Cell and gene therapy for blood disorders. Modeling of novel treatment strategies for Gaucher type 1 disease and Diamond-Blackfan anemia in mice

University dissertation from Division of Molecular Medicine and Gene Therapy

Abstract: Gaucher disease type 1 (GD type 1) and Diamond-Blackfan anemia (DBA) are rare genetic disorders affecting the hematopoietic system and routinely treated by administration of drugs with variable clinical efficacy. Though effective in alleviating disease symptoms in large cohorts of patients, these treatment options have the major drawback of being non-curative. Currently, bone marrow transplantation (BMT) from an immune compatible donor is the only corrective therapy for both GD type I and DBA. However, donor availability and standard BMT procedures are associated with an increased risk of morbidity and mortality. Gene therapy, entailing ex vivo genetic correction of autologous hematopoietic stem/progenitor cells (HSPCs) by retroviral vectors, has the potential of becoming a future therapeutic option for both GD type 1 and DBA patients unresponsive to conventional therapies. Gene therapy of autologous HSPCs circumvents the need for finding an HLA-matched donor and could potentially require a less rigid pre-conditioning protocol, thereby reducing risks associated with allogeneic BMTs. We have investigated self-inactivating (SIN) lentiviral vectors with cellular promoters in a murine disease model displaying clinical GD type I symptoms (Paper I). From our studies we conclude that a modest increase of GCase activity by enforced expression of GBA, primarily in tissue macrophages, effectively reverses pathophysiological symptoms in GD type 1 mice. Furthermore, we observe a relatively safe integration profile of the lentiviral vectors. Taken together, this provides support for the development of a clinical gene therapy protocol for GD type 1 patients using similar vectors. In Paper II we have evaluated a non-myeloablative conditioning protocol for autologous BMTs for treatment of DBA by employing a murine disease model with downregulated expression of ribosomal protein S19 (RPS19), the most frequently mutated gene in DBA patients. We show efficient reversal of key clinical hematopoietic symptoms after syngeneic BMTs in both sub-lethally and non-irradiated recipients with RPS19 deficiency. A reduced intensity conditioning protocol would be highly valuable in a clinical gene therapy setting for DBA, reducing risks associated with full myeloablation preceding BMT. In Paper III we report the finding of a novel regulator of adult HSCs, the Schlafen-2 protein. In extensive in vivo studies we determine that adult murine HSCs with mutated Schlafen-2 protein have reduced regenerative capacity. Identification of factors essential for HSC regulation aids not only in our basic understanding of hematopoiesis, but also plausibly to improved future HSC-based treatments. In summary, this thesis focuses on translational and basic research evaluating novel cell and gene therapeutic strategies for GD type 1 and DBA.