Clearance of HIV infection by selective elimination of host cells capable of producing HIV

Humanized mice for studying HIV latency and potentially its eradication

PURPOSE OF THE REVIEW

The quest for an HIV cure faces a formidable challenge: the persistent presence of latent viral infections within the cells and tissues of infected individuals. This review provides a thorough examination of discussions surrounding HIV latency, the use of humanized mouse models, and strategies aimed at eliminating the latent HIV reservoir. It explores the hurdles and advancements in understanding HIV pathogenesis, mainly focusing on establishing latent reservoirs in CD4 + T cells and macrophages. Introducing the concepts of functional and sterile cures, the review underscores the indispensable role of humanized mouse models in HIV research, offering crucial insights into the efficacy of cART and the ongoing pursuit of an HIV cure.

RECENT FINDINGS

Here, we highlight studies investigating molecular mechanisms and pathogenesis related to HIV latency in humanized mice and discuss novel strategies for eradicating latent HIV. Emphasizing the importance of analytical cART interruption in humanized mouse studies to gauge its impact on the latent reservoir accurately, the review underlines the ongoing progress and challenges in harnessing humanized mouse models for HIV research.

SUMMARY

This review suggests that humanized mice models provide valuable insights into HIV latency and potential eradication strategies, contributing significantly to the quest for an HIV cure.

Friends and Foes: The Ambivalent Role of Autophagy in HIV-1 Infection

Autophagy has emerged as an integral part of the antiviral innate immune defenses, targeting viruses or their components for lysosomal degradation. Thus, successful viruses, like pandemic human immunodeficiency virus 1 (HIV-1), evolved strategies to counteract or even exploit autophagy for efficient replication. Here, we provide an overview of the intricate interplay between autophagy and HIV-1. We discuss the impact of autophagy on HIV-1 replication and report in detail how HIV-1 manipulates autophagy in infected cells and beyond. We also highlight tissue and cell-type specifics in the interplay between autophagy and HIV-1. In addition, we weigh exogenous modulation of autophagy as a putative double-edged sword against HIV-1 and discuss potential implications for future antiretroviral therapy and curative approaches. Taken together, we consider both antiviral and proviral roles of autophagy to illustrate the ambivalent role of autophagy in HIV-1 pathogenesis and therapy.

Pharmacological approaches to promote cell death of latent HIV reservoirs

PURPOSE OF REVIEW

HIV requires lifelong antiviral treatment due to the persistence of a reservoir of latently infected cells. Multiple strategies have been pursued to promote the death of infected cells.

RECENT FINDINGS

Several groups have focused on multipronged approaches to induce apoptosis of infected cells. One approach is to combine latency reversal agents with proapoptotic compounds and cytotoxic T cells to first reactivate and then clear infected cells. Other strategies include using natural killer cells or chimeric antigen receptor cells to decrease the size of the reservoir.A novel strategy is to promote cell death by pyroptosis. This mechanism relies on the activation of the caspase recruitment domain-containing protein 8 (CARD8) inflammasome by the HIV protease and can be potentiated by nonnucleoside reverse transcriptase inhibitors.

SUMMARY

The achievement of a clinically significant reduction in the size of the reservoir will likely require a combination strategy since none of the approaches pursued so far has been successful on its own in clinical trials. This discrepancy between promising in vitro findings and modest in vivo results highlights the hurdles of identifying a universally effective strategy given the wide heterogeneity of the HIV reservoirs in terms of tissue location, capability to undergo latency reversal and susceptibility to cell death.

The integrated stress response signaling during the persistent HIV infection

Human immunodeficiency virus-1 (HIV) infection is a chronic disease under antiretroviral therapy (ART), during which active HIV replication is effectively suppressed. Stable viral reservoirs are established early in infection and cannot be eradicated in people with HIV (PWH) by ART alone, which features residual immune inflammation with disease-associated secondary comorbidities. Mammalian cells are equipped with integrated stress response (ISR) machinery to detect intrinsic and extrinsic stresses such as heme deficiency, nutrient fluctuation, the accumulation of unfolded proteins, and viral infection. ISR is the part of the innate immunity that defends against pathogen infection or environmental alteration, thereby maintaining homeostasis to avoid diseases. Here, we describe how this machinery responds to the off-target effects of ART and persistent HIV infection in both the peripheral compartments and the brain. The latter may be important for us to better understand the mechanisms of stable HIV reservoirs and HIV-associated neurocognitive disorders.

Targeting HIV-1 reservoirs in T cell subsets

The HIV-1 reservoirs harbor the latent proviruses that are integrated into the host genome. It is a challenging task to eradicate the proviruses in order to achieve an HIV cure. We have described a strategy for the clearance of HIV-1 infection through selective elimination of host cells harboring replication-competent HIV (SECH), by inhibition of autophagy and promotion of apoptosis during viral re-activation. HIV-1 can infect various CD4+ T cell subsets, but it is not known whether the SECH approach is equally effective in targeting HIV-1 reservoirs in these different subsets in vivo. In a humanized mouse model, we found that treatments of HIV-1 infection by suppressive antiretroviral therapy (ART) led to the establishment of latent HIV reservoirs in naïve, central memory and effector memory T cells. Moreover, SECH treatments could clear latent HIV-1 reservoirs in these different T cell subsets of humanized mice. Co-culture studies showed that T cell subsets latently infected by HIV-1, but not uninfected bystander cells, were susceptible to cell death induced by SECH treatments. Our study suggests that the SECH strategy is effective for specific targeting of latent HIV-1 reservoirs in different T cell subsets.

Clearance of HIV-1 or SIV reservoirs by promotion of apoptosis and inhibition of autophagy: Targeting intracellular molecules in cure-directed strategies

The reservoirs of the HIV display cellular properties resembling long-lived immune memory cells that could be exploited for viral clearance. Our interest in developing a cure for HIV stems from the studies of immunologic memory against infections. We and others have found that long-lived immune memory cells employ prosurvival autophagy and antiapoptotic mechanisms to protect their longevity. Here, we describe the rationale for the development of an approach to clear HIV-1 by selective elimination of host cells harboring replication-competent HIV (SECH). While reactivation of HIV-1 in the host cells with latency reversing agents (LRAs) induces viral gene expression leading to cell death, LRAs also simultaneously up-regulate prosurvival antiapoptotic molecules and autophagy. Mechanistically, transcription factors that promote HIV-1 LTR-directed gene expression, such as NF-κB, AP-1, and Hif-1α, can also enhance the expression of cellular genes essential for cell survival and metabolic regulation, including Bcl-xL, Mcl-1, and autophagy genes. In the SECH approach, we inhibit the prosurvival antiapoptotic molecules and autophagy induced by LRAs, thereby allowing maximum killing of host cells by the induced HIV-1 proteins. SECH treatments cleared HIV-1 infections in humanized mice in vivo and in HIV-1 patient PBMCs ex vivo. SECH also cleared infections by the SIV in rhesus macaque PBMCs ex vivo. Research efforts are underway to improve the efficacy and safety of SECH and to facilitate the development of SECH as a therapeutic approach for treating people with HIV.

Current strategies to induce selective killing of HIV-1-infected cells

Although combination antiretroviral therapy (ART) has led to significant HIV-1 suppression and improvement in immune function, persistent viral reservoirs remain that are refractory to intensified ART. ART poses many challenges such as adherence to drug regimens, the emergence of resistant virus, and cumulative toxicity resulting from long-term therapy. Moreover, latent HIV-1 reservoir cells can be stochastically activated to produce viral particles despite effective ART and contribute to the rapid viral rebound that typically occurs within 2 weeks of ART interruption; thus, lifelong ART is required for continued viral suppression. Several strategies have been proposed to address the HIV-1 reservoir such as reactivation of HIV-1 transcription using latency reactivating agents with a combination of ART, host immune clearance and HIV-1-cytotoxicity to purge the infected cells-a "shock and kill" strategy. However, these approaches do not take into account the multiple transcriptional and translational blocks that contribute to HIV-1 latency or the complex heterogeneity of the HIV-1 reservoir, and clinical trials have thus far failed to produce the desired results. Here, we describe alternative strategies being pursued that are designed to kill selectively HIV-1-infected cells while sparing uninfected cells in the absence of enhanced humoral or adaptive immune responses.

Genome-wide CRISPR screens identify combinations of candidate latency reversing agents for targeting the latent HIV-1 reservoir

Reversing HIV-1 latency promotes killing of infected cells and is essential for cure strategies; however, no single latency reversing agent (LRA) or LRA combination have been shown to reduce HIV-1 latent reservoir size in persons living with HIV-1 (PLWH). Here, we describe an approach to systematically identify LRA combinations to reactivate latent HIV-1 using genome-wide CRISPR screens. Screens on cells treated with suboptimal concentrations of an LRA can identify host genes whose knockout enhances viral gene expression. Therefore, inhibitors of these genes should synergize with the LRA. We tested this approach using AZD5582, an activator of the noncanonical nuclear factor κB (ncNF-κB) pathway, as an LRA and identified histone deacetylase 2 (HDAC2) and bromodomain-containing protein 2 (BRD2), part of the bromodomain and extra-terminal motif (BET) protein family targeted by BET inhibitors, as potential targets. Using CD4⁺ T cells from PLWH, we confirmed synergy between AZD5582 and several HDAC inhibitors and between AZD5582 and the BET inhibitor, JQ1. A reciprocal screen using suboptimal concentrations of an HDAC inhibitor as an LRA identified BRD2 and ncNF-κB regulators, especially BIRC2, as synergistic candidates for use in combination with HDAC inhibition. Moreover, we identified and validated additional synergistic drug candidates in latency cell line cells and primary lymphocytes isolated from PLWH. Specifically, the knockout of genes encoding CYLD or YPEL5 displayed synergy with existing LRAs in inducing HIV mRNAs. Our study provides insights into the roles of host factors in HIV-1 reactivation and validates a system for identifying drug combinations for HIV-1 latency reversal.

Autophagy in health and disease: From molecular mechanisms to therapeutic target

Macroautophagy/autophagy is an evolutionally conserved catabolic process in which cytosolic contents, such as aggregated proteins, dysfunctional organelle, or invading pathogens, are sequestered by the double‐membrane structure termed autophagosome and delivered to lysosome for degradation. Over the past two decades, autophagy has been extensively studied, from the molecular mechanisms, biological functions, implications in various human diseases, to development of autophagy‐related therapeutics. This review will focus on the latest development of autophagy research, covering molecular mechanisms in control of autophagosome biogenesis and autophagosome–lysosome fusion, and the upstream regulatory pathways including the AMPK and MTORC1 pathways. We will also provide a systematic discussion on the implication of autophagy in various human diseases, including cancer, neurodegenerative disorders (Alzheimer disease, Parkinson disease, Huntington's disease, and Amyotrophic lateral sclerosis), metabolic diseases (obesity and diabetes), viral infection especially SARS‐Cov‐2 and COVID‐19, cardiovascular diseases (cardiac ischemia/reperfusion and cardiomyopathy), and aging. Finally, we will also summarize the development of pharmacological agents that have therapeutic potential for clinical applications via targeting the autophagy pathway. It is believed that decades of hard work on autophagy research is eventually to bring real and tangible benefits for improvement of human health and control of human diseases.

Trace element homeostasis in the neurological system after SARS-CoV-2 infection: Insight into potential biochemical mechanisms

BACKGROUND

Several studies have suggested that COVID-19 is a systemic disease that can affect several organs, including the brain. In the brain, specifically, viral infection can cause dyshomeostasis of some trace elements that promote complex biochemical reactions in specialized neurological functions.

OBJECTIVE

Understand the neurovirulence of SARS-CoV-2 and the relationship between trace elements and neurological disorders after infection, and provide new insights on the drug development for the treatment of SARS-CoV-2 infections.

METHODS

The main databases were used to search studies published up September 2021, focusing on the role of trace elements during viral infection and on the correct functioning of the brain.

RESULTS

The imbalance of important trace elements can accelerate SARS-CoV-2 neurovirulence and increase the neurotoxicity since many neurological processes can be associated with the homeostasis of metal and metalloproteins. Some studies involving animals and humans have suggested the synapse as a vulnerable region of the brain to neurological disorders after viral infection. Considering the combined evidence, some mechanisms have been suggested to understand the relationship between neurological disorders and imbalance of trace elements in the brain after viral infection.

CONCLUSION

Trace elements play important roles in viral infections, such as helping to activate immune cells, produce antibodies, and inhibit virus replication. However, the relationship between trace elements and virus infections is complex since the specific functions of several elements remain largely undefined. Therefore, there is still a lot to be explored to understand the biochemical mechanisms involved between trace elements and viral infections, especially in the brain.

Understanding the relationship between viral infections and trace elements from a metallomics perspective: implications for COVID-19

Recently, the World Health Organization (WHO) declared a pandemic situation due to a new viral infection (COVID-19) caused by a novel virus (Sars-CoV-2). COVID-19 is today the leading cause of death from viral infections in the world. It is known that many elements play important roles in viral infections, both in virus survival, and in the activation of the host's immune system, which depends on the presence of micronutrients to maintain the integrity of its functions. In this sense, the metallome can be an important object of study for understanding viral infections. Therefore, this work presents an overview of the role of trace elements in the immune system and the state of the art in metallomics, highlighting the challenges found in studies focusing on viral infections.

Nanosystems Applied to HIV Infection: Prevention and Treatments

Sexually-transmitted infections (STIs) are a global health concern worldwide as they cause acute diseases, infertility, and significant mortality. Among the bacterial, viral, and parasitic pathogens that can be sexually transmitted, human immunodeficiency virus (HIV) has caused one of the most important pandemic diseases, which is acquired immune deficiency syndrome (AIDS). 32.7 million people have died from AIDS-related illnesses since the start of the epidemic. Moreover, in 2019, 38 million people were living with HIV worldwide. The need to deal with this viral infection becomes more obvious, because it represents not only a problem for public health, but also a substantial economic problem. In this context, it is necessary to focus efforts on developing methods for prevention, detection and treatment of HIV infections that significantly reduce the number of newly infected people and provide a better quality of life for patients. For several decades, biomedical research has been developed allowing quick solutions through the contribution of effective tools. One of them is the use of polymers as vehicles, drug carrier agents, or as macromolecular prodrugs. Moreover, nanosystems (NSs) play an especially important role in the diagnosis, prevention, and therapy against HIV infection. The purpose of this work is to review recent research into diverse NSs as potential candidates for prevention and treatment of HIV infection. Firstly, this review highlights the advantages of using nanosized structures for these medical applications. Furthermore, we provide an overview of different types of NSs used for preventing or combating HIV infection. Then, we briefly evaluate the most recent developments associated with prevention and treatment alternatives. Additionally, the implications of using different NSs are also addressed.