A candidate anti-HIV reservoir compound, auranofin, exerts a selective 'anti-memory' effect by exploiting the baseline oxidative status of lymphocytes

Monocyte to macrophage differentiation and changes in cellular redox homeostasis promote cell type-specific HIV latency reactivation

HIV latency regulation in monocytes and macrophages can vary according to signals directing differentiation, polarization, and function. To investigate these processes, we generated an HIV latency model in THP-1 monocytes and showed differential levels of HIV reactivation among clonal populations. Monocyte-to-macrophage differentiation of HIV-infected primary human CD14+ and THP-1 cells induced HIV reactivation and showed that virus production increased concomitant with macrophage differentiation. We applied the HIV-infected THP-1 monocyte-to-macrophage (MLat) model to assess the biological mechanisms regulating HIV latency dynamics during monocyte-to-macrophage differentiation. We pinpointed protein kinase C signaling pathway activation and Cyclin T1 upregulation as inherent differentiation mechanisms that regulate HIV latency reactivation. Macrophage polarization regulated latency, revealing proinflammatory M1 macrophages suppressed HIV reactivation while anti-inflammatory M2 macrophages promoted HIV reactivation. Because macrophages rely on reactive-oxygen species (ROS) to exert numerous cellular functions, we disrupted redox pathways and found that inhibitors of the thioredoxin (Trx) system acted as latency-promoting agents in T-cells and monocytes, but opposingly acted as latency-reversing agents in macrophages. We explored this mechanism with Auranofin, a clinical candidate for reducing HIV reservoirs, and demonstrated Trx reductase inhibition led to ROS induced NF-κB activity, which promoted HIV reactivation in macrophages, but not in T-cells and monocytes. Collectively, cell type-specific differences in HIV latency regulation could pose a barrier to HIV eradication strategies.

Next Generation Gold Drugs and Probes: Chemistry and Biomedical Applications

The gold drugs, gold sodium thiomalate (Myocrisin), aurothioglucose (Solganal), and the orally administered auranofin (Ridaura), are utilized in modern medicine for the treatment of inflammatory arthritis including rheumatoid and juvenile arthritis; however, new gold agents have been slow to enter the clinic. Repurposing of auranofin in different disease indications such as cancer, parasitic, and microbial infections in the clinic has provided impetus for the development of new gold complexes for biomedical applications based on unique mechanistic insights differentiated from auranofin. Various chemical methods for the preparation of physiologically stable gold complexes and associated mechanisms have been explored in biomedicine such as therapeutics or chemical probes. In this Review, we discuss the chemistry of next generation gold drugs, which encompasses oxidation states, geometry, ligands, coordination, and organometallic compounds for infectious diseases, cancer, inflammation, and as tools for chemical biology via gold-protein interactions. We will focus on the development of gold agents in biomedicine within the past decade. The Review provides readers with an accessible overview of the utility, development, and mechanism of action of gold-based small molecules to establish context and basis for the thriving resurgence of gold in medicine.

The reservoir of latent HIV

The persistence of latent reservoir of the human immunodeficiency virus (HIV) is currently the major challenge in curing HIV infection. After HIV infects the human body, the latent HIV is unable to be recognized by the body’s immune system. Currently, the widely adopted antiretroviral therapy (ART) is also unble to eliminate it, thus hindering the progress of HIV treatment. This review discusses the existence of latent HIV vault for HIV treatment, its formation and factors affecting its formation, cell, and tissue localization, methods for detection and removing latent reservoir, to provide a comprehensive understanding of latent HIV vault, in order to assist in the future research and play a potential role in achieving HIV treatment.

Broad Spectrum Functional Activity of Structurally Related Monoanionic Au(III) Bis(Dithiolene) Complexes

The biological properties of sixteen structurally related monoanionic gold (III) bis(dithiolene/diselenolene) complexes were evaluated. The complexes differ in the nature of the heteroatom connected to the gold atom (AuS for dithiolene, AuSe for diselenolene), the substituent on the nitrogen atom of the thiazoline ring (Me, Et, Pr, iPr and Bu), the nature of the exocyclic atom or group of atoms (O, S, Se, C(CN)₂) and the counter-ion (Ph₄P⁺ or Et₄N⁺). The anticancer and antimicrobial activities of all the complexes were investigated, while the anti-HIV activity was evaluated only for selected complexes. Most complexes showed relevant anticancer activities against Cisplatin-sensitive and Cisplatin-resistant ovarian cancer cells A2780 and OVCAR8, respectively. After 48 h of incubation, the IC₅₀ values ranged from 0.1–8 µM (A2780) and 0.8–29 µM (OVCAR8). The complexes with the Ph₄P⁺ ([P]) counter-ion are in general more active than their Et₄N⁺ ([N]) analogues, presenting IC₅₀ values in the same order of magnitude or even lower than Auranofin. Studies in the zebrafish embryo model further showed that, despite their marked anticancer effect, the complexes with [P] counter-ion exhibited low in vivo toxicity. In general, the exocyclic exchange of sulfur by oxygen or ylidenemalononitrile (C(CN)₂) enhanced the compounds toxicity. Most complexes containing the [P] counter ion exhibited exceptional antiplasmodial activity against the Plasmodium berghei parasite liver stages, with submicromolar IC₅₀ values ranging from 400–700 nM. In contrast, antibacterial/fungi activities were highest for most complexes with the [N] counter-ion. Auranofin and two selected complexes [P][AuSBu(=S)] and [P][AuSEt(=S)] did not present anti-HIV activity in TZM-bl cells. Mechanistic studies for selected complexes support the idea that thioredoxin reductase, but not DNA, is a possible target for some of these complexes. The complexes [P] [AuSBu(=S)], [P] [AuSEt(=S)], [P] [AuSEt(=Se)] and [P] [AuSeiPr(=S)] displayed a strong quenching of the fluorescence intensity of human serum albumin (HSA), which indicates a strong interaction with this protein. Overall, the results highlight the promising biological activities of these complexes, warranting their further evaluation as future drug candidates with clinical applicability.

Redox proteome analysis of auranofin exposed ovarian cancer cells (A2780)

The effects of Auranofin (AF) on protein expression and protein oxidation in A2780 cancer cells were investigated through a strategy based on simultaneous expression proteomics and redox proteomics determinations. Bioinformatics analysis of the proteomics data supports the view that the most critical cellular changes elicited by AF treatment consist of thioredoxin reductase inhibition, alteration of the cell redox state, impairment of the mitochondrial functions, metabolic changes associated with conversion to a glycolytic phenotype, induction of ER stress. The occurrence of the above cellular changes was extensively validated by performing direct biochemical assays. Our data are consistent with the concept that AF produces its effects through a multitarget mechanism that mainly affects the redox metabolism and the mitochondrial functions and results into severe ER stress. Results are discussed in the context of the current mechanistic knowledge existing on AF.

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Redox proteomics allows to underline cell adaptation mechanisms in response to Auranofin treatment in ovarian cancer cells.

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BRCA1 is one of the major candidates of the ovarian cancer cell adaptation to Auranofin treatment.

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Auranofin alters the oxidative phosphorylation and mitochondrial protein import machinery.

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TRAP1 C501 modulates Auranofin toxicity.

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Auranofin induces severe stress of the endoplasmic reticulum.

Black phosphorus-Au-thiosugar nanosheets mediated photothermal induced anti-tumor effect enhancement by promoting infiltration of NK cells in hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is a heterogeneous cancer required combination therapy, such as photothermal therapy and chemotherapy. In recent years, cancer immunotherapies are rapidly evolving and are some of the most promising avenues to approach malignancies. Thus, the combination of the traditional therapies and immunotherapy in one platform may improve the efficacy for HCC treatment.

Results

In this work, we have prepared a black phosphorus (BP)-Au-thiosugar nanosheets (BATNS), in which Au-thiosugar coating and functionalization improved the stability of both black phosphorus nanosheets (BPNS) and gold ions in different simulated physiological environments. The compression of the BATNS band gap can convert more photon energy to heat generation compared with BPNS, resulting in higher photothermal conversion efficiency. The in vitro and in vivo results also revealed a stronger reduction on the hepatocellular carcinoma of mice and prolonged survival of disease models compared with BPNS. More importantly, BATNS showed an additional immune effect by increasing local NK cell infiltration but not T cell on the liver cancer treatment, and this immune effect was caused by the thermal effect of BATNS photothermal treatment.

Conclusions

The novel BATNS could improve the stability of BPNS and simultaneously combine the cancer thermotherapy and immunotherapy leaded by local NK cell infiltration, resulting in a better therapeutic efficacy on hepatocellular carcinoma. This work also provided a new path to design BP-based materials for biomedical applications.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01286-z.

Immunogenicity of personalized dendritic-cell therapy in HIV-1 infected individuals under suppressive antiretroviral treatment: interim analysis from a phase II clinical trial

Background

We developed a personalized Monocyte-Derived Dendritic-cell Therapy (MDDCT) for HIV-infected individuals on suppressive antiretroviral treatment and evaluated HIV-specific T-cell responses.

Methods

PBMCs were obtained from 10 HIV⁺ individuals enrolled in trial NCT02961829. Monocytes were differentiated into DCs using IFN-α and GM-CSF. After sequencing each patient’s HIV-1 Gag and determining HLA profiles, autologous Gag peptides were selected based on the predicted individual immunogenicity and used to pulse MDDCs. Three doses of the MDDCT were administered every 15 days. To assess immunogenicity, patients’ cells were stimulated in vitro with autologous peptides, and intracellular IL-2, TNF, and interferon-gamma (IFN-γ) production were measured in CD4⁺ and CD8⁺ T-cells.

Results

The protocol of ex-vivo treatment with IFN-α and GM-CSF was able to induce maturation of MDDCs, as well as to preserve their viability for reinfusion. MDDCT administration was associated with increased expression of IL-2 in CD4⁺ and CD8⁺ T-cells at 15 and/or 30 days after the first MDDCT administration. Moreover, intracellular TNF and IFN-γ expression was significantly increased in CD4⁺ T-cells. The number of candidates that increased in vitro the cytokine levels in CD4⁺ and CD8⁺ T cells upon stimulation with Gag peptides from baseline to day 15 and from baseline to day 30 and day 120 after MDDCT was significant as compared to Gag unstimulated response. This was accompanied by an increasing trend in the frequency of polyfunctional T-cells over time, which was visible when considering both cells expressing two and three out of the three cytokines examined.

Conclusions

MDDC had a mature profile, and this MDDCT promoted in-vitro T-cell immune responses in HIV-infected patients undergoing long-term suppressive antiretroviral treatment.

Trial registration NCT02961829: (Multi Interventional Study Exploring HIV-1 Residual Replication: a Step Towards HIV-1 Eradication and Sterilizing Cure, https://www.clinicaltrials.gov/ct2/show/NCT02961829, posted November 11th, 2016)

Supplementary Information

The online version contains supplementary material available at 10.1186/s12981-021-00426-z.

Hydrogen sulfide blocks HIV rebound by maintaining mitochondrial bioenergetics and redox homeostasis

A fundamental challenge in human immunodeficiency virus (HIV) eradication is to understand how the virus establishes latency, maintains stable cellular reservoirs, and promotes rebound upon interruption of antiretroviral therapy (ART). Here, we discovered an unexpected role of the ubiquitous gasotransmitter hydrogen sulfide (H₂S) in HIV latency and reactivation. We show that reactivation of HIV is associated with downregulation of the key H₂S producing enzyme cystathionine-γ-lyase (CTH) and reduction in endogenous H₂S. Genetic silencing of CTH disrupts redox homeostasis, impairs mitochondrial function, and remodels the transcriptome of latent cells to trigger HIV reactivation. Chemical complementation of CTH activity using a slow-releasing H₂S donor, GYY4137, suppressed HIV reactivation and diminished virus replication. Mechanistically, GYY4137 blocked HIV reactivation by inducing the Keap1-Nrf2 pathway, inhibiting NF-κB, and recruiting the epigenetic silencer, YY1, to the HIV promoter. In latently infected CD4⁺ T cells from ART-suppressed human subjects, GYY4137 in combination with ART prevented viral rebound and improved mitochondrial bioenergetics. Moreover, prolonged exposure to GYY4137 exhibited no adverse influence on proviral content or CD4⁺ T cell subsets, indicating that diminished viral rebound is due to a loss of transcription rather than a selective loss of infected cells. In summary, this work provides mechanistic insight into H₂S-mediated suppression of viral rebound and suggests exploration of H₂S donors to maintain HIV in a latent form.

Will Auranofin Become a Golden New Treatment Against COVID-19?

Auranofin is an FDA-approved disease-modifying anti-rheumatic drug that has been used for decades for treatment of rheumatoid arthritis. This gold(I) compound has anti-inflammatory properties because it reduces IL-6 expression via inhibition of the NF-κB-IL-6-STAT3 signaling pathway. Also, by inhibiting redox enzymes such as thioredoxin reductase, auranofin increases cellular oxidative stress and promotes apoptosis. Auranofin also possesses antiviral properties. Recently, it was reported that auranofin reduced by 95% SARS-CoV-2 RNA in infected human cells in vitro and decreased SARS-CoV-2-induced cytokine expression, including IL-6. During SARS-CoV-2 infection, a cytokine storm involving IL-6 increases severity of illness and worsens prognosis. Therefore, auranofin could, in our point of view, reduce pathology due to SARS-CoV-2-induced IL-6. COVID-19 is a rapidly-evolving respiratory disease now distributed worldwide. Strikingly high numbers of new COVID-19 cases are reported daily. We have begun a race to vaccinate people, but due to the complex logistics of this effort, the virus will continue to spread before all humans can be immunized, and new variants that may be less well contained by current vaccines are of concern. The COVID-19 pandemic has overwhelmed health care systems and new treatments to reduce mortality are urgently needed. We encourage to further evaluate the potential of auranofin in the treatment of COVID-19 in vitro and in animal models of SARS-CoV-2 infection and, if preliminary data are promising, in clinical trials with COVID-19 patients. In our opinion, auranofin has the potential to become a valuable addition to available therapies in this pandemic.

Glycolysis downregulation is a hallmark of HIV-1 latency and sensitizes infected cells to oxidative stress

HIV-1 infects lymphoid and myeloid cells, which can harbor a latent proviral reservoir responsible for maintaining lifelong infection. Glycolytic metabolism has been identified as a determinant of susceptibility to HIV-1 infection, but its role in the development and maintenance of HIV-1 latency has not been elucidated. By combining transcriptomic, proteomic, and metabolomic analyses, we here show that transition to latent HIV-1 infection downregulates glycolysis, while viral reactivation by conventional stimuli reverts this effect. Decreased glycolytic output in latently infected cells is associated with downregulation of NAD+ /NADH. Consequently, infected cells rely on the parallel pentose phosphate pathway and its main product, NADPH, fueling antioxidant pathways maintaining HIV-1 latency. Of note, blocking NADPH downstream effectors, thioredoxin and glutathione, favors HIV-1 reactivation from latency in lymphoid and myeloid cellular models. This provides a "shock and kill effect" decreasing proviral DNA in cells from people living with HIV/AIDS. Overall, our data show that downmodulation of glycolysis is a metabolic signature of HIV-1 latency that can be exploited to target latently infected cells with eradication strategies.

[Potential Anticancer Activity of Auranofin]

Gold compounds have been employed throughout history to treat various types of disease, from ancient times to the present day. In the year 1985, auranofin, a gold-containing compound, was approved by U.S. Food and Drug Administration (FDA) as a therapeutic agent to target rheumatoid arthritis that would facilitate easy oral drug administration as opposed to conventional intramuscular injection used in treatments. Furthermore, auranofin demonstrates promising results for the treatment of various diseases beyond rheumatoid arthritis, including cancer, neurodegenerative diseases, acquired immune deficiency syndrome, and bacterial and parasitic infections. Various potential novel applications for auranofin have been proposed for treating human diseases. Auranofin has previously been demonstrated to inhibit thioredoxin reductase (TrxR) involved within the thioredoxin (Trx) system that comprises one of the critical cellular redox systems within the body. TrxR comprises the sole known enzyme that catalyzes Trx reduction. With cancers in particular, TrxR inhibition facilitates an increase in cellular oxidative stress and suppresses tumor growth. In this review, we describe the potential of auranofin to serve as an anticancer agent and further drug repurposing to utilize this as a strategy for further appropriate drug developments.

Antioxidant nanozyme counteracts HIV-1 by modulating intracellular redox potential

Reactive oxygen species (ROS) regulates the replication of human immunodeficiency virus (HIV‐1) during infection. However, the application of this knowledge to develop therapeutic strategies remained unsuccessful due to the harmful consequences of manipulating cellular antioxidant systems. Here, we show that vanadium pentoxide (V₂O₅) nanosheets functionally mimic natural glutathione peroxidase activity to mitigate ROS associated with HIV‐1 infection without adversely affecting cellular physiology. Using genetic reporters of glutathione redox potential and hydrogen peroxide, we showed that V₂O₅ nanosheets catalyze ROS neutralization in HIV‐1‐infected cells and uniformly block viral reactivation and replication. Mechanistically, V₂O₅ nanosheets suppressed HIV‐1 by affecting the expression of pathways coordinating redox balance, virus transactivation (e.g., NF‐κB), inflammation, and apoptosis. Importantly, a combination of V₂O₅ nanosheets with a pharmacological inhibitor of NF‐κB (BAY11‐7082) abrogated reactivation of HIV‐1. Lastly, V₂O₅ nanosheets inhibit viral reactivation upon prostratin stimulation of latently infected CD4⁺ T cells from HIV‐infected patients receiving suppressive antiretroviral therapy. Our data successfully revealed the usefulness of V₂O₅ nanosheets against HIV and suggested nanozymes as future platforms to develop interventions against infectious diseases.

What is holding back the development of antiviral metallodrugs? A literature overview and implications for SARS-CoV-2 therapeutics and future viral outbreaks

In light of the Covid-19 outbreak, this review brings together historical and current literature efforts towards the development of antiviral metallodrugs. Classical compounds such as CTC-96 and auranofin are discussed in depth, as pillars for future metallodrug development. From the recent literature, both cell-based results and biophysical assays against potential viral biomolecule targets are summarized here. The comprehension of the biomolecular targets and their interactions with coordination compounds are emphasized as fundamental strategies that will foment further development of metal-based antivirals. We also discuss other possible and unexplored methods for unveiling metallodrug interactions with biomolecules related to viral replication and highlight the specific challenges involved in the development of antiviral metallodrugs.

Role of Oxidative Stress on SARS-CoV (SARS) and SARS-CoV-2 (COVID-19) Infection: A Review

Novel coronavirus disease 2019 (COVID-19) has resulted in a global pandemic and is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Several studies have suggested that a precise disulfide-thiol balance is crucial for viral entry and fusion into the host cell and that oxidative stress generated from free radicals can affect this balance. Here, we reviewed the current knowledge about the role of oxidative stress on SARS-CoV and SARS-CoV-2 infections. We focused on the impact of antioxidants, like NADPH and glutathione, and redox proteins, such as thioredoxin and protein disulfide isomerase, that maintain the disulfide-thiol balance in the cell. The possible influence of these biomolecules on the binding of viral protein with the host cell angiotensin-converting enzyme II receptor protein as well as on the severity of COVID-19 infection was discussed.

The FDA-approved gold drug auranofin inhibits novel coronavirus (SARS-COV-2) replication and attenuates inflammation in human cells

SARS-COV-2 has recently emerged as a new public health threat. Herein, we report that the FDA-approved drug, auranofin, inhibits SARS-COV-2 replication in human cells at low micro molar concentration. Treatment of cells with auranofin resulted in a 95% reduction in the viral RNA at 48 h after infection. Auranofin treatment dramatically reduced the expression of SARS-COV-2-induced cytokines in human cells. These data indicate that auranofin could be a useful drug to limit SARS-CoV-2 infection and associated lung injury due to its antiviral, anti-inflammatory and anti-reactive oxygen species (ROS) properties. Further animal studies are warranted to evaluate the safety and efficacy of auranofin for the management of SARS-COV-2 associated disease.

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Auranofin inhibits replication of SARS-COV-2 in human cells at low micro molar concentration.

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Auranofin treatment resulted in significant reduction in SARS-COV-2-induced cytokines in human cells.

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Auranofin could mitigate SARS-COV-2 infection and lung damage due to its anti-viral and anti-inflammatory properties.

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Auranofin is a gold-containing FDA-approved drug.

Alterations of redox and iron metabolism accompany the development of HIV latency

HIV-1 persists in a latent form during antiretroviral therapy, mainly in CD4+ T cells, thus hampering efforts for a cure. HIV-1 infection is accompanied by metabolic alterations, such as oxidative stress, but the effect of cellular antioxidant responses on viral replication and latency is unknown. Here, we show that cells survive retroviral replication, both in vitro and in vivo in SIVmac-infected macaques, by upregulating antioxidant pathways and the intertwined iron import pathway. These changes are associated with remodeling of promyelocytic leukemia protein nuclear bodies (PML NBs), an important constituent of nuclear architecture and a marker of HIV-1 latency. We found that PML NBs are hyper-SUMOylated and that PML protein is degraded via the ubiquitin-proteasome pathway in productively infected cells, before latency establishment and after reactivation. Conversely, normal numbers of PML NBs were restored upon transition to latency or by decreasing oxidative stress or iron content. Our results highlight antioxidant and iron import pathways as determinants of HIV-1 latency and support their pharmacologic inhibition as tools to regulate PML stability and impair latency establishment.

Crossroads of Cancer and HIV-1: Pathways to a Cure for HIV

Recently, a second individual (the “London patient”) with HIV-1 infection and concomitant leukemia was cured of both diseases by a conditioning myeloablative regimen followed by transplantation of stem cells bearing the homozygous CCR5 Δ32 mutation. The substantial risks and cost associated with this procedure render it unfeasible on a large scale. This strategy also indicates that a common pathway toward a cure for both HIV and cancer may exist. Successful approaches to curing both diseases should ideally possess three components, i.e., (1) direct targeting of pathological cells (neoplastic cells in cancer and the HIV-infected reservoir cells), (2) subsequent impediment to reconstitution of the pool of pathological cells and (3) sustained, immunologic control of the disease (both diseases are characterized by detrimental immune hyper-activation that hinders successful establishment of immunity). In this review, we explore medications that are either investigational or FDA-approved anticancer treatments that may be employed to achieve the goal of curing HIV-1. These include: thioredoxin reductase inhibitors (phases 1–3), immune checkpoint inhibitors (phases 1, 3), Jak inhibitors (FDA approved for arthritis and multiple cancer indications, summarized in Table 1). Of note, some of these medications such as arsenic trioxide and Jak inhibitors may also reversibly down regulate CCR5 expression on CD4⁺ T-cells, thus escaping the ethical issues of inducing or transferring mutations in CCR5 that are presently the subject of interest as it relates to HIV-1 cure strategies.

Potential impact of the antirheumatic agent auranofin on proviral HIV-1 DNA in individuals under intensified antiretroviral therapy: Results from a randomised clinical trial

Antiretroviral therapy (ART) is typically composed of a combination of three antiretroviral drugs and is the treatment of choice for people with human immunodeficiency virus type 1/acquired immune deficiency syndrome (HIV-1/AIDS). However, it is unable to impact on viral reservoirs, which harbour latent HIV-1 genomes that are able to reignite the infection upon treatment suspension. The aim of this study was to provide an estimate of the safety of the disease-modifying antirheumatic agent auranofin and its impact on the HIV-1 reservoir in humans under intensified ART. For this purpose, an interim analysis was conducted of three of the six arms of the NCT02961829 clinical trial (five patients each) with: no intervention, i.e. continuation of first-line ART; intensified ART (ART + dolutegravir and maraviroc); and intensified ART plus auranofin. Auranofin treatment was found to be well tolerated. No major adverse events were detected apart from a transient decrease in CD4⁺ T-cell counts at Weeks 8 and 12. Auranofin decreased total viral DNA in peripheral blood mononuclear cells compared with ART-only regimens at Week 20 (P = 0.036) and induced a decrease in integrated viral DNA as quantified by Alu PCR. Despite the limited number of patient-derived sequences available in this study, phylogenetic analyses of nef sequences support the idea that auranofin may impact on the viral reservoir. [ClinicalTrials.gov ID: NCT02961829].

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

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

Induction of Oxidative Stress Through Inhibition of Thioredoxin Reductase 1 Is an Effective Therapeutic Approach for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most prevalent and lethal cancers worldwide which lacks effective treatment. Cancer cells experience high levels of oxidative stress due to increased generation of reactive oxygen species (ROS). Increased antioxidant-producing capacity is therefore found in cancer cells to counteract oxidative stress. The thioredoxin system is a ubiquitous mammalian antioxidant system which scavenges ROS, and we demonstrate that it is vital for HCC growth as it maintains intracellular reduction-oxidation (redox) homeostasis. Transcriptome sequencing in human HCC samples revealed significant overexpression of thioredoxin reductase 1 (TXNRD1), the cytosolic subunit and key enzyme of the thioredoxin system, with significant correlations to poorer clinicopathological features and patient survival. Driven by the transcriptional activation of nuclear factor (erythroid-derived 2)-like 2, the master protector against oxidative stress, TXNRD1 counteracts intracellular ROS produced in human HCC. Inhibition of TXNRD1 through genetic inhibition hindered the proliferation of HCC cells and induced apoptosis in vitro. Administration of the pharmacological TXNRD1 inhibitor auranofin (AUR) effectively suppressed the growth of HCC tumors induced using the hydrodynamic tail vein injection and orthotopic implantation models in vivo. Furthermore, AUR sensitized HCC cells toward the conventional therapeutic sorafenib. Conclusion: Our study highlights the reliance of HCC cells on antioxidants for redox homeostasis and growth advantage; targeting TXNRD1 resulted in dramatic accumulation of ROS, which was found to be an effective approach for the suppression of HCC tumor growth.

Redirecting an Anticancer to an Antibacterial Hit Against Methicillin-Resistant Staphylococcus aureus

YM155 is a clinically evaluated anticancer with a fused naphthoquinone-imidazolium scaffold. In this study, we demonstrated that based on weak or cryptic antibacterial activity of YM155 against methicillin-resistant Staphylococcus aureus (MRSA) (MIC of 50 μg/ml), some congeneric compounds with short alkyl chains (e.g., c5 with a hexyl chain) at the N3 position of the scaffold, displayed more potent antibacterial activity against MRSA (MIC of 3.13 μg/ml), which is in a clinically achievable range. Their antibacterial activity was evident against Gram-negative bacteria, only in the presence of the outer membrane-permeabilizing agent, polymyxin B. The antibacterial efficacy of c5 was confirmed using the Drosophila systemic infection model. We also characterized five spontaneous c5-resistant MRSA mutants that carry mutations in the ubiE gene, for quinone metabolism and respiratory electron transfer, and subsequently exhibited reduced respiration activity. The antibacterial activity of c5 was compromised either by an antioxidant, N-acetylcysteine, or in an anaerobic condition. These suggest that the antibacterial mechanism of c5 involves the generation of reactive oxygen species (ROS), presumably during respiratory electron transport. This study provides an insight into "drug redirecting," through a chemical modification, based on an ROS-generating pharmacophore.

Drug repurposing screens and synergistic drug-combinations for infectious diseases

Infectious diseases account for nearly one fifth of the worldwide death toll every year. The continuous increase of drug-resistant pathogens is a big challenge for treatment of infectious diseases. In addition, outbreaks of infections and new pathogens are potential threats to public health. Lack of effective treatments for drug-resistant bacteria and recent outbreaks of Ebola and Zika viral infections have become a global public health concern. The number of newly approved antibiotics has decreased significantly in the last two decades compared with previous decades. In parallel with this, is an increase in the number of drug-resistant bacteria. For these threats and challenges to be countered, new strategies and technology platforms are critically needed. Drug repurposing has emerged as an alternative approach for rapid identification of effective therapeutics to treat the infectious diseases. For treatment of severe infections, synergistic drug combinations using approved drugs identified from drug repurposing screens is a useful option which may overcome the problem of weak activity of individual drugs. Collaborative efforts including government, academic researchers and private drug industry can facilitate the translational research to produce more effective new therapeutic agents such as narrow spectrum antibiotics against drug-resistant bacteria for these global challenges.

LINKED ARTICLES

This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

Human Immunodeficiency Virus Playing Hide-and-Seek: Understanding the TFH Cell Reservoir and Proposing Strategies to Overcome the Follicle Sanctuary

Human immunodeficiency virus (HIV) infects millions of people worldwide, and new cases continue to emerge. Once infected, the virus cannot be cleared by the immune system and causes acquired immunodeficiency syndrome. Combination antiretroviral therapeutic regimen effectively suppresses viral replication and halts disease progression. The treatment, however, does not eliminate the virus-infected cells, and interruption of treatment inevitably leads to viral rebound. The rebound virus originates from a group of virus-infected cells referred to as the cellular reservoir of HIV. Identifying and eliminating the HIV reservoir will prevent viral rebound and cure HIV infection. In this review, we focus on a recently discovered HIV reservoir in a subset of CD4⁺ T cells called the follicular helper T (T_FH) cells. We describe the potential mechanisms for the emergence of reservoir in T_FH cells, and the strategies to target and eliminate this viral reservoir.

Host oxidative folding pathways offer novel anti-chikungunya virus drug targets with broad spectrum potential

Alphaviruses require conserved cysteine residues for proper folding and assembly of the E1 and E2 envelope glycoproteins, and likely depend on host protein disulfide isomerase-family enzymes (PDI) to aid in facilitating disulfide bond formation and isomerization in these proteins. Here, we show that in human HEK293 cells, commercially available inhibitors of PDI or modulators thereof (thioredoxin reductase, TRX-R; endoplasmic reticulum oxidoreductin-1, ERO-1) inhibit the replication of CHIKV chikungunya virus (CHIKV) in vitro in a dose-dependent manner. Further, the TRX-R inhibitor auranofin inhibited Venezuelan equine encephalitis virus and the flavivirus Zika virus replication in vitro, while PDI inhibitor 16F16 reduced replication but demonstrated notable toxicity. 16F16 significantly altered the viral genome: plaque-forming unit (PFU) ratio of CHIKV in vitro without affecting relative intracellular viral RNA quantities and inhibited CHIKV E1-induced cell-cell fusion, suggesting that PDI inhibitors alter progeny virion infectivity through altered envelope function. Auranofin also increased the extracellular genome:PFU ratio but decreased the amount of intracellular CHIKV RNA, suggesting an alternative mechanism of action. Finally, auranofin reduced footpad swelling and viremia in the C57BL/6 murine model of CHIKV infection. Our results suggest that targeting oxidative folding pathways represents a potential new anti-alphavirus therapeutic strategy.

Repurposing Approach Identifies Auranofin with Broad Spectrum Antifungal Activity That Targets Mia40-Erv1 Pathway

Current antifungal therapies have limited effectiveness in treating invasive fungal infections. Furthermore, the development of new antifungal is currently unable to keep pace with the urgent demand for safe and effective new drugs. Auranofin, an FDA-approved drug for the treatment of rheumatoid arthritis, inhibits growth of a diverse array of clinical isolates of fungi and represents a new antifungal agent with a previously unexploited mechanism of action. In addition to auranofin's potent antifungal activity against planktonic fungi, this drug significantly reduces the metabolic activity of Candida cells encased in a biofilm. Unbiased chemogenomic profiling, using heterozygous S. cerevisiae deletion strains, combined with growth assays revealed three probable targets for auranofin's antifungal activity—mia40, acn9, and coa4. Mia40 is of particular interest given its essential role in oxidation of cysteine rich proteins imported into the mitochondria. Biochemical analysis confirmed auranofin targets the Mia40-Erv1 pathway as the drug inhibited Mia40 from interacting with its substrate, Cmc1, in a dose-dependent manner similar to the control, MB-7. Furthermore, yeast mitochondria overexpressing Erv1 were shown to exhibit resistance to auranofin as an increase in Cmc1 import was observed compared to wild-type yeast. Further in vivo antifungal activity of auranofin was examined in a Caenorhabditis elegans animal model of Cryptococcus neoformans infection. Auranofin significantly reduced the fungal load in infected C. elegans. Collectively, the present study provides valuable evidence that auranofin has significant promise to be repurposed as a novel antifungal agent and may offer a safe, effective, and quick supplement to current approaches for treating fungal infections.

Galectin-3 promotes caspase-independent cell death of HIV-1-infected macrophages

HIV-1-infected macrophages are a key contributor to the formation of a viral reservoir and new treatment strategies focus on eliminating this pool of virus. Galectin-3 is a potent apoptosis-inducing protein that regulates diverse cellular activities. In the present study, we investigated whether galectin-3 could induce cell death in HIV-1-infected macrophages using HIV-1-infected THP1 monocytes (THP1-MNs) and THP1-derived macrophages (THP1-MΦs) as in vitro cellular models. We found that THP1-MΦs were more resistant than the THP1-MNs to HIV-1 infection-induced death, and that HIV-1 infection of the THP1-MΦs increased expression of the anti-apoptotic proteins Mcl-1, Bcl-2 and Bcl-xL. Additionally, galectin-3 but not FasL, tumor necrosis factor (TNF)-related apoptosis-inducing ligand or TNF-α, could induce cell death in HIV-1-infected THP1-MΦs. A similar result was shown for primary human monocyte-derived macrophages. Galectin-3-induced cell death was also significantly increased in macrophages obtained from SIVmac251-infected macaques compared to that of macrophages from healthy macaques. Furthermore, galectin-3-induced cell death in HIV-1-infected THP1-MΦs was caspase independent. Interestingly, endonuclease G (Endo G) was increased in the nucleus and decreased in the cytoplasm of galectin-3-treated cells; thus, galectin-3-induced cell death in HIV-1-infected THP1-MΦs is most likely related to the translocation of Endo G from the cytoplasm to the nucleus. These findings suggest that galectin-3 may potentially aid in the eradication of HIV-1/SIV-infected macrophages.

Oxidative Stress during HIV Infection: Mechanisms and Consequences

It is generally acknowledged that reactive oxygen species (ROS) play crucial roles in a variety of natural processes in cells. If increased to levels which cannot be neutralized by the defense mechanisms, they damage biological molecules, alter their functions, and also act as signaling molecules thus generating a spectrum of pathologies. In this review, we summarize current data on oxidative stress markers associated with human immunodeficiency virus type-1 (HIV-1) infection, analyze mechanisms by which this virus triggers massive ROS production, and describe the status of various defense mechanisms of the infected host cell. In addition, we have scrutinized scarce data on the effect of ROS on HIV-1 replication. Finally, we present current state of knowledge on the redox alterations as crucial factors of HIV-1 pathogenicity, such as neurotoxicity and dementia, exhaustion of CD4+/CD8+ T-cells, predisposition to lung infections, and certain side effects of the antiretroviral therapy, and compare them to the pathologies associated with the nitrosative stress.

Current views on HIV-1 latency, persistence, and cure

HIV-1 infection cannot be cured as it persists in latently infected cells that are targeted neither by the immune system nor by available therapeutic approaches. Consequently, a lifelong therapy suppressing only the actively replicating virus is necessary. The latent reservoir has been defined and characterized in various experimental models and in human patients, allowing research and development of approaches targeting individual steps critical for HIV-1 latency establishment, maintenance, and reactivation. However, additional mechanisms and processes driving the remaining low-level HIV-1 replication in the presence of the suppressive therapy still remain to be identified and targeted. Current approaches toward HIV-1 cure involve namely attempts to reactivate and purge HIV latently infected cells (so-called "shock and kill" strategy), as well as approaches involving gene therapy and/or gene editing and stem cell transplantation aiming at generation of cells resistant to HIV-1. This review summarizes current views and concepts underlying different approaches aiming at functional or sterilizing cure of HIV-1 infection.

Human CD4+ T cells require exogenous cystine for glutathione and DNA synthesis

Adaptive immune responses require activation and expansion of antigen-specific T cells. Whereas early T cell activation is independent of exogenous cystine (Cys2), T cell proliferation is dependent of Cys2. However, the exact roles of Cys2 in T cell proliferation still need to be determined. The aim of this study was to elucidate why activated human T cells require exogenous Cys2 in order to proliferate. We activated purified naïve human CD4+ T cells and found that glutathione (GSH) levels and DNA synthesis were dependent on Cys2 and increased in parallel with increasing concentrations of Cys2. Vice-versa, the GSH synthesis inhibitor L-buthionine-sulfoximine (BSO) and inhibition of Cys2 uptake with glutamate inhibited GSH and DNA synthesis in parallel. We further found that thioredoxin (Trx) can partly substitute for GSH during DNA synthesis. Finally, we show that GSH or Trx is required for the activity of ribonucleotide reductase (RNR), the enzyme responsible for generation of the deoxyribonucleotide DNA building blocks. In conclusion, we show that activated human T cells require exogenous Cys2 to proliferate and that this is partly explained by the fact that Cys2 is required for production of GSH, which in turn is required for optimal RNR-mediated deoxyribonucleotide synthesis and DNA replication.

Dual targeting of the thioredoxin and glutathione systems in cancer and HIV

Although the use of antioxidants for the treatment of cancer and HIV/AIDS has been proposed for decades, new insights gained from redox research have suggested a very different scenario. These new data show that the major cellular antioxidant systems, the thioredoxin (Trx) and glutathione (GSH) systems, actually promote cancer growth and HIV infection, while suppressing an effective immune response. Mechanistically, these systems control both the redox- and NO-based pathways (nitroso-redox homeostasis), which subserve innate and cellular immune defenses. Dual inhibition of the Trx and GSH systems synergistically kills neoplastic cells in vitro and in mice and decreases resistance to anticancer therapy. Similarly, the population of HIV reservoir cells that constitutes the major barrier to a cure for AIDS is exquisitely redox sensitive and could be selectively targeted by Trx and GSH inhibitors. Trx and GSH inhibition may lead to a reprogramming of the immune response, tilting the balance between the immune system and cancer or HIV in favor of the former, allowing elimination of diseased cells. Thus, therapies based on silencing of the Trx and GSH pathways represent a promising approach for the cure of both cancer and AIDS and warrant further investigation.

Elevation and persistence of CD8 T-cells in HIV infection: the Achilles heel in the ART era

Introduction

HIV infection leads to a disturbed T-cell homeostasis, featured by a depletion of CD4 T-cells and a persistent elevation of CD8 T-cells over disease progression. Most effort of managing HIV infection has been focused on CD4 T-cell recovery, while changes in the CD8 compartment were relatively underappreciated in the past.

Methods

A comprehensive literature review of publications in English language was conducted using major electronic databases. Our search was focused on factors contributing to CD8 T-cell dynamics in HIV infection and following antiretroviral therapy (ART).

Discussion

Normalization of CD8 counts is seldom observed even with optimal CD4 recovery following long-term treatment. Initiation of ART in primary HIV infection leads to enhanced normalization of CD8 count compared with long-term ART initiated in chronic infection. Importantly, such CD8 elevation in treated HIV infection is associated with an increased risk of inflammatory non-AIDS-related clinical events independent of CD4 T-cell recovery. The mechanisms underlying CD8 persistence remain largely unknown, which may include bystander activation, exhaustion and immunosenescence of CD8 T-cells. The information provided herein will lead to a better understanding of factors associated with CD8 persistence and contribute to the development of strategies aiming at CD8 normalization.

Conclusions

Persistence of CD8 T-cell elevation in treated HIV-infected patients is associated with an increased risk of non-AIDS-related events. Now that advances in ART have led to decreased AIDS-related opportunistic diseases, more attention has been focused on reducing non-AIDS events and normalizing persistent CD8 T-cell elevation.

Auranofin: repurposing an old drug for a golden new age

Drug discovery, development and registration is an expensive and time-consuming process associated with a high failure rate [Pessetto et al. (Mol Cancer Ther 12:1299-1309, 2013), Woodcock and Woosley (Annu Rev Med 59:1-12, 2008)]. Drug 'repurposing' is the identification of new therapeutic purposes for already approved drugs and is more affordable and achievable than novel drug discovery [Pessetto et al. (Mol Cancer Ther 12:1299-1309, 2013)]. Auranofin is a drug that is approved for the treatment of rheumatoid arthritis but is being investigated for potential therapeutic application in a number of other diseases including cancer, neurodegenerative disorders, HIV/AIDS, parasitic infections and bacterial infections [Tejman-Yarden et al. (Antimicrob Agents Chemother 57:2029-2035, 2013)]. The main mechanism of action of auranofin is through the inhibition of reduction/oxidation (redox) enzymes that are essential for maintaining intracellular levels of reactive oxygen species. Inhibition of these enzymes leads to cellular oxidative stress and intrinsic apoptosis [Pessetto et al. (Mol Cancer Ther 12:1299-1309, 2013), Fan et al. (Cell Death Dis 5:e1191, 2014), Fiskus et al. (Cancer Res 74:2520-2532, 2014), Marzano et al. (Free Radic Biol Med 42:872-881, 2007)]. Drugs such as auranofin that have already been approved for human use [Tejman-Yarden et al. (Antimicrob Agents Chemother 57:2029-2035, 2013)] can be brought into clinical use for other diseases relatively quickly and for a fraction of the cost of new drugs.

CCR5 Targeted Cell Therapy for HIV and Prevention of Viral Escape

Allogeneic transplantation with CCR5-delta 32 (CCR5-d32) homozygous stem cells in an HIV infected individual in 2008, led to a sustained virus control and probably eradication of HIV. Since then there has been a high degree of interest to translate this approach to a wider population. There are two cellular ways to do this. The first one is to use a CCR5 negative cell source e.g., hematopoietic stem cells (HSC) to copy the initial finding. However, a recent case of a second allogeneic transplantation with CCR5-d32 homozygous stem cells suffered from viral escape of CXCR4 quasi-species. The second way is to knock down CCR5 expression by gene therapy. Currently, there are five promising techniques, three of which are presently being tested clinically. These techniques include zinc finger nucleases (ZFN), clustered regularly interspaced palindromic repeats/CRISPR-associated protein 9 nuclease (CRISPR/Cas9), transcription activator-like effectors nuclease (TALEN), short hairpin RNA (shRNA), and a ribozyme. While there are multiple gene therapy strategies being tested, in this review we reflect on our current knowledge of inhibition of CCR5 specifically and whether this approach allows for consequent viral escape.

Increased ex vivo cell death of central memory CD4 T cells in treated HIV infected individuals with unsatisfactory immune recovery

Background

High levels of ex vivo CD4 T-cell death and the accumulation of highly differentiated and/or immunosenescent T cells have been associated with poor CD4 T-cell recovery in treated HIV-infected individuals. However, the relationship between cell death and T-cell differentiation is still unclear.

Methods

We have analyzed cell death, immunosenescence and differentiation parameters in HAART-treated subjects (VL <50 copies/mL for more than 2 years) with CD4 T-cell count <350 cells/μL (immunodiscordant, n = 23) or >400 cells/μL (immunoconcordant, n = 33). We included 11 healthy individuals as reference.

Results

As expected, suboptimal CD4 T-cell recovery was associated with low frequencies of naïve cells, high frequencies of transitional and effector memory cells and a subsequent low ratio of central/transitional memory cells in the CD4 compartment. These alterations correlated with spontaneous CD4 T-cell death. A deeper analysis of cell death in CD4 T-cell subsets showed increased cell death in memory cells of immunodiscordant individuals, mainly affecting central memory cells. Immunosenescence was also higher in immunodiscordant individuals albeit unrelated to cell death. The CD8 compartment was similar in both HIV-infected groups, except for an underrepresentation of naïve cells in immunodiscordant individuals.

Conclusion

Immunodiscordant individuals show alterations in memory CD4 T-cell differentiation associated with a short ex vivo lifespan of central memory cells and an in vivo low central/transitional memory cell ratio. These alterations may contribute to poor CD4 T-cell repopulation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0601-2) contains supplementary material, which is available to authorized users.

The role of cellular oxidoreductases in viral entry and virus infection-associated oxidative stress: potential therapeutic applications

INTRODUCTION

Cellular oxidoreductases catalyze thiol/disulfide exchange reactions in susceptible proteins and contribute to the cellular defense against oxidative stress. Oxidoreductases and oxidative stress are also involved in viral infections. In this overview, different aspects of the role of cellular oxidoreductases and oxidative stress during viral infections are discussed from a chemotherapeutic viewpoint.

AREAS COVERED

Entry of enveloped viruses into their target cells is triggered by the interaction of viral envelope glycoproteins with cellular (co)receptor(s) and depends on obligatory conformational changes in these viral envelope glycoproteins and/or cellular receptors. For some viruses, these conformational changes are mediated by cell surface-associated cellular oxidoreductases, which mediate disulfide bridge reductions in viral envelope glycoprotein(s). Therefore, targeting these oxidoreductases using oxidoreductase inhibitors might yield an interesting strategy to block viral entry of these viruses. Furthermore, since viral infections are often associated with systemic oxidative stress, contributing to disease progression, the enhancement of the cellular antioxidant defense systems might have potential as an adjuvant antiviral strategy, slowing down disease progression.

EXPERT OPINION

Promising antiviral data were obtained for both strategies. However, potential pitfalls have also been identified for these strategies, indicating that it is important to carefully assess the benefits versus risks of these antiviral strategies.

Chloroquine and beyond: exploring anti-rheumatic drugs to reduce immune hyperactivation in HIV/AIDS

The restoration of the immune system prompted by antiretroviral therapy (ART) has allowed drastically reducing the mortality and morbidity of HIV infection. However, one main source of clinical concern is the persistence of immune hyperactivation in individuals under ART. Chronically enhanced levels of T-cell activation are associated with several deleterious effects which lead to faster disease progression and slower CD4⁺ T-cell recovery during ART. In this article, we discuss the rationale, and review the results, of the use of antimalarial quinolines, such as chloroquine and its derivative hydroxychloroquine, to counteract immune activation in HIV infection. Despite the promising results of several pilot trials, the most recent clinical data indicate that antimalarial quinolines are unlikely to exert a marked beneficial effect on immune activation. Alternative approaches will likely be required to reproducibly decrease immune activation in the setting of HIV infection. If the quinoline-based strategies should nevertheless be pursued in future studies, particular care must be devoted to the dosage selection, in order to maximize the chances to obtain effective in vivo drug concentrations.

Cell-mediated anti-Gag immunity in pharmacologically induced functional cure of simian AIDS: a 'bottleneck effect'?

BACKGROUND

Administration of antiretroviral therapy and two experimental drugs, auranofin and buthionine sulfoximine (BSO), was previously shown to be followed by drug-free control of chronic SIVmac251 infection, decreased immune activation and increased cell-mediated anti-Gag responses.

METHODS

Phylogeny was analysed with Phylogeny.fr. Entropy was calculated with the specific tool of the HIV Sequence Database. The capsid Gag structure was computed using SPDBV. The bottleneck effect was simulated through an appropriate online tool.

RESULTS

The region of Gag predominantly targeted during control of SIVmac251 infection is highly conserved in primate lentiviruses and plays an important role in capsid architecture. Computer-aided simulations support the view that the preferential development of immune responses against this region is derived from a 'bottleneck effect' after restriction, by auranofin and BSO, of the activated lymphocyte pool.

CONCLUSIONS

Restriction of immune activation through auranofin/BSO may result in stochastic selection of cell clones targeting conserved epitopes leading to a functional cure-like condition.

Two-Year Follow-Up of Macaques Developing Intermittent Control of the Human Immunodeficiency Virus Homolog Simian Immunodeficiency Virus SIVmac251 in the Chronic Phase of Infection

Off-therapy control of viremia by HIV-infected individuals has been associated with two likely players: a restricted viral reservoir and an efficient cell-mediated immune response. We previously showed that a combination of highly suppressive antiretroviral therapy and two experimental drugs, i.e., auranofin and buthionine sulfoximine, was able to reduce the viral reservoir, elicit efficient cell-mediated antiviral responses, and induce intermittent posttherapy viral load control in chronically SIVmac251-infected macaques. We here show that the macaques that had received this drug combination and then stopped antiretroviral therapy were also able to maintain low numbers of activated CD4+ T cells at viral rebound. Moreover, these macaques consistently displayed low-level simian immunodeficiency virus (SIV) diversity, which was in line with the strong and broadly reactive cell-mediated immune responses against conserved Gag antigens. Extended follow-up showed that the two macaques that had received the complete drug combination remained healthy and did not develop AIDS in 2 years of follow-up after therapy suspension. This disease-free survival is longer than twice the average time of progression to AIDS in SIVmac251-infected rhesus macaques. These results suggest that limited numbers of activated T cells at viral rebound and subsequent development of broadly reactive cell-mediated responses may be interrelated in reducing the viral reservoir.

IMPORTANCE

The HIV reservoir in CD4+ T cells represents one main obstacle to HIV eradication. Recent studies, however, show that a drastic reduction of this reservoir is insufficient for inducing a functional cure of AIDS. In the present work, we thoroughly studied and subjected to long-term follow-up two macaques showing intermittent control of the virus following suspension of antiretroviral therapy plus an experimental antireservoir treatment, i.e., the gold salt auranofin and the investigational chemotherapeutic agent buthionione sulfoximine (BSO). We found that these drugs were able to decrease the number of activated CD4+ T cells, which are preferential targets for HIV infection. Then, efficient immune responses against the virus were developed in the macaques, which remained healthy during 2 years of follow-up. This result may furnish another building block for future attempts to cure HIV/AIDS.