Two-dimensional analysis reveals that peptide–MHC class II tetramers underestimate the frequency of cytokine-producing antigen-specific CD4+ T cells in polyclonal responses.

No abstract

Central nervous system B cells have several potential roles in multiple sclerosis (MS): secretors of proinflammatory cytokines and chemokines, presenters of autoantigens to T cells, producers of pathogenic antibodies, and reservoirs for viruses that trigger demyelination. To interrogate these roles, single-cell RNA sequencing (scRNA-Seq) was performed on paired cerebrospinal fluid (CSF) and blood from subjects with relapsing-remitting MS (RRMS; n = 12), other neurologic diseases (ONDs; n = 1), and healthy controls (HCs; n = 3). Single-cell immunoglobulin sequencing (scIg-Seq) was performed on a subset of these subjects and additional RRMS (n = 4), clinically isolated syndrome (n = 2), and OND (n = 2) subjects. Further, paired CSF and blood B cell subsets (RRMS; n = 7) were isolated using fluorescence activated cell sorting for bulk RNA sequencing (RNA-Seq). Independent analyses across technologies demonstrated that nuclear factor kappa B (NF-κB) and cholesterol biosynthesis pathways were activated, and specific cytokine and chemokine receptors were up-regulated in CSF memory B cells. Further, SMAD/TGF-β1 signaling was down-regulated in CSF plasmablasts/plasma cells. Clonally expanded, somatically hypermutated IgM+ and IgG1+ CSF B cells were associated with inflammation, blood–brain barrier breakdown, and intrathecal Ig synthesis. While we identified memory B cells and plasmablast/plasma cells with highly similar Ig heavy-chain sequences across MS subjects, similarities were also identified with ONDs and HCs. No viral transcripts, including from Epstein–Barr virus, were detected. Our findings support the hypothesis that in MS, CSF B cells are driven to an inflammatory and clonally expanded memory and plasmablast/plasma cell phenotype.

Background: Vaccine-elicited adaptive immunity is a prerequisite for control of SARS-CoV-2 infection. Multiple sclerosis (MS) disease-modifying therapies (DMTs) differentially target humoral and cellular immunity. A comprehensive comparison of MS DMTs on SARS-CoV-2 vaccine-specific immunity is needed, including quantitative and functional B and T cell responses.Methods: Spike-specific antibody and T cell responses were measured before and following SARS-CoV-2 vaccination in a cohort of 80 subjects, including healthy controls and MS patients in six DMT groups: untreated, glatiramer acetate (GA), dimethyl fumarate (DMF), natalizumab (NTZ), sphingosine-1-phosphate (S1P) receptor modulators, and anti-CD20 monoclonal antibodies. Anti-spike antibody responses were quantified by Luminex assay, high-resolution spike epitope reactivity was mapped by VirScan, and pseudovirus neutralization was assessed.Spike-specific CD4+ and CD8+ T cell responses were characterized by activation-induced marker (AIM) expression, cytokine production, and tetramer analysis.Results: Anti-spike IgG levels were similar between healthy controls, untreated MS, GA, DMF, and NTZ patients, but were significantly reduced in anti-CD20 and S1P-treated patients. Antispike seropositivity in anti-CD20 patients was significantly correlated with CD19+ B cell levels and inversely correlated with cumulative treatment duration. Spike epitope reactivity and pseudovirus neutralization was reduced in anti-CD20 and S1P patients, directly correlating with reduced spike receptor binding domain (RBD) IgG levels. Spike-specific CD4+ and CD8+ T cell reactivity remained robust across all groups except in S1P-treated patients in whom post-vaccine CD4+ T cell responses were attenuated.Conclusions: These findings from a large MS cohort exposed to a wide spectrum of MS immunotherapies have important implications for treatment-specific COVID-19 clinical guidelines.

CD8 + T cells are believed to play an important role in multiple sclerosis (MS), yet their role in MS pathogenesis remains poorly defined. Although myelin proteins are considered potential autoantigenic targets, prior studies of myelin-reactive CD8 + T cells in MS have relied on in vitro stimulation, thereby limiting accurate measurement of their ex vivo precursor frequencies and phenotypes. Peptide:MHC I tetramers were used to identify and validate 5 myelin CD8 + T cell epitopes, including 2 newly described determinants in humans. The validated tetramers were used to measure the ex vivo precursor frequencies and phenotypes of myelin-specific CD8 + T cells in the peripheral blood of untreated MS patients and HLA allele-matched healthy controls. In parallel, CD8 + T cell responses against immunodominant influenza epitopes were also measured. There were no differences in ex vivo frequencies of tetramerpositive myelin-specific CD8 + T cells between MS patients and control subjects. An increased proportion of myelin-specific CD8 + T cells in MS patients exhibited a memory phenotype and expressed CD20 compared to control subjects, while there were no phenotypic differences observed among influenza-specific CD8 + T cells. Longitudinal assessments were also measured in a subset of MS patients subsequently treated with anti-CD20 monoclonal antibody therapy. The proportion of memory and CD20 + CD8 + T cells specific for certain myelin but not influenza epitopes was significantly reduced following anti-CD20 treatment. This study, representing a characterization of unmanipulated myelin-reactive CD8 + T cells in MS, indicates these cells may be attractive targets in MS therapy. multiple sclerosis | CD8 + T cells | myelin antigen | anti-CD20 therapy

Compared with influenza-specific T cells, self-reactive T cells from patients with multiple sclerosis or type 1 diabetes fail to slow down and do not form normal immunological synapses upon encounter with cognate self-peptide presented by MHC.

Once considered to be of sole importance in allergy and parasitic infections, the role of mast cells in other pathologic and protective immune responses is becoming increasingly evident. We previously demonstrated that mast cells contribute to the severity of EAE, the rodent model of multiple sclerosis. Here we show that one mode of mast cell action is through effects on the autoreactive T cell response. Early indices of both peripheral CD4 and CD8 T cell activation, including IFN-c production and increases in CD44 and CD11a expression, are attenuated in mast cell-deficient (W/W v ) mice after myelin oligodendrocyte glycoprotein priming when compared to WT animals. Reduced infiltrates of activated T cells in the central nervous system are also observed. Importantly, selective repletion of the mast cell compartment restores most T cell responses in the lymph nodes and the central nervous system, correlating with reconstitution of severe disease. The adoptive transfer of WT-derived encephalitogenic T cells results in significantly less severe disease in W/W v recipients, indicating that mast cells also exert potent effects after the initial T cell response is generated. Our data provide the first in vivo evidence that mast cells can significantly influence T cell responses and suggest that mast cells exacerbate disease during both the inductive and effector phases.

MHC variant peptides are analogues of immunogenic peptides involving alterations of the MHC-binding residues, thereby altering the affinity of the peptide for the MHC molecule. Recently, our laboratory demonstrated that immunization of WT B6 mice with 45D, a low-affinity MHC variant peptide of MOG35–55, results in significantly attenuated experimental autoimmune encephalomyelitis (EAE), yet IFN-γ production is comparable to myelin oligodendrocyte glycoprotein (MOG)35–55-immunized mice. In light of these findings, we asked whether IFN-γ was required for the reduced encephalitogenicity of the weak ligand 45D in EAE. In this study, we report that immunization of mice deficient in IFN-γ or its receptor with 45D exhibit significant EAE signs compared with 45D-immunized wild-type B6 mice. Moreover, 45D-immunized IFN-γ−/− and IFN-γR−/− mice demonstrate MOG tetramer-positive CD4+ T cells within the CNS and display substantial numbers of MOG-specific CD4+ T cells in the periphery. In contrast, wild-type mice immunized with 45D exhibit reduced numbers of MOG-specific CD4+ T cells in the periphery and lack MOG tetramer- positive CD4+ T cells in the CNS. Importantly, the increased encephalitogenicity of 45D in mice lacking IFN-γ or IFN-γR was not due to deviation toward an enhanced IL-17-secreting phenotype. These findings demonstrate that IFN-γ significantly attenuates the encephalitogenicity of 45D and are the first to highlight the importance of IFN-γ signaling in setting the threshold level of responsiveness of autoreactive CD4+ T cells to weak ligands.