Identification and Validation of Novel Hematopoietic Stem Cell Regulatory microRNAs

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3872-3872
Author(s):  
Elias Simon Peter Eckert ◽  
Peer Wünsche ◽  
Manfred Schmidt ◽  
Claudia Ball ◽  
Friederike Herbst ◽  
...  
Keyword(s):  
Gene Therapy ◽  
High Throughput Sequencing ◽  
Conflicts Of Interest ◽  
Selection Process ◽  
Integration Site ◽  
Selection Strategy ◽  
Hematopoietic Stem ◽  
Mirna Genes ◽  
Clinical Gene Therapy

Abstract Within this study we have developed a novel approach to identify hematopoietic regulatory genes by re-analyzing genome-wide viral integration site (IS) data from a clinical gene therapy trial of 10 Wiskott-Aldrich syndrome patients. We observed a statistically enriched contribution of individual cell clones marked by IS to benign human long-term hematopoiesis within a dataset comprising 130,699 unique IS in the proximity of 12,437 genes. Furthermore, when we assessed the genomic distribution of the IS, we found that clusters of IS (CIS) are significantly over-represented at certain coding and non-coding genetic loci, indicating a viral marking of actively transcribed genes or a proliferation advantage of specific clones due to viral induced deregulation of adjacent genes. Notably, 42 % of the 50 most enriched regions encode for human HSC regulators such as MECOM, LMO2 and HMGA2. Based on a stepwise and stringent selection process evaluating IS number, location and CIS size, we chose the top 12 ranked miRNA genes for further analysis. Of those, three miRNAs (miR-132, miR-142, miR-146a) have described roles in hematopoiesis, strongly validating our selection strategy. In order to functionally investigate the influence of selected candidate genes on hematopoiesis we developed a lentiviral (LV) based pooled overexpression (OE) approach using uniquely barcoded (BC) vectors encoding for the top 8 candidate miRNA HSC regulators in lin- sca1+ ckit+ (LSK) cells. The LV based library consists of two vectors per gene including corresponding GFP control vectors, and harbor a unique BC cassette serving as a molecular tag to allow its unbiased amplification and high-throughput sequencing of up to 96 indexed samples simultaneously. To assess the influence of the selected miRNA candidates on hematopoietic differentiation in vitro, we performed serial CFU assays using BC library transduced LSK-SLAM cells as a starting population. Low infection rates were used to ensure one vector copy per cell. We detected a 1.58±0.03 [SEM] fold increase (p=0.003, n=5) in myeloid colony forming potential of miRNA library OE cells compared to GFP control cells without a shift in colony phenotypes. After three rounds of serial replating, colonies expressing 2/8 candidates were significantly overrepresented (1.6±0.23 to 2.0±0.20 fold; p=0.049 and p=0.005; n =5) while BC vectors encoding for two other candidate miRNAs were significantly reduced (0.4±0.11 to 0.5±0.14 fold, p=0.006 and p=0.027) compared to GFP control (fc=1.0±0.12). To address the influence of candidate miRNA OE on multi-lineage engraftment and self-renewal in vivo, we serially transplanted miRNA or GFP control library transduced LSK cells in a cohort of 18 recipient mice. We revealed efficient candidate BC representation in all mice with a median read count of 7.1E4 (min=2451, max=8.4E5) 20 weeks post-transplant. In line with our results in vitro, we observed a 1.23±0.23 (p=0.044) fold enrichment of the same two miRNA candidates and a depletion of the two other miRNA genes (0.63±0.09 to 0.68±0.13fold; p=0.002 and p=0.033) in PB samples already eight weeks after transplantation. Interestingly, BC sequencing of lineage sorted fractions suggests that one of the overrepresented candidates has a strong influence on T-cell differentiation (fc=1.5±0.2, p=0.029, 20 weeks post TP) whereas the other candidate impacts on myelopoiesis (fc=1.6±0.35, p=0.114). In summary, our systematic stepwise approach combining the comprehensive analysis of the complete integration site repertoire in a clinical gene therapy study with subsequent functional validation using a pooled lentiviral overexpression approach is a useful strategy to identify and characterize novel HSC regulators. Disclosures No relevant conflicts of interest to declare.

scholarly journals Long-term lymphoid progenitors independently sustain naïve T and NK cell production in humans

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Natalia Izotova ◽  
Christine Rivat ◽  
Cristina Baricordi ◽  
Elena Blanco ◽  
Danilo Pellin ◽  
...  
Keyword(s):  
Stem Cells ◽  
Gene Therapy ◽  
Nk Cell ◽  
Integration Site ◽  
Hematopoietic Stem ◽  
Cell Production ◽  
Lymphoid Progenitors ◽  
Clinical Gene Therapy ◽  
Cancer Immunotherapies

AbstractOur mathematical model of integration site data in clinical gene therapy supported the existence of long-term lymphoid progenitors capable of surviving independently from hematopoietic stem cells. To date, no experimental setting has been available to validate this prediction. We here report evidence of a population of lymphoid progenitors capable of independently maintaining T and NK cell production for 15 years in humans. The gene therapy patients of this study lack vector-positive myeloid/B cells indicating absence of engineered stem cells but retain gene marking in both T and NK. Decades after treatment, we can still detect and analyse transduced naïve T cells whose production is likely maintained by a population of long-term lymphoid progenitors. By tracking insertional clonal markers overtime, we suggest that these progenitors can support both T and NK cell production. Identification of these long-term lymphoid progenitors could be utilised for the development of next generation gene- and cancer-immunotherapies.

scholarly journals From Bone Marrow to Mobilized Peripheral Blood Stem Cells: The Circuitous Path to Clinical Gene Therapy for Fanconi Anemia

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 2208-2208
Author(s):  
Pamela S Becker ◽  
Jennifer Adair ◽  
Grace Choi ◽  
Anne Lee ◽  
Ann Woolfrey ◽  
...  
Keyword(s):  
Stem Cells ◽  
Gene Therapy ◽  
Bone Marrow ◽  
Fanconi Anemia ◽  
Research Funding ◽  
Hematopoietic Stem ◽  
Post Infusion ◽  
Clinical Gene Therapy

Abstract For decades, it has remained challenging to achieve long-term engraftment and correction of blood counts using gene-modified hematopoietic stem cells for Fanconi anemia. Toward this goal, our group conducted preclinical studies using a safety modified lentiviral vector encoding full-length cDNA for FANCA in normal and affected patient hematopoietic progenitor cells, and in a mutant mouse model that supported the IND for a gene therapy clinical trial for Fanconi anemia, complementation group A (NCT01331018). These studies led us to incorporate methods such as addition of N-acetylcysteine and hypoxic incubation during transduction. Because of the low stem cell numbers of Fanconi patients and initial difficulty with using plerixafor off-label for mobilization, we began our study with bone marrow as the source of stem cells. Due to concerns regarding secondary cancers, no conditioning was administered prior to infusion of gene-modified cells. The US Food and Drug Administration approved adult patients initially, but later permitted pediatric patient enrollment with a minimum age of 4 years. The primary objective of our phase I trial was safety. Secondary objectives included in vitro correction of mitomycin C (MMC) sensitivity, procurement of sufficient cell numbers, and ultimately, long-term correction of blood counts in recipients. Eligibility included absolute neutrophil count ≥0.5, hemoglobin ≥8, platelet count ≥20,000, lack of matched family donor, adequate organ function, and not meeting criteria for diagnosis of MDS. Our three enrolled patients were ages 22, 10, and 5 years. All demonstrated defects in the FANCA gene, with two patients sequenced and one patient diagnosed by complementation. Due to in-process learning and the later addition of plerixafor mobilization to the protocol, three different laboratory procedures were used to prepare the gene-modified product for each patient. Cell products were CD34+ selected bone marrow, bone marrow mononuclear cells depleted of red cells by hetastarch, and G-CSF and plerixafor mobilized cells depleted of red blood cells and cells bearing lineage markers, respectively. Transduction efficiencies were 17.7, 42.7 and 26.3% of colony forming cells (CFC) in 0 nM MMC, and 80, 100, and 100% of CFC in 10 nM MMC. Growth of hematopoietic colonies in MMC indicated functional correction of the FANCA defect. The 1st patient received 6.1×10e4, the 2nd 2.9×10e5, and the 3rd 4.3×10e6 CD34+ cells/kg. Serious adverse events included cytopenias in all patients, and hospital admission for fever due to viral upper respiratory infection in one patient. The patients remain alive at 46, 38, and 12 months after receipt of gene-modified cells. Due to worsening cytopenias, the third patient underwent hematopoietic cell transplant from an unrelated donor 10 months after infusion of gene-modified cells. To date, he has done well with transplant, and no indication that prior gene therapy impacted the outcome. The blood counts for the first 2 patients who have not undergone allogeneic transplant remain stable at 1,111 and 1,077 days post infusion compared to the first blood counts when they arrived at our center. For the 1st patient, vector was detectable in white blood cells (WBC) up to 21 days, in the 2nd up to 582 days, and the 3rd up to 81 days post infusion. Thus, in these patients, despite dramatic improvement in cell dose during the study, there was lack of persistence in detection of gene-modified WBCs beyond 1.5 years. A number of factors may have contributed, including lack of conditioning, in vitro cell manipulation including cytokine exposure, inability to transduce primitive hematopoietic stem cells, and paucity of long-term repopulating cells at the ages of the patients, suggesting earlier collection may be beneficial. This study is now closed to enrollment. Valuable information gained as a result of this study will contribute to future clinical gene therapy trials. Current work focuses on how to evaluate stem cell fitness prior to attempting gene therapy, minimizing manipulation required for gene correction and/or in vivo genetic correction and non-chemotherapy-based conditioning to facilitate engraftment. We would like to personally thank each patient and their families for participating in this study, as we could not have learned these lessons without their support. Disclosures Becker: GlycoMimetics: Research Funding; Abbvie: Research Funding; Amgen: Research Funding; BMS: Research Funding; CVS Caremark: Consultancy; Trovagene: Research Funding; Rocket Pharmaceuticals: Research Funding; Novartis: Research Funding; Pfizer: Consultancy; JW Pharmaceuticals: Research Funding. Adair:Miltenyi Biotec: Honoraria; RX Partners: Honoraria; Rocket Pharmaceuticals: Patents & Royalties: PCT/US2017/037967 and PCT/US2018/029983. Kiem:Rocket Pharmaceuticals: Consultancy; Homology Medicine: Consultancy; Magenta: Consultancy.

HSC Transplantation for Hemoglobinopathies: Allogeneic or Autologous Gene-Modified HSC?

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. SCI-46-SCI-46
Author(s):  
Marina Cavazzana-Calvo ◽  
Emmanuel Payen ◽  
Olivier Negre ◽  
Salima Hacein-Bey-Abina ◽  
Philippe Leboulch
Keyword(s):  
Gene Therapy ◽  
Conflicts Of Interest ◽  
Integration Site ◽  
Globin Gene ◽  
Iron Chelation ◽  
Single Amino Acid ◽  
Full Time ◽  
Hematopoietic Stem ◽  
Curative Therapy ◽  
Hsc Transplantation

Abstract Abstract SCI-46 The hematopoietic stem cell (HSC) transplantation pioneered by the Pesaro group is now applied wildly worldwide. The European Group for Blood and Marrow Transplantation (EBMT) has established the hemoglobinopathy registry, which now contains detailed epidemiological data on over 3000 patients. Today, allogeneic transplantation remains the only definitive curative therapy for thalassemia and other hemoglobinopathies. The development of iron chelation did not change this position. However, this has not settled the debate on how this curative but potentially lethal treatment stands vis-à-vis a medical noncurative therapy for adult and advanced disease patients. Nevertheless, despite the substantial improvements, a number of problems remain unsolved, such as the absence of an HLA genoidentical donor for all the diseased patients especially when they come from Outreach countries and the long-term morbidity due to HSCT (i.e., infectious complications, acute and chronic graft-versus-host disease, sterility). In this context and despite the unsolved debate, the development of gene therapy is highly justified. Sadelain and Leboulch pioneered the use of lentiviruses in human globin gene therapy, showing that anemia in mice affected with diseases mimicking the human pathological conditions can be abbreviated significantly by using lentiviruses containing a normal human β-globin gene. These pre-clinical studies set the basis for the current human clinical trial in Paris and for the upcoming trials. In our gene therapy trial, the human β-globin gene sequence has been modified by mutating a single amino acid at position 87 of the β-globin sequence. The major reason for using the b87 globin gene in lentiglobin in patients with β-thalassemia is that Hbb87 expression can easily be distinguished from that of normal Hb (HbA). In this trial, the patients received a full dose of Busulfex in the aim to obtain a myeloablation allowing the successful intake of gene modified autologous HSC. Two patients with thalassemia have been treated to date. One out of the two patients obtained a clinical benefit and is stably transfusion independent more than 3 years after the last transfusion. He currently has approximately 9 to 10 g percent of Hb in his blood, approximately one third being Hbb87, one third human HbF, and one third HbE. The patient is healthy up to now, with a full-time job. Integration site profile data will be discussed in detail during the meeting. Additional patients affected with thalassemia are currently being recruited in the Paris trial. Disclosures: No relevant conflicts of interest to declare.

The Immunogenicity of Platelet-Derived FVIII in Hemophilia a Mice with or without Pre-Existing Anti-FVIII Immunity

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2809-2809
Author(s):  
Yingyu Chen ◽  
Jocelyn Schroeder ◽  
Juan Chen ◽  
Xiaofeng Luo ◽  
Christina Baumgartner ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Immune Response ◽  
Hemophilia A ◽  
Conflicts Of Interest ◽  
Ex Vivo ◽  
High Titer ◽  
Hematopoietic Stem ◽  
Inhibitory Antibodies ◽  
Platelet Infusion

Abstract Recent studies from our group and others have demonstrated that FVIII ectopically targeted to platelets under control of the platelet-specific αIIb promoter (2bF8) can efficiently restore hemostasis in hemophilia A mice even in the presence of high-titer inhibitory antibodies directed against FVIII (inhibitors). Our studies have demonstrated that platelet-targeted FVIII gene therapy can not only correct the hemophilic phenotype, but also induce FVIII-specific immune tolerance. In the platelet gene therapy model, hematopoietic stem cells (HSCs) are ex vivo transduced with lentivirus carrying 2bF8 and transplanted into the recipient. Sufficient preconditioning has to be employed to create space for therapeutic engraftment of the transduced HSCs. It is not clear whether preconditioning affects the potential for an immune response in the context of platelet-derived FVIII. Furthermore, if current efforts to generate platelets in vitro succeed, genetically manipulated platelets containing FVIII may be used therapeutically, as potential transfusion alternative, in hemophilia A patients even with inhibitors. One important question that has not been explored, however, is the immunogenicity of platelet-derived FVIII. To investigate whether platelet-derived FVIII can act as an immunogen in hemophilia A mice, we infused transgenic mouse platelets with a level of platelet-FVIII of 6 mU/108 platelets into naïve FVIIInull mice without any preconditioning weekly for 8 weeks. These platelets were transfused to a level between 20 to 57% of total platelets upon infusion, and all animals survived the tail-clip survival test 13-hours after platelet infusion. The level of platelet-FVIII in the infused animals was 0.11 ± 0.01 mU/108 platelets (n = 6) even one week after infusion. Neither inhibitory nor non-inhibitory anti-FVIII antibodies were detected in the infused mice during the study course (n = 9). All animals developed inhibitors following further challenge with recombinant human FVIII (rhF8) at a dose of 50 U/kg by intravenous injection weekly for 4 weeks, indicating that infusion of platelets containing FVIII does not trigger an immune response in hemophilia A mice. We then explored whether platelets containing FVIII can act as an immunogen in FVIIInull mice with pre-existing anti-FVIII immunity. FVIIInull mice were immunized with rhF8 to induce anti-FVIII antibodies. Four week after the last immunization, 2bF8 transgenic platelets were transfused into rhF8-primed FVIIInull mice (n = 4) weekly for 4 weeks and anti-FVIII antibody titers were monitored. There was not significant augmentation of FVIII-specific antibodies as determined by Bethesda assay for inhibitory antibodies and ELISA assay for total anti-FVIII IgG, indicating that infusion of platelets containing FVIII does not stimulate an anti-FVIII memory response in the inhibitor model. To investigate whether preconditioning affects the anti-FVIII immune response, animals were pre-conditioned with a sub-lethal 660 cGy total body irradiation (TBI) followed by 2bF8 transgenic platelet infusion weekly for 8 weeks. No anti-FVIII antibodies were detected in recipients (n = 6) after 2bF8 transgenic platelet infusion. Following further challenge with rhF8, the inhibitor titer in this group was significantly lower (75 ± 42 BU/ml) than in the naïve FVIIInull mice without preconditioning when the same infusion protocol was employed (270 ± 76 BU/ml), indicating that 660 cGy TBI plus 2bF8 transgenic platelet infusion may suppress anti-FVIII immune response. In conclusion, our data demonstrate that infusion of platelets containing FVIII triggers neither primary nor memory anti-FVIII immune response in hemophilia A mice. Disclosures No relevant conflicts of interest to declare.

Cellular barcoding tool for clonal analysis in the hematopoietic system

Blood ◽  
2010 ◽  
Vol 115 (13) ◽  
pp. 2610-2618 ◽  
Author(s):  
Alice Gerrits ◽  
Brad Dykstra ◽  
Olga J. Kalmykowa ◽  
Karin Klauke ◽  
Evgenia Verovskaya ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Integration Site ◽  
Retroviral Vectors ◽  
Clonal Analysis ◽  
Great Promise ◽  
Hematopoietic Stem ◽  
Site Analysis ◽  
Integration Site Analysis ◽  
Cellular Barcoding

Abstract Clonal analysis is important for many areas of hematopoietic stem cell research, including in vitro cell expansion, gene therapy, and cancer progression and treatment. A common approach to measure clonality of retrovirally transduced cells is to perform integration site analysis using Southern blotting or polymerase chain reaction–based methods. Although these methods are useful in principle, they generally provide a low-resolution, biased, and incomplete assessment of clonality. To overcome those limitations, we labeled retroviral vectors with random sequence tags or “barcodes.” On integration, each vector introduces a unique, identifiable, and heritable mark into the host cell genome, allowing the clonal progeny of each cell to be tracked over time. By coupling the barcoding method to a sequencing-based detection system, we could identify major and minor clones in 2 distinct cell culture systems in vitro and in a long-term transplantation setting. In addition, we demonstrate how clonal analysis can be complemented with transgene expression and integration site analysis. This cellular barcoding tool permits a simple, sensitive assessment of clonality and holds great promise for future gene therapy protocols in humans, and any other applications when clonal tracking is important.

scholarly journals Preclinical Development of Autologous Hematopoietic Stem Cell-Based Gene Therapy for Immune Deficiencies: A Journey from Mouse Cage to Bed Side

Pharmaceutics ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 549
Author(s):  
Laura Garcia-Perez ◽  
Anita Ordas ◽  
Kirsten Canté-Barrett ◽  
Pauline Meij ◽  
Karin Pike-Overzet ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Severe Combined Immunodeficiency ◽  
Good Manufacturing Practice ◽  
Proof Of Concept ◽  
Preclinical Development ◽  
Hematopoietic Stem ◽  
Immune Deficiencies ◽  
Suitable Vector

Recent clinical trials using patient’s own corrected hematopoietic stem cells (HSCs), such as for primary immunodeficiencies (Adenosine deaminase (ADA) deficiency, X-linked Severe Combined Immunodeficiency (SCID), X-linked chronic granulomatous disease (CGD), Wiskott–Aldrich Syndrome (WAS)), have yielded promising results in the clinic; endorsing gene therapy to become standard therapy for a number of diseases. However, the journey to achieve such a successful therapy is not easy, and several challenges have to be overcome. In this review, we will address several different challenges in the development of gene therapy for immune deficiencies using our own experience with Recombinase-activating gene 1 (RAG1) SCID as an example. We will discuss product development (targeting of the therapeutic cells and choice of a suitable vector and delivery method), the proof-of-concept (in vitro and in vivo efficacy, toxicology, and safety), and the final release steps to the clinic (scaling up, good manufacturing practice (GMP) procedures/protocols and regulatory hurdles).

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.

ADA-deficient SCID is associated with a specific microenvironment and bone phenotype characterized by RANKL/OPG imbalance and osteoblast insufficiency

Blood ◽  
2009 ◽  
Vol 114 (15) ◽  
pp. 3216-3226 ◽  
Author(s):  
Aisha V. Sauer ◽  
Emanuela Mrak ◽  
Raisa Jofra Hernandez ◽  
Elena Zacchi ◽  
Francesco Cavani ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Bone Marrow ◽  
Severe Combined Immunodeficiency ◽  
Intrinsic Defect ◽  
Combined Immunodeficiency ◽  
Hematopoietic Stem ◽  
Enzyme Replacement ◽  
Bone Phenotype

Abstract Adenosine deaminase (ADA) deficiency is a disorder of the purine metabolism leading to combined immunodeficiency and systemic alterations, including skeletal abnormalities. We report that ADA deficiency in mice causes a specific bone phenotype characterized by alterations of structural properties and impaired mechanical competence. These alterations are the combined result of an imbalanced receptor activator of nuclear factor-κB ligand (RANKL)/osteoprotegerin axis, causing decreased osteoclastogenesis and an intrinsic defect of osteoblast function with subsequent low bone formation. In vitro, osteoblasts lacking ADA displayed an altered transcriptional profile and growth reduction. Furthermore, the bone marrow microenvironment of ADA-deficient mice showed a reduced capacity to support in vitro and in vivo hematopoiesis. Treatment of ADA-deficient neonatal mice with enzyme replacement therapy, bone marrow transplantation, or gene therapy resulted in full recovery of the altered bone parameters. Remarkably, untreated ADA–severe combined immunodeficiency patients showed a similar imbalance in RANKL/osteoprotegerin levels alongside severe growth retardation. Gene therapy with ADA-transduced hematopoietic stem cells increased serum RANKL levels and children's growth. Our results indicate that the ADA metabolism represents a crucial modulatory factor of bone cell activities and remodeling. The trials were registered at www.clinicaltrials.gov as #NCT00598481 and #NCT00599781.

Therapeutic Effect of HOXB4-Expanded Stem Cells in Mice with Beta Thalassemia Given a Non-Myeloablative Conditioning Regimen.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 341-341
Author(s):  
Silvia Bakovic ◽  
Patricia M. Rosten ◽  
Connie J. Eaves ◽  
R. Keith Humphries
Keyword(s):  
Stem Cells ◽  
Gene Therapy ◽  
Ex Vivo ◽  
Globin Gene ◽  
Conditioning Regimen ◽  
Beta Thalassemia ◽  
Mouse Bone Marrow ◽  
Myeloablative Conditioning ◽  
Hematopoietic Stem

Abstract The ultimate promise of gene therapy for patients with hemoglobinopathies depends on the development of safe strategies for achieving 2 goals. One is to obtain efficient and permanent correction of the gene defect in autologous hematopoietic stem cells (HSCs). The second is to develop methods for the pre-transplant amplification of transduced HSCs to high levels to ensure that they will outcompete the large residual endogenous HSC population remaining in non-myeloablated hosts (e.g. previous experiments have shown that a minimum of ~5 × 106 normal adult mouse bone marrow (BM) cells (~500 HSC) is required to achieve a level of chimerism of 20% in mice given 200 cGy). The ability of HOXB4 to promote HSC self-renewal divisions in short term culture prior to their use as transplants offers an attractive approach to achieve this latter goal. As a first test we transduced day-4 5FU BM cells from normal mice with a MSCV-HOXB4-IRES-GFP or control MSCV-IRES-GFP virus and then transplanted the cells either before or after 7 days maintenance in vitro into normal recipients given 250 cGy. Mice transplanted with an estimated 50 HSCs immediately after transduction with either virus reached equivalent low levels of chimerism (~10%) showing that HOXB4 does not impart an in vivo selective growth advantage under sublethal conditions. After ex vivo culture, the GFP transduced cells yielded an even lower level of chimerism (~5%), in contrast recipients of cultured HOXB4-transduced cells attained much higher stable levels of lympho-myeloid chimerism (~50%), indicative of a marked expansion of the HSCs pre-transplant and their retention of robust competitive repopulating potential. We then applied this approach to a gene therapy model of severe β-thalassemia in mice bearing a homozygous deletion of the β-major globin gene (β-MDD). To model a transplant of genetically corrected cells, BM cells were harvested from day-4 5FU pre-treated congenic wild-type donors and transduced with the HOXB4 virus. Cells were then cultured for 10 days and the progeny of 200K starting cells transplanted into 3 β-MDD and 4 normal recipients given 200 cGy. Transplantation of 500K freshly harvested day-4 5FU BM cells into 4 similarly conditioned control mice failed to produce significant chimerism (1–3% at 5 months). In contrast, all 4 control recipients of ex vivo expanded HOXB4-transduced cells exhibited significant stable chimerism (21±6% at 5 months). Similar levels of chimerism were also achieved in all 3 β-MDD recipients (18–76%), one of which was sustained at 34% at 5 months (52% in the RBCs). This was associated with substantial improvement in the Hct (36% vs 23% in untreated β-MDD), Hb (10.5 vs 5 g/dl) and RBC morphology. Southern blot analyses performed on 53 individual in vitro-expanded myeloid colonies generated from FACS-selected GFP+ marrow cells from this mouse 2 months post-transplant showed 19 distinct integration patterns indicating reconstitution from polyclonal expanded HSCs. This conclusion was further confirmed by proviral integration site analyses, which identified 13 separate integration sites from 9 colonies that had unique proviral patterns. These data demonstrate the curative potential of ex vivo expanded HSCs in a preclinical model of β-thalassemia treated with non-myeloablative conditioning. They also underscore the potential of HOXB4 as a potent tool to achieve the HSC expansions required.

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