Rational development of a HIV-1 gene therapy vector.

Abstract

HIV-1 provides an attractive option as the basis for gene transfer vectors due to its ability to stably transduce non-cycling cell populations. In order to fully utilise the promise of HIV-1 as a vector it is important that the effects of viral cis sequence elements on vector function are carefully delineated. In this study we have systematically evaluated the effect of various cis elements from the HIV-1 YU-2 genome that have been implicated as either affecting vector performance, or HIV-1 replication, on the efficiency of vector production (titre and infectivity). As a measure of the relative safety of vectors their propensity to inadvertently transfer the gagpol gene to transduced cells was assessed. Sequences that were found to increase vector titre were from the 5' end of the gag gene, from the 5' and 3' ends of the env gene, from immediately upstream of the polypurine tract, and the central polypurine tract. The substitution of the HIV-1 RRE with heterologous RNA transport elements, or the deletion of the RRE, resulted in greatly reduced vector titres. RNA analysis suggested that the role of the Rev/RRE system extends beyond simply acting as an RNA nuclear export signal. The relative safety of different vector designs was compared and an optimal construct selected. Based on our results we have constructed a vector that is both more efficient, and has better safety characteristics, than the widely used pHR' HIV-1 vector construct.