key: cord-0951379-gj6po1rl
authors: Campbell, Grant R.; Spector, Stephen A.
title: Induction of Autophagy to Achieve a Human Immunodeficiency Virus Type 1 Cure
date: 2021-07-16
journal: Cells
DOI: 10.3390/cells10071798
sha: ce04d25f4eccd0af900ed7aa39cffc95466707de
doc_id: 951379
cord_uid: gj6po1rl

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.

Within days of infection, human immunodeficiency virus type 1 (HIV-1) rapidly disseminates to draining lymph nodes. HIV-1 advances to destroy helper T cells and establish latent HIV-1 reservoirs through the irreversible integration of replication-competent proviral DNA into the genome of resting CD4 + T cells, hematopoietic stem cells, cells from the monocyte-macrophage lineage, and microglia [1] [2] [3] [4] [5] . Although antiretroviral therapy (ART) has transformed HIV-1 infection from a lethal and destructive disease into a controllable, but chronic condition, the establishment of HIV-1 latency is unaffected by early initiation of ART [6] , and there is no evidence that ART alone is able to eradicate latent HIV-1 [7, 8] . Moreover, although ART effectively suppresses HIV-1 replication, persistent residual lowlevel viremia maintains the latent pool [9, 10] , and the very low expression of viral proteins enables latently infected cells to evade detection and clearance by the immune system and undergo homeostatic proliferation [11] [12] [13] [14] [15] . Additionally, as viral loads rebound to high pre-therapy levels following ART interruption, albeit with significant heterogeneity in the speed of viral rebound (days, weeks, or sometimes years [16, 17] ), lifelong ART is required for continued viral suppression. Therefore, these latent cellular reservoirs present the major obstacle in preventing the eradication of HIV-1. phosphate (PI3P) which subsequently recruits PI3P-binding proteins, such as WIPI2 and ZFYVE1 [85] . The recruitment of these proteins results in the formation of phagophores, which expand and close through membrane scission forming autophagosomes [86] . The precise mechanisms(s) by which this occurs are not completely known. However, current research suggests that it involves two ubiquitin-like conjugation systems. The first entails the E1-like enzyme ATG7 and the E2-like enzyme ATG3 conjugating the ubiquitinlike ATG8 family proteins (microtubule-associated protein 1 light chain 3 [MAP1LC3 or more commonly LC3] A, LC3B, LC3B2, LC3C, GABARAP [GABA type A receptor associated protein], GABARAP-like [GABARAPL] 1 and GABARAPL2) to the headgroups of membrane lipid phosphatidylethanolamine (PE). The second involves the recruitment of the E3-like ATG12-ATG5-ATG16L1 complex to PI3P-containing phagophores by the WIPI2b isoform. The ATG12-ATG5-ATG16L1 complex then ligates ATG8-PE to nascent autophagosome membranes where they can interact with cargo receptors harbouring LC3interacting regions (LIRs; a conserved sequence W/F/YxxL/I/V) [85] . ATG16L1, as well as the polyubiquitin-binding autophagy receptors including sequestosome 1 (SQSTM1, p62), optineurin (OPTN), NBR1, and NDP52, which harbour both Ub-binding domains and LIRs also recruit and incorporate ubiquitin-decorated cargos into autophagosomes [87] . After detachment of ATG factors, the isolation membrane closes and syntaxin 17 is recruited to the autophagosomes. These then fuse with lysosomes resulting in the degradation of the engulfed components as well as the ATG8-PE and SQSTM1 associated with the inner membrane [88] . As autophagy is a coordinated pathway of autophagosome formation, sequestration of autophagic cargo, autophagosome-lysosome fusion, followed by the proteolytic degradation of the sequestered cargo, dysregulation or inhibition of any step could lead to the failure of the autophagy cycle that could lead to a disturbance of cellular homeostasis leading to cell death. As an example, inhibition of autophagy by blocking lysosomal degradation can lead to the accumulation of autophagosomes, thus depleting membrane sources. 14 . This complex translocates to ER sites and produces phosphatidylinositol 3phosphate (PI3P) which subsequently recruits PI3P-binding proteins, such as WIPI2 and ZFYVE1 [85] . The recruitment of these proteins results in the formation of phagophores, which expand and close through membrane scission forming autophagosomes [86] . The precise mechanisms(s) by which this occurs are not completely known. However, current research suggests that it involves two ubiquitin-like conjugation systems. [85] . ATG16L1, as well as the polyubiquitin-binding autophagy receptors including sequestosome 1 (SQSTM1, p62), optineurin (OPTN), NBR1, and NDP52, which harbour both Ub-binding domains and LIRs also recruit and incorporate ubiquitin-decorated cargos into autophagosomes [87] . After detachment of ATG factors, the isolation membrane closes and syntaxin 17 is recruited to the autophagosomes. These then fuse with lysosomes resulting in the degradation of the engulfed components as well as the ATG8-PE and SQSTM1 associated with the inner membrane [88] . As autophagy is a coordinated pathway of autophagosome formation, sequestration of autophagic cargo, autophagosome-lysosome fusion, followed by the proteolytic degradation of the sequestered cargo, dysregulation or inhibition of any step could lead to the failure of the autophagy cycle that could lead to a disturbance of cellular homeostasis leading to cell death. As an example, inhibition of autophagy by blocking lysosomal degradation can lead to the accumulation of autophagosomes, thus depleting membrane sources. The initiation of autophagy is a multistep process. The main regulators of autophagy are MTOR, an inhibitor, and AMP-activated kinase (AMPK) an activator. MTORC1 inhibition induces autophagy through the formation of the ULK1 complex. This complex initiates the formation of the phagophore by directly activating the phosphatidylinositol 3kinase catalytic subunit type 3 complex I (PIK3C3 complex). The PIK3C3 complex translocates to endoplasmic reticulum sites and produces phosphatidylinositol 3-phosphate (PI3P) which then recruits PI3P-binding proteins such as WIPI2 and ZFYVE1. HIV-1 Nef can inhibit this process by enhancing the association between BECN1 and its inhibitor BCL2. In the ATG12 conjugation system, ATG12 forms a covalent bond with ATG5, which then binds ATG16L1, followed by dimerization (not shown) and interaction with the PI3P-binding complex. The WIPI2b isoform acts immediately upstream of ATG16L1 and recruits ATG12-ATG5-ATG16L1 to PI3P-containing phagophores. The ATG12-ATG5-ATG16L1 complex Figure 1 . The initiation of autophagy is a multistep process. The main regulators of autophagy are MTOR, an inhibitor, and AMP-activated kinase (AMPK) an activator. MTORC1 inhibition induces autophagy through the formation of the ULK1 complex. This complex initiates the formation of the phagophore by directly activating the phosphatidylinositol 3-kinase catalytic subunit type 3 complex I (PIK3C3 complex). The PIK3C3 complex translocates to endoplasmic reticulum sites and produces phosphatidylinositol 3-phosphate (PI3P) which then recruits PI3P-binding proteins such as WIPI2 and ZFYVE1. HIV-1 Nef can inhibit this process by enhancing the association between BECN1 and its inhibitor BCL2. In the ATG12 conjugation system, ATG12 forms a covalent bond with ATG5, which then binds ATG16L1, followed by dimerization (not shown) and interaction with the PI3P-binding complex. The WIPI2b isoform acts immediately upstream of ATG16L1 and recruits ATG12-ATG5-ATG16L1 to PI3P-containing phagophores. The ATG12-ATG5-ATG16L1 complex then promotes conjugation of ATG8 family proteins with phosphatidylethanolamine (PE), which are then incorporated into phagophore membranes, where they interact with cargo receptors harbouring LC3-interacting motifs. ATG16L1, as well as the polyubiquitin-binding autophagy receptors including SQSTM1, OPTN, NBR1, and NDP52 also recruit and incorporate ubiquitin-decorated cargos into autophagosomes including HIV-1 Tat, HIV-1 Vif, and HIV-1 p24. After detachment of ATG factors, the isolation membrane closes through membrane scission, forming the autophagosome. These, then, fuse with lysosomes resulting in the degradation of the engulfed components as well as the ATG8-PE and SQSTM1 associated with the inner membrane.

HIV-1 Nef affects autophagosome maturation by preventing the fusion between autophagosomes and lysosomes.

Host cells can recognise microorganism-specific pathogen-associated molecular pattern (PAMP) molecules through pattern recognition receptors (PRR). These PRR include toll-like receptors (TLR), RIG-I-like receptors (RLR), nucleotide oligomerization domain (NOD)-like receptors (NLR), and C-type lectin receptors (CLR). The most studied PRR in relation to autophagy are the TLR. Humans have 10 TLRs, each recognizing a different PAMP, and are present in many different cell types including CD4 + T cells and macrophages. TLRs 1, 2, 4, 5, 6, and 10 are located at the plasma membrane and recognise bacterial membrane components, whereas TLRs 3, 7, 8, and 9 are predominantly located within endosomes. The phylogenetically and structurally related TLR7/8 recognise GU-rich short single-stranded microbial RNA, such as that found in the U5 region of the HIV-1 genome [89, 90] . HIV-1-Env-CD4 interactions mediates the endocytosis of HIV-1 that delivers viral genomic RNA to the endosomal TLR7/8 [91, 92] . In addition to mediating the endocytosis of HIV-1, in dendritic cells, HIV-1 Env also activates and exhausts autophagy leading to a rapid shutdown of both autophagy and immunoamphisome production. This results in an increase in both cell-associated HIV-1 and transfer of HIV-1 to CD4 + T cells while also impairing both the innate and adaptive immune responses as autophagy interacts with the MHC-II loading machinery [93, 94] . Upon ligand activation, TLR8 associates and interacts with the adapter protein MYD88 that recruits IL-1 receptor-associated kinases, leading to the NF-κB-dependent transcription of numerous pro-inflammatory mediators including IL-6, IL-12, IL-27, TNF, interferon (IFN) γ, and IL-1β in the absence of pyroptosis [95] [96] [97] [98] . Crucially, the NLRP3-inflammasome induced secretion of IL-1β is dependent upon intact autophagy [98, 99] . Similarly, exposure of plasmacytoid dendritic cells (pDCs) to infectious or non-infectious HIV-1 or to HIV-1 derived GU-rich HIV-1 RNA sequences induces IFNα production through a TLR7-and autophagy-dependent mechanism [91, 100] . In addition to stimulating the release of pro-inflammatory cytokines, TLR7/8 ligation also suppresses HIV-1 replication in acute ex vivo human lymphoid tissue of tonsillar origin and renders peripheral blood mononuclear cells (PBMC) barely permissive to HIV-1 infection [101] . Further studies demonstrated that binding of TLR8 by GU-rich HIV-1 RNA sequences induces autophagy through a cathelicidin antimicrobial peptide and vitamin D-dependent mechanism [92, 102] , and decreases HIV-1 p24 release from HIV-1 infected macrophages through an autophagy and lysosome dependent mechanism [92, 102] . Interestingly, HIV-1 downregulates IRAK4, which is essential for virtually all TLR signalling [103] . People living with HIV-1 (PLWH) have lower levels of vitamin D3 than uninfected individuals [104] [105] [106] [107] [108] [109] [110] [111] . Additionally, the concentrations of vitamin D3 decrease during HIV-1 disease progression and correlate with increased markers of inflammation and decreased autophagy and survival rates [110, 112, 113] . Vitamin D3 is a known autophagy inducer, and studies show that vitamin D3 decreases HIV-1 p24 release from HIV-1 infected macrophages through an autophagy-dependent mechanism [114] .

One of the first HIV-1 restriction factors identified was the PRR TRIM5α, which interacts with retroviral capsid proteins in the context of an intact core structure. Although TRIM5α was originally suggested to be a species-specific HIV-1 restriction factor, with rhesus TRIM5α but not human TRIM5α efficiently restricting HIV-1 infection by accelerating premature uncoating of the virus thereby inhibiting nuclear translocation and subsequent integration [115] [116] [117] , recent literature indicates that human TRIM5α also acts Cells 2021, 10, 1798 6 of 21 as an HIV-1 restriction factor through a different mechanism. While HIV-1 binding to DC-SIGN (CD209) positive dendritic cells leads to disassociation of TRIM5α from CD209, in Langerhans cells, TRIM5α mediates the assembly of an autophagy-activating scaffold to the CLR langerin (CD207), and acts as a receptor for selective autophagic degradation of HIV-1 proteins [118] [119] [120] [121] . Moreover, the TRIM5α-HIV-1 p24 binding promotes the synthesis of unattached K63-linked ubiquitin chains that promotes the recruitment and activation of the MAP3K7-TAB complex in an autophagy-dependent mechanism, leading to the transcription and secretion of cytokines including interferon α/β and IL-6 [118, 122, 123] . Interestingly, TRIM5α expression is increased in PBMC from long-term non-progressors, and this increase correlates with an increase in HIV-1 gp120 and TRIM5α co-localization in autophagic vacuoles compared with PBMC from typical progressors [124] .

Although Sagnier et al. [64] suggested that autophagy selectively degrades HIV-1 Tat through a ubiquitin-independent interaction with SQSTM1, Xu et al. demonstrated that HIV-1 Tat undergoes K63-polyubiquitination, a mark recognised by SQSTM1 and the NBR1 autophagy cargo receptor [125] [126] [127] , complexes with the CMA-specific chaperone HSPA8 and is subjected to K63Ub-selective autophagy mediated by serine hydroxymethyltransferase (SHMT) 1, SHMT2 and the BRCC36/BRISC deubiquitase complex [65] .

During HIV-1 infection, the cellular restriction factor APOBEC3G restricts HIV-1 replication through the specific deamination of dCs in newly synthesised (−)-strand viral DNA, resulting in massive G-to-A invalidating hypermutations in the nascent (+)-strand viral DNA genome during reverse transcription. In addition, APOBEC3G also directly blocks reverse transcriptase elongation in a deaminase-independent manner and interferes with the integration of proviral DNA. HIV-1 Vif antagonises the APOBEC3G-mediated host defence system by recruiting APOBEC3G into the E3 ubiquitin ligase complex, thus promoting APOBEC3G degradation through the ubiquitin-proteasome pathway. However, through its C-terminal ubiquitin-binding BUZ (binder of ubiquitin zinc finger) domain, the host factor HDAC6 binds HIV-1 Vif and targets it for autophagic degradation [128] . HDAC6 is a central component of basal autophagy that promotes cortactin-dependent, actin-remodelling machinery to stimulate autophagosome-lysosome fusion and substrate degradation [129] , while also facilitating the transport of misfolded proteins to the aggresome [130] .

HIV-1 overcomes these innate host autophagic defences through HIV-1 Nef, which blocks autophagy initiation by enhancing the association between BECN1 and its inhibitor BCL2 in a PRKN-dependent mechanism. This blocking is done by inducing the cytoplasmic sequestration of TFEB, an upstream regulator of MTOR, and by affecting autophagosome maturation by preventing the fusion between autophagosomes and lysosomes ( Figure 1 ) [92, 131, 132] .

Although post-transcriptional regulation of HIV-1 latency is an important multifactorial process, current efforts to eradicate the latent HIV-1 reservoir pool focus on reactivating the transcription of latent HIV-1 proviruses. This approach uses latency-reversing agents (LRAs) followed by a combination of ART, with the expectation that targeted immunotherapy, host immune clearance, and HIV-1-cytolysis will be sufficient to kill latently infected cells expressing viral proteins-the "kick and kill" approach. The LRAs under investigation are various and include histone post-translational modification modulators, NF-κB stimulators, non-histone chromatin modulators, TLR agonists, and MTOR activators [133] . However, with over 160 LRA tested to date, none have shown great promise [133] . The most studied class of LRA are the histone post-translational modification modulators that include the histone deacetylase inhibitors (HDACi) givinostat, panobinostat, romidepsin, and vorinostat. Although these induce HIV-1 expression through the reversal of epigenetic silencing, they do not induce the expression of MATR3 [80] , resulting in insufficiently low levels of induced viral expression to cause viral cytopathicity, or their elimination by immune effectors such as cytotoxic T cells. Unfortunately, HDACi impair cytotoxic T cell and natural killer (NK) cell functions [134, 135] , while also promoting the infection of uninfected CD4 + T cells [136] .

The inhibitor of apoptosis protein (IAP) family members BIRC2 and BIRC3, are upregulated in latent HIV-1 infected cells [137] [138] [139] [140] and are important negative regulators of non-canonical NF-κB signalling, and thus 5 LTR-dependent HIV-1 transcription [141, 142] . DIABLO/SMAC mimetics mimic the BIR-binding N-terminal tetrapeptide sequence of DIABLO, a pro-apoptogenic mitochondrial protein released into the cytoplasm in response to apoptotic stimuli to antagonise IAPs. The interaction of DIABLO/SMAC mimetics with BIRC2 and BIRC3 activates their E3 ubiquitin ligase activity promoting their autoubiquitination and proteasomal degradation [143] [144] [145] . Depletion of BIRC2 using DIABLO/SMAC mimetics can activate non-canonical NF-κB signalling, and can act as a LRA in latent HIV-1 cell line models [140, 142, [146] [147] [148] [149] [150] [151] . However, only AZD5582, xevinapant, and ciapavir have shown this ability in primary cells, albeit with mixed efficacy, and none have been tested in PLWH.

Agonists against the endosomal TLR3, -7, and -9 have gone through clinical trials for LRA with mixed results [152] . In addition to this potential function, TLR agonists also enhance the generation of HIV-1-specific CD8 + T cells [153] , while activating proinflammatory and antimicrobial responses, including the NF-κB-dependent transcription of numerous proinflammatory mediators [154] and the induction of autophagy [155] . As the hyper-activation of MTORC1 by HIV-1 Tat is necessary for HIV-1 production [25], the activation of MTOR by tideglusib, a glycogen synthase kinase 3 inhibitor, was investigated. However, although tideglusib reactivated latent HIV-1 from ex vivo primary CD4 + T cells derived from PLWH on suppressive ART, tideglusib, like other LRAs, failed to reverse latency in vivo [156] .

These examples highlight the overall disconnect between the promising in vitro and ex vivo results of LRAs and the poor in vivo findings. Therefore, there is an urgent need for a new approach if a functional HIV-1 cure is to be achieved. In contrast to the "kick and kill" approach, the latency promoting "block and lock" approach is designed to repress HIV-1 expression and release it to levels that can be controlled and cleared by the immune system in the absence of ART-a state of deep latency [157, 158] . Deep latency is occasionally observed in some PLWH who are able to control viremia for several years after ART interruption despite possessing weak HIV-1-specific immune responses and low levels of pro-inflammatory markers [16, 17, 159, 160] . Although these post-treatment controllers have relatively small HIV-1 reservoirs, it is theorised that a "block and lock" approach could achieve a similar transcriptionally repressive profile in people initially starting with much larger HIV-1 reservoirs, which result in normal CD4 + T cell counts, the absence of disease progression, and no release of replication competent virus after ART interruption ( Figure 2 ). The "block and lock" approach has a number of advantages over the "kick and kill" approach. As the "block and lock" approach is designed to induce a state of deep latency, the safety concerns related to viral reactivation, drug resistance, and transmission associated with the "kick and kill" approach should be mitigated. Additionally, this approach could be affordable, permanent, and easily implemented in resource-limited settings. Moreover, even if the latency-promoting agents (LPA) in development fail to achieve a long-term functional cure, they could still be of clinical value as a potential new class of ART, as well as being used to uncouple HIV-1 transcription from immune system activation, enhancing clearance by the immune system.

As the control of HIV-1 Tat and P-TEFb translation, modification, turnover, and abundance are important regulators of both HIV-1 replication and latency, HIV-1 Tat, TAR RNA, and P-TEFb are all important targets for LPA development [161] . Unfortunately, the lack of specificity and/or poor pharmacokinetic properties hindered the early development of compounds targeting these proteins [162] [163] [164] [165] . Although these early compounds decreased gross HIV-1 transcription, they had no effect on the integrated pro-virus such that when inhibition was relieved, HIV-1 viremia rapidly rebounded [166, 167] . In contrast to these early attempts, an equipotent analogue of the steroidal alkaloid cortistatin A, didehydro- [168, 169] , disrupting the HIV-1 transactivation positive feedback loop, while also instigating the progressive accrual of epigenetic modifications along the HIV-1 5 LTR. This results in a repressive heterochromatin environment that epigenetically silences the HIV-1 promoter [59, [170] [171] [172] [173] , even in the presence of an LRA [171] . Other recent promising LPA targeting the HIV-1 Tat/P-TEFb nexus include spironolactone [174] , HEXIM1-Tat peptide [175] , the BRD4 inhibitor ZL0580 [176, 177] , and Nullbasic, a 101 amino acid trans-dominant negative HIV-1 BH10 Tat in which G/A residues replace the entire basic domain [178] [179] [180] [181] . As the control of HIV-1 Tat and P-TEFb translation, modification, turnover, and abundance are important regulators of both HIV-1 replication and latency, HIV-1 Tat, TAR RNA, and P-TEFb are all important targets for LPA development [161] . Unfortunately, the lack of specificity and/or poor pharmacokinetic properties hindered the early development of compounds targeting these proteins [162] [163] [164] [165] . Although these early compounds decreased gross HIV-1 transcription, they had no effect on the integrated provirus such that when inhibition was relieved, HIV-1 viremia rapidly rebounded [166, 167] . In contrast to these early attempts, an equipotent analogue of the steroidal alkaloid cortistatin A, didehydro-cortistatin A (dCA), has shown promise. dCA binds to the TARbinding domain of HIV-1 Tat and blocks transcriptional elongation of the HIV-1 promoter [168, 169] , disrupting the HIV-1 transactivation positive feedback loop, while also instigating the progressive accrual of epigenetic modifications along the HIV-1 5′ LTR. This results in a repressive heterochromatin environment that epigenetically silences the HIV-1 promoter [59, [170] [171] [172] [173] , even in the presence of an LRA [171] . Other recent promising LPA targeting the HIV-1 Tat/P-TEFb nexus include spironolactone [174] , HEXIM1-Tat peptide [175] , the BRD4 inhibitor ZL0580 [176, 177] , and Nullbasic, a 101 amino acid trans-dominant negative HIV-1BH10 Tat in which G/A residues replace the entire basic domain [178] [179] [180] [181] .

Although LPA could function to a point where HIV-1 reactivation from latency is unlikely, these drugs do not induce the destruction of the latent reservoir. Unfortunately, the larger the expressed HIV-1 reservoir, the shorter the time to viral rebound after ART interruption [182] . Therefore, combining LPA with drugs that can specifically kill latent HIV-1 infected cells could be advantageous-a "kill, block and lock" (Figure 2d) . Although a number of pro-apoptotic compounds, including BCL2 antagonists, DDX3 inhibitors, PLK1 inhibitors, and RLR agonists have been assessed for their potential to specifi- Although LPA could function to a point where HIV-1 reactivation from latency is unlikely, these drugs do not induce the destruction of the latent reservoir. Unfortunately, the larger the expressed HIV-1 reservoir, the shorter the time to viral rebound after ART interruption [182] . Therefore, combining LPA with drugs that can specifically kill latent HIV-1 infected cells could be advantageous-a "kill, block and lock" (Figure 2d ). Although a number of pro-apoptotic compounds, including BCL2 antagonists, DDX3 inhibitors, PLK1 inhibitors, and RLR agonists have been assessed for their potential to specifically induce cell death of HIV-1-infected cells [183] [184] [185] [186] [187] , they all either require the addition of an LRA to specifically kill HIV-1 infected cells, or induce viral transcription themselves. Thus, they are incompatible with a "block and lock" approach. As the hyper-activation of MTORC1 by HIV-1 Tat is necessary for HIV-1 production [25] and the integrity and function of both MTORC1 and MTORC2 are essential in re-activating HIV-1 from latency [26,27], the inhibition of MTOR is an attractive target for LPA development. The potent and selective ATP-competitive second generation MTOR inhibitors torkinib, torin1, and sapanisertib all repress induced basal (HIV-1 Tat-independent) and (HIV-1 Tat-dependent) HIV-1 gene expression and the reactivation of HIV-1 from in vitro and in vivo models of HIV-1 latency, as well as ex vivo primary CD4+ T cells derived from PLWH on long-term suppressive ART [25, 26, 188] . Further supporting the use of MTOR inhibitors, the allosteric MTORC1 inhibitors, sirolimus and everolimus inhibit the production of fully infectious HIV-1 particles from a number of different cell types while also limiting intestinal HIV-1 transmission [114, [189] [190] [191] . Additionally, HIV-1-infected adult solid organ transplant recipients receiving these drugs better control HIV-1 replication versus patients receiving alternative immunosuppressants [192, 193] . Moreover, sirolimus synergistically enhances the activity of entry inhibitors, such as vicriviroc, aplaviroc and enfuvirtide [194] , and inhibits HIV-1 entry through the downregulation of CCR5 [194, 195] . Although these MTOR inhibition studies did not assess the role of autophagy, the inhibition of MTOR induces autophagy. Despite being a predominantly cell survival mechanism, under certain conditions autophagy, and the proteins associated with the autophagic process, can promote cell death [196, 197] . For instance, in combination with ART and ionizing radiation, sirolimus selectively kills HIV-1-infected myeloid and CD4+ T-cell reservoirs via the inhibition of viral transcription/translation and the induction of autophagy with no deleterious effect on uninfected bystander cells [198] .

Although HIV-1 Nef blocks autophagy initiation and autophagosome maturation, pharmacological inducers of autophagy such as sirolimus can overcome this block leading to the autophagic-degradation of HIV-1 capsid proteins and a decrease in released HIV-1 virions through an ATG5-and autophagy-dependent mechanism [114, 199] . Notably, in HIV-1-infected macrophages, the LRA HDACi vorinostat, panobinostat, givinostat and romidepsin and the non-histone chromatin modulating BET inhibitor JQ1 all inhibit MTOR through a yet unidentified mechanism, leading to the dose-dependent autophagic degradation of HIV-1 capsid proteins and a subsequent decrease in HIV-1 release in the absence of cell death [200, 201] . Similarly, the dual PI3K/MTOR inhibitor dactolisib (NVP-BEZ235), and the PI3K/MTOR/BRD4 inhibitor SF2523 all inhibit MTOR with similar autophagydependent decreases in both intracellular and extracellular HIV-1 p24 abundance in the absence of cell death [201] .

Further studies demonstrated that trehalose, a naturally occurring sugar, induces MTOR-dependent and MTOR-independent autophagy in HIV-1 infected macrophages and CD4 + T cells, leading to the degradation of intracellular HIV-1 capsid proteins and an autophagy-dependent reduction in HIV-1 release [202, 203] . Trehalose can also decrease HIV-1 entry through the downregulation of CD4 + expression on CD4 + T cells and macrophages and CCR5 on CD4 + T cells, thus, reducing transmission [202] . Interestingly, nelfinavir also inhibits MTOR through the upregulation of the MTOR inhibitor sestrin-2 (SESN2) resulting in autophagy induction [204] . Its role in HIV-1 restriction is yet to be pursued. Finally, the recent discovery of miRAB40, an autophagy-inducing, HIV-1inhibiting microRNA, may also provide insights into the microRNA-mediated regulation of autophagy-mediated HIV-1 inhibition [205] .

Although the autophagic degradation of HIV-1 does not have an effect on the transcriptionally latent HIV-1 provirus, autophagy can play a role in controlling latent HIV-1 infection by reducing the reservoir size through the susceptibility of latent HIV-1 infected cells to drug-induced autophagy-dependent cell death. As an example, the autophagyinducing peptide, Tat-beclin 1, composed of the amino acids 267-284 of BECN1 attached via a diglycine linker to the protein transduction domain of HIV-1 Tat, inhibits HIV-1 replication in primary human macrophages in an autophagy-dependent mechanism [199] . This peptide also restricted in vitro replication of Sindbis virus, chikungunya virus and West Nile Virus, and reduced the mortality of mice infected with West Nile Virus and chikungunya virus through autophagy [199] . Further studies demonstrated that when encapsulated within a lipid-coated hybrid poly(lactic-co-glycolic acid) (PLGA) nanoparticle, the Tat-beclin 1 peptide selectively kills latent HIV-1 infected CD4 + T cells through Na + /K + -ATPase-mediated autophagy-dependent autosis in the absence of increased viral replication [206] . Autosis is an autophagy-dependent, non-necrotic, non-apoptotic cell death characterised by unique biochemical and morphological features. In the first phase (1a), the endoplasmic reticulum becomes dilated and fragmented, and autophagosome, autolysosome, and empty vacuole numbers increase. In the second phase (1b), the perinuclear space (PNS) swells at discrete regions surrounding the inner nuclear membrane and contains cytoplasmic materials. In the last phase (2) , the morphology appears necrotic with ER, autophagosome, autolysosome numbers crashing while mitochondria and other cytoplasmic organelles swell. Also observed are a concavity of the nuclear surface and focal ballooning of the PNS, while the plasma membrane becomes porous [207] . Similar to Tat-beclin 1 nanoparticles, a lipid-coated hybrid PLGA nanoparticle encapsulated v-FLIP-α2 peptide (a ten amino acid α2-helix peptide derived from the death effector domain 1 of the K13 protein of human gammaherpesvirus 8 [208] ) also induces autosis of both HIV-1-infected resting memory CD4 + T cells and HIV-1-infected macrophages with no deleterious effects on uninfected bystander cells, and in the absence of increased viral replication [206, 209] . Nanoparticles are currently being evaluated to deliver small interfering RNAs (siRNAs) to silence gene expression in infected cells, as well as HIV-1 itself [210] , and to deliver cargo(s) that directly interfere with and inhibit viral entry [211, 212] , or to selectively kill HIV-1-infected cells [206] . Interestingly, a biomimetic nanoparticle wrapped in a CD4 + T cell membrane was shown to not only neutralise cell-free HIV-1, but also reduced cell-associated HIV-1 p24 through an autophagy-dependent mechanism [213, 214] . Importantly, under certain conditions, nanoparticles can be targeted to occult HIV-1 reservoir sites such as lymphatic tissue or the central nervous system (CNS) through the conjugation of cell-specific ligands to the nanoparticle surface, or with a biomimetic membrane [215, 216] . Although there is currently no delivery mechanism approved to deliver RNA or peptides to occult HIV-1 reservoirs in vivo, the regulatory approval of patisiran [217] , and the development and emergency use authorization of the COVID-19 mRNA vaccines BNT162b2 and mRNA-1273 [218, 219] paves the way for future lipid-based nanoparticle drug research to reach sanctuary sites, including the CNS. In other studies, autophagy inducing PI3K/AKT1 inhibitors, including the clinically available miltefosine, selectively kill HIV-1 infected macrophages [220, 221] . Therefore, the selective killing of HIV-1 infected cells, comprising those actively replicating virus and those within the latent reservoirs, has the potential to achieve the complete eradication of HIV-1 infection.

During infection, HIV-1 increases the expression of BIRC2/3/5, XIAP, as well as TREM1 and BCL2 family members, while decreasing the expression of pro-apoptotic proteins [137] [138] [139] [140] 147, [222] [223] [224] . In addition to inhibiting 5 LTR-dependent HIV-1 transcription [141, 142] , the overexpression of IAPs plays a further important role in the establishment and maintenance of HIV-1 latency by inhibiting HIV-1-mediated cytopathogenesis. They do this through direct antagonism, ubiquitination, and neddylation of apoptosis caspases [225, 226] , and ubiquitination of BECN1 (reducing autophagy) and RIPK1 [227] , suppressing its aberrant activation. RIPK1 is a death domain containing protein that controls differentiation and inflammation transcriptional responses [228] . The scaffolding function of RIPK1 is essential to promote pro-survival NF-κB signalling through the assembly of complex I, while activation of RIPK1 leads to either apoptosis or necroptosis [229] . RIPK1 also plays an important role in the cellular response to low energy levels and mediates AMPK-MTORC1 signalling [230] . Therefore, in addition to promoting the proteasomal degradation of BIRC2/3 and XIAP, the binding of DIABLO/SMAC mimetics to IAP also disinhibits apoptosis caspases and activates RIPK1 (Figure 3 ) [231] . In HIV-1-infected macrophages and latent HIV-1-infected resting memory CD4 + T cells, DIABLO/SMAC mimetics trigger the proteasomal degradation of IAPs that correlates with the induction of autophagy and cell death [140, 147, 232] . Importantly, although IAPs similarly induce the degradation of IAPs in uninfected cells, they do not undergo cell death [140, 147] . The DIABLO/SMAC mimetic-mediated degradation of IAPs leads to the deubiquitination and activation of RIPK1, which in HIV-1-infected cells leads to the formation of a deathinducing signalling complex (DISC) consisting of pro-apoptotic (FADD, RIPK1, RIPK3, CASP8) and autophagy (ATG5, ATG7, SQSTM1) proteins [140, 147] . Notably, inhibition of autophagy initiation, membrane nucleation, phagophore formation and expansion ablated DIABLO/SMAC mimetic-mediated apoptosis, while inhibition of autophagosome closure through membrane scission, autophago-lysosome fusion and degradation had no protective effect. Moreover, the DIABLO/SMAC mimetic-mediated DISC formation and localization to autophagosomes and resultant apoptosis required SQSTM1-mediated RIPK1 tethering to the phagophore membrane. Therefore, autophagosome membranes mediate DIABLO/SMAC mimetic-induced cell death by serving as a scaffold for efficient DISC formation rather than by autophagy degrading intracellular components. Importantly, although the DIABLO/SMAC mimetics AZD5582, xevinapant, and ciapavir are useful as LRA [142, 146, [148] [149] [150] [151] , treatment with birinapant, GDC-0152, and LCL-161 did not increase HIV-1 p24 antigen release indicating that the DIABLO/SMAC mimetics were killing HIV-1-infected cells in the absence of latency reactivation [140, 147, 232] . Notably, birinapant is also able to induce selective cell death in hepatitis B virus expressing hepatocytes [233] [234] [235] . Consequently, IAPs are excellent targets for therapeutic exploitation in an HIV-1 "kill, block and lock" cure strategy.

bly, inhibition of autophagy initiation, membrane nucleation, phagophore formation and expansion ablated DIABLO/SMAC mimetic-mediated apoptosis, while inhibition of autophagosome closure through membrane scission, autophago-lysosome fusion and degradation had no protective effect. Moreover, the DIABLO/SMAC mimetic-mediated DISC formation and localization to autophagosomes and resultant apoptosis required SQSTM1mediated RIPK1 tethering to the phagophore membrane. Therefore, autophagosome membranes mediate DIABLO/SMAC mimetic-induced cell death by serving as a scaffold for efficient DISC formation rather than by autophagy degrading intracellular components. Importantly, although the DIABLO/SMAC mimetics AZD5582, xevinapant, and ciapavir are useful as LRA [142, 146, [148] [149] [150] [151] , treatment with birinapant, GDC-0152, and LCL-161 did not increase HIV-1 p24 antigen release indicating that the DIABLO/SMAC mimetics were killing HIV-1-infected cells in the absence of latency reactivation [140, 147, 232] . Notably, birinapant is also able to induce selective cell death in hepatitis B virus expressing hepatocytes [233] [234] [235] . Consequently, IAPs are excellent targets for therapeutic exploitation in an HIV-1 "kill, block and lock" cure strategy. 

The combination of LPA with host-directed or direct-acting autophagy and autosis inducing drugs to eliminate selectively HIV-1 latently infected cells to reduce the viral reservoir can enhance the efficacy of the "block and lock" approach, and when combined with other strategies, could potentially achieve viral eradication. However, reaching isolated body compartments, including lymph nodes and the CNS remains a major challenge to achieving the full potential of these strategies. Currently, numerous drugs have shown considerable potential in vitro and in animal models that could contribute to an HIV-1 cure. Well-designed clinical trials will be required to assess the ability of any of these approaches to penetrate and act throughout the body. As these cure strategies are evaluated it is likely that the modulation of autophagy will be required to achieve an HIV-1 functional or complete virologic cure. 

The combination of LPA with host-directed or direct-acting autophagy and autosis inducing drugs to eliminate selectively HIV-1 latently infected cells to reduce the viral reservoir can enhance the efficacy of the "block and lock" approach, and when combined with other strategies, could potentially achieve viral eradication. However, reaching isolated body compartments, including lymph nodes and the CNS remains a major challenge to achieving the full potential of these strategies. Currently, numerous drugs have shown considerable potential in vitro and in animal models that could contribute to an HIV-1 cure. Well-designed clinical trials will be required to assess the ability of any of these approaches to penetrate and act throughout the body. As these cure strategies are evaluated, it is likely that the modulation of autophagy will be required to achieve an HIV-1 functional or complete virologic cure. 

Acute HIV-1 infection

HIV-1 reservoirs in urethral macrophages of patients under suppressive antiretroviral therapy

Microglial cells: The main HIV-1 reservoir in the brain

The interplay of HIV-1 and macrophages in viral persistence

Astrocytes are HIV reservoirs in the brain: A cell type with poor HIV infectivity and replication but efficient cell-to-cell viral transfer

Establishment of latent HIV-1 reservoirs: What do we really know?

Long-term follow-up studies confirm the stability of the latent reservoir for HIV-1 in resting CD4+ T cells

Precise quantitation of the latent HIV-1 reservoir: Implications for eradication strategies

The decay of the latent reservoir of replication-competent HIV-1 is inversely correlated with the extent of residual viral replication during prolonged anti-retroviral therapy

HIV-1 drug resistance profiles in children and adults with viral load of <50 copies/ml receiving combination therapy

Low-level viremia persists for at least 7 years in patients on suppressive antiretroviral therapy

HIV reservoir size and persistence are driven by T cell survival and homeostatic proliferation

Replication-competent noninduced proviruses in the latent reservoir increase barrier to HIV-1 cure

Specific HIV integration sites are linked to clonal expansion and persistence of infected cells

Multiple origins of virus persistence during natural control of HIV infection

Post-treatment HIV-1 controllers with a long-term virological remission after the interruption of early initiated antiretroviral therapy ANRS VISCONTI Study

HIV-1 virological remission lasting more than 12 years after interruption of early antiretroviral therapy in a perinatally infected teenager enrolled in the French ANRS EPF-CO10 paediatric cohort: A case report

Signaling hubs for metabolic sensing and longevity

Negative elongation factor is required for the maintenance of proviral latency but does not induce promoter-proximal pausing of RNA polymerase II on the HIV long terminal repeat

HIV-1 tat transcriptional activity is regulated by acetylation

HIV-1 Tat and host AFF4 recruit two transcription elongation factors into a bifunctional complex for coordinated activation of HIV-1 transcription

AFF4, a component of the ELL/P-TEFb elongation complex and a shared subunit of MLL chimeras, can link transcription elongation to leukemia

HIV-1 Tat assembles a multifunctional transcription elongation complex and stably associates with the 7SK snRNP

Key players in HIV-1 transcriptional regulation: Targets for a functional cure

Dynamics of human immunodeficiency virus transcription: P-TEFb phosphorylates RD and dissociates negative effectors from the transactivation response element

Spt5 cooperates with human immunodeficiency virus type 1 Tat by preventing premature RNA release at terminator sequences

Enhanced processivity of RNA polymerase II triggered by Tat-induced phosphorylation of its carboxy-terminal domain

The histone acetyltransferase, hGCN5, interacts with and acetylates the HIV transactivator

Requirement for SWI/SNF chromatinremodeling complex in Tat-mediated activation of the HIV-1 promoter

Tat inhibition by didehydro-Cortistatin A promotes heterochromatin formation at the HIV-1 long terminal repeat

Combinatorial patterns of histone acetylations and methylations in the human genome

a negative regulator of P-TEFb

HMGA1 recruits CTIP2-repressed P-TEFb to the HIV-1 and cellular target promoters

HIV-1 Vpr mediates the depletion of the cellular repressor CTIP2 to counteract viral gene silencing

Autophagy restricts HIV-1 infection by selectively degrading Tat in CD4+ T lymphocytes

SHMT2 and the BRCC36/BRISC deubiquitinase regulate HIV-1 Tat K63-ubiquitylation and destruction by autophagy

A non-proteolytic role for ubiquitin in Tat-mediated transactivation of the HIV-1 promoter

Making sense of multifunctional proteins: Human immunodeficiency virus type 1 accessory and regulatory proteins and connections to transcription

Modulation of the stability and activities of HIV-1 Tat by its ubiquitination and carboxyl-terminal region

Long noncoding RNA NRON contributes to HIV-1 latency by specifically inducing tat protein degradation

Epigenetic crosstalk in chronic infection with HIV-1

Modulation of BRD4 in HIV epigenetic regulation: Implications for finding an HIV cure

Counterregulation of chromatin deacetylation and histone deacetylase occupancy at the integrated promoter of human immunodeficiency virus type 1 (HIV-1) by the HIV-1 repressor YY1 and HIV-1 activator Tat

NF-kappaB p50 promotes HIV latency through HDAC recruitment and repression of transcriptional initiation

Recruitment of chromatinmodifying enzymes by CTIP2 promotes HIV-1 transcriptional silencing

Involvement of histone H3 lysine 9 (H3K9) methyltransferase G9a in the maintenance of HIV-1 latency and its reactivation by BIX01294

LSD1 cooperates with CTIP2 to promote HIV-1 transcriptional silencing

HIV latency in isolated patient CD + T cells may be due to blocks in HIV transcriptional elongation, completion, and splicing

Transcriptional profiles of latent human immunodeficiency virus in infected individuals: Effects of Tat on the host and reservoir

Gut and blood differ in constitutive blocks to HIV transcription, suggesting tissue-specific differences in the mechanisms that govern HIV latency

Posttranscriptional regulation of HIV-1 gene expression during replication and reactivation from latency by nuclear matrix protein MATR3

Cellular microRNAs contribute to HIV-1 latency in resting primary CD4+ T lymphocytes

Suppression of microRNA-silencing pathway by HIV-1 during virus replication

miR-198 inhibits HIV-1 gene expression and replication in monocytes and its mechanism of action appears to involve repression of cyclin T1

Suppression of HIV-1 replication by microRNA effectors

WIPI2 links LC3 conjugation with PI3P, autophagosome formation, and pathogen clearance by recruiting Atg12-5-16L1

Autophagosome closure requires membrane scission

Dikic, I. The LC3 interactome at a glance

Guidelines for the use and interpretation of assays for monitoring autophagy

Species-specific recognition of single-stranded RNA via toll-like receptor 7 and 8

MyD88-dependent immune activation mediated by human immunodeficiency virus type 1-encoded Toll-like receptor ligands

Endocytosis of HIV-1 activates plasmacytoid dendritic cells via Toll-like receptor-viral RNA interactions

Human immunodeficiency virus type 1 Nef inhibits autophagy through transcription factor EB sequestration

Human immunodeficiency virus-1 inhibition of immunoamphisomes in dendritic cells impairs early innate and adaptive immune responses

HIV-infected dendritic cells present endogenous MHC class II-restricted antigens to HIV-specific CD4+ T cells

Pathogen recognition and innate immunity

Toll-like receptor (TLR) 2-9 agonists-induced cytokines and chemokines: I. Comparison with T cell receptor-induced responses

The human-associated archaeon Methanosphaera stadtmanae is recognized through its RNA and induces TLR8-dependent NLRP3 inflammasome activation

SARS-CoV-2, SARS-CoV-1, and HIV-1 derived ssRNA sequences activate the NLRP3 inflammasome in human macrophages through a non-classical pathway

Autophagy-based unconventional secretory pathway for extracellular delivery of IL-1β

Production of interferon α by human immunodeficiency virus type 1 in human plasmacytoid dendritic cells is dependent on induction of autophagy

TLR7/8 triggering exerts opposing effects in acute versus latent HIV infection

Toll-like receptor 8 ligands activate a vitamin D mediated autophagic response that inhibits human immunodeficiency virus type 1

HIV induces both a down-regulation of IRAK-4 that impairs TLR signalling and an up-regulation of the antibiotic peptide dermcidin in monocytic cells

Subnormal serum concentration of 1,25-vitamin D in human immunodeficiency virus infection: Correlation with degree of immune deficiency and survival

Severe deficiency of 1,25-dihydroxyvitamin D3 in human immunodeficiency virus infection: Association with immunological hyperactivity and only minor changes in calcium homeostasis

Changes in calciotropic hormones and biochemical markers of bone metabolism in patients with human immunodeficiency virus infection

Osteopenia in HIV-infected women prior to highly active antiretroviral therapy

High prevalence of severe vitamin D deficiency in combined antiretroviral therapy-naive and successfully treated Swiss HIV patients

Vitamin D deficiency in HIV infection: An underestimated and undertreated epidemic

Vitamin D and clinical disease progression in HIV infection: Results from the EuroSIDA study

Vitamin D in HIV-infected patients

The potential protective role of vitamin D supplementation on HIV-1 infection

Vitamin D status modulates inflammatory response in HIV+ subjects: Evidence for involvement of autophagy and TG2 expression in PBMC

Hormonally active vitamin D3 (1α,25-dihydroxycholecalciferol) triggers autophagy in human macrophages that inhibits HIV-1 infection

The cytoplasmic body component TRIM5α restricts HIV-1 infection in Old World monkeys

Specific recognition and accelerated uncoating of retroviral capsids by the TRIM5α restriction factor

TRIM5α disrupts the structure of assembled HIV-1 capsid complexes in vitro

M. p62/sequestosome-1 associates with and sustains the expression of retroviral restriction factor TRIM5α

TRIM proteins regulate autophagy and can target autophagic substrates by direct recognition

Receptor usage dictates HIV-1 restriction by human TRIM5α in dendritic cell subsets

A helical LC3-interacting region mediates the interaction between the retroviral restriction factor Trim5α and mammalian autophagy-related ATG8 proteins

an innate immune sensor for the retrovirus capsid lattice

A non-canonical role for the autophagy machinery in anti-retroviral signaling mediated by TRIM5α

High levels of TRIM5α are associated with xenophagy in HIV-1-infected long-term nonprogressors

Dikic, I. A role for ubiquitin in selective autophagy

Dikic, I. Ubiquitination and selective autophagy

Versatile roles of K63-linked ubiquitin chains in trafficking

The HDAC6/APOBEC3G complex regulates HIV-1 infectiveness by inducing Vif autophagic degradation

autophagosome maturation essential for ubiquitin-selective quality-control autophagy

Clearance of misfolded and aggregated proteins by aggrephagy and implications for aggregation diseases

Autophagy pathway intersects with HIV-1 biosynthesis and regulates viral yields in macrophages

HIV-1 Nef counteracts autophagy restriction by enhancing the association between BECN1 and its inhibitor BCL2 in a PRKN-dependent manner

HIV "shock and kill" therapy: In need of revision

Histone deacetylase inhibitors impair the elimination of HIV-infected cells by cytotoxic T-lymphocytes

Histone deacetylase inhibitors enhance CD4 T cell susceptibility to NK cell killing but reduce NK cell function

The histone deacetylase inhibitor vorinostat (SAHA) increases the susceptibility of uninfected CD4+ T cells to HIV by increasing the kinetics and efficiency of post-entry viral events

Identifying the membrane proteome of HIV-1 latently infected cells

Apoptotic killing of HIV-1-infected macrophages is subverted by the viral envelope glycoprotein

Replication-independent expression of anti-apoptosis marker genes in human peripheral blood mononuclear cells infected with the wild-type HIV-1 and reverse transcriptase variants

SMAC mimetics induce autophagy-dependent apoptosis of HIV-1-infected resting memory CD4+ T cells

Noncanonical NF-kappaB activation requires coordinated assembly of a regulatory complex of the adaptors cIAP1, cIAP2, TRAF2 and TRAF3 and the kinase NIK

BIRC2/cIAP1 is a negative regulator of HIV-1 transcription and can be targeted by Smac mimetics to promote reversal of viral latency

Smac/DIABLO selectively reduces the levels of c-IAP1 and c-IAP2 but not that of XIAP and livin in HeLa cells

IAP antagonists induce autoubiquitination of c-IAPs, NF-κB activation, and TNFα-dependent apoptosis

A. cIAP1 and cIAP2 facilitate cancer cell survival by functioning as E3 ligases that promote RIP1 ubiquitination

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

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

SMAC mimetic plus triple-combination bispecific HIVxCD3 retargeting molecules in SHIV.C.CH505-infected, antiretroviral therapy-suppressed rhesus macaques

Pharmacological activation of non-canonical NF-κB signaling activates latent HIV-1 reservoirs in vivo

The intact non-inducible latent HIV-1 reservoir is established in an in vitro primary T CM cell model of latency

CD8 lymphocyte depletion enhances the latency reversal activity of the SMAC mimetic AZD5582 in ART-suppressed SIV-infected rhesus macaques

Targeting cellular and tissue HIV reservoirs with Toll-like receptor agonists

Toll-like receptor ligands modulate dendritic cells to augment cytomegalovirus-and HIV-1-specific T cell responses

The TLR and IL-1 signalling network at a glance

Toll-like receptors control autophagy

Evaluating a new class of AKT/mTOR activators for HIV latency reversing activity ex vivo and in vivo

Prevention of activation of HIV-1 by antiviral agents in OM-10.1 cells

Novel indolocarbazole protein kinase C inhibitors prevent reactivation of HIV-1 in latently infected cells

The control of HIV after antiretroviral medication pause (CHAMP) study: Posttreatment controllers identified from 14 clinical studies

A child with perinatal HIV infection and long-term sustained virological control following antiretroviral treatment cessation

HIV-1 Tat and viral latency: What we can learn from naturally occurring sequence variations

Discovery of a Tat HIV-1 inhibitor through computer-aided drug design

A possible improvement for structure-based drug design illustrated by the discovery of a Tat HIV-1 inhibitor

Inhibitors of HIV-1 Tat-mediated transactivation

Homonuclear 1H NMR and circular dichroism study of the HIV-1 Tat Eli variant

Tat-based therapies as an adjuvant for an HIV-1 functional cure

New horizons for a cure for HIV-1. Viruses

An analog of the natural steroidal alkaloid cortistatin A potently suppresses Tat-dependent HIV transcription

Didehydro-cortistatin A inhibits HIV-1 by specifically binding to the unstructured basic region of Tat

Stochastic gene expression in a lentiviral positive-feedback loop: HIV-1 Tat fluctuations drive phenotypic diversity

The Tat inhibitor didehydro-cortistatin A prevents HIV-1 reactivation from latency

Modeling the effect of tat inhibitors on HIV latency

Transcriptional circuit fragility influences HIV proviral fate

Specific inhibition of HIV infection by the action of spironolactone in T cells

HEXIM1-Tat chimera inhibits HIV-1 replication

Structure-guided drug design identifies a BRD4-selective small molecule that suppresses HIV

Epigenetic suppression of HIV in myeloid cells by the BRD4-selective small molecule modulator ZL0580

Potent inhibition of HIV-1 replication by a Tat mutant

Nullbasic, a potent anti-HIV tat mutant, induces CRM1-dependent disruption of HIV rev trafficking

A HIV-1 Tat mutant protein disrupts HIV-1 Rev function by targeting the DEAD-box RNA helicase DDX1

A mutant tat protein inhibits HIV-1 reverse transcription by targeting the reverse transcription complex

The size of the expressed HIV reservoir predicts timing of viral rebound after treatment interruption

Stimulating the RIG-I pathway to kill cells in the latent HIV reservoir following viral reactivation

Evaluation of the innate immune modulator acitretin as a strategy to clear the HIV reservoir

Inhibition of polo-like kinase 1 (PLK1) facilitates the elimination of HIV-1 viral reservoirs in CD4 + T cells ex vivo

The combination of venetoclax and ixazomib selectively and efficiently kills HIV-infected cell lines but has unacceptable toxicity in primary cell models

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

Targeting of mTOR catalytic site inhibits multiple steps of the HIV-1 lifecycle and suppresses HIV-1 viremia in humanized mice

The immunosuppressant rapamycin represses human immunodeficiency virus type 1 replication

Autophagy plays an important role in the containment of HIV-1 in nonprogressor-infected patients

Autophagy-enhancing drugs limit mucosal HIV-1 acquisition and suppress viral replication ex vivo

First report on a series of HIV patients undergoing rapamycin monotherapy after liver transplantation

Everolimus, an mTORC1/2 inhibitor, in ART-suppressed individuals who received solid organ transplantation: A prospective study

Inhibition of human immunodeficiency virus (HIV-1) infection in human peripheral blood leucocytes-SCID reconstituted mice by rapamycin

Rapamycin causes down-regulation of CCR5 and accumulation of anti-HIV β-chemokines: An approach to suppress R5 strains of HIV-1

Autophagy complexes cell death by necroptosis

Cells 2021

The good, the bad and the autophagosome: Exploring unanswered questions of autophagy-dependent cell death

Low-level ionizing radiation induces selective killing of HIV-1-infected cells with reversal of cytokine induction using mTOR inhibitors

Identification of a candidate therapeutic autophagy-inducing peptide

Autophagy induction by histone deacetylase inhibitors inhibits HIV type 1

Induction of autophagy by PI3K/MTOR and PI3K/MTOR/BRD4 inhibitors suppresses HIV-1 replication

Trehalose inhibits human immunodeficiency virus type 1 infection in primary human macrophages and CD4 + T lymphocytes through two distinct mechanisms

Trehalose limits opportunistic mycobacterial survival during HIV co-infection by reversing HIV-mediated autophagy block

Nelfinavir and bortezomib inhibit mTOR activity via ATF4-mediated sestrin-2 regulation

MicroRNA profiles in monocyte-derived macrophages generated by interleukin-27 and human serum: Identification of a novel HIV-inhibiting and autophagy-inducing microRNA

Selective cell death of latently HIV-infected CD4 + T cells mediated by autosis inducing nanopeptides

Autosis is a Na + ,K + -ATPase-regulated form of cell death triggered by autophagy-inducing peptides, starvation, and hypoxiaischemia

Induction of a Na + /K + -ATPase-dependent form of autophagy triggers preferential cell death of human immunodeficiency virus type-1-infected macrophages

Nanotechnology approaches for the delivery of exogenous siRNA for HIV therapy

Inhibition of HIV fusion with multivalent gold nanoparticles

Human immune cell targeting of protein nanoparticles-caveospheres

T-cell-mimicking nanoparticles can neutralize HIV infectivity

CD4 + T cell-mimicking nanoparticles broadly neutralize HIV-1 and suppress viral replication through autophagy

Nanoparticle-based manipulation of antigen-presenting cells for cancer immunotherapy

Nanomaterials for drug delivery to the central nervous system

The Onpattro story and the clinical translation of nanomedicines containing nucleic acid-based drugs

Safety and efficacy of the BNT162b2 mRNA COVID-19 vaccine

Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine

Targeting the PI3K/Akt cell survival pathway to induce cell death of HIV-1 infected macrophages with alkylphospholipid compounds

Novel PI3K/Akt inhibitors screened by the cytoprotective function of human immunodeficiency virus type 1 Tat

HIV-1 Nef associated PAK and PI3-kinases stimulate Akt-independent Bad-phosphorylation to induce anti-apoptotic signals

Human immunodeficiency virus 1 favors the persistence of infection by activating macrophages through TNF. Virology

TREM-1 protects HIV-1-infected macrophages from apoptosis through maintenance of mitochondrial function

IAP proteins as targets for drug development in oncology

X-linked inhibitor of apoptosis protein-A critical death resistance regulator and therapeutic target for personalized cancer therapy

Modulating TRADD to restore cellular homeostasis and inhibit apoptosis

IAP-mediated protein ubiquitination in regulating cell signaling

Receptor-interacting protein kinase 1 (RIPK1) as a therapeutic target

RIPK1 promotes energy sensing by the mTORC1 pathway

A dimeric Smac/diablo peptide directly relieves caspase-3 inhibition by XIAP. Dynamic and cooperative regulation of XIAP by Smac/Diablo

Combination of a latencyreversing agent with a Smac mimetic minimizes secondary HIV-1 infection in vitro

Cellular inhibitor of apoptosis proteins prevent clearance of hepatitis B virus

Eliminating hepatitis B by antagonizing cellular inhibitors of apoptosis

Combinatorial treatment of birinapant and zosuquidar enhances effective control of HBV replication in vivo

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.