ADA-transduced hematopoietic stem cells for severe combined immunodeficiency

This study is evaluating a gene therapy treatment in which the adenosine deaminase (ADA) gene is retrovirally delivered into hematopoietic stem cells and transplanted in patients with severe combined immunodeficiency disease (SCID) due to a mutant ADA gene. The SCID patients were treated by nonmyeloablative chemotherapy, followed by infusion of autologous hematopoietic stem cells that had been transduced with a retroviral vector bearing the ADA gene. Treatment was not associated with adverse events during a median follow-up period of 4 years. There was restoration of immune function, protection against severe infection in 90% of patients and improvement in the patients' physical development. Integration of retroviral vectors induces minor changes in the transcriptional activity of T cells from ADA-SCID patients treated with gene therapy.