Novel Tat-encoding bicistronic human immunodeficiency virus type 1-based gene transfer vectors for high-level transgene expression.

We describe bicistronic single-exon Tat (72-amino-acid Tat [Tat72])- and full-length Tat (Tat86)-encoding gene transfer vectors based on human immunodeficiency virus type 1 (HIV-1). We created versions of these vectors that were rendered Rev independent by using the constitutive transport element (CTE) from Mason-Pfizer monkey virus (MPMV). Tat72-encoding vectors performed better than Tat86-expressing vectors in gene transfer experiments. CTE-containing vectors, produced in a Rev-independent packaging system, had gene transfer efficiencies nearly equivalent to those produced using a combination RNA transport (CTE and Rev-Rev response element)-based packaging system. The Tat72-encoding vectors could be efficiently transduced into a variety of cell types, showed higher levels of transgene expression than vectors with the simian cytomegalovirus immediate-early or the simian virus 40 early promoter, and provide an alternative to HIV-1 vectors with internal promoters.