Effects of High Cytomegalovirus DNA Load on Immune Reconstitution and Clinical Outcomes after Single Unrelated Cord Blood Transplantation

Abstract

To investigate the effects of cytomegalovirus (CMV) DNA load on immune reconstitution and clinical outcomes of patients after unrelated cord blood transplantation (UCBT). Eight-color flow cytometry was used to dynamically monitor the changes of peripheral blood lymphocyte subsets of 41 patients at one year after UCBT, and 10 healthy volunteers were enroled as controls. Patients were divided into two groups according to the DNA load of CMV (DNA copies <1000/ml and DNA copies ≥1000/ml). Comparative analyse of the effect of CMV DNA load on lymphocyte subsets and transplantation outcomes were carried out after transplantation. The high CMV DNA load group showed a faster and expanded T cell reconstitution, and the differences between the two groups were statistically significant at one and nine months after transplantation (0.38×109 /L vs 0.25×109 /L, P=0.015 and 2.53×109 /L vs 1.36×109 /L, P=0.006, respectively). Further analysis of T cell subsets suggested that CD8+ T cells presented a higher and faster recovery in the high DNA load group, and the differences between the two groups were statistically significant at one and nine months after transplantation (0.20×109 /L vs 0.10×109 /L, P=0.038 and 1.62×109 /L vs 0.68×109 /L, P=0.003, respectively). In addition, there were no significant differences in levels of B cells, regulatory B cells and NK cells between the two groups. Outcomes after one- and a-half-year transplantation showed that there were no significant difference in relapse, non-relapse mortality and overall survival between the high and the low DNA load groups (7.7% vs 7.5%) (P=0.900) (15.4% vs 21.4%) (P=0.686) and (76.9% vs 78.6%) (P=0.889) respectively. The high CMV DNA load induces a faster and long-lasting expansion of T cells, mainly as the expansion of CD8+ T cells after UCBT. Besides, under the current pre-emptive treatment of CMV, the high CMV DNA load does not affect the early survival of patients with acute myeloid leukemia after UCBT.