Cytomegalovirus infection/disease after hematopoietic stem cell transplantation

Cytomegalovirus (CMV) disease has historically been a main cause of death after allogeneic hematopoietic stem cell transplantation (HSCT). Since the introduction of prophylactic or preemptive therapy against CMV, the incidence of CMV disease has been successfully reduced. However, breakthrough CMV disease, particularly CMV gastrointestinal disease, remains one of the major infectious complications. Administration of an antiviral agent, ganciclovir, is often associated with myelotoxicity in HSCT recipients, and delayed immune reconstitution against CMV. Delayed immune reconstitution is a possible cause of the increasing incidence of late (more than 3 months after transplant) CMV disease after HSCT in this era of preemptive therapy. Foscarnet and valganciclovir are the available alternatives to intravenous ganciclovir. Foscarnet is not myelotoxic and has a toxicity profile different from ganciclovir. Valganciclovir, a prodrug of ganciclovir, has a higher bioavailability than oral ganciclovir and could be of clinical use, particularly in the outpatient setting or for patients requiring long-term antiviral therapy. Recent technological developments have enabled the visualization and isolation of CMV-specific T cells. Using these techniques, an individualized approach could be conducted based on each patient's immune reconstitution against CMV. In this review, we summarize the recent progress and current knowledge of CMV infection and disease after allogeneic HSCT.