A role for CXCR3 ligands as biomarkers of post-operative Crohn's disease recurrence.

BACKGROUND AND AIMS Crohn's disease (CD) recurrence following ileocolic resection (ICR) is common. We sought to identify blood-based biomarkers associated with CD recurrence. METHODS CD patients undergoing ICR were recruited across six centres. Serum samples were obtained at post-operative colonoscopy. A multiplex immunoassay was used to analyse 92 inflammation-related proteins (Olink Proteomics). Bayesian analysis was used to identify proteins associated with increasing Rutgeerts score. Identified proteins were employed in receiver operating characteristic (ROC) analysis to examine ability to identify CD recurrence (Rutgeerts score ≥ i2). Existing single cell data was interrogated to further elucidate the role of identified proteins. RESULTS Data from 276 colonoscopies in 213 patients were available. Median time from surgery to 1st and 2nd colonoscopy was 7 (IQR 6-9) and 19 (IQR 16-23) months, respectively. Disease recurrence was evident at 60 (30%) first and 36 (49%) second colonoscopies. Of 14 proteins significantly associated with Rutgeerts score, the strongest signal was seen for CXCL9 and MMP1. Among patients on anti-TNF, CXCL9 and CXCL11 were most strongly associated with Rutgeerts score. Both are CXCR3 ligands. Incorporation of identified proteins into ROC analysis improved the ability to identify disease recurrence as compared to C-reactive protein alone; area under the curve (AUC) 0.75 (95% CI: 0.66-0.82) vs. 0.64 (95% CI 0.56-0.72), p=0.012. Single cell transcriptomic data provide evidence that innate immune cells are the primary source of identified proteins. CONCLUSIONS CXCR3 ligands are associated with CD recurrence following ICR. Incorporation of novel blood-based candidate biomarkers may aid identification of CD recurrence.