Long-Term Follow-Up of Patients Treated by Gene Therapy for X-Linked Chronic Granulomatous Disease.

Chronic granulomatous disease (CGD) is a primary immunodeficiency in which phagocytic cells of affected patients have impaired antimicrobial activity due to a defect in the production of reactive oxygen species (ROS). CGD is caused by mutations in any one of four genes encoding for the subunits of the NADPH oxidase complex. Although curable by HSC transplantation, this strategy is usually limited only to patients with HLA-matched sibling or unrelated donors, as mismatched transplantation is associated with high morbidity and mortality due to graft failure and slow immune reconstitution. A therapeutic alternative for CGD patients is the genetic modification of autologous HSC. In January 2004 we initiated a Phase I/II clinical trial for X-CGD patients including conditioning with busulfan (8 mg/kg/total dose) prior to infusion of genetically modified HSC. G-CSF mobilized CD34+ cells from 2 adult patients (25 and 26 years) were transduced ex-vivo with a monocistronic gp91phox retroviral vector.