Inhibition of HIV Type 1 Replication Using Lentiviral-Mediated Delivery of Mutant tRNA Lys3 A58U

Abstract

In previous studies, we showed that residue A58 of cellular tRNALys3 is necessary for appropriate termination of viral plus-strand strong-stop DNA (+SS DNA), and therefore plays a critical role in the life cycle of HIV-1. We also performed proof-of-principle studies that established that a mutant form of this tRNA primer(tRNA^Lys3A58U, which lacks the M1A58 residue necessary for +SS DNA termination) could inhibit HIV-1 replication. In the present work, we examined whether a third generation lentiviral vector (SIN) could be used to deliver tRNA^Lys3A58U to CEM cells. Using both viral kinetic studies and limiting dilution assays (LDA), we observed significant impairment of HIV-1 replication, up to 3 logs in the LDA, in CEM sublines expressing mutant tRNA^Lys3A58U. No inhibition occurred in cells that either expressed wild-type tRNA^Lys3 or were transduced with empty SIN vector. Further, we observed impairment of viral replication using primary isolates of both HIV-1 and HIV-2 in sublines containing tRNA^Lys3A58U. We also detected "breakthrough" HIV-1 replication in some tRNA^Lys3A58U-expressing cultures. Interestingly, analyzed breakthrough viruses appeared to be both genetically and phenotypically wild type. One possible explanation for virological breakthrough is that it reflects the gradual accumulation of HIV-1 within the infected cell culture, to a level that ultimately exceeds the containment "threshold" conferred by tRNA^Lys3A58U. The fact that HIV-1 does not appear to acquire heritable resistance to tRNA^Lys3A58U-mediated blockade differentiates this antiviral modality from other therapeutic interventions. It also suggests that tRNA-mediated inhibition of viral replication might be a valuable adjunct to other antiviral approaches.