A soluble CAR-SCF fusion protein improves adenoviral vector-mediated gene transferto c-Kit-positive hematopoietic cells

Background Although adenoviral vectors primarily derived from the adenovirus serotype 5 (Ad5) are widely used for many gene transfer applications, they cannot efficiently infect hematopoietic cells, since these cells do not express the coxsackie‐adenoviral receptor (CAR). Methods We have developed a soluble fusion protein that bridges adenoviral fibers and the c‐Kit receptor to alter Ad5 tropism to immature hematopoietic cells. The CAR‐SCF fusion protein consists of the extracellular domains of CAR and stem cell factor (SCF). The human megakaryoblastic leukemia cell lines UT‐7 and M07e, human chronic myelogenous leukemia cell line K‐562, and erythroleukemia cell line TF‐1 were used to assess CAR‐SCF‐assisted Ad5‐mediated gene transfer. Hematopoietic cell lines were infected with an Ad5 vector (Ad5‐eGFP) or a fiber‐mutant Ad5/F35 (Ad5/F35‐eGFP) expressing the enhanced green fluorescent protein gene in the presence or absence of CAR‐SCF. Results Twenty‐four hours after infection, more than 80% of M07e cells infected in the presence of CAR‐SCF were eGFP‐positive, compared with very few eGFP‐positive cells following Ad5‐eGFP infection in the absence of CAR‐SCF. The enhancement of Ad5‐eGFP infection by CAR‐SCF was greater than that caused by Ad5/F35‐eGFP (50%). The ability of CAR‐SCF to enhance Ad5‐eGFP infectivity was highly dependent on cellular c‐Kit expression levels. Furthermore, CAR‐SCF also enhanced Ad5‐mediated gene transfer into human primary CD34+ cells. Conclusions The CAR‐SCF fusion protein assists Ad5‐mediated transduction to c‐Kit+ CAR− hematopoietic cells. The use of this fusion protein would enhance a utility of Ad5‐mediated hematopoietic cell transduction strategies. Copyright © 2003 John Wiley & Sons, Ltd.