Autologous Cytomegalovirus (CMV) Specific CD8+ T Cells as Treatment for CMV Reactivation

Allogeneic Hematopoietic Stem Cell transplantation (allo-SCT) remains the only curative approach for a number of patients with hematological malignancies. However, the use of allo-SCT can expose patients to prolonged periods of immunosupression during which time viral infections can be a significant cause of morbidity and mortality. Human cytomegalovirus (CMV) infection and reactivation still represents one of the most important and lifethreatening complications in immunocompromised patients. Prophylaxis or early treatment with antiviral drugs after CMV reactivation have reduced the mortality related to this complication. However, the antiviral drugs have many side-effects and are costly. Furthermore, CMV infection refractory to antiviral treatment after alloSCT is associated with a high mortality. A number of studies have shown the efficacy of selecting Tcells against the virus from the donor and infusing them into the recipient (adoptive transfer of immunity) to prevent or treat CMV reactivation. However this approach relies on the donor having preexisitng immunity to CMV (50% of the healthy population is CMV seronegative and therefore have no preexisting immunity against CMV). We propose an alternative approach to collect CMV specific Tcells from the seropositive recipient prior to transplantation; the autologous CMV specific T cells will then be infused back into the recipient at the time of CMV reactivation post-transplant. This approach is especially relevant where the donor is CMV seronegative or unavailable or following the use of cord blood transplant where there is no memory T cell response to CMV.