Protective Effects of Cytomegalovirus DNA Copies ≧1000/mL for AML Patients in Complete Remission After Single Cord Blood Transplantation

INTRODUCTION: Current consensus recommends a protective effect of cytomegalovirus (CMV) infection on relapse after peripheral blood or bone marrow hematopoietic stem cell transplantation. However, in cord blood transplantation (CBT), studies of CMV infection, especially CMV viral load, on relapse are limited. PATIENTS AND METHODS: Wct e retrospectively analyzed the effect of CMV infection on 3-year outcomes in 249 AML patients according to CMV DNA load (DNA copies <1000/mL and DNA copies ≧1000/mL) within 100 days after CBT. Furthermore, eight-colour flow cytometry was used to detect peripheral blood lymphocyte subsets in 38 patients who received CBT in the last year, and 10 healthy volunteers were included as controls. RESULTS: The results showed that CMV DNA load did not affect the cumulative incidence of relapse in the whole study population. However, in patients with complete remission status before transplantation, the high CMV DNA load group showed a significantly reduction of relapse than the low CMV DNA load group (3.9% vs 14.6%, p=0.012, respectively), which was confirmed by multivariate analysis (HR 0.23; 95% CI, 0.07–0.73, p = 0.012). Surprisingly, high or low CMV DNA load did not significantly affect non-relapse mortality or overall survival (18.0% vs 17.0%, p=0.777 and 79.0% vs 74.6%, p=0.781, respectively). Besides, the absolute number of CD8(+) T cells were increased in the high CMV DNA load group compared with the low DNA load group 1 month after CBT (0.20×10(9)/L vs 0.10×10(9)/L, p=0.021, respectively). CONCLUSION: DNA copies ≧1000/mL for AML patients in complete remission was associated with a lower incidence of relapse after CBT, which might partly result from the expansion of CMV-related CD8(+) T cells.