Quiescent lymphocytes gene transfer with measles virus glycoprotein-pseudotyped lentiviral vectors requires binding to SLAM and CD46 receptors

Abstract

Lentiviral transduction of quiescent lymphocytes is key for gene therapy. However, transduction with classical VSVG- pseudotyped LVs needs at least cell cycle entry to occur. We generated lentiviral vectors pseudotyped with measles virus glycoproteins (MV-LVs) that showed to be independent of the cell cycle status therefore allowing efficient and stable trans- duction of G0/G1a T and B cells with the bonus of maintaining their quiescent state. Since MV-LVs recognizes CD46 and SLAM molecules on the target cells? membrane we looked into the roles of each of these receptors on the transduction process. LVs that recognized only SLAM or CD46 receptors did not result in stable transduction of resting lymphocytes. Looking in depth, CD46- tropic vectors accomplished vector-cell binding, fusion, and reverse transcription but no provirus integration while SLAM- tropic vectors were blocked already at the level of fusion. Im- portantly, efficient and stable transduction of quiescent T and B cells only occurred when both CD46 and SLAM binding sites were present in cis in the MV-hemagglutinin envelope glyco- protein. In addition, the way of entry of MV-LVs appears to be crucial for the efficient transduction observed and strongly re- sembles macropinocytosis. Taken together we propose that vec- tor entry and reverse transcription can already occur through CD46 receptor but SLAM binding and signalling is absolutely required to ultimately achieve successful integration and stable transduction of quiescent lymphocytes.