The peripheral blood has been established as a source of hematopoietic stem cells, providing an alternative source to bone marrow for hematopoietic reconstitution of patients with oncologic, hematologic, and genetic diseases. Although apheresis is less efficient than bone marrow harvesting for collection of large numbers of CD34+ (a marker of early hematopoietic precursors) cells, apheresis is less traumatic, requires no anesthesia and can be performed more frequently than bone marrow harvesting. The purpose of this preclinical research project is to investigate the use of hematopoietic stem cells mobilized into peripheral blood as targets for retroviral-mediated gene therapy, to compare the efficiency of transduction of primitive cells with the lentiviral and foamy viral vector systems and to evaluate the ability to expand those stem cells ex vivo using hematopoietic growth factors (cytokines). Research participants in this study will be healthy adult volunteers.