Background:The majority of patients with rheumatoid arthritis (RA) produce autoantibodies against proteins that have undergone post-translational modfication, e.g. citrullination or carbamylation. There is growing evidence of their relevance and their potential utility to improve diagnosis, patient stratification, and prognosis for precision medicine. Investigating new autoantibody patterns may allow further stratification of patients and identifying subsets of patients that benefit from different treatment modalities. Following the discovery of high autoantibody reactivity against multiple modified proteins the interest in native targets decreased. Even though antibodies reacting with native proteins may also have a role in RA pathogenesis, their reactivity patterns are much less studied.Objectives:To identify novel native autoantigens in RA patients and elucidate patterns within autoantibody reactivity against native autoantigens.Methods:We investigated the reactivity of autoantibodies in plasma pools from 15 anti-CCP positive and 10 anti-CCP negative RA patients and 10 healthy donors against more than 1600 human proteins in native configuration using the Immunome high-density protein microarray.Results:We identified 86 native proteins that were recognized by IgG antibodies from anti-CCP positive RA patients and 76 native proteins recognized by IgG antibodies from anti-CCP negative RA patients, but not by antibodies from healthy donors. Examples of proteins recognized by both patient subgroups are calcium/calmodulin-dependent protein kinase type II subunits, histone deacetylases, keratin, and vimentin. Reactivity against the ribonucleic protein SSB was observed in anti-CCP negative RA patients only.Conclusion:Several human proteins in their native conformation are recognized by autoantibodies from anti-CCP positive as well as anti-CCP negative RA patients. In general, anti-CCP positive patients had higher autoantibody activity than anti-CCP negative patients and healthy donors.References:[1] Konig, M.F., Giles, J.T., Nigrovic, P.A., Andrade, F., 2016. Antibodies to native and citrullinated RA33 (hnRNP A2/B1) challenge citrullination as the inciting principle underlying loss of tolerance in rheumatoid arthritis. Ann. Rheum. Dis. 75, 2022–2028.[2] Zheng, Z., Mergaert, A.M., Fahmy, L.M., Bawadekar, M., Holmes, C.L., Ong, I.M., Bridges, A.J., Newton, M.A., Shelef, M.A., 2019. Disordered Antigens and Epitope Overlap Between Anti-Citrullinated Protein Antibodies and Rheumatoid Factor in Rheumatoid Arthritis. Arthritis Rheumatol. art.41074.[3] Sirotti, S., Generali, E., Ceribelli, A., Isailovic, N., De Santis, M., Selmi, C., 2017. Personalized medicine in rheumatology: the paradigm of serum autoantibodies. Autoimmun. Highlights 8.Acknowledgments :The Department of Clinical Immunology at Rigshospitalet Copenhagen is acknowledged for providing the healthy donor blood. The study is part of the PROCIT study financed by the Danish Council for Independent Research (grant no. DFF - 7016-00233). Moreover, the Obelske Family Foundation, the Svend Andersen Foundation, the Spar Nord Foundation and the Danish National Mass Spectrometry Platform for Functional Proteomics (PRO-MS; grant no. 5072-00007B) are acknowledged for grants to the analytical platform are acknowledged for the funding to enabling parts of this study.Disclosure of Interests:Thomas B.G. Poulsen: None declared, Dres Damgaard: None declared, Malene Møller Jørgensen: None declared, Ladislav Senolt: None declared, Jonathan Blackburn Shareholder of: Sengenics Corporation, Consultant of: Director of Sengenics Corporation, Employee of: Director of Sengenics Corporation, Claus Henrik Nielsen: None declared, Allan Stensballe: None declared
Identification of Novel Native Autoantigens in Rheumatoid Arthritis