Development of minimal lentivirus vectors derived from simian immunodeficiency virus (SIVmac251) and their use for gene transfer into human dendriticcells

Lentivirus-derived vectors are very promising gene delivery systems since t hey are able to transduce nonproliferating differentiated cells, while muri ne leukemia virus-based vectors can only transduce cycling cells. Here we r eport the construction and characterization of highly efficient minimal vec tors derived from simian immunodeficiency virus (SIVmac251), High-fidelity PCR amplification of DNA fragments was used to generate a minimal SIV vecto r formed from a 5' cytomegalovirus early promoter, the 5' viral sequences u p to the 5' end of gag required for reverse transcription and packaging, th e Rev-responsive element, a gene-expressing cassette, and the 3' long termi nal repeat (LTR), Production of SIV vector particles was achieved by transf ecting 293T cells with the vector DNA and helper constructs coding for the viral genes and the vesicular stomatitis virus glycoprotein G envelope. The se SN vectors were found to have transducing titers reaching 10(7) transduc ing units/ml on HeLa cells and to deliver a gene without transfer of helper functions to target cells, The central polypurine tract can be included in the minimal vector, resulting in a two- to threefold increase in the trans duction titers on dividing or growth-arrested cells. Based on this minimal SIV vector, a sin vector was designed by deleting 151 nucleotides in the 3' LTR U3 region, and this SIV sin vector retained high transduction titers, Furthermore, the minimal SIV vector was efficient at transducing terminally differentiated human CD34(+) cell-derived or monocyte-derived dendritic ce lls (DCs), Results show that up to 40% of human primary DCs can be transduc ed by the SIV vectors, This opens a new perspective in the field of immunot herapy.