Cytomegalovirus and inflammatory bowel diseases, with a special focus on its role in ulcerative colitis

Cytomegalovirus (CMV) infects approximately 50 % of adults in France and persists lifelong as a latent agent in different organs, including the gut. A close relationship is observed between inflammation that favors viral expression, and viral replication that modulates inflammation. In this context, CMV colitis may impact the prognosis of patients suffering from inflammatory bowel diseases (IBD), and notably those with ulcerative colitis (UC). In UC, the mucosal inflammation in link with Th2 cytokines, together with immunomodulatory drugs used for controlling flares-up, favors viral reactivation within the gut, which increases mucosal inflammation; it results in an important risk of impairing corticoid and immunosuppressor efficacy (the probability of steroid resistance is multiplied by more than 20 in case of CMV colitis), precipitating the need for colectomy. This review emphasizes the virological tools that are recommended for exploring CMV colitis during IBD and underlines the interest of using ganciclovir for treating flares-up associated to CMV colitis in UC patients.