Variable Transduction Efficiency of Murine Leukemia Retroviral Vector on Mammalian Cells: Role of Cellular Glycosylation

AbstractTo elucidate the cellular tropism of Moloney murine leukemia virus (MuLV), we have studied the transduction efficiency of a recombinant MuLV vector carrying the β-galactosidase reporter gene on a variety of rodent cells. Under optimal conditions forin vitrocell transduction, primary cultures of adult rat fibroblasts derived from various organs were very poorly transduced by the ecotropic MuLV vector (0.02–0.12%) when compared to immortalized cells such as the F2408 (42%) and 3Y1 (defined as 100%) lines. Primary cultures of fibroblasts from neonatal (3.7%) or embryonic rat tissues (4.6%) and primary cultures of rat mammary epithelial cells (3–4%) were somewhat more susceptible. Immortalization of rodent fibroblasts with Polyomavirus Large T, SV40 Large T, and E6-E7 genes of human papilloma virus resulted in a modest or minimal increase in transduction efficiency, and introduction of the transforming genes v-Src, v-Ras, and v-Raf was in most instances associated with a decrease in MuLV vector entry. Variability of transduction efficiency was not related to differences in cellular growth rate and treatment of MuLV vectorsin vitrowith deoxyribonucleoside triphosphates and treatment of cells in culture with protease inhibitors failed to modify cellular entry of the MuLV vector. On the other hand, inhibition of cellular glycosylation with swansonine, 1-deoxymannojirimycin and, primarily, tunicamycin enhanced entry of the ecotropic vector by up to 220-fold, particularly into cells which were otherwise highly resistant. These findings demonstrate major differences in transduction efficiency of the ecotropic MuLV vector on rodent cells and indicate that cellular glycosylation plays a critical role in determining MuLV cellular tropism