Novel lentiviral vectors for gene therapy of sickle cell disease combining gene addition and gene silencing strategies

Sickle cell disease (SCD) is due to a mutation in the O-globin gene causing production of the toxic sickle hemoglobin (HbS; ex2OS2). Transplantation of autologous hematopoietic stem and progenitor cells (HSPCs) transduced with lentiviral vectors (LVs) expressing an anti-sickling O-globin (OAS) is a promising treatment; however, it is only partially effective, and patients still present elevated HbS levels. Here, we developed a bifunctional LV expressing OAS3-globin and an artificial microRNA (amiRNA) specifically downregulating OS-globin expression with the aim of reducing HbS levels and favoring OAS3 incorporation into Hb tetramers. Efficient transduction of SCD HSPCs by the bifunctional LV led to a substantial decrease of OS-globin transcripts in HSPC-derived erythroid cells, a significant reduction of HbS+ red cells, and effective correction of the sickling phenotype, outperforming OAS gene addition and BCL11A gene silencing strategies. The bifunctional LV showed a standard integration profile, and neither HSPC viability, engraftment, and multilineage differentiation nor the erythroid transcriptome and miRNAome were affected by the treatment, confirming the safety of this therapeutic strategy. In conclusion, the combination of gene addition and gene silencing strategies can improve the efficacy of current LV-based therapeutic approaches without increasing the mutagenic vector load, thus representing a novel treatment for SCD

Therapeutic approach to Gradenigo's syndrome: a case report

Abstract Introduction Traditional management of Gradenigo's syndrome requires aggressive and radical surgery without any attempt to preserve hearing. Recent reports, however, describe a successful outcome after conservative surgical intervention without labyrinthectomy. A similar outcome has also been reported in patients who were only prescribed with antibiotics and did not undergo myringotomy. Case presentation We report the case of a 24-year-old Caucasian Greek woman with Gradenigo's syndrome who was treated by draining her petrous apex via an infralabyrithine approach between her posterior semicircular canal and the jugular bulb. Her inner ear was not sacrificed during the procedure. She presented pre-operatively with ipsilateral conductive hearing loss, which recovered completely four weeks after the surgery. Conclusions Patients with Gradenigo's syndrome may be successfully treated with a combination of long-term permanent drainage and ventilation of the apical cells with corresponding hearing preservation. This can be achieved via a combination of transmastoid, infralabyrinthine and suprajugular approaches, if such would be allowed by the anatomy of the region or if there is enough space between the posterior semicircular canal and the jugular bulb.</p

Optimization of CRISPR/Cas9 Delivery to Human Hematopoietic Stem and Progenitor Cells for Therapeutic Genomic Rearrangements

International audienceEditing the beta-globin locus in hematopoietic stem cells is an alternative therapeutic approach for gene therapy of beta-thalassemia and sickle cell disease. Using the CRISPR/Cas9 system, we genetically modified human hematopoietic stem and progenitor cells (HSPCs) to mimic the large rearrangements in the beta-globin locus associated with hereditary persistence of fetal hemoglobin (HPFH), a condition that mitigates the clinical phenotype of patients with beta-hemoglobinopathies. We optimized and compared the efficiency of plasmid-, lentiviral vector (LV)-, RNA-, and ribonucleoprotein complex (RNP)-based methods to deliver the CRISPR/Cas9 system into HSPCs. Plasmid delivery of Cas9 and gRNA pairs targeting two HPFH-like regions led to high frequency of genomic rearrangements and HbF reactivation in erythroblasts derived from sorted, Cas9(+) HSPCs but was associated with significant cell toxicity. RNA-mediated delivery of CRISPR/Cas9 was similarly toxic but much less efficient in editing the beta-globin locus. Transduction of HSPCs by LVs expressing Cas9 and gRNA pairs was robust and minimally toxic but resulted in poor genome-editing efficiency. Ribonucleoprotein (RNP)-based delivery of CRISPR/Cas9 exhibited a good balance between cytotoxicity and efficiency of genomic rearrangements as compared to the other delivery systems and resulted in HbF upregulation in erythroblasts derived from unselected edited HSPCs