Introduction: Nullbasic is a derivative of the HIV-1 transcriptional activator protein, Tat. We have shown that Nullbasic is a nontoxic first-in-class antiviral agent that inhibits HIV production and viral spread in human T cells. We hypothesised that the stable expression of Nullbasic not only can inhibit HIV production in Jurkat cells but also can supress HIV-1 production in chronically infected Jurkat cells.
Methods: Nullbasic.Zsgreen (NB.ZsG) was delivered to Jurkat cells with a lentiviral vector pSicoR-EF1a that expresses NB.ZsG from a constitutively driven EF1a promoter. Positive cells were selected by a cell sorter. Then 1) Jurkat.NB.ZsG cells were infected with HIV-1 at 20 ng/105 cells. 2) HIV-1 infected Jurkat.NB.ZsG were stimulated with 1 nM PMA. 3) Co-culturing experiments were performed to check any progeny virus made by Jurkat.NB.ZsG cells can spread to other cells. 4) NB.ZsG VLPs were used to treat HIV-1 chronically infected Jurkat cells. NB.ZsG expression was monitored by FACS and Western blot. HIV-I level was measured by p24 ELISA assay. HIV gene expression was measured by RT- PCR.
Results: No HIV-1 replication was detected in the infected Jurkat.NB.ZsG cells. However, HIV-1 DNA was detected suggesting that the cells harboured proviral DNA. The proviral DNA could not be stimulated by PMA (1nM). Co-culture of infected Jukat.NB.ZsG cells with uninfected Jurkat cells failed to rescue HIV-1 replication. Finally, NB can strongly supress HIV-1 production in the HIV-1 chronically infected Jurkat cells. RT-PCR revealed that HIV mRNA level in NB.ZsG-treated cells dropped by 150-800 folds compared to the control cells. Interestingly, PMA could not fully reactivated the HIV-1 production in the treated cells. ChIP assay indicated that NB significantly inhibits HIV gene expression by preventing RNA polymerase II from binding to LTR promoter.
Conclusions: The results suggest that Nullbasic induces a latency-like effect, which could not be fully reactivated with PMA. NB strongly inhibit HIV-1 gene expression in by preventing RNA polymerase II from binding to LTR promoter.Therefore, Nullbasic is a potent candidate anti-HIV-1 therapy.