Minimum requirements for efficient transduction of dividing and nondividing cells by feline immunodeficiency virus vectors

The development of gene delivery vectors based on feline immunodeficiency v irus (FIV) is an attractive alternative to vectors based on primate sources for the delivery of genes into humans. To investigate the requirements for efficient transduction of dividing and nondividing cells by vector particl es based on FIV, a series of packaging and vector constructs was generated for which viral gene expression was minimized and from which unnecessary ci s-acting sequences were deleted. Pseudotyped vector particles produced in 2 93T cells were used to transduce various target cells, including contact-in hibited human skin fibroblasts and growth-arrested HT1080 cells. FIV vector s in which the U3 promoter was replaced with the cytomegalovirus promoter g ave rise to over 50-fold-higher titers than FIV vectors containing the comp lete FIV 5' long terminal repeat (LTR). Comparison of the transduction effi ciencies of vectors containing different portions of the FIV Gag coding reg ion indicates that at least a functional part of the PTV packaging signal ( Psi) is located within an area which includes the 5' LTR and the first 350 bp of gag. Transduction efficiencies of vectors prepared without PN vif and orf2 accessory gene expression did not differ substantially from those of vectors prepared with accessory gene expression in either dividing or nondi viding cells. The requirement for FIV rev-RRE was, however, demonstrated by the inefficient production of vector particles in the absence of rev expre ssion. Together, these results demonstrate the efficient transduction of no ndividing cells in vitro by a multiply attenuated FIV vector and contribute to an understanding of the minimum requirements for efficient vector produ ction and infectivity. In addition, we describe the ability of an FIV vecto r to deliver genes in vivo into hamster muscle tissue.