Adeno-associated virus 2-mediated transduction and erythroid lineage-restricted long-term expression of the human β-globin gene in hematopoietic cells from homozygous β-thalassemic mice

Adeno-associated virus 2 (AAV), a nonpathogenic human parvovirus, has gained attention as a potentially useful vector for human gene therapy. Here, we report successful AAV-mediated stable transduction and high-efficiency, long-term, erythroid lineage-restricted expression of a human beta -globin gene in primary murine hematopoietic stem cells in vivo. Bone marrow-derived primitive Sca-1(+), lin(-) hematopoietic stem cells from homozygous beta -thalassemic mice were transduced ex vivo with a recombinant AAV vector containing a normal human beta -globin gene followed by transplantation into low-dose-irradiated B6.c-kitW(41/41) anemic recipient mice. Six months posttransplantation, tail-vein blood samples were analyzed by PCR amplification to document the presence of the transduced human p-globin gene sequences in the peripheral blood cells. Semiquantitative PCR analyses revealed that the transduced human beta -globin gene sequences were present at similar to1 copy per cell. The efficiency of the human beta -globin gene expression was determined to be up to 35% compared with the murine endogenous beta -globin gene by semiquantitative RT-PCR analyses. Peripheral blood samples from several positive recipient mice obtained 10 months posttransplantation were fractionated to obtain enriched populations of granulocytes, lymphocytes, and erythroid cells. PCR analyses revealed the presence of the human beta -globin gene sequences in granulocytes and lymphocytes, indicating multilineage reconstitution. However, only the erythroid population was positive following RT-PCR analyses, suggesting lineage-restricted expression of the transduced human beta -globin gene. Southern blot analyses of total genomic DNA samples isolated from bone marrow cells from transplanted mice also documented proviral integration. These results provide further support for the potential use of recombinant AAV vectors in gene therapy of beta -thalassemia and sickle-cell disease.