EFFECT OF CHLOROQUINE ON TRANSDUCTION OF CELL LINES AND BABOON CD34 CELLS BY A GALV PSEUDOTYPED RETROVIRUS

Background . Chloroquine is an amine that inhibits lysosomal enzymes and is increasingly being used for increasing the rate of transfection of cells during gene transfer. Its effects on retrovirus-mediated gene transfer (transduction) are not clearly evident. Here, we studied the effects of this drug on transduction efficiency in a variety of cell lines and in hematopoietic cells. Methods . We used a GALV pseudotyped retrovirus (PG13/ MNDEGFPSN) for transduction of the cell lines Hela, 208F, K562 and HL60, and baboon column-bead selected CD34+ cells using different methods, and in the presence of different concentrations of chloroquine. Transduction was gauged by detection of cells producing green fluorescence in a flow cytometer. Results . Chloroquine (100 µmol) reduced transduction efficiency in cell lines, with some concomitant increase in propidum iodide positivity, which is an indicator of toxicity. This reduction in transduction efficiency remained in the generations of cells, even after the disappearance of conditions causing cellular toxicity. In baboon CD34+ cells, its effects were variable, but it did not increase the cellular toxicity. Increased transduction efficiency was observed in the presence of chloroquine (13.02 ± 0.5% in the absence of chloroquine versus that in the presence of 50 µmol (28.84 ± 2.71%) and 100 µmol (28.76 ± 2.12%) of chloroquine). In other experiments, chloroquine increased PI positivity of the baboon cells and decreased transduction efficiency (19.09 ± 0.61% and 17.99 ± 0.22% without chloroquine in second and third experiments, respectively). Conclusion . Although chloroquine inhibited transduction efficiency in cell lines, it had the opposite effect on baboon CD34+ cells and may actually increased transduction to these cells.