Hit-and-Run Stimulation: a Novel Concept To Reactivate Latent HIV-1 Infection without Cytokine Gene Induction

Current antiretroviral therapy (ART) efficiently controls HIV-1 replication but fails to eradicate the virus. Even after years of successful ART, HIV-1 can conceal itself in a latent state in long-lived CD4+ memory T cells. From this latent reservoir, HIV-1 rebounds during treatment interruptions. Attempts to therapeutically eradicate this viral reservoir have yielded disappointing results. A major problem with previously utilized activating agents is that at the concentrations required for efficient HIV-1 reactivation, these stimuli trigger high-level cytokine gene expression (hypercytokinemia). Therapeutically relevant HIV-1-reactivating agents will have to trigger HIV-1 reactivation without the induction of cytokine expression. We present here a proof-of-principle study showing that this is a possibility. In a high-throughput screening effort, we identified an HIV-1-reactivating protein factor (HRF) secreted by the nonpathogenic bacteriumMassilia timonae . In primary T cells and T-cell lines, HRF triggered a high but nonsustained peak of nuclear factor kappa B (NF-κB) activity. While this short NF-κB peak potently reactivated latent HIV-1 infection, it failed to induce gene expression of several proinflammatory NF-κB-dependent cellular genes, such as those for tumor necrosis factor alpha (TNF-α), interleukin-8 (IL-8), and gamma interferon (IFN-γ). Dissociation of cellular and viral gene induction was achievable, as minimum amounts of Tat protein, synthesized following application of a short NF-κB pulse, triggered HIV-1 transactivation and subsequent self-perpetuated HIV-1 expression. In the absence of such a positive feedback mechanism, cellular gene expression was not sustained, suggesting that strategies modulating the NF-κB activity profile could be used to selectively trigger HIV-1 reactivation.