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Essential thrombocythemia is a hematological disorder characterized by clonal hemopoiesis in the bone marrow and increased number of circulating platelets. It is usually discovered accidentally at the time of routine blood examinations or can become clinically evident with either thrombotic or hemorrhagic complications. In the present article, we describe the case of a 66-year-old woman with pneumonia due to Pneumocystis carinii, who experienced deep vein thrombosis and pulmonary embolism during hospitalization with a subsequent heparin-induced thrombocytopenia. Bone marrow examination performed after clinical improvement revealed the patient to be affected by essential thrombocythemia.

The impact of chronic lymphatic leukemia (CLL) tumor burden on the autologous immune system has already been demonstrated. This study attempted to elucidate the molecular mechanisms underlying T-cell immunologic deficiencies in CLL.Freshly isolated CD3(+) T cells from patients with a diagnosis of CLL and healthy donors were analyzed by gene expression profiling. Activated T cells from 20 patients with CLL were tested in vitro for cytotoxicity against mutated and unmutated autologous B cells and DAUDI, K562 and P815 cell lines. To investigate T-cell mediated cytotoxicity in vivo, we co-transplanted OKT3-activated T lymphocytes and autologous B-cell CLL (B-CLL) cells into NOD/SCID mice.Gene expression profiles of peripheral blood T cells from B-CLL patients showed 25 down-regulated, and 31 up-regulated, genes that were mainly involved in cell differentiation, proliferation, survival, apoptosis, cytoskeleton formation, vesicle trafficking and T-cell activation. After culture, the T-cell count remained unchanged, CD8 cells expanded more than CD4 and a cytotoxicity index30% was present in 5/20 patients. Cytotoxicity against B autologous leukemic cells did not correlate with B-cell mutational status. Only activated T cells exerting cytotoxicity against autologous leukemic B cells prevented CLL in a human-mouse chimera.This study indicates that patients with CLL are affected by a partial immunologic defect that might be somewhat susceptible to repair. This study identifies the molecular pathways underlying T-cell deficiencies in CLL and shows that cytotoxic T-cell functions against autologous B-CLL can be rebuilt at least in part in vitro and in vivo.

Primary myelofibrosis (PMF) is a chronic myeloproliferative neoplasm characterized by progressive anemia, massive splenomegaly, leukoerythroblastosis, extramedullary hematopoiesis and in about 50% of cases the presence of JAK2V617F mutation. Curative therapy in PMF is currently possible only with allogeneic haematopoietic stem cell transplantation which is, unfortunately, associated with relatively high risks of mortality and morbidity which undermine its broad applications. Non-transplant treatment modalities are used for palliative purposes. Recently, anti-angiogenic drugs such as thalidomide have been used to treat these patients on the basis of the prominent bone marrow angiogenesis. Here, we report the case of a patient suffering from JAK2V617F-positive PMF with marked bone marrow neo-angiogenesis. The patient was treated with thalidomide but after 20 days developed life-threatening toxic epidermal necrolysis (TEN). To the best of our knowledge this is the first case of TEN in a patient with PMF under thalidomide therapy.

In this study we determined whether human stromal cells could be engineered with a retroviral vector carrying the interleukin 7 (IL-7) gene and investigated the effects on T cells in vitro and in vivo in a murine model. Transduced mesenchymal cells strongly express CD90 (98.15%), CD105 (87.6%), and STRO-1 (86.7%). IL-7 production was 16.37 (+/-2 SD) pg/ml, which remained stable for 60 days. In vitro-immunoselected naive T cells maintained the CD45RA+ CD45RO- naive phenotype (4.2 times more than controls) after 7 days of culture with IL-7-engineered stromal cells. The apoptosis rate (4.7%) of the naive T cells cultured with transduced stromal cells overlapped with that of freshly isolated cells. Immunohistological analysis detected stromal cells in bone marrow, spleen, and thymus. Cotransplantation of IL-7-engineered stromal cells with CD34+ cells improved engraftment in terms of CD45+ cells and significantly increased the CD3+ cell count in peripheral blood, bone marrow, and spleen. These data demonstrate the following: (1) human stromal cells can be transduced, generating a normal layer; (2) transduced stromal cells in vitro maintain the naive T cell phenotype; and (3) IL-7-transduced stromal cells in vivo home to lymphoid organs and produce sufficient IL-7 in loco, supporting T cell development in a cotransplantation model. Because of their efficient cytokine production and homing, IL-7-engineered stromal cells might be an ideal vehicle to hasten immunological reconstitution in T cell-depleted hosts.

Haploidentical stem cell transplantation has became a clinical reality in the last 10 years as it provides the chance of transplant for about 50% of patients with hematological malignancies who do not have a matched related or unrelated donor. Proper graft preparation for this type of transplant is crucial and this paper analyses our work over the past decade in the search for the optimal graft processing procedure moving from E-rosetting and soybean agglutination, through a combination of negative or positive selection of hematopoietic stem cells to the current method of one-step positive selection. In preparing a graft for haploidentical transplant, three essential requisites must be met. It must contain (1) a megadose (>10 x 10(6) x kg recipient b.w.) of hematopoietic stem cells to overcome the HLA histocompatibility barrier; (2) very few T-lymphocytes (CD3+ cells < 3 x 10(4)/kg recipient b.w.) to prevent severe acute and chronic graft-versus-host disease (GvHD); (3) very few B-lymphocytes to prevent Epstein-Barr virus-related lymphoproliferative disorders. With current graft processing technologies based on positive selection of hematopoietic stem cells, these requirements can be met. A 70-80% hematopoietic stem cell recovery ensures the target megadose is achieved in over 70% of cases with a T-cell depletion of more than 4 logs and a B-cell depletion of over 3 logs. Progress in graft processing has ensured primary, sustained engraftment rates of over 90% and has significantly reduced the incidence of severe acute GvHD and EBV-related lymphoproliferative disorders. Modern time-saving automated graft processing devices ensure reproducibility, reliability, and biological safety, which make widespread application of the haploidentical transplant currently feasible.

To develop a trial with lymphocyte suicide gene therapy in patients with hematological malignancies, we transduced human T lymphocytes with a retroviral vector (LSN-tk) encoding the herpes simplex virus thymidine kinase (tk) and the neomycin resistance (NeoR) genes. Precise quantification of gene transfer is crucial for any gene therapy protocol, but methods using semiquantitative PCR are inaccurate and subject to variations. Real-time quantitative PCR could be a valid alternative. A TaqMan probe was designed to hybridize with the NeoR gene. The PCR product is 64 nucleotides long and readily quantified by TaqMan probe binding. The analysis was performed soon after transduction and repeated after the selection procedure. This method was more accurate, reproducible, and sensitive than the semiquantitative PCR assay. Accuracy was the same whether the analysis was performed at the highest rate or at the lowest rate of transduction. Additionally we used real-time PCR to monitor the kinetics of enrichment of the transduced cells over the selection time and showed how 7 days of selection are needed. This study precisely quantified the percentages of cells transduced by the retroviral vector and could have major implications in gene therapy studies.

Relapse is still the major cause of failure of allogeneic stem cell transplantation in high-risk acute leukemia patients. Indeed, whoever the donor and whatever the transplantation strategy, post-transplant relapse rates are ~30%, which is hardly satisfactory. The present phase 2 study analyzed the impact of adoptive immunotherapy with naturally occurring FoxP3+ T-regulatory cells (2 × 10(6) per kg) and conventional T lymphocytes (1 × 10(6) per kg) on prevention of GvHD and leukemia relapse in 43 high-risk adults undergoing full-haplotype mismatched transplantation without any post-transplant immunosuppression. Ninety-five percent of patients achieved full-donor type engraftment. Only 6/41 patients (15%) developed ⩾ grade II acute GvHD. Specific CD4(+) and CD8(+) for opportunistic pathogens emerged significantly earlier than after standard T-cell-depleted haplo-transplantation. The probability of disease-free survival was 0.56. At a median follow-up of 46 months (range 18-65 months), only 2/41 evaluable patients have relapsed. The cumulative incidence of relapse was significantly lower than in historical controls (0.05 vs 0.21; P = 0.03). These results demonstrate that the immunosuppressive potential of Tregs can be used to suppress GvHD without loss of the benefits of GvL activity. Humanized murine models provided insights into the mechanisms underlying separation of GvL from GvHD.

The EGFP-tk retroviral vector, encoding enhanced green fluorescent protein (EGFP) and the herpes simplex virus thymidine kinase (HSV-tk) packaged in a Phoenix amphotropic cell line, was used to transduce healthy donor T lymphocytes. Infection yielded a mean of 41.8 +/- 9.3% SD (range 31.1-48.4%) EGFP-positive cells and a mean of 92 +/- 2% SD (range 90-94%) after cell sorting. EGFP expression remained stable for 30 d after infection. The entire gene transfer procedure had no significant effect on lymphocyte subsets and slightly reduced clonogenicity. Ganciclovir (gcv) treatment (1 microg/ml x 10 d) killed all EGFP-positive cells in the transduced and transduced/sorted populations, but had no effect on untransduced controls. Our results show that primary T lymphocytes can be transduced using an EGFP-tk vector that yields a homogeneous infected population without affecting lymphocyte subsets, function and clonogenicity.

In this study, we assessed the efficiency of T lymphocyte transduction with a retroviral vector carrying the herpes simplex virus thymidine kinase (HSV-tk) and neomycin phosphotransferase (neo) genes by four different protocols: standard supernatant infection, supernatant infection plus centrifugation steps, supernatant infection on fibronectin fragment-coated wells, and cocultivation. After retrovirus-mediated gene transfer of tk-neo in PHA/IL-2-stimulated primary T lymphocytes and G418 selection, T cells retained their proliferative activity, alloresponsiveness, ability to produce and to respond to IL-2, and ganciclovir (gcv)-specific sensitivity. When the four different transduction techniques were compared, no significant differences were seen in terms of cellular viability, proliferation capacity, and immunophenotyping. tk gene expression was the same in all transduced selected populations, as indicated by gcv sensitivity. Transduction efficiency was evaluated by semiquantitative PCR. Using the standard supernatant infection method, the rate of infection was extremely low (

Oxidative metabolism and redox signaling prove to play a decisional role in controlling adult hematopoietic stem/progenitor cells (HSPCs) biology. However, HSPCs reside in a hypoxic bone marrow microenvironment raising the question of how oxygen metabolism might be ensued. In this study, we provide for the first time novel functional and molecular evidences that human HSPCs express myoglobin (Mb) at level comparable with that of a muscle-derived cell line. Optical spectroscopy and oxymetry enabled to estimate an O2-sensitive heme-containing protein content of approximately 180 ng globin per 106 HSPC and a P50 of approximately 3 µM O2. Noticeably, expression of Mb mainly occurs through a HIF-1-induced alternative transcript (Mb-V/Mb-N = 35 ± 15, p < .01). A search for other Mb-related globins unveiled significant expression of neuroglobin (Ngb) but not of cytoglobin. Confocal microscopy immune detection of Mb in HSPCs strikingly revealed nuclear localization in cell subsets expressing high level of CD34 (nuclear/cytoplasmic Mb ratios 1.40 ± 0.02 vs. 0.85 ± 0.05, p < .01) whereas Ngb was homogeneously distributed in all the HSPC population. Dual-color fluorescence flow cytometry indicated that while the Mb content was homogeneously distributed in all the HSPC subsets that of Ngb was twofold higher in more immature HSPC. Moreover, we show that HSPCs exhibit a hypoxic nitrite reductase activity releasing NO consistent with described noncanonical functions of globins. Our finding extends the notion that Mb and Ngb can be expressed in nonmuscle and non-neural contexts, respectively, and is suggestive of a differential role of Mb in HSPC in controlling oxidative metabolism at different stages of commitment. Stem Cells 2014;32:1267–1277

Today human leukocyte antigen-haploidentical transplantation is a feasible option for patients with high-risk acute leukemia who do not have matched donors. Whether it is T-cell replete or T-cell depleted, it is still, however, associated with issues of transplant-related mortality and posttransplant leukemia relapse. After reports that adoptive immunotherapy with T-regulatory cells controls the alloreactivity of conventional T lymphocytes in animal models, tomorrow’s world of haploidentical transplantation will focus on new “designed” grafts. They will contain an appropriate ratio of conventional T lymphocytes and T-regulatory cells, natural killer cells, γ δ T cells, and other accessory cells. Preliminary results of ongoing clinical trials show the approach is feasible. It is associated with better immune reconstitution and a quite powerful graft-versus-leukemia effect with a low incidence of graft-versus-host disease and no need for posttransplant pharmacological prophylaxis. Future strategies will focus on enhancing the clinical benefit of T-regulatory cells by increasing their number and strengthening their function.

γ-Secretase inhibitors (GSIs) have been proposed for combined therapies of malignancies with a dysregulated Notch signaling. GSI I (Z-Leu-Leu-Nle-CHO) induces apoptosis of some tumor cells by inhibiting proteasome and Notch activity. Alterations in these two cell survival regulators contribute to apoptosis resistance of chronic lymphocytic leukemia (CLL) cells. Here, we investigated the mechanisms whereby GSI I increases apoptosis of primary CLL cells. Time-course studies indicate that initial apoptotic events are inhibition of proteasome activity, concomitant with an increased endoplasmic reticulum (ER) stress apoptotic signaling, and a consistent Noxa protein up-regulation. These events precede, and some of them contribute to, mitochondrial alterations, which occur notwithstanding Mcl-1 accumulation induced by GSI I. In CLL cells, GSI I inhibits Notch1 and Notch2 activation only in the late apoptotic phases, suggesting that this event does not initiate CLL cell apoptosis. However, Notch inhibition may contribute to amplify GSI I-induced CLL cell apoptosis, given that Notch activation sustains the survival of these cells, as demonstrated by the evidence that both Notch1 and Notch2 down-regulation by small-interfering RNA accelerates spontaneous CLL cell apoptosis. Overall, our results show that GSI I triggers CLL cell apoptosis by inhibiting proteasome activity and enhancing ER stress, and amplifies it by blocking Notch activation. These findings suggest the potential relevance of simultaneously targeting these three important apoptosis regulators as a novel therapeutic strategy for CLL.

The NOTCH1 gene has been shown to have an essential biological role in hematopoiesis and cancer [1]. In 2009, we were the first group to identify NOTCH1 mutations in chronic lymphocytic leukemia (C...

Background: the Registro Italiano Trombocitemie (RIT) was activated mainly to evaluate the diagnosis and therapy appropriateness in the thrombocythemic patients with Ph-negative myeloproliferative neoplasm (MPN) observed in the adhering centers. Objective: to evaluate how the diagnostic and therapeutic approach changed in the RIT patients diagnosed with thrombocythemic MPN in the last two decades. Methods: the RIT centers registered by a web-based system during the years 2005-2014 their thrombocythemic MPN patients, and semesterly updated their follow-up data. For patients diagnosed before 2005, the data on diagnosis and prior follow-up were retrospectively collected. The diagnostic process and the initial treatment (started into the first year after diagnosis) were comparatively analyzed in the patients diagnosed before and after 2005. Results: the RIT centers registered 2629 patients. 2388 of them, object of this analysis, were diagnosed between1995 and 2014: 1098 (46%) in the decade 1995-2004 (Group I), and 1290 (54%) in the decade 2005-2014 (Group II). The diagnostic process in the patients of Group II and Group I included bone marrow biopsy (BMB, performed into 1 year and before any cytoreduction): 85% vs 80%, p The patients of Group II, as compared with those of Group I, showed a similar gender distribution (M/F ratio 0.61 vs 0.65, p 0.452), and had at diagnosis: a higher age (median 60 vs 57 years, p 60 years in 50% vs 45% of cases, p Moreover, they had: a lower platelet (PLT) count (median 737 vs 775 x 109/L, p 10 x 109/L in 28% vs 26% cases); a similar median levels of hematocrit (HCT %, in females 41.4 vs 41.0; in males 44.7 vs 44.6) and hemoglobin (Hb g/dL, in females 13.8 vs 13.6; in males 15.0 vs 14.9). The BMB, revised according to the WHO 2008 criteria, showed a not different distribution (p 0.21) of ET (64% vs 61%), ep-PMF (16% vs 17%), PMF (3% vs 2%), PV (4% vs 4%), and U-MPN (13% vs 16%. The JAK2 V617F mutation in patients of Group II (at diagnosis) and of Group I (after diagnosis) was found in 62% and in 58% of tested cases (p 0.054), respectively. The patients at high standard thrombotic risk were 58% vs 52%, p 0.004. In the patients of Group II and Group I the distribution of the treatment started into the first year was significantly different (p The treatment CYT ± AntiPLT was started in the patients at high standard thrombotic risk with a rate of 81% vs 80%, respectively, and in the patients at low standard thrombotic risk in 37% vs 43% of cases, respectively. The initial treatment CYT±AntiPLT was related, in multivariate analysis, both in patients of Group II and Group I, with older age (>60 and 40-60 vs 1000 and 700-1000 vs Conclusion: in the studied thrombocythemic MPN patients the real-life diagnostic approach was improved after 2005 not only due to the routine use of JAK2 tests, but also due to the higher rate of BMB done (85% vs 80%). The appropriateness of the cytoreductive treatment (CYT±AntiPLT started into one year from diagnosis) remained high in patients at high standard thrombotic risk (over 80% of cases were treated). Concomitantly, the inappropriate use of the cytoreductive drugs in patients at low standard thrombotic risk appreciably decreased (from 43% to 37% of cases). Moreover, it has to be remarked that the therapeutic approach was significantly influenced not only by older age and prior thrombosis, but also by thrombocytosis (PLT count >700 x 109/L), disease-related symptoms, and inconstantly by leukocytosis and CVRFs. Table Table. Disclosures Gugliotta: SHIRE Co.: Honoraria. Gugliotta:Bristol Myers Squibb: Consultancy, Honoraria; Novartis: Consultancy, Honoraria.

We selected T regulatory cells (Tregs) from standard leukapheresis using double-negative selection (anti-CD8 and anti-CD19) followed by positive selection (anti-CD25) and 72 procedures were performed. A median of 263×10(6)cells (range 143-470×10(6)) were recovered with a mean of CD4(+)/CD25(+) cells of 94.5±2.4% (36.5±18.6% CD4(+)/CD25(+hi)). FoxP3(+) cells were equal to 79.8%±22.2. CD127(+) cells were 12.5%±8.2. The inhibition assay showed an inhibition rate of 67±22. Cells isolated by means of this approach can be used in allogeneic hematopoietic stem cell transplantation to reduce the incidence and severity of GvHD without bystander inhibition of general immunity.

Background: Autologous stem cell transplantation (ASCT) generally provides good results in Hodgkin’s lymphoma (HL). We studied a high-dose chemotherapy regimen based on thiotepa, etoposide and carboplatin (TECA).Methods: Fifty-eight patients with advanced HL were treated with thiotepa, etoposide and carboplatin for transplant induction.Results: The overall response rate was 79·3% (39 CR: 67·2%; and 7 PR: 12·1%); 12 patients (20·1%) were non-responders. The 5-year overall survival rate was 77·6%; five initially responder patients relapsed within the first 5 years of follow-up and underwent salvage therapy.Conclusion: The TECA conditioning regimen for ASCT in HL results in a good anti-HL effect, positive response to treatment and high 5-year overall survival rate. It was also well tolerated and did not induce excessive toxicity, suggesting that TECA may be a very useful conditioning regimen for HL.

High-dose chemotherapy conditioning regimens followed by autologous stem cell transplantation generally provide good results in non-Hodgkin lymphoma. We have evaluated the effects of a high-dose regimen comprising thiotepa, etoposide and carboplatin. After debulking and mobilization with high-dose cyclophosphamide or other schedules, forty-five patients at various disease stages were conditioned with thiotepa, etoposide and carboplatin prior to autologous stem cell transplantation. The overall response rate was 77.8% (30 CR, 66.7%; 5 PR, 11.1%). Ten patients (22.2%) did not respond. Two patients (4.4%) died from transplant-related complications. The mean 5-year overall survival was 71.1%: 12 patients relapsed within the first 5 years of follow-up. The overall response rate and 5-year overall survival were better for patients with an International Prognostic Index (IPI) 1 at diagnosis than for those with IPI 2 and IPI 3 (P

Haploidentical transplantation, with extensive T cell depletion to prevent GvHD, is associated with a high incidence of infection-related deaths. The key challenge is to improve immune recovery with allogeneic donor T cells without triggering GvHD. As T regulatory cells (Tregs) controlled GvHD in preclinical studies, the present phase I/II clinical trial evaluated the impact of early infusion of donor CD4/CD25+ Tregs, followed by an inoculum of donor mature T cells (Tcons) and positively immunoselected CD34+ cells. Twenty-eight patients (median age 41, range 21-60) were enrolled from September 2008 onwards; 22 had AML (10 in CR1 at high risk, 10 in ≥CR2 and 2 in relapse), 5 had ALL (4 in CR1; 1 in relapse) and 1 had high grade NHL in relapse. Conditioning was: 8 Gy single fraction TBI, thiotepa (4 mg/kg × 2), fludarabine (40 mg/m2 × 5), cyclophosphamide (35 mg/kg × 2). All patients received immunoselected Tregs (CliniMACS, Miltenyi Biotec) (23/28 2 × 106/kg bw; 5/28 4 × 106/kg bw) and 4 days later positively immunoselected CD34+ cells (median 8.2 × 106/kg bw, range 5.0-19.1) together with Tcons (4/28 0.5 × 106/kg bw; 17/28 1 × 106/kg bw; 5/28 2 × 106/kg bw; 2/28 did not receive Tcons). CD4/CD25+ Tregs (purity 92.7 ± 2.1) consisted of 33.6% ± 13.1 CD25high; 58.1% ± 6.6 CD25int; 5.8% ± 2.5 CD25low; 65.7% ± 11.8 FoxP3; 17.4% ± 7.2 CD127 (mean ± SD). No GvHD prophylaxis was administered. 26/28 patients engrafted. No GvHD developed in 24/26 patients, 2 developed ≥ grade II GvHD. Ten patients died (3 VOD, 2 fungal pneumonia, 1 bacterial sepsis, 1 CNS aspergillosis, 1 systemic toxoplasmosis, 1 adenoviral infection, 1 MOF). CD4 and CD8 counts reached, respectively, 50/μL medianly on days 34 (range 19-63 days) and 24 (range 15-87); 100/μL medianly on days 47 (range 28-100 days) and 34 (range 19-95); 200/μL on days 70 (range 41-146 days) and 61 (range 21-95). A wide T-cell repertoire developed rapidly with high frequencies of specific CD4+ and CD8+ for opportunistic pathogens. Episodes of CMV reactivation were significantly fewer than after our "standard haplo" transplants. In KIR ligand-mismatched transplants, speed of NK cell reconstitution/maturation and size of donor vs recipient alloreactive NK cell repertoires were preserved. In conclusion, in the setting of haploidentical transplantation infusion of Tregs makes administration of a high dose of T cells feasible for the first time. This strategy provides a long-term protection from GvHD and robust immune reconstitution.

The safest duration of anticoagulation after idiopathic deep vein thrombosis (DVT) is unknown. We conducted a prospective study to assess the optimal duration of vitamin K antagonist (VKA) therapy considering the risk of recurrence of thrombosis according to residual vein thrombosis (RVT). Patients with a first unprovoked DVT were evaluated for the presence of RVT after 3 months of VKA administration; those without RVT suspended VKA, while those with RVT continued oral anticoagulation for up to 2 years. Recurrent thrombosis and/or bleeding events were recorded during treatment (RVT group) and 1 year after VKA withdrawal (both groups). Among 409 patients evaluated for unprovoked DVT, 33.2% (136 of 409 patients) did not have RVT and VKA was stopped. The remaining 273 (66.8%) patients with RVT received anticoagulants for an additional 21 months; during this period of treatment, recurrent venous thromboembolism and major bleeding occurred in 4.7% and 1.1% of patients, respectively. After VKA suspension, the rates of recurrent thrombotic events were 1.4% and 10.4% in the no-RVT and RVT groups, respectively (relative risk = 7.4; 95% confidence interval = 4.9-9.9). These results indicate that in patients without RVT, a short period of treatment with a VKA is sufficient; in those with persistent RVT, treatment extended to 2 years substantially reduces, but does not eliminate, the risk of recurrent thrombosis.

Hastening posttransplantation immune reconstitution is a key challenge in human leukocyte antigen (HLA)–haploidentical hematopoietic stem-cell transplantation (HSCT). In experimental models of mismatched HSCT, T-regulatory cells (Tregs) when coinfused with conventional T cells (Tcons) favored posttransplantation immune reconstitution and prevented lethal graft-versus-host disease (GVHD). In the present study, we evaluated the impact of early infusion of Tregs, followed by Tcons, on GVHD prevention and immunologic reconstitution in 28 patients with high-risk hematologic malignancies who underwent HLA-haploidentical HSCT. We show for the first time in humans that adoptive transfer of Tregs prevented GVHD in the absence of any posttransplantation immunosuppression, promoted lymphoid reconstitution, improved immunity to opportunistic pathogens, and did not weaken the graft-versus-leukemia effect. This study provides evidence that Tregs are a conserved mechanism in humans.

Introduction Haploidentical transplantation, with extensive T cell depletion to prevent GvHD, is associated with a high incidence of infection-related deaths. The key challenge is to improve immune recovery with allogeneic donor T cells without triggering GvHD. As T regulatory cells (Tregs) controlled GvHD in pre-clinical studies, the present study evaluated the impact of an infusion of donor CD4/CD25 + Tregs, followed by an inoculum of donor mature T cells (Tcons) and positively immunoselected CD34 + cells in the setting of haploidentical stem cell transplantation. Patients and methods Twenty-eight patients were enrolled in this study (22 AML; 5 ALL; 1 NHL). All received immunoselected Tregs (CliniMACS, Miltenyi Biotec) followed by positively immunoselected CD34 + cells together with Tcons 4 days later. No GvHD prophylaxis was administered. Results 26/28 patients engrafted. No acute GvHD developed in 24/26 patients; 2 developed ≥ grade II acute GvHD. No patient has developed chronic GvHD. CD4 and CD8 counts rapidly increased after transplant. Episodes of CMV reactivation were significantly fewer than in controls. Conclusions In the setting of haploidentical transplantation infusion of Tregs makes administration of a high dose of T cells feasible. This strategy provides a long-term protection from GvHD and robust immune reconstitution.

A better understanding of apoptotic signaling in B-chronic lymphocytic leukemia (B-CLL) cells may help to define new therapeutic strategies. This study investigated endoplasmic reticulum (ER) stress signaling in spontaneous apoptosis of B-CLL cells and whether manipulating ER stress increases their apoptosis. Results show that a novel ER stress-triggered caspase cascade, initiated by caspase-4 and involving caspase-8 and -3, plays an important role in spontaneous B-CLL cell apoptosis. ER stress-induced apoptosis in B-CLL cells also involves CHOP/GADD153 up-regulation, increased JNK1/2 phosphorylation, and caspase-8–mediated cleavage of Bap31 to Bap20, known to propagate apoptotic signals from ER to mitochondria. In ex vivo B-CLL cells, some apoptotic events associated with mitochondrial pathway also occur, including mitochondrial cytochrome c release and caspase-9 processing. However, pharmacologic inhibition studies show that caspase-9 plays a minor role in B-CLL cell apoptosis. ER stress also triggers survival signals in B-CLL cells by increasing BiP/GRP78 expression. Manipulating ER signaling by siRNA down-regulation of BiP/GRP78 or treating B-CLL cells with 2 well-known ER stress-inducers, tunicamycin and thapsigargin, increases their apoptosis. Overall, our findings show that ER triggers an essential pathway for B-CLL cell apoptosis and suggest that genetic and pharmacologic manipulation of ER signaling could represent an important therapeutic strategy.

Abstract 480 Acute myeloid leukemia with mutated NPM1 gene and cytoplasmic nucleophosmin (NPMc+ AML) [Falini B et al, NEJM 2005;352:254-266] is a new entity of WHO classification that shows distinctive biological and clinical features [Falini B et al, Blood 2007;109:874-885] which include negativity for CD34 antigen expression at both immunohistochemistry and gene expression profiling. Flow cytometric analysis shows that, in most NPM1-mutated AML, percentages of CD34+ cells are in the low range (< 5-10%). Detection of NPM1 mutations by molecular techniques and/or immunohistochemistry and Western Blot analysis with specific antibodies provides an important tool for tracking the genetic lesion in leukemic cells at different hierarchical stage. We previously reported involvement by NPM1 gene mutation of the CD34+ cell fraction isolated from patients with NPM1-mutated AML, and, in one case, the involvement, in particular, of the early progenitor CD34+/CD38- [Martelli MP et al, Blood (ASH Annual Meeting Abstracts) 2008;112:307]. Here we expand and confirm our previous observation in 5 cases of CD34-negative NPM1-mutated AML. CD34+/CD38- cells were isolated by either FACS (3 cases, purity >98%) or MACS-sorting (2 cases, purity >92%) and analyzed by molecular analysis and Western Blot with a specific anti-NPM1 mutant antibody, respectively. The presence of either NPM1 gene mutation or mutant protein was demonstrated in all samples analyzed proving the CD34+/CD38- cells belong to the leukemic clone. This cell subpopulation displayed also immunophenotypic features classically associated to leukemic stem cells (LSCs) (CD123+/CD33+/CD90-) in all (16/16) samples analyzed, suggesting they might actually represent the LSCs in NPM1-mutated AML. Indeed, CD34+ cell fraction isolated from NPM1-mutated AML was able to generate leukemia in immunocompromised mice resembling the original patient's disease. However, there is experimental evidence that, at least in some CD34-negative AML, also the CD34- population may contain LSCs. Whether the CD34- cell compartment in NPM1-mutated AML is also able to engraft and outgrow into leukemia in mice remains to be clarified. For this purpose, we assessed the engraftment ability of CD34- cells from 5 NPM1-mutated AML patients. No engraftment was observed in one case. Interestingly, in three patients with myelomonocytic (M4, 2 cases) and myelocytic (M2, 1 case) AML, the CD34- fraction resulted into marrow engraftment by human CD45+/CD33+ myeloid cells that, at morphological and immunohistological grounds, consisted of a mixed population of macrophage cells expressing the CD68 (PG-M1) antigen and mature looking myeloperoxidase (MPO)-positive cells. This pattern possibly reflects short-term engraftment by leukemic cells devoid of self-renewal potential that differentiated into mature elements. However, the neoplastic nature of engrafted cells could be established with certainty only in one case by western blotting detection of NPM1 mutant protein. Immunohistochemistry could not help in these cases to establish the leukemic nature of human cells since terminally differentiated leukemic cells in NPM1-mutated AML show nucleus-restricted NPM1 positivity. In contrast, the pure CD34+ fraction (availabel for comparison in one of these three cases) engrafted as AML with clear blastic morphology and cytoplasmic dislocation of nucleophosmin. In a fourth patient, the highly purified CD34- fraction from relapsed NPM1-mutated AML engrafted in mice with a typical AML picture. These preliminary findings suggest that in general the CD34- fraction from NPM1-mutated AML may have more limited engraftment potential than the CD34+ fraction. Further studies are ongoing to address this issue. Disclosures: Falini: Xenomics: Patents & Royalties.

Objective Discovery of genetic variations in the genes encoding for Toll-like receptors (TLRs) has highlighted a potential link between genomic variation of the host and susceptibility to infections. Materials and Methods We investigated the association between polymorphisms in the TLR2, TLR4, and TLR9 genes in recipients of allogeneic hematopoietic stem cell transplant and susceptibility to infections caused by cytomegalovirus and filamentous fungi. Results A significant association was observed between the presence of the T-1237C polymorphism (TLR9) and susceptibility to viral pneumonia (p = 0.04; odds ratio [OR]: 1.73). For fungi, a significant association was observed between the presence of the cosegregating Asp299Gly/Thr399Ile polymorphisms (TLR4) and fungal colonization (p = 0.003; OR: 10.6). However, susceptibility to fungal infections, predominantly fungal pneumonia, was instead significantly decreased in the presence of the same polymorphisms (p = 0.03; OR: 0.23). Conclusion Thus, fungal colonization may not predict susceptibility to infection in the presence of these single nucleotide polymorphisms. The finding that defective viral but not fungal sensing may predict susceptibility to infection highlights the divergent function of TLRs in the pathogenesis of opportunistic infections., This study was supported by the Specific Targeted Research Project “MANASP” (Luxembourg) (LSHE-CT-2006), contract number 037899 (FP6), the Italian project PRIN prot. 2007BAHJKR_004 (Rome, Italy) and by Fundação para a Ciência e Tecnologia (Lisbon, Portugal) (POCI/SAU-ESP/61080/2004). Agostinho Carvalho was financially supported by a fellowship from Fundação para a Ciência e Tecnologia (Lisbon, Portugal) (contract SFRH/BPD/46292/2008).

Notch signaling is involved in tumorigenesis, but its role in B–chronic lymphocytic leukemia (B-CLL) pathogenesis is not completely defined. This study examined the expression and activation of Notch receptors in B-CLL cells and the role of Notch signaling in sustaining the survival of these cells. Our results show that B-CLL cells but not normal B cells constitutively express Notch1 and Notch2 proteins as well as their ligands Jagged1 and Jagged2. Notch signaling is constitutively activated in B-CLL cells, and its activation is further increased in B-CLL cells, which resist spontaneous apoptosis after 24-hour ex vivo culture. Notch stimulation by a soluble Jagged1 ligand increases B-CLL cell survival and is accompanied by increased nuclear factor–kappa B (NF-κB) activity and cellular inhibitor of apoptosis protein 2 (c-IAP2) and X-linked inhibitor of apoptosis protein (XIAP) expression. In contrast, Notch-signaling inhibition by the γ-secretase inhibitor I (GSI; z-Leu-Leu-Nle-CHO) and the specific Notch2 down-regulation by small-interfering RNA accelerate spontaneous B-CLL cell apoptosis. Apoptotic activity of GSI is accompanied by reduction of NF-κB activity and c-IAP2 and XIAP expression. Overall, our findings show that Notch signaling plays a critical role in B-CLL cell survival and apoptosis resistance and suggest that it could be a novel potential therapeutic target.

The discovery of the Janus kinase 2 Val617Phe mutation has brought new insights into the development of myeloproliferative disorders; however, the pathogenesis of essential thrombocythemia and its related thrombotic complications has not been completely understood. Although the Janus kinase 2 Val617Phe mutation confirms the initially suspected clonal character of the disease, factors influencing clonal transformation and expansion in the bone marrow have not been fully detected. Furthermore, patients affected by essential thrombocythemia who are carriers of the Janus kinase 2 Val617Phe mutation show a higher incidence of venous thromboembolism both before, and at the time of diagnosis, compared with noncarriers, and recent evidence of splanchnic and cerebral vein thrombosis in carriers of the Janus kinase 2 Val617Phe mutation has been reported. The intake of oral contraceptives is a strong and independent risk factor for venous thromboembolism. In addition, in-vitro tests showed both an altered primary haemostatic plug formation and enhanced platelet aggregation in patients taking such drugs. Little is known, though, about the influence of steroid hormones on both megakaryopoiesis and platelet function in patients with the Janus kinase 2 Val617Phe mutation. Herewith, we report the case of a 30-year-old woman who took a third generation oral contraceptive for 5 months and developed an essential thrombocythemia with splenog-portal axis and superior mesenteric vein thrombosis. She was found to carry the kinase gene Janus kinase 2 mutation. © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Retroviral vectors are used in human gene therapy trials to stably introduce therapeutic genes in the genome of patients' cells. Their applicability, however, is frustrated by the limited viability of transformed cells and/or by risks linked to selection of oncogene-mutated clones. The reasons for these drawbacks are not yet completely understood. In this study, we show that LXSN-NeoR gene/interleukin-7-engineered mesenchymal stromal cells exhibited a marked enhancement of reactive oxygen species production compared with untransfected cells. This effect resulted to be independent on the product of the gene carried by the retroviral vehicle as it was reproducible in cells transfected with the empty vector alone. Stable transfection of mesenchymal stromal cells with the different retroviral vectors pBabe-puro and PINCO-puro and the lentiviral vector pSico PGK-puro caused similar redox imbalance, unveiling a phenomenon of more general impact. The enhanced production of reactive oxygen species over the basal level was attributable to mitochondrial dysfunction and brought back to altered activity of the NADH-CoQ oxidoreductase (complex I) of the respiratory chain. The oxidative stress in transfected mesenchymal stem cells was completely reversed by treatment with a cAMP analog, thus pointing to alteration in the protein kinase A-dependent signaling pathway of the host cell. Transfection of mesenchymal stromal cells with a PINCO-parental vector harboring the green fluorescent protein gene as selection marker in place of the puromycin-resistance gene resulted in no alteration of the redox phenotype. These novel findings provide insights and caveats to the applicability of cell- or gene-based therapies and indicate possible intervention to improve them. Disclosure of potential conflicts of interest is found at the end of this article.

Objective Despite much investigation into T regulatory cells (Tregs), little is known about the mechanism controlling their recruitment and function. Because multipotent mesenchymal stromal cells (MSCs) exert an immune regulatory function and suppress T-cell proliferation, this in vitro study investigated their role in Treg recruitment and function. Materials and Methods Human MSCs and different T cell populations (CD3 + , CD3 + /CD45RA + , CD3 + /CD45RO + , CD4 + /CD25 + , CD4 + /CD25 + /CD45RO + , CD4 + /CD25 + /CD45RA + ) from healthy donors were cocultured for up to 15 days. Harvested lymphocytes were analyzed by flow cytometry and FoxP3 and CD127 expressions were measured by real-time polymerase chain reaction. Their regulatory activity was assessed. Results We demonstrate MSC recruit Tregs from a fraction of CD3 + and from immunoselected CD3 + /CD45RA + and CD3 + /CD45RO + fractions. After culture with MSCs both immunoselected fractions registered increases in the CD4 + /CD25 bright /FoxP3 subset and CD127 expression was downregulated. When purified Treg populations (CD4/CD25 + , CD4/CD25 + /CD45RA + , and CD4/CD25 + /CD45RO + ) are used in MSC cocultures, they maintain FoxP3 expression and CD127 expression is downregulated. Treg suppressive capacity was maintained in Treg populations that were layered on MSC for up to 15 days while control Tregs lost all suppressive activity after 5 days culture. Conclusions In conclusion, our study demonstrates that MSCs recruit, regulate, and maintain T-regulatory phenotype and function over time.

As Chronic Lymphocytic Leukemia (CLL) is associated with several defects in the T cell compartment, the impact of tumour burden on the autologous immune system was studied. Gene expression profiles (using Applied Biosystem Human Genome Microarray) identified 237 genes with significantly increased expression and 221 genes with significantly decreased expression (p 30% in 5/20 patients. The other 15 were partially cytotoxic against P815, K562 and Daudi. Cell line analysis in all 20 confirmed prevalently T cell-mediated cytotoxicity and poor NK/LAK activity. Cytotoxicity did not correlate with B cell mutational status. We tested the cytotoxic activity of autologous activated T cells in NOD/SCID mice co-transplanted with leukaemic B cells. Only activated T cells exerting cytotoxicity vs autologous B-cell CLL prevent CLL in human-mouse chimera, as confirmed by PCR and FACS analysis which visualised only CD3+ cells. In conclusion, in patients with CLL, activating autologous T cells with OKT3 /IL-2 bypasses, at least in part, the T cell immunological deficiencies. These in vitro and in vivo findings might serve to throw light on new mechanisms that could be exploited in immunotherapy designed to exert disease control.

Patients who underwent autologous stem cell transplantation (ASCT) are prone to decreased bone mineral density (BMD). We measured BMD in 180 patients who underwent ASCT for hematologic malignancies. Patients were evaluated with a median of 6.2 years after ASCT. Twenty patients who received only chemotherapy were evaluated as controls. The loss of bone mass was greater during the first year after ASCT, since majority of patients recover BMD and normalize bone turnover markers during the following years. After ASCT, over half of the patients show osteopenia or osteoporosis independent of the sex. According to the results of other groups, our results emphasize the potential usefulness of antiresorptive agents to prevent or treat post-ASCT osteopenia or osteoporosis, and the importance of the measurement of BMD as an integral component to the follow-up of ASCT.

Despite much investigation into T regulatory cells (Tregs), little is known about the mechanism controlling their recruitment and function. Since mesenchymal cells (MSCs) exert an immune regulatory function and suppress T cell proliferation, this in vitro study investigated their role in Treg recruitment and function. hMSCs and different T cell populations (CD3+, CD3+/CD45RA+, CD3+/CD45RO+, CD4+/CD25+, CD4+/CD25+/CD45RO+, CD4+/CD25+/CD45RA+) from healthy donors were co-cultured for up to 15 days. Harvested lymphocytes were analysed by flow-cytometry; FoxP3 and CD127 expression were measured by real time PCR; regulatory activity was assessed. Within CD3+ fraction, percentages of CD4+/CD25bright and CD4+/CD25bright/Foxp3+ cells were higher in the presence of hMSCs (42% vs 34% for the CD4+/CD25bright and 20.5 vs 3.5 for the CD4+/CD25bright/Foxp3+). Within CD3+/CD45RA+ and CD3+/CD45RO+ fractions, the T reg starting fraction of the naïve population rose from 0.05% ± 0.01 CD4/CD25 positive cells to 0.2% ± 0.14 and the T reg starting fraction of the memory population rose from 0.3% ± 0.05 CD4/CD25 positive cells to 1.5% ± 0.9. Within CD4+/CD25+, CD4+/CD25+/CD45RA+, CD4+/CD25+/CD45RO+, FoxP3 expression did not change in CD4+/CD25+ cells. It increased 5.38±2.3 fold in CD4+/CD25+/CD45RA+ and 7.98±1.9 fold in CD4+/CD25+/CD45RO+ cells. CD127 expression decreased by -582±29.2 fold in CD4+/CD25+ cells, by -216±17.5 fold in CD4+/CD25+/CD45RA+ and by -71.95±12.6 fold in CD4+/CD25+/CD45RO+ cells. Cytofluorimetric analysis showed CD4+/CD25+/FoxP3+ was up-regulated to 14%±4 and CD127 down-regulated to 4.4%±1.5 vs respectively 0.2%±0.28 and 21.9%±3.5 in controls without MSCs (CD4+/CD25+ alone). FoxP3 up-regulation was more marked in CD4+/CD25bright cells (51%±10 vs 0.1%±0.7 in controls). Sorted Tregs exert potent immunosuppressive activity on CD4+/CD25- cell populations. Inhibitory activity was lost within 15 days when sorted T regs were cultured without hMSC. On day +15 proliferation using CD4+/CD25+ cells as suppressor cells was 1.7±0.8 vs 45.2±12 in controls; proliferation using CD4/CD25+/CD45RA+ as suppressor cells was 5.4±3.1, vs 21.3±11.2 in controls, and proliferation with CD4+/CD25+/RO+ as suppressor cells was 2.3±2 vs 33.5±8.7 in controls. We demonstrate MSC recruit Tregs from a fraction of CD3+ and from immunoselected CD3+/CD45RA+ and CD3+/CD45RO+ fractions. After culture with MSCs both immunoselected fractions registered increases in the CD4+/CD25bright/FoxP3 subset and CD127 expression was down regulated. When purified Treg populations (CD4/CD25+, CD4/CD25+/CD45RA+ and CD4/CD25+/CD45RO+) were used as fraction for hMSC co-cultures, they maintain FoxP3 expression and CD127 expression is down-regulated. Treg suppressive capacity was maintained in Treg populations that were layered on MSC for up to 15 days while control Tregs lost all suppressive activity after 5 days culture. In conclusion, our study demonstrates that MSCs recruit, regulate and maintain T regulatory phenotype and function over time.

Background In patients with Ph-negative MPN, a prior thrombosis (PrTh) occurs in around 1/5 of cases, with variable platelet (PLT) count and variable distance from diagnosis. Objective To investigate the influence of PLT count at PrTh on diagnostic and therapeutic approach in MPN patients. Material and methods We evaluated 129 MPN patients from RIT, reclassified according to WHO 2008 criteria as ET (n70), initial-primary myelofibrosis (n29), early-PV (n10), and unclassifiable-MPN (n20). Results Patients, 60 males and 69 females, showed following PrTh: 91(71%) major arterial (37 AMI, 4 angina, 24 stroke, and 26 TIA); 12(9%) minor arterial; 22(17%) major venous (8 DVT, 7 splanchnic, 4 cerebral sinus, 3 pulmonary embolism); and 4(3%) minor venous events. PrTh occurred at a median distance of 4.1 months (range 0.1-118) from MPN diagnosis. This distance was >24 months in 21(16%) patients. At occurrence of PrTh, median age was 58 years. PLT count (x109/L) had a median value of 661 (range 150-2200), and was ≤450, 451-600, 601-700, 701-1000, and >1000 in 15(12%), 35(27%), 26(20%), 43(33%), and 10(8%) patients, respectively. Median white blood cell (WBC) count was 9.0 x 109/L and median hematocrit (HCT) value was 46% in males, and 41% in females. Median time (months) from PrTh to diagnosis of MPN was higher (p0.004) in patients with lower PLT count (x 109/L): ≤450 (50.2), 451-600 (11.7), 601-700 (2.7), 701-1000 (1.8), and >1000 (1.4). After occurrence of PrTh, all patients received conventional anti-thrombotic treatment, but in 7(5.4%) patients 9 recurrent thrombosis were reported before MPN diagnosis (11/100 pt-years). At MPN diagnosis, clonality was documented in 101(78%) patients (JAK2 V617F mutation in 96 cases, 74%). The age was >60 years in 61(47%) patients. PLT count (x109/L) had a median value of 720 (166-2440), and was ≤450 (n 7, 5%), 451-600 (n 21, 16%), 601-700 (n 28, 22%), 701-1000 (n 58, 45%), >1000 (n15, 12%). WBC count (109/L) had a median value of 8.9, and was >10 in 40 (31%) cases. Median HCT level (%) was 45.6 in males and 42.1 in females. Cardiovascular risk factors (CVRF), comorbidities and symptoms were documented in 103(80%), 97(75%), and 57(44%) cases, respectively. Thrombotic risk (IPSET-Th) was high in 97.5%, and intermediate in 2.5% of cases. All 129 patients received anti-thrombotic drugs (low dose aspirin in 95% of cases) and, immediately after the diagnosis, they started a cytoreductive treatment (hydroxycarbamide 89%, anagrelide 8%, interferon-alpha 3%). Patients with a PLT count (x109/L) at PrTh ≤600(n 50), as compared with those with a PLT count >600(n 79), showed a longer median time to the MPN diagnosis (16.7 vs 2.0 months, p60 years (52% vs 44%, p0.39); CVRF (82%vs79%, p0.63); WBC >10 x109/L (23% vs 39%, p0.07); HCT high level [>47% in males, >44% in females](28% vs 36%, p0.37), and high thrombotic risk [IPSET-Th] (96%vs99%, p0.56). During follow-up (median 7.9 years) they showed a higher incidence of thrombosis recurrence (30%vs15%, p0.04; 4.5 vs 1.7/100 pt-y, p Conclusion Time to MPN diagnosis was significantly longer in patients with PLT count (x109/L) at PrTh ≤600 vs >600, and this time to diagnosis was characterized by a not negligible thrombosis recurrence. Moreover, during follow-up they showed a higher incidence of thrombosis recurrence. This analysis strongly suggests that a PLT count Disclosures Passamonti: Novartis: Consultancy, Honoraria, Speakers Bureau. Vannucchi:Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Other: Research Funding paid to institution (University of Florence), Research Funding; Shire: Speakers Bureau; Baxalta: Membership on an entity's Board of Directors or advisory committees.

T-cell homeostasis is regulated by several molecules; among these, interleukin (IL)-7 plays an essential role in the survival and homeostatic proliferation of peripheral naive T cells. In a previous study, we investigated whether human mesenchymal stromal cells (MSCs) could be engineered with the IL-7 gene to produce functional level of this cytokine. In the present study, we analyzed the impact of different quantities of IL-7 produced by MSCs on the survival and proliferation of a negative immunoselected naive (CD3(+)/CD45RA(+)) T-cell population. Co-cultivation of peripheral naive T cells with MSCs producing low (16 pg/mL) or high (1000 pg/mL) IL-7 levels or in the presence of exogenous IL-7 (0.01 ng/mL and 100 ng/mL) maintained the CD3(+)/CD45RA(+) naive T-cell phenotype. Chemokine receptor CCR7(+) expression was also maintained among this T-cell population. Naive T-cell molecular characteristics were maintained as assessed by the Vbeta spectratyping complexity score, which showed the maintenance of a broad T-cell repertoire. No Th1 or Th2 differentiation was observed, as assessed by interferon-gamma or IL-4 accumulation. In contrast, only MSCs producing high amounts of IL-7 caused increased activation (CD25 31.2% +/- 12% vs 10% +/- 3.5%; P.05), proliferation (CD71 17.8+/-7% vs 9.3%+/-3, P.05), apoptosis (assessed by annexin V: 18.6% +/- 5% vs 14.9% +/- 2.6%; P.05), and the phase S cell cycle (15% vs 6.9%, P.05). Exogenous IL-7 exhibited no significant effect. In conclusion, we demonstrated that IL-7 produced by MSCs has a dose-independent effect on naive T-cell survival while exerting a dose-dependent effect on activation/proliferation. Due to the continuous production of IL-7 by engineered cells, our system is more efficacious than exogenous IL-7.

Tumor necrosis factor alpha (TNFalpha) is constitutively produced by B-chronic lymphocytic leukemia (B-CLL) cells and may act as an autocrine factor for their growth and survival. However, very few data are available on the possible cytotoxic effect of TNFalpha produced by B-CLL cells. This study investigated whether B-CLL cells exert in vitro cytotoxicity by TNFalpha and if so, whether this cytotoxicity can be modulated by cytokines. In 8 of 12 patients (66.6%), B-CLL cells in vitro constitutively produced TNFalpha and exerted a TNFalpha-mediated cytotoxicity, evaluated in an 18-h 51Cr release assay, against the TNFalpha-sensitive Jurkat, U937 and K562 cell lines but not against the TNFalpha-resistant Raji cell line. Involvement of TNFalpha in B-CLL cell cytotoxicity is demonstrated by the fact that anti-TNFalpha antibodies strongly inhibited it and supernatants of cytotoxic cultures contained TNFalpha and mediated a completely TNFalpha-dependent cytotoxicity. When the cytotoxic B-CLL cells were stimulated with interleukin (IL)-2 plus IL-12, there was increased TNFalpha mRNA expression, TNFalpha production and TNFalpha-mediated cytotoxicity. All eight patients with cytotoxic leukemic cells had progressive disease and six of these also expressed high levels of ZAP-70 protein. In the other four patients (33.3%), B-CLL cells did not produce TNFalpha in vitro and were not cytotoxic, either spontaneously or after IL-2 plus IL-12 stimulation. Of these four patients, three had stable disease and one had progressive disease. The patient with progressive disease and one of the three with stable disease expressed low levels of ZAP-70 protein. We conclude that a group of B-CLL patients with progressive disease have leukemic B cells able to exert in vitro a TNFalpha-mediated cytotoxicity, which is modulated by cytokines.

INTRODUCTION High-dose chemotherapy conditioning regimens for autologous stem cell transplantation generally give similar results in multiple myeloma. We compared two regimens: melphalan versus melphalan plus busulphan. METHODS In all, 30 untreated patients with stage III low-risk multiple myeloma were studied. After induction with three VAD courses and mobilization with cyclophosphamide 7 g/m(2) and recombinant human granulocyte-colony stimulating factor (rHuG-CSF) (10 microg/kg b.w./die), they received melphalan 200 mg/m(2) (arm A) or busulphan 16 mg/kg plus melphalan 100 mg/m(2) (arm B) for conditioning for transplantation. All patients received maintenance therapy with Interferon 3 MU x 3/week. RESULTS Time to engraftment after transplantation was similar in both groups. All patients received rHuG-CSF after reinfusion of peripheral stem cells. No differences emerged in transplant-related infective and noninfective complications. There were no transplant-related deaths. A better response was observed in the melphalan plus busulphan regimen (85 versus 75%, P

In this report we present a case of concurrent B-cell chronic lymphocytic leukaemia and mycosis fungoides in a 69-year-old male patient. The patient originally presented with hepatosplenomegaly and enlarged, bilateral, axillary, and inguinal lymph nodes (maximum diameter of 2 cm). The lungs were clear and heart sounds were normal. The number of whiteblood cells was 56·310 9 /L, haemoglobin concentration was 10·3 g/dL, and the number of platelets was 22710 9 /L; other laboratory tests (such as protein electrophoresis and concentrations of immunoglobulin and b2 microglobulin) were normal except for the concentration of lactate dehydrogenase, which was slightly increased above normal expectations (514 mU/ml). Coomb’s test was negative, as were serological tests for viral hepatitis and HIV. A chest Xray showed chronic bronchitis and an abdominal ultrasound scan showed an enlarged liver (10 cm) and spleen (20 cm). Echocardiography was normal. A peripheral blood smear showed that lymphocytes accounted for 90% of the sample and neutrophils 10%, several Gumprecht’s shadows were also apparent but no prolymphocytes were seen. A bone marrow (figure) and lymph-node biopsy showed interstitial infiltration by small, mature lymphoid cells. The immunophenotype of the neoplastic proportion of the bone marrow aspirate was positive for CD19 (90·5%), CD20 (85%; weak expression), and -light chain (98%), and negative for CD5, CD10, CD103, and -light chain. Although the immunological findings were not typical of a classical phenotype for B-cell chronic lymphocytic leukaemia (B-CLL), in November 2001, the patient was diagnosed with B-CLL, Rai’s stage III, Binet’s stage C. The patient was treated with one cycle of chlorambucil (25 mg/day for 5 days) before treatment was stopped because he developed two lung infections of unknown aetiology. The first infection was treated successfully with imipemen and cilastatin, and the second with trimethoprim, sulfamethoxazole, and clarithromicin. Other complications of the chemotherapy included the development of severe liver toxicity (serum glutamic oxaloacetic transaminase, 251 mU/mL; serum glutamate pyruvate transaminase, 969 mU/mL; alkaline phosphatase, 2134 mU/mL; g-glutamyltransferase, 358 mU/ml; lactate dehydrogenase, 774 mU/mL; total serum bilirubin 2·28 mg/dL), which only resolved after cessation of chlorambucil. Repeated tests for viral hepatitis were negative. The patient’s haemoglobin concentration also decreased and repeated transfusions were needed to normalise the situation. After this short course of chlorambucil, the B-CLL had progressed (number of white blood cells increased to 14010 9 /L, haemoglobin concentration decreased to 7 g/dL, and number of platelets decreased to 9010 9 /L; liver, spleen, and lymph-node diameters were unchanged from the initial diagnosis). There were no signs of Richter Syndrome or pro-lymphocytic leukaemia.

In mammals, methylation of DNA within regulatory sites and histone deacetylase recruitment in transcriptional repressing domains are involved in the loss of the expression of retroviral DNA or repeat arrays transferred in cells for therapeutic purposes. Various investigation results suggest that methylation/deacetylation events are modulated by extracellular and cytoplasmic signal transduction pathways closely involved in regulating cell differentiation. To analyse gene silencing mechanisms and assess if potential pharmacological treatment affects gene silencing kinetics we transduced U937 myelomonocytic cells with a bicistronic retroviral construct carrying the herpes simplex virus thymidine kinase (HSV-TK) and beta-galactosidase (Lac-Z) genes. This vector can be employed in vivo and in vitro to render transduced cell populations susceptible to ganciclovir (GCV). We verified the effect of the histone deacetylase inhibitor Trichostatin A (TSA) alone or combined with 5'-azacytidine (5'aza-C) on transcription downmodulation. Our results indicate that in our in vitro model TSA is able to reactivate transgene expression, more efficiently and with quicker kinetics (12-24h) than 5'aza-C (36-48 h). The effect is dose dependent (between 1 and 50 nM), with no relevant toxicity. Treatment with both drugs is synergistic in gene reactivation in terms of extension and persistence, with low toxicity and no relevant differentiating effects. The cells in which transgene expression has been reactivated undergo progressive silencing, but once weekly drug treatment can maintain high transgene expression levels for more than 90 days with no evidence of selection. The results obtained by treating U937 transduced clones with TSA and/or 5'aza-C together with IL-3, G-CSF or GM-CSF cytokines suggest that transduced U937 differentiation levels do not affect basal expression, but render these cells more responsive to reactivation by TSA or TSA plus 5'aza-C, but not to 5'aza-C alone. In conclusion, the results suggest that in vitro inhibition of histone deacetylase by TSA can interfere with gene silencing mechanisms affecting 5' Moloney murine leukaemia virus long terminal repeat (MoMuLV-LTR) driven transgene expression thus providing the rationale for TSA and/or 5'aza-C administration in animal models for the translation on gene therapy applications.

The herpes simplex virus thymidine kinase (HSV-tk) gene conferring ganciclovir (GCV)-specific sensitivity to transduced cells might control Graft-versus-Leukemia (GvL)/Graft-versus-Host Disease (GvHD). Human T lymphocytes were engineered with an LSN-tk retroviral vector encoding tk and neomycin resistance (NeoR) genes. A total of 80 x 10(6) tk(+) lymphocytes were injected intraperitoneally in NOD-SCID mice. Engraftment was evaluated by human CD45(+)/CD3(+) cytofluorimetric analysis and NeoR-based polymerase chain reaction (PCR) on peripheral blood, bone marrow, liver, thymus, and spleen on day +5. After 14 days, GCV (10 mg/kg daily) cytofluorimetric analysis and PCR were repeated (day +19). Immunohistological studies with anti-CD3 monoclonal antibody followed by alkaline phosphatase and monoclonal anti-alkaline phosphatase staining were performed on spleen and liver at the same time points. Human CD45(+)/CD3(+) cells were engrafted in all tissues on day +5 according to cytofluorimetry, immunohistology, and PCR. Lymphocytes "homed" to the white pulp T-cell area and to the red pulp; liver localization is prevalently at the periportal area. After GCV (day +19), cytofluorimetry and immunohistology showed very few CD3(+) cells. PCR identified the transgene in 22% tissue samples (positive only in thymus and spleen). GvHD did not occur in any animal. These data demonstrate elevated doses of human-transduced CD3(+) cells engraft in NOD/SCID mice; after GCV, very few CD3(+) cells can be detected and those that escape treatment can be found in the thymus and in the spleen on day +19. Lack of full response to GCV may account for cases of GvHD in patients receiving tk-transduced T lymphocytes.

Posttransplant relapse is still a major cause of treatment failure in high-risk acute leukemia. Evidence from experimental bone marrow transplantation (BMT) showed coinfusion of conventional T lymphocytes (Tcons) with regulatory T lymphocytes (Tregs) suppressed lethal Graft-versus-Host Disease (GvHD) without impairing the Graft-versus-Leukemia (GvL) effect (Edinger et al., Nat Med. 2003;9:1144-1150). In HLA haploidentical transplantation for acute leukemia we demonstrated that donor-derived natural Tregs, coinfused with Tcons, protected recipients against GvHD (Di Ianni et al., Blood 2011, 117:3921-3928) and largely prevented posttransplant leukemia relapse, as only 5% of evaluable patients relapsed (Martelli et al., Blood 2014, 124:638-44). The mechanism by which the GvL effect is maintained in the absence of GvHD is still unknown. In humans, naïve CD45RA+ Tregs express CXCR4 and preferentially localize to the bone marrow while memory CD45RO+ Tregs display lower CXCR4 expression and home to the periphery (Booth et al., J Immunol. 2010;184:4317-4326). Since peripheral blood Tregs to be used for adoptive immunotherapy are CD45RO+, we hypothesized that GvL without GvHD might be due to unopposed Tcon alloreactivity in the bone marrow combined with regulated T cell alloreactivity at the periphery. Immunodeficient NSG mice (a total of 40 for each experimental group) received human myeloid or lymphoblastic leukemia (3x106) and HLA mismatched Tregs/Tcons (3x106). Mice that received leukemia and Tcons (without Tregs) cleared leukemia but died of GvHD. Human T cells harvested from their BM, spleen and liver were predominantly (90%) CD8+ and displayed potent alloreactivity (by 51-chromium release at an E:T ratio of 5:1) against human leukemia (lysis = 50% ± 15), autologous to leukemia PHA blasts (lysis = 60% ± 10) and mouse Con A blasts (lysis = 40% ± 8). Mice that received human leukemia and Tcons plus Tregs were rescued from leukemia and survived without GvHD. Human T cells harvested from spleen and liver were composed of CD8+ T cells (40%) and CD4+/FOXP3- T cells (60%). Despite their FOXP3 negativity, purified CD4+ T cells had retained their regulatory function as they inhibited mixed lymphocyte reaction (by 50% at a Tcon/Treg ratio of 1:2). Purified CD8+ T cells displayed no alloreactivity against human leukemia, PHA blasts and mouse Con A blasts. In contrast, human T cells harvested from BM were still predominantly CD8+ and still displayed potent alloreactivity against human leukemia and autologous to leukemia PHA blasts and mouse ConA blasts, suggesting Tcons had retained their alloantigen recognition against human and mouse MHC. Finally, in mice treated with Tregs alone, human T cells were recovered only in the spleen and liver, they displayed a CD4+/FOXP3- phenotype and inhibited mixed lymphocyte reaction. No human T cells were found in the bone morrow, thus showing human CD45RO+ Tregs do not home to the bone marrow. In conclusion, Treg/Tcon adoptive immunotherapy mediates GvL effect in the absence of GvHD because Tcons that home to the bone marrow exert unopposed alloantigen recognition, while Tcons that home to the periphery are blocked by Tregs. Disclosures No relevant conflicts of interest to declare.

Generation of an efficient graft-versus-leukemia (GVL) effect in patients with hematological malignancies who relapse after allogeneic bone marrow transplantation depends in part upon the number of infused T lymphocytes. Currently, a GVL reaction cannot be achieved without inducing concomitant graft-versus-host disease (GVHD); thus, one strategy is to try to modulate this GVL/GVHD ratio. We engineered human T lymphocytes with herpes simplex virus-thymidine kinase and neomycin resistance genes, with an LXSN-derived vector that confers a ganciclovir-specific sensitivity to the transduced T cells. We analyzed proliferation, interleukin-2 production, alloreactivity in a mixed lymphocyte culture, and clonogenicity during the different stages of retroviral infection and G418 selection. Our results confirm that a sufficient number of transduced T lymphocytes can be obtained after selection for clinical studies. Their proliferative activity, alloresponsiveness, and ability to produce and respond to interleukin-2 were retained. Compared with control populations, their clonogenicity, as assessed by limiting dilution assays, was reduced after retroviral infection and G418 selection by 1.6 and 2.9 logs, respectively, with both viral supernatant incubation and coculture procedures. This study shows that infection and selection with the thymidine kinase-neomycin resistance gene retroviral vector significantly reduces the number of functional T lymphocytes. This finding should be taken into account when establishing the dose of T lymphocytes necessary to trigger a modulated GVL/GVHD effect.

We constructed a functional MoMuLV-based bicistronic retroviral vector encoding the herpes simplex virus type I thymidine kinase gene, which induces sensitivity to the prodrug ganciclovir (gcv), and the reporter β-galactosidase gene (MFG-tk-IRES-lacZ). The U937 histiocytic cell line was transduced with this vector, and a clone (VB71) with high-level transgene expression was selected. Severe combined immunodeficient (SCID) mice were injected with VB71 cells to evaluate the role of long terminal repeat methylation in transgene silencing in vivo and to see whether 5-azacytidine (5′ aza-C) demethylating agent prevented it. We found 5′ aza-C maintained gene expression at high level in vitro. In vivo, time to tumor onset was significantly longer in SCID mice receiving the VB71 cells, 5′ aza-C, and gcv compared with animals treated with either 5′ aza-C or gcv alone. The number of injected tumor cells influences tumor onset time and the efficacy of 5′ aza-C and gcv treatment. The standard gcv treatment schedule (10 mg/kg from d + 1 until the onset of tumor) controlled tumor onset better than short-term treatment with high doses. In conclusion, the results extend our previous findings that transgene methylation in vivo may be prevented with an appropriate schedule of 5′ aza-C and gcv.

In this study we describe a new retroviral vector utilizing an internal ribosome entry site (IRES) from encephalomyocarditis virus to co-express two genes. One is the herpes simplex virus type 1 thymidine kinase gene (HSV-TK) which induces sensitivity to ganciclovir, and the second is the bacterial beta-galactosidase gene ( LacZ ) which was revealed by an histochemical staining with 5-bromo-4-chloro-3-indolyl-β- d -galactopyranoside (X-Gal). We enginereed the U937 human cell line to co-express both genes and monitored transduced cells using X-Gal staining. Several transduced clones were selected. The clones exhibiting X-Gal positive cells were sensitive to ganciclovir treatment (1 μg/ml) while X-Gal negative clones were not. Monoclonal cell lines showed a single copy of the provirus integrated in their genome with the TK-IRES- LacZ sequence stably inserted in all clones. The band distribution pattern of the proviral DNA differed only at the long terminal repeat (LTR) level. Northern blot analysis of an X-Gal positive/ganciclovir sensitive clone showed an mRNA band of 6 kb with both LacZ and TK probes. An X-Gal negative/ganciclovir resistant clone was negative with both probes. This report shows: (1) a therapeutic gene can be linked to a marker gene by an IRES element achieving equivalent expression of both proteins; (2) the co-expression of a marker gene makes fluorescein-di-β- d -galactopyranoside staining possible, and consequently separation of cells expressing the LacZ gene by fluorescence activated cell sorting. Thus the cells expressing the HSV-Tk gene are enriched; (3) the use of a marker gene such as LacZ could open up interesting perspectives in gene therapy protocols because of the opportunity to monitor the transduced cells using a simple cytochemical stain.

Deferasirox (DFX) is an iron chelator used to prevent and treat complications related to transfusional iron overload in myelodisplastic syndrome patients (MDS). Intriguingly, DFX treatment induces haematological responses in a consistent percentage of patients whereas other chelators, like deferoxamine (DFO) do not show such an appreciable effect. A body of literature documents a general reduction of oxidative stress in patients treated with DFX but little is known about the direct effect of DFX treatment on hematopoietic stem cells (HSC). Consolidated evidence highlights the importance of redox signalling in the homeostasis of fundamental processes, particularly in controlling the balance between self-renewal and differentiation of stem cells. In this setting, reactive species of oxygen (ROS) would act as secondary messengers, modulating the expression of master transcription factors and regulatory proteins leading or (pre)conditioning stem cells towards differentiation. In the present study we investigated the effect of DFX and DFO on ROS production in hematopoietic stem/progenitor cells (HSPCs) in order to identify a molecular mechanism explaining the differential effect of iron chelators in rescuing altered hematopoiesis. Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood of healthy subjects and incubated for 24 hours with DFO and DFX in a range of doses between 6.2mM and 200mM. Human HSPCs, isolated upon informed consent from peripheral blood of G-CSF-treated healthy donors by immuno-selection against the specific markers CD133 and CD34, were treated with 100 mM DFX or DFO for 24 hours. To completely abrogate ROS production, cells were co-incubated with diphenil iodide (DPI) 100mM, a known inhibitor of the main proteins able to generate ROS: the flavo-oxidases of the respiratory chain and the NADPH oxidases. Cell viability was determined by trypan blue staining. ROS levels were analyzed by laser scanning confocal microscopy (LSCM) and flow cytometry after the incubation at 37°C for 15 minutes with the intracellular H2O2 specific probe dichlorodihhyrofluorescein-diacetate (H2DCFDA) 10mM. b-catenin and BMI1 protein levels were assessed by western blotting. Data were presented as mean±s.e.m. and were compared by unpaired Student T-Test; a p The flow cytometry analysis on PBMCs revealed that DFX, surprisingly, was able to induce ROS production in a dose-dependent manner with a significant increase at 100mM and 200mM compared to CTRL (p=0.02) whereas DFO treatment didn’t show any effect compared to CTRL. Since the cell viability resulted to be not affected by both drugs, the dose of 100mM was chosen for the following experiments performed with HSPCs where the ability of DFX to cause a significant increase of H2O2 was confirmed. A deeper analysis aimed to clarify the localization of ROS released following DFX treatment was performed by LSCM: a significant up-regulation of mitochondrial ROS induced by DFX and not by DFO was clearly observed compared to untreated samples. Importantly, the addition of DPI strongly reduced the entity of the signal detected by DCF (p=0.01 versus DFX). In order to understand a possible link between ROS production and the ability of DFX to restore the hematopoiesis, the expression of b-catenin and BMI1, both of them sensitive to the intracellular redox state and involved in the hematopoietic function, was analysed by western blotting. It was shown that DFX significantly reduced the expression of both b-catenin, strictly linked to hematopoietic function and BMI1 (p=0.02 versus CTRL), a regulatory protein sustaining immaturity and required for the maintaining of adult self-renewing hematopoietic stem cells. Conversely, no significant variation was observed by DFO treatment. Interestingly, the b-catenin and BMI-1expression downregulations, specifically induced by DFX, were completely reversed by ROS abrogation obtained by DPI treatment. Our results show, for the first time, that DFX treatment, independently on its iron-chelating property, is able to induce ROS production that in turn influences key factors involved in self-renewal/differentiation of hematopoietic stem cells. In this scenario, the modulation of ROS, because of their ability to restore the hematopoietic function, could be taken in account as potential further pharmacological target in MDS treatment. Disclosures: No relevant conflicts of interest to declare.

In HLA-haploidentical stem cell transplantation we showed adoptive immunotherapy with naturally occurring T regulatory cells (nTregs) followed by conventional T cells (Tcons) prevented acute and chronic graft-versus-host-disease (GvHD), favoured lymphoid reconstitution and immunity against pathogens (Di Ianni et al., Blood 2011). One major concern is whether a graft-versus-leukemia (GvL) effect is maintained since FoxP3+Tregs can also suppress immune response against tumour. However, we showed in immunodeficient NSG mice engrafted with human myeloid and lymphoblastic acute leukemia cells (7x106 iv), Treg (3x106)+Tcon(3x106) infusion rescued mice from leukemia death in the absence of GvHD. In contrast, controls died of leukemia (when not treated or infused with Tregs only) or of GvHD (when infused with Tcons only).Since September 2008, 45 consecutive patients (21 male; 24 female; median age 40, range 20-59) with high-risk acute leukemia ( 33 AML, 12 ALL) were transplanted. The conditioning regimen included TBI, thiotepa, fludarabine and cyclophosphamide (25 patients in the 1st clinical trial) or alemtuzumab/ATG (20 patients in the 2nd clinical trial). On day -4, patients received an infusion of freshly isolated donor Tregs (mean 2.5/kg ±1; Foxp3 81.01%±16.47; Helios/FoxP3 54%±8.4; CD127 11.72%±7.653) followed on day 0 by a megadose of purified CD34+ cells (9.7x106/kg ± 3.1) and Tcons (mean 1.1 /kg ±0.6; CD3 90.72%± 9.6; CD4 57.77% ± 8.85; CD8 31.21% ± 8.59). No post-transplant GvHD prophylaxis was given. 43 of the 45 patients achieved primary, sustained full-donor type engraftment. Only 6/43 evaluable patients developed ≥ grade II acute GvHD (3 alive, treated and now off-therapy). At a median follow-up of 28 months (range 4-58) no patient has developed chronic GvHD. CD4 and CD8 counts reached 100/µL medianly on days 40 (range 25-150) and 45 (range 18-100) and 200/µL on days 55 (range 45-160) and 60 (range 50-140). In KIR-ligand mismatched transplants (Ruggeri et al., Science 2002; Ruggeri et al., Blood 2007), donor versus recipient alloreactive NK cells were also preserved. At a median follow-up of 46 months (range 7-58) 23/43 patients are alive and disease free with a probability of DFS of 0.56. The cumulative incidence of TRM is 0.37. The cumulative incidence of relapse was 0.06 as only 2 AML patients transplanted from non-NK alloreactive donors have relapsed to date. This incidence is extremely low considering the high-risk patient population (9 with FLT-3/ITD; 8 with complex karyotypes; 4 with t(9:22); 2 PIF; 1 secondary AML; 1CR after second-line induction; 1 with CNS and skin localization at diagnosis; 19 ≥ 2CR). In conclusion, adoptive immunotherapy with Tregs and Tcons exerts a powerful GVT activity in both AML and ALL patients in the absence of GvHD. Disclosures: No relevant conflicts of interest to declare.

Abstract 2299 Introduction Hematopoietic stem cells (HSCs) constitute a reservoir of undifferentiated cells that can be committed, upon appropriate stimuli, in the haematic lineages. Although residing in a bone-marrow hypoxic microenvironment (niche) and mainly relying on anaerobic glycolysis, HSCs are endowed with mitochondria. Recently, specific interest has been focused on HSCs mitochondria and on their role as reactive oxygen species (ROS) generators during the early phases of commitment. Indeed, consolidated evidences highlight the importance of redox signalling in the homeostasis of fundamental processes in cell adaptive biology and particularly in controlling the balance between self-renewal and differentiation of stem cells. HSCs constitutively generate low levels of ROS produced by both mitochondrial respiratory chain and NADPH oxidases (NOXs). ROS would act as secondary messengers, modulating the expression of master transcription factors leading or (pre)conditioning stem cells towards differentiation. Myelodisplastic syndrome (MDS) is characterized by disturbance of the HSC differentiation and most MDS patients are treated with iron chelators to compensate for the iron overload consequent to the blood cell transfusion-based standard therapy. Intriguingly, a robust percentage of patients, treated with the iron chelator deferasirox (DFX), recover correct HSCs differentiation whereas other chelators, like deferoxamine (DFO) did not. In the presented study we investigated the effect of DFX and DFO on the redox homeostasis of hematopoietic stem/progenitor cells (HSPCs) in order to get insights on the differential effect of iron chelators in rescuing altered hematopoiesis. Materials and Methods Human HSPCs were isolated from peripheral blood (PB) or bone marrow (BM) of G-CSF-treated or untreated healthy donors, respectively, by immuno-selection against the specific markers CD133 and CD34 and resulted >99% immunophenotypically homogeneous. Mitochondrial respiratory activity was measured in intact HSPCs by high resolution oxymetry. Morpho-functional features of HSPC-mitochondria, expression of the HSPC-surface commitment markers and ROS level were analyzed by laser scanning confocal microscopy (LSCM) and flow cytometry using specific probes or antibodies. HSPCs were treated with 100 mM DFX or DFO for 24 hrs. Results Measurement of oxygen consumption rate as well as molecular analyses in PB-HSPCs confirmed a poor mitochondrial oxidative phosphorylation phenotype. LSCM imaging of mitochondria in either PB- and BM-HSCs displayed a punctuate rather than interconnected network. However, co-staining of mitochondria and CD34/CD133 stemness-markers revealed a striking inverse correlation. Finally HSPCs produced DCF-detectable and DPI-inhibitable ROS attributable to constitutive NOX activity and related to stabilization of the hypoxia-inducibile factor (HIF1a) under normoxic condition. DFX treatment of HSPCs resulted in a significant up-regulation of ROS level whereas no significant change was observed following DFO treatment. Importantly, the DFX-mediated ROS production was insensitive to treatment with low NOX-inhibiting concentration of DPI but was abrogated by high concentration of DPI thus pointing to mitochondria as ROS source. Conclusions Our results show that HSCs in the early phase of commitment undergo a progressive increase of mitochondrial mass indicating the need of a bioenergetic up-regulation to cope with the oncoming energy-demanding proliferative/differentiative phenotype. Redox signaling, mediated by ROS production and likely triggered by changes in the environmental oxygen tension, appears to be essential in regulating HSC self-renewal and preservation of pluripotency. DFX treatment, by modulating ROS production, might lead to activation of redox-sensitive key factors able to restore the hematopoietic function in MDS patients. This effect seemingly is independent on the iron-chelating property of DFX but pertains to additional pharmacological properties that warren further investigation. Disclosures: No relevant conflicts of interest to declare.

Abstract 4 Transplantation of large numbers of highly purified CD34+ cells from haploidentical relatives is a viable strategy for the cure of acute leukaemia at high risk of relapse (Aversa et al., NEJM 1998; JCO 2005). As extensive T cell depletion is required to prevent GvHD, the very narrow T cell repertoire in the inoculum delays recovery of immune response against pathogens, leading to a high incidence of infection-related deaths. Thus the key challenge is to improve immune recovery by administering allogeneic donor T cells without causing GvHD. Preclinical studies demonstrated that freshly isolated or ex vivo expanded T regulatory cells (Tregs) could be used to control GvHD following bone marrow transplantation. The present phase I/II clinical trial evaluated the impact of early infusion of freshly isolated donor CD4/CD25+ Tregs, followed by an inoculum consisting of donor mature T cells (Tcons) and positively immunoselected CD34+ cells, on GvHD prevention and immunological reconstitution. Twenty-two patients (10 male; 12 female; median age 40.5, range, 21 to 60) with AML (n=17; 8 in CR1 at high risk, 7 in ≥CR2 and 2 in relapse), ALL (n=4; 3 in CR1; 1 in relapse) and 1 with high grade NHL in relapse were enrolled from September 2008 onwards. The conditioning regimen consisted of 8Gy single fraction TBI, thiotepa (4 mg/kg×2), fludarabine (40mg/m2×4), and cyclophosphamide (35 mg/kg×2). All patients received CD4/CD25+ GMP immunoselected Tregs (CliniMACS, Miltenyi Biotec) (21/22 2×106/kg bw; 1/22 1×106/kg bw). Three days later they received positively immunoselected CD34+ cells (median 8.2, range 5.0-19.1) together with Tcons (16/22 1×106/kg bw; 4/22 0.5 ×106/kg bw; 2/22 did not receive Tcons). Immunoselected CD4/CD25+ Tregs (purity 91.5±4.5) consisted of CD25high 25.6%±11.2; CD25int 57.4%±5.9; CD25low 8.5%±6; FoxP3 64%±1; CD127 14.9%±13.7 (mean±SD). As suggested by in vitro immunosuppressive assays and by immunophenotypic analysis, the contaminating cells in the Treg fraction were 50% of the CD25int and 100% of the CD25low, so that the infused Tregs:Tcons ratio was established at 1:1.5. No post-transplant prophylaxis against GvHD was used. 20/22 patients engrafted. Neutrophils reached 1×109/L at a median of 15 days (range, 11 to 39 days). Platelets reached 25×109/L and 50×109/L at median of 13 and 15 days, respectively (range, 11 to 48 days, and 13 to 60 days). All engrafted patients showed persistent full donor-type chimerism in peripheral blood and bone marrow. Strikingly, no GvHD was observed in 17/20 valuable patients, 2/20 developed grade I cutaneous self-limited untreated GvHD and 1/20 developed grade III GvHD. This patient had received the fewest Tregs. Six patients died (1 bacterial sepsis, 2 VOD, 1 fungal pneumonia, 1 CNS aspergillosis and 1 GvHD/systemic toxoplasmosis). In contrast with our previous experience, the speed of immune recovery was enhanced. The CD4 and the CD8 counts reached, respectively, 50/μL medianly on days 34 (range, 19 to 63 days) and 24 (range, 15 to 87); 100/μL medianly on days 47 (range, 28 to 100 days) and 34 (range, 19 to 95); 200/μL on days 70 (range, 41 to 146 days) and 61 (range, 21 to 95). We also observed a rapid development of a wide T-cell repertoire and detection of high frequencies of specific CD4+ and CD8+ for opportunistic pathogens such as Aspergillus, Candida, CMV, ADV, HSV, VZV, Toxoplasma. In KIR ligand-mismatched transplants, speed of NK cell reconstitution/maturation and size of donor vs recipient alloreactive NK cell repertoires were preserved (Ruggeri et al., Science 2002). In conclusion, in the setting of haploidentical transplantation infusion of freshly purified Tregs makes administration of high dose of T cells feasible for the first time. This strategy provides a long-term protection from GvHD and robust immune reconstitution. Treg-based cellular therapy may represent an innovative strategy to improve the outcome of haploidentical transplants. Disclosures: No relevant conflicts of interest to declare.