Gene therapy of AIDS: a novel approach combining anti HIV-1 siRNAs and a fusion inhibitor

Background: Gene therapy holds considerable promise for the functional cure of HIV-1 infection and, in this context, combinatorial approaches, aimed at interfering with different steps of viral replication, represent powerful strategies. To this end, we previously developed a series of self-inactivating lentiviral vectors expressing multiple small interfering (si)-RNAs targeting the CCR5 cellular gene as well as vif and tat/rev viral transcripts, under the control of different RNA polymerase III promoters (U6, 7SK, H1). The use of a single RNA polymerase III promoter driving the expression of a sequence giving rise to three siRNAs directed against the selected targets (e-shRNA) was also investigated. We identified two effective anti HIV combinatorial vectors that conferred protection against R5 and X4 tropic viruses in human primary CD4+ T lymphocytes. Methods: In the present study, these two vectors were further modified by the inclusion of a membrane-anchored peptide (maC46), which has been shown to efficiently block the entry of both CXCR-4 and CCR5 using viruses. The maC46 was inserted under the transcriptional control of the human Elongation Factor 1 promoter. Additionally, an optimized version of the Woodchuck hepatitis virus post-transcriptional regulatory element (WPRE*) was also inserted in the new generation of lentiviral vectors. The antiviral activity of the optimized vectors was assessed in different cellular models. Results: The developed vectors conferred to the transduced cells a sustained and significant protection against HIV-1 challenge. Conclusion: Overall our results contribute to gain further insights in the design of combinatorial gene therapy approaches against HIV-1 for clinical application.