P038 Persistent inflammatory markers and deregulated immune response in clinical remission Crohn's disease patients treated with infliximab

Abstract

BACKGROUND: The development of Inflammatory Bowel Diseases (IBD) comprises an imbalance among gut microbiota, genetic susceptibility and exacerbated immune responses, which predispose to chronic inflammation in affected patients, who are usually treated with biological agents such as anti-tumor necrosis factor-α (TNF-α). Despite that, even during clinical remission periods, Crohn’s disease (CD) patients may still present endoscopic disease activity and possibly a residual systemic inflammatory response. Therefore, in this study we aimed to evaluate the responsiveness and immune profile of peripheral blood mononuclear cells (PBMC) of infliximab-treated patients, as well as the relationship between the altered responses and the clinical disease presentation. METHODS: We enrolled 20 healthy controls (HC) and 39 CD patients, which were classified according to the Harvey-Bradshaw Index (HBI) and Simple Endoscopic Score for Crohn’s Disease (SES-CD). All were using anti-TNF-α therapy (infliximab), including 61.5% in combination with Azathioprine. RESULTS: Although 94% of the patients were in clinical remission, 51.3% presented disease mucosal activity. Considering the Montreal classification, 12.8% had colonic disease, while 33.4% had ileal and 53.8% ileocolonic disease. Most the patients developed complications, being 20.5% stenosis and 35.9% structuring disease, while 59% had perianal disease. The immunophenotyping identification of PBMC by flow cytometry showed increased CD14+ and CD14++CD16+ monocytes in CD, indicating a tendency towards an inflammatory response because of the increased CD16 expression, along with augmented NKT and decreased NK cells and B lymphocytes. Considering the population of regulatory lymphocytes, CD patients had increased CD4+CD25+CTLA-4+ and CD4+CD25+FOXP3+ cells, together with augmented expression of CTLA-4 and FOXP3 in CD4+CD25- and CD4+CD25+ lymphocytes, indicating the raising of an important systemic counter regulatory response. Nevertheless, there was an increase in the inflammatory cytokine IL-6 in plasma and when PBMC was restimulated in vitro with bacterial-derived lipopolysaccharide (LPS), CD patients produced more TNF than healthy controls. Indeed, plasma dosage of LPS pointed to increased detection in CD samples, suggesting that these patients still present bacteria translocation to circulation. CONCLUSION(S): Even in clinical remission, CD patients had a relevant systemic inflammatory response together with increased regulatory population, probably elicited in an attempt to achieve immune-regulation after biological therapy. Financial support: Fapesp # 2017/08651-1.