Chloroquine modulates HIV-1-induced plasmacytoid dendritic cell alpha interferon: implication for T-cell activation

IRF7: role and regulation in immunity and autoimmunity

Interferon regulatory factor (IRF) 7 was originally identified as master transcriptional factor that produced IFN-I and regulated innate immune response, subsequent studies have revealed that IRF7 performs a multifaceted and versatile functions in multiple biological processes. In this review, we provide a comprehensive overview on the current knowledge of the role of IRF7 in immunity and autoimmunity. We focus on the latest regulatory mechanisms of IRF7 in IFN-I, including signaling pathways, transcription, translation, and post-translational levels, the dimerization and nuclear translocation, and the role of IRF7 in IFN-III and COVID-19. In addition to antiviral immunity, we also discuss the role and mechanism of IRF7 in autoimmunity, and the further research will expand our understanding of IRF7.

COVID-19 pandemic: A multidisciplinary perspective on the pathogenesis of a novel coronavirus from infection, immunity and pathological responses

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus2 (SARS-CoV-2), has spread to more than 200 countries and regions, having a huge impact on human health, hygiene, and economic activities. The epidemiological and clinical phenotypes of COVID-19 have increased since the onset of the epidemic era, and studies into its pathogenic mechanisms have played an essential role in clinical treatment, drug development, and prognosis prevention. This paper reviews the research progress on the pathogenesis of the novel coronavirus (SARS-CoV-2), focusing on the pathogenic characteristics, loci of action, and pathogenic mechanisms leading to immune response malfunction of SARS-CoV-2, as well as summarizing the pathological damage and pathological manifestations it causes. This will update researchers on the latest SARS-CoV-2 research and provide directions for future therapeutic drug development.

SIDT1 plays a key role in type I IFN responses to nucleic acids in plasmacytoid dendritic cells and mediates the pathogenesis of an imiquimod-induced psoriasis model

Background

Type I IFN (IFN-I) is a family of cytokines involved in the pathogenesis of autoimmune and autoinflammatory diseases such as psoriasis. SIDT1 is an ER-resident protein expressed in the lymphoid lineage, and involved in anti-viral IFN-I responses in vivo, through an unclear mechanism. Herein we have dissected the role of SIDT1 in the natural IFN-producing cells, the plasmacytoid dendritic cells (pDC).

Methods

The function of SIDT1 in pDC was determined by silencing its expression in human primary pDC and GEN2.2 cell line. SIDT1 role in vivo was assessed using the imiquimod-induced psoriasis model in the SIDT1-deficient mice (sidt1^−/−).

Findings

Silencing of SIDT1 in GEN2.2 led to a blockade of the IFN-I response after stimulation of TLR7 and TLR9, without affecting the pro-inflammatory responses or upregulation of maturation markers. We found that SIDT1 migrates from the ER to the endosomal and lysosomal compartments together with TLR9 after CpG stimulation, participating in the access of the TLR9-CpG complex to lysosome-related vesicles, and therefore mediating the activation of TBK1 and the nuclear migration of IRF7, but not of NF-κB. sidt1^−/− mice showed a significant decrease in severity parameters of the imiquimod-induced acute psoriasis-like model, associated with a decrease in the production of IFN-I and IFN-dependent chemokines.

Interpretation

Our findings indicate that SIDT1 is at the cross-road between the IFN-I and the proinflammatory pathways and constitutes a promising drug target for psoriasis and other diseases mediated by IFN-I responses.

Funding

This work was supported by the Consejería de Salud y Familias de la Junta de Andalucía (PIER_S1149 and C2_S0050) and Instituto de Salud Carlos III (PI18/00082 and PI21/01151), partly supported by European FEDER funds, and prior funding to MEAR from the Alliance for Lupus Research and the Swedish Research Council.

Targeted Delivery of Chloroquine to Antigen-Presenting Cells Enhances Inhibition of the Type I Interferon Response

Systemic lupus erythematosus (SLE) causes damaging inflammation in multiple organs via the accumulation of immune complexes. These complexes activate plasmacytoid dendritic cells (pDCs) via toll-like receptors (TLRs), contributing to disease pathogenesis by driving the secretion of inflammatory type I interferons (IFNs). Antimalarial drugs, such as chloroquine (CQ), are TLR antagonists used to alleviate inflammation in SLE. However, they require ∼3 months of continuous use before achieving therapeutic efficacy and can accumulate in the retinal pigment epithelium with chronic use, resulting in retinopathy. We hypothesized that poly(ethylene glycol)-b-poly(propylene sulfide) filamentous nanocarriers, filomicelles (FMs), could directly deliver CQ to pDCs via passive, morphology-based targeting to concentrate drug delivery to specific immune cells, improve drug activity by increased inhibition of type I IFN, and enhance efficacy per dose. Healthy human peripheral blood mononuclear cells were treated with soluble CQ or CQ-loaded FMs, stimulated with TLR agonists or SLE patient sera, and type I IFN secretion was quantified via multi-subtype IFN-α ELISA and MX1 gene expression using real-time reverse transcription-quantitative polymerase chain reaction. Our results showed that 50 μg CQ/mg FM decreased MX1 expression and IFN-α production after TLR activation with either synthetic nucleic acid agonists or immune complex-rich sera from SLE patients. Cellular uptake and biodistribution studies showed that FMs preferentially accumulate in human pDCs and monocytes in vitro and in tissues frequently damaged in SLE patients (i.e., kidneys), while sparing the eye in vivo. These results showed that nanocarrier morphology enables drug delivery, and CQ-FMs may be equally effective and more targeted than soluble CQ at inhibiting SLE-relevant pathways.

Inhibition of Chikungunya Virus Infection by 4-Hydroxy-1-Methyl-3-(3-morpholinopropanoyl)quinoline-2(1H)-one (QVIR) Targeting nsP2 and E2 Proteins

The re-emergence of Chikungunya virus (CHIKV) infection in humans with no approved antiviral therapies or vaccines is one of the major problems with global significance. In the present investigation, we screened 80 in-house quinoline derivatives for their anti-CHIKV activity by computational techniques and found 4-hydroxy-1-methyl-3-(3-morpholinopropanoyl)quinoline-2(1H)-one (QVIR) to have potential binding affinities with CHIKV nsP2 and E2 glycoproteins. QVIR was evaluated in vitro for its anti-CHIKV potential. QVIR showed strong inhibition of CHIKV infection with an EC₅₀ (50% effective concentration) value of 2.2 ± 0.49 μM without significant cytotoxicity (CC₅₀ > 200 μM) and was chosen for further elucidation of its antiviral mechanism. The infectious viral particle formation was abolished by approximately 72% at a QVIR concentration of 20 μM during infection in the BHK-21 cell line, and the CHIKV RNA synthesis was diminished by 84% for nsP2 as well as 74% for E2, whereas the levels of viral proteins were decreased by 69.9% for nsP2 and 53.9% for E2. Flow cytometry analysis confirmed a huge decline in the expression of viral nsP2 and E2 proteins by 71.84 and 67.7%, respectively. Time of addition experiments indicated that QVIR inhibited viral infection at early and late stages of viral replication cycle, and the optimal inhibition was observed at 16 h post infection. The present study advocates for the first time that QVIR acts as a substantial and potent inhibitor against CHIKV and might be as an auspicious novel drug candidate for the development of therapeutic agents against CHIKV infections.

Repurposing Chloroquine Against Multiple Diseases With Special Attention to SARS-CoV-2 and Associated Toxicity

Chloroquine and its derivatives have been used since ages to treat malaria and have also been approved by the FDA to treat autoimmune diseases. The drug employs pH-dependent inhibition of functioning and signalling of the endosome, lysosome and trans-Golgi network, immunomodulatory actions, inhibition of autophagy and interference with receptor binding to treat cancer and many viral diseases. The ongoing pandemic of COVID-19 has brought the whole world on the knees, seeking an urgent hunt for an anti-SARS-CoV-2 drug. Chloroquine has shown to inhibit receptor binding of the viral particles, interferes with their replication and inhibits "cytokine storm". Though multiple modes of actions have been employed by chloroquine against multiple diseases, viral diseases can provide an added advantage to establish the anti-SARS-CoV-2 mechanism, the in vitro and in vivo trials against SARS-CoV-2 have yielded mixed results. The toxicological effects and dosage optimization of chloroquine have been studied for many diseases, though it needs a proper evaluation again as chloroquine is also associated with several toxicities. Moreover, the drug is inexpensive and is readily available in many countries. Though much of the hope has been created by chloroquine and its derivatives against multiple diseases, repurposing it against SARS-CoV-2 requires large scale, collaborative, randomized and unbiased clinical trials to avoid false promises. This review summarizes the use and the mechanism of chloroquine against multiple diseases, its side-effects, mechanisms and the different clinical trials ongoing against "COVID-19".

4-Aminoquinoline compounds from the Spanish flu to COVID-19

In 1918, quinine was used as one of the unscientifically based treatments against the H1N1 virus during the Spanish flu pandemic. Originally, quinine was extracted from the bark of Chinchona trees by South American natives of the Amazon forest, and it has been used to treat fever since the seventeenth century. The recent COVID-19 pandemic caused by Sars-Cov-2 infection has forced researchers to search for ways to prevent and treat this disease. Based on the antiviral potential of two 4-aminoquinoline compounds derived from quinine, known as chloroquine (CQ) and hydroxychloroquine (HCQ), clinical investigations for treating COVID-19 are being conducted worldwide. However, there are some discrepancies among the clinical trial outcomes.Thus, even after one hundred years of quinine use during the Spanish flu pandemic, the antiviral properties promoted by 4-aminoquinoline compounds remain unclear. The underlying molecular mechanisms by which CQ and HCQ inhibit viral replication open up the possibility of developing novel analogs of these drugs to combat COVID-19 and other viruses.

Prevention and treatment of COVID-19: Focus on interferons, chloroquine/hydroxychloroquine, azithromycin, and vaccine

The ongoing pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has drawn the attention of researchers and clinicians from several disciplines and sectors who are trying to find durable solutions both at preventive and treatment levels. To date, there is no approved effective treatment or vaccine available to control the coronavirus disease-2019 (COVID-19). The preliminary in vitro studies on viral infection models showed potential antiviral activities of type I and III interferons (IFNs), chloroquine (CQ)/hydroxychloroquine (HCQ), and azithromycin (AZM); however, the clinical studies on COVID-19 patients treated with CQ/HCQ and AZM led to controversies in different regions due to their adverse side effects, as well as their combined treatment could prolong the QT interval. Interestingly, the treatment with type I IFNs showed encouraging results. Moreover, the different preliminary reports of COVID-19 candidate vaccines showcase promising results by inducing the production of a high level of neutralizing antibodies (NAbs) and specific T cell-mediated immune response in almost all participants. The present review aims to summarize and analyze the recent progress evidence concerning the use of IFNs, CQ/HCQ, and AZM for the treatment of COVID-19. The available data on immunization options to prevent the COVID-19 are also analyzed with the aim to present the promising options which could be investigated in future for sustainable control of the pandemic.

Elucidating the Pivotal Immunomodulatory and Anti-Inflammatory Potentials of Chloroquine and Hydroxychloroquine

Chloroquine (CQ) and hydroxychloroquine (HCQ) are derivatives of 4-aminoquinoline compounds with over 60 years of safe clinical usage. CQ and HCQ are able to inhibit the production of cytokines such as interleukin- (IL-) 1, IL-2, IL-6, IL-17, and IL-22. Also, CQ and HCQ inhibit the production of interferon- (IFN-) α and IFN-γ and/or tumor necrotizing factor- (TNF-) α. Furthermore, CQ blocks the production of prostaglandins (PGs) in the intact cell by inhibiting substrate accessibility of arachidonic acid necessary for the production of PGs. Moreover, CQ affects the stability between T-helper cell (Th) 1 and Th2 cytokine secretion by augmenting IL-10 production in peripheral blood mononuclear cells (PBMCs). Additionally, CQ is capable of blocking lipopolysaccharide- (LPS-) triggered stimulation of extracellular signal-modulated extracellular signal-regulated kinases 1/2 in human PBMCs. HCQ at clinical levels effectively blocks CpG-triggered class-switched memory B-cells from differentiating into plasmablasts as well as producing IgG. Also, HCQ inhibits cytokine generation from all the B-cell subsets. IgM memory B-cells exhibits the utmost cytokine production. Nevertheless, CQ triggers the production of reactive oxygen species. A rare, but serious, side effect of CQ or HCQ in nondiabetic patients is hypoglycaemia. Thus, in critically ill patients, CQ and HCQ are most likely to deplete all the energy stores of the body leaving the patient very weak and sicker. We advocate that, during clinical usage of CQ and HCQ in critically ill patients, it is very essential to strengthen the CQ or HCQ with glucose infusion. CQ and HCQ are thus potential inhibitors of the COVID-19 cytokine storm.

A randomized trial of vorinostat with treatment interruption after initiating antiretroviral therapy during acute HIV-1 infection

OBJECTIVE AND DESIGN

A randomized, open-label pilot study in individuals treated with antiretroviral therapy (ART) since acute HIV infection (AHI) with a regimen including a histone deacetylase inhibitor to induce HIV from latency and control HIV replication during subsequent treatment interruption (TI).

METHODS

Fifteen participants who initiated ART at AHI were randomized to vorinostat/hydroxychloroquine/maraviroc (VHM) plus ART (n ​= ​10) or ART alone (n ​= ​5). The VHM arm received three 14-day vorinostat cycles within 10 weeks before TI. ART was resumed for plasma viral load (VL) ​> ​1,000 HIV RNA copies/mL. Primary outcome was proportion of participants on VHM ​+ ​ART versus ART only with VL ​< ​50 copies/mL for 24 weeks after TI.

RESULTS

Fifteen participants on ART (median: 178 weeks: range 79-295) enrolled. Two on VHM ​+ ​ART experienced serious adverse events. Fourteen participants underwent TI; all experienced VL rebound with no difference in time between arms: VHM ​+ ​ART (n ​= ​9) median: 4 weeks and ART only (n ​= ​5) median: 5 weeks. VHM induced a 2.2-fold increase in VL (p ​= ​0.008) by single-copy HIV RNA assay after the first cycle. Neopterin levels increased significantly following the first two cycles. After VHM treatment, the frequencies of peripheral blood mononuclear cells harboring total HIV DNA and cell-associated RNA were unchanged. All participants achieved VL suppression following ART re-initiation.

CONCLUSIONS

Administration of VHM increased HIV VL in plasma, but this was not sustained. VHM did not impact time to viral rebound following TI and had no impact on the size of the HIV reservoir, suggesting that HIV reservoir elimination will require alternative treatment strategies.

Immune Modulation as a Therapeutic Option During the SARS-CoV-2 Outbreak: The Case for Antimalarial Aminoquinolines

The rapid spread, severity, and lack of specific treatment for COVID-19 resulted in hasty drug repurposing. Conceptually, trials of antivirals were well-accepted, but twentieth century antimalarials sparked an impassioned global debate. Notwithstanding, antiviral and immunomodulatory effects of aminoquinolines have been investigated in vitro, in vivo and in clinical trials for more than 30 years. We review the mechanisms of action of (hydroxy)chloroquine on immune cells and networks and discuss promises and pitfalls in the fight against SARS-CoV-2, the agent of the COVID-19 outbreak.

Chloroquine in fighting COVID-19: good, bad, or both?

Coronavirus disease 2019 (COVID-19) has attracted worldwide attention due to its speed of progression and elevated mortality rate. Amid the rush to develop treatments, recent hopes have focused on the anti-malarial drug chloroquine or the derivative hydroxychloroquine. Here, we briefly discuss the evidence for the potential use of these drugs with regard to the current pandemic.

Immunomodulatory Effects of Hydroxychloroquine and Chloroquine in Viral Infections and Their Potential Application in Retinal Gene Therapy

Effective treatment of retinal diseases with adeno-associated virus (AAV)-mediated gene therapy is highly dependent on the proportion of successfully transduced cells. However, due to inflammatory reactions at high vector doses, adjunctive treatment may be necessary to enhance the therapeutic outcome. Hydroxychloroquine and chloroquine are anti-malarial drugs that have been successfully used in the treatment of autoimmune diseases. Evidence suggests that at high concentrations, hydroxychloroquine and chloroquine can impact viral infection and replication by increasing endosomal and lysosomal pH. This effect has led to investigations into the potential benefits of these drugs in the treatment of viral infections, including human immunodeficiency virus and severe acute respiratory syndrome coronavirus-2. However, at lower concentrations, hydroxychloroquine and chloroquine appear to exert immunomodulatory effects by inhibiting nucleic acid sensors, including toll-like receptor 9 and cyclic GMP-AMP synthase. This dose-dependent effect on their mechanism of action supports observations of increased viral infections associated with lower drug doses. In this review, we explore the immunomodulatory activity of hydroxychloroquine and chloroquine, their impact on viral infections, and their potential to improve the efficacy and safety of retinal gene therapy by reducing AAV-induced immune responses. The safety and practicalities of delivering hydroxychloroquine into the retina will also be discussed.

Repurposing of well-known medications as antivirals: hydroxychloroquine and chloroquine - from HIV-1 infection to COVID-19

INTRODUCTION

Chloroquine (CQ) and hydroxychloroquine (HCQ) originally were prescribed for prevention or treatment of malaria, but now successfully are used in several rheumatologic diseases. In addition, in recent decades considering their immunomodulatory effects, high tolerably, and low cost, they are evaluated for various viral infections from HIV to COVID-19.

AREAS COVERED

In this review, we tried to summarize all available studies on HCQ and CQ efficacy for management of viral infections and the probable mechanisms of action. The data were collected by searching 'Hydroxychloroquine,' 'Chloroquine,' 'Viral infection,' and names of various viral infections in PubMed/MEDLINE, Scopus, and Google Scholar databases from commencement to June 2020. Out of 95 search results, 74 most relevant works were gathered.

EXPERT OPINION

HCQ/CQ showed acceptable efficacy in HIV especially as an adjuvant treatment beside routine HAART. However, for some viral infections such as ZIKA, EBOLA, SARS-CoV, and MERS-CoV, human studies are lacking. In the COVID-19 pandemic, in vitro and preliminary human studies showed encouraging findings. However, later well-designed trials and retrospective studies with large sample size not only reported non-significant efficacy but also showed more cardiac adverse reactions. Alkalinization of acid vesicles is the most important mechanism of action.

Facts and Myths: Efficacies of Repurposing Chloroquine and Hydroxychloroquine for the Treatment of COVID-19

The emergence of coronavirus disease 2019 (COVID-19) is caused by the 2019 novel coronavirus (2019-nCoV). The 2019-nCoV first broke out in Wuhan and subsequently spread worldwide owing to its extreme transmission efficiency. The fact that the COVID-19 cases and mortalities are reported globally and the WHO has declared this outbreak as the pandemic, the international health authorities have focused on rapid diagnosis and isolation of patients as well as search for therapies able to counter the disease severity. Due to the lack of known specific, effective and proven therapies as well as the situation of public-health emergency, drug repurposing appears to be the best armour to find a therapeutic solution against 2019-nCoV infection. Repurposing anti-malarial drugs and chloroquine (CQ)/ hydroxychloroquine (HCQ) have shown efficacy to inhibit most coronaviruses, including SARS-CoV-1 coronavirus. These CQ analogues have shown potential efficacy to inhibit 2019-nCoV in vitro that leads to focus several future clinical trials. This review discusses the possible effective roles and mechanisms of CQ analogues for interfering with the 2019-nCoV replication cycle and infection.

A review on possible modes of action of chloroquine/hydroxychloroquine: repurposing against SAR-CoV-2 (COVID-19) pandemic

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Chloroquine (CQ) has diverse modes of action against viral infections.

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CQ may interfere with SARS-CoV-2 attachment to the host ACE2 receptor.

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CQ may hamper the STING pathway to attenuate the pro-inflammatory response.

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Hydroxychloroquine (HCQ) might be a logical approach in the treatment of SARS-CoV-2 infection.

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Large clinical trials are needed before clinical recommendations of HCQ against COVID-19.

Chloroquine (CQ) and its analogue hydroxychloroquine (HCQ) have long been used worldwide as frontline drugs for the treatment and prophylaxis of human malaria. Since the first reported cases in Wuhan, China, in late December 2019, humans have been under threat from coronavirus disease 2019 (COVID-19) caused by the novel coronavirus SARS-CoV-2 (previously known as 2019-nCoV), subsequently declared a pandemic. While the world is searching for expedited approval for a vaccine, which may be only preventative and not a cure, physicians and country leaders are considering several concerted clinical trials suggesting that the age-old antimalarial drugs CQ/HCQ could be a potent therapeutic against COVID-19. Based on accumulating scientific reports, here we highlight the possible modes of action of CQ/HCQ that could justify its use against viral infections. Considering the global health crisis of the COVID-19 pandemic, the option of repurposing old drugs, e.g. CQ/HCQ, particularly HCQ, for the treatment of SARS-CoV-2 infection could be a good choice. CQ/HCQ has diverse modes of action, including alteration of the acidic environment inside lysosomes and late endosomes, preventing endocytosis, exosome release and phagolysosomal fusion, and inhibition of the host cytokine storm. One or more diverse mechanisms might work against viral infections and reduce mortality. As there is no cure for COVID-19, clinical testing of HCQ is urgently required to determine its potency against SARS-CoV-2, as this is the currently available treatment option. There remains a need to find other innovative drug candidates as possible candidates to enter clinical evaluation and testing.

HIV-1 Tat - TLR4/MD2 interaction drives the expression of IDO-1 in monocytes derived dendritic cells through NF-κB dependent pathway

In the present study we showed that HIV-1 Tat protein stimulated the expression of Indoleamine 2,3 dioxygenase (IDO) -1 in human monocytes derived dendritic cells (MoDC) but not IDO-2 by acting directly at the cell membrane level. This induction of IDO-1 is dependent on the secondary structure of Tat protein, since stimulation with a chemically oxidized Tat protein loses its capacity to induce the production of IDO-1. Among the variety of candidate receptors described for Tat, we demonstrated that Tat protein interacted physically with TLR4/MD2 complex. Strikingly, blockade of Tat-TLR4 interaction by anti-TLR4 antibodies (clone HTA125), LPS-RS, a known TLR4 antagonist, or by soluble recombinant TLR4/MD2 complex inhibited strongly or totally the capacity of Tat to induce IDO-1 in MoDC while such treatments had no effect on IFN-γ-induced IDO-1. Furthermore, we showed that the activation of the transcription factor NF-κB by Tat is essential for the production of IDO-1 by human MoDC. Indeed, Tat activated NF-κB pathway in MoDC as demonstrated by the phosphorylation of p65 in Tat-treated MoDC. Further, we demonstrate that the stimulation of IDO-1 by Tat or by IFN-γ was totally or partially inhibited in the presence of NF-κB inhibitor respectively. These results suggest that Tat and IFN-γ act probably by two distinct mechanisms to induce the production of IDO-1. Our results clearly demonstrated that, although TLR4 pathway is necessary for Tat-induced IDO-1 in MoDC, it seems not to be sufficient since stable transfection of a functional TLR4/MD2 pathway in HEK or HeLa cell lines which are endogenously defectives for TLR4, did not restore the capacity of Tat to induce IDO-1 while IFN-γ treatment induces IDO-1 in HeLa cells independently of TLR4 pathway. These results suggest the involvement of additional stimuli in addition to TLR4 pathway which remain to be identified. Altogether our results demonstrated that, in human MoDC, HIV-1 Tat protein induced IDO-1 expression and activity in a NF-κB dependent-manner by recruiting TLR4 pathway.

Hydroxychloroquine efficiently suppresses inflammatory responses of human class-switched memory B cells via Toll-like receptor 9 inhibition

Hydroxychloroquine is widely used for autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. Although B cells contribute to the pathogenesis of these diseases, the action of hydroxychloroquine on B cells remains unclear. Here we examined the effects of hydroxychloroquine on functions of B cell subsets. Hydroxychloroquine efficiently inhibited the mammalian target of rapamycin complex 1, differentiation of CD19⁺IgD^-CD27⁺ class-switched memory B cells to plasmablasts and their IgG production, under stimulation with CpG, a Toll-like receptor (TLR)-9 ligand. Hydroxychloroquine also inhibited CpG-induced production of interleukin-6 and tumor necrosis factor-α in B cell subsets. Taken together, hydroxychloroquine markedly suppresses the TLR9-mediated human B cell functions during inflammatory processes. Based on our results, we believe that hydroxychloroquine can be beneficial in the treatment of B cell-mediated autoimmune diseases.

Antiviral Activity of Novel Quinoline Derivatives against Dengue Virus Serotype 2

Dengue virus causes dengue fever, a debilitating disease with an increasing incidence in many tropical and subtropical territories. So far, there are no effective antivirals licensed to treat this virus. Here we describe the synthesis and antiviral activity evaluation of two compounds based on the quinoline scaffold, which has shown potential for the development of molecules with various biological activities. Two of the tested compounds showed dose-dependent inhibition of dengue virus serotype 2 in the low and sub micromolar range. The compounds 1 and 2 were also able to impair the accumulation of the viral envelope glycoprotein in infected cells, while showing no sign of direct virucidal activity and acting possibly through a mechanism involving the early stages of the infection. The results are congruent with previously reported data showing the potential of quinoline derivatives as a promising scaffold for the development of new antivirals against this important virus.

Interferon-associated therapies toward HIV control: The back and forth

Human immunodeficiency virus (HIV) induces a persistent and incurable infection. However, the combined antiretroviral treatment (cART) has markedly changed the evolution of the infection and transformed a deadly disease into a manageable chronic infection. Withdrawal of cART generally leads though to resumption of the viral replication. The eradication of the virus from its cellular and anatomical reservoirs remains a goal-to-achieve for a cure. In this context, developing novel therapies contributing to this aim are an important field of research. Type I IFN has antiviral activity, which, before the presence of efficient anti-HIV drugs, has led to the testing of IFN-based therapeutic strategies during the early years of the pandemic. A historical overview of the results and its limitations that were put into light are reviewed here. In addition, several lessons could be drawn. For instance, the efficacy of the IFN-I depends on the timing of its administration and the context. Thus, the persistence of an endogenous IFN-signature, such as that generally observed in viremic patients, seems to be associated with a lower efficacy of IFN. Based on the lessons from previous trials, and in the context of cART and research for a cure, type I Interferon has regained interest and novel therapeutic approaches are currently tested in combination with cART, some with disappointing, other with encouraging results with regard to a reduction in the size of the HIV reservoir and/or delays in viral rebound after cessation of cART. Additional strategies are currently developed in addition to improve the antiviral function of the IFN-I, by using for instance other IFN subtypes than IFN-Iα2. In parallel, the development of innovative strategies aimed at counteracting the excessive activation of the IFN-pathways have been continued and their results are reviewed here as well. Altogether, the use of IFN-I in anti-HIV therapies has gone through distinct phases and many lessons could be drawn. Novel combinations are currently be tested that might provide interesting results.

Interferon-α Subtypes As an Adjunct Therapeutic Approach for Human Immunodeficiency Virus Functional Cure

Human immunodeficiency virus (HIV) establishes life-long latency in infected individuals. Although highly active antiretroviral therapy (HAART) has had a significant impact on the course of HIV infection leading to a better long-term outcome, the pool of latent reservoir remains substantial even under HAART. Numerous approaches have been under development with the goal of eradicating the latent HIV reservoir though with limited success. Approaches that combine immune-mediated control of HIV to activate both the innate and the adaptive immune system under suppressive therapy along with “shock and kill” drugs may lead to a better control of the reactivated virus. Interferon-α (IFN-α) is an innate cytokine that has been shown to activate intracellular defenses capable of restricting and controlling HIV. IFN-α, however, harbors numerous functional subtypes that have been reported to display different binding affinities and potency. Recent studies have suggested that certain subtypes such as IFN-α8 and IFN-α14 have potent anti-HIV activity with little or no immune activation, whereas other subtypes such as IFN-α4, IFN-α5, and IFN-α14 activate NK cells. Could these subtypes be used in combination with other strategies to reduce the latent viral reservoir? Here, we review the role of IFN-α subtypes in HIV infection and discuss the possibility that certain subtypes could be potential adjuncts to a “shock and kill” or therapeutic vaccination strategy leading to better control of the latent reservoir and subsequent functional cure.

The Significance of Type-I Interferons in the Pathogenesis and Therapy of Human Immunodeficiency Virus 1 Infection

Type-I interferons (IFN-I) are a widely expressed family that could promote antivirus immunity in the process of pathogens invasion. In a human immunodeficiency virus 1 (HIV-1)-infected individual, the production of IFN-I can be detected as early as the acute phase and will persist throughout the course of infection. However, sustained stimulation of immune system by IFN-I also contributes greatly to host-mediated immunopathology and diseases progression. Although the protective effects of IFN-I in the acute phase of HIV-1 infection have been observed, more studies recently focus on their detrimental role in the chronic stage. Inhibition of IFN-I signaling may reverse HIV-1-induced immune hyperactivation and furthermore reduce HIV-1 reservoirs, which suggest this strategy may provide a potential way to enhance the therapeutic effect of antiretroviral therapy. Therefore, we review the role of IFN-I in HIV-1 progression, their effects on different immunocytes, and therapeutic prospects targeting the IFN-I system.

Exploring gene expression changes in the amphioxus gill after poly(I:C) challenge using digital expression profiling

Amphioxus, a cephalochordate, is a key model animal for studying the evolution of vertebrate immunity. Recently, studies have revealed that microRNA (miRNA) expression profiles change significantly in the amphioxus gill after immune stimulation, but it remains largely unknown how gene expression responds to immune stress. Elucidating gene expression changes in the amphioxus gill will provide a deeper understanding of the evolution of gill immunity in vertebrates. Here, we used high-throughput RNA sequencing technology (RNA-seq) to conduct tag-based digital gene expression profiling (DGE) analyses of the gills of control Branchiostoma belcheri and of those exposed to the viral mimic, poly(I:C) (pIC). Six libraries were created for the control and treatment groups including three biological replicates per group. A total of 1999 differently expressed genes (DEGs) were obtained, with 571 and 1428 DEGs showing up- or down-regulation, respectively, in the treatment group. Enrichment analysis of gene ontology (GO) terms and pathways revealed that the DEGs were primarily related to immune and defense response, apoptosis, human disease, cancer, protein metabolism, enzyme activity, and regulatory processes. In addition, eight DEGs were randomly selected to validate the RNA-seq data using real-time quantitative PCR (qRT-PCR), and the results confirmed the accuracy of the RNA-seq approach. Next, we screened eight key responding genes to examine the dynamic changes in expression levels at different time points in more detail. The results indicated that expressions of TRADD, MARCH, RNF31, NF-κb, CYP450, TNFRSF6B, IFI and LECT1 were induced to participate in the antiviral response against pIC. This study provides a valuable resource for understanding the role of the amphioxus gill in antiviral immunity and the evolution of gill immunity in vertebrates.

HIV as a Cause of Immune Activation and Immunosenescence

Systemic immune activation has emerged as an essential component of the immunopathogenesis of HIV. It not only leads to faster disease progression, but also to accelerated decline of overall immune competence. HIV-associated immune activation is characterized by an increase in proinflammatory mediators, dysfunctional T regulatory cells, and a pattern of T-cell-senescent phenotypes similar to those seen in the elderly. These changes predispose HIV-infected persons to comorbid conditions that have been linked to immunosenescence and inflamm-ageing, such as atherosclerosis and cardiovascular disease, neurodegeneration, and cancer. In the antiretroviral treatment era, development of such non-AIDS-defining, age-related comorbidities is a major cause of morbidity and mortality. Treatment strategies aimed at curtailing persistent immune activation and inflammation may help prevent the development of these conditions. At present, the most effective strategy appears to be early antiretroviral treatment initiation. No other treatment interventions have been found effective in large-scale clinical trials, and no adjunctive treatment is currently recommended in international HIV treatment guidelines. This article reviews the role of systemic immune activation in the immunopathogenesis of HIV infection, its causes and the clinical implications linked to immunosenescence in adults, and the therapeutic interventions that have been investigated.

Transcriptomic meta-analysis identifies gene expression characteristics in various samples of HIV-infected patients with nonprogressive disease

BACKGROUND

A small proportion of HIV-infected patients remain clinically and/or immunologically stable for years, including elite controllers (ECs) who have undetectable viremia (<50 copies/ml) and long-term nonprogressors (LTNPs) who maintain normal CD4⁺ T cell counts for prolonged periods (>10 years). However, the mechanism of nonprogression needs to be further resolved. In this study, a transcriptome meta-analysis was performed on nonprogressor and progressor microarray data to identify differential transcriptome pathways and potential biomarkers.

METHODS

Using the INMEX (integrative meta-analysis of expression data) program, we performed the meta-analysis to identify consistently differentially expressed genes (DEGs) in nonprogressors and further performed functional interpretation (gene ontology analysis and pathway analysis) of the DEGs identified in the meta-analysis. Five microarray datasets (81 cases and 98 controls in total), including whole blood, CD4⁺ and CD8⁺ T cells, were collected for meta-analysis.

RESULTS

We determined that nonprogressors have reduced expression of important interferon-stimulated genes (ISGs), CD38, lymphocyte activation gene 3 (LAG-3) in whole blood, CD4⁺ and CD8⁺ T cells. Gene ontology (GO) analysis showed a significant enrichment in DEGs that function in the type I interferon signaling pathway. Upregulated pathways, including the PI3K-Akt signaling pathway in whole blood, cytokine-cytokine receptor interaction in CD4⁺ T cells and the MAPK signaling pathway in CD8⁺ T cells, were identified in nonprogressors compared with progressors. In each metabolic functional category, the number of downregulated DEGs was more than the upregulated DEGs, and almost all genes were downregulated DEGs in the oxidative phosphorylation (OXPHOS) and tricarboxylic acid (TCA) cycle in the three types of samples.

CONCLUSIONS

Our transcriptomic meta-analysis provides a comprehensive evaluation of the gene expression profiles in major blood types of nonprogressors, providing new insights in the understanding of HIV pathogenesis and developing strategies to delay HIV disease progression.

Targeting endosomal acidification by chloroquine analogs as a promising strategy for the treatment of emerging viral diseases

Emerging viruses such as HIV, dengue, influenza A, SARS coronavirus, Ebola, and other viruses pose a significant threat to human health. Majority of these viruses are responsible for the outbreaks of pathogenic lethal infections. To date, there are no effective therapeutic strategies available for the prophylaxis and treatment of these infections. Chloroquine analogs have been used for decades as the primary and most successful drugs against malaria. Concomitant with the emergence of chloroquine‐resistant Plasmodium strains and a subsequent decrease in the use as antimalarial drugs, other applications of the analogs have been investigated. Since the analogs have interesting biochemical properties, these drugs are found to be effective against a wide variety of viral infections. As antiviral action, the analogs have been shown to inhibit acidification of endosome during the events of replication and infection. Moreover, immunomodulatory effects of analogs have been beneficial to patients with severe inflammatory complications of several viral diseases. Interestingly, one of the successful targeting strategies is the inhibition of HIV replication by the analogs in vitro which are being tested in several clinical trials. This review focuses on the potentialities of chloroquine analogs for the treatment of endosomal low pH dependent emerging viral diseases.

Naturally Occurring Fc-Dependent Antibody From HIV-Seronegative Individuals Promotes HIV-Induced IFN-α Production

A majority of adults without HIV infection and with a low risk of HIV-exposure have plasma IgG antibodies that enhance the rate and magnitude of HIV-induced interferon alpha (IFN-α) production. Fc-dependent IgG-HIV complexes induce IFN-α rapidly and in high titers in response to HIV concentrations that are too low to otherwise stimulate an effective IFN-α response. IFN-α promoting antibody (IPA) counters HIV-specific inhibition of IFN-α production, and compensates for the inherent delay in IFN-α production common to HIV infection and other viruses. Naturally occurring IPA has the potential to initiate a potent IFN-α response early in the course of HIV mucosal invasion in time to terminate infection prior to the creation of a pool of persistently infected cells. The current study adds IPA as a mediator of an Fc-dependent antiviral state capable of preventing HIV infection.

Activating autophagy to potentiate immunogenic chemotherapy and radiation therapy

Autophagy is fundamental to the maintenance of intracellular homeostasis in virtually all human cells. Accordingly, defective autophagy predisposes healthy cells to undergoing malignant transformation. By contrast, malignant cells are able to harness autophagy to thrive, despite adverse microenvironmental conditions, and to resist therapeutic challenges. Thus, inhibition of autophagy has been proposed as a strategy to kill cancer cells or sensitize them to therapy; however, autophagy is also critical for optimal immune function, and mediates cell-extrinsic homeostatic effects owing to its central role in danger signalling by neoplastic cells responding to immunogenic chemotherapy and/or radiation therapy. In this Perspective, we discuss accumulating preclinical and clinical evidence in support of the all-too-often dismissed possibility that activating autophagy might be a relevant clinical objective that enables an increase in the effectiveness of immunogenic chemotherapy and/or radiation therapy.

Chloroquine inhibited Ebola virus replication in vitro but failed to protect against infection and disease in the in vivo guinea pig model

Ebola virus (EBOV) is highly pathogenic, with a predisposition to cause outbreaks in human populations accompanied by significant mortality. Owing to the lack of approved therapies, screening programmes of potentially efficacious drugs have been undertaken. One of these studies has demonstrated the possible utility of chloroquine against EBOV using pseudotyped assays. In mouse models of EBOV disease there are conflicting reports of the therapeutic effects of chloroquine. There are currently no reports of its efficacy using the larger and more stringent guinea pig model of infection. In this study we have shown that replication of live EBOV is impaired by chloroquine in vitro. However, no protective effects were observed in vivo when EBOV-infected guinea pigs were treated with chloroquine. These results advocate that chloroquine should not be considered as a treatment strategy for EBOV.

The enigma of the clandestine association between chloroquine and HIV-1 infection

OBJECTIVES

The antimalarial drug chloroquine (CQ) dampens the immune system and is used in the treatment of autoimmune disorders. CQ also shows antiviral activity against nonenveloped and enveloped viruses, including HIV-1. Persistent immune activation in chronic HIV-1infection leads to CD4 T-cell depletion. CQ is envisioned to attenuate immune activation and virus activity in HIV-1-infected patients. The role of CQ in immune activation and virus activity is discussed here.

METHODS

To elucidate the effect of CQ on immune activation, a retrospective review of published clinical trials, in vivo experimental studies in animals, and the most relevant in vitro observations in HIV-1-infected cells, together with observations from our own laboratory studies, was carried out and the findings discussed.

RESULTS

In a few clinical studies and animal experiments, CQ was ineffective in decreasing immune activation and HIV-1 infection. In vitro, CQ markedly increased HIV-1 infection in astrocytes and other non-CD4 cells.

CONCLUSIONS

The use of CQ in HIV-1-infected patients is questionable. The evidence for a dampening of immune activation by CQ is inconclusive.

HIV-1 Tat Protein Induces Production of Proinflammatory Cytokines by Human Dendritic Cells and Monocytes/Macrophages through Engagement of TLR4-MD2-CD14 Complex and Activation of NF-κB Pathway

We recently reported that the human immunodeficiency virus type-1 (HIV-1) Tat protein induced the expression of programmed death ligand-1 (PD-L1) on dendritic cells (DCs) through a TLR4 pathway. However, the underlying mechanisms by which HIV-1 Tat protein induces the abnormal hyper-activation of the immune system seen in HIV-1 infected patients remain to be fully elucidated. In the present study, we report that HIV-1 Tat protein induced the production of significant amounts of the pro-inflammatory IL-6 and IL-8 cytokines by DCs and monocytes from both healthy and HIV-1 infected patients. Such production was abrogated in the presence of anti-TLR4 blocking antibodies or soluble recombinant TLR4-MD2 as a decoy receptor, suggesting TLR4 was recruited by Tat protein. Tat-induced murine IL-6 and CXCL1/KC a functional homologue of human IL-8 was abolished in peritoneal macrophages derived from TLR4 KO but not from Wt mice, confirming the involvement of the TLR4 pathway. Furthermore, the recruitment of TLR4-MD2-CD14 complex by Tat protein was demonstrated by the activation of TLR4 downstream pathways including NF-κB and SOCS-1 and by down-modulation of cell surface TLR4 by endocytosis in dynamin and lipid-raft-dependent manners. Collectively, these findings demonstrate, for the first time, that HIV-1 Tat interacts with TLR4-MD2-CD14 complex and activates the NF-κB pathway, leading to overproduction of IL-6 and IL-8 pro-inflammatory cytokines by myeloid cells from both healthy and HIV-1 infected patients. This study reveals a novel mechanism by which HIV-1, via its early expressed Tat protein, hijacks the TLR4 pathway, hence establishing abnormal hyper-activation of the immune system.

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.

Influence of quinacrine and chloroquine on the in vitro 3'-azido-3'-deoxythymidine antiretroviral effect

Background

Antimalarials quinacrine (Qc) and chloroquine (Cq) intercalate DNA, potentiate the activity of other drugs and have lysosomotropic, anti-inflammatory and antiviral activities that could increase the effect of the 3′-azido-3′-deoxythymidine (AZT) antiretroviral agent. The aim of the current study was to evaluate if Qc and Cq could improve the in vitro effect of the antiretroviral AZT agent.

Findings

Inhibition of viral replication in human immunodeficiency virus (HIV)_SF33-infected peripheral blood mononuclear cells treated with Qc or Cq, alone or combined with a low dose of AZT was measured. Viral replication increased with Qc and decreased with high doses of Cq. The increase of replication caused by Qc was reversed by AZT. Neither Qc nor Cq significantly changed the antiviral activity of AZT.

Conclusion

Cq does not potentiate the effect of AZT, but it is effective by itself at high doses. The rise of HIV replication by Qc could be deleterious in HIV endemic regions, where it is used as antimalarial. The mechanisms associated to this phenomenon must be identified.

High secretion of interferons by human plasmacytoid dendritic cells upon recognition of Middle East respiratory syndrome coronavirus

The Middle East respiratory syndrome coronavirus (MERS-CoV) emerged in 2012 as the causative agent of a severe respiratory disease with a fatality rate of approximately 30%. The high virulence and mortality rate prompted us to analyze aspects of MERS-CoV pathogenesis, especially its interaction with innate immune cells such as antigen-presenting cells (APCs). Particularly, we analyzed secretion of type I and type III interferons (IFNs) by APCs, i.e., B cells, macrophages, monocyte-derived/myeloid dendritic cells (MDDCs/mDCs), and by plasmacytoid dendritic cells (pDCs) of human and murine origin after inoculation with MERS-CoV. Production of large amounts of type I and III IFNs was induced exclusively in human pDCs, which were significantly higher than IFN induction by severe acute respiratory syndrome (SARS)-CoV. Of note, IFNs were secreted in the absence of productive replication. However, receptor binding, endosomal uptake, and probably signaling via Toll-like receptor 7 (TLR7) were critical for sensing of MERS-CoV by pDCs. Furthermore, active transcription of MERS-CoV N RNA and subsequent N protein expression were evident in infected pDCs, indicating abortive infection. Taken together, our results point toward dipeptidyl peptidase 4 (DPP4)-dependent endosomal uptake and subsequent infection of human pDCs by MERS-CoV. However, the replication cycle is stopped after early gene expression. In parallel, human pDCs are potent IFN-producing cells upon MERS-CoV infection. Knowledge of such IFN responses supports our understanding of MERS-CoV pathogenesis and is critical for the choice of treatment options.

IMPORTANCE

MERS-CoV causes a severe respiratory disease with high fatality rates in human patients. Recently, confirmed human cases have increased dramatically in both number and geographic distribution. Understanding the pathogenesis of this highly pathogenic CoV is crucial for developing successful treatment strategies. This study elucidates the interaction of MERS-CoV with APCs and pDCs, particularly the induction of type I and III IFN secretion. Human pDCs are the immune cell population sensing MERS-CoV but secrete significantly larger amounts of IFNs, especially IFN-α, than in response to SARS-CoV. A model for molecular virus-host interactions is presented outlining IFN induction in pDCs. The massive IFN secretion upon contact suggests a critical role of this mechanism for the high degree of immune activation observed during MERS-CoV infection.

A parasitic helminth-derived peptide that targets the macrophage lysosome is a novel therapeutic option for autoimmune disease

Parasitic worms (helminths) reside in their mammalian hosts for many years. This is attributable, in part, to their ability to skew the host's immune system away from pro-inflammatory responses and towards anti-inflammatory or regulatory responses. This immune modulatory ability ensures helminth longevity within the host, while simultaneously minimises tissue destruction for the host. The molecules that the parasite releases clearly exert potent immune-modulatory actions, which could be exploited clinically, for example in the prophylactic and therapeutic treatment of pro-inflammatory and autoimmune diseases. We have identified a novel family of immune-modulatory proteins, termed helminth defence molecules (HDMs), which are secreted by several medically important helminth parasites. These HDMs share biochemical and structural characteristics with mammalian cathelicidin-like host defence peptides (HDPs), which are significant components of the innate immune system. Like their mammalian counterparts, parasite HDMs block the activation of macrophages via toll like receptor (TLR) 4 signalling, however HDMs are significantly less cytotoxic than HDPs. HDMs can traverse the cell membrane of macrophages and enter the endolysosomal system where they reduce the acidification of lysosomal compartments by inhibiting vacuolar (v)-ATPase activity. In doing this, HDMs can modulate critical cellular functions, such as cytokine secretion and antigen processing/presentation. Here, we review the role of macrophages, specifically their lysosomal mediated activities, in the initiation and perpetuation of pro-inflammatory immune responses. We also discuss the potential of helminth defence molecules (HDMs) as therapeutics to counteract the pro-inflammatory responses underlying autoimmune disease. Given the current lack of effective, non-cytotoxic treatment options to limit the progression of autoimmune pathologies, HDMs open novel treatment avenues.

Chloroquine use improves dengue-related symptoms

Dengue is the most important arboviral disease in the world. As chloroquine, an antimalarial agent, has shown some antiviral effects, this study evaluated its effect in patients with dengue. A randomised, double-blind study was performed by administering chloroquine or placebo for three days to 129 patients with dengue-related symptoms. Of these patients, 37 were confirmed as having dengue and completed the study; in total, 19 dengue patients received chloroquine and 18 received placebo. There was no significant difference in the duration of the disease or the degree and days of fever. However, 12 patients (63%) with confirmed dengue reported a substantial decrease in pain intensity and a great improvement in their ability to perform daily activities (p = 0.0004) while on the medication and the symptoms returned immediately after these patients stopped taking the medication. The same effect was not observed in patients with diseases other than dengue. Therefore, this study shows that patients with dengue treated with chloroquine had an improvement in their quality of life and were able to resume their daily activities. However, as chloroquine did not alter the duration of the disease or the intensity and days of fever, further studies are necessary to confirm the clinical effects and to assess the side effects of chloroquine in dengue patients.

Assessment of chloroquine as a modulator of immune activation to improve CD4 recovery in immune nonresponding HIV-infected patients receiving antiretroviral therapy

OBJECTIVES

Chloroquine (CQ), an anti-inflammatory drug, inhibits Toll-like receptor (TLR) signalling in plasmacytoid dendritic cells (pDCs) and may be beneficial for HIV-infected patients in whom immune activation persists despite effective antiretroviral therapy (ART). The effect of CQ on CD4 T-cell recovery and immune activation in immune nonresponding patients receiving successful ART was therefore studied.

METHODS

Nineteen adults on ART with CD4 counts ≤ 350 cells/μL and undetectable viral load (VL) orally received CQ at 250 mg/day for 24 weeks. Side effects, CD4 and CD8 T-cell counts, VL, T-cell activation, pDC proportion and plasma inflammatory markers were assessed at baseline, at 24 weeks, and at 12 weeks after CQ discontinuation (clinicaltrial.org registration #NCT02004314).

RESULTS

CQ was well tolerated and all patients maintained an undetectable VL. The absolute CD4 and CD8 T-cell counts and their percentages, the pDC proportion, T-cell activation, D-dimer and C-reactive protein (CRP) plasma levels and the kynurenine/tryptophan ratio did not change with CQ treatment. Among nine cytokines/chemokines measured, only levels of interferon (IFN)-α2 were significantly increased by CQ treatment.

CONCLUSIONS

CQ was well tolerated in patients with low CD4 T-cell counts despite long-term effective ART; however, 24 weeks of CQ treatment did not improved CD4 T-cell recovery, lymphoid and myeloid immune activation or inflammatory markers.

Immune responses during spontaneous control of HIV and AIDS: what is the hope for a cure?

HIV research has made rapid progress and led to remarkable achievements in recent decades, the most important of which are combination antiretroviral therapies (cART). However, in the absence of a vaccine, the pandemic continues, and additional strategies are needed. The 'towards an HIV cure' initiative aims to eradicate HIV or at least bring about a lasting remission of infection during which the host can control viral replication in the absence of cART. Cases of spontaneous and treatment-induced control of infection offer substantial hope. Here, we describe the scientific knowledge that is lacking, and the priorities that have been established for research into a cure. We discuss in detail the immunological lessons that can be learned by studying natural human and animal models of protection and spontaneous control of viraemia or of disease progression. In particular, we describe the insights we have gained into the immune mechanisms of virus control, the impact of early virus-host interactions and why chronic inflammation, a hallmark of HIV infection, is an obstacle to a cure. Finally, we enumerate current interventions aimed towards improving the host immune response.

Modulation of HIV-1-induced activation of plasmacytoid dendritic cells by 6-desfluoroquinolones

Chronic activation of plasmacytoid dendritic cells (pDCs) is an important contributor to the immunopathogenesis of HIV infection. The quinolone derivative chloroquine (CQ) prevents endosomal acidification, required for toll-like receptor sensing of HIV by pDCs, and is currently under clinical trial as an immunotherapeutic approach. We tested three different 6-desfluoroquinolones (6-DFQs), structurally related to CQ and endowed with antiretroviral activity, for their ability to inhibit HIV-induced pDC activation and interferon (IFN)-α production in peripheral blood mononuclear cells (PBMCs) in vitro. PBMCs from six healthy donors were cultured overnight with aldrithiol-2 (AT-2)-inactivated HIV-1MN in the presence or absence of 6-DFQs or CQ. IFN-α production was measured by ELISA; pDC and monocyte activation was analyzed by flow cytometry. Incubation with HIV labeled with the fluorescent dye DyLight-488 (DL488) was used to test virus uptake by flow cytometry. We found that the 6-DFQs effectively inhibited HIV-induced IFN-α similar to CQ, but only 6-DFQs also inhibited the upregulation of the pDC activation marker CD83. Interestingly, HIV-induced expression of the costimulatory molecule CD80 and, to a lesser extent CD86, was further enhanced on pDCs by 6-DFQs, but not CQ. Conversely, 6-DFQs and CQ had similar inhibitory effects on HIV-induced monocyte activation, consistent with the primary mechanism being associated with IFN-α signaling. Finally, 6-DFQs interfered with HIV interaction with pDCs and monocytes, but not myeloid DCs. Our data indicate that 6-DFQs may interfere with pDC-mediated and IFN-α-dependent immunopathogenesis while supporting pDC differentiation into mature antigen-presenting cells by favoring expression of costimulatory molecules.

Transient increase of interferon-stimulated genes and no clinical benefit by chloroquine treatment during acute simian immunodeficiency virus infection of macaques

Simian immunodeficiency virus (SIV) infection leads to AIDS in experimentally infected Rhesus macaques similarly to HIV-infected humans. In contrast, SIV infection of natural hosts is characterized by a down-regulation of innate acute responses to the virus within a few weeks of infection and results in limited pathology. Chloroquine (CQ) has been used in the treatment or prevention of malaria and has recently been shown to cause a decrease of immune activation and CD4 cell loss in HIV-infected individuals treated with antiretroviral therapy. Here, we treated Rhesus macaques with CQ during the acute phase of SIVmac251 infection with the intent to decrease viral-induced immune activation and possibly limit disease progression. Contrary to what was expected, CQ treatment resulted in a temporary increased expression of interferon (IFN)-stimulating genes and it worsened the recovery of CD4(+) T cells in the blood. Our findings confirm recent results observed in asymptomatic HIV-infected patients and suggest that CQ does not provide an obvious benefit in the absence of antiretroviral therapy.

Interferon-alpha, immune activation and immune dysfunction in treated HIV infection

Type I interferons (IFNs) exert anti-viral effects through the induction of numerous IFN-stimulated genes and an immunomodulatory effect on innate and adaptive immune responses. This is beneficial in controlling virus infections but prolonged IFN-α activity in persistent virus infections, such as HIV infection, may contribute to immune activation and have a detrimental effect on the function of monocytes and T and B lymphocytes. Activation of monocytes, associated with increased IFN-α activity, contributes to atherosclerotic vascular disease, brain disease and other ‘age-related diseases' in HIV patients treated with long-term antiretroviral therapy (ART). In HIV patients receiving ART, the anti-viral effects of IFN-α therapy have the potential to contribute to eradication of HIV infection while IFN-α inhibitor therapy is under investigation for the treatment of immune activation. The management of HIV patients receiving ART will be improved by understanding more about the opposing effects of IFN-α on HIV infection and disease and by developing methods to assess IFN-α activity in clinical practice.

Antimalarial drugs inhibit IFNα-enhanced TNFα and STAT4 expression in monocytes: implication for systemic lupus erythematosus

OBJECTIVES

To analyse the influence of IFNα on TNFα production by human peripheral blood mononuclear cells (PBMCs), as well as the possible interference of this cytokine on the effect of antimalarial drugs, TNFα regulators widely used in the treatment of systemic lupus erythematosus (SLE).

METHODS

PBMCs, monocytes or T cells were treated with IFNα alone or simultaneously to cellular stimuli as well as in the presence or absence of chloroquine. Supernatants from such cultures were collected to quantify TNFα by ELISA. TNFα and STAT4 expression in cultured cells were analysed by intracellular flow cytometry. In addition, STAT4 gene expression and serum levels of TNFα and IFNα were quantified in 53 SLE patients and 45 controls.

RESULTS

IFNα alone did not modify significantly TNFα production, but an increase was observed in stimulated PBMC. Further analyses showed that monocytes were the cellular population responsible for this effect. In addition, IFNα treatment increased STAT4 in stimulated monocytes, suggesting that TNFα upregulation could be mediated by STAT4. On the other hand, the analysis of the antimalarial effect showed that chloroquine was able to inhibit in vitro the expression of TNFα and STAT4 enhanced by IFNα. In antimalarial-treated SLE patients, however, only those with high IFNα serum levels presented lower expression of STAT4.

CONCLUSIONS

IFNα treatment enhances the induction of TNFα and STAT4 in stimulated monocytes, an effect inhibited in vitro by chloroquine treatment. However, the consequence of antimalarial treatment on SLE patients could be different depending on their IFNα serum levels.

Immune activation and the role of TLRs and TLR agonists in the pathogenesis of HIV-1 infection in the humanized mouse model

Immune activation plays a critical role in HIV-1 pathogenesis, but the pathways that are responsible for HIV-1-associated immune activation are not well understood. Recent advances in the development of a humanized mouse model for HIV-1 infection might provide new approaches to study the mechanisms of HIV-1 associated immune activation, and to test interventions aimed at reducing HIV-1 pathogenesis.

Decoding the complexity of type I interferon to treat persistent viral infections

Type I interferons (IFN-I) are a broad family of cytokines that are central to the innate immune response. These proteins have long been appreciated for the critical roles they play in restraining viral infections and shaping antiviral immune responses. However, in recent years there has been increased awareness of the immunosuppressive actions of these proteins as well. Although there are many current therapeutic applications to manipulate IFN-I pathways, we have limited understanding of the mechanisms by which these therapies are actually functioning. In this review, we highlight the diversity and temporal impact of IFN-I signaling, discuss the current therapeutic uses of IFN-I, and explore the strategy of blocking IFN-I to alleviate immune dysfunction in persistent virus infections.

Immune quiescence: a model of protection against HIV infection

Aberrant immune activation is a strong correlate of HIV disease progression, but little is known about how immune activation alters susceptibility to HIV infection. Susceptibility to HIV infection varies between individuals, but the immunological determinants of HIV transmission are not well understood. Here, we present evidence from studies of HIV transmission in the context of clinical trials and HIV-exposed seronegative (HESN) cohorts that implicates elevated immune activation as a risk factor for acquiring HIV. We propose a model of protection from infection based on a phenotype of low baseline immune activation referred to as immune quiescence. Immune quiescence is evidenced by reduced expression of T cell activation markers, low levels of generalized gene transcription and low levels of proinflammatory cytokine and chemokine production in the periphery and genital mucosa of HESN. Since HIV preferentially replicates in activated CD4+ T cells, immune quiescence may protect against infection by limiting HIV target cell availability. Although the determinants of immune quiescence are unclear, several potential factors have been identified that may be involved in driving this phenotype. HESN were shown to have elevated proportions of regulatory T cells (Tregs), which are known to suppress T cell activation. Likewise, proteins involved in controlling inflammation in the genital tract have been found to be elevated in HESN. Furthermore, expression of interferon regulatory factor 1 (IRF-1) is reduced in HESN as a consequence of genetic polymorphisms and differential epigenetic regulation. Since IRF-1 is an important regulator of immune responses, it may play a role in maintaining immune quiescence. Based on this model, we propose a novel avenue for HIV prevention targeted based on reducing host mucosal immune activation.

HIV-1 Tat protein induces the production of IDO in human monocyte derived-dendritic cells through a direct mechanism: effect on T cells proliferation

During HIV-1 infection, an increase of indoleamine 2,3 dioxygenase (IDO) expression, and dendritic cells (DC) dysfunction were often associated with AIDS disease progression. In this work, we investigated the effect of HIV-1 Tat protein on the expression of IDO, in MoDCs. We show that Tat induces IDO protein expression and activity in a dose dependent manner by acting at the cell membrane. Using Tat-mutants, we show that the N-Terminal domain, Tat 1–45, but not the central region, Tat 30–72, is sufficient to induce the expression of active IDO. Tat protein is also able to induce several cytokines in MoDCs, including IFN-γ, a strong inducer of IDO. In order to understand whether IDO is induced directly by Tat protein or indirectly following IFN-γ production, complementary experiments were performed and showed that: i) at the kinetic level, Tat induced IDO expression before the production of IFN-γ ii) treatment of MoDCs with Tat-conditioned medium was unable to stimulate IDO expression, iii) coculture of MoDCs in a transwell cell system did not allow IDO expression in MoDCs not previously treated by Tat, iv) direct contact between Tat-treated and untreated MoDCs was not sufficient to induce IDO expression in a Tat-independent manner, and v) treatment of MoDCs in the presence of IFN-γ pathway inhibitors, Jak I and Ly294002, inhibited IFN-γ-induced IDO but had no effect on Tat-induced IDO. At the functional level, our data showed that treatment of MoDCs with Tat led to the inhibition of their capacity to stimulate T cell proliferation. This impairement was totally abolished when the stimulation was performed in the presence of 1MT, an inhibitor of IDO activity, arguing for the implication of the kynurenine pathway. By inducing IDO, Tat protein may be considered, as a viral pathogenic factor, in the dysregulation of the DC functions during HIV-1 infection.

Chloroquine use improves dengue-related symptoms

Dengue is the most important arboviral disease in the world. As chloroquine, an antimalarial agent, has shown some antiviral effects, this study evaluated its effect in patients with dengue. A randomised, double-blind study was performed by administering chloroquine or placebo for three days to 129 patients with dengue-related symptoms. Of these patients, 37 were confirmed as having dengue and completed the study; in total, 19 dengue patients received chloroquine and 18 received placebo. There was no significant difference in the duration of the disease or the degree and days of fever. However, 12 patients (63%) with confirmed dengue reported a substantial decrease in pain intensity and a great improvement in their ability to perform daily activities (p = 0.0004) while on the medication and the symptoms returned immediately after these patients stopped taking the medication. The same effect was not observed in patients with diseases other than dengue. Therefore, this study shows that patients with dengue treated with chloroquine had an improvement in their quality of life and were able to resume their daily activities. However, as chloroquine did not alter the duration of the disease or the intensity and days of fever, further studies are necessary to confirm the clinical effects and to assess the side effects of chloroquine in dengue patients.

Chloroquine: modes of action of an undervalued drug

For more than two decades, chloroquine (CQ) was largely and deliberately used as first choice drug for malaria treatment. However, worldwide increasing cases of resistant strains of Plasmodium have hampered its use. Nevertheless, CQ has recently been tested as adjunct therapy in several inflammatory situations, such as rheumatoid arthritis and transplantation procedures, presenting intriguing and promising results. In this review, we discuss recent findings and CQ mechanisms of action vis-à-vis its use as a broad adjunct therapy.

Understanding and controlling chronic immune activation in the HIV-infected patients suppressed on combination antiretroviral therapy

Combination antiretroviral therapy (cART) has resulted in tremendous gains in survival among HIV-infected patients, but as a group those who achieve undetectable viral loads on cART experience a greater degree of immune activation and inflammation than the general population. HIV-infected patients continue to experience premature immune senescence with earlier and more frequent non-AIDS events compared to HIV-uninfected individuals. Chronic immune activation during suppressive cART derives from a variety of sources mediated by cytokines, chemokines, coagulation, microbial translocation, immune regulators and T(effector) cell activation abnormalities, among others. Current investigational strategies to control immune activation target potential causes of persistently heightened immune activation during cART such as microbial translocation, co-infections, and comorbidities or mediators along a common final pathway. Although several interventions have shown promise in vitro or in preliminary clinical trials, no intervention has sufficient evidence for routine use, making control of immune activation during cART an unmet need.