POS0189 SERUM IFNα CONCENTRATIONS MEASURED WITH SINGLE-MOLECULE ARRAY TECHNOLOGY IN SJÖGREN’S SYNDROME REFLECT BLOOD INTERFERON-STIMULATED GENE EXPRESSION
Authors: E. Huijser, J. Göpfert, Z. Brkic, C. G. Van Helden-Meeuwsen, S. Jansen, T. Mandl, P. Olsson, B. Schrijver, M. W. Schreurs, P. L. Van Daele, W. A. Dik, M. Versnel
Journal: Annals of the Rheumatic Diseases (2021)

Background: Type I interferon (IFN-I) activation is a prominent feature of several Rheumatic and Musculoskeletal Diseases (RMDs) including primary Sjögren’s syndrome (pSS), systemic lupus erythematosus (SLE) and systemic sclerosis (SSc). Ultrasensitive single-molecule array (SiMoA) technology has facilitated the measurement of subfemtomolar concentrations of IFNs [1-3]. Objectives: Here, we tested the performance of a commercially available SiMoA kit for detection of IFNα in serum from pSS, SLE, and SSc and correlated serum IFNα to whole blood IFN-stimulated gene (ISG) expression. Methods: Serum IFNα2 was measured in healthy controls (HC; n=68) and patients with pSS (n=85, n=110), SLE (n=24) and SSc (n=23) using a ready-to-use IFNα SiMoA kit on a HD-X Analyzer. IFN-I activation was additionally determined from paired samples of whole blood IFN-stimulated gene (ISG) expression of IFI44, IFI44L, IFIT1, IFIT3, and MxA by RT-PCR or MxA-ELISA. Results: Serum IFNα2 levels were elevated in pSS (median = 61.3 fg/mL) compared to HC (median &lt; 5fg/mL) and SSc (median = 11.6 fg/mL), lower compared to SLE (median = 313.5 fg/mL), and positively correlated to whole blood ISG expression (rs=0.71-0.76, p&lt;0.001). Comparable to MxA-ELISA (AUC=0.93), IFNα2 SiMoA identified pSS with high ISG expression (AUC=0.90) with 80-93% specificity and 71-84% sensitivity. Blinded validation in an independent pSS cohort yielded a comparable accuracy of 89%. Multiple linear regression indicated independent associations of autoantibodies, IgG, and use of hydroxychloroquine with serum IFNα2 concentrations in pSS. Confirming the literature [4], serum IFNα2 levels were lower in SLE patients in remission (DORIS classification) compared to patients not in remission. Conclusion: Thus, SiMoA serum IFNα2 reflects blood ISG expression in pSS, SLE and SSc. In light of IFN-targeting treatments, SiMoA could potentially be applied for patient stratification or high-throughput retrospective analysis of stored clinical trial material. References: [1]Rissin, D.M.; Kan, C.W.; Campbell, T.G.; Howes, S.C.; Fournier, D.R.; Song, L.; Piech, T.; Patel, P.P.; Chang, L.; Rivnak, A.J., et al. Single-molecule enzyme-linked immunosorbent assay detects serum proteins at subfemtomolar concentrations. Nat. Biotechnol. 2010, 28, 595-599. [2]Wilson, D.H.; Rissin, D.M.; Kan, C.W.; Fournier, D.R.; Piech, T.; Campbell, T.G.; Meyer, R.E.; Fishburn, M.W.; Cabrera, C.; Patel, P.P., et al. The Simoa HD-1 Analyzer: A Novel Fully Automated Digital Immunoassay Analyzer with Single-Molecule Sensitivity and Multiplexing. Journal of Laboratory Automation 2015, 21, 533-547. DOI: 10.1177/2211068215589580. [3]Rodero, M.P.; Decalf, J.; Bondet, V.; Hunt, D.; Rice, G.I.; Werneke, S.; McGlasson, S.L.; Alyanakian, M.A.; Bader-Meunier, B.; Barnerias, C., et al. Detection of interferon alpha protein reveals differential levels and cellular sources in disease. J. Exp. Med. 2017, 214, 1547-1555. DOI: 10.1084/jem.20161451. [4]Mathian, A.; Mouries-Martin, S.; Dorgham, K.; Devilliers, H.; Yssel, H.; Garrido Castillo, L.; Cohen-Aubart, F.; Haroche, J.; Hie, M.; Pineton de Chambrun, M., et al. Ultrasensitive serum interferon-alpha quantification during SLE remission identifies patients at risk for relapse. Ann. Rheum. Dis. 2019, 78, 1669-1676. DOI: 10.1136/annrheumdis-2019-215571. Disclosure of Interests: None declared