Background: Staphylococcus aureus and Streptococcus pyogenes produce a number of superantigens able to cross-link TCRs with HLA-DR molecules and stimulate T-cells in a peptide-independent manner. Most superantigens bind TCRs via the TCR β-chain with individual preferences to certain TRBV families. TSST-1 from S.aureus and SpeC from S.pyogenes interact with the RA-associated HLA-DRB1*01 and *04, respectively, and are known to stimulate the TRBV12-3/12-4+ and TRBV20-1+ T cells. Analyzing the TCR repertoires in the joints of RA-patients vs healthy controls may reveal a potential role for superantigens in RA.

Objectives: To test the hypothesis that S.aureus and S.pyogenes superantigens contribute to bias the autoreactive TCR repertoire in RA.

Methods: We used DR4-restricted T cell epitopes from citrullinated cartilage intermediate layer protein (cit-CILP _297-311 ) and influenza matrix protein (MP _97-116 ) to investigate antigen-specific responses in ACPA+ HLA-DR*04+ RA patient synovial fluids. We used HLA-DR tetramers to single cell sort cit-CILP-specific and influenza MP-specific CD4+ T cells and compared with peripheral blood of HLA-matched healthy controls. Following TCR sequencing, we compared autoreactive TCRs with virus-specific TCRs s from the same samples to identify potential disease-relevant TCR signatures. We also validated and extended our analyses in two previously reported TCR sequence data sets from our lab (Sharma et al 2021, Turcinov et al 2023).

Results: We identified 260 αβ-paired citCILP-specific autoreactive TCR sequences from synovial fluids of RA patients and 63 from peripheral blood of HC, as well 336 influenza-specific TCRs from RA patients and 277 HC. The TRBV, TRBJ, TRBA and TRAJ gene usage was analyzed using MixCR and TCRdist. From this analysis we identified an overrepresentation of the TRBV20-1 gene variant in the CILP-specific TCRs from RA patients vs HC; this bias was not observed among virus-specific TCRs. Interestingly, TRBV20-1+ TCRs are known to bind superantigens from S.aureus and S.pyogenes . Going back to our other TCR repertoire data sets from RA patients, we again observed an over usage of the TRBV20-1 in both tetramer-sorted cells specific to another candidate autoantigen (tenascin C) as well in non-tetramer sorted cells from early RA synovial tissue biopsies from HLA-DR4+ patients.

Conclusion: The TCR repertoire from joints of RA patients suggests a possible role of superantigen-driven T cell stimulation in RA. This was evident for the autoimmune TCR repertoire but not for the influenza repertoire.

REFERENCES: NIL.

Acknowledgements: NIL.

Disclosure of Interests: Anatoly Dubnovitsky: None declared. Ravi Kumar: None declared. Begum Horuluoglu: None declared. Sara Turcinov: None declared. Lars Klareskog: None declared. Vivianne Malmström Pfizer, ONO.

© The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.