Chronic granulomatous disease (CGD) is a rare congenital immunodeficiency characterized by a defect in nicotinamide adenine dinucleotide phosphate oxidase required for phagocytosis. Hematopoietic stem cell (HSC) transplantation is currently the only curative treatment, but it is ladened with morbidities and mortality. Gene therapy is a promising treatment for CGD. However, if not properly designed, the gene therapy approach may not be successful. We engineered lentiviral vectors (LVs) carrying a universal promoter (EF1a) and two myeloid-specific promoters (miR223 and CD68) to drive the expression of green fluorescence protein (GFP) or CYBB, one of the key defective genes causing CGD. Tissue-specific LV expression was investigated in vitro and in a CGD mouse model. We compared GFP expression in both myeloid differentiated and undifferentiated HSCs. The CGD mice were transplanted with LV-modified mouse HSCs to investigate expression of CYBB and restoration of reactive oxygen species. The LV promoters were further compared under low and high-transgenic conditions to assess safety and therapeutic efficacy. A pneumonia disease model based on pathogenic Staphylococcus aureus challenge was established to assess the survival rate and body weight change. All three promoters demonstrated ectopic CYBB expression in vitro and in vivo. The EF1a promoter showed the highest expression of GFP or CYBB in transduced cells, including HSCs without cytotoxicity, whereas the LV-miR223 showed the highest transgene delivery efficiency with high myeloid specificity. Importantly, under low-transgenic condition, only the LV-EF1a-CYBB showed high antibacterial activity in vivo.
Keywords: CGD; CYBB; gene therapy; lentiviral vector; myeloid promoter.