF MOG‐IgG titer (both available in 29 samples) were correlated (Spearman's r = 0.64, p < 0.001). Interpretation CSF MOG‐IgG testing has diagnostic utility in patients with a suspicious phenotype but negative serum MOG‐IgG, and those with low positive serum MOG‐IgG results and diagnostic uncertainty. These findings support a role for CSF MOG‐IgG testing in the appropriate clinical setting. ANN NEUROL 2024;96:34–45