Antibodies Against Glutamic Acid Decarboxylase 65 Are Locally Produced in the CSF and Arise During Affinity Maturation

Background and Objectives Antibodies (Abs) against the cytoplasmic protein glutamic acid decarboxylase 65 (GAD65) are detected in patients with neurologic syndromes together referred to as GAD65-Ab spectrum disorders. The response of some of these patients to plasma exchange or immunoglobulins indicates that GAD65-Abs could contribute to disease pathogenesis at least at some stages of disease. However, the involvement of GAD65-reactive B cells in the CNS is incompletely understood. Methods We studied 7 patients with high levels of GAD65-Abs and generated monoclonal Abs (mAbs) derived from single cells in the CSF. Sequence characteristics, reactivity to GAD65, and the role of somatic hypermutations of the mAbs were analyzed. Results Twelve CSF-derived mAbs were generated originating from 3 patients with short disease duration, and 7/12 of these mAbs (58%) were GAD65 reactive in at least 1 detection assay. Four of 12 (33%) were definitely positive in all 3 detection assays. The intrathecal anti-GAD65 response was polyclonal. GAD65-Abs were mostly of the IgG1 subtype and had undergone affinity maturation. Reversion of 2 GAD65-reactive mAbs to their corresponding germlineencoded unmutated common ancestors abolished GAD65 reactivity. Discussion GAD65-specific B cells are present in the CNS and represent a sizable fraction of CSF B cells early in the disease course. The anti-GAD65 response in the CSF is polyclonal and shows evidence of antigen-driven affinity maturation required for GAD65 recognition. Our data support the hypothesis that the accumulation of GAD65-specific B cells and plasma cells in the CSF is an important feature of early disease stages

Persistence of functional memory B cells recognizing SARS-CoV-2 variants despite loss of specific IgG

Although some COVID-19 patients maintain SARS-CoV-2-specific serum immunoglobulin G (IgG) for more than 6 months postinfection, others eventually lose IgG levels. We assessed the persistence of SARS-CoV-2-specific B cells in 17 patients, 5 of whom had lost specific IgGs after 5–8 months. Differentiation of blood-derived B cells in vitro revealed persistent SARS-CoV-2-specific IgG B cells in all patients, whereas IgA B cells were maintained in 11. Antibodies derived from cultured B cells blocked binding of viral receptor-binding domain (RBD) to the cellular receptor ACE-2, had neutralizing activity to authentic virus, and recognized the RBD of the variant of concern Alpha similarly to the wild type, whereas reactivity to Beta and Gamma were decreased. Thus, differentiation of memory B cells could be more sensitive for detecting previous infection than measuring serum antibodies. Understanding the persistence of SARS-CoV-2-specific B cells even in the absence of specific serum IgG will help to promote long-term immunity

A genome-wide in vivo CRISPR screen identifies essential regulators of T cell migration to the CNS in a multiple sclerosis model

Multiple sclerosis (MS) involves the infiltration of autoreactive T cells into the CNS, yet we lack a comprehensive understanding of the signaling pathways that regulate this process. Here, we conducted a genome-wide in vivo CRISPR screen in a rat MS model and identified 5 essential brakes and 18 essential facilitators of T cell migration to the CNS. While the transcription factor ETS1 limits entry to the CNS by controlling T cell responsiveness, three functional modules, centered around the adhesion molecule & alpha;4-integrin, the chemokine receptor CXCR3 and the GRK2 kinase, are required for CNS migration of autoreactive CD4+ T cells. Single-cell analysis of T cells from individuals with MS confirmed that the expression of these essential regulators correlates with the propensity of CD4+ T cells to reach the CNS. Our data thus reveal key regulators of the fundamental step in the induction of MS lesions. Multiple sclerosis (MS) lesions are initiated by the infiltration of T cells to the CNS. Here, Kendirli et al. use a genome-wide CRISPR screen in an MS model to define the molecules that regulate T cell entry to the CNS

Identification of circulating MOG-specific B cells in patients with MOG antibodies

Objective To identify circulating myelin oligodendrocyte glycoprotein (MOG)-specific B cells in the blood of patients with MOG antibodies (Abs) and to determine whether circulating MOG-specific B cells are linked to levels and epitope specificity of serum anti-MOG-Abs. Methods We compared peripheral blood from 21 patients with MOG-Abs and 26 controls for the presence of MOG-specific B cells. We differentiated blood-derived B cells in vitro in separate culture wells to Ab-producing cells via engagement of Toll-like receptors 7 and 8. We quantified the anti-MOG reactivity with a live cell-based assay by flow cytometry. We determined the recognition of MOG epitopes with a panel of mutated variants of MOG. Results MOG-Ab-positive patients had a higher frequency of MOG-specific B cells in blood than controls, but MOG-specific B cells were only detected in about 60% of these patients. MOG-specific B cells in blood showed no correlation with anti-MOG Ab levels in serum, neither in the whole group nor in the untreated patients. Epitope analysis of MOG-Abs secreted from MOG-specific B cells cultured in different wells revealed an intraindividual heterogeneity of the anti-MOG autoimmunity. Conclusions This study shows that patients with MOG-Abs greatly differ in the abundance of circulating MOG-specific B cells, which are not linked to levels of MOG-Abs in serum suggesting different sources of MOG-Abs. Identification of MOG-specific B cells in blood could be of future relevance for selecting patients with MOG-Abs for B cell-directed therapy

Search for heavy long-lived multi-charged particles in pp collisions at √s = 8 TeV using the ATLAS detector

A search for heavy long-lived multi-charged particles is performed using the ATLAS detector at the LHC. Data collected in 2012 at s√ = 8 TeV from pp collisions corresponding to an integrated luminosity of 20.3 fb−1 are examined. Particles producing anomalously high ionisation, consistent with long-lived massive particles with electric charges from |q|=2e to |q|=6e are searched for. No signal candidate events are observed, and 95% confidence level cross-section upper limits are interpreted as lower mass limits for a Drell–Yan production model. The mass limits range between 660 and 785 GeV

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements