Gene transfer by lentiviral vectors is limited by nuclear translocation and rescued by HIV-1 pol sequences

Gene-transfer vectors based on lentiviruses are distinguished by their abil ity to transduce non-dividing cells(1,2). The HIV-1 proteins Matrix, Vpr an d Integrase have been implicated in the nuclear import of the viral genome in non-dividing cells(3-5). Here we show that a sequence within polis also required in cis. It contains structural elements previously associated with the progress of reverse transcription in target cells(6-9). We restored th ese elements in cis within late-generation lentiviral vectors(10,11). The n ew vector transduced to a much higher efficiency several types of human pri mary cells, when both growing and growth-arrested, including haematopoietic stem cells assayed by longterm repopulation of NOD/SCID mice. On in vivo a dministration into SCID mice, the vector induced higher plasma levels of hu man clotting factor IX (F.IX) than non-modified vector. Our results indicat e that nuclear translocation of the genome is a rate-limiting step in lenti viral infection of both dividing and non-dividing cells, and that it depend s on protein and nucleic acid sequence determinants. Full rescue of this st ep in lentivirus-based vectors improves performance for gene-therapy applic ations.