ANALYSIS IN HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 VECTORS OF CIS-ACTINGSEQUENCES THAT AFFECT GENE-TRANSFER INTO HUMAN-LYMPHOCYTES

Human immunodeficiency virus type 1 (HIV-1) can be used to generate re combinant viral vectors far delivery of heterologous genes to human CD 4-positive lymphocytes. To define the cis-acting sequences required fo r efficient gene transfer, a number of HIV-1 vectors containing a prev iously identified packaging signal, long terminal repeats. and additio nal gag, pol, and env viral sequences were designed. By providing the viral proteins in trans, recombinant viruses were generated and analyz ed for their abilities to transfer genes into human T lymphocytes. Inc lusion of up to 653 nucleotides derived from the 5' end of the gag gen e in the vector improved the efficiency of gene transfer, but inclusio n of additional gag or pol sequences did net further improve this effi ciency. The increased efficiency of gene transfer associated with the inclusion of 5' gag sequences in the vector arose, at least in part, f rom an increase in the packaging of vector RNA. The presence of the Re v-responsive element (RRE) increased the efficiency of transfer of vec tors containing significant lengths of gag sequence, as expected from the Rev requirement for nucleus-to-cytoplasm transport of unspliced ve ctor RNA containing intact packaging signals. However, the presence of a RRE did not affect the transfer efficiency of smaller vectors lacki ng significant lengths of gag sequences, arguing against a specific ro le for the RRE in packaging or vector transfer. These results contribu te to an understanding of the minimal cis-acting sequences that operat e in the contest of HIV-1 vectors for delivering genes into human lymp hocytes.