Autoreactive T cells identified in patients with anti-Jo1+ antisynthetase syndrome recognise a new epitope on histidyl t-RNA synthetase.

Abstract

Anti-Jo1+ antisynthetase syndrome (ASyS) is characterised by autoantibodies targeting histidyl t-RNA synthetase (HisRS), association with HLA-DRB1*03:01 and a distinct clinical phenotype including interstitial lung disease, myositis, arthritis, and mechanic's hands. Previous studies of autoreactive HisRS-specific CD4⁺T cells point to yet undiscovered T cell epitopes. We aimed to identify new epitopes on HisRS to investigate the presence of autoreactive T cells and their corresponding T-cell receptor (TCR) repertoire from patients with ASyS. Peptides from HisRS N-terminal region with appropriate major histocompatibility complex (MHC) anchor residues were selected for in vitro binding assays. The peptide (HisRS_41-55) with the highest HLA-DRB1*03:01 binding affinity was selected for studies with HLA-class II tetramers. Peripheral blood mononuclear cells (PBMCs) from patients with ASyS with HLA-DRB1*03:01 (n = 12) were stimulated in vitro with peptide and peptide-HLA-DRB1*03:01 tetramers were used to detect HisRS⁺CD4⁺T cells. Single TCR sequencing of captured T cells allowed analyses of the underlying TCR repertoire. We identified a new T cell epitope on HisRS with high affinity for HLA-DRB1*03:01. Autoreactive HisRS⁺CD4⁺T cells were detected in PBMCs of patients (n = 6/12). TCR repertoire analysis of HisRS⁺CD4⁺T cells revealed shared gene V-alpha and beta usages. Moreover, HisRS⁺CD4⁺T cells persisted after treatment in 2 patients (P2 and P4) and 2 identical T cell clones were detected between the initial and follow-up time points in 1 patient (P2). Autoreactive T-cells targeting a new HisRS epitope were identified indicating T cell reactivity to diverse epitopes of the HisRS protein in patients with anti-Jo1 autoantibodies. Furthermore, we demonstrated the TCR repertoire of autoreactive HisRS+CD4+T cells in patients. Persistence of these T-cells and specific clones may be contributing to disease.