The inhibitor apoptosis protein antagonist Debio 1143 Is an attractive HIV-1 latency reversal candidate

Dynamic modulation of the non-canonical NF-κB signaling pathway for HIV shock and kill

HIV cure still remains an elusive target. The "Shock and Kill" strategy which aims to reactivate HIV from latently infected cells and subsequently kill them through virally induced apoptosis or immune mediated clearance, is the subject of widespread investigation. NF-κB is a ubiquitous transcription factor which serves as a point of confluence for a number of intracellular signaling pathways and is also a crucial regulator of HIV transcription. Due to its relatively lower side effect profile and proven role in HIV transcription, the non-canonical NF-κB pathway has emerged as an attractive target for HIV reactivation, as a first step towards eradication. A comprehensive review examining this pathway in the setting of HIV and its potential utility to cure efforts is currently lacking. This review aims to summarize non-canonical NF-κB signaling and the importance of this pathway in HIV shock-and-kill efforts.

Breaking the Silence: Regulation of HIV Transcription and Latency on the Road to a Cure

Antiretroviral therapy (ART) has brought the HIV/AIDS epidemic under control, but a curative strategy for viral eradication is still needed. The cessation of ART results in rapid viral rebound from latently infected CD4+ T cells, showing that control of viral replication alone does not fully restore immune function, nor does it eradicate viral reservoirs. With a better understanding of factors and mechanisms that promote viral latency, current approaches are primarily focused on the permanent silencing of latently infected cells ("block and lock") or reactivating HIV-1 gene expression in latently infected cells, in combination with immune restoration strategies to eliminate HIV infected cells from the host ("shock and kill"). In this review, we provide a summary of the current, most promising approaches for HIV-1 cure strategies, including an analysis of both latency-promoting agents (LPA) and latency-reversing agents (LRA) that have shown promise in vitro, ex vivo, and in human clinical trials to reduce the HIV-1 reservoir.

New Concepts in Therapeutic Manipulation of HIV-1 Transcription and Latency: Latency Reversal versus Latency Prevention

Antiretroviral therapy (ART) has dramatically improved the prognosis for people living with HIV-1, but a cure remains elusive. The largest barrier to a cure is the presence of a long-lived latent reservoir that persists within a heterogenous mix of cell types and anatomical compartments. Efforts to eradicate the latent reservoir have primarily focused on latency reversal strategies. However, new work has demonstrated that the majority of the long-lived latent reservoir is established near the time of ART initiation, suggesting that it may be possible to pair an intervention with ART initiation to prevent the formation of a sizable fraction of the latent reservoir. Subsequent treatment with latency reversal agents, in combination with immune clearance agents, may then be a more tractable strategy for fully clearing the latent reservoir in people newly initiating ART. Here, we summarize molecular mechanisms of latency establishment and maintenance, ongoing efforts to develop effective latency reversal agents, and newer efforts to design latency prevention agents. An improved understanding of the molecular mechanisms involved in both the establishment and maintenance of latency will aid in the development of new latency prevention and reversal approaches to ultimately eradicate the latent reservoir.

The Effect of Xevinapant Combined with Ionizing Radiation on HNSCC and Normal Tissue Cells and the Impact of Xevinapant on Its Targeted Proteins cIAP1 and XIAP

The poor prognosis of HNSCC is partly due to treatment resistance. The SMAC mimetic Xevinapant is a promising new approach to targeted cancer therapy. Xevinapant inhibits cIAP1/2 and XIAP, leading to apoptosis, necroptosis and inhibition of prosurvival signaling. Combining Xevinapant with IR could improve therapeutic potential. The effect of Xevinapant in combination with IR on HNSCC and healthy tissue cells was investigated. Cell growth, cell death, clonogenic survival and DNA double-strand breaks (DSBs) were studied, and intracellular cIAP1 and XIAP levels were evaluated. Xevinapant had cytostatic and cytotoxic, as well as radiosensitizing, effects on the malignant cells, while healthy tissue cells were less affected. Apoptotic and necrotic cell death was particularly affected, but the increase in residual DSBs and the reduced survival implied an additional effect of Xevinapant on DNA damage repair and other cell inactivation mechanisms. cIAP1 and XIAP levels varied for each cell line and were affected by Xevinapant and IR treatment. There was an association between higher IAP levels and increased cell death. Xevinapant appears to be a potent new drug for HNSCC therapy, especially in combination with IR. IAP levels could be an indicator for impaired DNA damage repair and increased susceptibility to cellular stress.

The Involvement of Ubiquitination and SUMOylation in Retroviruses Infection and Latency

Retroviruses, especially the pathogenic human immunodeficiency virus type 1 (HIV-1), have severely threatened human health for decades. Retroviruses can form stable latent reservoirs via retroviral DNA integration into the host genome, and then be temporarily transcriptional silencing in infected cells, which makes retroviral infection incurable. Although many cellular restriction factors interfere with various steps of the life cycle of retroviruses and the formation of viral latency, viruses can utilize viral proteins or hijack cellular factors to evade intracellular immunity. Many post-translational modifications play key roles in the cross-talking between the cellular and viral proteins, which has greatly determined the fate of retroviral infection. Here, we reviewed recent advances in the regulation of ubiquitination and SUMOylation in the infection and latency of retroviruses, focusing on both host defense- and virus counterattack-related ubiquitination and SUMOylation system. We also summarized the development of ubiquitination- and SUMOylation-targeted anti-retroviral drugs and discussed their therapeutic potential. Manipulating ubiquitination or SUMOylation pathways by targeted drugs could be a promising strategy to achieve a "sterilizing cure" or "functional cure" of retroviral infection.

Medicinal Chemistry of Anti-HIV-1 Latency Chemotherapeutics: Biotargets, Binding Modes and Structure-Activity Relationship Investigation

The existence of latent viral reservoirs (LVRs), also called latent cells, has long been an acknowledged stubborn hurdle for effective treatment of HIV-1/AIDS. This stable and heterogeneous reservoir, which mainly exists in resting memory CD4⁺ T cells, is not only resistant to highly active antiretroviral therapy (HAART) but cannot be detected by the immune system, leading to rapid drug resistance and viral rebound once antiviral treatment is interrupted. Accordingly, various functional cure strategies have been proposed to combat this barrier, among which one of the widely accepted and utilized protocols is the so-called 'shock-and-kill' regimen. The protocol begins with latency-reversing agents (LRAs), either alone or in combination, to reactivate the latent HIV-1 proviruses, then eliminates them by viral cytopathic mechanisms (e.g., currently available antiviral drugs) or by the immune killing function of the immune system (e.g., NK and CD8+ T cells). In this review, we focuse on the currently explored small molecular LRAs, with emphasis on their mechanism-directed drug targets, binding modes and structure-relationship activity (SAR) profiles, aiming to provide safer and more effective remedies for treating HIV-1 infection.

The role of latency reversal in HIV cure strategies

One strategy to eliminate latently infected cells that persist in people with HIV on antiretroviral therapy is to activate virus transcription and virus production to induce virus or immune‐mediated cell death. This is called latency reversal. Despite clear activity of multiple latency reversal agents in vitro, clinical trials of latency‐reversing agents have not shown significant reduction in latently infected cells. We review new insights into the biology of HIV latency and discuss novel approaches to enhance the efficacy of latency reversal agents.

Catchet-MS identifies IKZF1-targeting thalidomide analogues as novel HIV-1 latency reversal agents

A major pharmacological strategy toward HIV cure aims to reverse latency in infected cells as a first step leading to their elimination. While the unbiased identification of molecular targets physically associated with the latent HIV-1 provirus would be highly valuable to unravel the molecular determinants of HIV-1 transcriptional repression and latency reversal, due to technical limitations, this has been challenging. Here we use a dCas9 targeted chromatin and histone enrichment strategy coupled to mass spectrometry (Catchet-MS) to probe the differential protein composition of the latent and activated HIV-1 5′LTR. Catchet-MS identified known and novel latent 5′LTR-associated host factors. Among these, IKZF1 is a novel HIV-1 transcriptional repressor, required for Polycomb Repressive Complex 2 recruitment to the LTR. We find the clinically advanced thalidomide analogue iberdomide, and the FDA approved analogues lenalidomide and pomalidomide, to be novel LRAs. We demonstrate that, by targeting IKZF1 for degradation, these compounds reverse HIV-1 latency in CD4+ T-cells isolated from virally suppressed people living with HIV-1 and that they are able to synergize with other known LRAs.

Insights Into Persistent HIV-1 Infection and Functional Cure: Novel Capabilities and Strategies

Although HIV-1 replication can be efficiently suppressed to undetectable levels in peripheral blood by combination antiretroviral therapy (cART), lifelong medication is still required in people living with HIV (PLWH). Life expectancies have been extended by cART, but age-related comorbidities have increased which are associated with heavy physiological and economic burdens on PLWH. The obstacle to a functional HIV cure can be ascribed to the formation of latent reservoir establishment at the time of acute infection that persists during cART. Recent studies suggest that some HIV reservoirs are established in the early acute stages of HIV infection within multiple immune cells that are gradually shaped by various host and viral mechanisms and may undergo clonal expansion. Early cART initiation has been shown to reduce the reservoir size in HIV-infected individuals. Memory CD4+ T cell subsets are regarded as the predominant cellular compartment of the HIV reservoir, but monocytes and derivative macrophages or dendritic cells also play a role in the persistent virus infection. HIV latency is regulated at multiple molecular levels in transcriptional and post-transcriptional processes. Epigenetic regulation of the proviral promoter can profoundly regulate the viral transcription. In addition, transcriptional elongation, RNA splicing, and nuclear export pathways are also involved in maintaining HIV latency. Although most proviruses contain large internal deletions, some defective proviruses may induce immune activation by expressing viral proteins or producing replication-defective viral-like particles. In this review article, we discuss the state of the art on mechanisms of virus persistence in the periphery and tissue and summarize interdisciplinary approaches toward a functional HIV cure, including novel capabilities and strategies to measure and eliminate the infected reservoirs and induce immune control.

So Pathogenic or So What?-A Brief Overview of SIV Pathogenesis with an Emphasis on Cure Research

HIV infection requires lifelong antiretroviral therapy (ART) to control disease progression. Although ART has greatly extended the life expectancy of persons living with HIV (PWH), PWH nonetheless suffer from an increase in AIDS-related and non-AIDS related comorbidities resulting from HIV pathogenesis. Thus, an HIV cure is imperative to improve the quality of life of PWH. In this review, we discuss the origins of various SIV strains utilized in cure and comorbidity research as well as their respective animal species used. We briefly detail the life cycle of HIV and describe the pathogenesis of HIV/SIV and the integral role of chronic immune activation and inflammation on disease progression and comorbidities, with comparisons between pathogenic infections and nonpathogenic infections that occur in natural hosts of SIVs. We further discuss the various HIV cure strategies being explored with an emphasis on immunological therapies and "shock and kill".

SMAC Mimetics as Therapeutic Agents in HIV Infection

Although combination antiretroviral therapy is extremely effective in lowering HIV RNA to undetectable levels in the blood, HIV persists in latently infected CD4⁺ T-cells and persistently infected macrophages. In latently/persistently infected cells, HIV proteins have shown to affect the expression of proteins involved in the apoptosis pathway, notably the inhibitors of apoptosis proteins (IAPs), and thereby influence cell survival. IAPs, which are inhibited by endogenous second mitochondrial-derived activators of caspases (SMAC), can serve as targets for SMAC mimetics, synthetic compounds capable of inducing apoptosis. There is increasing evidence that SMAC mimetics can be used to reverse HIV latency and/or kill cells that are latently/persistently infected with HIV. Here, we review the current state of knowledge of SMAC mimetics as an approach to eliminate HIV infected cells and discuss the potential future use of SMAC mimetics as part of an HIV cure strategy.

Fighting HIV-1 Persistence: At the Crossroads of "Shoc-K and B-Lock"

Despite the success of highly active antiretroviral therapy (HAART), integrated HIV-1 proviral DNA cannot be eradicated from an infected individual. HAART is not able to eliminate latently infected cells that remain invisible to the immune system. Viral sanctuaries in specific tissues and immune-privileged sites may cause residual viral replication that contributes to HIV-1 persistence. The “Shock or Kick, and Kill” approach uses latency reversing agents (LRAs) in the presence of HAART, followed by cell-killing due to viral cytopathic effects and immune-mediated clearance. Different LRAs may be required for the in vivo reactivation of HIV-1 in different CD4⁺ T cell reservoirs, leading to the activation of cellular transcription factors acting on the integrated proviral HIV-1 LTR. An important requirement for LRA drugs is the reactivation of viral transcription and replication without causing a generalized immune activation. Toll-like receptors, RIG-I like receptors, and STING agonists have emerged recently as a new class of LRAs that augment selective apoptosis in reactivated T lymphocytes. The challenge is to extend in vitro observations to HIV-1 positive patients. Further studies are also needed to overcome the mechanisms that protect latently infected cells from reactivation and/or elimination by the immune system. The Block and Lock alternative strategy aims at using latency promoting/inducing agents (LPAs/LIAs) to block the ability of latent proviruses to reactivate transcription in order to achieve a long term lock down of potential residual virus replication. The Shock and Kill and the Block and Lock approaches may not be only alternative to each other, but, if combined together (one after the other), or given all at once [namely “Shoc-K(kill) and B(block)-Lock”], they may represent a better approach to a functional cure.

Selective elimination of host cells harboring replication-competent human immunodeficiency virus reservoirs: a promising therapeutic strategy for HIV cure

ABSTRACT

Many seminal advances have been made in human immunodeficiency virus (HIV)/AIDS research over the past four decades. Treatment strategies, such as gene therapy and immunotherapy, are yielding promising results to effectively control HIV infection. Despite this, a cure for HIV/AIDS is not envisioned in the near future. A recently published academic study has raised awareness regarding a promising alternative therapeutic option for HIV/AIDS, referred to as "selective elimination of host cells capable of producing HIV" (SECH). Similar to the "shock and kill strategy," the SECH approach requires the simultaneous administration of drugs targeting key mechanisms in specific cells to efficiently eliminate HIV replication-competent cellular reservoirs. Herein, we comprehensively review the specific mechanisms targeted by the SECH strategy. Briefly, the suggested cocktail of drugs should contain (i) latency reversal agents to promote the latency reversal process in replication-competent reservoir cells, (ii) pro-apoptotic and anti-autophagy drugs to induce death of infected cells through various pathways, and finally (iii) drugs that eliminate new cycles of infection by prevention of HIV attachment to host cells, and by HIV integrase inhibitor drugs. Finally, we discuss three major challenges that are likely to restrict the application of the SECH strategy in HIV/AIDS patients.

CD4+ T cell-mimicking nanoparticles encapsulating DIABLO/SMAC mimetics broadly neutralize HIV-1 and selectively kill HIV-1-infected cells

HIV-1 is a major global health challenge. The development of an effective vaccine and a therapeutic cure are top priorities. The creation of vaccines that focus an antibody response toward a particular epitope of a protein has shown promise, but the genetic diversity of HIV-1 stymies this progress. Therapeutic strategies that provide effective and broad‐spectrum neutralization against HIV-1 infection are highly desirable.

Methods: We investigated the potential of nanoengineered CD4+ T cell membrane-coated nanoparticles (TNP) encapsulating the DIABLO/SMAC mimetics LCL-161 or AT-406 (also known as SM-406 or Debio 1143) to both neutralize HIV-1 and selectively kill HIV-1-infected resting CD4+ T cells and macrophages.

Results: DIABLO/SMAC mimetic-loaded TNP displayed outstanding neutralizing breadth and potency, and selectively kill HIV-1-infected cells via autophagy-dependent apoptosis while having no drug-induced off-target or cytotoxic effects on bystander cells. Genetic inhibition of early stages of autophagy abolishes this effect.

Conclusion: DIABLO/SMAC mimetic loaded TNP have the potential to be used as therapeutic agents to neutralize cell-free HIV-1 and to kill specifically HIV-1-infected cells as part of an HIV-1 cure strategy.

Induction of Autophagy to Achieve a Human Immunodeficiency Virus Type 1 Cure

Effective antiretroviral therapy has led to significant human immunodeficiency virus type 1 (HIV-1) suppression and improvement in immune function. However, the persistence of integrated proviral DNA in latently infected reservoir cells, which drive viral rebound post-interruption of antiretroviral therapy, remains the major roadblock to a cure. Therefore, the targeted elimination or permanent silencing of this latently infected reservoir is a major focus of HIV-1 research. The most studied approach in the development of a cure is the activation of HIV-1 expression to expose latently infected cells for immune clearance while inducing HIV-1 cytotoxicity—the “kick and kill” approach. However, the complex and highly heterogeneous nature of the latent reservoir, combined with the failure of clinical trials to reduce the reservoir size casts doubt on the feasibility of this approach. This concern that total elimination of HIV-1 from the body may not be possible has led to increased emphasis on a “functional cure” where the virus remains but is unable to reactivate which presents the challenge of permanently silencing transcription of HIV-1 for prolonged drug-free remission—a “block and lock” approach. In this review, we discuss the interaction of HIV-1 and autophagy, and the exploitation of autophagy to kill selectively HIV-1 latently infected cells as part of a cure strategy. The cure strategy proposed has the advantage of significantly decreasing the size of the HIV-1 reservoir that can contribute to a functional cure and when optimised has the potential to eradicate completely HIV-1.

Selective cell death in HIV-1-infected cells by DDX3 inhibitors leads to depletion of the inducible reservoir

An innovative approach to eliminate HIV-1-infected cells emerging out of latency, the major hurdle to HIV-1 cure, is to pharmacologically reactivate viral expression and concomitantly trigger intracellular pro-apoptotic pathways in order to selectively induce cell death (ICD) of infected cells, without reliance on the extracellular immune system. In this work, we demonstrate the effect of DDX3 inhibitors on selectively inducing cell death in latent HIV-1-infected cell lines, primary CD4+ T cells and in CD4+ T cells from cART-suppressed people living with HIV-1 (PLWHIV). We used single-cell FISH-Flow technology to characterise the contribution of viral RNA to inducing cell death. The pharmacological targeting of DDX3 induced HIV-1 RNA expression, resulting in phosphorylation of IRF3 and upregulation of IFNβ. DDX3 inhibition also resulted in the downregulation of BIRC5, critical to cell survival during HIV-1 infection, and selectively induced apoptosis in viral RNA-expressing CD4+ T cells but not bystander cells. DDX3 inhibitor treatment of CD4+ T cells from PLWHIV resulted in an approximately 50% reduction of the inducible latent HIV-1 reservoir by quantitation of HIV-1 RNA, by FISH-Flow, RT-qPCR and TILDA. This study provides proof of concept for pharmacological reversal of latency coupled to induction of apoptosis towards the elimination of the inducible reservoir.

Humanized Mice for the Evaluation of Novel HIV-1 Therapies

With the discovery of antiretroviral therapy, HIV-1 infection has transitioned into a manageable but chronic illness, which requires lifelong treatment. Nevertheless, complete eradication of the virus has still eluded us. This is partly due to the virus’s ability to remain in a dormant state in tissue reservoirs, ‘hidden’ from the host’s immune system. Also, the high mutation rate of HIV-1 results in escape mutations in response to many therapeutics. Regardless, the development of novel cures for HIV-1 continues to move forward with a range of approaches from immunotherapy to gene editing. However, to evaluate in vivo pathogenesis and the efficacy and safety of therapeutic approaches, a suitable animal model is necessary. To this end, the humanized mouse was developed by McCune in 1988 and has continued to be improved on over the past 30 years. Here, we review the variety of humanized mouse models that have been utilized through the years and describe their specific contribution in translating HIV-1 cure strategies to the clinic.

Latency Reversal 2.0: Giving the Immune System a Seat at the Table

PURPOSE OF REVIEW

For most people living with HIV (PLWH), treatment with effective antiretroviral therapy (ART) results in suppression of viremia below the limit of detection of clinical assays, immune reconstitution, reduced immune activation, avoidance of opportunistic infections, and progression to AIDS. However, ART alone is not curative, and HIV persists in a non-replicating, latent form. In this review, we provide a historical perspective on non-specific latency reversal approaches (LRA 1.0) and summarize recent advances in latency reversal strategies that target specific signaling pathways within CD4+ T cells or other immune cells to induce expression of latent HIV (immune-based latency reversal, or LRA 2.0).

RECENT FINDINGS

The HIV reservoir is primarily composed of latently infected CD4+ T cells carrying integrated, replication-competent provirus that can give rise to rebound viremia if ART is stopped. Myeloid lineage cells also contribute to HIV latency in certain tissues; we focus here on CD4+ T cells as a sufficient body of evidence regarding latency reversal in myeloid cells is lacking. The immunomodulatory LRA 2.0 approaches we describe include pattern recognition receptor agonists, immune checkpoint inhibitors, non-canonical NF-kB stimulation, and transient CD8+ lymphocyte depletion, along with promising combination strategies. We highlight recent studies demonstrating robust latency reversal in nonhuman primate models. While significant strides have been made in terms of virus reactivation from latency, initial hopes for latency reversal alone to result in a reduction of infected cells, through viral cytopathic effect or an unboosted immune system, have not been realized and it seems clear that even effective latency reversal strategies will need to be paired with an approach that facilitates immune recognition and clearance of cells containing reactivated virus.

HIV-1 Latency and Viral Reservoirs: Existing Reversal Approaches and Potential Technologies, Targets, and Pathways Involved in HIV Latency Studies

Eradication of latent human immunodeficiency virus (HIV) infection is a global health challenge. Reactivation of HIV latency and killing of virus-infected cells, the so-called "kick and kill" or "shock and kill" approaches, are a popular strategy for HIV cure. While antiretroviral therapy (ART) halts HIV replication by targeting multiple steps in the HIV life cycle, including viral entry, integration, replication, and production, it cannot get rid of the occult provirus incorporated into the host-cell genome. These latent proviruses are replication-competent and can rebound in cases of ART interruption or cessation. In general, a very small population of cells harbor provirus, serve as reservoirs in ART-controlled HIV subjects, and are capable of expressing little to no HIV RNA or proteins. Beyond the canonical resting memory CD4⁺ T cells, HIV reservoirs also exist within tissue macrophages, myeloid cells, brain microglial cells, gut epithelial cells, and hematopoietic stem cells (HSCs). Despite a lack of active viral production, latently HIV-infected subjects continue to exhibit aberrant cellular signaling and metabolic dysfunction, leading to minor to major cellular and systemic complications or comorbidities. These include genomic DNA damage; telomere attrition; mitochondrial dysfunction; premature aging; and lymphocytic, cardiac, renal, hepatic, or pulmonary dysfunctions. Therefore, the arcane machineries involved in HIV latency and its reversal warrant further studies to identify the cryptic mechanisms of HIV reservoir formation and clearance. In this review, we discuss several molecules and signaling pathways, some of which have dual roles in maintaining or reversing HIV latency and reservoirs, and describe some evolving strategies and possible approaches to eliminate viral reservoirs and, ultimately, cure/eradicate HIV infection.

NF-κB sub-pathways and HIV cure: A revisit

HIV cure is thwarted by the presence of quiescent yet replication competent HIV-1 (HIV). Antiretroviral therapy (ART) is unable to eradicate reservoirs, and upon cessation of ART, HIV will rebound. This review encompasses the curative strategies of HIV in the context of NF-κB sub-pathways that are currently exploited and demonstrate promise in the disruption of latent HIV. Canonical NF-κB signaling has long been established to drive HIV proviral expression while noncanonical NF-κB signaling, a novel and perhaps more desirable mechanism of latency reversal due to its unique characteristics, has recently been shown to also promote HIV expression from latency. Furthermore, we discuss the previously unrecognized upstream signaling of NF-κB as a new avenue for exploration of a functional cure of HIV.

Transcriptome analysis reveals seven key immune pathways of Japanese flounder (Paralichthys olivaceus) involved in megalocytivirus infection

Megalocytivirus is a serious viral pathogen to many farmed fish including Japanese flounder (Paralichthys olivaceus). In this study, in order to systematically identify host immune genes induced by megalocytivirus infection, we examined the transcription profiles of flounder infected by megalocytivirus for 2, 6, and 8 days. Compared with uninfected fish, virus-infected fish exhibited 1242 differentially expressed genes (DEGs), with 225, 275, and 877 DEGs occurring at 2, 6, and 8 days post infection, respectively. Of these DEGs, 728 were upregulated and 659 were downregulated. The majority of DEGs were time-specific and formed four distinct expression profiles well correlated with the time of infection. The DEGs were classified into diverse Gene Ontology (GO) functional terms and enriched in 27 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, approximately one third of which were related to immunity. Weighted co-expression network analysis (WGCNA) was used to identify 16 key immune DEGs belonging to seven immune pathways (RIG-I-like receptor signaling pathway, JAK-STAT signaling pathway, TLR signaling pathway, cytokine-cytokine receptor interaction, phagosome, apoptosis, and p53 signaling pathway). These pathways interacted extensively and formed complicated networks. This study provided a global picture of megalocytivirus-induced gene expression profiles of flounder at the transcriptome level and uncovered a set of key immune genes and pathways closely linked to megalocytivirus infection. These results provided a set of targets for future delineation of the key factors implicated in the anti-megalocytivirus immunity of flounder.

SMAC mimetics induce autophagy-dependent apoptosis of HIV-1-infected macrophages

Human immunodeficiency type 1 (HIV)-infected macrophages (HIV-Mφ) are a reservoir for latent HIV infection and a barrier to HIV eradication. In contrast to CD4+ T cells, HIV-Mφ are resistant to the cytopathic effects of acute HIV infection and have increased expression of cell survival factors, including X-linked inhibitor of apoptosis (XIAP), baculoviral IAP repeat containing (BIRC) 2/cIAP1, beclin-1, BCL2, BCL-xl, triggering receptor expressed on myeloid cells 1, mitofusin (MFN) 1, and MFN2. DIABLO/SMAC mimetics are therapeutic agents that affect cancer cell survival and induce cell death. We found that DIABLO/SMAC mimetics (LCL-161, AT-406 (also known as SM-406 or Debio 1143), and birinapant) selectively kill HIV-Mφ without increasing bystander cell death. DIABLO/SMAC mimetic treatment of HIV-Mφ-induced XIAP and BIRC2 degradation, leading to the induction of autophagy and the formation of a death-inducing signaling complex on phagophore membranes that includes both pro-apoptotic or necroptotic (FADD, receptor-interacting protein kinase (RIPK) 1, RIPK3, caspase 8, and MLKL) and autophagy (ATG5, ATG7, and SQSTM1) proteins. Genetic or pharmacologic inhibition of early stages of autophagy, but not late stages of autophagy, ablated this interaction and inhibited apoptosis. Furthermore, DIABLO/SMAC mimetic-mediated apoptosis of HIV-Mφ is dependent upon tumor necrosis factor signaling. Our findings thus demonstrate that DIABLO/SMAC mimetics selectively induce autophagy-dependent apoptosis in HIV-Mφ.

Neurologic Complications of Acute HIV Infection

Purpose of Review

This review focuses on the pathophysiology of acute HIV infection (AHI) and related central nervous system (CNS) pathology, the clinical characteristics of neurologic complications of AHI, and the implications of the CNS reservoir and viral escape for HIV treatment and cure strategies.

Recent Findings

Recent studies in newly seroconverted populations show a high prevalence of peripheral neuropathy and cognitive dysfunction in AHI, even though these findings have been classically associated with chronic HIV infection. HIV cure strategies such as the "shock and kill" strategy are currently being studied in vitro and even in small clinical trials, though the CNS as a reservoir for latent HIV poses unique barriers to these treatment strategies.

Summary

Limited point of care diagnostic testing for AHI and delayed recognition of infection continue to lead to under-recognition and under-reporting of neurologic manifestations of AHI. AHI should be on the differential for a broad range of neurological conditions, from Bell's palsy, peripheral neuropathy, and aseptic meningitis, to more rare manifestations such as ADEM, AIDP, meningo-radiculitis, transverse myelitis, and brachial neuritis. Treatment for these conditions involves early initiation of antiretroviral therapy (ART) and then standard presentation-specific treatments. Current HIV cure strategies under investigation include bone marrow transplant, viral reservoir re-activation and eradication, and genome and epigenetic viral targeting. However, CNS penetration by HIV-1 occurs early on in the disease course with the establishment of the CNS viral reservoir and is an important limiting factor for these therapies.

Reduce and Control: A Combinatorial Strategy for Achieving Sustained HIV Remissions in the Absence of Antiretroviral Therapy

Human immunodeficiency virus (HIV-1) indefinitely persists, despite effective antiretroviral therapy (ART), within a small pool of latently infected cells. These cells often display markers of immunologic memory and harbor both replication-competent and -incompetent proviruses at approximately a 1:100 ratio. Although complete HIV eradication is a highly desirable goal, this likely represents a bridge too far for our current and foreseeable technologies. A more tractable goal involves engineering a sustained viral remission in the absence of ART––a “functional cure.” In this setting, HIV remains detectable during remission, but the size of the reservoir is small and the residual virus is effectively controlled by an engineered immune response or other intervention. Biological precedence for such an approach is found in the post-treatment controllers (PTCs), a rare group of HIV-infected individuals who, following ART withdrawal, do not experience viral rebound. PTCs are characterized by a small reservoir, greatly reduced inflammation, and the presence of a poorly understood immune response that limits viral rebound. Our goal is to devise a safe and effective means for replicating durable post-treatment control on a global scale. This requires devising methods to reduce the size of the reservoir and to control replication of this residual virus. In the following sections, we will review many of the approaches and tools that likely will be important for implementing such a “reduce and control” strategy and for achieving a PTC-like sustained HIV remission in the absence of ART.

The inhibitor of apoptosis proteins antagonist Debio 1143 promotes the PD-1 blockade-mediated HIV load reduction in blood and tissues of humanized mice

The immune checkpoint programmed cell death protein 1 (PD-1) plays a major role in T cell exhaustion in cancer and chronic HIV infection. The inhibitor of apoptosis protein antagonist Debio 1143 (D1143) enhances tumor cell death and synergizes with anti-PD-1 agents to promote tumor immunity and displayed HIV latency reversal activity in vitro. We asked in this study whether D1143 would stimulate the potency of an anti-human PD-1 monoclonal antibody (mAb) to reduce HIV loads in humanized mice. Anti-PD-1 mAb treatment decreased PD-1+ CD8+ cell population by 32.3% after interruption of four weeks treatment, and D1143 co-treatment further reduced it from 32.3 to 73%. Anti-PD-1 mAb administration reduced HIV load in blood by 94%, and addition of D1143 further enhanced this reduction from 94 to 97%. D1143 also more profoundly promoted with the anti-PD-1-mediated reduction of HIV loads in all tissues analyzed including spleen (71 to 96.4%), lymph nodes (64.3 to 80%), liver (64.2 to 94.4), lung (64.3 to 80.1%) and thymic organoid (78.2 to 98.2%), achieving a >5 log reduction of HIV loads in CD4+ cells isolated from tissues 2 weeks after drug treatment interruption. Ex vivo anti-CD3/CD28 stimulation increased the ability to activate exhausted CD8+ T cells in infected mice having received in vivo anti-PD-1 treatment by 7.9-fold (5 to 39.6%), and an additional increase by 1.7-fold upon D1143 co-treatment (39.6 to 67.3%). These findings demonstrate for the first time that an inhibitor of apoptosis protein antagonist enhances in a statistically manner the effects of an immune check point inhibitor on antiviral immunity and on HIV load reduction in tissues of humanized mice, suggesting that the combination of two distinct classes of immunomodulatory agents constitutes a promising anti-HIV immunotherapeutic approach.

Strategies to eradicate HIV from infected patients: elimination of latent provirus reservoirs

35 years since identification of HIV as the causative agent of AIDS, and 35 million deaths associated with this disease, significant effort is now directed towards the development of potential cures. Current anti-retroviral (ART) therapies for HIV/AIDS can suppress virus replication to undetectable levels, and infected individuals can live symptom free so long as treatment is maintained. However, removal of therapy allows rapid re-emergence of virus from a highly stable reservoir of latently infected cells that exist as a barrier to elimination of the infection with current ART. Prospects of a cure for HIV infection are significantly encouraged by two serendipitous cases where individuals have entered remission following stem cell transplantation from compatible HIV-resistant donors. However, development of a routine cure that could become available to millions of infected individuals will require a means of specifically purging cells harboring latent HIV, preventing replication of latent provirus, or destruction of provirus genomes by gene editing. Elimination of latently infected cells will require a means of exposing this population, which may involve identification of a natural specific biomarker or therapeutic intervention to force their exposure by reactivation of virus expression. Accordingly, the proposed "Shock and Kill" strategy involves treatment with latency-reversing agents (LRA) to induce HIV provirus expression thus exposing these cells to killing by cellular immunity or apoptosis. Current efforts to enable this strategy are directed at developing improved combinations of LRA to produce broad and robust induction of HIV provirus and enhancing the elimination of cells where replication has been reactivated by targeted immune modulation. Alternative strategies may involve preventing re-emergence virus from latently infected cells by "Lock and Block" intervention, where transcription of provirus is inhibited to prevent virus spread or disruption of the HIV provirus genome by genome editing.

A broad drug arsenal to attack a strenuous latent HIV reservoir

HIV cure is impeded by the persistence of a strenuous reservoir of latent but replication competent infected cells, which remain unsusceptible to c-ART and unrecognized by the immune system for elimination. Ongoing progress in understanding the molecular mechanisms that control HIV transcription and latency has led to the development of strategies to either permanently inactivate the latent HIV infected reservoir of cells or to stimulate the virus to emerge out of latency, coupled to either induction of death in the infected reactivated cell or its clearance by the immune system. This review focuses on the currently explored and non-exclusive pharmacological strategies and their molecular targets that 1. stimulate reversal of HIV latency in infected cells by targeting distinct steps in the HIV-1 gene expression cycle, 2. exploit mechanisms that promote cell death and apoptosis to render the infected cell harboring reactivated virus more susceptible to death and/or elimination by the immune system, and 3. permanently inactivate any remaining latently infected cells such that c-ART can be safely discontinued.