Citations

Abstract Description Background Glutamic acid decarboxylase 65 (GAD65) antibodies are found in patients with stiff-person syndrome (SPS), cerebellar ataxia (CA), epilepsy and type-I diabetes (T1D). Given the intracellular localization of the antigenic target, a direct pathogenic role for GAD65 antibody (GAD65Ab) is unlikely. Methods PBMC-derived dendritic cells (DCs) from GAD65Ab+ patients with SPS (n = 6), epilepsy (n = 4), CA (n = 5), or T1D (n = 4) were pulsed with full-length GAD65 proteins or with 15-mer peptides from GAD65. T cell activation, exhaustion, and cytotoxicity were measured via cytometric bead array, FluoroSpot, flow cytometry, and live cell imaging. Results CD8+ T cells from patients with GAD65Ab-associated neurological disorders (AD) were activated by exposure to DCs pulsed with full-length GAD65 (p < 0.01 vs unstimulated, Mann-Whitney test; n = 16). We found 3 peptides of interest that caused a 10-30% increase in activated CD8+ T cells in GAD65AbAD patients, as assessed by surface CD69+ labeling. Using NetMHCpan4.2, we identified 8 different 9-mer peptides with high predicted affinity for HLA-C*03:03/04 and HLA-C*07:01/02. Two of these peptides showed high binding to HLA-C and subsequently demonstrated tetramer labeling of CD8+ T cells in GAD65AbAD patients. Conclusions We demonstrated that both full-length GAD65 protein and specific GAD peptides activated CD8+ T cells derived from patients with GAD65AbAD, indicating a potential pathogenic role for these effectors in these disorders. Funding Sources Support from Aditxt Immune Health Project (EU CT number: 2023-504798-19-00) and the Center for MS and Autoimmune Neurology in Mayo Clinic. Topic Categories Neuroimmunology (NEUR)

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.

Background: Tremor in multiple sclerosis (MS) is often refractory to medications. Deep brain stimulation (DBS) may help, but possible side effects and disease exacerbation limit its use. Objectives: Evaluate outcomes of DBS for MS-associated tremor. Methods: Retrospective review of 18 patients with MS-associated tremor who underwent DBS, analyzing Expanded Disability Status Scale (EDSS) and Fahn–Tolosa–Marin (FTM) tremor scores. Results: Median age at surgery was 49.5 years (range, 28–75), with postoperative follow-up 2.5 years (range, 0–22). No relapses (0/18) or new lesions (0/8) occurred postoperatively. All had ventral intermediate nucleus leads; other targets were not used in programming. EDSS remained stable (median 6 to 6.25; p = 0.2). FTM scores improved (median 14.5 to 10, p = 0.008). Patients with EDSS 3.5–6 had variable outcomes ( p = 0.02). Conclusions: DBS is a potential treatment for severe MS tremor and did not provoke relapse. Targeting VIM alone may optimize tremor control and maintain magnetic resonance imaging (MRI) access.

This cohort study examines the oncological, neurological, and serological profiles of adult male patients with testicular germ cell tumors and paraneoplastic neurologic syndromes.

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.

Abstract Purpose: Germ cell tumors (GCTs) pose significant diagnostic challenges due to the limited sensitivity and specificity of current tumor markers. Hereby we utilize phage immunoprecipitation sequencing (PhIP-Seq) technique to develop a unique immunosignature panel (iSIGN) with high sensitivity and specificity to improve the diagnosis and differentiation of GCTs. Patients and Methods: Serum samples from patients with confirmed gonadal or extragonadal GCTs and controls were collected from Mayo Clinic repositories. Controls included benign testicular lesions, autoimmune diseases, neurodegenerative disorders, and other cancers. Samples were randomized into development and validation cohorts. PhIP-Seq identified antigen-autoantibody interactions, and enrichment scores were calculated to develop a biomarker panel distinguishing GCT from non-GCT cases. A second biomarker panel was developed to predict seminoma from nonseminoma cases. Results: A total of 427 serum samples were analyzed, including 150 from GCT patients and 277 controls. For our primary model to distinguish GCT cases (GCT-iSIGN), 24 peptides from 16 antigens were identified based on significant differential autoantibody binding enrichment in GCT patients (p &lt; 0.05), ≥2 peptides per antigen, and enrichment scores ≥ 2.5-fold. GCT-iSIGN was highly sensitive (93%) and specific (99%) for identifying GCT cases from controls with an area under curve (AUC) of 0.93 and 9% Unknown Case Rate (UCR). The secondary panel (Sem-iSIGN) included 17 peptides corresponding to 5 unique proteins with high specificity (93%), moderate sensitivity (65%) and AUC of 0.77 to distinguish seminoma from nonseminoma GCT cases. Conclusion: This study demonstrates the potential use of PhIP-Seq to identify unique immunosignature panels that can serve as reliable biomarkers for GCT. These panels address the limitations of traditional markers and other proteomic techniques. This immunosignature model represents a cost-effective, stable, and scalable approach to enhancing GCT diagnosis and management. Citation Format: M Bakri Hammami, Andrew Knight, Haidara Kherbek, Brian Costello, Silvana De Lorenzo, Bradley C. Leibovich, John C. Cheville, Yong Guo, Jessica Sagen, Janet E. Olson, Alicia Algeciras-Schimnich, Sean J. Pittock, John R. Mills, Surendra Dasari, Divyanshu Dubey. iSIGN panel identifies germ cell tumors via whole-proteome phage immunoprecipitation sequencing [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Mechanisms of Cancer Immunity and Cancer-related Autoimmunity; 2025 Sep 24-27; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(9 Suppl):Abstract nr B027.