Sort-purification of human CD34+CD90+ cells reduces target cell population and improves lentiviral transduction

ABSTRACTHematopoietic stem cell (HSC) gene therapy has the potential to cure many genetic, malignant and infectious diseases. We have shown in a nonhuman primate (NHP) HSC gene therapy and transplantation model that the CD34+CD90+ cell fraction was exclusively responsible for multilineage engraftment and hematopoietic reconstitution. Here we show the translational potential of this HSC-enriched CD34 subset for lentivirus-mediated gene therapy. Alternative HSC-enrichment strategies include the purification of CD133+ cells or CD38low/- subsets of CD34+ cells from human blood products. We directly compared these strategies to the isolation of CD90+ cells using a GMP-grade flow-sorting protocol with clinical applicability. We show that CD90+ cell selection results in 40-fold fewer target cells in comparison to CD133+ or CD38low/- CD34 subsets without compromising the engraftment potential in vivo. Single cell RNA sequencing confirmed nearly complete depletion of lineage committed progenitor cells in CD90+ fractions compared to alternative selections. Importantly, lentiviral transduction efficiency in purified CD90+ cells resulted in up to 3-fold higher levels of engrafted gene-modified blood cells. These studies should have important implications for the manufacturing of patient-specific HSC gene therapy and genome editing products.