Retroviral WASP gene transfer into human hematopoietic stem cells reconstitutes the actin cytoskeleton in myeloid progeny cells differentiated in vitro

OBJECTIVE: Wiskott-Aldrich syndrome (WAS) is a primary immunodeficiency disorder characterized by recurrent infections, autoimmunity, microthrombocytopenia, and susceptibility to malignant tumors. Compared with the conventional treatment using allogeneic bone marrow transplantation, hematopoietic stem cell gene therapy might offer more specific and less toxic therapeutic options. METHODS: We investigated retroviral WAS protein (WASP) gene transfer to assess functional correction and potential toxicities in human CD34(+) cells from WAS patients and healthy individuals, respectively. RESULTS: WASP mRNA and protein levels were restored in CD14(+) cells derived from WASP-transduced hematopoietic stem cells. Functional reconstitution in WASP-transduced myeloid cells was documented by podosome formation and Fc gamma R-mediated phagocytosis. Importantly, overexpression of WASP in CD34(+) cells from healthy donors did not cause any discernible toxic effects. CONCLUSIONS: Our studies document the feasibility of WASP gene transfer into human CD34(+) cells and suggest that the phenotype of WASP-deficient myeloid cells can be restored upon retroviral gene transfer.