Contributions
Abstract: EP1481
Type: Poster Sessions
Abstract Category: Pathology and pathogenesis of MS - Immunology
Introduction: The pathogenic role of B cells in multiple sclerosis (MS) is not known. We have previously demonstrated that B cells from cerebrospinal fluid (CSF) of MS patients can activate T cells through specific recognition of antigenic determinants (idiotopes) from their own B cells receptors (BCR). The aim of the present study was to test whether antigenic properties of immunoglobulin variable heavy chain (IGVH) repertoires can be predicted in silico.
Methods: Transcribed IGVH repertoires from MS patients were sequenced and translated. In silico predicted human leukocyte antigen (HLA) class II affinity and endosomal processing, as well as T cell exposed motif rarity and transcript frequency, guided selection of ten potential stimulatory (rare) and five potential regulatory (frequent) idiotope-peptides from two MS patients. To validate the predictions, peripheral blood mononuclear cells from these patients were stimulated with 15-mer idiotope-peptides in presence of anti-CD40 for 16 hours. T cells were then labeled for activation status with anti-CD154 antibodies and phenotyped with anti-CD3, -CD4, -CD45RO, -CXCR5, -GARP and -PD-1, as well as anti-CD14 and -CD8 for dump channel. Unstimulated cells and/or insulin peptides were used as negative controls, and HLA class II restricted virus peptides including EBNA-1 were used as positive controls.
Results: In two MS patients, four of eight and seven of 14 idiotope-peptides predicted to be T cell antigens induced similar CD4+ T cell activation as the positive control peptides. The responding CD4+ T cells were mainly CD45RO+ memory T cells, and included more CXCR5+ follicular-like helper cells than those activated by negative control peptides. Activation of Tregs (GARP+CD154-CD4+ T cells) was equally low for idiotope- and control peptides.
Conclusion: This in vitro pilot study suggests that MS patients have a memory T cell repertoire capable of recognizing frequent BCRs from endogenous CSF. It further indicates that antigenic properties of BCR-idiotopes from CSF of MS patients can be predicted in silico using HLA affinity and endosomal processing predictions. The rarity of one particular idiotope does not seem to predict whether T cells are tolerant to that idiotope.
Disclosure: RAH has received speaker honoraria and/or received unrestricted research grants from Biogen, Merck, Novartis and Roche. AL has received speaker honoraria from Roche, and unrestricted research grants from Sanofi Genzyme. RB holds equity in EigenBio, the company responsible for designing the bioinformatics models used in this project. TH has received speaker honoraria, and/or served on advisory board, and/or received unrestricted research grants from Biogen, Roche, Merck, Novartis, and Genzyme. The study was supported with a grant from the Norwegian Research Council (grant 250864/F20), as well as unrestricted grants from Biogen Norway and the Fritz and Ingrid Nilsen endowment.
Abstract: EP1481
Type: Poster Sessions
Abstract Category: Pathology and pathogenesis of MS - Immunology
Introduction: The pathogenic role of B cells in multiple sclerosis (MS) is not known. We have previously demonstrated that B cells from cerebrospinal fluid (CSF) of MS patients can activate T cells through specific recognition of antigenic determinants (idiotopes) from their own B cells receptors (BCR). The aim of the present study was to test whether antigenic properties of immunoglobulin variable heavy chain (IGVH) repertoires can be predicted in silico.
Methods: Transcribed IGVH repertoires from MS patients were sequenced and translated. In silico predicted human leukocyte antigen (HLA) class II affinity and endosomal processing, as well as T cell exposed motif rarity and transcript frequency, guided selection of ten potential stimulatory (rare) and five potential regulatory (frequent) idiotope-peptides from two MS patients. To validate the predictions, peripheral blood mononuclear cells from these patients were stimulated with 15-mer idiotope-peptides in presence of anti-CD40 for 16 hours. T cells were then labeled for activation status with anti-CD154 antibodies and phenotyped with anti-CD3, -CD4, -CD45RO, -CXCR5, -GARP and -PD-1, as well as anti-CD14 and -CD8 for dump channel. Unstimulated cells and/or insulin peptides were used as negative controls, and HLA class II restricted virus peptides including EBNA-1 were used as positive controls.
Results: In two MS patients, four of eight and seven of 14 idiotope-peptides predicted to be T cell antigens induced similar CD4+ T cell activation as the positive control peptides. The responding CD4+ T cells were mainly CD45RO+ memory T cells, and included more CXCR5+ follicular-like helper cells than those activated by negative control peptides. Activation of Tregs (GARP+CD154-CD4+ T cells) was equally low for idiotope- and control peptides.
Conclusion: This in vitro pilot study suggests that MS patients have a memory T cell repertoire capable of recognizing frequent BCRs from endogenous CSF. It further indicates that antigenic properties of BCR-idiotopes from CSF of MS patients can be predicted in silico using HLA affinity and endosomal processing predictions. The rarity of one particular idiotope does not seem to predict whether T cells are tolerant to that idiotope.
Disclosure: RAH has received speaker honoraria and/or received unrestricted research grants from Biogen, Merck, Novartis and Roche. AL has received speaker honoraria from Roche, and unrestricted research grants from Sanofi Genzyme. RB holds equity in EigenBio, the company responsible for designing the bioinformatics models used in this project. TH has received speaker honoraria, and/or served on advisory board, and/or received unrestricted research grants from Biogen, Roche, Merck, Novartis, and Genzyme. The study was supported with a grant from the Norwegian Research Council (grant 250864/F20), as well as unrestricted grants from Biogen Norway and the Fritz and Ingrid Nilsen endowment.