High Frequency Cell Surface Expression Of A Foreign Gene Product After Murine Hematopoietic Stem Cell Transduction With A Retroviral Vector
A retroviral vector (pSFF) derived from murine Friend spleen focus forming virus was used to transduce murine hematopoietic stem cells and express a cell surface marker protein, mutated murine prion protein, in vivo after transplantation. To enhance retroviral vector integration in bone marrow cells, mice were treated with 5 - fluorouracil (5- FU) to increase stem cell mitotic activity. The infectivity titer of the vector, pSFF-mPrP-3F4, was determined by a novel assay in which antigen-positive foci of infected cells were detected after replication and spread of the vector in cultures of mixed packaging cell lines. Infection of Sca- 1 + /Lineagene9''low cells with pSFF-mPrP-3F4 resulted in marker protein expression in 40% of the progeny cells after 7 days of culture. Transplantation of marrow cells or sorted Sca- 1 + /Lineagene9'low cells transduced with vector resulted in 3F4- positive mPrP expression in 11-37% of donor-derived peripheral blood leukocytes at two weeks. Although the percentage of 3F4-positive blood cells gradually declined, at 28 weeks 23% of recipient mice still maintained expression of the marker gene. Expression was observed in lymphoid, myeloid and erythroid lineages and was detected in Scal + /Lineagene9_low marrow cells. The multi-lineage, high frequency expression observed suggests that pSFF may have utility in gene therapy directed to hematopoietic stem cells and their differentiated progeny.