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.

We performed a genome-wide association study in 1,194 controls and 150 patients with anti-N-methyl-D-aspartate receptor (anti-NMDAR, n = 96) or anti-leucine-rich glioma-inactivated1 (anti-LGI1, n = 54) autoimmune encephalitis. Anti-LGI1 encephalitis was highly associated with 27 single-nucleotide polymorphisms (SNPs) in the HLA-II region (leading SNP rs2858870 p = 1.22 × 10 , OR = 13.66 [7.50-24.87]). Potential associations, below genome-wide significance, were found with rs72961463 close to the doublecortin-like kinase 2 gene (DCLK2) and rs62110161 in a cluster of zinc-finger genes. HLA allele imputation identified association of anti-LGI1 encephalitis with HLA-II haplotypes encompassing DRB1*07:01, DQA1*02:01 and DQB1*02:02 (p < 2.2 × 10 ) and anti-NMDAR encephalitis with HLA-I allele B*07:02 (p = 0.039). No shared genetic risk factors between encephalitides were identified. Ann Neurol 2018;83:863-869.

Objective:It was hypothesized that in encephalitides with autoantibodies directed to CNS surface antigens an antibody-removing intervention might speed up recovery.Methods:The outcome of autoimmune encephalitis in 19 patients with antibodies against surface antigens (leucine-rich, glioma inactivated 1 [LGI1], n = 3; contactin-associated protein-2 [CASPR2], n = 4; NMDA receptor [NMDAR], n = 7) and intracellular antigens (glutamic acid decarboxylase [GAD], n = 5) after immunoadsorption in addition to corticosteroid therapy was evaluated retrospectively. Modified Rankin scale (mRS) scores and data on seizures, memory, and antibody titers directly after immunoadsorption (early follow-up) and after a median of 4 months (late follow-up) were compiled.Results:Immediately after immunoadsorption, 9 of 14 patients with antibodies against LGI1, CASPR2, or NMDAR (64%), but none with GAD antibodies, had improved by at least one mRS point. Five of the 7 patients with LGI1 or CASRP2 antibodies had become seizure-free, and 2 patients with NMDAR antibodies had a memory improvement of more than 1 SD of a normal control population. At late follow-up, 12 of 14 patients with surface antibodies had improved (86%), and none of the patients with GAD antibodies.Conclusions:It is suggested that addition of immunoadsorption to immunosuppression therapy in patients with surface antibodies may accelerate recovery. This supports the pathogenic role of surface antibodies.Classification of evidence:This study provides Class IV evidence that immunoadsorption combined with immunosuppression therapy is effective in patients with autoimmune encephalitis with surface antibodies.

Temporal lobe epilepsy with amygdala enlargement (TLE-AE) is increasingly recognized as a distinct adult electroclinical syndrome. However, functional consequences of morphological alterations of the amygdala in TLE-AE are poorly understood. Here, two emotional stimulation designs were employed to investigate subjective emotional rating and skin conductance responses in a sample of treatment-naïve patients with suspected or confirmed autoimmune TLE-AE (n = 12) in comparison to a healthy control group (n = 16). A subgroup of patients completed follow-up measurements after treatment. As compared to healthy controls, patients with suspected or confirmed autoimmune TLE-AE showed markedly attenuated skin conductance responses and arousal ratings, especially pronounced for anxiety-inducing stimuli. The degree of right amygdala enlargement was significantly correlated with the degree of autonomic arousal attenuation. Furthermore, a decline of amygdala enlargement following prompt aggressive immunotherapy in one patient suffering from severe confirmed autoimmune TLE-AE with a very recent clinical onset was accompanied by a significant improvement of autonomic responses. Findings suggest dual impairments of autonomic and cognitive discrimination of stimulus arousal as hallmarks of emotional processing in TLE-AE. Emotional responses might, at least partially, recover after successful treatment, as implied by first single case data.

Objective: To report on a novel neuronal target antigen in 3 patients with autoimmune cerebellar degeneration.Methods: Three patients with subacute to chronic cerebellar ataxia and controls underwent detailed clinical and neuropsychological assessment together with quantitative high-resolution structural MRI. Sera and CSF were subjected to comprehensive autoantibody screening by indirect immunofluorescence assay (IFA) and immunoblot. Immunoprecipitation with lysates of hippocampus and cerebellum combined with mass spectrometric analysis was used to identify the autoantigen, which was verified by recombinant expression in HEK293 cells and use in several immunoassays. Multiparameter flow cytometry was performed on peripheral blood and CSF, and peripheral blood was subjected to T-cell receptor spectratyping.Results: Patients presented with a subacute to chronic cerebellar and brainstem syndrome. MRI was consistent with cortical and cerebellar gray matter atrophy associated with subsequent neuroaxonal degeneration. IFA screening revealed strong immunoglobulin G1 reactivity in sera and CSF with hippocampal and cerebellar molecular and granular layers, but not with a panel of 30 recombinantly expressed established neural autoantigens. Neurochondrin was subsequently identified as the target antigen, verified by IFA and immunoblot with HEK293 cells expressing human neurochondrin as well as the ability of recombinant neurochondrin to neutralize the autoantibodies' tissue reaction. Immune phenotyping revealed intrathecal accumulation and activation of B and T cells during the acute but not chronic phase of the disease. T-cell receptor spectratyping suggested an antigen-specific T-cell response accompanying the formation of antineurochondrin autoantibodies. No such neurochondrin reactivity was found in control cohorts of various neural autoantibody-associated neurologic syndromes, relapsing-remitting multiple sclerosis, cerebellar type of multiple system atrophy, hereditary cerebellar ataxias, other neurologic disorders, or healthy donors. Conclusion:Neurochondrin is a neuronal target antigen in autoimmune cerebellar degeneration.Neurol Neuroimmunol Neuroinflamm 2017;4:e307; doi: 10.1212/NXI.0000000000000307 GLOSSARY AD 5 axial diffusivity; AI 5 antibody indices; DTI 5 diffusion tensor imaging; FA 5 fractional anisotropy; IFA 5 immunofluorescent assay; IgG 5 immunoglobulin G; IVIg 5 IV immunoglobulin; mGluR 5 metabotropic glutamate receptor; MSA-c 5 cerebellar type of multiple system atrophy; PB 5 peripheral blood; RD 5 radial diffusivity; RRMS 5 relapsing-remitting multiple sclerosis; SARA 5 Scale for the Assessment and Rating of Ataxia; TCR 5 T-cell receptor.Autoantibodies against neuronal constituents are associated with several severe immune-mediated CNS disorders. These disorders may predominantly affect gray matter structures of different brain regions such as the archicortex of the limbic system, neocortex, and basal ganglia, as well as cerebellar cortex and brainstem.

Objectives:To characterize the cellular autoimmune response in patients with γ-aminobutyric acid (GABA)B receptor antibody–associated limbic encephalitis (GABAB-R LE).Methods:Patients underwent MRI, extensive neuropsychological assessment, and multiparameter flow cytometry of peripheral blood and CSF.Results:We identified a series of 3 cases of nonparaneoplastic GABAB-R LE and one case of paraneoplastic GABAB-R LE associated with small cell lung cancer. All patients exhibited temporal lobe epilepsy, neuropsychological deficits, and MRI findings typical of LE. Absolute numbers of CD19+ B cells, CD138+ CD19+ plasma cells, CD4+ T cells, activated HLADR+ CD4+ T cells, as well as CD8+ T cells and HLADR+ CD8+ T cells did not differ in peripheral blood but were elevated in CSF of patients with GABAB-R LE compared to controls. Augmented absolute numbers of CD138+ CD19+ plasma cells and activated HLADR+ CD8+ T cells in CSF corresponded to higher overall neuropsychological and memory deficits in patients with GABAB-R LE. A histologic specimen of one patient following selective amygdalohippocampectomy revealed perivascular infiltrates of CD138+ plasma cells and CD4+ T cells, whereas cytotoxic CD8+ T cells were detected within the brain parenchyma in close contact to neurons.Conclusion:Our data suggest a pathogenic role for CD8+ T cells in addition to the established role of plasma cell–derived autoantibodies in GABAB-R LE.

BackgroundAntibodies (ABs) against the 65-kDa isoform of the intracellular enzyme glutamate decarboxylase (GAD65) have been found in limbic encephalitis (LE) and other neurological conditions. The direct significance of anti-GAD65-ABs for epilepsy is unclear. However, in histological preparations from biopsies of resective epilepsy surgeries, predominantly cytotoxic T-lymphocytes were detected making close contacts to neurons. Activated T-lymphocytes can, in turn, be selectively controlled by therapeutic interleukin-2 receptor Abs, such as basiliximab.Case presentationWe report of a 25-year-old male patient with epilepsy since the age of 18 and displaying clinical signs of LE and a high titer of GAD65 ABs in cerebrospinal fluid (CSF) and serum. Monthly, repetitive, intravenous cortisone pulse therapies that were initially administered for 6 months failed to improve his condition. Subsequent flow-cytometry analysis of CSF showed especially an increased fraction of activated HLA-DR+ CD8+ T-lymphocytes (fCD8+TL) when compared to controls. Thus, a second, intravenous cortisone pulse therapy with an additional basiliximab dose of 20 mg/month was started. After 3 months, the fCD8+TL in the CSF normalized; after 6 months, the psychological impulse-control deficits normalized; and after 11 months the patient was seizure free. However, 7 weeks later, seizures and, later on, psychological deficits recurred and fCD8+TL was once again present in the CSF. Flumazenil PET, magnetic resonance imaging-volumetry, and neuropsychological changes during therapy are described.ConclusionThe correlation of the fCD8+TL in the CSF with clinical and paraclinical measures of disease activity combined with the unambiguous response to basiliximab strongly argues in favor of the putative pathogenic role fCD8+TL in anti-GAD65 LE. The clinical relapse at the end of the observation period might be due to the formation of human anti-drug ABs, a well-known complication of therapy with chimeric ABs.

Autoimmune limbic encephalitis (ALE) is the most common type of autoimmune encephalitis (AIE). Subacute memory disturbance, temporal lobe seizures, and psychiatric symptoms are clinical hallmarks of the disease. However, little is known on the factors contributing to cognitive functioning in ALE. Hence, we here investigate major determinants of cognitive functioning in ALE. In a retrospective analysis of 102 patients with ALE, we first compared verbal learning capacity, nonverbal learning capacity, and attentional and executive functioning by absence or presence of different types of neural autoantibodies (AABs). Subsequently we established three linear regression models including 63, 38, and 61 patients, respectively to investigate how cognitive functioning in these domains may depend on common markers of ALE such as intrathecal inflammation, blood‐cerebrospinal fluid (CSF)‐barrier function, mesiotemporal epileptiform discharges and slowing, determined by electroencephalography (EEG) and structural mesiotemporal changes, measured with magnetic resonance imaging (MRI). We also accounted for possible effects of cancer‐ and immunotherapy and other centrally effective medication. There was no effect of AAB status on cognitive functioning. Although the regression models could not predict verbal and nonverbal learning capacity, structural mesiotemporal neural network alterations on T2‐/fluid attenuated inversion recovery (FLAIR)‐signal‐weighted MRI and mesiotemporal epileptiform discharges or slowing on EEG exerted a significant impact on memory functions. In contrast, the regression model significantly predicted attentional and executive functioning with CSF white blood cell count and centrally effective medication being significant determinants. In this cohort, cognitive functioning in ALE does not depend on the AAB status. Common markers of ALE cannot predict memory functioning that only partially depends on structural and functional alterations of mesiotemporal neural networks. Common markers of ALE significantly predict attentional and executive functioning that is significantly related to centrally effective medication and CSF white blood cell count, which may point toward inflammation affecting brain regions beyond the limbic system.