NMDAR encephalitis: passive transfer from man to mouse by a recombinant antibody

Abstract

ObjectiveAutoimmune encephalitis is most frequently associated with anti‐NMDAR autoantibodies. Their pathogenic relevance has been suggested by passive transfer of patients' cerebrospinal fluid (CSF) in mice in vivo. We aimed to analyze the intrathecal plasma cell repertoire, identify autoantibody‐producing clones, and characterize their antibody signatures in recombinant form.MethodsPatients with recent onset typical anti‐NMDAR encephalitis were subjected to flow cytometry analysis of the peripheral and intrathecal immune response before, during, and after immunotherapy. Recombinant human monoclonal antibodies (rhuMab) were cloned and expressed from matching immunoglobulin heavy‐ (IgH) and light‐chain (IgL) amplicons of clonally expanded intrathecal plasma cells (cePc) and tested for their pathogenic relevance.ResultsIntrathecal accumulation of B and plasma cells corresponded to the clinical course. The presence of cePc with hypermutated antigen receptors indicated an antigen‐driven intrathecal immune response. Consistently, a single recombinant human GluN1‐specific monoclonal antibody, rebuilt from intrathecal cePc, was sufficient to reproduce NMDAR epitope specificity in vitro. After intraventricular infusion in mice, it accumulated in the hippocampus, decreased synaptic NMDAR density, and caused severe reversible memory impairment, a key pathogenic feature of the human disease, in vivo.InterpretationA CNS‐specific humoral immune response is present in anti‐NMDAR encephalitis specifically targeting the GluN1 subunit of the NMDAR. Using reverse genetics, we recovered the typical intrathecal antibody signature in recombinant form, and proved its pathogenic relevance by passive transfer of disease symptoms from man to mouse, providing the critical link between intrathecal immune response and the pathogenesis of anti‐NMDAR encephalitis as a humorally mediated autoimmune disease.

NMDA Receptor Autoantibodies in Autoimmune Encephalitis Cause a Subunit-Specific Nanoscale Redistribution of NMDA Receptors

“…Recombinant human monoclonal NMDAR autoantibodies derived from patients’ plasma cells had the same effects as those reported for patients’ CSF antibodies (Malviya et al, 2017), indicating that the observed effects were caused by the antibodies, not by other CSF factors. Moreover, autoantibody-derived F(ab) (antigen binding) fragments did not decrease surface receptor density (Moscato et al, 2014), indicating that the cross-linking and internalization of NMDAR required the two arms of the antibody molecule and were not due to the labeling procedure.…”

Human Cerebrospinal Fluid Monoclonal LGI1 Autoantibodies Increase Neuronal Excitability

“…Prior to recording, slices were transferred to a submerged recording chamber (Luigs and Neumann, Ratingen, Germany) and perfused with oxygenated artificial CSF (ACSF; pH 7.4) containing (in mM) NaCl (119), NaHCO 3 , glucose , KCl (2.5), NaH 2 PO 4 (1.25), MgCl 2 (4.0), and CaCl 2 (4.0) at room temperature, with a perfusion rate of 5ml/min. Excitability of the cells was measured in current clamp mode with a K‐gluconate–based intracellular solution containing (in mM) K‐gluconate (120), Hepes , KCl , NaCl , MgATP , NaGTP (0.3), and phosphocreatine , adjusted to pH 7.3 with KOH.…”

“…Although immunosuppression is effective in 50 to 80% of patients with LGI1 encephalitis, detailed insight into the composition of the humoral autoimmune response to LGI1 in the CSF and the role of single LGI1 antibodies is missing. As exemplified by recent studies of N‐methyl‐D‐aspartate (NMDA) receptor encephalitis, sequencing and expression of monoclonal antibodies from patient samples allow a deeper understanding of autoimmune encephalopathies . Here, we amplified and cloned variable heavy and light chain sequences from CSF‐derived antibody‐secreting cells (ASCs) and B cells of 3 patients with LGI1 encephalitis.…”

“…As exemplified by recent studies of Nmethyl-D-aspartate (NMDA) receptor encephalitis, sequencing and expression of monoclonal antibodies from patient samples allow a deeper understanding of autoimmune encephalopathies. 25,26 Here, we amplified and cloned variable heavy and light chain sequences from CSF-derived antibody-secreting cells (ASCs) and B cells of 3 patients with LGI1 encephalitis. We expressed 85 monoclonal recombinant antibodies and characterized their reactivities and antigen-binding sites.…”

Human gestational N‐methyl‐d‐aspartate receptor autoantibodies impair neonatal murine brain function

“…Maternal immune activation including such ABs may therefore influence the etiology of neurodevelopmental disorders, including autism spectrum disorders (ASD), learning disabilities, and schizophrenia. [14][15][16] Third, during fetal brain development, NMDARs are crucial for proper axonal 17 and dendritic growth, 18 neuronal survival, 19 and glutamatergic synaptic transmission at early stages. 9,10 So far, little is known about maternal ABs against the NR1 (GluN1) subunit of the Nmethyl-D-aspartate receptor (NMDAR), although it is among the most frequent anti-neuronal ABs in clinically asymptomatic individuals, with an IgG seroprevalence of 1%.…”