Retrovirus mediated gene transfer as therapy for adenosine deaminase (ADA) deficiency.

ADA deficiency manifests as a severe combined immunodeficiency with profound T-lymphocytopenia. Affected individuals have variable defects of both T- and B-lymphocyte function and greatly increased morbidity and mortality caused by frequent viral and bacterial infection. In 1990 a clinical protocol for the treatment of this disease using retrovirus mediated transfer of the ADA gene into peripheral lymphocytes was begun and in 1993 an amendment permitting gene transfer to CD34+ stem cells isolated from peripheral blood or from umbilical cord blood was approved. Five patients have been treated on this protocol and have been analyzed for the persistence of cells containing the transferred gene and for immunologic reconstitution.