Bryostatin activates HIV-1 latent expression in human astrocytes through a PKC and NF-ĸB-dependent mechanism

Bryostatin-1 enhances the proliferation and functionality of exhausted CD8+ T cells by upregulating MAP Kinase 11

Introduction

Bryostatin-1, a potent agonist of the protein kinase C, has been studied for HIV and cancer therapies. In HIV research, it has shown anti-HIV effects during acute infection and reactivation of latent HIV in chronic infection. As effective CD8+ T cell responses are essential for eliminating reactivated virus and achieving a cure, it is important to investigate how bryostatin-1 affects HIV-specific CD8+ T cells. HIV-specific CD8+ T cells often become exhausted, showing reduced proliferative potential and impaired cytokine production, a dysfunction also observed in cancer. Therefore, we further investigated how bryostatin-1 directly impacts exhausted CD8+ T cells.

Methods

PBMCs from people with HIV (PWH) were treated with bryostatin-1 and tracked with proliferation dye for cell expansion. One day 6, HIV-specific CD8+ T cells were detected by tetramers staining and examined by flow cytometry. By utilizing an established in vitro murine T cell exhaustion system, changes in inhibitory receptors, transcription factors, cytokine production and killing capacity of bryostatin-1 treated exhausted CD8+ T cells were determined by flow cytometry. RNA-seq analysis was performed to study transcriptional changes in these cells.

Results

We found that bryostatin-1 improved the expansion and decreased PD-1 expression of HIV-specific CD8+ T cells. Bryostatin-1 enhanced the functionality and proliferation while decreasing inhibitory receptor expression of in vitro generated exhausted CD8+ T cells. Bryostatin-1 upregulated TCF-1 and decreased TOX expression. These changes were confirmed through RNA-seq analysis. RNA-seq revealed that mitogen-activated protein kinases (MAPK) 11 was significantly downregulated in exhausted CD8+ T cells, however, it greatly upregulated after bryostatin-1 treatment. Inhibition of MAPK11 in bryostatin-1-treated cells blocked the increased proliferation and IFN-γ production induced by bryostatin-1, but did not affect other bryostatin-1 induced effects, such as the reduction of inhibitory receptors.

Discussion

Our data demonstrate that bryostatin-1 induces a MAPK 11-dependent improvement in the proliferative and functional capacity of exhausted T cells. This study provides a rationale for bryostatin-1's potential to help eradicate the HIV reservoir during treatment, and it may also contribute to cancer immunotherapy by functionally improving exhausted CD8+ T cells.

CBP/p300 lysine acetyltransferases inhibit HIV-1 expression in latently infected T cells

HIV-1 latency is regulated by chromatin modifying enzymes, and histone deacetylase inhibitors (HDACi) cause reactivation of provirus expression. Surprisingly, we observed that inhibitors of the CBP/p300 acetyltransferases also cause reversal of latency in T cells. CBP/p300 inhibitors synergize with various latency reversing agents to cause HIV-1 reactivation. In contrast, inhibition of CBP/p300 impaired reversal of latency by the HDACi SAHA, indicating that CBP/p300 must contribute to acetylation on the HIV-1 LTR associated with HDACi-mediated latency reversal. CBP/p300 inhibition caused loss of H3K27ac and H3K4me3 from the LTR, but did not affect association of the inhibitor protein BRD4. Furthermore, inhibition of the additional lysine acetyltransferases PCAF/GCN5 or KAT6A/KAT6B also caused reversal of latency, suggesting that protein acetylation has an inhibitory effect on HIV-1 expression. Collectively, these observations indicate that transcription from the HIV-1 LTR is controlled both positively and negatively by protein acetylation, likely including both histone and non-histone regulatory targets.

Potential implications of protein kinase Cα in pathophysiological conditions and therapeutic interventions

PKCα is a molecule with many functions that play an important role in cell survival and death to maintain cellular homeostasis. Alteration in the normal functioning of PKCα is responsible for the complicated etiology of many pathologies, including cancer, cardiovascular diseases, kidney complications, neurodegenerative diseases, diabetics, and many others. Several studies have been carried out over the years on this kinase's function, and regulation in normal physiology and pathological conditions. A lot of data with antithetical results have therefore accumulated over time to create a complex framework of physiological implications connected to the PKCα function that needs comprehensive elucidation. In light of this information, we critically analyze the multiple roles played by PKCα in basic cellular processes and their molecular mechanism during various pathological conditions. This review further discusses the current approaches to manipulating PKCα signaling amplitude in the patient's favour and proposed PKCα as a therapeutic target to reverse pathological states.

Targeting and eradicating latent CNS reservoirs of HIV-1: original strategies and new models

Nowadays, combination antiretroviral therapy (cART) is the standard treatment for all people with human immunodeficiency virus (HIV-1). Although cART is effective in treating productive infection, it does not eliminate latent reservoirs of the virus. This leads to lifelong treatment associated with the occurrence of side effects and the development of drug-resistant HIV-1. Suppression of viral latency is therefore the major hurdle to HIV-1 eradication. Multiple mechanisms exist to regulate viral gene expression and drive the transcriptional and post-transcriptional establishment of latency. Epigenetic processes are amongst the most studied mechanisms influencing both productive and latent infection states. The central nervous system (CNS) represents a key anatomical sanctuary for HIV and is the focal point of considerable research efforts. However, limited and difficult access to CNS compartments makes understanding the HIV-1 infection state in latent brain cells such as microglial cells, astrocytes, and perivascular macrophages challenging. This review examines the latest advances on epigenetic transformations involved in CNS viral latency and targeting of brain reservoirs. Evidence from clinical studies as well as in vivo and in vitro models of HIV-1 persistence in the CNS will be discussed, with a special focus on recent 3D in vitro models such as human brain organoids. Finally, the review will address therapeutic considerations for targeting latent CNS reservoirs.

Shock and kill within the CNS: A promising HIV eradication approach?

The most studied HIV eradication approach is the "shock and kill" strategy, which aims to reactivate the latent reservoir by latency reversing agents (LRAs) and allowing elimination of these cells by immune-mediated clearance or viral cytopathic effects. The CNS is an anatomic compartment in which (persistent) HIV plays an important role in HIV-associated neurocognitive disorder. Restriction of the CNS by the blood-brain barrier is important for maintenance of homeostasis of the CNS microenvironment, which includes CNS-specific cell types, expression of transcription factors, and altered immune surveillance. Within the CNS predominantly myeloid cells such as microglia and perivascular macrophages are thought to be a reservoir of persistent HIV infection. Nevertheless, infection of T cells and astrocytes might also impact HIV infection in the CNS. Genetic adaptation to this microenvironment results in genetically distinct, compartmentalized viral populations with differences in transcription profiles. Because of these differences in transcription profiles, LRAs might have different effects within the CNS as compared with the periphery. Moreover, reactivation of HIV in the brain and elimination of cells within the CNS might be complex and could have detrimental consequences. Finally, independent of activity on latent HIV, LRAs themselves can have adverse neurologic effects. We provide an extensive overview of the current knowledge on compartmentalized (persistent) HIV infection in the CNS and on the "shock and kill" strategy. Subsequently, we reflect on the impact and promise of the "shock and kill" strategy on the elimination of persistent HIV in the CNS.

Off-Target Effect of Activation of NF-κB by HIV Latency Reversal Agents on Transposable Elements Expression

Many drugs have been evaluated to reactivate HIV-1 from cellular reservoirs, but the off-target effects of these latency reversal agents (LRA) remain poorly defined. Transposable elements (TEs) are reactivated during HIV-1 infection, but studies of potential off-target drug effects on TE expression have been limited. We analyzed the differential expression of TEs induced by canonical and non-canonical NF-κB signaling. We evaluated the effect of PKC agonists (Bryostatin and Ingenol B) on the expression of TEs in memory CD4+ T cells. Ingenol B induced 38 differentially expressed TEs (17 HERV (45%) and 21 L1 (55%)). Interestingly, TE expression in effector memory CD4+ T cells was more affected by Bryostatin compared to other memory T-cell subsets, with 121 (107 upregulated and 14 downregulated) differentially expressed (DE) TEs. Of these, 31% (n = 37) were HERVs, and 69% (n = 84) were LINE-1 (L1). AZD5582 induced 753 DE TEs (406 HERV (54%) and 347 L1 (46%)). Together, our findings show that canonical and non-canonical NF-κB signaling activation leads to retroelement expressions as an off-target effect. Furthermore, our data highlights the importance of exploring the interaction between LRAs and the expression of retroelements in the context of HIV-1 eradication strategies.

Possible mechanisms of HIV neuro-infection in alcohol use: Interplay of oxidative stress, inflammation, and energy interruption

Alcohol use and HIV-1 infection have a pervasive impact on brain function, which extends to the requirement, distribution, and utilization of energy within the central nervous system. This effect on neuroenergetics may explain, in part, the exacerbation of HIV-1 disease under the influence of alcohol, particularly the persistence of HIV-associated neurological complications. The objective of this review article is to highlight the possible mechanisms of HIV/AIDS progression in alcohol users from the perspective of oxidative stress, neuroinflammation, and interruption of energy metabolism. These include the hallmark of sustained immune cell activation and high metabolic energy demand by HIV-1-infected cells in the central nervous system, with at-risk alcohol use. Here, we discussed the point that the increase in energy supply requirement by HIV-1-infected neuroimmune cells as well as the deterrence of nutrient uptake across the blood-brain barrier significantly depletes the energy source and neuro-environment homeostasis in the CNS. We also described the mechanistic idea that comorbidity of HIV-1 infection and alcohol use can cause a metabolic shift and redistribution of energy usage toward HIV-1-infected neuroimmune cells, as shown in neuropathological evidence. Under such an imbalanced neuro-environment, meaningless energy waste is expected in infected cells, along with unnecessary malnutrition in non-infected neuronal cells, which is likely to accelerate HIV neuro-infection progression in alcohol use. Thus, it will be important to consider the factor of nutrients/energy imbalance in formulating treatment strategies to help impede the progression of HIV-1 disease and associated neurological disorders in alcohol use.

Putative role of natural products as Protein Kinase C modulator in different disease conditions

INTRODUCTION

Protein kinase C (PKC) is a promising drug target for various therapeutic areas. Natural products derived from plants, animals, microorganisms, and marine organisms have been used by humans as medicine from prehistoric times. Recently, several compounds derived from plants have been found to modulate PKC activities through competitive binding with ATP binding site, and other allosteric regions of PKC. As a result fresh race has been started in academia and pharmaceutical companies to develop an effective naturally derived small-molecule inhibitor to target PKC activities. Herein, in this review, we have discussed several natural products and their derivatives, which are reported to have an impact on PKC signaling cascade.

METHODS

All information presented in this review article regarding the regulation of PKC by natural products has been acquired by a systematic search of various electronic databases, including ScienceDirect, Scopus, Google Scholar, Web of science, ResearchGate, and PubMed. The keywords PKC, natural products, curcumin, rottlerin, quercetin, ellagic acid, epigallocatechin-3 gallate, ingenol 3 angelate, resveratrol, protocatechuic acid, tannic acid, PKC modulators from marine organism, bryostatin, staurosporine, midostaurin, sangivamycin, and other relevant key words were explored.

RESULTS

The natural products and their derivatives including curcumin, rottlerin, quercetin, ellagic acid, epigallocatechin-3 gallate, ingenol 3 angelate, resveratrol, bryostatin, staurosporine, and midostaurin play a major role in the management of PKC activity during various disease progression.

CONCLUSION

Based on the comprehensive literature survey, it could be concluded that various natural products can regulate PKC activity during disease progression. However, extensive research is needed to circumvent the challenge of isoform specific regulation of PKC by natural products.

Brain HIV-1 latently-infected reservoirs targeted by the suicide gene strategy

Reducing the pool of HIV-1 reservoirs in patients is a must to achieve functional cure. The most prominent HIV-1 cell reservoirs are resting CD4 + T cells and brain derived microglial cells. Infected microglial cells are believed to be the source of peripheral tissues reseedings and the emergence of drug resistance. Clearing infected cells from the brain is therefore crucial. However, many characteristics of microglial cells and the central nervous system make extremely difficult their eradication from brain reservoirs. Current methods, such as the "shock and kill", the "block and lock" and gene editing strategies cannot override these difficulties. Therefore, new strategies have to be designed when considering the elimination of brain reservoirs. We set up an original gene suicide strategy using latently infected microglial cells as model cells. In this paper we provide proof of concept of this strategy.

Macrolides: From Toxins to Therapeutics

Macrolides are a diverse class of hydrophobic compounds characterized by a macrocyclic lactone ring and distinguished by variable side chains/groups. Some of the most well characterized macrolides are toxins produced by marine bacteria, sea sponges, and other species. Many marine macrolide toxins act as biomimetic molecules to natural actin-binding proteins, affecting actin polymerization, while other toxins act on different cytoskeletal components. The disruption of natural cytoskeletal processes affects cell motility and cytokinesis, and can result in cellular death. While many macrolides are toxic in nature, others have been shown to display therapeutic properties. Indeed, some of the most well known antibiotic compounds, including erythromycin, are macrolides. In addition to antibiotic properties, macrolides have been shown to display antiviral, antiparasitic, antifungal, and immunosuppressive actions. Here, we review each functional class of macrolides for their common structures, mechanisms of action, pharmacology, and human cellular targets.

Harmine enhances the activity of the HIV-1 latency-reversing agents ingenol A and SAHA

Infection with human immunodeficiency virus 1 (HIV-1) remains incurable because long-lived, latently-infected cells persist during prolonged antiretroviral therapy. Attempts to pharmacologically reactivate and purge the latent reservoir with latency reactivating agents (LRAs) such as protein kinase C (PKC) agonists (e.g. ingenol A) or histone deacetylase (HDAC) inhibitors (e.g. SAHA) have shown promising but incomplete efficacy. Using the J-Lat T cell model of HIV latency, we found that the plant-derived compound harmine enhanced the efficacy of existing PKC agonist LRAs in reactivating latently-infected cells. Treatment with harmine increased not only the number of reactivated cells but also increased HIV transcription and protein expression on a per-cell basis. Importantly, we observed a synergistic effect when harmine was used in combination with ingenol A and the HDAC inhibitor SAHA. An investigation into the mechanism revealed that harmine, when used with LRAs, increased the activity of NFκB, MAPK p38, and ERK1/2. Harmine treatment also resulted in reduced expression of HEXIM1, a negative regulator of transcriptional elongation. Thus, harmine enhanced the effects of LRAs by increasing the availability of transcription factors needed for HIV reactivation and promoting transcriptional elongation. Combination therapies with harmine and LRAs could benefit patients by achieving deeper reactivation of the latent pool of HIV provirus.

The long noncoding RNA LINC01140/miR-140-5p/FGF9 axis modulates bladder cancer cell aggressiveness and macrophage M2 polarization

MIBC (muscle invasive bladder cancer) only accounts for only a minority of bladder cancers, however, the disease-specific and overall survival rates of patients with MIBC are low. Macrophage M2 polarization has been reported to be associated with poorer prognosis in bladder cancer. Through cancer bioinformatics and experimental analyses, FGF9 was found to be upregulated in MIBC tissues. FGF9 knockdown in T24 cells strongly suppressed the viability, migratory capacity, and invasive capacity of cells; culture with medium from FGF9 knockdown T24 cells (si-FGF9-CM) significantly inhibited macrophage M2 polarization, while promoting M1 polarization. The long noncoding RNA (lncRNA) LINC01140 was positively correlated with FGF9 and was significantly upregulated in MIBC tissues. LINC01140 knockdown inhibited the viability, migratory capacity and invasive capacity of T24 cells; culture in si-LINC01140-CM also inhibited macrophage M2 polarization, while promoting M1 polarization. LINC01140 targeted miR-140-5p, while miR-140-5p targeted FGF9 to form a lncRNA-miRNA-mRNA axis. The effects of miR-140-5p inhibition on bladder cancer aggressiveness and macrophage M2 polarization were opposite to those of LINC01140 or FGF9 knockdown; additionally, miR-140-5p inhibition partially reversed the effects of LINC01140 knockdown on FGF9 protein levels, bladder cancer phenotype, and macrophage M2 polarization. In conclusion, LINC01140, miR-140-5p, and FGF9 form a lncRNA-miRNA-mRNA axis that modulates the bladder cancer phenotype, affects macrophage M2 polarization through the tumor microenvironment, and in turn affects bladder cancer cell aggressiveness.

A novel selective histone deacetylase I inhibitor CC-4a activates latent HIV-1 through NF-κB pathway

AIMS

The fact that HIV-1 inside human bodies can perform reverse transcription and integrate resultant DNA into host chromosome remains a challenge in AIDS treatment. "Shock and kill" strategy was proposed to achieve the functional cure, which requested latency reactivating agents (LRAs) to reactivate latent HIV-1 and then extirpate viruses and infected cells with antiviral agents and the immune system. However, there are no feasible LRAs clinically applied. Herein, we examined a synthesized HDAC I inhibitor, CC-4a, in reactivating latent HIV-1 and investigated its mechanisms.

MATERIALS AND METHODS

Two HIV-1 infected cell models and human PBMCs were used in this study. Flow cytometry, ELISA, luciferase, and RT-PCR assay were used to analyze the expression of viral protein and mRNA. The mechanisms were explored by using cytoplasmic nuclear protein isolation and western blotting assays.

KEY FINDINGS

CC-4a could successfully reactivate latent HIV-1 at the protein and gene levels with low cytotoxicity. Intriguingly, CC-4a showed the ability to induce apoptosis in HIV-1 infected cell models. CC-4a exerted a synergistic activation effect with prostratin without triggering global T cell activation and inflammatory factor storm. It was further found that CC-4a down-regulated the expressions of CCR5 and CD4. Moreover, CC-4a together with antiviral drugs was proved to antagonize HIV-1 without mutual interference. Finally, the enhanced histone acetylation and activated NF-κB pathway were detected in CC-4a mechanisms.

SIGNIFICANCE

The results suggested that CC-4a activated latent HIV-1 and showed promising clinical applications, demonstrating that CC-4a played a role in HIV-1 eradication in "shock and kill" strategy.

Engineering CAR T Cells to Target the HIV Reservoir

The HIV reservoir remains to be a difficult barrier to overcome in order to achieve a therapeutic cure for HIV. Several strategies have been developed to purge the reservoir, including the “kick and kill” approach, which is based on the notion that reactivating the latent reservoir will allow subsequent elimination by the host anti-HIV immune cells. However, clinical trials testing certain classes of latency reactivating agents (LRAs) have so far revealed the minimal impact on reducing the viral reservoir. A robust immune response to reactivated HIV expressing cells is critical for this strategy to work. A current focus to enhance anti-HIV immunity is through the use of chimeric antigen receptors (CARs). Currently, HIV-specific CARs are being applied to peripheral T cells, NK cells, and stem cells to boost recognition and killing of HIV infected cells. In this review, we summarize current developments in engineering HIV directed CAR-expressing cells to facilitate HIV elimination. We also summarize current LRAs that enhance the “kick” strategy and how new generation and combinations of LRAs with HIV specific CAR T cell therapies could provide an optimal strategy to target the viral reservoir and achieve HIV clearance from the body.

The Phylum Bryozoa: From Biology to Biomedical Potential

Less than one percent of marine natural products characterized since 1963 have been obtained from the phylum Bryozoa which, therefore, still represents a huge reservoir for the discovery of bioactive metabolites with its ~6000 described species. The current review is designed to highlight how bryozoans use sophisticated chemical defenses against their numerous predators and competitors, and which can be harbored for medicinal uses. This review collates all currently available chemoecological data about bryozoans and lists potential applications/benefits for human health. The core of the current review relates to the potential of bryozoan metabolites in human diseases with particular attention to viral, brain, and parasitic diseases. It additionally weighs the pros and cons of total syntheses of some bryozoan metabolites versus the synthesis of non-natural analogues, and explores the hopes put into the development of biotechnological approaches to provide sustainable amounts of bryozoan metabolites without harming the natural environment.

Insights into the Gene Expression Profiles of Active and Restricted Red/Green-HIV+ Human Astrocytes: Implications for Shock or Lock Therapies in the Brain

A significant number of people living with human immunodeficiency virus type 1 (HIV-1) suffer from HIV-associated neurocognitive disorders (HAND). Many previous studies investigating HIV in astrocytes as a heterogenous population have established the relevance of astrocytes to HIV-associated neuropathogenesis. However, these studies were unable to differentiate the state of infection, i.e., active or latent, or to evaluate how this affects astrocyte biology. In this study, the pseudotyped doubly labeled fluorescent reporter red/green (R/G)-HIV-1 was used to identify and enrich restricted and active populations of HIV⁺ astrocytes based on the viral promoter activity. Here, we report that the majority of human astrocytes restricted R/G-HIV-1 gene expression early during infection and were resistant to reactivation by vorinostat and interleukin 1β. However, actively infected astrocytes were inducible, leading to increased expression of viral proteins upon reactivation. R/G-HIV-1 infection also significantly decreased the cell proliferation and glutamate clearance ability of astrocytes, which may contribute to excitotoxicity. Moreover, transcriptome analyses to compare gene expression patterns of astrocyte harboring active versus restricted long terminal repeats (LTRs) revealed that the gene expression patterns were similar and that the active population demonstrated more widespread and robust changes. Our data suggest that harboring the HIV genome profoundly alters astrocyte biology and that strategies that keep the virus latent (e.g., block and lock) or those that reactivate the latent virus (e.g., shock and kill) would be detrimental to astrocyte function and possibly augment their contributions to HAND.IMPORTANCE More than 36 million people are living with HIV-1 worldwide, and despite antiretroviral therapy, 30 to 50% of the people living with HIV-1 suffer from mild to moderate neurocognitive disorders. HIV-1 reservoirs in the central nervous system (CNS) are challenging to address due to low penetration of antiretroviral drugs, lack of resident T cells, and permanent integration of provirus into neural cells such as microglia and astrocytes. Several studies have shown astrocyte dysfunction during HIV-1 infection. However, little is known about how HIV-1 latency affects their function. The significance of our research is in identifying that the majority of HIV⁺ astrocytes restrict HIV expression and were resistant to reactivation. Further, simply harboring the HIV genome profoundly altered astrocyte biology, resulting in a proinflammatory phenotype and functional changes. In this context, therapeutic strategies to reactivate or silence astrocyte HIV reservoirs, without excising proviral DNA, will likely lead to detrimental neuropathological outcomes during HIV CNS infection.

Impact of Myeloid Reservoirs in HIV Cure Trials

PURPOSE OF REVIEW

Gallant efforts are ongoing to achieve sustained antiretroviral therapy (ART)-free HIV remission in the HIV-infected person; however, most, if not all, current human clinical studies have primarily focused these efforts on targeting viral persistence in CD4 T cells in blood and tissue sanctuaries. The lack of myeloid centered HIV clinical trials, either as primary or secondary end points, has hindered our understanding of the contribution of myeloid cells in unsuccessful trials but may also guide successes in future HIV eradication clinical strategies.

RECENT FINDINGS

Recent advances have highlighted the importance of myeloid reservoirs as sanctuaries of HIV persistence and therefore may partially be responsible for viral recrudescence following ART treatment interruption in several clinical trials where HIV was not detectable or recovered from CD4 T cells. Given these findings, novel innovative therapeutic approaches specifically focused on HIV clearance in myeloid cell populations need to be vigorously pursued if we are to achieve additional cases of sustained ART-free remission. This review will highlight new research efforts defining myeloid persistence and recent advances in HIV remission and cure trials that would be relevant in targeting this compartment and make an argument as to their clinical relevancy as we progress towards sustained ART-free HIV remission in all HIV-infected persons.

The impact of HIV central nervous system persistence on pathogenesis

: The persistence of HIV in the central nervous system is somewhat controversial particularly in the context of HIV viral suppression from combined antiretroviral therapy. Further, its significance in relation to HIV pathogenesis in the context of HIV-associated neurocognitive disorders, systemic HIV pathogenesis, and eradication in general, but especially from the brain, are even more contentious. This review will discuss each of these aspects in detail, highlighting new data, particularly from recent conference presentations.

Perspective on potential impact of HIV central nervous system latency on eradication

: Given the challenges of life-long adherence to suppressive HIV antiretroviral therapy (ART) and possibilities of comorbidities, such as HIV association neurocognitive disorder, HIV remission and eradication are desirable goals for people living with HIV. In some individuals, there is evidence that HIV persists and replicates in the CNS, impacting the success of HIV remission interventions. This article addresses the role of HIV CNS latency on HIV eradication, examines the effects of early ART, latency-modifying agents, antibody-based and T-cell enhancing therapies on the CNS as well as ART interruption in remission studies. We propose the integration of CNS monitoring into such studies in order to clarify the short-term and long-term neurological safety of experimental agents and treatment interruption, and to better characterize their effects on HIV CNS persistence.

Unlocking the Drug Potential of the Bryostatin Family: Recent Advances in Product Synthesis and Biomedical Applications

Bryostatins are a class of naturally occurring macrocyclic lactones with a unique fast developing portfolio of clinical applications, including treatment of AIDS, Alzheimer's disease, and cancer. This comprehensive account summarizes the recent progress (2014-present) in the development of bryostatins, including their total synthesis and biomedical applications. An emphasis is placed on the discussion of bryostatin 1, the most-studied analogue to date. This review highlights the synthetic and biological challenges of bryostatins and provides an outlook on their future development.

Tat expression led to increased histone 3 tri-methylation at lysine 27 and contributed to HIV latency in astrocytes through regulation of MeCP2 and Ezh2 expression

Astrocytes are susceptible to HIV infection and potential latent HIV reservoirs. Tat is one of three abundantly expressed HIV early genes in HIV-infected astrocytes and has been shown to be a major pathogenic factor for HIV/neuroAIDS. In this study, we sought to determine if and how Tat expression would affect HIV infection and latency in astrocytes. Using the glycoprotein from vesicular stomatitis virus-pseudotyped red-green HIV (RGH) reporter viruses, we showed that HIV infection was capable of establishing HIV latency in astrocytes. We also found that Tat expression decreased the generation of latent HIV-infected cells. Activation of latent HIV-infected astrocytes showed that treatment of GSK126, a selective inhibitor of methyltransferase enhancer of zeste homolog 2 (Ezh2) that is specifically responsible for tri-methylation of histone 3 lysine 27 (H3K27me3), led to activation of significantly more latent HIV-infected Tat-expressing astrocytes. Molecular analysis showed that H3K27me3, Ezh2, MeCP2, and Tat all exhibited a similar bimodal expression kinetics in the course of HIV infection and latency in astrocytes, although H3K27me3, Ezh2, and MeCP2 were expressed higher in Tat-expressing astrocytes and their expression were peaked immediately preceding Tat expression. Subsequent studies showed that Tat expression alone was sufficient to induce H3K27me3 expression, likely through its regulation of Ezh2 and MeCP2 expression. Taken together, these results showed for the first time that Tat expression induced H3K27me3 expression and contributed to HIV latency in astrocytes and suggest a new role and novel mechanism for Tat in HIV latency.

Dual effects of the novel ingenol derivatives on the acute and latent HIV-1 infections

The latent reservoir of HIV-1 in resting memory CD4⁺ T cells serves as a major barrier to curing HIV-1 infection. Reactivation of latent HIV-1 is proposed as a promising strategy for the clearance of the viral reservoirs. Because of the limitations of current latency reversal agents (LRAs), identification of new LRAs is urgently required. Here, we analyzed Euphorbia kansui extracts and obtained three ingenol derivative compounds named EK-1A, EK-5A and EK-15A. We found that ingenol derivatives can effectively reactivate latent HIV-1 at very low (nanomolar) concentrations in HIV latency model in vitro. Furthermore, ingenol derivatives exhibited synergy with other LRAs in reactivating latent HIV-1. We verified that EK-15A can promote latent HIV-1 reactivation in the ex vivo resting CD4⁺ T cells isolated from the peripheral blood of HIV-infected individuals on suppressive antiretroviral therapy. In addition, ingenol derivatives down-regulated the expression of cell surface HIV co-receptors CCR5 and CXCR4, therefore potentially preventing new infection of HIV-1. Our results indicated that the ingenol derivatives extracted from Euphorbia kansui have dual functions: reactivation of latent HIV-1 and inhibition of HIV-1 infection.

Arsenic Trioxide Impacts Viral Latency and Delays Viral Rebound after Termination of ART in Chronically SIV-Infected Macaques

The latent viral reservoir is the source of viral rebound after interruption of antiretroviral therapy (ART) and is the major obstacle in eradicating the latent human immunodeficiency virus-1 (HIV-1). In this study, arsenic class of mineral, arsenic trioxide, clinically approved for treating acute promyelocytic leukemia, is demonstrated to reactivate latent provirus in CD4+ T cells from HIV-1 patients and Simian immunodeficiency virus (SIV)-infected macaques, without significant systemic T cell activation and inflammatory responses. In a proof-of-concept study using chronically SIVmac239-infected macaques, arsenic trioxide combined with ART delays viral rebound after ART termination, reduces the integrated SIV DNA copies in CD4+ T cells, and restores CD4+ T cells counts in vivo. Most importantly, half of arsenic trioxide-treated macaques show no detectable viral rebound in the plasma for at least 80 days after ART discontinuation. Mechanistically, the study reveals that CD4 receptors and CCR5 co-receptors of CD4+ T cells are significantly downregulated by arsenic trioxide treatment, which reduces susceptibility to infection after provirus reactivation. Furthermore, an increase in SIV-specific immune responses after arsenic trioxide treatment may contribute to suppression of viral rebound. This work suggests that arsenic trioxide in combination with ART is a novel regimen in down-sizing or even eradicating latent HIV-1 reservoir.

RNA-induced epigenetic silencing inhibits HIV-1 reactivation from latency

BACKGROUND

Current antiretroviral therapy is effective in controlling HIV-1 infection. However, cessation of therapy is associated with rapid return of viremia from the viral reservoir. Eradicating the HIV-1 reservoir has proven difficult with the limited success of latency reactivation strategies and reflects the complexity of HIV-1 latency. Consequently, there is a growing need for alternate strategies. Here we explore a "block and lock" approach for enforcing latency to render the provirus unable to restart transcription despite exposure to reactivation stimuli. Reactivation of transcription from latent HIV-1 proviruses can be epigenetically blocked using promoter-targeted shRNAs to prevent productive infection. We aimed to determine if independent and combined expression of shRNAs, PromA and 143, induce a repressive epigenetic profile that is sufficiently stable to protect latently infected cells from HIV-1 reactivation when treated with a range of latency reversing agents (LRAs).

RESULTS

J-Lat 9.2 cells, a model of HIV-1 latency, expressing shRNAs PromA, 143, PromA/143 or controls were treated with LRAs to evaluate protection from HIV-1 reactivation as determined by levels of GFP expression. Cells expressing shRNA PromA, 143, or both, showed robust resistance to viral reactivation by: TNF, SAHA, SAHA/TNF, Bryostatin/TNF, DZNep, and Chaetocin. Given the physiological importance of TNF, HIV-1 reactivation was induced by TNF (5 ng/mL) and ChIP assays were performed to detect changes in expression of epigenetic markers within chromatin in both sorted GFP^- and GFP⁺ cell populations, harboring latent or reactivated proviruses, respectively. Ordinary two-way ANOVA analysis used to identify interactions between shRNAs and chromatin marks associated with repressive or active chromatin in the integrated provirus revealed significant changes in the levels of H3K27me3, AGO1 and HDAC1 in the LTR, which correlated with the extent of reduced proviral reactivation. The cell line co-expressing shPromA and sh143 consistently showed the least reactivation and greatest enrichment of chromatin compaction indicators.

CONCLUSION

The active maintenance of epigenetic silencing by shRNAs acting on the HIV-1 LTR impedes HIV-1 reactivation from latency. Our "block and lock" approach constitutes a novel way of enforcing HIV-1 "super latency" through a closed chromatin architecture that renders the virus resistant to a range of latency reversing agents.

Review of bioactive secondary metabolites from marine bryozoans in the progress of new drugs discovery

Marine bryozoans play an important role for the discovery of novel bioactive compounds among marine organisms. In this review, we summarize 164 new secondary metabolites including macrocyclic lactones, sterols, alkaloids, sphingolipids and so forth from 24 marine bryozoans in the last two decades. The structural features, bioactivity, structure-activity relationship, mechanism and strategies to address the resupply of these scarce secondary metabolites are discussed. The structural and bioactive diversity of the secondary metabolites from marine bryozoans indicated the possibility of using these compounds, especially bryostatin 1 (1), bryostatin analog (BA1), alkaloids (50, 53, 127-128 and 134-139), sphingolipids sulfates (148 and 149) and sulfur-containing aromatic compound (160), as the starting points for new drug discovery.

Different molecular mechanisms of HTLV-1 and HIV LTR activation by TPA

HTLV-1 and HIV-1 are retroviruses involved in different human diseases. However, following infection, these viruses inter into a latent state. Tax and Tat are regarded as trans-activators of HTLV-1 and HIV-1 respectively. As it known, during the latent state the infected cells contain low Tax and Tat protein levels, so the activation of these viruses must be independent of these proteins. Here we focus on exploring the mechanism of activation of these viruses by 12-O-tetradecanoylphorbol-13-acetate (TPA), which is a potent activator of protein kinase C (PKC) and considered as a stress-inducing agent. Our results showed that short exposure to TPA considerably stimulated only the HIV-1 LTR expression, while long exposure stimulated only the HTLV-1 LTR and that their activation is agonized or antagonized by PKC respectively. It was found that TPA induced interaction between the transcriptional factors Sp1 and P53 producing Sp1-p53 complex which strongly interacted with c-Jun only after short exposure to TPA. In addition, TPA treatment highly induced the expression of CREB which attached to the Sp1-p53 complex mainly after a long exposure to TPA. A strong binding of sp1, p53 and CREB proteins with HTLV-1 LTR and strong binding of NF-κB with HIV-1 LTR were observed after long (24 h) and short (6 h) exposures to TPA respectively by Chip assay. These results support the possibility that sp1, p53 and CREB are involved in the TPA induced HTLV-1 LTR expression while TPA activation of HIV-1 LTR seems to be dependent on PKC activity through the NF-κB pathway.

The latest evidence for possible HIV-1 curative strategies

Human immunodeficiency virus type 1 (HIV-1) infection remains a major health issue worldwide. In developed countries, antiretroviral therapy has extended its reach from treatment of people living with HIV-1 to post-exposure prophylaxis, treatment as prevention, and, more recently, pre-exposure prophylaxis. These healthcare strategies offer the epidemiological tools to curve the epidemic in rich settings and will be concomitantly implemented in developing countries. One of the remaining challenges is to identify an efficacious curative strategy. This review manuscript will focus on some of the current curative strategies aiming at providing a sterilizing or functional cure to HIV-1-positive individuals. These include the following: early treatment initiation in post-treatment controllers as a long-term HIV-1 remission strategy, latency reversal, gene editing with or without stem cell transplantation, and antibodies against either the viral envelope protein or the host integrin α4β7.

Astrocytes sustain long-term productive HIV-1 infection without establishment of reactivable viral latency

The "shock and kill" HIV-1 cure strategy proposes eradication of stable cellular reservoirs by clinical treatment with latency-reversing agents (LRAs). Although resting CD4⁺ T cells latently infected with HIV-1 constitute the main reservoir that is targeted by these approaches, their consequences on other reservoirs such as the central nervous system are still unknown and should be taken into consideration. We performed experiments aimed at defining the possible role of astrocytes in HIV-1 persistence in the brain and the effect of LRA treatments on this viral sanctuary. We first demonstrate that the diminished HIV-1 production in a proliferating astrocyte culture is due to a reduced proliferative capacity of virus-infected cells compared with uninfected astrocytes. In contrast, infection of non-proliferating astrocytes led to a robust HIV-1 infection that was sustained for over 60 days. To identify astrocytes latently infected with HIV-1, we designed a new dual-color reporter virus called NL4.3 eGFP-IRES-Crimson that is fully infectious and encodes for all viral proteins. Although we detected a small fraction of astrocytes carrying silent HIV-1 proviruses, we did not observe any reactivation using various LRAs and even strong inducers such as tumor necrosis factor, thus suggesting that these proviruses were either not transcriptionally competent or in a state of deep latency. Our findings imply that astrocytes might not constitute a latent reservoir per se but that relentless virus production by this brain cell population could contribute to the neurological disorders seen in HIV-1-infected persons subjected to combination antiretroviral therapy.

HIV latency is reversed by ACSS2-driven histone crotonylation

Eradication of HIV-1 (HIV) is hindered by stable viral reservoirs. Viral latency is epigenetically regulated. While the effects of histone acetylation and methylation at the HIV long-terminal repeat (LTR) have been described, our knowledge of the proviral epigenetic landscape is incomplete. We report that a previously unrecognized epigenetic modification of the HIV LTR, histone crotonylation, is a regulator of HIV latency. Reactivation of latent HIV was achieved following the induction of histone crotonylation through increased expression of the crotonyl-CoA-producing enzyme acyl-CoA synthetase short-chain family member 2 (ACSS2). This reprogrammed the local chromatin at the HIV LTR through increased histone acetylation and reduced histone methylation. Pharmacologic inhibition or siRNA knockdown of ACSS2 diminished histone crotonylation-induced HIV replication and reactivation. ACSS2 induction was highly synergistic in combination with either a protein kinase C agonist (PEP005) or a histone deacetylase inhibitor (vorinostat) in reactivating latent HIV. In the SIV-infected nonhuman primate model of AIDS, the expression of ACSS2 was significantly induced in intestinal mucosa in vivo, which correlated with altered fatty acid metabolism. Our study links the HIV/SIV infection-induced fatty acid enzyme ACSS2 to HIV latency and identifies histone lysine crotonylation as a novel epigenetic regulator for HIV transcription that can be targeted for HIV eradication.

Contrasting effect of the latency-reversing agents bryostatin-1 and JQ1 on astrocyte-mediated neuroinflammation and brain neutrophil invasion

Background

Despite effectiveness of the combined antiretroviral therapy, HIV-1 persists in long-lived latently infected cells. Consequently, new therapeutic approaches aimed at eliminating this latent reservoir are currently being developed. A “shock and kill” strategy using latency-reversing agents (LRA) to reactivate HIV-1 has been proposed. However, the impact of LRA on the central nervous system (CNS) remains elusive.

Methods

We used human fetal astrocytes and investigated the effects of several LRA on their functional and secretory activities. Astrocytes were infected with VSV-G-pseudotyped HIV-1 before treatment with various blood-brain barrier (BBB)-permeable LRA at subcytotoxic doses, which allow HIV-1 reactivation based on previous in vitro and clinical studies. Cells and supernatants were then used to evaluate effects of infection and LRA on (i) viability and metabolic activity of astrocytes using a colorimetric MTS assay; (ii) chemokines and proinflammatory cytokines secretion and gene expression by astrocytes using ELISA and RT-qPCR, respectively; (iii) expression of complement component 3 (C3), a proxy for astrogliosis, by RT-qPCR; (iv) glutamate uptake capacity by a fluorometric assay; and (v) modulation of neutrophil transmigration across an in vitro BBB model.

Results

We demonstrate that bryostatin-1 induces secretion of chemokines CCL2 and IL-8 and proinflammatory cytokines IL-6 and GM-CSF, whereas their production is repressed by JQ1. Bryostatin-1 also increases expression of complement component 3 and perturbs astrocyte glutamate homeostasis. Lastly, bryostatin-1 enhances transmigration of neutrophils across an in vitro blood-brain barrier model and induces formation of neutrophil extracellular traps.

Conclusions

These observations highlight the need to carefully assess the potential harmful effect to the CNS when selecting LRA for HIV-1 reactivation strategies.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-1019-y) contains supplementary material, which is available to authorized users.

Reactivation of HIV-1 from Latency by an Ingenol Derivative from Euphorbia Kansui

Cells harboring latent HIV-1 pose a major obstacle to eradication of the virus. The ‘shock and kill’ strategy has been broadly explored to purge the latent reservoir; however, none of the current latency-reversing agents (LRAs) can safely and effectively activate the latent virus in patients. In this study, we report an ingenol derivative called EK-16A, isolated from the traditional Chinese medicinal herb Euphorbia kansui, which displays great potential in reactivating latent HIV-1. A comparison of the doses used to measure the potency indicated EK-16A to be 200-fold more potent than prostratin in reactivating HIV-1 from latently infected cell lines. EK-16A also outperformed prostratin in ex vivo studies on cells from HIV-1-infected individuals, while maintaining minimal cytotoxicity effects on cell viability and T cell activation. Furthermore, EK-16A exhibited synergy with other LRAs in reactivating latent HIV-1. Mechanistic studies indicated EK-16A to be a PKCγ activator, which promoted both HIV-1 transcription initiation by NF-κB and elongation by P-TEFb signal pathways. Further investigations aimed to add this compound to the therapeutic arsenal for HIV-1 eradication are in the pipeline.

Strategies to target non-T-cell HIV reservoirs

PURPOSE OF REVIEW

A central question for the HIV cure field is to determine new ways to target clinically relevant, latently and actively replicating HIV-infected cells beyond resting memory CD4 T cells, particularly in anatomical areas of low drug penetrability.

RECENT FINDINGS

HIV eradication strategies being positioned for targeting HIV for extinction in the CD4 T-cell compartment may also show promise in non-CD4 T-cells reservoirs. Furthermore, several exciting novel therapeutic approaches specifically focused on HIV clearance from non-CD4 T-cell populations are being developed.

SUMMARY

Although reservoir validity in these non-CD4 T cells continues to remain debated, this review will highlight recent advances and make an argument as to their clinical relevancy as we progress towards an HIV cure.

Preclinical shock strategies to reactivate latent HIV-1: an update

PURPOSE OF REVIEW

The 'shock and kill' strategy consists of activating HIV-1 expression to allow latently infected cells to die from viral cytopathic effects or host cytolytic immune effectors. This strategy relies on small molecules, called latency reversing agents, which activate HIV transcription.

RECENT FINDINGS

Several mechanisms operating at the transcriptional level are involved in the establishment and maintenance of HIV-1 latency, including the absence of crucial inducible host transcription factors, epigenetic silencing, and the sequestration of the positive transcription elongation factor B. Progresses made toward the understanding of the molecular mechanisms of HIV-1 transcriptional repression have led to the identification of latency reversing agents that activate HIV transcription, such as histone deacetylase inhibitors or protein kinase C agonists. Multiple studies have recently pointed interesting ways to optimize the shock strategy by using combinations of latency reversing agents with an appropriate time schedule.

SUMMARY

Combining latency reversing agents appears as one potential strategy for therapy against HIV-1 latency.

HIV-1 Latency and Eradication: Past, Present and Future

BACKGROUND

It is well established that antiretroviral therapy (ART), while highly effective in controlling HIV replication, cannot eliminate virus from the body. Therefore, the majority of HIV-1-infected individuals remain at risk for developing AIDS due to persistence of infected reservoir cells serving as a source of virus re-emergence. Several reservoirs containing replication competent HIV-1 have been identified, most notably CD4+ T cells. Cells of the myeloid lineage, which are the first line of defense against pathogens and participate in HIV dissemination into sanctuary organs, also serve as cellular reservoirs of HIV-1. In latently infected resting CD4+ T cells, the integrated copies of proviral DNA remain in a dormant state, yet possess the ability to produce replication competent virus after cellular activation. Studies have demonstrated that modification of chromatin structure plays a role in establishing persistence, in part suggesting that latency is, controlled epigenetically.

CONCLUSION

Current efforts to eradicate HIV-1 from this cell population focus primarily on a "shock and kill" approach through cellular reactivation to trigger elimination of virus producing cells by cytolysis or host immune responses. However, studies revealed several limitations to this approach that require more investigation to assess its clinical application. Recent advances in gene editing technology prompted use of this approach for inactivating integrated proviral DNA in the genome of latently infected cells. This technology, which requires a detailed understanding of the viral genetics and robust delivery, may serve as a powerful strategy to eliminate the latent reservoir in the host leading to a sterile cure of AIDS.

Novel nanoformulation to mitigate co-effects of drugs of abuse and HIV-1 infection: towards the treatment of NeuroAIDS

Drug abuse (e.g., methamphetamine-Meth or cocaine-Coc) is one of the major risk factors for becoming infected with HIV-1, and studies show that in combination, drug abuse and HIV-1 lead to significantly greater damage to CNS. To overcome these issues, we have developed a novel nanoformulation (NF) for drug-abusing population infected with HIV-1. In this work, a novel approach was developed for the co-encapsulation of Nelfinavir (Nel) and Rimcazole (Rico) using layer-by-layer (LbL) assembled magnetic nanoformulation for the cure of neuroAIDS. Developed NF was evaluated for blood-brain barrier (BBB) transmigration, cell uptake, cytotoxicity and efficacy (p24 assay) in HIV-1 infected primary astrocyte (HA) in presence or absence of Coc and Meth. Developed magnetic nanoformulation (NF) fabricated using the LbL approach exhibited higher amounts of drug loading (Nel and Rico) with 100% release of both the therapeutic agents in a sustained manner for 8 days. NF efficacy studies indicated a dose-dependent decrease in p24 levels in HIV-1-infected HA (~55%) compared to Coc + Meth treated (~50%). The results showed that Rico significantly subdued the effect of drugs of abuse on HIV infectivity. NF successfully transmigrated (38.8 ± 6.5%) across in vitro BBB model on the application of an external magnetic field and showed >90% of cell viability with efficient cell uptake. In conclusion, our proof of concept study revealed that sustained and concurrent release of sigma σ1 antagonist and anti-HIV drug from the developed novel sustained release NF can overcome the exacerbated effects of drugs of abuse in HIV infection and may solve the issue of medication adherence in the drug-abusing HIV-1 infected population.

On the way to find a cure: Purging latent HIV-1 reservoirs

Introduction of cART in 1996 has drastically increased the life expectancy of people living with HIV-1. However, this treatment has not allowed cure as cessation of cART is associated with a rapid viral rebound. The main barrier to the eradication of the virus is related to the persistence of latent HIV reservoirs. Evidence is now accumulating that purging the HIV-1 reservoir might lead to a cure or a remission. The most studied strategy is the so called "shock and kill" therapy. This strategy is based on reactivation of dormant viruses from the latently-infected reservoirs (the shock) followed by the eradication of the reservoirs (the kill). This review focuses mainly on the recent advances made in the "shock and kill" therapy. We believe that a cure or a remission will come from combinatorial approaches i.e. combination of drugs to reactivate the dormant virus from all the reservoirs including the one located in sanctuaries, and combination of strategies boosting the immune system. Alternative strategies based on cell and gene therapy or based in inducing deep latency, which are evoked in this review reinforce the idea that at least a remission is attainable.

An Updated Review on Marine Anticancer Compounds: The Use of Virtual Screening for the Discovery of Small-Molecule Cancer Drugs

Marine secondary metabolites are a promising source of unexploited drugs that have a wide structural diversity and have shown a variety of biological activities. These compounds are produced in response to the harsh and competitive conditions that occur in the marine environment. Invertebrates are considered to be among the groups with the richest biodiversity. To date, a significant number of marine natural products (MNPs) have been established as antineoplastic drugs. This review gives an overview of MNPs, both in research or clinical stages, from diverse organisms that were reported as being active or potentially active in cancer treatment in the past seventeen years (from January 2000 until April 2017) and describes their putative mechanisms of action. The structural diversity of MNPs is also highlighted and compared with the small-molecule anticancer drugs in clinical use. In addition, this review examines the use of virtual screening for MNP-based drug discovery and reveals that classical approaches for the selection of drug candidates based on ADMET (absorption, distribution, metabolism, excretion, and toxicity) filtering may miss potential anticancer lead compounds. Finally, we introduce a novel and publically accessible chemical library of MNPs for virtual screening purposes.

PKC-δ isoform plays a crucial role in Tat-TLR4 signalling pathway to activate NF-κB and CXCL8 production

HIV-1 Tat protein induces the production of CXCL8 chemokine in a TLR4/MD2 and PKC dependent manner. The objective of this study was to understand whether these two pathways were distinct or constituted a single common pathway, and to determine the nature of the PKC isoforms involved and their interrelation with the activation of NF-κB and CXCL8 gene product expression. Here, we show that Tat-induced CXCL8 production is essentially dependent on the activation of PKC delta isoform, as shown a) by the capacity of PKC delta dominant negative (DN), and Rottlerin, a selective PKC delta pharmacological inhibitor, to inhibit Tat-induced CXCL8 production and b) by the ability of the constitutively active (CAT) isoform of PKC delta to induce CXCL8 production in a HEK cell line in the absence of Tat stimulation. The finding that comparable amounts of CXCL8 were produced following stimulation with either Tat protein, PKC-delta CAT transfection, or both, argue for the implication of one common pathway where PKC delta is activated downstream of TLR4 recruitment and leads to the activation of NF-κB. Altogether, our results underline the crucial role of PKC delta isoform in activating gene expression of CXCL8, a cytokine largely implicated in the physiopathology of HIV-1 infection.

Promising Role of Toll-Like Receptor 8 Agonist in Concert with Prostratin for Activation of Silent HIV

The persistence of latently HIV-infected cells in patients under combined antiretroviral treatment (cART) remains the major hurdle for HIV eradication. Thus far, individual compounds have not been sufficiently potent to reactivate latent virus and guarantee its elimination in vivo. Thus, we hypothesized that transcriptional enhancers, in concert with compounds triggering the innate immune system, are more efficient in reversing latency by creating a Th1 supportive milieu that acts against latently HIV-infected cells at various levels. To test our hypothesis, we screened six compounds on a coculture of latently infected cells (J-lat) and monocyte-derived dendritic cells (MDDCs). The protein kinase C (PKC) agonist prostratin, with a Toll-like receptor 8 (TLR8) agonist, resulted in greater reversion of HIV latency than any single compound. This combinatorial approach led to a drastic phenotypic and functional maturation of the MDDCs. Tumor necrosis factor (TNF) and cell-cell interactions were crucial for the greater reversion observed. Similarly, we found a greater potency of the combination of prostratin and TLR8 agonist in reversing HIV latency when applying it to primary cells of HIV-infected patients. Thus, we demonstrate here the synergistic interplay between TLR8-matured MDDCs and compounds acting directly on latently HIV-infected cells, targeting different mechanisms of latency, by triggering various signaling pathways. Moreover, TLR8 triggering may reverse exhaustion of HIV-specific cytotoxic T lymphocytes that might be essential for killing or constraining the latently infected cells.

IMPORTANCE

Curing HIV is the Holy Grail. The so-called "shock and kill" strategy relies on drug-mediated reversion of HIV latency and the subsequent death of those cells under combined antiretroviral treatment. So far, no compound achieves efficient reversal of latency or eliminates this latent reservoir. The compounds may not target all of the latency mechanisms in all latently infected cells. Moreover, HIV-associated exhaustion of the immune system hinders the efficient elimination of the reactivated cells. In this study, we demonstrated synergistic latency reversion by combining agonists for protein kinase C and Toll-like receptor 8 in a coculture of latently infected cells with myeloid dendritic cells. The drug prostratin stimulates directly the transcriptional machinery of latently infected cells, and the TLR8 agonist acts indirectly by maturing dendritic cells. These findings highlight the importance of the immune system and its activation, in combination with direct-acting compounds, to reverse latency.

HIV Latency: Should We Shock or Lock?

Combinatory antiretroviral therapy (cART) increases the survival and quality of life of HIV-1-infected patients. However, interruption of therapy almost invariably leads to the re-emergence of detectable viral replication because HIV-1 persists in viral latent reservoirs. Improved understanding of the molecular mechanisms involved in HIV-1 latency has paved the way for innovative strategies that attempt to purge latent virus. In this article we discuss the results of the broadly explored 'shock and kill' strategy, and also highlight the major hurdles facing this approach. Finally, we present recent innovative works suggesting that locking out latent proviruses could be a potential alternative therapeutic strategy.

HIV-1 Latency-Reversing Agents Prostratin and Bryostatin-1 Induce Blood-Brain Barrier Disruption/Inflammation and Modulate Leukocyte Adhesion/Transmigration

A shock-and-kill approach involving the simultaneous treatment of HIV-1-infected patients with latency-reversing agents (LRAs) and combination antiretroviral therapy was proposed as a means to eradicate viral reservoirs. Currently available LRAs cannot discriminate between HIV-1-infected and uninfected cells. Therefore, the risks and benefits of using broad-spectrum LRAs need to be carefully evaluated, particularly in the CNS, where inflammation and leukocyte transmigration must be tightly regulated. We used a real-time impedance-sensing system to dynamically record the impact of different classes of LRAs on the integrity of tight monolayers of the immortalized human cerebral microvascular endothelial cell line hCMEC/D3. Results show that prostratin and bryostatin-1 can significantly damage the integrity of an endothelial monolayer. Moreover, prostratin and bryostatin-1 induce secretion of some proinflammatory cytokines and an increase of ICAM-1 expression. Additional studies demonstrated that prostratin and bryostatin-1 also affect adhesion and transmigration of CD4⁺ and CD8⁺ T cells as well as monocytes in an in vitro human blood-brain barrier (BBB) model. Prostratin and bryostatin-1 could thus be considered as potent regulators of BBB permeability and inflammation that influence leukocyte transport across the BBB. Altogether, these findings contribute to a better understanding of the potential risks and benefits of using a shock-and-kill approach with LRAs on the normal physiological functions of the BBB.

In vitro effects of the small-molecule protein kinase C agonists on HIV latency reactivation

The persistence of latently HIV-infected cellular reservoirs represents the major obstacle to virus eradication in patients under antiretroviral therapy (ART). Cure strategies to eliminate these reservoirs are thus needed to reactivate proviral gene expression in latently infected cells. In this study, we tested optimal concentrations of PKC agonist candidates (PEP005/Ingenol-3-angelate, prostratin, bryostatin-1, and JQ1) to reactivate HIV latency in vitro, and examined their effects on cell survival, activation and epigenetic histone methylation after treatment alone or in combination in cell line and isolated CD4 T cells from SIV-infected macaques. The results showed that PKC agonists increased cell activation with different degrees of latency reactivation, concomitant with reduced levels of histone methylation. With increasing concentrations, prostratin and byrostain-1 treatment rapidly reduced cell survival and cell activation. The PKC agonist combinations, or in combination with JQ1, led to modest levels of synergistic reactivation of HIV. Remarkably, PEP005 treatment alone caused marked reactivation of HIV latency, similar to PMA stimulation. These findings suggested that PEP005 alone, as indicated its lower cytotoxicity and lower effective dose inducing maximal reactivation, might be a candidate for effectively reactivating HIV latency as part of a therapeutic strategy for HIV infection.

Targeting the Brain Reservoirs: Toward an HIV Cure

One of the top research priorities of the international AIDS society by the action “Towards an HIV Cure” is the purge or the decrease of the pool of all latently infected cells. This strategy is based on reactivation of latently reservoirs (the shock) followed by an intensifying combination antiretroviral therapy (cART) to kill them (the kill). The central nervous system (CNS) has potential latently infected cells, i.e., perivascular macrophages, microglial cells, and astrocytes that will need to be eliminated. However, the CNS has several characteristics that may preclude the achievement of a cure. In this review, we discuss several limitations to the eradication of brain reservoirs and how we could circumvent these limitations by making it efforts in four directions: (i) designing efficient latency-reversal agents for CNS-cell types, (ii) improving cART by targeting HIV transcription, (iii) improving delivery of HIV drugs in the CNS and in the CNS-cell types, and (iv) developing therapeutic immunization. As a prerequisite to these efforts, we also believe that a better comprehension of molecular mechanisms involved in establishment and persistence of HIV latency in brain reservoirs are essential to design new molecules for strategies aiming to achieve a cure for instance the “shock and kill” strategy.

Comparative analysis of the anti-chikungunya virus activity of novel bryostatin analogs confirms the existence of a PKC-independent mechanism

Previously, we reported that salicylate-based analogs of bryostatin protect cells from chikungunya virus (CHIKV)-induced cell death. Interestingly, 'capping' the hydroxyl group at C26 of a lead bryostatin analog, a position known to be crucial for binding to and modulation of protein kinase C (PKC), did not abrogate the anti-CHIKV activity of the scaffold, putatively indicating the involvement of a pathway independent of PKC. The work detailed in this study demonstrates that salicylate-derived analog 1 and two capped analogs (2 and 3) are not merely cytoprotective compounds, but act as selective and specific inhibitors of CHIKV replication. Further, a detailed comparative analysis of the effect of the non-capped versus the two capped analogs revealed that compound 1 acts both at early and late stages in the chikungunya virus replication cycle, while the capped analogs only interfere with a later stage process. Co-dosing with the PKC inhibitors sotrastaurin and Gö6976 counteracts the antiviral activity of compound 1 without affecting that of capped analogs 2 and 3, providing further evidence that the latter elicit their anti-CHIKV activity independently of PKC. Remarkably, treatment of CHIKV-infected cells with a combination of compound 1 and a capped analog resulted in a pronounced synergistic antiviral effect. Thus, these salicylate-based bryostatin analogs can inhibit CHIKV replication through a novel, yet still elusive, non-PKC dependent pathway.

Bryostatin-1 for latent virus reactivation in HIV-infected patients on antiretroviral therapy

OBJECTIVE

The protein kinase C (PKC) agonist bryostatin-1 has shown significant ex-vivo potency to revert HIV-1 latency, compared with other latency reversing agents (LRA). The safety of this candidate LRA remains to be proven in treated HIV-1-infected patients.

METHODS

In this pilot, double-blind phase I clinical-trial (NCT 02269605), we included aviraemic HIV-1-infected patients on triple antiretroviral therapy to evaluate the effects of two different single doses of bryostatin-1 (10 or 20 μg/m) compared with placebo.

RESULTS

Twelve patients were included, four in each arm. Bryostatin-1 was well tolerated in all participants. Two patients in the 20 μg/m arm developed grade 1 headache and myalgia. No detectable increases of cell-associated unspliced (CA-US) HIV-1-RNA were observed in any study arm, nor differences in HIV-1 mRNA dynamics between arms (P = 0.44). The frequency of samples with low-level viraemia did not differ between arms and low-level viraemia did not correlate with CA-US HIV-1-RNA levels (P = 0.676). No changes were detected on protein kinase C (PKC) activity and in biomarkers of inflammation (sCD14 and interleukin-6) in any study arm. After the single dose of bryostatin-1, plasma concentrations were under detection limits in all the patients in the 10 μg/m arm, and below 50 pg/ml (0.05 nmol/l) in those in the 20 μg/m arm.

CONCLUSION

Bryostatin-1 was safe at the single doses administered. However, the drug did not show any effect on PKC activity or on the transcription of latent HIV, probably due to low plasma concentrations. This study will inform next trials aimed at assessing higher doses, multiple dosing schedules or combination studies with synergistic drugs.

TGF-β1 Upregulates the Expression of Triggering Receptor Expressed on Myeloid Cells 1 in Murine Lungs

Triggering receptor expressed on myeloid cells 1 (TREM-1) increases the expression of TGF-β family genes, which are known as profibrogenic cytokines in the pathogenesis of pulmonary fibrosis. In this study, we determined whether TGF-β1 regulated the expression of TREM-1 in a mouse model of pulmonary fibrosis. The expression of TGF-β1 and TREM-1 was increased on day 7, 14, and 21 after single intratracheal injection of bleomycin (BLM). And there was positive correlation between the expression of TGF-β1 and TREM-1. TGF-β1 increased expression of TREM-1 mRNA and protein in a time- and dose-dependent manner in mouse macrophages. The expression of the activator protein 1 (AP-1) was increased in lung tissues from mouse after BLM injection and in mouse macrophages after TGF-β1 treatment, respectively. TGF-β1 significantly increased the relative activity of luciferase in the cells transfected with plasmid contenting wild type-promoter of TREM-1. But TGF-β1 had no effect on the activity of luciferase in the cells transfected with a mutant-TREM1 plasmid carrying mutations in the AP-1 promoter binding site. In conclusion, we found the expression of TREM-1 was increased in lung tissues from mice with pulmonary fibrosis. TGF-β1 increased the expression of TREM-1 in mouse macrophages partly via the transcription factor AP-1.

New Drugs from Marine Organisms in Alzheimer's Disease

Alzheimer’s disease (AD) is a multifactorial neurodegenerative disorder. Current approved drugs may only ameliorate symptoms in a restricted number of patients and for a restricted period of time. Currently, there is a translational research challenge into identifying the new effective drugs and their respective new therapeutic targets in AD and other neurodegenerative disorders. In this review, selected examples of marine-derived compounds in neurodegeneration, specifically in AD field are reported. The emphasis has been done on compounds and their possible relevant biological activities. The proposed drug development paradigm and current hypotheses should be accurately investigated in the future of AD therapy directions although taking into account successful examples of such approach represented by Cytarabine, Trabectedin, Eribulin and Ziconotide. We review a complexity of the translational research for such a development of new therapies for AD. Bryostatin is a prominent candidate for the therapy of AD and other types of dementia in humans.

HIV-1 increases TLR responses in human primary astrocytes

Astrocytes are the major glial cell within the central nervous system and have a number of important physiological properties related to brain homeostasis. They provide trophic support to neurons and are immune cells with key roles during states-of-inflammation. The potential for production of proinflammatory cytokines and its consequences has been studied in the context of HIV-1 infection of normal human astrocytes (NHA). NHA express TLR3, TLR4, and TLR5. TLR3 ligation induced the strongest proinflammatory polarizing response, characterized by generation of high levels of TNF-α, IL-6, and IL-8. HIV-1 increased the transient production of key inflammatory mediators, and exposure to LPS of HIV-1-infected cells increased significantly the cytokine secretion. We confirmed that it is necessary viral gene expression from the moment of pretreatment with antiretrovirals inhibited totally HIV-1-induced TLR response. The higher response to LPS from HIV-1-infected cells did not correlate with TLR4 or MyD88 increased expression. LPS responsiveness of infected cells parallels MHC class II expression, but not CD14. HIV-1-infected NHA present increased sensitivity to the proinflammatory effects of LPS. If this phenomenon occurs in vivo, it will contribute to the immunopathogenesis of this disease and may ultimately offer novel targets for immunomodulatory therapy.

HIV-1, methamphetamine and astrocytes at neuroinflammatory Crossroads

As a popular psychostimulant, methamphetamine (METH) use leads to long-lasting, strong euphoric effects. While METH abuse is common in the general population, between 10 and 15% of human immunodeficiency virus-1 (HIV-1) patients report having abused METH. METH exacerbates the severity and onset of HIV-1-associated neurocognitive disorders (HAND) through direct and indirect mechanisms. Repetitive METH use impedes adherence to antiretroviral drug regimens, increasing the likelihood of HIV-1 disease progression toward AIDS. METH exposure also directly affects both innate and adaptive immunity, altering lymphocyte numbers and activity, cytokine signaling, phagocytic function and infiltration through the blood brain barrier. Further, METH triggers the dopamine reward pathway and leads to impaired neuronal activity and direct toxicity. Concurrently, METH and HIV-1 alter the neuroimmune balance and induce neuroinflammation, which modulates a wide range of brain functions including neuronal signaling and activity, glial activation, viral infection, oxidative stress, and excitotoxicity. Pathologically, reactive gliosis is a hallmark of both HIV-1- and METH-associated neuroinflammation. Significant commonality exists in the neurotoxic mechanisms for both METH and HAND; however, the pathways dysregulated in astroglia during METH exposure are less clear. Thus, this review highlights alterations in astrocyte intracellular signaling pathways, gene expression and function during METH and HIV-1 comorbidity, with special emphasis on HAND-associated neuroinflammation. Importantly, this review carefully evaluates interventions targeting astrocytes in HAND and METH as potential novel therapeutic approaches. This comprehensive overview indicates, without a doubt, that during HIV-1 infection and METH abuse, a complex dialog between all neural cells is orchestrated through astrocyte regulated neuroinflammation.