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Plerixafor+G-CSF-mobilized CD34+ cells represent an optimal graft source for thalassemia gene therapy

Garyfalia Karponi, Nikoletta Psatha, Carsten Werner Lederer, Jennifer Eileen Adair, Fani Zervou, Nikolaos Zogas, Marina Kleanthous, Constantinos Tsatalas, Achilles Anagnostopoulos, Michel Sadelain, Isabelle Rivière, George Stamatoyannopoulos and Evangelia Yannaki

Key points

  • Effective gene correction and long-term engraftment of human thalassemic CD34+ cells, mobilized with different strategies.

  • Plerixafor+G-CSF-mobilized CD34+ cells produce higher β-globin/VCN and superior early engraftment over single-agent-mobilized cells.

Abstract

Globin gene therapy requires abundant numbers of highly engraftable, autologous hematopoietic stem cells expressing curative levels of β-globin upon differentiation. In this study, CD34+ cells from 31 thalassemic patients mobilized with Hydroxyurea+G-CSF, G-CSF, Plerixafor or Plerixafor+G-CSF were transduced with the TNS9.3.55 β-globin lentivector and compared for transducibility and globin expression in vitro, as well as engraftment potential in a xenogeneic model after partial myeloablation. Transduction efficiency and vector copy number (VCN) averaged 48.4%±2.8 and 1.91±0.04 respectively, while expression approximated the one-copy normal β-globin output. Plerixafor+G-CSF-cells produced the highest β-globin expression/VCN. Long-term multilineage engraftment and persistent VCN and vector expression was encountered in all xenografted groups, with Plerixafor+G-CSF-mobilized cells achieving superior short-term engraftment rates, with similar numbers of CD34+ cells transplanted. Overall, Plerixafor+G-CSF not only allows high CD34+ cell yields, but also provides increased β-globin expression/VCN and enhanced early human chimerism under non-myeloablative conditions, thus representing an optimal graft for thalassemia gene therapy.

  • Submitted March 10, 2015.
  • Accepted June 8, 2015.