Long-Term Expression of Retroviral-Transduced Adenosine Deaminase in Human Primitive Hematopoietic Progenitors

Abstract

Adenosine deaminase (ADA) deficiency, a rare autosomal recessive disorder, is an ideal candidate for gene replacement therapy. By means of co-cultivation with a retroviral vector-producing cell line, we have demonstrated efficient transfer and expression of the human ADA gene into human primitive hematopoietic progenitors. At 6 weeks post-transduction in myeloid long-term bone marrow culture, approximately 50% of the clonogenic progenitors were transduced by the provirus, with ADA expression detected in 30% of transduced colonies. The ADA activity increased by 3.7-fold in the nonadherent fraction of transduced bone marrow after 9 weeks. We have also achieved efficient transduction by retroviral supernatant of normal and ADA-deficient bone marrow cells that were allowed to establish a stromal layer in long-term culture, indicating the feasibility of proceeding with attempts to perform stem cell gene therapy on patients with ADA deficiency.

Overview summary

Sustained expression of a gene by a retroviral vector is one of the most critical issues for human gene therapy, although it is not yet clear which enhancer/promoter system is suitable for human bone marrow stem cells. Mitani et al. have shown that the long terminal repeat of Molony murine leukemia virus remains active after being transferred into human primitive hematopoieitc progenitors. They also developed a modified viral supernatant transduction protocol that achieves gene transfer into human primitive hematopoietic progenitors with an equivalent efficiency to the co-cultivation procedure.