Human cytomegalovirus (HCMV) remains a cause of serious infectious complications after allogeneic transplantation of hematopoietic stem cells, especially in recipients of T cell depleted grafts. Here, we investigated the incidence of CMV-DNAemia in a cohort of 100 pediatric patients with leukemias and nonmalignant diseases, who received megadoses of CD34+ or CD133+ selected (and therefore highly T-cell depleted) grafts from matched unrelated or mismatched related (haploidentical) donors. Graft versus host disease was minimized with this approach (acute GvHD grade III-IV 5%) but T-cell recovery was delayed in most patients.

All patients received prophylactic acyclovir. PCR screening for CMV was performed weekly from leukocytes and plasma and additional antiviral treatment was started in the case of positive findings. Cumulative incidence of CM-DNAemia at day 100 was 29%. Seropositive recipients (n=44) had a significantly higher incidence of CMV-DNAemia than seronegative recipients (n=56) (64% vs. 0.05%; p=0.0001). In contrast, the incidence was not influenced by the serostatus of the donors (patients with seropositve donors (n=41): 33%; patients with seronegative donors (n=59): 28%; p=0.6). D+R+ pairs were not superior to D-R+ pairs. CMV related over-all mortality was<10%. Conclusions: the incidence of CMVDNAemia was remarkably low in our transplanted patients, despite profound T-cell depletion. Donor seropositivity had no influence. An explanation for these observations may be, that only purified stem cells were transplanted (representing less than 1% of the total cell number of an unmanipulated graft) and therefore, patients received a minimal number of potentially CMV infected leukocytes.We suppose, that this effect may counterbalance the transiently impaired T-cell function in our patients and supports the use of CD34+ or CD133 selection in order to prevent GvHD.

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