Kinetics of lentiviral vector transduction in human CD34+ cells
Human hematopoietic stem cells (HSCs) are refractory to the lentiviral vector transduction. Improvement of transduction efficiency for human HSCs remains crucial for further development of gene therapy especially for non-immunodeficiency diseases. In this report, the authors investigated which step(s) could be at stake, internalization, reverse transcription, nuclear transport or integration. In this purpose, they evaluated the kinetics of lentiviral transduction in human CD34+ cells. After transduction step, the vector RNA amounts were evaluated in Hela versus CD34+ cells. They observed that similar amounts of vector RNA (RNAv) can enter in the two types of cells. However, the timing of the conversion of the RNAv to DNA is different. Indeed, in Hela cells, the amount of RNAv rapidly decreases in favor of DNA vector forms while, in CD34+, the amount of RNAv decreases slowly and a very low level of DNA vector is detected. They conclude that the initiation of reverse transcription is a major limiting step in lentiviral transduction for human CD34+ cells.
To enhance human CD34+ cells transduction, one solution could be the use of lentiviral vectors lacking of reverse transcription step. The last generation of GEG Tech lentiviral vectors is. Indeed, Lenti-ONE Trans vectors are mutants of reverse transcriptase, so they are taken in charge by the cells such as a classical mRNA and are not dependent of the reverse transcriptase step. They induce a full transient expression which could be very useful for genome editing tools or transient therapeutic factors. Furthermore, the expression of this type of vector could be prolonged by repeat transduction steps
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