Autoantibody Profiling in Ulcerative Colitis: Identification of Early Immune Signatures and Disease-Associated Antigens for Improved Diagnosis and Monitoring

Ulcerative colitis (UC) is a major form of inflammatory bowel disease (IBD) characterised by chronic immune-mediated inflammation. While serological biomarkers for IBD diagnosis and differentiation have been explored, autoantibody-based profiling remains underdeveloped. This study aimed to elucidate antibody signatures in manifested and pre-diagnostic UC patients compared to controls using a high-content protein microarray. Serum and plasma samples from manifested and pre-diagnostic UC cohorts were analysed using AIT's 16k protein microarray, presenting 6369 human proteins. The pre-diagnostic cohort, consisting of 33 UC cases and 33 controls, included longitudinal samples collected before diagnosis, while the severe UC cohort, comprising 49 severe UC patients and 23 controls, included individuals undergoing treatment. Immunoglobulin G (IgG) autoantibody reactivity was assessed to identify differentially reactive antigens (DIRAGs) linked to UC onset, disease progression, and activity. In manifested UC, 691 DIRAGs showed higher reactivity in cases. In the pre-diagnostic cohort, 966 DIRAGs were identified, with 803 antigens exhibiting increased reactivity in cases. Longitudinal analysis revealed 1371 DIRAGs, with 1185 showing increased reactivity closer to diagnosis when comparing samples collected 4-11 months before UC diagnosis to earlier time points 9-24 months prior, highlighting potential early biomarkers. A significant overlap of 286 antigens, corresponding to 41 percent of identified DIRAGs, was observed between severe and pre-diagnostic UC datasets, with an odds ratio of 3.8 and a p-value below 2.2 x 10-16, confirming reliability and biological relevance. Additionally, 21 antigens correlated with simple clinical colitis activity index (SCCAI) scores. Reactome pathway analysis identified 49 pathways associated with DIRAGs in pre-diagnostic UC, distinct from 24 pathways in manifested UC, with an overlap of five key pathways related to protein folding, immune regulation, and viral infection, reflecting differences in disease onset and manifestation. Autoantibody profiling reveals early immune signatures in UC, offering novel biomarkers for preclinical diagnosis and disease monitoring. The overlap between pre-diagnostic and manifested UC antigenic profiles reinforces their biological relevance, linking them to molecular pathology. These findings highlight antibody profiling as an additional omics layer, paving the way for new diagnostic and therapeutic strategies in UC management.