Abstract
Human cytomegalovirus (HCMV) is a ubiquitous herpesvirus (the human herpesvirus 5) and an opportunistic pathogen that primarily infects HIV-positive and other immuno-compromised patients. Retrospective studies in the field of inflammatory bowel disease (IBD) have suggested a relationship between a concomitant colonic HCMV infection and poor outcomes in patients with an ulcerative colitis (UC) due to the presence of HCMV in surgical specimens of patients with a toxic megacolon or a steroid-resistant UC. Therefore, gastroenterologists have focused on the contribution of HCMV infections in the exacerbation of UC. Numerous studies have addressed the benefits of treating colonic HCMV reactivation in UC using an antiviral treatment. However, its clinical relevance remains uncertain as only a few prospective studies have assessed the direct relationship between clinical outcomes and the viral load of HCMV in colonic tissues. HCMV reactivation can be triggered by inflammation according to fundamental research studies. Thus, optimal control of intestinal inflammation is essential for preventing an HCMV reactivation in the intestinal mucosa. Indeed, several reports have indicated the effectiveness of an anti-tumor necrosis factor-alpha (TNFα) treatment in patients with an active UC and concomitant HCMV infections. In this review, we describe the mechanism of HCMV reactivation in UC cases and discuss the current issues regarding diagnosis and treatment of HCMV infections in UC patients.
Highlights
Human cytomegalovirus (HCMV), a double-stranded DNA virus belonging to the family Herpesviridae, is generally contracted during childhood and can persist as a lifelong latent infection
The treatment of HCMV infection in patients with active Ulcerative colitis (UC) is complicated by the difficulty experienced in exactly distinguishing an HCMV reactivation from HCMV colitis, as inflammatory conditions in the colonic mucosa of UC patients may contribute to an HCMV reactivation [23,31]
The diagnosis continues to be based on HCMV detection in histopathology, but we believe that the quantitative polymerase chain reaction (PCR) method is a promising alternative approach to better define the extent of an HCMV reactivation in histological negative cases
Summary
Human cytomegalovirus (HCMV), a double-stranded DNA virus belonging to the family Herpesviridae, is generally contracted during childhood and can persist as a lifelong latent infection. HCMV reactivation is controlled by specific antibodies and the CD8-positive T cells (Figure 1) This defense mechanism is disrupted in an immunosuppressed host and HCMV is reactivated, causing damage to multiple organs, including the gastrointestinal tract. Inflammatory cytokines, including TNF-α, are important for the pathophysiology of IBD and the reactivation of HCMV in the intestinal tract by promoting the differentiation of HCMV latently-infected cells and the virus growth. The existence of ulcerative lesions in UC patients refractory to immunosuppressive therapies may suggest the possibility of HCMV infection Endoscopic findings such as punched-out ulcers, longitudinal ulcers, diffuse mucosal defect, and geographic ulcers (Figure 2) have been reported to be characteristics of UC complicated by HCMV infection [13,14]. We should know the advantages and disadvantages of each diagnostic methods (Table 1)
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