Management of cytomegalovirus infection in inflammatory bowel diseases

Cytomegalovirus is a deoxyribonucleic acid virus that infects a large part of the human population; after primary infection, it develops a latent state and can be reactivated, notably after a decrease in host immune defences. In patients with inflammatory bowel diseases, cytomegalovirus is frequently involved, either as an agent of colitis or through local asymptomatic reactivation. Due to the immune context of inflammatory bowel diseases and to the immunosuppressive therapies that are used to treat them, cytomegalovirus entertains complex relationships with these diseases. Whereas Crohn's disease seems little impacted by cytomegalovirus, this agent interferes strongly with the natural progression of ulcerative colitis. While immune treatments have a clear influence on the occurrence of cytomegalovirus colitis in ulcerative colitis (favourable for steroids and cyclosporine and rather inhibitory for infliximab), the role of cytomegalovirus infection on ulcerative colitis is more debated with roles ranging from innocent bystander to key pathogen suggested. There is however growing evidence for a participation of intestinal cytomegalovirus infection in the resistance of ulcerative colitis to steroids and the investigation of cytomegalovirus infection in intestinal biopsies by immunohistochemistry or quantitative polymerase chain reaction assay is strongly recommended. In several studies, treatment of cytomegalovirus infection by ganciclovir was shown to restore the response to immunomodulatory therapies and even to prevent the need for colectomy. All of these recently acquired data need to be validated by randomised clinical trials conducted on a large panel of ulcerative colitis patients.