Efficient Transduction of Human Hematopoietic Cells with the Human Multidrug Resistance Gene 1 via SV40 Pseudovirions

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Abstract
Transduction of MDR1 may be of use in chemoprotection of normal bone marrow (BM) cells during treatment of malignancies, or as a selectable marker for the transfer of other genes into the BM, a critical target for the cure of many diseases. To that aim, the human multidrug resistance gene MDR1 was cloned into an SV40 pseudoviral vector containing the SV40 origin of replication (ori) and encapsidation signal (ses), and the plasmid was encapsidated in COS cells as SV40/MDR1 pseudovirions. Expression of the human MDR1 gene was demonstrated in murine MEL cells infected with SV40/MDR1 pseudovirions, using a monoclonal antibody (MPK16) specific for the human 170-kD P-glycoprotein. Functional P-glycoprotein was demonstrated by resistance to colchicine in NIH-3T3 cells infected with SV40/MDR1 pseudovirions. Activity of P-glycoprotein was assayed by rhodamine-123 dye exclusion and fluorescence-activated cell sorter analysis (FACS) in various cell types including hematopoietic cells. Highly efficient gene transfer and expression was demonstrated in all murine and human cell types tested, including primary human BM cells. Using multiplicities of infection (moi) of 1–2, over 95% of cells were found to become MDR1+. The percent of MDR1+ cells was proportional to the moi. We conclude that the SV40 pseudoviral vector is efficient for gene transmission into human hematopoietic cells. SV40 is an attractive potential vector with high-efficiency gene transfer into a wide variety of human tissues, including the bone marrow. Introducing the human MDR1 gene into hematopoietic progenitor cells has been recently attempted to reduce the toxicity caused by anticancer drugs in patients undergoing chemotherapy. Here we demonstrate the use of SV40 pseudovirions to transfer a functional human MDR1 gene into human bone marrow cells. The experiments demonstrated highly efficient gene transfer and significant expression. These studies, in parallel with the development of an in vitro packaging system for SV40 pseudovirions, suggest the feasibility of using the SV40/MDR1 pseudovirion delivery system for chemotherapy protection. This system is also potentially valuable for delivering other therapeutic genes into hematopoietic cells, a critical target for the treatment of many diseases.