RETROVIRAL TRANSDUCTION OF CD34-ENRICHED HEMATOPOIETIC PROGENITOR CELLS UNDER SERUM-FREE CONDITIONS

The use of defined or serum-free culture conditions during retroviral transduction of hematopoietic cells would be desirable for standardiza tion and safety reasons, as well as potentially allowing greater expan sion of progenitor cells. Retroviral vector supernatants were concentr ated and purified via tangential now filtration polyethylene glycol (P EG)-precipitation, and ultracentrifugation, allowing serum-free transd uctions at standard multiplicities of infection (moil. Protein content of transductions using these concentrated vectors was 5-6 logs lower than in standard transductions. Transduction efficiencies of these con centrated vector preparations added back to serum-free or serum-contai ning media were equivalent to standard retroviral supernatant transduc tions of CD34-enriched progenitors. Absolute progenitor (CFU-C) number s at the end of transduction were higher in serum-free + concentrated virus transductions, as opposed to transductions in standard vector su pernatants containing fetal calf serum.