Retroviral vectors derived from murine leukemia retrovirus (MuLV) have been widely used for efficient gene transfer to achieve long-term expression of a chosen therapeutic gene in mammLian cells (1). Disadvantages of this vector are the instability and low viral titers generated from packaging cells, low efficiency of gene transfer into human cells, especially in vivo, and the requirement for dividing cells. Some authors have attempted to increase the transduction efficiency by using strategies like low-speed centrifugation of viral supernatant with cells, multiple viral exposures (2), or increasing viral titers by ultracentrifugation (3); they were able to produce an average transduction efficiency of 10–60%. However, all such improvements in transduction efficiency require additional procedures, which are practically inefficient.