Improved Long-term In Vivo Lentiviral Gene Therapy for Chronic Granulomatous Disease

Abstract Chronic granulomatous disease (CGD) is a congenital immunodeficiency characterized by lack of reactive oxygen species in phagocytes. We developed an in vivo gene therapy strategy based on intravenous (iv) injection of lentiviral vectors (LVs) in X-CGD mice. A non-myeloablative chemo-conditioning regimen using busulfan, cyclophosphamide and dexamethasone was developed to improve iv LV gene delivery efficiency. The X-CGD mice received two LVs injections. After the second injection, antibody response to LV particle-associated p24-protein was examined by Western blot. We detected increased gene transfer without anti-p24 antibody response. However, the blood vector copy number (VCN) was gradually reduced after 3–12 months. To improve gene delivery into hematopoietic stem cells (HSCs), the mice were treated with AMD3100 to mobilize HSCs before LV injection. To confirm HSCs gene transfer, we transplanted the HSCs from the LV- CYBB -treated CGD mice into untreated CGD mice. The result showed successful passage of LV- CYBB HSCs to recipient mice. Thus, by combining chemo-conditioning and AMD3100 mobilization prior to the iv LV injection, improved in vivo long-term LV gene transfer into HSCs could be established. This improved iv LV gene delivery strategy could reduce both the risk and the cost of CGD gene therapy with great potential in translational applications.