ALBERT

Description: Key Points Adoptive transfer of TH-1 cells is a safe and effective treatment of refractory AdV infection after stem cell transplantation. AdV-related mortality was 9.5% in patients with a response to ACT (overall survival 71%) compared with 100% mortality in nonresponders.

Description: The chromosomal translocation t(4;11) marks infant acute lymphoblastic leukemia associated with a particularly dismal prognosis. The leukemogenic role of the corresponding fusion gene MLL-AF4 is not well understood. We show that transient inhibition of MLL-AF4 expression with small interfering RNAs impairs the proliferation and clonogenicity of the t(4; 11)–positive human leukemic cell lines SEM and RS4;11. Reduction of mixed-lineage leukemia (MLL)–ALL-1 fused gene from chromosome 4 (AF4) levels induces apoptosis associated with caspase-3 activation and diminished BCL-XL expression. Suppression of MLL-AF4 is paralleled by a decreased expression of the homeotic genes HOXA7, HOXA9, and MEIS1. MLL-AF4 depletion inhibits expression of the stem-cell marker CD133, indicating hematopoietic differentiation. Transfection of leukemic cells with MLL-AF4 siRNAs reduces leukemia-associated morbidity and mortality in SCID mice that received a xenotransplant, suggesting that MLL-AF4 depletion negatively affects leukemia-initiating cells. Our findings demonstrate that MLL-AF4 is important for leukemic clonogenicity and engraftment of this highly aggressive leukemia. Targeted inhibition of MLL-AF4 fusion gene expression may lead to an effective and highly specific treatment of this therapy-resistant leukemia.

Description: About 50% of all infants suffering from acute lymphoblastic leukaemia (ALL) show the translocation t(4;11)(q21;q23) which creates the fusion genes MLL/AF4 and AF4/MLL. This reciprocal translocation identifies a therapy resistant form of leukaemia with a poor prognosis. In order to gain a better insight into the molecular mechanisms of t(4;11) leukaemias we used the two ALL cell lines SEM and RS4;11, both harbouring the t(4;11) translocation, however with different fusion sites. Specific small interfering RNAs (siRNAs) against the two fusion site variants of the MLL/AF4 fusion transcript were designed and transfected into the respective cells via electroporation, using very mild conditions. Serial electroporations at two-day intervals resulted in sustained depletion of the MLL/AF4 transcript up to 70–80%, and depending on the experimental setup, cells were analysed after two or three electroporations. Knock-down of MLL/AF4 resulted in strong inhibition of proliferation and clonogenicity in the two t(4;11)-positive cell lines SEM and RS4;11, along with induction of apoptosis. MLL/AF4 depletion resulted in a 65% decrease in telomerase activity in both SEM and RS4;11 cells, with telomerase reverse transcriptase (TERT) expression being reduced twofold on both transcript and protein levels. Notably, TERT reduction was even stronger (90% depletion) when apoptosis caused by MLL/AF4 knock-down was suppressed with the caspase inhibitor zVAD. In contrast, levels of the RNA component of the telomerase, TERC, were not affected by MLL/AF4 knock-down. Additionally, MLL/AF4 knock-down was associated with reduced expression of several members of the HOXA gene cluster, HOXA6 (65% reduction), HOXA7 (85% reduction), HOXA9 (60% reduction) and HOXA10 (75% reduction). Interestingly, siRNA-mediated knock-down of the MLL/AF4 target gene HOXA7 also induced apoptosis and resulted in a 70% decrease of TERT levels in two t(4;11) positive cell lines without affecting MLL/AF4. Chromatin immunoprecipitation assays revealed HOXA7 binding to the promoter of TERT. Therefore, MLL/AF4 regulates TERT expression, at least in part, via HOXA7. These data suggest that t(4;11) positive cells with substantially lower TERT expression undergo apoptosis, and that TERT may play an antiapoptotic role in t(4;11) positive ALL. Furthermore, these studies identify TERT as a putative new therapeutic target in this therapy-resistant infant leukaemia.

Description: Profound depletion of T and B cells is a fundamental prerequisite for haploidentical transplantation. Here, we compare hematopoietic engraftment and occurrence of GvHD after two different positive selection procedures (with anti-CD34 coated or anti-CD133 coated beads) and after a direct depletion procedure with CD3/CD19 coated microbeads in children with leukemias (ALL, AML, CML) and lymphomas. Median purity of stem cells was comparable after CD34+ selection and CD133+ selection, whereas stem cells were only slightly enriched after CD3+/CD19+ depletion (97.5%, 93.4% and 1.02%). Indirect depletion of T cells was better after CD34+ selection than after CD133+ selection (4.1log vs. 3.75log, p

Description: 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

Description: Primary hemophagocytic lymphohistiocytosis (HLH) is a severe inflammatory condition that is caused by an abnormal accumulation of activated macrophages. The common NK- and cytotoxic T-cell dysfunction in HLH has been related to genetic defects of vesicle transport and apoptosis. Here, we identify a novel form of hereditary HLH that is related to and possibly caused by a homozygous missense mutation (G139V) of the active centre of heme oxygenase-1 (HO-1). The clinical picture of this male patient is characterized by persistent, severe microcytic hemolytic anemia without hyperbilirubinemia since birth. In the second year of life, the clinical syndrome of HLH developed with persistent fever, marked hepatosplenomegaly, thrombocytopenia, hyperferritinemia, hypertriglyceridemia, and elevated levels of soluble CD25. Liver histology showed marked lympho- and erythrophagocytosis, which confirmed the diagnosis of HLH. The clinical syndrome responded well to immunosuppressive treatment with etoposide, dexamethasone and cyclosporine A. PRF1, UNC13-D and STX11 mutations were excluded. Functional analysis of NK-activity showed only slightly decreased killing activity with normal responses of NK-cells to cytokine stimulation. Persistent endothelial damage was indicated by a pronounced elevation of vWF and D-dimer concentrations. The persistently very low bilirubin levels despite marked hemolysis suggested a defect of hemoglobin degradation. HO-1 is the rate limiting enzyme of this pathway resulting in bilirubin synthesis. Normally, HO-1 is constitutively expressed at a low level but strongly induced by heme, and hypoxia. Functional analysis of HO-1 protein in the patient’s mononuclear blood cells showed a high constitutive expression that did not respond further to heme treatment. Sequence analysis revealed a homozygous GGT (Gly) to GTT (Val) point mutation of HO-1 codon 139. This mutation of the enzyme’s active center is known from in-vitro analyses to change enzyme activity from an oxygenase into a peroxidase. Consistent with this change in activity, quantitative analysis of reactive oxygen species (ROS) metabolites in the urine of this boy showed high amounts of bilirubin oxidative metabolites, 8-hydroxy-2′-deoxyguanosine and acrolein-lysine. In this report we thus identify a novel disease entity which is characterized by an activating mutation of HO-1 which results in a defect of hemoglobin degradation, bilirubin synthesis and in excessive oxidative stress and inflammation.

Description: Unrelated donors are commonly used for hematopoietic stem cell transplants, but graft-versus-host disease (GVHD) is a major problem. We investigated whether transplantation of CD34+ or CD133+ enriched stem cells with add-back of ten million T-cells per kg from unrelated donors would prevent acute GVHD in pediatric patients in combination with pharmacologic immunosuppression. Eighteen patients (1 CML in second chronic phase, 2 MDS, 4 ALL in CR1, 4 ALL in CR2, 1 JMML, 1 AML in CR1, 3 AML in CR2, 1 Wiskott-Aldrich syndrome and 1 NHL in CR2) were transplanted with G-CSF mobilized peripheral blood stem cells (PBSC) from HLA-matched unrelated donors (n = 18). Median of age was 8.9 years (0.5 to 18 years). Conditioning regimens were performed according to national therapy protocol guidelines. On the day of transplant patients received a median of 13.5 (4.5 to 30.0 x 106) CD34+ or CD133+ enriched stem cells and an aliquot of unmanipulated PBSC containing 10 x 106 T-cells per kg. GVHD prophylaxis consisted of cyclosporine A (CSA) and short course methotrexate (MTX) on day +1, +3 and +6. Engraftment was rapid with a median of 19.6 days in sixteen patients. Two patients failed to engraft at first. However, full donor chimerism and stable engraftment was achieved in both patients after cessation of CSA treatment and an additional stem cell boost without any reconditioning. One patient with ALL developed acute GVHD grade III (skin and gut) after cessation of CSA treatment, but responded well to treatment with CSA and steroids. None of the other 17 patients developed acute GVHD 〉 grade I. Thirteen are alive and well with a median follow-up of 578 days (101 to 1095 days). Three patients died of severe infectious complications and two due to relapse (JMML, AML). Compared to a historical control group of patients transplanted with highly purified CD34+ selected cells, the group with add-back of 10 x 106 T-cells per kg showed significantly higher T-cell counts (p=0.008, Wilcoxon Rank sum test) on day 90 after transplantation with a median number of six T-cells/μl in the control group and a median number of 294 T-cells/μl in the study group. We conclude that add-back of 10 x 106 T-cells per kg in combination with CSA and short course MTX improves T-cell recovery and appears to be a safe T-cell dosage regarding acute GVHD in the setting of allogeneic peripheral blood stem cell transplantation from unrelated donors.

Description: Graft failure is a rare but life-threatening complication after transplantation of hematopoietic stem cells. Treatment comprises immunoablative reconditioning regimens and a second stem cell donation from the same or from a different donor as soon as possible to minimize the time of pancytopenia and its sequelae. We report a cohort of 11 pediatric patients with leukemias (acute lymphatic n=4, acute or chronic myeloic/MDS n=4) and severe aplastic anemia (n=3) who experienced graft rejection after TBI, busulphan or melphalan based myeloablative transplantation from mismatched related donors (MMRD) (n=6) or after cord blood/matched unrelated donor (MUD) transplantation (n=5) between 2000 and 2006. In the latter the original donor was not available a second time. Thus, all patients were re-transplanted with CD34+ positive selected or CD3/CD19 depleted stem cells from a second, haploidentical parental donor (MACS method, Miltenyi Biotec). Median time span from diagnosis of graft rejection to second donation was 16 days. The reconditioning regimens consisted of total lymphoid irradiation or cyclophosphamide, thiotepa (5mg/kg), fludarabine (120 mg/m2) and ATG/OKT3. A median number of 25×106/kg of body weight stem cells with 60.000/kg residual T cells were infused. Mofetilmycophenolat was given as GvHD prophylaxis, if residual T cells exceeded 25 000/kg bw. Sustained engraftment was achieved in all patients (ANC〉500/μl: 9 (11–32) days). No GvHD 〉 grade II was observed. T cell recovery was delayed, however no lethal viral infection occurred. Severe organ toxicity was observed in 2 patients (BOOP, hemorrhagic cystits) and moderate mucositis in 11 patients. 8/11 patients are disease free (median follow up 1.5 (0.3–6.6) years; 1 year EFS=73%). Causes of death were: BOOP (n=1), infection (n=1); only one patient with refractory AML relapsed. Thus, transplantation of stem cells from haploidentical donors represents a realistic option to rescue patients with graft failure within a short time span and for whom a second donation of the original donor is not available. The use of a different donor may help to avoid a second rejection.

Description: There is still a significant risk of GvHD in transplantation of peripheral stem cells from matched unrelated donors, despite the use of ATG and pharmacological prophylaxis. Especially in the case of young pediatric patients and adult donors, grafts with high numbers of stem cells but also with extreme amounts of T cells can be obtained. We present an update of a clinical study with T cell reduced grafts in 22 patients, which offer both large stem cell numbers and clearly defined amounts of T cells. Positive selection of peripheral stem cells was done with CD34 or CD133 coated magnetic microbeads and the CliniMACS™ device. Afterwards, an unselected aliquot containing 10x106/kg T cells was added to the purified stem cells and infused on day 0, resulting in a median T cell depletion of 2 log. The diagnoses were: acute lymphatic leukemia (n=9; CR1=4, CR2=5), NHL (n=1) acute (n=5; CR1=1, CR2=4) and chronic myeloic leukemias (n=3), MDS (n=3) and Wiskott-Aldrich (n=1). Median age was 10 years (0.5–18). The donors were matched for HLA-A/B (medium resolution typing) and DRB1/DQB1 (high resolution). A short course of MTX (2–3x10 mg/m2) and CSA (2–3 mg/kg, adjusted to blood levels) until day 100 were given. 21/22 patients had primary engraftment with a median time to ANC 〉500 of 18 days (12–60). No G-CSF was given. One patient rejected his graft and was successfully retransplanted from another MUD. Platelet recovery was fast (median time to reach independence from substitution: 20 days). Mean numbers of CD3+, CD3+CD4+ and CD3+CD8+ on day 180 (365) were 259/μl (868/μl), 100/μl (400/μl) and 146/μl (456/μl). 19/22 patients had GvHD grade 0–I (86%), 1 and 2 patients had grade II and III, (5%, 10%) respectively. Chronic GvHD occurred in 2 patients (10%). 15/22 patients are alive with a median follow up of 3 years (1.5–5). 3 year EFS was 64% (all patients), 50% (ALL/NHL) and 73% (myeloic leukemias/MDS). Relapse probability at 2 years was 25%, probability of TRM at 2 years was 15%.Causes of death were relapse (n=4) and infections (n=3). Thus, stable and favourable survival rates with a low incidence of GvHD were achieved. The method allows to administer clearly defined T cell numbers independent from the size of the grafts. This may be of advantage in particular in small children and if the donor does not accept a bone marrow harvest: all available stem cells can be infused without the limitation of unacceptable high T cell numbers.

Description: Abstract 3344 Poster Board III-232 Background: Hepatic VOD is a life-threatening complication following SCT with a high incidence in children. Development of VOD is one of the most common causes of early death after SCT. Busulfan (BU), an alkylating agent with a very narrow therapeutic index is a commonly used conditioning agent in pediatric stem cell transplantation (SCT) with a strong correlation between AUC and both efficacy and toxicity. Oral BU (poBU) has significant age-related and interpatient pharmacokinetic differences and was linked with an increased risk for VOD. IV busulfan (ivBU) yielded promising results in some studies to be associated with low toxicity profile, especially with a reduced incidence of VOD. Methods: Patients 2 mg/dL, hepatomegaly, ascites and/or unexplained weight gain 〉 5%). VOD was assessed by physical exam; hepatomegaly and ascites were confirmed by ultrasound. A blinded IRC of 3 expert hematologists confirmed the diagnosis of VOD. Although the study was not powered to assess mortality, a composite score was assessed as a secondary endpoint that incorporated VOD-associated toxicity (respiratory failure, renal failure, encephalopathy) and mortality. The additional analysis of the influence of BU on VOD was not planned and is therefore explorative. Results: 360 pts were enrolled between January 2006 and January 2009 by 28 centers in the EU and Israel. An Intent-to-Treat (ITT) analysis was performed on all pts who signed informed consent (n=356). 251 (71%) pts from the ITT population were conditioned with BU (64% ivBU; 36% poBU). 202 (55%) were treated with BU and Melphalan (MEL) (60% ivBU; 40% poBU). In 49 (14%) BU was used without MEL (80% ivBU; 20% poBU). In children