Severe hematopoietic stem cell inflammation compromises chronic granulomatous disease gene therapy

X-linked chronic granulomatous disease (CGD) is associated with defective phagocytosis, life-threatening infections, and inflammatory complications. We performed a clinical trial of lentivirus-based gene therapy in four patients (NCT02757911). Two patients show stable engraftment and clinical benefits, whereas the other two have progressively lost gene-corrected cells. Single-cell transcriptomic analysis reveals a significantly lower frequency of hematopoietic stem cells (HSCs) in CGD patients, especially in the two patients with defective engraftment. These two present a profound change in HSC status, a high interferon score, and elevated myeloid progenitor frequency. We use elastic-net logistic regression to identify a set of 51 interferon genes and transcription factors that predict the failure of HSC engraftment. In one patient, an aberrant HSC state with elevated CEBPβ expression drives HSC exhaustion, as demonstrated by low repopulation in a xenotransplantation model. Targeted treatments to protect HSCs, coupled to targeted gene expression screening, might improve clinical outcomes in CGD.

Ex vivo generated human T-lymphoid progenitors as a tool to accelerate immune reconstitution after partially HLA compatible hematopoietic stem cell transplantation or after gene therapy

Prolonged T-cell immunodeficiency following HLA- incompatible hematopoietic stem cell transplantation (HSCT) represents a major obstacle hampering the more widespread use of this approach. Strategies to fasten T-cell reconstitution in this setting are highly warranted as opportunistic infections and an increased risk of relapse account for high rates of morbidity and mortality especially during early month following this type of HSCT. We have implemented a feeder free cell system based on the use of the notch ligand DL4 and cytokines allowing for the in vitro differentiation of human T-Lymphoid Progenitor cells (HTLPs) from various sources of CD34+ hematopoietic stem and precursor cells (HSPCs). Co- transplantion of human T-lymphoid progenitors (HTLPs) and non- manipulated HSPCs into immunodeficient mice successfully accelerated the reconstitution of a polyclonal T-cell repertoire. This review summarizes preclinical data on the use of T-cell progenitors for treatment of post- transplantation immunodeficiency and gives insights into the development of GMP based protocols for potential clinical applications including gene therapy approaches. Future clinical trials implementing this protocol will aim at the acceleration of immune reconstitution in different clinical settings such as SCID and leukemia patients undergoing allogeneic transplantation. Apart from pure cell-therapy approaches, the combination of DL-4 culture with gene transduction protocols will open new perspectives in terms of gene therapy applications for primary immunodeficiencies.

Vascular access for optimal hematopoietic stem cell collection

BACKGROUND

Autologous and allogeneic hematopoietic stem cell transplantation of cytokine-mobilized peripheral blood stem cells (PBSCs) is increasingly used to treat patients with hematologic disorders. Different types of vascular access have been exploited for the apheresis procedure, including peripheral veins (PV) and central venous catheter (CVC). In some cases, PV access is unavailable. There are few published data on the efficiency and quality of harvesting with different types of vascular access. This study brings out complications and morbidity of this procedure linked to these different access.

METHODS

We performed a comparative, retrospective, single-center study of hematopoietic stem cell collection using these two types of vascular access. We compared the efficiency and complication rate for 617 adults apheresis sessions in 401 patients and healthy donors, for PBSC collection via PV or CVC between 2010 and 2016. The quality of the HSC product was evaluated in terms of the total CD34 + count and neutrophil contamination.

RESULTS

The PV and CVC groups did not differ significantly in terms of the quality of the apheresis product, mean ± SD CD34 + cells collected in PV group was 383.1 ± 402.7 × 10e6 and 298.8 ± 372.7 × 10e6 and the level of neutrophil contamination was 21.0 ± 17.8% in the PV group and 20.6 ± 18.4% in the CVC group. The complication rate did not differ between the two groups.

CONCLUSION

The type of vascular access for apheresis hematopoietic stem cell harvesting must be determined by trained staff. Successful harvesting can be performed via PV then CVC is not needed or not available.

Extensive multilineage analysis in patients with mixed chimerism after allogeneic transplantation for sickle cell disease: insight into hematopoiesis and engraftment thresholds for gene therapy

Although studies of mixed chimerism following hematopoietic stem cell transplantation in patients with sickle cell disease (SCD) may provide insights into the engraftment needed to correct the disease and into immunological reconstitution, an extensive multilineage analysis is lacking. We analyzed chimerism simultaneously in peripheral erythroid and granulomonocytic precursors/progenitors, highly purified B and T lymphocytes, monocytes, granulocytes and red blood cells (RBC). Thirty-four patients with mixed chimerism and ≥12 months of follow-up were included. A selective advantage of donor RBC and their progenitors/precursors led to full chimerism in mature RBC (despite partial engraftment of other lineages), and resulted in the clinical control of the disease. Six patients with donor chimerism <50% had hemolysis (reticulocytosis) and higher HbS than their donor. Four of them had donor chimerism <30%, including a patient with AA donor (hemoglobin >10 g/dL) and three with AS donors (hemoglobin <10 g/dL). However, only one vaso-occlusive crisis occurred with 68.7% HbS. Except in the patients with the lowest chimerism, the donor engraftment was lower for T cells than for the other lineages. In a context of mixed chimerism after hematopoietic stem cell transplantation for SCD, myeloid (rather than T cell) engraftment was the key efficacy criterion. Results show that myeloid chimerism as low as 30% was sufficient to prevent a vaso-occlusive crisis in transplants from an AA donor but not constantly from an AS donor. However, the correction of hemolysis requires higher donor chimerism levels (i.e ≥50%) in both AA and AS recipients. In the future, this group of patients may need a different therapeutic approach.

Safety of CD34+ Hematopoietic Stem Cells and CD4+ T Lymphocytes Transduced with LVsh5/C46 in HIV-1 Infected Patients with High-Risk Lymphoma

Although the risk of developing lymphoma has decreased in the highly active antiretroviral therapy era, this cancer remains the major cause of mortality in HIV-infected patients. Autologous hematopoietic stem cell transplantation (ASCT) outcome does not differ for HIV-infected versus HIV-uninfected patients. We propose to develop a new treatment for HIV-associated high-risk lymphoma based on autologous transplantation of two genetically modified products: CD4⁺ T lymphocytes and CD34⁺ hematopoietic stem cells (HSPCs). The cells will be transduced ex vivo with the Cal-1 lentiviral vector encoding for both a short hairpin RNA (shRNA) against CCR5 (sh5) and the HIV-1 fusion inhibitor C46. The transduced cells will be resistant to HIV infection by two complementary mechanisms: impaired binding of the virus to the cellular CCR5 co-receptor and decreased fusion of the virus as C46 interacts with gp41 and inhibits HIV infection. This phase I/II pilot study, also entitled GENHIV, will involve two French participating centers: Saint Louis Hospital and Necker Hospital in Paris. We plan to enroll five HIV-1-infected patients presenting with high-risk lymphoma and require a treatment with ASCT. The primary objective of this study is to evaluate the safety, feasibility, and success of engraftment of Cal-1 gene-transduced CD4⁺ T lymphocytes and CD34⁺ HSPCs.

Plerixafor enables safe, rapid, efficient mobilization of hematopoietic stem cells in sickle cell disease patients after exchange transfusion

Sickle cell disease is characterized by chronic anemia and vaso-occlusive crises, which eventually lead to multi-organ damage and premature death. Hematopoietic stem cell transplantation is the only curative treatment but it is limited by toxicity and poor availability of HLA-compatible donors. A gene therapy approach based on the autologous transplantation of lentiviral-corrected hematopoietic stem and progenitor cells was shown to be efficacious in one patient. However, alterations of the bone marrow environment and properties of the red blood cells hamper the harvesting and immunoselection of patients' stem cells from bone marrow. The use of Filgrastim to mobilize large numbers of hematopoietic stem and progenitor cells into the circulation has been associated with severe adverse events in sickle cell patients. Thus, broader application of the gene therapy approach requires the development of alternative mobilization methods. We set up a phase I/II clinical trial whose primary objective was to assess the safety of a single injection of Plerixafor in sickle cell patients undergoing red blood cell exchange to decrease the hemoglobin S level to below 30%. The secondary objective was to measure the efficiency of mobilization and isolation of hematopoietic stem and progenitor cells. No adverse events were observed. Large numbers of CD34⁺ cells were mobilized extremely quickly. Importantly, the mobilized cells contained high numbers of hematopoietic stem cells, expressed high levels of stemness genes, and engrafted very efficiently in immunodeficient mice. Thus, Plerixafor can be safely used to mobilize hematopoietic stem cells in sickle cell patients; this finding opens up new avenues for treatment approaches based on gene addition and genome editing. Clinicaltrials.gov identifier: NCT02212535.

Associated factors of umbilical cord blood collection quality

After 30 years of hematopoietic stem cell use for various indications, umbilical cord blood is considered as an established source of cells with marrow and postmobilization peripheral blood. The limited number of cells still remains a problematic element restricting their use, especially in adults who require to be grafted with a higher cell number. Improving the quality of harvested cord blood, at least in terms of volume and amount of cells, is essential to decrease the number of discarded units. In this review, we examine several variables related to parturient, pregnancy, labor, delivery, collection, the newborn, umbilical cord, and placenta. We aim to understand the biologic mechanisms that can impact cord blood quality. This knowledge will ultimately allow targeting donors, which could provide a rich graft and improve the efficiency of the collection.