Abstract

The failure of highly active antiretroviral therapy (HAART) has been largely responsible for the existence of latent human immunodeficiency virus type 1 (HIV-1) reservoirs. The “shock and kill” strategy was confirmed to reactivate HIV-1 latent reservoirs by latency-reversing agents (LRAs) for accelerated HIV-1 clearance. However, a single LRA might be insufficient to induce HIV-1 reactivation from latency due to the complexity of the multiple signaling regulatory pathways that establish the HIV-1 latent reservoir. Therefore, combinations of LRAs or dual-mechanism LRAs are urgently needed to purge the latent reservoirs. We demonstrate here for the first time that a dual-target inhibitor with a specific suppressive effect on both BRD4 and TIP60, CPI-637, could reactivate latent HIV-1 in vitro by permitting Tat to bind positive transcription elongation factor b (P-TEFb) and assembling Tat-super-elongation complex (SEC) formation. In addition, CPI-637-mediated TIP60 downregulation further stimulated BRD4 dissociation from the HIV-1 long terminal repeat (LTR) promoter, allowing Tat to more effectively bind P-TEFb compared to BRD4 inhibition alone. Much more importantly, CPI-637 exerted a potent synergistic effect but alleviated global T cell activation and blocked viral spread to uninfected bystander CD4+ T cells with minimal cytotoxicity. Our results indicate that CPI-637 opens up the prospect of novel dual-target inhibitors for antagonizing HIV-1 latency and deserves further investigation for development as a promising LRA with a “shock and kill” strategy.

Highlights

  • Highly active antiretroviral therapy (HAART) has dramatically decreased morbidity and mortality in patients infected with human immunodeficiency virus type 1 (HIV-1), a rapid rebound in plasma viremia to pretreatment levels is observed after the interruption of highly active antiretroviral therapy (HAART) treatment (Van Lint et al, 2013)

  • The production of HIV-1 p24 antigen in the supernatants of ACH2 cells in the presence or absence of CPI-637 was detected by Enzyme-Linked Immunosorbent Assay (ELISA)

  • CPI-637 induced a significant decrease in the level of BRD4 bound to the HIV-1 promoter, while the levels of cyclin-dependent kinase 9 (CDK9), Tat, and RNA Pol II CTD Ser2 phosphorylation were upregulated by 4.2-fold, 7.2-fold and 6.0-fold, respectively. These results indicate that CPI-637 reactivated HIV-1 expression by dissociating BRD4 from the HIV-1 long terminal repeat (LTR) promoter, permitting Tat to bind positive transcription elongation factor b (P-TEFb) and assembling Tat-super-elongation complex (SEC) on the transactivation response (TAR) stem-loop structure for RNA Pol II CTD Ser2 phosphorylation

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Summary

Introduction

Highly active antiretroviral therapy (HAART) has dramatically decreased morbidity and mortality in patients infected with human immunodeficiency virus type 1 (HIV-1), a rapid rebound in plasma viremia to pretreatment levels is observed after the interruption of HAART treatment (Van Lint et al, 2013). Due to the lack of viral transcription, latently infected cells are usually difficult to identify and eliminate by both the innate and adaptive immune responses and antiviral drugs (Chun et al, 1997; Dufour et al, 2020). One strategy, termed “shock and kill”, aims to reactivate dormant viruses from the HIV-1 latent reservoir by regulating hostdependent pathways and eradicate the reservoir through HIV-1-related cytopathic effects or immune system-based clearance of infected cells (Abner and Jordan, 2019). To expose the latent reservoirs for accelerated clearance, numerous latency-reversing agents (LRAs) targeting specific steps of HIV-1 transcription have been identified (Spivak and Planelles, 2018). A combinatory regimen including a set of LRAs targeting multiple steps of HIV-1 latency is expected to reactivate all integrated proviruses and effectively purge latent reservoirs

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