Background: Inflammatory bowel diseases (IBD), encompassing Crohn's disease (CD) and ulcerative colitis (UC), exhibit unique immunological changes early in development. Although >300 IBD-specific antibody responses have been identified¹, systemic antibody epitope repertoires of preclinical IBD remain elusive. This study aimed to profile systemic antibody responses at unprecedented depth in individuals before and after the onset of IBD, aiming to identify preclinical disease biomarkers.

Methods: This study included individuals participating in the Lifelines Cohort Study, a large prospective population-based cohort study in the Netherlands including 167,000 individuals with longitudinal follow-up. Participants without IBD at baseline were screened for any reported IBD diagnosis during follow-up (2006-2021). Individuals who reported IBD during follow-up and with available serum samples were included. Samples at baseline (pre-diagnosis) and during follow-up (post-diagnosis) were used to profile antibody repertoires against 344,000 rationally selected microbial-, food-, and immune antigens using phage-display immunoprecipitation sequencing (PhIP-Seq).

Results: A total of 178 individuals with new-onset IBD were identified (Fig. 1). Median follow-up time until diagnosis was 3.9 (IQR: 3.4-4.3) years. Most individuals reported newly developed UC (n=123, 69.1%), followed by CD (n=44, 24.7%), and undetermined IBD (IBD-U, n=11, 6.2%). A total of 5,174 antibody responses were observed in 5-95% of participants. Fifty-nine antibodies were differentially abundant (FDR<0.05) pre-diagnosis vs. post-diagnosis (Fig. 2), 14 of which (24%) were previously reported as IBD-specific¹. Thirteen were more (22%) and 46 less (78%) frequently observed post-diagnosis. Those developing UC exhibited 33 differentially abundant antibody responses, while those with CD exhibiting only four (FDR<0.05). Individuals developing IBD exhibited lower frequencies of antibody responses against EBV-associated peptides post-diagnosis, e.g. Epstein-Barr nuclear antigen-1 (EBNA-1) and capsid protein V26, and varicella-zoster virus, alongside higher antibody responses against bacterial flagellins. Individuals developing UC showed elevated antibody responses mainly against viruses (e.g. human adenovirus C, enteroviruses B/C) and particular pathogenic bacterial species (e.g. pneumococcal histidine triad proteins) post-diagnosis compared to pre-diagnosis.

Conclusion: Distinct antibody responses appear years before IBD diagnosis, indicating potential involvement in pre-clinical disease development. Furthermore, post-diagnosis, lower frequencies of antibody responses against EBV may suggest reduced immunogenicity against this virus in early disease pathogenesis.

1. Bourgonje et al. Immunity. 2023.

Sergio Andreu-Sánchez

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