Integration efficiency of a hybrid adenoretroviral vector

The frequency with which the hybrid vector AdLTR-luc mediates genomic integration [Nat. Biotech. 18 (2000) 176–180] is unknown. To address this, we constructed AdLTR-red, using the AdLTR-luc backbone and the enhanced red fluorescence protein cDNA. Kinetic studies showed that AdLTR-red and a conventional adenoviral vector, AdCMV-red, entered and transduced epithelial cells comparably. AdLTR-red integration frequency in vitro, i.e., the percentage of red clones after 10–12 doubling times from limiting dilutions, was 8.0% (36/450; at 67 particles/cell). With AdCMV-red, 0/549 clones were integration-positive. Seven days after AdLTR-luc or AdCMV-luc (<f>1011</f> particles) femoral vein administration to adult rats splenocytes were prepared, stimulated with concanavalin A, and examined by FISH. AdLTR-luc integration occurred in 5–11% of mitotic rat splenocytes, while no unequivocal integration was found with AdCMV-luc. These data provide the first quantitative evidence of the frequency for genomic integration with this hybrid vector. [Copyright &y& Elsevier]