Lentiviral Hematopoietic Stem Cell Gene Therapy in Patients with Wiskott-Aldrich Syndrome

Abstract

Wiskott-Aldrich Syndrome (WAS) is an inherited immunodeficiency caused by mutations in the gene encoding WASP, a protein regulating the cytoskeleton. Hematopoietic stem/progenitor cell (HSPC) transplants can be curative but, when matched donors are unavailable, infusion of autologous HSPCs modified ex vivo by gene therapy is an alternative approach. We used a lentiviral vector encoding functional WASP to genetically correct HSPCs from three WAS patients and re-infused the cells after reduced-intensity conditioning regimen. All three patients showed stable engraftment of WASP-expressing cells and improvements in platelet counts, immune functions, and clinical score. Vector integration analyses revealed highly polyclonal and multi-lineage haematopoiesis resulting from the gene corrected HSPCs. Lentiviral gene therapy did not induce selection of integrations near oncogenes and no aberrant clonal expansion was observed after 20–32 months. Although extended clinical observation is required to establish long-term safety, lentiviral gene therapy represents a promising treatment for WAS.

Epigenetic Memory Underlies Cell-Autonomous Heterogeneous Behavior of Hematopoietic Stem Cells

“…These include cells that have distinctive behaviors in terms of cell production and lineage bias (Dykstra et al, 2007;Picelli et al, 2013). Hematopoietic stem cells have been demonstrated to exhibit bias toward myeloid, lymphoid, or megakaryocytic lineage upon transplantation of single cells (Dykstra et al, 2007(Dykstra et al, , 2011Morita et al, 2010), on ex vivo barcoding and transplantation of populations (Aiuti et al, 2013;Gerrits et al, 2010;Jordan and Lemischka, 1990;Lemischka, 1993;Lemischka et al, 1986;Lu et al, 2011;Mazurier et al, 2004;Shi et al, 2002;Snodgrass and Keller, 1987), or by retrotransposon tagging of endogenous cells (Sun et al, 2014b). Further, single-cell transplant data have been coupled with single-cell gene expression analysis on different cells to resolve subpopulations with corresponding gene expression and repopulation potential (Wilson et al, 2015).…”

Lentiviral Vector Gene Therapy Protects XCGD Mice From Acute Staphylococcus aureus Pneumonia and Inflammatory Response

“…While these VCNs are in line with previous studies from our group and others [36][37][38] it is expected that lower VCNs would be observed in the clinical application based on our previous studies in human CD34+ cells, 23 and clinical trials in other therapeutic areas. 34,39 Unfortunately, no published data is available regarding the protection from the infections in clinical trials with lentiviral vectors encoding for gp91phox. In a previous retroviral gene therapy trial, two patients cleared infections with 4-25% oxidase activity and are clinically well with very low persistent marking level (0.03 and 0.7%) while another succumbed to the infection after losing gene marking.…”

“…These results would suggest that a reduced-intensity conditioning, such as the one adopted for previous CGD trials or other diseases, could be used. 34 Our study included a wide distribution of VCN (ranging from 0.3 to 9.8). While these VCNs are in line with previous studies from our group and others [36][37][38] it is expected that lower VCNs would be observed in the clinical application based on our previous studies in human CD34+ cells, 23 and clinical trials in other therapeutic areas.…”

Quantitative Shearing Linear Amplification Polymerase Chain Reaction: An Improved Method for Quantifying Lentiviral Vector Insertion Sites in Transplanted Hematopoietic Cell Systems

“…4,[32][33][34] However, these methods sometimes lack quantitative standards and may not accurately measure clone size in all instances, particularly when restriction enzyme digestion is used to facilitate adapter ligation. 13,17,35 Recently, random DNA shearing by sonication and count of shear site was introduced and appear to have better accuracy and sensitivity.…”