Protein-based Immunome Wide Association Studies (PIWAS) for the discovery of significant disease-associated antigens

Abstract

Identification of the antigens associated with antibodies is vital to understanding immune responses in the context of infection, autoimmunity, and cancer. Discovering antigens at a proteome scale could enable broader identification of antigens that are responsible for generating an immune response or driving a disease state. Although targeted tests for known antigens can be straightforward, discovering antigens at a proteome scale using protein and peptide arrays is time consuming and expensive. We leverage Serum Epitope Repertoire Analysis (SERA), an assay based on a random bacterial display peptide library coupled with NGS, to power the development of Protein-based Immunome Wide Association Study (PIWAS). PIWAS uses proteome-based signals to discover candidate antibody-antigen epitopes that are significantly elevated in a subset of cases compared to controls. After demonstrating statistical power relative to the magnitude and prevalence of effect in synthetic data, we apply PIWAS to systemic lupus erythematosus (SLE, n=31) and observe known autoantigens, Smith and Ribosomal P, within the 22 highest scoring candidate protein antigens across the entire human proteome. We validate the magnitude and location of the SLE specific signal against the Smith family of proteins using a cohort of patients who are positive by predicate anti-Sm tests. Collectively, these results suggest that PIWAS provides a powerful new tool to discover disease-associated serological antigens within any known proteome. Author SummaryInfection, autoimmunity, and cancer frequently induce an antibody response in patients with disease. Identifying the protein antigens that are involved in the antibody response can aid in the development of diagnostics, biomarkers, and therapeutics. To enable high-throughput antigen discovery, we present PIWAS, which leverages the SERA technology to identify antigens at a proteome- and cohort-scale. We demonstrate the ability of PIWAS to identify known autoantigens in SLE. PIWAS represents a major step forward in the ability to discover protein antigens at a proteome scale.