Isolation of a Highly Purified HSC-enriched CD34(+)CD90(+)CD45RA(−) Cell Subset for Allogeneic Transplantation in the Nonhuman Primate Large-animal Model

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is a common treatment for patients suffering from different hematological disorders. Allo-HCT in combination with hematopoietic stem cell (HSC) gene therapy is considered a promising treatment option for millions of patients with HIV+ and acute myeloid leukemia. Most currently available HSC gene therapy approaches target CD34-enriched cell fractions, a heterogeneous mix of mostly progenitor cells and only very few HSCs with long-term multilineage engraftment potential. As a consequence, gene therapy approaches are currently limited in their HSC targeting efficiency, very expensive consuming huge quantities of modifying reagents, and can lead to unwanted side effects in nontarget cells. We have previously shown that purified CD34(+)CD90(+)CD45RA(−) cells are enriched for multipotent HSCs with long-term multilineage engraftment potential, which can reconstitute the entire hematopoietic system in an autologous nonhuman primate transplant model. Here, we tested the feasibility of transplantation with purified CD34(+)CD90(+)CD45RA(−) cells in the allogeneic setting in a nonhuman primate model. METHODS. To evaluate the feasibility of this approach, CD34(+)CD90(+)CD45RA(−) cells from 2 fully major histocompatibility complex-matched, full sibling rhesus macaques were sort-purified, quality controlled, and transplanted. Engraftment and donor chimerism were evaluated in the peripheral blood and bone marrow of both animals. RESULTS. Despite limited survival due to infectious complications, we show that the large-scale sort-purification and transplantation of CD34(+)CD90(+)CD45RA(−) cells is technically feasible and leads to rapid engraftment of cells in bone marrow in the allogeneic setting and absence of cotransferred T cells. CONCLUSIONS. We show that purification of an HSC-enriched CD34(+) subset can serve as a potential stem cell source for allo-HCTs. Most importantly, the combination of allo-HCT and HSC gene therapy has the potential to treat a wide array of hematologic and nonhematologic disorders.