ALBERT

Description: The present study demonstrates that CD4+CD25+ T cells, expanded in peripheral blood of HIV-infected patients receiving highly active antiretroviral therapy (HAART), exhibit phenotypic, molecular, and functional characteristics of regulatory T cells. The majority of peripheral CD4+CD25+ T cells from HIV-infected patients expressed a memory phenotype. They were found to constitutively express transcription factor forkhead box P3 (Foxp3) messengers. CD4+CD25+ T cells weakly proliferated to immobilized anti-CD3 monoclonal antibody (mAb) and addition of soluble anti-CD28 mAb significantly increased proliferation. In contrast to CD4+CD25– T cells, CD4+CD25+ T cells from HIV-infected patients did not proliferate in response to recall antigens and to p24 protein. The proliferative capacity of CD4 T cells to tuberculin, cytomegalovirus (CMV), and p24 significantly increased following depletion of CD4+CD25+ T cells. Furthermore, addition of increasing numbers of CD4+CD25+ T cells resulted in a dose-dependent inhibition of CD4+CD25– T-cell proliferation to tuberculin and p24. CD4+CD25+ T cells responded specifically to p24 antigen stimulation by expressing transforming growth factor β (TGF-β) and interleukin 10 (IL-10), thus indicating the presence of p24-specific CD4+ T cells among the CD4+CD25+ T-cell subset. Suppressive activity was not dependent on the secretion of TGF-β or IL-10. Taken together, our results suggest that persistence of HIV antigens might trigger the expansion of CD4+CD25+ regulatory T cells, which might induce a tolerance to HIV in vivo.

Description: In gene therapy with human hematopoietic stem and progenitor cells (HSPCs), each gene-corrected cell and its progeny are marked in a unique way by the integrating vector. This feature enables lineages to be tracked by sampling blood cells and using DNA sequencing to identify the vector integration sites. Here, we studied 5 cell lineages (granulocytes, monocytes, T cells, B cells, and natural killer cells) in patients having undergone HSPC gene therapy for Wiskott-Aldrich syndrome or β hemoglobinopathies. We found that the estimated minimum number of active, repopulating HSPCs (which ranged from 2000 to 50 000) was correlated with the number of HSPCs per kilogram infused. We sought to quantify the lineage output and dynamics of gene-modified clones; this is usually challenging because of sparse sampling of the various cell types during the analytical procedure, contamination during cell isolation, and different levels of vector marking in the various lineages. We therefore measured the residual contamination and corrected our statistical models accordingly to provide a rigorous analysis of the HSPC lineage output. A cluster analysis of the HSPC lineage output highlighted the existence of several stable, distinct differentiation programs, including myeloid-dominant, lymphoid-dominant, and balanced cell subsets. Our study evidenced the heterogeneous nature of the cell lineage output from HSPCs and provided methods for analyzing these complex data.

Description: We report preliminary results in 3 children with cerebral X-linked adrenoleukodystrophy (ALD) who received in September 2006, January 2007 and June 2008 lentiviral vector transduced autologous hematopoietic stem cell (HSC). We have previously demonstrated that cerebral demyelination associated with cerebral ALD can be stopped or reversed within 12–18 months by allogeneic HSC transplantation. The long term beneficial effects of HCT transplantation in ALD are due to the progressive turn-over of brain macrophages (microglia) derived from bone-marrow cells. For the current HSC gene therapy procedure, we used mobilized peripheral blood CD34+ cells that were transduced ex vivo for 18 hours with a non-replicative HIV1-derived lentiviral vector (CG1711 hALD) at MOI25 and expressing the ALD cDNA under the control of the MND (myeloproliferative sarcoma virus enhancer, negative control region deleted, dl587rev primer binding site substituted) promoter, and in the presence of 4 human recombinant cytokines (Il- 3, Stem Cell Factor [SCF], Flt3-ligand and Megakaryocyte Growth and Differentiation Factor [MGDF]) and CH-296 retronectine. Transduced cells were frozen to perform the required (RCL) safety tests. After thawing and prior to reinjection, 50%, 30% and 40% of transduced CD34+ cells expressed the ALD protein with a mean of 0.7, 0.6 and 0.65 copies of integrated provirus per cell. Transduced CD34+ cells were infused to ALD patients after a conditioning regimen including full doses of cyclophosphamide and busulfan. Hematopoietic recovery occured at day 13–15 post-transplant and the procedure was uneventful. In patient P1 and P2, the percentage of lymphocytes and monocytes expressing the ALD protein declined from day 60 to 6 months after gene therapy (GT) and remained stable up to 16 months post-GT. In P1, 9 to 13% of CD14+, CD3+, CD19+ and CD15+ cells expressed ALD protein 16 months post-transplant. In P2 and at the same time-point after transplant, 10 to 18% of CD14+, CD3+, CD19+ and CD15+ cells expressed ALD protein. ALD protein was expressed in 18–20% of bone marrow CD34+ cells from patients P1 and P2, 12 months post-transplant. In patient P3, 20 to 23% of CD3+, CD14+ and CD15+ cells expressed ALD protein 2 months after transplant. Tests assessing vector-derived RCL and vector mobilization were negative up to the last followups in the 3 patients. Integration of the vector was polyclonal and studies of integration sites arein progress. At 16 months post-transplant, HSC gene therapy resulted in neurological effects comparable with allogeneic HSC transplantation in patient P1 and P2. These results support that: ex-vivo HSC gene therapy using HIV1-derived lentiviral vector is not associated with the emergence of RCL and vector mobilization; a high percentage of hematopoietic progenitors were transduced expressing ALD protein in long term; no early evidence of selective advantage of the transduced ALD cells nor clonal expansion were observed. (This clinical trial is sponsored by Institut National de la Santé et de la Recherche Médicale and was conducted in part under a R&D collaboration with Cell Genesys, Inc., South San Francisco, CA)

Description: Background. Wiskott Aldrich Syndrome (WAS) is a rare primary immunodeficiency associated with thrombocytopenia, eczema, severe infectious and autoimmune complications, and lymphomas. Mismatched allogeneic hematopoietic stem cell transplantation (HSCT) is an alternative for patient lacking an HLA-matched donor but is associated with an increased frequency of complications. Moreover low lymphoid and myeloid chimerism is related to a higher rate of autoimmunity and thrombocytopenia. Recent gene therapy (GT) trials showed that gene-corrected autologous CD34+ cells infusion could be an appropriate therapeutic approach for these patients. It has been recently shown that B cell homeostasis is altered in WAS. As the B cell reconstitution participates to the restoration of immunological competence, a comprehensive study of this compartment after GT and the comparison with mismatched allogeneic HSCT is crucial. Objective. To perform a longitudinal study of B cell reconstitution in WAS patients after lentiviral vector-mediated GT, compared to mismatched allogeneic HSCT. Methods. Five patients (age 0.8-15.5 years) underwent GT at our center since 2011(follow-up 1.5-4.2 years) after near-myeloablative and immunosuppressive conditioning regimen with (n=3) or without (n=2) anti-CD20 administration. Patient 2 (P2) died 7 months after GT from a pre-existing infectious complication. Eleven patients undergoing mismatched allogeneic HSCT (age 0.6-10.9 years) at the same center were studied (follow-up 5.1-14.7 years). Longitudinal B cell assessment included B cell count before and after treatment, and the following subsets: switched memory (SM, CD19+ CD27+ IgD-), marginal zone (MZ, CD19+ CD27+ IgD+), naives (CD19+ CD27- IgD+), transitional (CD19+ CD27- IgD+ CD24high CD38high), circulating plasma cells (CD19+ CD27+ IgD- CD27high CD38high) and CD21low B cells (CD19+ CD21low CD38-), a subset abnormally expanded in WAS. Quantification of the B cell replication history was assessed through k-deleting recombination excision circles (KRECs). Analyses were compared to age-matched controls. WAS protein (WASP) expression and vector copy number (VCN) were measured in sorted B cells. Results. All alive GT patients show stable engraftment of functionally corrected lymphoid cells, without adverse events. Transduced B cells number and WASP expression increased progressively after GT. Absolute B cell count attained normal values in all the patients, and correlates with WASP expression and VCN in B cells. IgM levels are below normal ranges in four patients. P3 and P4 attained a B-cell phenotype within normal ranges; P3 discontinued intravenous immunoglobulin (IvIg) replacement. No expansion of CD21low B cells was observed. P1 and P5 (follow-up 18 months) present a variable defect in SM, naives and/or MZ B cells. P1 recently developed autoimmune manifestations; no significant changes were observed concomitantly. A defect in B cell lymphopoiesis was observed before GT as measured by KRECs analysis, normalizing after GT (P1, P3 and P4). Several complications were recorded in patients undergoing mismatched allogeneic HSCT, including dysimmunity, arthritis, developmental deficit and infections. Total B cell count normalized in eight patients, IgM levels were low in three. Among patients with available information, four still remain under IvIg replacement. Four patients developed a mixed lymphoid and myeloid chimerism, variably associated with low B cell count, low IgM and IvIg replacement. A complete B cell assessment for these patients is ongoing. Conclusions. B cell transgene expression is obtained after lentiviral vector-mediated GT in WAS patients and is associated with improved B cell lymphopoiesis. A correct B cell phenotype is observed in two patients who did not receive rituximab prior GT. The question whether this is related to the treatment will need a longer follow-up to be answered. Patients undergoing mismatched allogeneic HSCT present a higher frequency of complications. Although a higher proportion of these patients discontinued IvIg replacement, B cell reconstitution is not optimal. Analysis of patients in particular with mixed chimerism will provide important information in the setting of GT. The analysis of B cell reconstitution after GT and mismatched allogeneic HSCT deserves particular attention in the assessment of immunological reconstitution. Disclosures No relevant conflicts of interest to declare.

Description: Key Points SCID-X1 patients treated with gene therapy show faster T-cell development compared with patients treated with haploidentical HSCT.

Description: Introduction: β-globin gene transfer into hematopoietic stem cells (HSCs) has the potential to reduce or eliminate the symptoms of severe sickle cell disease (SCD) and reduce or eliminate transfusion requirements in transfusion-dependent β-thalassemia (TDT). LentiGlobin Drug Product (DP) contains autologous CD34+ cells transduced with the BB305 lentiviral vector, which encodes a human β-globin gene containing a single point mutation (AT87Q) designed to confer anti-sickling properties similar to those observed with γ-globin. We previously reported proof of concept for LentiGlobin DP treatment in severe SCD and early data from 4 treated patients with TDT. We now report 18 months of follow-up for the patient with SCD and between 9 and 30 months of follow-up for the 4 patients with TDT. Patients (5-35 years of age) with severe SCD (e.g. ≥2 acute chest syndrome episodes or ≥2 vaso-occlusive crises [VOC] in preceding year/in year prior to regular transfusions) or TDT (≥100mL/kg of packed red blood cells [RBCs] per year) were enrolled. Following mobilization and apheresis (for TDT) or bone marrow harvest (for SCD), autologous CD34+ cells were transduced with the BB305 lentiviral vector. Patients underwent myeloablative conditioning with busulfan prior to infusion of the transduced cells. After infusion, patients were monitored for hematologic engraftment, vector copy number (VCN), and HbAT87Q expression. Disease-specific assessments included transfusion requirements for TDT, or VOCs and hospitalizations for SCD. Safety assessments included adverse events (AEs) and integration site analysis. Results: As of July 2016, 1 patient with severe SCD (male; 13 years old) and 4 patients with TDT (2 male, 2 female; 16-19 years old) have received LentiGlobin DP in Study HGB-205. The median LentiGlobin DP cell dose was 8.9 (range 5.6-13.6) x 106 CD34+ cells/kg with a DP VCN of 1.2 (range: 0.8-2.0) vector copies/diploid genome. Median post-infusion follow-up as of July 6, 2016 is 20.8 months (range 9.5-31.3). All subjects successfully engrafted after receiving LentiGlobin DP, with a median time to neutrophil engraftment of 17 days (range 14-38 days). VCN in peripheral blood has remained generally consistent from Month 3 in all patients with a range of 0.2 to 3.4 at last measurement. The toxicity profile observed from start of conditioning to latest follow-up remains consistent with myeloablative conditioning with single-agent busulfan, with no DP-related ≥Grade 3 AEs or serious AEs and no evidence of clonal dominance reported to date. Three patients with TDT have β0/βE genotypes and 1 is homozygous for the severe β+ mutation IVS1 nt 110 G〉A. The 2 patients who have completed the 2-year primary follow-up period (both β0/βE) have not required RBC transfusions for 31 and 28 months, with total Hb of 10.9 and 13.5 g/dL, and HbAT87Q expression of 7.7 and 10.1 g/dL, respectively, at most recent study visit. Iron chelation has been discontinued and phlebotomy initiated for 1 of the patients. The remaining patient with β0/βE genotype has 9 months of follow-up and has not required transfusions since 4 days post-LentiGlobin DP infusion, achieving a total Hb of 11.3 g/dL at last study visit. The patient with the severe IVS1 genotype has 12 months of follow-up and has been free of transfusions for 9 months, with a total Hb of 8.3 g/dL at last study visit. The patient with severe SCD, who prior to study enrollment received regular RBC transfusions, has experienced no clinical symptoms or complications of SCD in the 18 months since treatment, despite discontinuing transfusions 3 months after LentiGlobin DP infusion. Total Hb in this patient was 12.5 g/dL, with 6.6 g/dL HbAT87Q (53%) and 5.7 g/dL HbS (45%) at last study visit. Compared with values at screening, unconjugated bilirubin had dropped 78% (50 to 11 μmol/L), lactate dehydrogenase had dropped 54% (626 to 287 U/L), and reticulocyte count had dropped 45% (238x109/L to 132x109/L) by Month 18. Conclusions: Data from this ongoing Phase 1/2 clinical study suggest that treatment with LentiGlobin DP can result in sustained production of therapeutic HbAT87Q, which ameliorates the clinical and biochemical effects of severe SCD and TDT, with an acceptable safety profile. Gene therapy presents a potentially promising therapy for patients with severe hemoglobinopathies. Further follow-up and additional data from patients are needed to confirm the encouraging results seen to date in this study. Disclosures Ribeil: Bluebirdbio: Consultancy; Addmedica: Research Funding. Payen:bluebird bio: Patents & Royalties. Hermine:Alexion: Research Funding; Celgene: Research Funding; Novartis: Research Funding; AB science: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding, Speakers Bureau. Asmal:bluebird bio: Employment, Equity Ownership. Joseney-Antoine:bluebird bio: Employment, Equity Ownership. De Montalembert:Addmedica: Research Funding; Novartis: Research Funding, Speakers Bureau. Leboulch:bluebird bio, Inc: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.

Description: The historical model of hematopoiesis, mainly derived from murine studies, is based on the existence of a single hematopoietic stem cell (HSC) capable of generating all blood cell lineages. However this model has been challenged by the proposal of four types of murine HSC, which differ by their relative contribution to the myeloid and lymphoid lineages. Here we have used data from a gene therapy trial to treat Wiskott-Aldrich syndrome (WAS) to explore hematopoiesis in humans. In the trial, the therapeutic vector (lentivirus) integrates into the genome at unique positions in each hematopoietic stem and progenitor cell (HSPC) and is consequently transmitted to all its progeny. Thus hematopoietic ontogeny in humans can be inferred by tracking the appearance of unique integration sites in fractionated blood cell populations. This provides a unique opportunity to model the developmental complexity of the human haematological system. Considerable effort over the last 15 years has been devoted to optimizing retroviral integration sites (RIS) analysis using ligation mediated PCR (LM-PCR), combined with acoustic shearing and high-throughput Illumina sequencing. Acoustic shearing enables more precise quantification of RIS abundance through the enumeration of the various sizes of shear fragments (SonicAbundance) containing a given RIS, which correspond to individual ancestor HSPC and its blood progeny. In four WAS patients treated by gene therapy, we have sorted peripheral blood samples for 5 cell types: myeloid (granulocytes and monocytes) and lymphoid subpopulations (T, B and NK cells), and analysed their RIS profile. Each RIS corresponds to a particular stem/progenitor cell clone, with a particular pattern defined by its presence or absence in each of the 5 lineages. These data are then use to reconstruct aspects of the hematopoietic hierarchy. In order to face the challenging issue of cell sorting contamination we have been using a stringent sort precision mode and we treat residual contamination explicitly in downstream statistical models. Using these approaches, we have characterized up to tens of thousands RIS per patients with a follow up of 4 years. In order to minimize biases due to sparse sampling, we concentrate on the more abundant RIS clones that can be more easily caught and are therefore analysed more reliably. We showed that a significant fraction of RIS clones are detected in a single lineage, while other RIS clones are characterized by different levels of contribution to the myeloid and lymphoid lineages, highlighting the heterogeneity of human HSC. Clones contributing to all 5 lineages are readily recovered but this study also unravels a diversity of inferred hematopoietic programs with various potentials contributing to human blood homeostasis. Longitudinal analysis of clonal dynamics is ongoing, with preliminary results highlighting the maintenance of this heterogeneity of HSPC over time. These new findings provide unique data on human hematopoiesis based on gene corrected WAS patients. Disclosures No relevant conflicts of interest to declare.