Background Diagnostic biomarkers are decision-making tools in clinical lab routine and are of growing importance for clinical management of patients. In autoimmune diseases, one class of biomarkers are autoantibodies (AAB) directed against human autoantigens. Apart from diagnostic antigens used in clinical routine, additional AAB reactivities to more than 100 human antigens are described in literature. Obviously, the autoimmune profile of humans covers a huge number of AABs, which display an enormous resource to identify novel marker candidates.
Objectives Here we describe a new screening platform SeroTag for screening of novel AABs in autoimmune diseases. By offering thousands of human antigens to serum samples of several autoimmune diseases a comprehensive landscape shall be drawn to identify diseases and disease subgroups according to their intrinsic, highly differentiated autoantibody pattern.
Methods SeroTag utilizes over 7,000 human proteins as antigen collection in bead-based suspension arrays (Luminex FlexMap 3D) to allow for high throughput serum sample processing with high accuracy, followed by standard and advanced data mining procedures. We screened over 4,000 serum samples from patients with autoimmune diseases such as SLE (n= >500), SSc (n= >250), RA (n= >500), and healthy individuals (n= >350) to confirm known and to discover novel autoantibodies. Recombinant antigens were covalently coupled to magnetic, color coaded beads and serum samples were incubated with 20 multiplex bead mixes each representing hundreds of antigens. Univariate and multivariate statistical analyses were performed to reveal significant antigens and to define correlation of antigens with clinical parameters and amongst themselves.
Results In SLE, SSc and RA novel autoantigens were discovered in independent discovery and validation studies. Antigens showing reproducible, significant reactivity compared to active and passive controls were selected in a stepwise marker refinement approach. Examples include BICD2 and KDM6B as novel antigens in SSc with 20–30% prevalence, TMPO and MVP in SLE with 15–25% prevalence, and several novel protein targets of anti-citrullinated peptide antibodies.
Conclusions Discovery approaches for autoantigens in autoimmune diseases show great promise to further detail the autoimmune landscape. SeroTag screening is a valuable tool for “omics”-type biomarker discovery and verification. Novel autoantigens were discovered and validated in RA, SLE, SSc which show potential for improved and earlier diagnosis, differential diagnosis, and disease subgrouping.
Disclosure of Interest P. Schulz-Knappe Employee of: Protagen AG, P. Budde Employee of: Protagen AG, H. Goehler Employee of: Protagen AG, H.-D. Zucht Employee of: Protagen AG, M. Schneider: None declared, S. Vordenbäumen: None declared, A. Lueking Employee of: Protagen AG, R. Brinks: None declared, J. Richter: None declared