Integrated single-cell multiomic analysis of HIV latency reversal reveals novel regulators of viral reactivation
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ABSTRACT: Despite the success of antiretroviral therapy, HIV cannot be cured because of a reservoir of latently infected cells that evades therapy. To understand the mechanisms of HIV latency, we employed an integrated single-cell RNA-seq/ATAC-seq approach to simultaneously profile the transcriptomic and epigenomic characteristics of ~125,000 latently infected primary CD4 cells after reactivation using three different latency-reversing agents.
Project description:The barrier to HIV-1 functional cure is caused by a small pool of latently infected resting CD4 T-cells that persist under antiretroviral therapy. Notably this latent reservoir of infected cells will produce replication-competent infectious virus once prolonged suppressive HAART is withdrawn. The reactivation of HIV-1 gene expression in T-cells harboring latent provirus in HIV-1 patients under HAART will likely result in depletion of this latent reservoir due to cytopathic effects and immune clearance. Many studies have investigated small molecules that reactivate HIV-1 gene expression but to date no latency reversal agent (LRA) has been identified to be specific, non-toxic, and effective in primary T-cells isolated from HIV-1 infected individuals undergoing long-term HAART. Stochastic fluctuations in HIV-1 tat gene expression have been attributed to be essential in the viral progression to latency. We hypothesized that exposing Tat to latently infected CD4 T-cells will result in potent latency reversal. Our results indicate the capacity of an engineered Tat to reactivate HIV-1 in latently infected cells from patients to a similar degree as the protein kinase C agonist PMA (Phorbol 12-Myristate 13-Acetate) while showing no T-cell activation nor any significant transcriptome perturbation in primary CD4 T-cells.
Project description:HIV-1 infected patients virally suppressed by antiviral treatment harbor a persistent reservoir of replication competent latent HIV-1 infected cells, which constitute the main roadblock to a cure. A main strategy for HIV cure aims to stimulate viral gene expression in latently infected cells so that they can be cleared. Crucial for the design of drugs referred to as “latency-reversing agents” (LRAs) is the identification of molecular targets for latency reversal. The regulatory factors physically associated with and repressing the latent HIV-1 promoter or 5’LTR would provide ideal putative molecular targets for latency reversal. However, due to technical limitations, the comprehensive and unbiased identification of host proteins associated with the latent or active integrated HIV LTR in infected cells not been possible. Here we use dCas9 targeted chromatin and histone enrichment strategy coupled to mass spectrometry (Catchet-MS), to purify the locus-associated dCas9 bait, guided downstream of the HIV-1 transcriptional start site (TSS) in latent and activated HIV-1 infected T cells to identify the 5’LTR bound latent and active regulatory complexes. Catchet-MS identified both previously described as well as novel host factors distinctly associated with the latent versus transcriptionally active HIV-1 5’LTR. Within the identified factors we find the transcription factor IKZF1 to be a novel repressor of the HIV-1 promoter required for maintenance of latency, and thus a molecular target for latency reversal. Finally, we identify the FDA approved drug, Iberdomide, which targets IKZF1 for degradation to be a novel LRA, which reversed latency in latent ex vivo HIV-1 infected primary CD4+ T cells and in cells isolated from HIV-1 infected, aviremic participants.
Project description:Background: The cellular reservoir of latent HIV infection remains the main barrier to cure this virus. Elimination of this reservoir would be possible, if molecular identity of latently infected cells were fully elucidated. Biomarkers proposed previously were able to capture only a relatively small fraction of all reservoir cells. In the present study, we set out to conduct comprehensive molecular profiling, at the protein and RNA levels, of CD4+ T cells latently infected with HIV in vitro, using liquid chromatography-mass spectrometry (LC-MS) and RNA sequencing (RNA-Seq), respectively. Protein-based methods such as quantitative proteomic profiling using LC-MS may be more beneficial due to direct transferability of results to antibody-based approaches to capture latently infected cells. Integrated analysis of proteomic and transcriptomic data adds a level of validation and increases confidence in identified biomarkers. Flow cytometry and integrated HIV DNA assay were further used to enrich for latently infected cells with antibodies against selected biomarker proteins. Results: Using quantitative proteomics, we identified a total of 10,886 proteins (peptide level FDR < 0.05), of which 673 were up- and 780 down-regulated in latently infected compared to mock-infected cells in vitro (p < 0.05). Among these proteins, 21 were dysregulated at the RNA level in the same direction. Pathway analysis identified p53, mTOR, Wnt and NOTCH signaling, demonstrating that our in vitro model reflects known mechanisms of latency establishment and maintenance. Comparison of identified proteins with other proteomics studies revealed that identified molecular signatures of latency depend on technology and cell types used; however, a subset of proteins were identified both in the present, and at least one other study. Antibodies against selected protein markers, CEACAM1 and PLXNB2, could enrich for latently infected cells from mixed cell population 3-10 fold (5.8 fold average, p < 0.001). Conclusion: Two new molecules, CEACAM1 and PLXNB2, were identified as biomarkers for HIV latency. However, the level of enrichment for latently infected cells compared to biomarkers proposed previously was not improved. These results are consistent with the idea that each proposed biomarker defines only a subset of latently infected cells, and that a combined biomarker will be required to capture or target the latent HIV reservoir represented by different cell types.
Project description:HIV infection remains incurable due to the long-term persistence of latently infected cells, capable of refueling viremia upon antiretroviral therapy interruption. Shock-and-kill strategies aim to purge this latent reservoir by inducing the expression of viral genes, making infected cells visible for cleanup by the immune system. Here, we present a Tat mRNA formulation that, when combined with panobinostat, enables latency reversal at levels >3-fold higher than those reached with the most potent mitogens. We demonstrate that this mRNA formulation does not alter the transcriptome or phenotype of CD4 T cells, enabling the ex vivo assessment of infected cells upon latency reversal in a near-native state. Taking advantage of this characteristic, we show transcriptomic and proteomic differences between infected cells upon latency reversal and non-infected cells, including the upregulation of the cytotoxic protein granzyme A and a novel long non-coding RNA. Overall, we demonstrate that a Tat mRNA formulation enables potent reactivation of latent HIV, presenting a valuable research tool for studying the inducible HIV reservoir, as well as paving the way to a more effective shock-and-kill functional cure.
Project description:HIV latency is a major obstacle to curing infection. Current strategies to eradicate HIV aim at increasing transcription of the latent provirus. In the present study we observed that latently infected CD4+ T cells from HIV-infected individuals failed to produce viral particles upon ex vivo exposure to SAHA (vorinostat), despite effective inhibition of histone deacetylases. To identify steps that were not susceptible to the action of SAHA or other latency reverting agents, we used a primary CD4+ T cell model, joint host and viral RNA sequencing, and a viral-encoded reporter. This model served to investigate the characteristics of latently infected cells, the dynamics of HIV latency, and the process of reactivation induced by various stimuli. During latency, we observed persistence of viral transcripts but only limited viral translation. Similarly, the reactivating agents SAHA and disulfiram successfully increased viral transcription, but failed to effectively enhance viral translation, mirroring the ex vivo data. This study highlights the importance of post-transcriptional blocks as one mechanism leading to HIV latency that needs to be relieved in order to purge the viral reservoir.
Project description:HIV-1 infects lymphoid and myeloid cells, which can harbor a latent proviral reservoir responsible for maintaining lifelong infection. Glycolytic metabolism has been identified as a determinant of susceptibility to HIV-1 infection, but its role in the development and maintenance of HIV-1 latency has not been elucidated. By combining transcriptomic, proteomic and metabolomic analysis, we here show that transition to latent HIV-1 infection downregulates glycolysis, while viral reactivation by conventional stimuli reverts this effect. Decreased glycolytic output in latently infected cells is associated with downregulation of NAD+/NADH. Consequently, infected cells rely on the parallel pentose phosphate pathway and its main product, the antioxidant NADPH, fueling antioxidant pathways maintaining HIV-1 latency. Of note, blocking NADPH downstream effectors, thioredoxin and glutathione, favors HIV-1 reactivation from latency in lymphoid and myeloid cellular models. This provides a “shock and kill effect” decreasing proviral DNA in cells from people-living-with-HIV/AIDS. Overall, our data show that downmodulation of glycolysis is a metabolic signature of HIV-1 latency that can be exploited to target latently infected cells with eradication strategies.
Project description:To identify novel host factors as putative targets to reverse HIV-1 latency, we performed an insertional mutagenesis genetic screen in a latently HIV-1-infected pseudohaploid KBM7 cell line (Hap-Lat). Following mutagenesis, insertions were mapped to the genome, and bioinformatic analysis resulted in the identification of 69 candidate host genes involved in maintaining HIV-1 latency.
Project description:The goal of this study was to utilize CaptureSeq to be able to measure HIV-1 transcription after reversal of latency in primary cells from antiretroviral-treated HIV-1 infected individuals.
Project description:Resting CD4+ T cells that are both persistent and latently infected with HIV represent the most important challenge to HIV eradication. Estimates indicate the need for >70 years of continuous, fully suppressive, antiretroviral therapy (ART) to eliminate the HIV reservoir. Alternatively, induction of HIV from its latent state could accelerate the decline of the reservoir, thereby shortening the time to eradication. Previous attempts to reactivate latent HIV in preclinical animal models and in clinical trials have measured HIV induction in peripheral blood with minimal focus on tissue reservoirs and had limited effect. We found that activation of the non-canonical NF-B signaling pathway via AZD5582 results in induction of HIV- and SIV-RNA expression in the blood and tissues of ART-suppressed humanized mice and rhesus macaques. Analysis of resting CD4+ T cells from tissues after AZD55852 treatment revealed increased SIV-RNA in lymph nodes in macaques and robust induction of HIV in virtually all tissues analyzed in humanized mice including lymph nodes, thymus, bone marrow, liver, and lung. This promising new approach to latency reversal, in combination with the appropriate tools for systemic clearance of persistent HIV infection, greatly increases opportunities for HIV eradication.
Project description:Latently infected resting CD4+ T cells are a major barrier to HIV cure. Understanding how latency is established, maintained and reversed is critical to identifying novel strategies to eliminate latently infected cells. We demonstrate here that co-culture of resting CD4+ T cells and syngeneic myeloid dendritic cells (mDC) can dramatically increase the frequency of HIV DNA integration and latent HIV infection in non-proliferating memory, but not naïve, CD4+ T cells. Gene expression in non-proliferating CD4+ T cells, enriched for latent infection, showed significant changes in the expression of genes involved in cellular activation and interferon regulated pathways, including the down-regulation of genes controlling both NF-κB and cell cycle. We conclude that mDC play a key role in the establishment of HIV latency in resting memory CD4+ T cells, which is predominantly mediated through signalling during DC-T cell contact.