Differential Effects of Strategies to Improve the Transduction Efficiency of Lentiviral Vector that Conveys an Anti-HIV Protein, Nullbasic, in Human T Cells.

Nullbasic is a mutant form of HIV-1 Tat that has strong ability to protect cells from HIV-1 replication by inhibiting three different steps of viral replication: reverse transcription, Rev export of viral mRNA from the nucleus to the cytoplasm and transcription of viral mRNA by RNA polymerase II. We previously showed that Nullbasic inhibits transduction of human cells including T cells by HIV-1-based lentiviral vectors. Here we investigated whether the Nullbasic antagonists huTat2 (a Tat targeting intrabody), HIV-1 Tat or Rev proteins or cellular DDX1 protein could improve transduction by a HIV-1 lentiviral vector conveying Nullbasic-ZsGreen1 to human T cells. We show that overexpression of huTat2, Tat-FLAG and DDX1-HA in virus-like particle (VLP) producer cells significantly improved transduction efficiency of VLPs that convey Nullbasic in Jurkat cells. Specifically, co-expression of Tat-FLAG and DDX1-HA in the VLP producer cell improved transduction efficiency better than if used individually. Transduction efficiencies could be further improved by including a spinoculation step. However, the same optimised protocol and using the same VLPs failed to transduce primary human CD4+ T cells. The results imply that the effects of Nullbasic on VLPs on early HIV-1 replication are robust in human CD4+ T cells. Given this significant block to lentiviral vector transduction by Nullbasic in primary CD4+ T cells, our data indicate that gammaretroviral, but not lentiviral, vectors are suitable for delivering Nullbasic to primary human T cells.