Amphotropic and VSV-G-pseudotyped retroviral vectors transduce human hematopoietic progenitor cells with similar...

One restriction of retroviral gene transfer into hematopoietic stem cells is the low level of amphotropic virus receptor. In the present study, we examined whether retroviral vectors pseudotyped with the G-protein of vesicular stomatitis virus (VSV) can overcome this restriction. Human progenitor cells purified by magnetic beads and cell sorting were transduced with an amphotropic or VSV-G-pseudotyped retroviral vector containing the truncated human nerve growth factor receptor as a marker gene. Cells were prestimulated with flt-3 ligand, stem cell factor, and interleukin-3 and transduced on fibronectin. Marker gene expression was analyzed by flow cytometry. Transduction efficiencies of amphotropic and VSV-G-pseudotyped virus for CD34+ cells did not differ significantly. Gene transfer into CD34+CD38- cells, which are enriched in more immature progenitors, was not restricted and transfer efficiencies for this subset were also similar for both pseudotypes. The addition of fibronectin improved gene transfer with the amphotropic vector considerably (5- to 19.3-fold, mean 12.6), while the effect on the VSV-G-pseudotype was far less pronounced (1- to 3.9-fold, mean 2.1, P = 0.04). In conclusion, high levels of gene transfer to human hematopoietic progenitors were achieved with an optimized transduction protocol, and transduction efficiencies could not be improved further by the use of VSV-G-pseudotypes.