Determinants of the efficacy of HIV latency-reversing agents and implications for drug and treatment design.

HIV eradication studies have focused on developing latency-reversing agents (LRAs). However, it is not understood how the rate of latent reservoir reduction is affected by different steps in the process of latency reversal. Furthermore, as current LRAs are host-directed, LRA treatment is likely to be intermittent to avoid host toxicities.

Single-Cell Analysis of Quiescent HIV Infection Reveals Host Transcriptional Profiles that Regulate Proviral Latency.

A detailed understanding of the mechanisms that establish or maintain the latent reservoir of HIV will guide approaches to eliminate persistent infection. We used a cell line and primary cell models of HIV latency to investigate viral RNA (vRNA) expression and the role of the host transcriptome using single-cell approaches. Single-cell vRNA quantitation identified distinct populations of cells expressing various levels of vRNA, including completely silent populations.

HIV-Specific, Ex Vivo Expanded T Cell Therapy: Feasibility, Safety, and Efficacy in ART-Suppressed HIV-Infected Individuals.

Adoptive T cell therapy has had dramatic successes in the treatment of virus-related malignancies and infections following hematopoietic stem cell transplantation. We adapted this method to produce ex vivo expanded HIV-specific T cells (HXTCs), with the long-term goal of using HXTCs as part of strategies to clear persistent HIV infection. In this phase 1 proof-of-concept study (NCT02208167), we administered HXTCs to antiretroviral therapy (ART)-suppressed, HIV-infected participants.

Correction to: HIV Persistence on Antiretroviral Therapy and Barriers to a Cure.

Correction to: Chapter 7 in L. Zhang, S. R.

HIV Persistence on Antiretroviral Therapy and Barriers to a Cure.

HIV persists within the body despite successful suppression of virus replication with antiretroviral therapy (ART). HIV lurks in latent and active reservoirs, leading to rebound of virus spread if ART is interrupted. The latent HIV reservoir is a natural consequence of the life cycle of HIV, with integration of HIV into the genomes of cells that are or later enter the resting state, resulting in transcriptionally quiescent provirus.

γδ T cells: an immunotherapeutic approach for HIV cure strategies.

Current strategies aimed to cure HIV infection are based on combined efforts to reactivate the virus from latency and improve immune effector cell function to clear infected cells. These strategies are primarily focused on CD8+ T cells and approaches are challenging due to insufficient HIV antigen production from infected cells and poor HIV-specific CD8+ T cells. γδ T cells represent a unique subset of effector T cells that can traffic to tissues, and selectively target cancer or virally infected cells without requiring MHC presentation.

Interleukin-15-Stimulated Natural Killer Cells Clear HIV-1-Infected Cells following Latency Reversal .

Current efforts toward human immunodeficiency virus (HIV) eradication include approaches to augment immune recognition and elimination of persistently infected cells following latency reversal. Natural killer (NK) cells, the main effectors of the innate immune system, recognize and clear targets using different mechanisms than CD8 T cells, offering an alternative or complementary approach for HIV clearance strategies. We assessed the impact of interleukin 15 (IL-15) treatment on NK cell function and the potential for stimulated NK cells to clear the HIV reservoir.

HDAC inhibition induces HIV-1 protein and enables immune-based clearance following latency reversal.

Promising therapeutic approaches for eradicating HIV include transcriptional activation of provirus from latently infected cells using latency-reversing agents (LRAs) and immune-mediated clearance to purge reservoirs. Accurate detection of cells capable of producing viral antigens and virions, and the measurement of clearance of infected cells, is essential to assessing therapeutic efficacy. Here, we apply enhanced methodology extending the sensitivity limits for the rapid detection of subfemtomolar HIV gag p24 capsid protein in CD4+ T cells from ART-suppressed HIV+ individuals, and we show viral protein induction following treatment with LRAs.

Vorinostat Renders the Replication-Competent Latent Reservoir of Human Immunodeficiency Virus (HIV) Vulnerable to Clearance by CD8 T Cells.

Unlabelled: Latently human immunodeficiency virus (HIV)-infected cells are transcriptionally quiescent and invisible to clearance by the immune system. To demonstrate that the latency reversing agent vorinostat (VOR) induces a window of vulnerability in the latent HIV reservoir, defined as the triggering of viral antigen production sufficient in quantity and duration to allow for recognition and clearance of persisting infection, we developed a latency clearance assay (LCA). The LCA is a quantitative viral outgrowth assay (QVOA) that includes the addition of immune effectors capable of clearing cells expressing viral antigen.

Interval dosing with the HDAC inhibitor vorinostat effectively reverses HIV latency.

Background: The histone deacetylase (HDAC) inhibitor vorinostat (VOR) can increase HIV RNA expression in vivo within resting CD4+ T cells of aviremic HIV+ individuals. However, while studies of VOR or other HDAC inhibitors have reported reversal of latency, none has demonstrated clearance of latent infection. We sought to identify the optimal dosing of VOR for effective serial reversal of HIV latency.

Chromatin Regulation and the Histone Code in HIV Latency .

The formation of a latent reservoir of Human Immunodeficiency Virus (HIV) infection hidden from immune clearance remains a significant obstacle to approaches to eradicate HIV infection. Towards an understanding of the mechanisms of HIV persistence, there is a growing body of work implicating epigenetic regulation of chromatin in establishment and maintenance of this latent reservoir. Here we discuss recent advances in the field of chromatin regulation, specifically in our understanding of the histone code, and how these discoveries relate to our current knowledge of the chromatin mechanisms linked to HIV transcriptional repression and the reversal of latency.

Proviral Latency, Persistent Human Immunodeficiency Virus Infection, and the Development of Latency Reversing Agents.

Quiescent proviral genomes that persist during human immunodeficiency virus type 1 (HIV-1) infection despite effective antiretroviral therapy (ART) can fuel rebound viremia after ART interruption and is a central obstacle to the cure of HIV infection. The induction of quiescent provirus is the goal of a new class of potential therapeutics, latency reversing agents (LRAs). The discovery, development, and testing of HIV LRAs is a key part of current efforts to develop latency reversal and viral clearance strategies to eradicate established HIV infection.

Interrupting antiretroviral treatment in HIV cure research: scientific and ethical considerations.

Over the past several years there has been intense activity directed at the possibility of achieving remission or eradication of HIV infection. Current assays for the measurement of latent HIV are insufficient to demonstrate complete clearance of replication-competent HIV. Therefore, the ultimate test for assessing whether investigational interventions have resulted in HIV remission or eradication is to interrupt standard antiretroviral therapy (ART) in a carefully controlled clinical trial setting.

Benzotriazoles Reactivate Latent HIV-1 through Inactivation of STAT5 SUMOylation.

The presence of latent HIV-1 in infected individuals represents a major barrier preventing viral eradication. For that reason, reactivation of latent viruses in the presence of antiretroviral regimens has been proposed as a therapeutic strategy to achieve remission. We screened for small molecules and identified several benzotriazole derivatives with the ability to reactivate latent HIV-1.

HIV antibodies for treatment of HIV infection.

The bar is high to improve on current combination antiretroviral therapy (ART), now highly effective, safe, and simple. However, antibodies that bind the HIV envelope are able to uniquely target the virus as it seeks to enter new target cells, or as it is expressed from previously infected cells. Furthermore, the use of antibodies against HIV as a therapeutic may offer advantages.

Detection of human immunodeficiency virus RNAs in living cells using Spinach RNA aptamers.

Many techniques currently used to measure HIV RNA production in cells suffer from limitations that include high background signal or the potential to destroy cellular context. Fluorophore-binding RNA aptamers offer the potential for visualizing RNAs directly in living cells with minimal cellular perturbation. We inserted a sequence encoding a fluorophore-binding RNA aptamer, known as Spinach, into the HIV genome such that predicted RNA secondary structures in both Spinach and HIV were preserved.

Transcriptomic Analysis Implicates the p53 Signaling Pathway in the Establishment of HIV-1 Latency in Central Memory CD4 T Cells in an In Vitro Model.

The search for an HIV-1 cure has been greatly hindered by the presence of a viral reservoir that persists despite antiretroviral therapy (ART). Studies of HIV-1 latency in vivo are also complicated by the low proportion of latently infected cells in HIV-1 infected individuals. A number of models of HIV-1 latency have been developed to examine the signaling pathways and viral determinants of latency and reactivation.

HIV Latency-Reversing Agents Have Diverse Effects on Natural Killer Cell Function.

In an effort to clear persistent HIV infection and achieve a durable therapy-free remission of HIV disease, extensive pre-clinical studies and early pilot clinical trials are underway to develop and test agents that can reverse latent HIV infection and present viral antigen to the immune system for clearance. It is, therefore, critical to understand the impact of latency-reversing agents (LRAs) on the function of immune effectors needed to clear infected cells. We assessed the impact of LRAs on the function of natural killer (NK) cells, the main effector cells of the innate immune system.

Quantification of the Latent HIV-1 Reservoir Using Ultra Deep Sequencing and Primer ID in a Viral Outgrowth Assay.

Background: In this study, we measured the latent HIV-1 reservoir harboring replication-competent HIV-1 in resting CD4 T cells in participants on highly active antiretroviral therapy, quantitating the frequency of latent infection through the use of a Primer ID-based Ultra Deep Sequencing Assay (UDSA), in comparison to the readout of the quantitative viral outgrowth assay (QVOA).

Methods: Viral RNA derived from culture wells of QVOA that scored as HIV-1 p24 capsid antigen positive were tagged with a specific barcode during cDNA synthesis, and the sequences within the V1-V3 region of the HIV-1 env gene were analyzed for diversity using the Primer ID-based paired-end MiSeq platform. We analyzed samples from a total of 19 participants, 2 initially treated with highly active antiretroviral therapy in acute infection and 17 treated during chronic infection.

The differential short- and long-term effects of HIV-1 latency-reversing agents on T cell function.

Despite the extraordinary success of HIV-1 antiretroviral therapy in prolonging life, infected individuals face lifelong therapy because of a reservoir of latently-infected cells that harbor replication competent virus. Recently, compounds have been identified that can reverse HIV-1 latency in vivo. These latency- reversing agents (LRAs) could make latently-infected cells vulnerable to clearance by immune cells, including cytolytic CD8+ T cells.

Dendritic Cell Immunotherapy for HIV-1 Infection Using Autologous HIV-1 RNA: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial.

Background: The genomic heterogeneity of HIV-1 impedes the ability of consensus sequences in vaccines to elicit effective antiviral immune responses. AGS-004 amplifies translation-competent RNA molecules encoding for Gag, Rev, Vpr, and Nef from the patient's autologous virus and loads them into dendritic cells.

Methods: This phase IIB, multicenter, 2:1 randomized, double-blind, placebo-controlled study enrolled 54 HIV-1-infected patients on antiretroviral therapy with viral loads (VLs) <50 copies per milliliter, current CD4 T-cell counts >450 cells per cubic millimeter, and nadir counts >200 cells per cubic millimeter, to receive intradermal injections of study product into the axillary lymph node region every 4 weeks.

HIV reservoirs: what, where and how to target them.

One of the main challenges in the fight against HIV infection is to develop strategies that are able to eliminate the persistent viral reservoir that harbours integrated, replication-competent provirus within host cellular DNA. This reservoir is resistant to antiretroviral therapy (ART) and to clearance by the immune system of the host; viruses originating from this reservoir lead to rebound viraemia once treatment is stopped, giving rise to new rounds of infection. Several studies have focused on elucidating the cells and tissues that harbour persistent virus, the true size of the reservoir and how best to target it, but these topics are the subject of ongoing debate.