Control of Cytomegalovirus Viremia after Allogeneic Stem Cell Transplantation: A Review on CMV-Specific T Cell Reconstitution

Abstract Recipients of allogeneic stem cell transplantation (alloSCT) are at risk for reactivation of endogenous herpesviruses due to profound and prolonged T cell deficiency following conditions such as GVHD, immunosuppression and/or T cell depletion. Reactivation of endogenous CMV is the most frequently occurring herpesvirus reactivation following alloSCT. Antiviral medication is often used in pre-emptive treatment strategies initiated when increases in CMV viral loads are detected as a result of active reactivation of the virus. Despite pre-emptive antiviral treatment, the incidence of CMV disease in CMV seropositive alloSCT patients is still 10% at 1 year following alloSCT. This illustrates the necessity for adequate CMV specific T cell immunity for long-term control of CMV and prevention of CMV disease. In this review, we analyzed the available studies on the influence of donor CMV status on CMV specific T cell reconstitution and CMV disease. Furthermore, we reviewed the available studies on the safety and efficacy of adoptive transfer of donor CMV specific T cells for the prevention and treatment of CMV disease following alloSCT, including studies on adoptive transfer of third-party CMV specific T cells as a possible alternative when donor T cells are not available.