Laird, Renée M.

Abstract Background Biomarkers for predicting the development of Ulcerative Colitis (UC) and disease-related complications are lacking. Anti-integrin αvβ6 IgG autoantibodies (anti-αvβ6) have been recently described in patients diagnosed with UC. Here, we sought to determine if anti-αvβ6 autoantibodies predate UC development and to study associations between anti-αvβ6 and disease outcomes in newly diagnosed UC patients. Methods In a unique pre-clinical IBD cohort from the PRoteomic Evaluation and Discovery in an IBD Cohort of Tri-service Subjects (PREDICTS), anti-αvβ6 were measured in longitudinal pre-diagnosis serum samples from 82 subjects who later developed UC as well as in 82 matched subjects that did not develop IBD (HC). Sample A was at the time of UC diagnosis, Sample B was at a median of 2 years before Sample A, Sample C was at a median of 4 years before Sample A and Sample D was at a median of 10 years before Sample A. In a distinct, external validation cohort (the Crohn’s and Colitis Canada Genetics Environment Microbial (GEM) Project), we tested samples from 12 subjects who later developed UC and compared those with 49 matched subjects who remained asymptomatic. Further, anti-αvβ6 were measured in 2 incident IBD cohorts (COMPASS, n=55 and OSCCAR, n=104 UC subjects) and associations between anti-αvβ6 and adverse UC-outcomes were defined using Cox proportional-hazards model. Results Anti-αvβ6 were significantly higher in the PREDICTS cohort among individuals who developed UC compared to HC up to 10 years prior to diagnosis (Figure 1A). The anti-αvβ6 seropositivity was 12.2% 10 years before diagnosis and increased to 52.4% at the time of diagnosis in subjects who developed UC compared with 2.7% in controls across the 4 timepoints. Additionally, the predictive performance of anti-αvβ6 autoantibodies as assessed via area under the receiver operator curves (AUROC) with 10-fold cross validation was at least 0.8 up to 10 years before diagnosis (Figure 1B). Elevated levels of anti-αvβ6 in pre-clinical UC samples were further validated in the GEM cohort (Figure 1C). Finally, high anti-αvβ6 were associated with a composite of adverse UC-outcomes including hospitalization, disease extension, colectomy, systemic steroid use and/or escalation to biologic therapy in both incident cohorts (Figure 1D). Conclusion Anti-integrin αvβ6 autoantibodies precede the clinical diagnosis of UC by up to 10 years and are associated with adverse UC-related outcomes.

Abstract Background Crohn’s disease (CD) is a heterogenous, chronic inflammatory disorder driven by a combination of genetic, environmental, and microbiota-dependent risk factors. Mononuclear phagocytes (MNP) are crucial cells that maintain intestinal homeostasis. An important cytokine for MNP survival and function is granulocyte-macrophage colony stimulating factor (GM-CSF). Interestingly, several studies reported CD-associated genetic risk variants within the GM-CSF receptor and its downstream signaling components. Furthermore, high titers of autoantibodies specific to GM-CSF can be detected in CD patients. Taken together, this data suggests an important role for GM-CSF in abrogation of CD development in a subgroup of patients. Aims This study sought to investigate the function of GM-CSF autoantibodies in CD. Methods We retrospectively quantified and characterized GM-CSF autoantibodies in sera of 220 CD, 200 ulcerative colitis (UC) patients, and 220 healthy controls (HC) sampled at 3 time points prior to disease diagnosis and one time point after diagnosis. ELISA was used to determine GM-CSF autoantibody titers and isotypes followed by in vitro multiplexed mass cytometry (CyTOF) neutralization assays on peripheral blood mononuclear cells. Flow cytometry and CyTOF were used to map the profile of immune cells isolated from inflamed and non-inflamed CD mucosa. Results Our data demonstrates that GM-CSF autoantibodies are specific to CD, significantly elevated up to 7 years prior to diagnosis of disease, and correlate with disease location, severity, and complications at the time of diagnosis. Moreover, in contrast to GM-CSF autoantibodies in pulmonary alveolar proteinosis patients, CD-associated autoantibodies neutralize GM-CSF via specific recognition of post-translational modifications (PTM), affecting MNP function. Removal of PTM enabled GM-CSF to escape autoantibody binding and restored MNP response to GM-CSF in the presence of neutralizing antibodies, indicating a potential therapeutic avenue. Furthermore, we identified group 3 innate lymphoid cells (ILC3) as a major source of GM-CSF in the healthy intestinal tract, suggesting intriguing crosstalk of MNP and ILC3 across the GM-CSF-GM-CSFR axis. Conclusions Our results identify GM-CSF autoantibodies as predictive serological biomarker for CD in a subgroup of patients presenting with severe and complicated form of disease at the time of diagnosis. The presence of GM-CSF autoantibodies precedes the onset of CD by several years and likely abrogates homeostatic immune cell crosstalk involving ILC3 and MNP, suggesting the development of a pre-diseased state in CD patients. Funding Agencies CIHRDr. Edward Ketchum Graduate Scholarship