No evidence of clonal dominance in primates up to 4 years following transplantation of multidrug resistance 1 retrovirally transduced long-term repopulating cells

Previous murine studies have suggested that retroviral multidrug resistance 1 ( MDR1) gene transfer may be associated with a myeloproliferative disorder. Analyses at a clonal level and prolonged long-term follow-up in a model with more direct relevance to human biology were lacking. In this study, we analyzed the contribution of individual CD34selected peripheral blood progenitor cells to long-term rhesus macaque hematopoiesis after transduction with a retroviral vector either expressing the multidrug resistance 1 gene ( HaMDR1 vector) or expressing the neomycin resistance ( NeoR) gene ( G1Na vector). We found a total of 122 contributing clones from 8 weeks up to 4 years after transplantation. One hundred two clones contained the G1Na vector, whereas only 20 clones contained the HaMDR1 vector. Here, we show for the first time realtime polymerase chain reaction based quantification of individual transduced cell clones constituting 0.0008% +/- 0.0003% to 0.0041% +/- 0.00032% of primate peripheral blood cells. No clonal dominance was observed.