Lentiviral vectors: design, biological properties, milestones and current major applications, hazards 1

Published on September 3, 2014   58 min

Other Talks in the Category: Cell Biology

0:00
So hello, everybody. This is Luigi Naldini from the San Raffaele-Telethon Institute of Gene Therapy in Milan, Italy. Today we will be discussing properties of retroviral vectors and, in particular, lentiviral vectors.
0:18
The first slide, I'm listing key properties of retroviral vectors in general. First of all, these vectors are capable of integrating the transgene into the genome. So they're very well suitable for stable gene transfer in target cell. Transgene expression can also be stable in long term, but this is not necessarily the case. At least in some situation, you may have the vector gene stable inserted in a cell, but lack of its expression. There is a number or reason why this may happen. In some cases, most of the vector may be silenced, because the cell can recognize viral sequence, most often in the viral long terminal repeat-- so-called LTRs-- and specifically silence that by epigenetic changes. This usually occurs in some cell type-- most often embryonic stem cell. And this usually happens with the gamma retroviral vector, which contains long terminal repeat, which carries sequence which are recognized by this surveillance system. So if you are transducing ES cell, you may want to use a vector which is devoided of those long terminal repeat sequence targeted by the surveillance mechanism. You may use a lentiviral vector, or a vector which has a deletion of those LTR. In other cases, silencing may only affect a fraction of the integration site. This could be a small subset, or a sizable subset. And these are those integration which randomly occur into chromatin being condensed, and so not permissive to transcription; or chromatin, which becomes condensed after that initial transduction. In this case it will be extinction of the O expression. But most of the insertion site could still be open and expressed. So this statement about general stability of expression remains true, although not for every insertion site, but for a majority of them in most of the cases. In term of fidelity of replication retroviral vector are dependent on reverse transcription for the transfer of the genome to target cell. Reverse transcription is highly error-prone so there will be a significant rate of mutation-- up to one in thousand basis In the transduced cell.
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Lentiviral vectors: design, biological properties, milestones and current major applications, hazards 1

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