A new step in understanding stem cell mobilization in patients with Fanconi anemia: A bridge to gene therapy

BACKGROUND

Fanconi anemia (FA) is an inherited disorder characterized clinically by congenital abnormalities, progressive bone marrow failure (BMF), and a predisposition to malignancy. Gene therapy (GT) of FA, via the infusion of gene-corrected peripheral blood (PB) autologous hematopoietic stem cells (HSCs), may constitute a cure for BMF. GT bypasses the donor restrictions and adverse events associated with allogenic HSC transplantation. However, adequate harvesting of PB-HSCs is a crucial determinant of successful engraftment in gene therapy. Harvesting the low numbers of HSCs in patients with FA is particularly challenging.

STUDY DESIGN AND METHODS

This open-label phase I/II trial evaluates the feasibility and safety of co-administration of G-CSF and plerixafor in patients with FA for the mobilization and harvesting of peripheral HSCs, intending to use them in a gene therapy trial. Patients with mutations in the FANCA gene received two subcutaneous injections of G-CSF (6 μg/kg × 2/d from D1 to D8. Plerixafor (0.24 mg/kg/d) was administered 2 h before apheresis (from D5 onward).

RESULTS

CD34⁺ cells were mobilized for four patients quickly but transiently after the plerixafor injection. One patient had a CD34⁺ cell count of over 100/μl; the mobilization peaked 2 h after the injection and lasted for more than 9 h. There were no short-term adverse events associated with the mobilization or harvesting procedures.

CONCLUSION

Our data in patients with FA show that the mobilization of HSCs with G-CSF and plerixafor is safe and more efficient in younger individuals without BMF.

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.

Chronic Intestinal Pseudo-Obstruction and Lymphoproliferative Syndrome as a Novel Phenotype Associated With Tetratricopeptide Repeat Domain 7A Deficiency

Mutations in the tetratricopeptide repeat domain 7A (TTC7A) gene cause very early onset inflammatory bowel diseases (VOIBD) or multiple intestinal atresia associated with immune deficiency of various severities, ranging from combined immune deficiency to mild lymphopenia. In this manuscript, we report the clinical, biological and molecular features of a patient born from consanguineous parents, presenting with recurrent lymphoproliferative syndrome and pan-hypergammaglobulinemia associated with chronic intestinal pseudo obstruction (CIPO). Genetic screening revealed the novel c.974G>A (p.R325Q) mutation in homozygosity in the TTC7A gene. The patient's phenotype differs significantly from that previously associated with TTC7A deficiency in humans. It becomes closer to the one reported in the ttc7a-deficient mice that invariably develop a proliferative lymphoid and myeloid disorder. Functional studies showed that the extreme variability in the clinical phenotype couldn't be explained by the cellular phenotype. Indeed, the patient's TTC7A mutation, as well as the murine-ttc7 mutant, have the same functional impact on protein expression, DNA instability and chromatin compaction, as the other mutations that lead to classical TTC7A-associated phenotypes. Co-inheritance of genetic variants may also contribute to the unique nature of the patient's phenotype. The present case report shows that the clinical spectrum of TTC7A deficiency is much broader than previously suspected. Our findings should alert the physicians to consider screening of TTC7A mutations in patients with lymphoproliferative syndrome and hypergammaglobulinemia and/or chronic intestinal pseudo-obstruction.

Haploidentical Hematopoietic Stem Cell Transplantation with Post-Transplant Cyclophosphamide for Primary Immunodeficiencies and Inherited Disorders in Children

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment for some inherited disorders, including selected primary immunodeficiencies (PIDs). In the absence of a well-matched donor, HSCT from a haploidentical family donor (HIFD) may be considered. In adult recipients high-dose post-transplant cyclophosphamide (PTCY) is increasingly used to mitigate the risks of graft failure and graft-versus-host disease (GVHD). However, data on the use of PTCY in children (and especially those with inherited disorders) are scarce. We reviewed the outcomes of 27 children transplanted with an HIFD and PTCY for a PID (n = 22) or osteopetrosis (n = 5) in a single center. The median age was 1.5 years (range, .2 to 17). HSCT with PTCY was a primary procedure (n = 21) or a rescue procedure after graft failure (n = 6). The conditioning regimen was myeloablative in most primary HSCTs and nonmyeloablative in rescue procedures. After a median follow-up of 25.6 months, 24 of 27 patients had engrafted. Twenty-one patients are alive and have been cured of the underlying disease. The 2-year overall survival rate was 77.7%. The cumulative incidences of acute GVHD grade ≥ II, chronic GVHD, and autoimmune disease were 45.8%, 24.2%, and 29.6%, respectively. There were 2 cases of grade III acute GVHD and no extensive cGVHD. The cumulative incidences of blood viral replication and life-threatening viral events were 58% and 15.6%, respectively. There was evidence of early T cell immune reconstitution. In the absence of an HLA-identical donor, HIFD HSCT with PTCY is a viable option for patients with life-threatening inherited disorders.

Gene Therapy in Patients with Transfusion-Dependent β-Thalassemia

BACKGROUND

Donor availability and transplantation-related risks limit the broad use of allogeneic hematopoietic-cell transplantation in patients with transfusion-dependent β-thalassemia. After previously establishing that lentiviral transfer of a marked β-globin (β^A-T87Q) gene could substitute for long-term red-cell transfusions in a patient with β-thalassemia, we wanted to evaluate the safety and efficacy of such gene therapy in patients with transfusion-dependent β-thalassemia.

METHODS

In two phase 1-2 studies, we obtained mobilized autologous CD34+ cells from 22 patients (12 to 35 years of age) with transfusion-dependent β-thalassemia and transduced the cells ex vivo with LentiGlobin BB305 vector, which encodes adult hemoglobin (HbA) with a T87Q amino acid substitution (HbA^T87Q). The cells were then reinfused after the patients had undergone myeloablative busulfan conditioning. We subsequently monitored adverse events, vector integration, and levels of replication-competent lentivirus. Efficacy assessments included levels of total hemoglobin and HbA^T87Q, transfusion requirements, and average vector copy number.

RESULTS

At a median of 26 months (range, 15 to 42) after infusion of the gene-modified cells, all but 1 of the 13 patients who had a non-β⁰/β⁰ genotype had stopped receiving red-cell transfusions; the levels of HbA^T87Q ranged from 3.4 to 10.0 g per deciliter, and the levels of total hemoglobin ranged from 8.2 to 13.7 g per deciliter. Correction of biologic markers of dyserythropoiesis was achieved in evaluated patients with hemoglobin levels near normal ranges. In 9 patients with a β⁰/β⁰ genotype or two copies of the IVS1-110 mutation, the median annualized transfusion volume was decreased by 73%, and red-cell transfusions were discontinued in 3 patients. Treatment-related adverse events were typical of those associated with autologous stem-cell transplantation. No clonal dominance related to vector integration was observed.

CONCLUSIONS

Gene therapy with autologous CD34+ cells transduced with the BB305 vector reduced or eliminated the need for long-term red-cell transfusions in 22 patients with severe β-thalassemia without serious adverse events related to the drug product. (Funded by Bluebird Bio and others; HGB-204 and HGB-205 ClinicalTrials.gov numbers, NCT01745120 and NCT02151526 .).

Ontogeny of human mucosal-associated invariant T cells and related T cell subsets

There are very few human MAIT cells in cord blood. Ben Youssef et al. show that they slowly expand during childhood and point to a critical role of the TCRαβ repertoire in determining their unique ability to recognize MR1-restricted microbial antigens.

Mucosal-associated invariant T (MAIT) cells are semi-invariant Vα7.2⁺ CD161^highCD4⁻ T cells that recognize microbial riboflavin precursor derivatives such as 5-OP-RU presented by MR1. Human MAIT cells are abundant in adult blood, but there are very few in cord blood. We longitudinally studied Vα7.2⁺ CD161^high T cell and related subset levels in infancy and after cord blood transplantation. We show that Vα7.2⁺ and Vα7.2⁻ CD161^high T cells are generated early during gestation and likely share a common prenatal developmental program. Among cord blood Vα7.2⁺ CD161^high T cells, the minority recognizing MR1:5-OP-RU display a TRAV/TRBV repertoire very similar to adult MAIT cells. Within a few weeks of life, only the MR1:5-OP-RU reactive Vα7.2⁺ CD161^high T cells acquire a memory phenotype. Only these cells expand to form the adult MAIT pool, diluting out other Vα7.2⁺ CD161^high and Vα7.2⁻ CD161^high populations, in a process requiring at least 6 years to reach adult levels. Thus, the high clonal size of adult MAIT cells is antigen-driven and likely due to the fine specificity of the TCRαβ chains recognizing MR1-restricted microbial antigens.

Probable DRESS syndrome induced by IL-1 inhibitors

Interleukin (IL)-1 inhibitors have been increasingly used for treating autoinflammatory diseases during the last 10 years, but the spectrum of their possible side effects is not yet fully known. Here, we bring physicians’ attention to a new severe complication of IL-1 inhibitors, manifesting as a probable drug reaction with eosinophilia and systemic symptoms (DRESS) in two patients.

Cutaneous and Visceral Chronic Granulomatous Disease Triggered by a Rubella Virus Vaccine Strain in Children With Primary Immunodeficiencies

Persistence of rubella live vaccine has been associated with chronic skin granuloma in 3 children with primary immunodeficiency. We describe 6 additional children with these findings, including 1 with visceral extension to the spleen.

Mammalian target of rapamycin inhibition counterbalances the inflammatory status of immune cells in patients with chronic granulomatous disease

BACKGROUND

Chronic granulomatous disease (CGD) is a primary immunodeficiency caused by defective production of reactive oxygen species in phagocytic cells that results in life-threatening infections and severe inflammatory manifestations. The treatment of inflammatory manifestations remains challenging because it can be associated with an increased risk of infections. Previous studies have shown that phagocytes from patients with CGD display a defect in autophagy and a reactive oxygen species-independent activation of the inflammasome.

OBJECTIVE

Because the intersections between autophagy and the inflammasome have been observed in patients with various diseases and microbial infections, we investigated the possible benefit of restoring the autophagy defect through rapamycin, a potent autophagy inducer, in the setting of CGD.

METHODS

We studied 15 patients given a diagnosis of CGD and followed in our institution. All patients were free of any active infection at the time of the study.

RESULTS

We show that patients with CGD present a consistent inflammatory phenotype defined by (1) increased nonclassical and intermediate monocytes, (2) a proinflammatory state of mononuclear phagocytes with increased IL-1β and TNF-α content, (3) a T_H17 bias of CD4⁺ T cells, (4) and an increase in IL-17A-secreting neutrophil numbers. We document the reversion of CGD inflammatory status by the mammalian target of rapamycin inhibitor rapamycin on the different immune cell subsets. We also provide evidence for the enhancement of rapamycin's inhibitory effect on IL-1β secretion by the IL-1 receptor antagonist anakinra in phagocytes of patients with CGD.

CONCLUSION

Altogether, these data open new therapeutic approaches for CGD-related inflammatory manifestations.