We analyzed the incidence, etiology, risk factors, and clinical management of hemorrhagic cystitis (HC) in 102 children who underwent allogeneic stem cell transplantation: 28 from matched siblings, 57 from unrelated donors, and 17 from mismatched relatives. Conditioning regimens consisted of high-dose chemotherapy (n=83) or total body irradiation (n=19). In all children, urine and plasma were prospectively screened for human polyomavirus (HPV; BK virus [BKV] and JC virus [JCV]) or adenovirus (AdV) DNA with a polymerase chain reaction-based assay. Viral DNA was detected in the urine of 56 children (54.9%): BKV in 48 (47%), JCV in 4 (3.9%), and AdV in 4 (3.9%). HC occurred in 26 children (25.5%), and viruria was detected in all of them: BKV in 21 (80.8%), AdV in 4 (14.4%), and JCV in 1 (3.8%). All patients with AdV viruria developed HC. The cumulative incidence of HC in patients with HPV viruria was 0.43. The only significant risk factor for HC in patients with HPV-positive urine was conditioning with high-dose chemotherapy. Twenty-two children were treated with cidofovir, with no significant toxicity. In all treated patients but 1, the clinical symptoms were moderate, and no HC-related death was observed. We conclude that virus-induced HC is a frequent complication after allogeneic hematopoietic cell transplantation. Treatment with cidofovir is feasible, and further studies are warranted to evaluate its activity in HC mediated by BKV or JCV.

Summary. Immune reconstitution was studied prospectively in 66 children who underwent 77 haematopoietic cell transplantations (HCT): 46 autologous HCTs in 39 patients and 31 allogeneic HCTs in 27 patients. We studied the dynamic analysis of immune recovery with regard to potential factors affecting its speed, including age, type of HCT, diagnosis, graft-versus-host disease (GvHD) and cytomegalovirus (CMV) infection reactivation. Absolute counts of different lymphocyte subsets and immunoglobulin serum levels were determined in peripheral blood of patients on d )7 and +16, and then at various intervals up to 24 months post transplant. Common patterns of immune recovery after both allogeneic and autologous HCT were identified: (i) CD4 + CD45RO + peripheral T-cell expansion on d +16; (ii) inverted CD4 + :CD8 + ratio from d +30 onwards; (iii) rapid natural killer (NK) cell (CD16 ± CD56 + ) count normalization. We observed prolonged T-cell lymphopenia (CD3 + , CD3 + CD4 + , CD4 + CD45RA + ) until 24 months after autologous HCT, whereas in the allogeneic setting CD3 + CD4 + cells, including naive CD45RA + cells, returned to normal values at 9 months post transplant. Age > 10 years and coexistence of GvHD and CMV reactivation were associated with a substantial delay in T-(CD4 + , including CD45RA + ) and B-cell recovery after allogeneic HCT. Multidrug GvHD prophylaxis resulted in impaired T-(CD4 + , CD4 + CD45RA + ) and B-cell reconstitution only in the early phase after allogeneic HCT (up to 4 months). Our results demonstrated that T-cell recovery was severely impaired in children after autologous HCT. It should be emphasized that specific approaches to enhance immune reconstitution are necessary to control minimal residual disease and avoid the risk of infectious complications in the autologous setting. Thymic involution after allogeneic HCT seems to be associated with age and coexistence of GvHD and CMV reactivation.

The aim of our study was to compare the results of unrelated donor (UD) peripheral blood stem cell transplantation versus UD bone marrow transplantation and to analyze the impact of infused CD34(+) and CD3(+) cell doses on survival and incidence of severe graft-versus-host disease (GVHD) in 187 children who underwent UD hematopoietic cell transplantation with the use of in vivo T cell depletion (antithymocyte globulin or CAMPATH-1H). HLA typing was performed at the "high-resolution" level. Patients receiving > or =10 x 10(6) CD34(+) cells/kg and > or =4 x 10(8) CD3(+) cells/kg had better overall and disease-free survival. Multivariate analysis has shown that both infused CD34(+) cell dose <10 x 10(6)/kg and CD3(+) cell dose <4 x 10(8)/kg were independent risk factors for mortality (relative risk [RR] 1.8 and 1.71, P = .009 and .016, respectively). Regarding disease-free survival, multivariate analysis has revealed another independent risk factor for poor outcome apart from the 2 earlier-mentioned cell doses, which was the use of donors mismatched at 2 HLA antigens or 3 HLA allele/antigens (RR 2.5, P = .004). In age groups 0-10 years and 10-20 years, CD34(+) cell doses higher than the age-adjusted median dose clearly favored survival. Higher infused doses of CD34(+) and CD3(+) cells did not result in an increased rate of severe GVHD. The use of mismatched donors was the only independent risk factor for the incidence of severe acute GVHD (RR 2.2, P = .046). The report demonstrates for the first time in a pediatric cohort, that higher doses of transplanted CD34(+) and CD3(+) cells lead to an improved survival without an increased risk of severe GVHD. The study findings may be limited to the population of patients receiving in vivo T cell depletion, which is now broadly used in unrelated donor setting in Europe.

This retrospective analysis evaluated 51 children (0.7-17 years; median eight) with high-risk or advanced hematological malignancies, including 18 (35%) patients undergoing second/third hematopoietic SCT (allo-HSCT), not eligible for standard myeloablative regimens and transplanted from matched sibling (MSD) (n ¼ 24) or matched unrelated (MUD) (n ¼ 27) donors. Preparative regimens were based on treosulfan (TREO) i.v., a structural analog of BU, given at total dose of 30 g/m 2 (n ¼ 21) or 36-42 g/ m 2 (n ¼ 30) in combination with, fludarabine, cyclophosphamide, melphalan and/or VP-16 according to diagnosis, and risk factors. Deaths due to early regimenrelated toxicity (RRT) did not occur. Nonrelapse mortality was 8% at 1 year and 16% after 4 years. Myeloid engraftment was achieved in 94%, complete donor chimerism in 90% of patients. A 4-year incidence of relapse was 24%, and was significantly lower after MUD-HSCT (8%) than after MSD-HSCT (39%), but similar in children undergoing first (28%) or second/third HSCT (17%). A 4-year disease-free survival was 61%, but it was significantly better in myeloid (73%), than in lymphoid malignancies (41%). Thus, children with high-risk and advanced hematological malignancies and high-risk of life-threatening RRT can be transplanted effectively and safely using TREO-based regimens. Particularly favorable results were achieved in myeloid malignancies and in children undergoing second HSCT.

After stem cell transplantation, human patients are prone to life-threatening opportunistic infections with a plethora of microorganisms. We report a retrospective study on 116 patients (98 children, 18 adults) who were transplanted in a pediatric bone marrow transplantation unit. Blood, urine and stool samples were collected and monitored for adenovirus (AdV) DNA using polymerase chain reaction (PCR) and real-time PCR (RT-PCR) on a regular basis. AdV DNA was detected in 52 (44.8%) patients, with mortality reaching 19% in this subgroup. Variables associated with adenovirus infection were transplantations from matched unrelated donors and older age of the recipient. An increased seasonal occurrence of adenoviral infections was observed in autumn and winter. Analysis of immune reconstitution showed a higher incidence of AdV infections during periods of low T-lymphocyte count. This study also showed a strong interaction between co-infections of AdV and BK polyomavirus in patients undergoing hematopoietic stem cell transplantations.