Retroviral Particles Produced from a Stable Human-Derived Packaging Cell Line Transduce Target Cells with Very High Efficiencies

The goal of this work was to determine whether a stable 293 amphotropic packaging line, which we have designated 293-SPA, is useful for the production of high-titer stable virus by comparison to the murine ΨCRIP line. Here, we report our unexpected findings that particles derived from the 293-SPA line transduce target cells (both NIH-3T3 cells and primary melanoma cells) with greatly enhanced efficiencies (at least 10-fold) compared to particles derived from the ΨCRIP packaging line. We show that the presence of a transferable inhibitor in the ΨCRIP line at least partially accounts for this dramatic difference in transduction efficiency. This work has important implications for improving the efficiency of retrovirus-mediated gene transfer in general as well as in the design of new packaging cell lines. The construction of new packaging cell lines for retroviral vectors that increase the efficiency of gene transduction is an important goal. We have investigated the use of a stable human (293)-based amphotropic packaging cell line (293-SPA) and compared the transduction efficiencies to those obtained with virus derived from the murine ΨCRIP line. Vectors encoding two different marker genes (lacZ and huGM-CSF) were used to measure transduction efficiencies in terms of proviral copies transmitted to target cells as well as gene expression in target cells. We show that the 293-SPA-derived virus transduces target cells more effectively than ΨCRIP derived virus by a minimum of 10-fold. This will be valuable for enhancing the efficiency of retrovirus-mediated gene transfer.