Lentivirus Vector Mediated Hematopoietic Stem Cell Gene Transfer of Common Gamma-Chain Cytokine Receptor in Rhesus Macaques

We examined the efficiency of marking, gene expression, and transplant of bone marrow and peripheral blood CD34 ＋cells using a lentivirus vector in non-human primate model systems. In vitrocytokine stimulation was not required to achieve efficient transduction of CD34 ＋cells resulting in marking and gene expression of the reporter gene encoding enhanced green fluorescent protein (EGFP) following transplant of the CD34 ＋cells. Monkeys transplanted with mobilized peripheral blood CD34 ＋cells resulted in EGFP expression in 1 to 10% of multilineage peripheral blood cells, including red blood cells and platelets, stable for 5 years to date. The relative level of gene expression utilizing a lentiviral vector bearing a RhMLV promoter is 2- to 10-fold greater than that utilizing a lenntivirus vector bearing the cytomegalovirus immediate-early promoter. In contrast, in animals transplanted with autologous bone mallow CD34 ＋cells, multilineage EGFP expression was evident initially but diminished over time. We further tested our lentivirus vector system by demonstrating gene transfer of the human common gamma-chain cytokine receptor gene (νc), deficient in X-linked SCID patients and recently successfully used to treat disease. Marking was 0.42 and 0.001 HIV-1 vector DNA copy per 100 cells in two animals. To date, all EGFP- and νc-transplanted animals are healthy. This system may prove useful for expression of therapeutic genes in human hematopoientic cells.