Altered Repertoire Diversity and Disease-Associated Clonal Expansions Revealed by T Cell Receptor Immunosequencing in Ankylosing Spondylitis Patients.

Aimee L Hanson,Kim‐Anh Lê Cao,Julie Phipps,Hendrik J Nel,Linda Bradbury,Tony J Kenna,Ranjeny Thomas,Matthew A Brown

doi:10.1002/art.41252

Abstract

Ankylosing spondylitis (AS) is a common spondyloarthropathy primarily affecting the axial skeleton and strongly associated with HLA-B*27 carriage. Genetic evidence implicates both autoinflammatory processes and autoimmunity against an HLA-B*27-restricted autoantigen in immunopathology. In addition to articular symptoms, up to 70% of AS patients present with concurrent bowel inflammation, suggesting that adverse interactions between a genetically primed host immune system and the gut microbiome contribute to the disease. Accordingly, this study aimed to characterize adaptive immune responses to antigenic stimuli in AS. The peripheral CD4 and CD8 T cell receptor (TCR) repertoire was profiled in AS patients (n = 47) and HLA-B*27-matched healthy controls (n = 38). Repertoire diversity was estimated using the Normalized Shannon Diversity Entropy (NSDE) index, and univariate and multivariate statistical analyses were performed to characterize AS-associated clonal signatures. Furthermore, T cell proliferation and cytokine production in response to immunogenic antigen exposure were investigated in vitro in peripheral blood mononuclear cells from AS patients (n = 19) and HLA-B*27-matched healthy controls (n = 14). Based on the NSDE measure of sample diversity across CD4 and CD8 T cell repertoires, AS patients showed increased TCR diversity compared to healthy controls (for CD4 T cells, P = 7.8 × 10-6 ; for CD8 T cells, P = 9.3 × 10-4 ), which was attributed to a significant reduction in the magnitude of peripheral T cell expansions globally. Upon in vitro stimulation, fewer T cells from AS patients than from healthy controls expressed interferon-γ (for CD8 T cells, P = 0.03) and tumor necrosis factor (for CD4 T cells, P = 0.01; for CD8 T cells, P = 0.002). In addition, the CD8 TCR signature was altered in HLA-B*27+ AS patients compared to healthy controls, with significantly expanded Epstein-Barr virus-specific clonotypes (P = 0.03) and cytomegalovirus-specific clonotypes (P = 0.02). HLA-B*27+ AS patients also showed an increased incidence of "public" CD8 TCRs, representing identical clonotypes emerging in response to common antigen encounters, including homologous clonotypes matching those previously isolated from individuals with bacterial-induced reactive arthritis. The dynamics of peripheral T cell responses in AS patients are altered, suggesting that differential antigen exposure and disrupted adaptive immunity are underlying features of the disease.

Highlights

TCRβ immunosequencing was conducted in peripheral blood mononuclear cells (PBMCs) from 47 Ankylosing spondylitis (AS) patients and healthy controls (Table 1)
Twenty patients were receiving treatment with a tumor necrosis factor (TNF) antagonist at the time of sampling, which resulted in significantly lower disease activity according to the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI; scale 0–10) [33], as compared to patients who had not received biologic treatment (Table 1)
Given the decreased percentage of CD4 and CD8 T cells contained in large expansions in the peripheral blood of AS patients, we examined whether the T cell receptor (TCR) repertoires in AS patients demonstrated evidence of reduced peripheral T cell expansion in response to common viral infection

Summary

Introduction

Ankylosing spondylitis (AS) is a seronegative immune- mediated arthritis affecting the axial skeleton, in which enthesitis leads to joint erosion and reactive bone formation. Professor Thomas’ work was supported by an NHMRC of Australia Fellowship (grant 1071822) and Arthritis Queensland.

Methods

Results

Conclusion