P036 Expression of CD69 on peripheral lymphocytes predicts treatment response in Acute Severe ulcerative colitis

Abstract

Background and Aims Disease severity in acute severe ulcerative colitis (ASUC) is currently assessed using clinical and endoscopic indices, and treatment response is determined following a trial of drug therapy. Immune profiling potentially offers new methods of classifying disease activity to determine the likelihood of a response to therapy. CD69 is a marker of lymphocyte activation and recent work implicates it in the regulation of intestinal inflammation, with CD69 expression on mucosal associated invariant T (MAIT) cells correlating with IBD disease activity. We aimed to identify biomarkers of steroid and infliximab (IFX) response in ASUC by immune profiling of peripheral blood and intestinal mucosa. Methods: Peripheral blood and mucosal biopsies were collected from 44 patients with ASUC on admission and 10 healthy controls. Clinical response to intravenous steroids and IFX salvage therapy was correlated with peripheral lymphocyte CD69 expression, and membrane TNF (mTNF) expression on monocytes measured by flow cytometry, and mucosal cytokine gene expression by RT-PCR. Results: ASUC patients had a peripheral deficiency of MAIT, natural killer (NK), NKT and Th1 cell proportions compared to healthy controls. CD69 expression on these lymphocytes correlated with disease activity; with CD69 expression on MAIT and NK cell correlating more consistently across clinical, biochemical and endoscopic indices compared to CRP or albumin alone. CD69 expression on MAIT, NK, NKT, Th1 and Th2 cells was significantly higher in steroid non-responders and was predictive of steroid non-response [MAIT (AUROC 0.76, P=0.01, cutoff 27.55%), NK (AUROC 0.81, P<0.01, cutoff 16.75%), NKT (AUROC 0.71, P=0.04, cutoff 33.1%), Th1 (AUROC 0.73, P=0.02, cutoff 1.65%) and Th2 (AUROC 0.81, P<0.01, cutoff 7.06%)]. Elevated Th2 CD69 expression also predicted IFX non-response (AUROC 0.74, P=0.04, cutoff 11.45%) and was an independent immunological predictor of treatment response on multivariate logistic regression. IFX non-responders had a non-significant trend towards higher mTNF expression on monocytes and subsets. Monocyte subset proportions and concomitant mTNF expression did not correlate with steroid response status. Mucosal TGFb expression in IFX non-responders was significantly higher compared to responders (p=0.03). Mucosal TNF expression was not associated with treatment response or disease activity. Conclusion: In ASUC, CD69 expression on key peripheral lymphocyte subsets is a novel biomarker of disease severity and has the potential to identify those at risk of treatment failure. Future work is required to discern the function of CD69 in ASUC, to assess why elevated expression is associated with treatment failure, and whether CD69 represents a potential therapeutic target in the future.