FIG. 4.

Mobilization of pICUT vectors after one round of transduction into a packaging cell line. The 4070A envelope pseudotyped virus, made by transient transfection of 293T cells, was initially used to transduce the FLYRD18 packaging cell line at a multiplicity of infection of 1. At 48 h posttransduction, the supernatant from these cells was then harvested, and the titers were determined on HT1080 cells. The corresponding primary and secondary titers of the pICUT-2–ZN vector and the control pZN vector were established on HT1080 cells as LFU per milliliter. The primary titers were established from the harvested supernatant taken from transfected 293T cells (shown as black bars) and secondary titers from supernatant harvested from the transduced FLYRD18 cells (shown as white bars). This figure illustrates that while secondary titers for the pZN control remain high, such titers drop 10,000-fold in the pICUT vectors after one round of RT.