Gene therapy for inherited diseases using heamatopoietic stem cells--gene therapy for patients with chronic granulomatous disease

The possibility of gene therapy for inherited diseases with a single gene mutation in Figure 1 had been verified by the successful treatment with bone marrow transplantation. As the gene therapy method and theory has been progressing rapidly, it is expected that gene therapy will overcome the complications of bone marrow transplantation. Of these inherited diseases, chronic granulomatous disease (CGD) is the one of the most expected disease for gene therapy. CGD is an inherited immune deficiency caused by mutations in any of the following four phox genes encoding subunits of the superoxide generating phagocyte NADPH oxidase. It consists of membranous cytochrom b558 composed of gp91 phox and p22 phox, and four cytosolic components, p47 phox, p67 phox, rac p21 and p40 phox, which translocate to the membrane upon activation. In our group study, more than 220 CGD patients has been enrolled. The incidence of CGD patients was estimated as 1 out of 250,000 births. The expected life span of the CGD patients is 25 to 30 years old by the Kaplan Meier analysis. Comparing with the ratio of CGD subtype in US and Europe, that with p47phox deficiency is lower (less than 10%/o vs. 23%) and that of gp91 phox deficiency is higher (more than 75% vs. 60%). Prophylactic administration of ST antibiotics and IFN-gamma and bone marrow transplantation have been successfully employed in our therapeutic strategy. However, it is necessary to develop the gene therapy technology for CGD patients as more promising treatment. In the current study we constructed two retrovirus vectors; MFGS-gp91/293 SPA which contains only the therapeutic gp91 phox gene, a bicistronic retrovirus pHa-MDR-IRES-gp91/PA317 which carries a multi drug resistant gene (MDR1) and the gp91phox gene connected with an internal ribosome entry site (IRES). We demonstrate high efficiency transduction of gp 91 phox to CGD EB virus established cell line with high levels of functional correction of the oxidase by MFGS-gp91 and by pHa-MDR-IRES-gp91, respectively. We also demonstrate sufficient transduction of gp91 phox to CD34+ hematopoietic stem cell from the patients with gp91 phox deficiency by MFGS-gp91/293 SPA. Our current studies suggest that the combination of the 293-SPA packaging system and the bicistronic retrovirus system inserted MDR1 gene make our CGD gene therapy more feasible for clinical application.