In Vivo Suppression of HIV Rebound by Didehydro-Cortistatin A, a "Block-and-Lock" Strategy for HIV-1 Treatment

HIV-1 Tat activates viral transcription and limited Tat transactivation correlates with latency establishment. We postulated a "block-and-lock" functional cure approach based on properties of the Tat inhibitor didehydro-Cortistatin A (dCA). HIV-1 transcriptional inhibitors could block ongoing viremia during antiretroviral therapy (ART), locking the HIV promoter in persistent latency. We investigated this hypothesis in human CD4⁺ T cells isolated from aviremic individuals. Combining dCA with ART accelerates HIV-1 suppression and prevents viral rebound after treatment interruption, even during strong cellular activation. We show that dCA mediates epigenetic silencing by increasing nucleosomal occupancy at Nucleosome-1, restricting RNAPII recruitment to the HIV-1 promoter. The efficacy of dCA was studied in the bone marrow-liver-thymus (BLT) mouse model of HIV latency and persistence. Adding dCA to ART-suppressed mice systemically reduces viral mRNA in tissues. Moreover, dCA significantly delays and reduces viral rebound levels upon treatment interruption. Altogether, this work demonstrates the potential of block-and-lock cure strategies.

Didehydro-Cortistatin A: a new player in HIV-therapy?

Antiretroviral therapy can effectively suppress HIV-1 infection but is ineffective against integrated proviruses. A latent viral reservoir composed of latently infected CD4(+)T cells persists under suppressive therapy, and infected individuals must remain indefinitely on antiretroviral therapy to prevent viral reactivation and propagation. Despite therapy, some degree of low-level ongoing replication is detected and transient viral reactivation may replenish the latent reservoir. An analog of the natural compound, Cortistatin A, blocks HIV-1 transcription by specifically targeting the viral transactivator, Tat. Treatment of latently infected cells with this Tat inhibitor promotes a state of deep-latency from which HIV reactivation capacity is greatly diminished. Here we discuss the use of Tat inhibitors to limit the latent reservoir to achieve a functional cure.