Background/Purpose:

In the pre-clinical rheumatoid arthritis (RA) prodrome, autoantibodies and transient symptoms may develop. Pre-clinical autoantibody development suggests concomitant expansion of autoantigen-specific CD4⁺ follicular helper T cells (T_FH). A biased T cell receptor (TCR) repertoire in the joints of recent-onset RA patients suggests clonal expansion in early RA. Antigen-specific CD4⁺ T cells were clonally expanded at onset of murine collagen-induced arthritis. To model the pathogenetic role played by autoantigen-specific CD4⁺ T cells before and after autoantibody development, we longitudinally assessed the frequency, phenotype and clonotypic composition of the dominant aggrecan_89-103 epitope-specific CD4⁺ T cell repertoire in proteoglycan-induced arthritis (PGIA). We aimed to elucidate how and when autoantigen-specific CD4⁺ T cells contribute to arthritis progression.

Methods:

PGIA was induced in BALB/cAnNCrl and BALB/c FoxP3-GFP mice by intraperitoneal injection (prime and two booster injections) of recombinant G1 epitope of human proteoglycan (rhG1-PG) emulsified in DDA adjuvant. MHC class II (IA^d)-aggrecan_89-103 tetramers and single-cell multiplex-nested PCR-TCR sequencing was used to study splenic aggrecan_89-103-specific CD4⁺ T cells before and after onset of PGIA. Quantitative and phenotypic analysis of aggrecan_89-103-specific CD4⁺ T cells was assessed by flow cytometry, based on the expression of CD44, CD62L, FoxP3, CXCR5 and PD1 and index sorting in TCR sequencing experiments. ELISA measured anti-human PG-specific antibodies.

Results:

Splenic aggrecan_89-103-specific CD4⁺ T cells expanded in the prodrome before the detection of autoantibodies or persistent disease activity. Aggrecan_89-103-specific CD4⁺ T cells shifted from naïve to activated effector memory (T_EM) and T_FH, associated with a loss of aggrecan­_89-103-specific FoxP3⁺ Treg. CD4⁺ TCR β-chain variable genes (TRBV)13-1⁺, 13-2⁺ and 2⁺ aggrecan_89-103-specific T_EM and T_FH cells clonally expanded in the prodromal period during transient joint inflammation. After clonotype depletion with anti-TRBV13 mAb, disease onset was delayed, autoantibody titres reduced and arthritis attenuated. Three public TRBV13⁺ clonotypes were shared between mice and between different BALB/c strains. All public clonotypes had conserved amino acid residues arising from convergent recombination, supporting selection of TCR for antigen recognition.

Conclusion:

Antigen-specific public clonotypes expand during the prodromal period, prior to development of autoantibodies. Therefore longitudinal antigen-specific TCR repertoire analysis prior to high titre autoantibody development may identify expanding autoreactive CD4⁺ T cell clones in individuals at risk of RA.

« Back to 2018 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/pre-clinical-clonally-expanded-aggrecan89-103-specific-cd4-t-cells-are-a-target-for-autoimmune-arthritis-prevention/