Poly-L-lysine-based molecular conjugate vectors: A high efficiency gene transfer system for human progenitor and leukemia cells

Background: Targeted, specific receptor mediated gene transfer is a major g oal of gene therapy research to accomplish gene transfer exclusively to the desired cell population. Methods: First, the use of natural receptor for s tem cell factor and transferrin receptor-targeted gene transfer using poly- L-lysine-based molecular conjugate vectors was evaluated in a panel of hema topoietic progenitor cell lines. Second, the ability of poly-L-lysine to en hance adenovirus mediated gene transfer efficiency was examined in differen t cell lines by using recombinant adenovirus-poly-L-lysine molecular conjug ate conglomerates (recMCVEGFP). Results: Despite effective ligand internali zation receptor, gene expression amplification in receptor positive cell li nes was not uniformly observed. Therefore, using a poly-L-lysine-based, rec eptor-targeted vector, neither transferrin nor natural receptor for stem ce ll factor mediated gene transfer can be considered a universally applicable procedure that exclusively depends on the presence of receptors on the cel l surface; rather, it is a cell specific phenomenon. In our model, poly-L-l ysine is the major contributor for gene transfer to hematopoietic progenito r cells, mediating the initial vector-cell binding. Human progenitor cell l ines are poorly transduceable with recombinant adenovirus vectors. This new poly-L-lysine-modified, adenovirus-based vector could overcome virus tropi sm restrictions and consistently achieve very high transduction efficiency (>90%) in cells otherwise refractory to adenovirus gene transfer. Conclusio ns: Polylysine-based adenovirus vectors may have promise for situations in which high-efficiency gene transfer with transient high level transgene exp ression in hematopoietic cells is needed, such as leukemia vaccine protocol s or for purging strategies in leukemia cell contaminated stem cell prepara tions.