The Challenge Of HSCs Procurement For Gene Therapy: Exploring Plerixafor As Mobilization Agent

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2901-2901
Author(s):  
Maria Rosa Lidonnici ◽  
Annamaria Aprile ◽  
Marta Claudia Frittoli ◽  
Giacomo Mandelli ◽  
Bernhard Gentner ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Peripheral Blood ◽  
Conflicts Of Interest ◽  
Transduction Efficiency ◽  
Beta Thalassemia ◽  
Hematopoietic Stem ◽  
Cell Dose ◽  
Nsg Mice ◽  
Molecular Features ◽  
Cd34 Cells

Abstract Successful gene therapy of inherited blood diseases relies on transplantation and engraftment of autologous genetically engineered hematopoietic stem/progenitor cells (HSPCs) in myeloablated patients. Hematopoietic reconstitution and clinical benefit are related to cell dose, although single disease features might play a role favoring selection of relevant progenitor populations. Gene therapy trials in young pediatric patients are performed isolating CD34+ cells from bone marrow (BM), while in adults mobilized peripheral blood stem cells (PBSC) should represent the favorite target. In the context of gene therapy for thalassemia, the choice of HSPC source is crucial since intrinsic characteristics of patients (splenomegaly and thrombophilia) dictate caution in the use of G-CSF as mobilization agent and prompt investigation of new agents. Moreover, adult thalassemic patients may possibly have a decreased BM stem cell reservoir, due to the BM suppression in response to multiple transfusions. A phase II clinical protocol exploring the use of Plerixafor as a single mobilizing agent in adult patients affected by transfusion dependent beta-thalassemia (EudraCT 2011-000973-30) started in 2012 at our hospital. Plerixafor selectively and reversibly antagonizes the binding of SDF-1 to its receptor CXCR4 with subsequent egress of HSCs to the peripheral blood. The availability of a new source of HSPCs, potentially superior in terms of CD34+ cell yield, transduction efficiency and biological features to steady-state BM, would have a significant impact on the feasibility and efficacy of gene therapy. Four subjects were enrolled and treated by subcutaneously administration of Plerixafor at the single dose of 0.24 mg/kg followed by leukoapheresis. Mobilization of CD34+ cells occurred very rapidly with a peak between 7 to 9 hrs. Three out of four patients achieved the minimal target cell dose (2 x 106 cells/kg) and no severe adverse event occurred. To the aim of engineering Plerixafor-mobilized CD34+ cells for gene therapy, we performed a comprehensive characterization of their biological, molecular and functional properties. In vivo reconstitution potential and lympho-myeloid differentiation were tested following transplantation in NSG mice and compared to those of PBSCs mobilized by G-CSF. Percentages of engrafted human cells in NSG mice transplanted with Plerixafor -PBSCs were about 2- to 5-fold higher than those found in mice transplanted with G-CSF PBSCs. On the same line, the SRC frequency, obtained by pooled engraftment data, was significantly higher (1 SRC out of 47.875 CD34+ cells vs.1 SRC out of 141.203 CD34+ cells). The phenotypic analysis of the frequency of primitive hematopoietic sub-populations revealed that Plerixafor mobilizes preferentially HSPCs and LT-HSPCs, with a percentage of CD34+ CD38-/low CD90+ CD45RA- CD49f+ cells higher than that found in G-CSF PBSCs. This result mirrors the enhanced number of SRCs found in the CD34+ cell population mobilized by Plerixafor. In order to further define the molecular features of HSPCs from different sources, we are studying signalling networks in response to specific cytokines by phospho-proteins analysis and gene expression by microarrays analysis. Our studies are focused on self-renewal, homing, engraftment and multilineage differentiation processes and bioinformatic analysis will reveal the molecular machinery underlying 'stemness' properties of Plerixafor mobilized cells. Disclosures: No relevant conflicts of interest to declare.

Retroviral transduction efficiency of G-CSF+SCF–mobilized peripheral blood CD34+ cells is superior to G-CSF or G-CSF+Flt3-L–mobilized cells in nonhuman primates

Blood ◽  
2003 ◽  
Vol 101 (6) ◽  
pp. 2199-2205 ◽  
Author(s):  
Peiman Hematti ◽  
Stephanie E. Sellers ◽  
Brian A. Agricola ◽  
Mark E. Metzger ◽  
Robert E. Donahue ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Peripheral Blood ◽  
Nonhuman Primates ◽  
Transduction Efficiency ◽  
Target Cells ◽  
Hematopoietic Stem ◽  
Retroviral Transduction ◽  
Peripheral Blood Cd34 ◽  
Cd34 Cells ◽  
Clinical Gene Therapy

Gene transfer experiments in nonhuman primates have been shown to be predictive of success in human clinical gene therapy trials. In most nonhuman primate studies, hematopoietic stem cells (HSCs) collected from the peripheral blood or bone marrow after administration of granulocyte colony-stimulating factor (G-CSF) + stem cell factor (SCF) have been used as targets, but this cytokine combination is not generally available for clinical use, and the optimum target cell population has not been systematically studied. In our current study we tested the retroviral transduction efficiency of rhesus macaque peripheral blood CD34+ cells collected after administration of different cytokine mobilization regimens, directly comparing G-CSF+SCF versus G-CSF alone or G-CSF+Flt3-L in competitive repopulation assays. Vector supernatant was added daily for 96 hours in the presence of stimulatory cytokines. The transduction efficiency of HSCs as assessed by in vitro colony-forming assays was equivalent in all 5 animals tested, but the in vivo levels of mononuclear cell and granulocyte marking was higher at all time points derived from target CD34+ cells collected after G-CSF+SCF mobilization compared with target cells collected after G-CSF (n = 3) or G-CSF+Flt3-L (n = 2) mobilization. In 3 of the animals long-term marking levels of 5% to 25% were achieved, but originating only from the G-CSF+SCF–mobilized target cells. Transduction efficiency of HSCs collected by different mobilization regimens can vary significantly and is superior with G-CSF+SCF administration. The difference in transduction efficiency of HSCs collected from different sources should be considered whenever planning clinical gene therapy trials and should preferably be tested directly in comparative studies.

Limitations of G-CSF Mobilization in Splenectomized Patients with Beta-Thalassemia Major: Implications for Thalassemia Gene Therapy.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2150-2150
Author(s):  
Evangelia Yannaki ◽  
Thalia Papayannopoulou ◽  
Erica Jonlin ◽  
Ioannis Batsis ◽  
Pamela S. Becker ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Splenic Rupture ◽  
Conflicts Of Interest ◽  
Thalassemia Major ◽  
Adult Patients ◽  
Cell Yield ◽  
Beta Thalassemia ◽  
Limited Information ◽  
Hematopoietic Stem ◽  
Cd34 Cells

Abstract Abstract 2150 Poster Board II-127 For gene therapy (GT) of thalassemia (TH), high numbers of genetically-modified hematopoietic stem cells (HSCs) are required to effectively compete for niche space in the hypercellular thalassemic bone marrow (bm). Mobilized peripheral blood is the preferable source of HSCs for thalassemia GT due to higher yields of CD34+cells compared to bm harvest. There is limited information on the mobilization efficacy of adult patients with major β-TH as well as on the safety of the procedure in a condition of splenomegaly and extramedullary hemopoiesis. Rare events of splenic rupture or thrombosis with G-CSF in normal donors raise safety concerns for its use in TH where chronic splenomegaly and hypercoagulability exist. Pretreatment of patients with hydroxyurea (HU) could reduce the risk of splenic rupture or thrombosis by decreasing the splenic hemopoiesis and thereby the spleen size in the non-splenectomized (non-SPL), and the circulating cells in the splenectomized (SPL) patients before G-CSF. In an on going mobilization study, we aim to assess the safety and efficacy of G-CSF mobilization with or without HU pretreatment in adult patients with β-TH major. Sufficient mobilization is considered to be the yield of ≥2×106CD34+cells/kg/2aphereses. Sixteen patients have been enrolled so far, 9 SPL and 7 non-SPL. One non-SPL patient withdrew during the study. Six SPL and 4 non-SPL patients received HU pretreatment (20mg/kg/d the non-SPL, 25-30mg/kg/d the SPL) for 1 month before G-CSF. There was a 1-2 weeks' interval between HU cessation and G-CSF initiation. No severe adverse events were observed. In non-SPL patients, HU decreased the spleen volume over baseline (306cm3 vs 536cm3, p=0,03) resulting in 9% max increase during mobilization compared to 45% size increase in patients w/o HU pretreatment. In non-SPL patients, HU negatively affected the CD34+yield when the ‘wash-out' period before G-CSF was 8 days (mean CD34+cells 1,86±0,76×106/kg/2aphereses, n=2). However, when the interval period from the HU stop to the G-CSF initiation increased up to 18 days allowing for bm recovery after the myelosuppressive effect of HU, mobilization was successful (P12:CD34+cells 6,5×106/kg/2aph). Non-SPL patients w/o HU pretreatment (n=3) yielded adequate numbers of HSCs (CD34+cells:5,8±3,89×106/kg/2aph). Surprisingly, CD34+cell yields were very low in the first 2 non-HU pretreated SPL patients (CD34+cells:0,98±0,14×106/kg/2aph). This was due to the development of early excessive leukocytosis (mean max WBCs 81×109/l, day 3) with the regular 10mcg/kg/d G-CSF dose, which necessitated dose hold or therapeutic leukapheresis and resulted in loss of the CD34+cell peak in blood. However, when mobilization started with lower (2,5mcg/kg/d) and adjusted to the WBCs doses of G-CSF (mean daily dose 3,21mcg/kg) and aphereses were initiated later (day6), CD34+cell yield markedly improved (P15:4,5×106/kg/2aph) without inducing early excessive leukocytosis (max WBCs 67×109/l, day 5). In SPL patients, HU was shown to decrease the high PLT and WBC numbers before G-CSF (PLTs:from 640±132×109/l at baseline to 240±53×109/l, p=0,0002 / WBCs:from 20,23±15,8×109/l at baseline to 11,47±6,11×109/l, p=0,23) potentially reducing the risk of thrombosis and partially preventing excessive leukocytosis during mobilization (max WBCs SPL-HU:51,68±29,37×109/l vs SPL-no HU:74,77±8,78×109/l, p=0,23). HU pretreatment negatively affected the yield in SPL patients when the ‘wash-out' period before G-CSF was 7-10 days (mean CD34+yield 0.62±0,41×106/kg/2aph, n=5). However, when the interval period from HU stop to G-CSF initiation increased up to 12 days, mobilization was successful (P16:CD34+cells 3,8×106/kg/2aphereses). G-CSF dose adjustment was also needed in HU-pretreated SPL patients with WBCs≥14,6×109/l before G-CSF (P9,P16). Overall, it seems that mobilization of SPL thalassemic patients is challenging. Mobilization is not inherently inefficient in SPL patients but it results from mandatory G-CSF-dose modifications to avoid hyperleukocytosis. Patient-tailored schemes of G-CSF mobilization or alternative ways of mobilization (ie AMD 3100) will be required in order to obtain high numbers of HSCs from SPL patients. HU seems to play a safety role as pretreatment before mobilization, especially in the SPL patients, however the time to G-CSF initiation after HU cessation is critical for a sufficient CD34+cell yield. Disclosures: No relevant conflicts of interest to declare.

Plerixafor Single Agent for Autologous Stem Cells Mobilization and Collection in Adult Thalassemic Patients: Towards the Assessment of the Suitable Hematopoietic Stem Cell Source for Gene Therapy of Beta-Thalassemia.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 586-586
Author(s):  
Marta Claudia Frittoli ◽  
Bernhard Gentner ◽  
Maria Rosa Lidonnici ◽  
Annamaria Aprile ◽  
Laura Bellio ◽  
...  
Keyword(s):  
Stem Cells ◽  
Gene Therapy ◽  
Steady State ◽  
Peripheral Blood ◽  
Single Agent ◽  
Beta Thalassemia ◽  
Target Cells ◽  
Beta Globin ◽  
Hematopoietic Stem ◽  
Cd34 Cells

Abstract Abstract 586 Gene therapy of inherited blood diseases requires harvest of hematopoietic stem cells (HSCs) from patients and autologous transplantation of genetically modified cells. In order to achieve correction of the disease, high number of HSCs and previous conditioning of the host bone marrow (BM) are necessary. In the clinical application of gene therapy for thalassemic patients the choice of the HSC source is a crucial issue. On one side, the minimal target dose poses a challenge for the use of steady state BM since reinfusion of high numbers of beta globin gene modified CD34+ cells is probably necessary to gain sufficient correction of the genetic defect in order to achieve transfusion independency; on the other side, the disease related features and complications of thalassemic patients (i.e. splenomegaly and thrombophilia) dictate caution in the use of G-CSF as mobilizing agent. In April 2011 a clinical protocol exploring the use of Plerixafor (AMD3100) as single agent was started (“Plerixafor mobilized stem cells as source for gene therapy of beta-thalassemia”, acronym AMD-THAL, EudraCT2011-000973-30). Aims of the trial were to explore the ability of Plerixafor in inducing safe and effective stem cells mobilization in adult patients affected by beta-thalassemia, to characterize stem/progenitor cells mobilized from the BM and peripheral blood of treated subjects and to achieve gene transfer efficiency of mobilized CD34+ cells at a level comparable to that obtained using steady state BM. Four patients (01, 02, 03 and 04) were enrolled and already mobilized to date (August 2012). All patients are affected by transfusion dependent beta-thalassemia and aged 28 (01), 41 (02), 39 (03), 33 (04). Two are splenectomized (02 and 03); all subjects are regularly iron chelated with adequate organ function. Administration of Plerixafor subcutaneously as single agent and at the single dose of 0.24 mg/kg resulted in mobilization of CD34+ cells/mcl with a peak of 78 cells at 9 hrs (01), 70 cells at 7 hrs (02) and 69 cells at 8 hrs (03); suboptimal mobilization was observed in patient 04 (peak 18 at 8 hrs). Patient 03 received a second dose at 0.40 mg/kg 24 hrs after the first dose and underwent a second leucoapheretic procedure. Harvest by leukoapharesis resulted in procurement of the following CD34+ cells/kg: 1.84 × 106 (01) and 4.43 × 106 (02) with a unique leukoapheretic procedure, and 3.57 × 106 (03) with two leukoapheresis. No apheresis was performed for patient 04 because the minimum target of 20 CD34+ cells/mcl in peripheral blood was not reached. CD34+ cells selection through Clinimacs Miltenyi resulted in the following yield: 1.2 × 106 CD34+ cells/Kg, 65% recovery (01), 2.66 × 106 CD34+ cells/Kg, 60% recovery (02), 1.78 × 106 CD34+ cells/Kg, 50% recovery (03). No severe adverse event occurred. Recorded side effects were: grade 3 hypotension related to the apheretic procedure (01), mild grade 1 facial disestesia (02 and 04) and hyperleukocytosis (02: WBC from 13.6 to 42.6 × 103/mcl). In addition, steady state and Plerixafor primed BM aspirates were performed to analyze any modification in CD34+ concentration in the BM following Plerixafor administration. In fact, Plerixafor administration resulted in enrichment of CD34+ cells concentration in the BM. Purified CD34+ cells from leukoapheresis of the 4 treated patients were analyzed for their biological and functional properties, subpopulations composition and expression profile. In vivo reconstitution potential and lymphomyeloid differentiation of CD34+ cells were tested following transplantation in NSG mice. Experiments are ongoing but preliminary results indicate that cells mobilized by Plerixafor have a primitive phenotype with a high reconstitution potential and are efficiently transduced with a lentiviral based vector, named GLOBE, encoding for the human beta-globin (Roselli et al., 2010), thus being a suitable source of target cells for gene therapy. Disclosures: No relevant conflicts of interest to declare.

Intrinsic Molecular Features of Human Hematopoietic Stem Cells from Different Sources Define Their Specific Functional Properties

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3069-3069
Author(s):  
Maria Rosa Lidonnici ◽  
Annamaria Aprile ◽  
Marta Frittoli ◽  
Giacomo Mandelli ◽  
Ylenia Paleari ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Peripheral Blood ◽  
Cell Frequency ◽  
Hematopoietic Stem ◽  
Nsg Mice ◽  
Molecular Features ◽  
Cd34 Cells ◽  
Different Sources

Abstract Over the past decades outcomes of clinical hematopoietic stem cell transplants have established a clear relationship between the sources of hematopoietic stem cells (HSCs) infused and their differential homing and engraftment properties. For a long time, bone marrow (BM) harvest has been the preferred source of hematopoietic stem and progenitor cells (HSPCs) for hematopoietic reconstitution following myeloablative conditioning regimen. At present, mobilized peripheral blood (PB) is commonly used for hematopoietic cells transplantation in both adults and children, particularly in the autologous setting, and it has progressively replaced BM as the source of HSCs. So far, the intrinsic molecular features of human primitive HSCs from different sources have not been investigated in comparative studies to unravel their variable reconstitution potential. Diverse strategies are currently used to disengage HSCs from the niche, promoting egress from BM to PB. Traditionally the growth factor granulocyte-colony stimulating factor (G-CSF) represents the gold standard agent to mobilize HSPCs for transplantation. Nevertheless, many other compounds have been tested to this regard. One of the most successful mobilizing agents is Plerixafor (AMD3100, Mozobil™), a bicyclam molecule that selectively and reversibly antagonizes the binding of stromal cell derived factor-1 (SDF-1), located on the surface of BM stromal cells and osteoclasts, to chemokine CXC-receptor-4 (CXCR4), located on the surface of HSPCs, with the subsequent mobilization in the PB. This drug, which was shown in preclinical combination studies with G-CSF to enhance mobilization compared to G-CSF alone, is currently approved by FDA and EMA "in combination with G-CSF to enhance the mobilization of HSCs into the peripheral blood for collection and autologous transplantation of patients affected by lymphoma or multiple myeloma whose cells mobilize poorly" We investigated functional and molecular hallmarks of human HSCs from different sources, i.e. BM and PB following mobilization by G-CSF and/or Plerixafor. We show that Plerixafor alone mobilizes preferentially long-term hematopoietic stem cells (LT-HSCs), defined as CD34+ CD38/low CD90+ CD45RA- CD49f+ cells and primitive populations of HSCs. These cells are able to provide stable long-term hematopoietic engraftment in NOD/SCID/IL2rγnull (NSG) mice, resulting in enriched scid-repopulating cell frequency, in comparison to other sources. The quiescence status of these cells correlates with the enriched scid-repopulating cell frequency. Noteworthy, the combined use of G-CSF and Plerixafor mobilizes a CD34+ population enriched in immature cells and with a lower engraftment capacity respect to cells mobilized by Plerixafor alone. Since the signaling provided by the interaction of SDF-1 with CXCR4, plays an essential role in maintaining HSC quiescence and regulating homing, we analyzed the CXCR4 expression. Interestingly, this analysis reveals that the proportion of CXCR4+ primitive cells was lower when using G-CSF combined to Plerixafor in respect to Plerixafor alone. These data indicate that the combination of the two mobilizing agents induce a higher amount of circulating CD34+ cells but containing a lower proportion of cells capable of homing to BM in NSG mice. . As a result, at a defined dose of transplanted CD34+ cells, less SRCs are observed when G-CSF is added to Plerixafor. Indeed, it is expected to observe also a rapid rescue of hematopoiesis in myeloablated subjects conferred by high amount of short-term progenitors. Insights into the transcriptional program reveal the molecular machinery underlying stemness features of cells derived from different sources, defining their specific functional properties. Noteworthy, CD34+ cells exposed to Plerixafor but still resident in the BM acquire an intermediate signature between steady-state and circulating cells, suggesting an effect of this agent on HSC function. From preliminary data, genes of Prostaglandin signaling are up-regulated in HSCs mobilized by Plerixafor, suggesting a role of this pathway. These data uncover unique HSCs properties shaped by their origin and illuminate the choice of different transplantation strategies accordingly to the clinical need. Disclosures No relevant conflicts of interest to declare.

Hematopoietic Stem Cell Mobilization for Gene Therapy: The Combination of G-CSF+Plerixafor in Patients with Beta-Thalassemia Major Provides High Yields of CD34+ Cells with Primitive Signatures

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 4412-4412
Author(s):  
Elena Baiamonte ◽  
Rita Barone ◽  
Rosalia Di Stefano ◽  
Melania Lo Iacono ◽  
Barbara Spina ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Stem Cell ◽  
Hematopoietic Stem Cell ◽  
Peripheral Blood ◽  
Total Yield ◽  
Thalassemia Major ◽  
Vitro Assay ◽  
Hematopoietic Stem ◽  
Cell Dose ◽  
Cd34 Cells

Abstract Hematopoietic stem cell engineering is a promising therapy to cure b-thalassemia, in particular for patients who lack a suitable BM donor for allogeneic transplantation. Since the engrafted gene-corrected stem cells will not have any selective advantage over the unmodified ones, the effectiveness of the therapy in this setting largely depends on the infusion of high numbers of gene-modified cells and on the conditioning regimen. The quality of the infused cells is also crucial for the clinical outcome and the duration of the therapeutic effect. HSPCs mobilization, particularly when G-CSF and plerixafor are used in combination, has been proved to be the optimal approach to harvest a large number of CD34+cells in patients with hematological malignancies and in healthy volunteers. However adult heavily-transfused thalassemia patients have intrinsic characteristics that may adversely affect both the safety and the efficacy of mobilization. We conducted a clinical trial to investigate the safety and effectiveness of mobilizing HSPCs with G-CSF+plerixafor in adult patients affected by β-thalassemia major with the aim to reach a cell dose of ≥8x106 CD34+cells/Kg. We studied the kinetic of CD34+cells during mobilization and performed a comprehensive characterization of their molecular and functional properties. All patients completed the mobilization according to the protocol (G-CSF 10 μg/kg/day for four days, followed by plerixafor 240 μg/kg in the evening on day 4) and no serious adverse events occurred. Leukapheresis was done 10-12 hours after plerixafor (on day 5). Three of the four patients reached the target cell dose or more in single-apheresis collections, even one patient where a significant dose reduction of G-CSF was halved due to early hyperleukocytosis. For one patients the number of cells collected in the first apheresis was slightly below the established target and therefore, according to the protocol, she was subjected to a second apheresis on day 6, after an additional dose of plerixafor. The total yield from the combined apheresis in this patient was 13.0 CD34+cells /Kg. CD34+ cell yields per single apheresis in our patients were comparable to those in healthy donors (12 pts) mobilized in our hospital with G-CSF alone. A significant increase in the mean peripheral blood CD34+ cells (12.1± 8.2 fold), was unanimously observed after plerixafor addiction. The frequencies of the more primitive CD34+cell subtypes (CD34+CD38- and CD34+CD38-133+) as well as the clonogenic capacity tested in short term in vitro assay were found significantly increased too. Comprehensive microarray analysis of genes expressed in the CD34+ cells purified from the same patient upon mobilization with G-CSF alone (G/CD34+cell) and with G-CSF+plerixafor (G+pl/CD34+cell) highlighted a different HSCs repertoire. According to the mechanism of plerixafor mobilization, CXCR-4 gene expression was found 5-fold higher in G+pl/CD34+cells. CXCR-4 gene is known to be expressed on the surface of more primitive CD34+ HSCs with long-term repopulating potential and plays a central role in the regulation of adhesion of them to native niche in the BM. A substantial number of genes with previously shown implication in mechanisms of homing and engraftment (CXCR4, CD82, DPP4, ROBO4), or genes linked to stress resistance (CXCL4, SOD2, IL8, PPBP) as well as several chemokines genes involved in cell mobility (CXCL2, CXC3, CXCR2) were also found to be up-regulated in G+pl/CD34+cells. Overall, the yields, the primitive signatures of CD34+cells indicate the G-CSF+plerixafor mobilized peripheral blood as optimal graft that should favor HSPCs engraftment after transplantation. This findings has therapeutic implications not only for b-thalassemia but also for other hematopoietic stem cell gene therapy applications. This work was funded by the F and P Cutino Foundation - Project RiMedRi CUP G73F1200015000. Disclosures No relevant conflicts of interest to declare.

scholarly journals Genome Editing Strategies to Treat Beta-Hemoglobinopathies

Blood ◽  
2017 ◽  
Vol 130 (Suppl_1) ◽  
pp. SCI-16-SCI-16
Author(s):  
Mitchell J Weiss
Keyword(s):  
Gene Therapy ◽  
Genome Editing ◽  
Conflicts Of Interest ◽  
Gene Mutations ◽  
Fetal Hemoglobin ◽  
Beta Thalassemia ◽  
Great Promise ◽  
Globin Genes ◽  
Hematopoietic Stem ◽  
Medical Therapies

Genetic forms of anemia caused by HBB gene mutations that impair beta globin production are extremely common worldwide. The resultant disorders, mainly sickle cell disease (SCD) and beta-thalassemia, cause substantial morbidity and early mortality. Treatments for these diseases include medical therapies and bone marrow transplantation (BMT), which can be curative. However, medical therapies are suboptimal and BMT is associated with serious toxicities, particularly because HLA-matched allogeneic sibling donors are not available for most patients. Thus, new therapies are urgently needed for millions of affected individuals. Gene therapy offers great promise to cure SCD and beta thalassemia and emerging genome editing technologies represent a new form of gene therapy. Approaches to cure SCD and beta-thalassemia via genome editing include: 1) Correction of HBB mutations by homology directed repair (HDR); 2) use of non-homologous end joining (NHEJ) to activate gamma globin production and raise fetal hemoglobin (HbF) levels; 3) NHEJ to disrupt alpha-globin genes (HBA1 or HBA2) and thereby alleviate globin chain imbalance in intermediately severe forms of beta thalassemia. Challenges for these approaches include selection of the most effective genome editing tools, optimizing their delivery to hematopoietic stem cells (HSCs), improving specificity and better understanding potential off target effects, particularly those that are biologically relevant. Technologies for genome editing are advancing rapidly and being tested in preclinical models for HBB-mutated disorders. Ultimately, however, the best strategies can only be identified in clinical trials. This will require close collaborations between basic/translational researchers who study genome editing, clinical hematologists and collaboration between experts in academia and the bio-pharmaceutical industry. Disclosures No relevant conflicts of interest to declare.

A Modified HIV1-Based Lentiviral Vector Can Transduce Rhesus Hematopoietic Repopulating Cells as Efficiently as An SIV Vector in An Autologous Transplantation Model.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 692-692
Author(s):  
Naoya Uchida ◽  
Phillip W Hargrove ◽  
Kareem Washington ◽  
Coen J. Lap ◽  
Matthew M. Hsieh ◽  
...  
Keyword(s):  
T Cells ◽  
Blood Cells ◽  
Conflicts Of Interest ◽  
Lentiviral Vector ◽  
Autologous Transplantation ◽  
Vector System ◽  
Transduction Efficiency ◽  
Large Animal ◽  
Hematopoietic Stem ◽  
Cd34 Cells

Abstract Abstract 692 HIV1-based vectors transduce rhesus hematopoietic stem cells poorly due to a species specific block by restriction factors, such as TRIM5αa which target HIV1 capsid proteins. The use of simian immunodeficiency virus (SIV)-based vectors can circumvent this restriction, yet use of this system precludes the ability to directly evaluate HIV1-based lentiviral vectors prior to their use in human clinical trials. To address this issue, we previously developed a chimeric HIV1 vector (χHIV vector) system wherein the HIV1-based lentiviral vector genome is packaged in the context of SIV capsid sequences. We found that this allowed χHIV vector particles to escape the intracellular defense mechanisms operative in rhesus hematopoietic cells as judged by the efficient transduction of both rhesus and human CD34+ cells. Following transplantation of rhesus animals with autologous cell transduced with the χHIV vector, high levels of marking were observed in peripheral blood cells (J Virol. 2009 Jul. in press). To evaluate whether χHIV vectors could transduce rhesus blood cells as efficiently as SIV vectors, we performed a competitive repopulation assay in two rhesus macaques for which half of the CD34+ cells were transduced with the standard SIV vector and the other half with the χHIV vector both at a MOI=50 and under identical transduction conditions. The transduction efficiency for rhesus CD34+ cells before transplantation with the χHIV vector showed lower transduction rates in vitro compared to those of the SIV vector (first rhesus: 41.9±0.83% vs. 71.2±0.46%, p<0.01, second rhesus: 65.0±0.51% vs. 77.0±0.18%, p<0.01, respectively). Following transplantation and reconstitution, however, the χHIV vector showed modestly higher gene marking levels in granulocytes (first rhesus: 12.4% vs. 6.1%, second rhesus: 36.1% vs. 27.2%) and equivalent marking levels in lymphocytes, red blood cells (RBC), and platelets, compared to the SIV vector at one month (Figure). Three to four months after transplantation in the first animal, in vivo marking levels plateaued, and the χHIV achieved 2-3 fold higher marking levels when compared to the SIV vector, in granulocytes (6.9% vs. 2.8%) and RBCs (3.3% vs. 0.9%), and equivalent marking levels in lymphocytes (7.1% vs. 5.1%) and platelets (2.8% vs. 2.5)(Figure). Using cell type specific surface marker analysis, the χHIV vector showed 2-7 fold higher marking levels in CD33+ cells (granulocytes: 5.4% vs. 2.7%), CD56+ cells (NK cells: 6.5% vs. 3.2%), CD71+ cells (reticulocyte: 4.5% vs. 0.6%), and RBC+ cells (3.6% vs. 0.9%), and equivalent marking levels in CD3+ cells (T cells: 4.4% vs. 3.3%), CD4+ cells (T cells: 3.9% vs. 4.6%), CD8+ cells (T cells: 4.2% vs. 3.9%), CD20+ cells (B cells: 7.6% vs. 4.8%), and CD41a+ cells (platelets: 3.5% vs. 2.2%) 4 months after transplantation. The second animal showed a similar pattern with higher overall levels (granulocytes: 32.8% vs. 19.1%, lymphocytes: 24.4% vs. 17.6%, RBCs 13.1% vs. 6.8%, and platelets: 14.8% vs. 16.9%) 2 months after transplantation. These data demonstrate that our χHIV vector can efficiently transduce rhesus long-term progenitors at levels comparable to SIV-based vectors. This χHIV vector system should allow preclinical testing of HIV1-based therapeutic vectors in the large animal model, especially for granulocytic or RBC diseases. Disclosures: No relevant conflicts of interest to declare.

Kinetics of Engraftment and Graft Versus Host Disease After Cotransplantation of Ex Vivo Expanded and Unexpanded Cord Blood Units In Immunodeficient Mice.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3722-3722
Author(s):  
Li Ming Ong ◽  
Xiubo Fan ◽  
Pak Yan Chu ◽  
Florence Gay ◽  
Justina Ang ◽  
...  
Keyword(s):  
Cord Blood ◽  
Conflicts Of Interest ◽  
Ex Vivo ◽  
Ex Vivo Expansion ◽  
Hematopoietic Stem ◽  
Immunodeficient Mice ◽  
Insulin Growth Factor ◽  
Nsg Mice ◽  
Nonobese Diabetic ◽  
Cd34 Cells

Abstract Abstract 3722 Ex vivo expansion of cord blood (CB) hematopoietic stem cells (HSCs) and cotransplantation of two CB units can enhance applicability of CB transplants to adult patients. This is the first study on cotransplantation of ex vivo expanded and unexpanded human CB units in immunodeficient mice, simulating conditions for ex vivo CB expansion clinical trials. CB units were cultured in serum-free medium supplemented with Stem Cell Factor, Flt-3 ligand, Thrombopoietin and Insulin Growth Factor Binding Protein-2 with mesenchymal stromal co-culture. Cotransplantation of unexpanded and expanded CB cells was achieved by tail vein injection into forty-five sublethally irradiated nonobese diabetic SCID-IL2γ−/− (NSG) mice. Submandibular bleeding was performed monthly and mice were sacrificed 4 months following transplantation to analyze for human hematopoietic engraftment. CB expansion yielded 40-fold expansion of CD34+ cells and 18-fold expansion of HSCs based on limiting dilution analysis of NSG engraftment. Mice receiving expanded grafts had 4.30% human cell repopulation, compared to 0.92% in mice receiving only unexpanded grafts at equivalent starting cell doses (p = 0.07). Ex vivo expanded grafts with lower initiating cell doses also had equivalent engraftment to unexpanded grafts with higher cell dose (8.0% vs 7.9%, p= 0.93). However, the unexpanded graft, richer in T-cells, predominated in final donor chimerism. Ex vivo expansion resulted in enhanced CB engraftment at equivalent starting cell doses, even though the unexpanded graft predominated in long-term hematopoiesis. The expanded graft with increased stem/progenitor cells enhanced initial engraftment despite eventual rejection by the unexpanded graft. Disclosures: No relevant conflicts of interest to declare.

Next Generation Humanized Mice Support Engraftment of Myelofibrosis CD34+ Cells

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 1880-1880
Author(s):  
Alexandre P.A. Theocharides ◽  
Rouven Müller ◽  
Yasuyuki Saito ◽  
Richard A. Flavell ◽  
Markus G. Manz
Keyword(s):  
Bone Marrow ◽  
Peripheral Blood ◽  
Conflicts Of Interest ◽  
Constitutive Expression ◽  
Xenograft Model ◽  
Jak2 V617f ◽  
Spleen Weight ◽  
Patient Sample ◽  
Nsg Mice ◽  
Cd34 Cells

Abstract Introduction While the key transforming genetic events occur in the developing cancerous cell, this cell is dependent on its environmental context and interaction for competitive outgrowth and subsequent tumor-development. Myelofibrosis (MF) represents a model cancer disease with stepwise development from a chronic state that depends on microenvironmental interactions to a more aggressive disease. Engraftment of primary MF patient cells in murine xenograft models is poor (Wang et al., JCI 2012) and is possibly explained by the lack of supportive microenvironmental factors. Thrombopoietin (TPO) has been implicated in the pathogenesis of MF (Schepers et al., Cell Stem Cell 2013, Dadfarnia et al., Blood 2014, Abdel-Wahab et al., Annu Rev Med 2009). Also, the interaction between human hematopoietic cells and SIRPα expressed on mouse macrophages is critical for human engraftment in xenografts (Takenaka et al., Nature Immunology 2007). We hypothesized that the constitutive expression of human TPO and human SIRPα may promote the development of the human MF clone in mouse xenografts. Methods Purified peripheral blood CD34+ cells were collected from six patients with primary MF or post-PV/ET MF and low to intermediate 2 risk disease according to the dynamic international prognostic scoring system (DIPSS). Four patients carried a JAK2-V617F mutation and two patients carried a calreticulin (CALR) mutation. CD34+ cells were intrahepatically transplanted into sublethally irradiated newborn humanSIRPα-transgenic/humanTPO-knockin Rag2-/- gamma-/- (TPO-SIRPα) mice (Rongvaux et al., Ann Rev. Immunol 2013). NSG mice were used as controls and injected with the same number of CD34+ cells. Two to three mice were injected with ≥1 million CD34+ cells from the same patient sample each. Mice were sacrificed 12-16 weeks after transplantation and human engraftment and hematopoietic cell lineage distribution was assessed by flow cytometry using human specific antibodies. Tissues were collected for immunohistochemistry, assessment of fibrosis and spleen weight. DNA was extracted from whole bone marrow and a qualitative PCR was performed to determine the presence of the JAK2-V617F or CALR-mutations. Results Three out of six samples generated a human graft of ≥20% human CD45+ cells, while the three other samples generated engraftment of 0.1-3%. The human graft was mainly composed of myeloid cells and monocytic differentiation was observed. In 2/2 experiments analysed, a JAK2-V617F and a CALR type 2 mutation were detected in the bone marrow of engrafted mice transplanted with the respective patient sample. Development of fibrosis was not observed three months post-transplantation, presumably due to the short observation time. Spleen weight was significantly increased in mice engrafted with human MF and was the consequence of increased murine extramedullary hematopoiesis. We then aimed to identify factors that could predict human MF engraftment in TPO-SIRPα mice. While neither the DIPSS, nor the presence of myeloid precursors in the peripheral blood (blasts excluded) were predictive of human MF engraftment, the presence of blasts in the peripheral blood significantly correlated with engraftment potential. Importantly, none of the patients developed acute leukemia during follow-up. Finally, preliminary evidence suggests that TPO-SIRPα mice are more supportive of human MF engraftment than NSG mice. Conclusions This is the first xenograft model that supports robust engraftment of human peripheral blood MF cells and further supports a role for TPO in the pathogenesis of MF. In contrast to previous models TPO-SIRPα mice strongly promote myeloid rather than lymphoid engraftment. The tight correlation between the presence of peripheral blood blasts and the human MF engraftment potential suggests that human MF stem cells reside in the blast population. In summary, the xenograft model presented here constitutes a powerful tool to assess heterogeneity regarding MF biology, microenvironmental dependence of the MF clone and likely also therapeutic response of MF in vivo. Disclosures No relevant conflicts of interest to declare.

The Tetraspanin CD9 Regulates Engraftment and Mobilization of Human CD34+ Hematopoietic Stem/Progenitor Cells and Modulates VLA-4 Activity

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1169-1169
Author(s):  
Kam Tong Leung ◽  
Karen Li ◽  
Yorky Tsin Sik Wong ◽  
Kathy Yuen Yee Chan ◽  
Xiao-Bing Zhang ◽  
...  
Keyword(s):  
Stem Cell ◽  
Progenitor Cells ◽  
Peripheral Blood ◽  
Scid Mouse ◽  
Conflicts Of Interest ◽  
Chimeric Mice ◽  
Hematopoietic Stem ◽  
Cell Engraftment ◽  
Cd34 Cells

Abstract Migration, homing and engraftment of hematopoietic stem/progenitor cells depend critically on the SDF-1/CXCR4 axis. We previously identified the tetraspanin CD9 as a downstream signal of this axis, and it regulates short-term homing of cord blood (CB) CD34+ cells (Leung et al, Blood, 2011). However, its roles in stem cell engraftment, mobilization and the underlying mechanisms have not been described. Here, we provided evidence that CD9 blockade profoundly reduced long-term bone marrow (BM; 70.9% inhibition; P = .0089) and splenic engraftment (87.8% inhibition; P = .0179) of CB CD34+ cells (n = 6) in the NOD/SCID mouse xenotransplantation model, without biasing specific lineage commitment. Interestingly, significant increase in the CD34+CD9+ subsets were observed in the BM (9.6-fold; P < .0001) and spleens (9.8-fold; P = .0014) of engrafted animals (n = 3-4), indicating that CD9 expression on CD34+ cells is up-regulated during engraftment in the SDF-1-rich hematopoietic niches. Analysis of paired BM and peripheral blood (PB) samples from healthy donors revealed higher CD9 expressions in BM-resident CD34+ cells (46.0% CD9+ cells in BM vs 26.5% in PB; n = 13, P = .0035). Consistently, CD34+ cells in granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood (MPB) expressed lower levels of CD9 (32.3% CD9+ cells; n = 25), when compared with those in BM (47.7% CD9+ cells; n = 16, P = .0030). In vitro exposure of MPB CD34+ cells to SDF-1 significantly enhanced CD9 expression (1.5-fold increase; n = 4, P = .0060). Treatment of NOD/SCID chimeric mice with G-CSF decreased the CD34+CD9+ subsets in the BM from 79.2% to 62.4% (n = 8, P = .0179). These data indicate that CD9 expression is down-regulated during egress or mobilization of CD34+ cells. To investigate the possible mechanisms, we performed a VCAM-1 (counter receptor of the VLA-4 integrin) binding assay on BM CD34+ cells. Our results demonstrated that CD34+CD9+ cells preferentially bound to soluble VCAM-1 (17.2%-51.4% VCAM-1-bound cells in CD9+ cells vs 12.8%-25.9% in CD9- cells; n = 10, P ≤ .0003), suggesting that CD9+ cells possess higher VLA-4 activity. Concomitant with decreased CD9 expression, MPB CD34+ cells exhibited lower VCAM-1 binding ability (2.8%-4.0% VCAM-1-bound cells; n = 3), when compared to BM CD34+ cells (15.5%-37.7%; n = 10, P < .0130). In vivo treatment of NOD/SCID chimeric mice with G-CSF reduced VCAM-1 binding of CD34+ cells in the BM by 49.0% (n = 5, P = .0010). Importantly, overexpression of CD9 in CB CD34+ cells promoted VCAM-1 binding by 39.5% (n = 3, P = .0391), thus providing evidence that CD9 regulates VLA-4 activity. Preliminary results also indicated that enforcing CD9 expression in CB CD34+ cells could enhance their homing and engraftment in the NOD/SCID mouse model. Our findings collectively established that CD9 expression and associated integrin VLA-4 activity are dynamically regulated in the BM microenvironment, which may represent important events in governing stem cell engraftment and mobilization. Strategies to modify CD9 expression could be developed to enhance engraftment or mobilization of CD34+ cells. Disclosures No relevant conflicts of interest to declare.

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