Statin-induced inhibition of HIV-1 release from latently infected U1 cells reveals a critical role for protein prenylation in HIV-1 replication

Aminobisphosphonates reactivate the latent reservoir in people living with HIV-1

Antiretroviral therapy (ART) is not curative due to the existence of cellular reservoirs of latent HIV-1 that persist during therapy. Current research efforts to cure HIV-1 infection include "shock and kill" strategies to disrupt latency using small molecules or latency-reversing agents (LRAs) to induce expression of HIV-1 enabling cytotoxic immune cells to eliminate infected cells. The modest success of current LRAs urges the field to identify novel drugs with increased clinical efficacy. Aminobisphosphonates (N-BPs) that include pamidronate, zoledronate, or alendronate, are the first-line treatment of bone-related diseases including osteoporosis and bone malignancies. Here, we show the use of N-BPs as a novel class of LRA: we found in ex vivo assays using primary cells from ART-suppressed people living with HIV-1 that N-BPs induce HIV-1 from latency to levels that are comparable to the T cell activator phytohemagglutinin (PHA). RNA sequencing and mechanistic data suggested that reactivation may occur through activation of the activator protein 1 signaling pathway. Stored samples from a prior clinical trial aimed at analyzing the effect of alendronate on bone mineral density, provided further evidence of alendronate-mediated latency reversal and activation of immune effector cells. Decay of the reservoir measured by IPDA was however not detected. Our results demonstrate the novel use of N-BPs to reverse HIV-1 latency while inducing immune effector functions. This preliminary evidence merits further investigation in a controlled clinical setting possibly in combination with therapeutic vaccination.

Aminobisphosphonates reactivate the latent reservoir in people living with HIV-1

Antiretroviral therapy (ART) is not curative due to the existence of cellular reservoirs of latent HIV-1 that persist during therapy. Current research efforts to cure HIV-1 infection include "shock and kill" strategies to disrupt latency using small molecules or latency-reversing agents (LRAs) to induce expression of HIV-1 enabling cytotoxic immune cells to eliminate infected cells. The modest success of current LRAs urges the field to identify novel drugs with increased clinical efficacy. Aminobisphosphonates (N-BPs) that include pamidronate, zoledronate, or alendronate, are the first-line treatment of bone-related diseases including osteoporosis and bone malignancies. Here, we show the use of N-BPs as a novel class of LRA: we found in ex vivo assays using primary cells from ART-suppressed people living with HIV-1 that N-BPs induce HIV-1 from latency to levels that are comparable to the T cell activator phytohemagglutinin (PHA). RNA sequencing and mechanistic data suggested that reactivation may occur through activation of the activator protein 1 signaling pathway. Stored samples from a prior clinical trial aimed at analyzing the effect of alendronate on bone mineral density, provided further evidence of alendronate-mediated latency reversal and activation of immune effector cells. Decay of the reservoir measured by IPDA was however not detected. Our results demonstrate the novel use of N-BPs to reverse HIV-1 latency while inducing immune effector functions. This preliminary evidence merits further investigation in a controlled clinical setting possibly in combination with therapeutic vaccination.

Statins for primary cardiovascular disease prevention among people with HIV: emergent directions

PURPOSE OF REVIEW

While people with HIV (PWH) are living longer due to advances in antiretroviral therapy, recent data have demonstrated an increased risk of cardiovascular disease (CVD) among this population. This increased risk is thought to be due to both traditional (for example, smoking, diabetes) and HIV-specific (for example, inflammation, persistent immune activation) risk factors. This review focuses on the potential for statin therapy to mitigate this increased risk.

RECENT FINDINGS

Several randomized clinical trials have demonstrated that statins, a class of lipid-lowering medications, are effective as a primary CVD prevention strategy among people without HIV. Among PWH, statins have been shown to lower cholesterol, exert immunomodulatory effects, stabilize coronary atherosclerotic plaque, and even induce plaque regression.

SUMMARY

Prevention of CVD among the aging population of people with controlled, but chronic, HIV is vital. Data exploring primary prevention in this context are thus far limited. The Randomized Trial to Prevent Vascular Events in HIV (REPRIEVE) is ongoing; this trial will inform the field by investigating the effects of pitavastatin calcium as a primary prevention strategy for major adverse cardiovascular events among PWH on antiretroviral therapy (ART) at low-to-moderate traditional CVD risk.

Cholesterol Biosynthesis Modulates CSFV Replication

Classical swine fever (CSF) caused by the classical swine fever virus (CSFV) has resulted in severe losses to the pig industry worldwide. It has been proposed that lipid synthesis is essential for viral replication, and lipids are involved in viral protein maturation and envelope production. However, the specific crosstalk between CSFV and host cell lipid metabolism is still unknown. In this study, we found that CSFV infection increased intracellular cholesterol levels in PK-15 cells. Further analysis demonstrated that CSFV infection upregulated PCSK9 expression to block the uptake of exogenous cholesterol by LDLR and enhanced the cholesterol biosynthesis pathway, which disrupted the type I IFN response in PK-15 cells. Our findings provide new insight into the mechanisms underpinning the pathogenesis of CSFV and hint at methods for controlling the disease.

U1 and OM10.1. Myeloid Cell Lines as Surrogate Models of Reversible Proviral Latency

As already discussed for T cell lines, also myeloid cell lines as served as the earliest models of chronic HIV infection. They were particularly relevant in the late 1980s and early 1990s when most experimental in vitro infections were based on laboratory-adapted "T-cell tropic" strains of HIV-1, such as LAI/IIIB or others, that later were found to rely upon CXCR4 as coreceptor for viral entry in addition to CD4 as primary receptor. Although primary macrophages do express CXCR4 together with CD4, virus replication is much less efficient than that observed with CCR5-using "macrophage-tropic" strains, as discussed separately in this book. Although different myeloid cell lines have been used to generate models of chronic HIV-1 infection that could be used to investigate features of proviral reactivation, as reviewed in (Cassol et al. J Leukoc Biol 80:1018-1030, 2006), two cell lines in particular have been broadly used and will be here discussed: the U937-derived U1 and HL-60-derived OM-10.1.

Low-Density Lipoprotein Receptor Suppresses the Endogenous Cholesterol Synthesis Pathway To Oppose Gammaherpesvirus Replication in Primary Macrophages

Gammaherpesviruses are ubiquitous pathogens that establish lifelong infections in >95% of adults worldwide and are associated with several cancers. We have shown that endogenous cholesterol synthesis supports gammaherpesvirus replication. However, the role of exogenous cholesterol exchange and signaling during infection remains poorly understood. Extracellular cholesterol is carried in the serum by several lipoproteins, including low-density lipoproteins (LDL). The LDL receptor (LDL-R) mediates the endocytosis of these cholesterol-rich LDL particles into the cell, thereby supplying the cell with cholesterol. We found that LDL-R expression attenuates gammaherpesvirus replication during the early stages of the replication cycle, as evident by increased viral gene expression in LDL-R^-/- primary macrophages. This was not observed in primary fibroblasts, indicating that the antiviral effects of LDL-R are cell type specific. Increased viral gene expression in LDL-R^-/- primary macrophages was due to increased activity of the endogenous cholesterol synthesis pathway. Intriguingly, despite type I interferon-driven increase in LDL-R mRNA levels in infected macrophages, protein levels of LDL-R continually decreased over the single cycle of viral replication. Thus, our study has uncovered an intriguing tug of war between the LDL-R-driven antiviral effect on cholesterol metabolism and the viral targeting of the LDL-R protein. IMPORTANCE LDL-R is a cell surface receptor that mediates the endocytosis of cholesterol-rich low-density lipoproteins, allowing cells to acquire cholesterol exogenously. Several RNA viruses usurp LDL-R function to facilitate replication; however, the role of LDL-R in DNA virus infection remains unknown. Gammaherpesviruses are double-stranded DNA viruses that are associated with several cancers. Here, we show that LDL-R attenuates gammaherpesvirus replication in primary macrophages by decreasing endogenous cholesterol synthesis activity, a pathway known to support gammaherpesvirus replication. In response, LDL-R protein levels are decreased in infected cells to mitigate the antiviral effects, revealing an intriguing tug of war between the virus and the host.

Strategy, Progress, and Challenges of Drug Repurposing for Efficient Antiviral Discovery

Emerging or re-emerging viruses are still major threats to public health. Prophylactic vaccines represent the most effective way to prevent virus infection; however, antivirals are more promising for those viruses against which vaccines are not effective enough or contemporarily unavailable. Because of the slow pace of novel antiviral discovery, the high disuse rates, and the substantial cost, repurposing of the well-characterized therapeutics, either approved or under investigation, is becoming an attractive strategy to identify the new directions to treat virus infections. In this review, we described recent progress in identifying broad-spectrum antivirals through drug repurposing. We defined the two major categories of the repurposed antivirals, direct-acting repurposed antivirals (DARA) and host-targeting repurposed antivirals (HTRA). Under each category, we summarized repurposed antivirals with potential broad-spectrum activity against a variety of viruses and discussed the possible mechanisms of action. Finally, we proposed the potential investigative directions of drug repurposing.

Dysregulation of the mevalonate pathway during SARS-CoV-2 infection: An in silico study

SARS-CoV-2 triggers a dysregulated innate immune system activation. As the mevalonate pathway (MVP) prevents the activation of inflammasomes and cytokine release and regulates endosomal transport, compromised signaling could be associated with the pathobiology of COVID-19. Prior transcriptomic studies of host cells in response to SARS-CoV-2 infection have not reported to date the effects of SARS-CoV-2 on the MVP. In this study, we accessed public data sets to report in silico investigations into gene expression. In addition, we proposed candidate genes that are thought to have a direct association with the pathogenesis of COVID-19, and which may be dependent on signals derived from the MVP. Our results revealed dysregulation of genes involved in the MVP. These results were not found when investigating the gene expression data from host cells infected with H3N2 influenza virus, H1N1 influenza virus, or respiratory syncytial virus. Our manually curated gene set showed significant gene expression variability in A549 cells infected with SARS-CoV-2, as per Blanco-Melo et al. data set (GSE147507). In light of the present findings, SARS-CoV-2 could hijack the MVP, leading to hyperinflammatory responses. Prompt reconstitution of this pathway with available agents should be considered in future studies.

The Impact of Statin Therapy on the Survival of Patients with Gastrointestinal Cancer

Statins are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors that may play an important role in the evolution of cancers, due to their effects on cancer cell metabolism. Statins affect several potential pathways, including cell proliferation, angiogenesis, apoptosis and metastasis. The number of trials assessing the putative clinical benefits of statins in cancer is increasing. Currently, there are several trials listed on the global trial identifier website clinicaltrials.gov. Given the compelling evidence from these trials in a variety of clinical settings, there have been calls for a clinical trial of statins in the adjuvant gastrointestinal cancer setting. However, randomized controlled trials on specific cancer types in relation to statin use, as well as studies on populations without a clinical indication for using statins, have elucidated some potential underlying biological mechanisms, and the investigation of different statins is probably warranted. It would be useful for these trials to incorporate the assessment of tumour biomarkers predictive of statin response in their design. This review summarizes the recent preclinical and clinical studies that assess the application of statins in the treatment of gastrointestinal cancers with particular emphasize on their association with cancer risk.

Liver X Receptors Suppress Activity of Cholesterol and Fatty Acid Synthesis Pathways To Oppose Gammaherpesvirus Replication

Gammaherpesviruses are oncogenic pathogens that persist in ~95% of the adult population. Cellular metabolic pathways have emerged as important regulators of many viral infections, including infections by gammaherpesviruses that require several lipid synthetic pathways for optimal replication. Liver X receptors (LXRs) are transcription factors that are critical regulators of cellular fatty acid and cholesterol synthesis pathways. Not surprisingly, LXRs are attractive therapeutic targets in cardiovascular disease. Here we describe an antiviral role for LXRs in the context of gammaherpesvirus infection of primary macrophages. We show that type I interferon increased LXR expression following infection. Surprisingly, there was not a corresponding induction of LXR target genes. Rather, LXRs suppressed the expression of target genes, leading to decreased fatty acid and cholesterol synthesis, two metabolic pathways that support gammaherpesvirus replication. This report defines LXR-mediated restriction of cholesterol and lipid synthesis as an intrinsic metabolic mechanism to restrict viral replication in innate immune cells.IMPORTANCE Fatty acid and cholesterol synthesis pathways of the host play important roles in diverse biological systems. Importantly, these two metabolic pathways are also usurped by a number of viruses to facilitate viral replication. In this report, we show that suppression of these pathways by liver X receptors in primary macrophages creates an intrinsic antiviral state that attenuates gammaherpesvirus replication by limiting viral access to the two metabolic pathways.

Statins Suppress Ebola Virus Infectivity by Interfering with Glycoprotein Processing

Ebola virus (EBOV) infection is a major public health concern due to high fatality rates and limited effective treatments. Statins, widely used cholesterol-lowering drugs, have pleiotropic mechanisms of action and were suggested as potential adjunct therapy for Ebola virus disease (EVD) during the 2013-2016 outbreak in West Africa. Here, we evaluated the antiviral effects of statin (lovastatin) on EBOV infection in vitro Statin treatment decreased infectious EBOV production in primary human monocyte-derived macrophages and in the hepatic cell line Huh7. Statin treatment did not interfere with viral entry, but the viral particles released from treated cells showed reduced infectivity due to inhibition of viral glycoprotein processing, as evidenced by decreased ratios of the mature glycoprotein form to precursor form. Statin-induced inhibition of infectious virus production and glycoprotein processing was reversed by exogenous mevalonate, the rate-limiting product of the cholesterol biosynthesis pathway, but not by low-density lipoprotein. Finally, statin-treated cells produced EBOV particles devoid of the surface glycoproteins required for virus infectivity. Our findings demonstrate that statin treatment inhibits EBOV infection and suggest that the efficacy of statin treatment should be evaluated in appropriate animal models of EVD.IMPORTANCE Treatments targeting Ebola virus disease (EVD) are experimental, expensive, and scarce. Statins are inexpensive generic drugs that have been used for many years for the treatment of hypercholesterolemia and have a favorable safety profile. Here, we show the antiviral effects of statins on infectious Ebola virus (EBOV) production. Our study reveals a novel molecular mechanism in which statin regulates EBOV particle infectivity by preventing glycoprotein processing and incorporation into virus particles. Additionally, statins have anti-inflammatory and immunomodulatory effects. Since inflammation and dysregulation of the immune system are characteristic features of EVD, statins could be explored as part of EVD therapeutics.

Inhibition of the mevalonate pathway enhances cancer cell oncolysis mediated by M1 virus

Oncolytic virus is an attractive anticancer agent that selectively lyses cancer through targeting cancer cells rather than normal cells. Although M1 virus is effective against several cancer types, certain cancer cells present low sensitivity to it. Here we identified that most of the components in the cholesterol biosynthesis pathway are downregulated after M1 virus infection. Further functional studies illustrate that mevalonate/protein farnesylation/ras homolog family member Q (RHOQ) axis inhibits M1 virus replication. Further transcriptome analysis shows that RHOQ knockdown obviously suppresses Rab GTPase and ATP-mediated membrane transporter system, which may mediate the antiviral effect of RHOQ. Based on this, inhibition of the above pathway significantly enhances the anticancer potency of M1 virus in vitro, in vivo, and ex vivo. Our research provides an intriguing strategy for the rational combination of M1 virus with farnesyl transferase inhibitors to enhance therapeutic efficacy.

Oncolytic viruses selectively kill tumour cells and induce anti-tumour immunity. Here, the AUs demonstrate the anti-viral effect of the mevalonate pathway on oncolytic virus M1 in refractory cancer cells and provide evidence for a combination strategy of targeting the mevalonate pathway for potentiating oncolytic virus therapy.

Protein Lipidation: Occurrence, Mechanisms, Biological Functions, and Enabling Technologies

Protein lipidation, including cysteine prenylation, N-terminal glycine myristoylation, cysteine palmitoylation, and serine and lysine fatty acylation, occurs in many proteins in eukaryotic cells and regulates numerous biological pathways, such as membrane trafficking, protein secretion, signal transduction, and apoptosis. We provide a comprehensive review of protein lipidation, including descriptions of proteins known to be modified and the functions of the modifications, the enzymes that control them, and the tools and technologies developed to study them. We also highlight key questions about protein lipidation that remain to be answered, the challenges associated with answering such questions, and possible solutions to overcome these challenges.

Lipids in infectious diseases - The case of AIDS and tuberculosis

Lipids play a central role in many infectious diseases. AIDS (Acquired Immune Deficiency Syndrome) and tuberculosis are two of the deadliest infectious diseases to have struck mankind. The pathogens responsible for these diseases, Human Immunodeficiency Virus-1 and Mycobacterium tuberculosis, rely on lipids and on lipid membrane properties to gain access to their host cells, to persist in them and ultimately to egress from their hosts. In this Review, we discuss the life cycles of these pathogens and the roles played by lipids and membranes. We then give an overview of therapies that target lipid metabolism, modulate host membrane properties or implement lipid-based drug delivery systems. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

Evaluation of anti-Zika virus activities of broad-spectrum antivirals and NIH clinical collection compounds using a cell-based, high-throughput screen assay

Recent studies have clearly underscored the association between Zika virus (ZIKV) and severe neurological diseases such as microcephaly and Guillain-Barre syndrome. Given the historical complacency surrounding this virus, however, no significant antiviral screenings have been performed to specifically target ZIKV. As a result, there is an urgent need for a validated screening method and strategy that is focused on highlighting potential anti-ZIKV inhibitors that can be further advanced via rigorous validation and optimization. To address this critical gap, we sought to test whether a cell-based assay that measures protection from the ZIKV-induced cytopathic effect could serve as a high-throughput screen assay for discovering novel anti-ZIKV inhibitors. Employing this approach, we tested the anti-ZIKV activity of previously known broad-spectrum antiviral compounds and discovered several compounds (e.g., NITD008, SaliPhe, and CID 91632869) with anti-ZIKV activity. Interestingly, while GTP synthesis inhibitors (e.g., ribavirin or mycophenolic acid) were too toxic or showed no anti-ZIKV activity (EC₅₀ > 50 μM), ZIKV was highly susceptible to pyrimidine synthesis inhibitors (e.g., brequinar) in the assay. We amended the assay into a high-throughput screen (HTS)-compatible 384-well format and then screened the NIH Clinical Compound Collection library, which includes a total of 727 compounds organized, using an 8-point dose response format with two Zika virus strains (MR766 and PRVABC59, a recent human isolate). The screen discovered 6-azauridine and finasteride as potential anti-ZIKV inhibitors with EC₅₀ levels of 3.18 and 9.85 μM for MR766, respectively. We further characterized the anti-ZIKV activity of 6-azauridine and several pyrimidine synthesis inhibitors such as brequinar in various secondary assays including an antiviral spectrum test within flaviviruses and alphaviruses, Western blot (protein), real-time PCR (RNA), and plaque reduction assays (progeny virus). From these assays, we discovered that brequinar has potent anti-ZIKV activity. Our results show that a broad anti-ZIKV screen of compound libraries with our CPE-based HTS assay will reveal multiple chemotypes that could be pursued as lead compounds for therapies to treat ZIKV-associated diseases or as molecular probes to study the biology of the ZIKV replication mechanism.

The role of statins in the setting of HIV infection

HIV-infected individuals are at an increased risk of cardiovascular disease (CVD) and other HIV-related co-morbidities. This is due in part to dyslipidemia associated with antiretroviral therapy and increased inflammation and immune activation from chronic HIV infection. Statins not only have potent lipid-lowering properties but are also anti-inflammatory and immunomodulators. Studies suggest that statin therapy in the HIV-infected population may decrease the risk of CVD and other non-AIDS-defining co-morbidities. This review summarizes the recent literature on statin use in the HIV setting.

Type I Interferon Counteracts Antiviral Effects of Statins in the Context of Gammaherpesvirus Infection

The cholesterol synthesis pathway is a ubiquitous cellular biosynthetic pathway that is attenuated therapeutically by statins. Importantly, type I interferon (IFN), a major antiviral mediator, also depresses the cholesterol synthesis pathway. Here we demonstrate that attenuation of cholesterol synthesis decreases gammaherpesvirus replication in primary macrophages in vitro and reactivation from peritoneal exudate cells in vivo. Specifically, the reduced availability of the intermediates required for protein prenylation was responsible for decreased gammaherpesvirus replication in statin-treated primary macrophages. We also demonstrate that statin treatment of a chronically infected host attenuates gammaherpesvirus latency in a route-of-infection-specific manner. Unexpectedly, we found that the antiviral effects of statins are counteracted by type I IFN. Our studies suggest that type I IFN signaling counteracts the antiviral nature of the subdued cholesterol synthesis pathway and offer a novel insight into the utility of statins as antiviral agents.

IMPORTANCE

Statins are cholesterol synthesis inhibitors that are therapeutically administered to 12.5% of the U.S.

POPULATION

Statins attenuate the replication of diverse viruses in culture; however, this attenuation is not always obvious in an intact animal model. Further, it is not clear whether statins alter parameters of highly prevalent chronic herpesvirus infections. We show that statin treatment attenuated gammaherpesvirus replication in primary immune cells and during chronic infection of an intact host. Further, we demonstrate that type I interferon signaling counteracts the antiviral effects of statins. Considering the fact that type I interferon decreases the activity of the cholesterol synthesis pathway, it is intriguing to speculate that gammaherpesviruses have evolved to usurp the type I interferon pathway to compensate for the decreased cholesterol synthesis activity.

Atorvastatin restricts HIV replication in CD4+ T cells by upregulation of p21

OBJECTIVE

Antigen persistence due to HIV is a major source of inflammation and substantial immune activation, both of which are linked to accelerated aging. This illustrates the need to reduce immune activation in these patients and subsequently decrease the risk of cardiovascular diseases and other non-AIDS-defining comorbidities.

METHODS

CD4 T cells were infected with HIV-1 isolates in the presence or absence of atorvastatin (0.25 to 1 μg/ml) for 24-48 h. Atorvastatin-induced anti-inflammatory functions and anti-viral replication were measured in vitro.

RESULTS

Atorvastatin, a lipid-lowering medication, exerted a broad spectrum of anti-inflammatory functions by reducing T-cell immune activation markers (e.g. CD38, HLA-DR and Ki67), lowering HIV-1 co-receptor CCR-5, and decreasing proliferative capabilities of CD4 T cells in vitro. In contrast, atorvastatin expanded regulatory T cells (Tregs) and upregulated the expression of T-cell immunoglobulin and ITIM domain (TIGIT), which enhanced the suppressive activity of Tregs. Furthermore, atorvastatin upregulated the cyclin-dependent kinase inhibitor p21, which is also known as cip-1 and waf-1, in the CD4 T cells. Upregulation of p21 in CD4 T cells rendered them less susceptible to HIV-1 infection and replication whereas siRNA-mediated p21 depletion and/or p21 selective inhibitor rescued viral replication. Interestingly, atorvastatin reduced HIV infection in both rested and phytohemagglutinin-activated CD4 T cells in vitro. Finally, atorvastatin mediated p21 upregulation occurred via mevalonate pathway, but independent of p53.

CONCLUSION

The results demonstrate a novel mechanism by which atorvastatin induced resistance of CD4 T cells to HIV-1 infection via p21 upregulation and suggest that statins may hold particular promise for some HIV-infected individuals.

Antileishmanial effect of mevastatin is due to interference with sterol metabolism

Visceral leishmaniasis (VL) is one of the most severe forms of leishmaniasis which is fatal if left untreated. Sterol biosynthetic pathway in Leishmania is currently being explored for its therapeutic potential. In the present study, we have evaluated the antileishmanial efficacy of mevastatin, a known inhibitor of 3-hydroxy-3-methyl glutaryl-CoA reductase (HMGR) enzyme. Mevastatin inhibited Leishmania donovani promastigotes and intracellular amastigotes with an 50% inhibitory concentration (IC50) value of 23.8 ± 4.2 and 7.5 ± 1.1 μM, respectively, without exhibiting toxicity towards host cell line. Mevastatin also inhibited recombinant L. donovani HMGR (LdHMGR) enzyme activity with an IC50 value of 42.2 ± 3.0 μM. Kinetic analysis revealed that the inhibition of recombinant LdHMGR activity by mevastatin was competitive with HMG-CoA. Mevastatin-treated parasites exhibited 66% reduction in ergosterol levels with respect to untreated parasites. Incubation of mevastatin-treated L. donovani promastigotes with ergosterol resulted in revival of cell growth, whereas cholesterol supplementation failed to cause reversal in cell death. To further prove the specificity of mevastatin for HMGR enzyme, HMGR-overexpressing parasites were used which showed almost threefold resistance to mevastatin. It also induced morphological changes in the parasite accompanied by lipid body accumulation. Hence, antileishmanial effect of mevastatin was due to the inhibition of HMGR, which eventually leads to reduction in ergosterol levels and hence parasite death. The present study may have implications in the treatment of visceral form of leishmaniasis.

Understanding the molecular mechanism of host-based statin resistance in hepatitis C virus replicon containing cells

A number of statins, the cholesterol-lowering drugs, inhibit the in vitro replication of hepatitis C virus (HCV). In HCV-infected patients, addition of statins to the earlier standard of care therapy (pegIFN-α and ribavirin) resulted in increased sustained virological response rates. The mechanism by which statins inhibit HCV replication has not yet been elucidated. In an attempt to gain insight in the underlying mechanism, hepatoma cells carrying an HCV replicon were passaged in the presence of increasing concentrations of fluvastatin. Fluvastatin-resistant replicon containing cells could be generated and proved ∼8-fold less susceptible to fluvastatin than wild-type cultures. The growth efficiency of the resistant replicon containing cells was comparable to that of wild-type replicon cells. The fluvastatin-resistant phenotype was not conferred by mutations in the viral genome but is caused by cellular changes. The resistant cell line had a markedly increased HMG-CoA reductase expression upon statin treatment. Furthermore, the expression of the efflux transporter P-gp was increased in fluvastatin-resistant replicon cells (determined by qRT-PCR and flow cytometry). This increased expression resulted also in an increased functional transport activity as measured by the P-gp mediated efflux of calcein AM. In conclusion, we demonstrate that statin resistance in HCV replicon containing hepatoma cells is conferred by changes in the cellular environment.

[Microbial metabolites that inhibit sterol biosynthesis, their chemical diversity and characteristics of mode of action]

Inhibitors of sterol biosynthesis (ISB) are widespread in nature and characterized by appreciable diversity both in their chemical structure and mode of action. Many of these inhibitors express noticeable biological activity and approved themselves in development of various pharmaceuticals. In this review there is a detailed description of biologically active microbial metabolites with revealed chemical structure that have ability to inhibit sterol biosynthesis. Inhibitors of mevalonate pathway in fungous and mammalian cells, exhibiting hypolipidemic or antifungal activity, as well as inhibitors of alternative non-mevalonate (pyruvate gliceraldehyde phosphate) isoprenoid pathway, which are promising in the development of affective antimicrobial or antiparasitic drugs, are under consideration in this review. Chemical formulas of the main natural inhibitors and their semi-synthetic derivatives are represented. Mechanism of their action at cellular and biochemical level is discussed. Special attention is given to inhibitors of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase (group of lovastatin) and inhibitors of acyl-CoA-cholesterol-acyl transferase (ACAT) that possess hypolipidemic activity and could be affective in the treatment of atherosclerosis. In case of inhibitors of late stages of sterol biosynthesis (after squalene formation) special attention is paid to compounds possessing evident antifungal and antitumoral activity. Explanation of mechanism of anticancer and antiviral action of microbial ISB, as well as the description of their ability to induce apoptosis is given.

Antiviral drug discovery: broad-spectrum drugs from nature

Covering: up to April 2014. The development of drugs with broad-spectrum antiviral activities is a long pursued goal in drug discovery. It has been shown that blocking co-opted host-factors abrogates the replication of many viruses, yet the development of such host-targeting drugs has been met with scepticism mainly due to toxicity issues and poor translation to in vivo models. With the advent of new and more powerful screening assays and prediction tools, the idea of a drug that can efficiently treat a wide range of viral infections by blocking specific host functions has re-bloomed. Here we critically review the state-of-the-art in broad-spectrum antiviral drug discovery. We discuss putative targets and treatment strategies, with particular focus on natural products as promising starting points for antiviral lead development.

Opposing regulation of endolysosomal pathways by long-acting nanoformulated antiretroviral therapy and HIV-1 in human macrophages

BACKGROUND

Long-acting nanoformulated antiretroviral therapy (nanoART) is designed to improve patient regimen adherence, reduce systemic drug toxicities, and facilitate clearance of human immunodeficiency virus type one (HIV-1) infection. While nanoART establishes drug depots within recycling and late monocyte-macrophage endosomes, whether or not this provides a strategic advantage towards viral elimination has not been elucidated.

RESULTS

We applied quantitative SWATH-MS proteomics and cell profiling to nanoparticle atazanavir (nanoATV)-treated and HIV-1 infected human monocyte-derived macrophages (MDM). Native ATV and uninfected cells served as controls. Both HIV-1 and nanoATV engaged endolysosomal trafficking for assembly and depot formation, respectively. Notably, the pathways were deregulated in opposing manners by the virus and the nanoATV, likely by viral clearance. Paired-sample z-scores, of the proteomic data sets, showed up- and down- regulation of Rab-linked endolysosomal proteins. NanoART and native ATV treated uninfected cells showed limited effects. The data was confirmed by Western blot. DAVID and KEGG bioinformatics analyses of proteomic data showed relationships between secretory, mobility and phagocytic cell functions and virus and particle trafficking.

CONCLUSIONS

We posit that modulation of endolysosomal pathways by antiretroviral nanoparticles provides a strategic path to combat HIV infection.

Matrix conditions and KLF2-dependent induction of heme oxygenase-1 modulate inhibition of HCV replication by fluvastatin

Background & Aims

HMG-CoA-reductase-inhibitors (statins) have been shown to interfere with HCV replication in vitro. We investigated the mechanism, requirements and contribution of heme oxygenase-1(HO-1)-induction by statins to interference with HCV replication.

Methods

HO-1-induction by fluva-, simva-, rosuva-, atorva- or pravastatin was correlated to HCV replication, using non-infectious replicon systems as well as the infectious cell culture system. The mechanism of HO-1-induction by statins as well as its relevance for interference with HCV replication was investigated using transient or permanent knockdown cell lines. Polyacrylamide(PAA) gels of different density degrees or the Rho-kinase-inhibitor Hydroxyfasudil were used in order to mimic matrix conditions corresponding to normal versus fibrotic liver tissue.

Results

All statins used, except pravastatin, decreased HCV replication and induced HO-1 expression, as well as interferon response in vitro. HO-1-induction was mediated by reduction of Bach1 expression and induction of the Nuclear factor (erythroid-derived 2)-like 2 (NRF2) cofactor Krueppel-like factor 2 (KLF2). Knockdown of KLF2 or HO-1 abrogated effects of statins on HCV replication. HO-1-induction and anti-viral effects of statins were more pronounced under cell culture conditions mimicking advanced stages of liver disease.

Conclusions

Statin-mediated effects on HCV replication seem to require HO-1-induction, which is more pronounced in a microenvironment resembling fibrotic liver tissue. This implicates that certain statins might be especially useful to support HCV therapy of patients at advanced stages of liver disease.

Simvastatin modulates cellular components in influenza A virus-infected cells

Influenza A virus is one of the most important health risks that lead to significant respiratory infections. Continuous antigenic changes and lack of promising vaccines are the reasons for the unsuccessful treatment of influenza. Statins are pleiotropic drugs that have recently served as anti-influenza agents due to their anti-inflammatory activity. In this study, the effect of simvastatin on influenza A-infected cells was investigated. Based on the MTT cytotoxicity test, hemagglutination (HA) assay and qPCR it was found that simvastatin maintained cell viability and decreased the viral load significantly as compared to virus-inoculated cells. The expression of important pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-6 and interferon-γ), which was quantified using ELISA showed that simvastatin decreased the expression of pro-inflammatory cytokines to an average of 2-fold. Furthermore, the modulation of actin filament polymerization was determined using rhodamine staining. Endocytosis and autophagy processes were examined by detecting Rab and RhoA GTPase protein prenylation and LC3 lipidation using western blotting. The results showed that inhibiting GTPase and LC3 membrane localization using simvastatin inhibits influenza replication. Findings of this study provide evidence that modulation of RhoA, Rabs and LC3 may be the underlying mechanisms for the inhibitory effects of simvastatin as an anti-influenza compound.

Are statins a viable option for the treatment of infections with the hepatitis C virus?

Statins are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors that are widely used for the treatment of hypercholesterolemia. Besides their cholesterol-lowering effect, statins have been reported to have antiviral activity against a variety of viruses, including hepatitis C virus (HCV). Several statins inhibit the in vitro replication of subgenomic HCV replicons and also suppress in vitro RNA replication of infectious HCV. The precise mechanism of the anti-HCV activity of statins has not yet been defined. Recent studies suggest that the antiviral effect may result from the inhibition of geranylgeranylation of cellular proteins, rather than the inhibition of cholesterol synthesis. Despite the antiviral effect observed in vitro, statin monotherapy seems to be insufficient for the treatment of chronic HCV infection. However, several prospective and retrospective studies have demonstrated that the addition of statins to IFN-α and ribavirin therapy increases SVR, RVR, and EVR rates without the occurrence of additional adverse events. These clinical data, together with the excellent safety profile and low cost, suggest that statins may play a role in HCV therapy until more potent and safe direct-acting antivirals become available. This article forms part of a symposium in Antiviral Research on "Hepatitis C: next steps toward global eradication."

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.

Two-year treatment with rosuvastatin reduces carotid intima-media thickness in HIV type 1-infected patients receiving highly active antiretroviral therapy with asymptomatic atherosclerosis and moderate cardiovascular risk

Recent studies have shown that rosuvastatin significantly decreases serum levels of inflammatory biomarkers and slows progression of carotid atherosclerosis in the general population. However, there are no data about its effect on progression of atherosclerosis in HIV-infected patients. Adult patients with HIV infection, on stable antiretroviral therapy, with asymptomatic carotid atherosclerosis and hypercholesterolemia, who started a rosuvastatin treatment at 10 mg daily during the period 2007-2009 were enrolled and followed-up for 24 months. Thirty-six patients (30 males) were enrolled, with a mean age of 49 years, a mean duration of current antiretroviral therapy of 38 months, and a mean 10-year risk of myocardial infarction of 18.5%. Rosuvastatin led to a significant decrease in mean values of intima-media thickness in all extracranial carotid arteries, with the greatest magnitude observed in carotid bifurcations (a mean decrease of 18.7% in the right artery and of 21.4% in the left artery) and in internal carotid arteries (a mean decrease of 23.7% in the right artery and of 25.6% in the left artery). Moreover, there was a significant reduction in mean levels of total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides versus respective baseline values associated with a significantly decreased mean cardiovascular risk. The treatment with rosuvastatin was well tolerated, and serious adverse events were not reported. A 24-month treatment with rosuvastatin in HIV-infected patients on highly active antiretroviral therapy (HAART) with subclinical atherosclerosis and a moderate cardiovascular risk seems to promote significantly favorable changes in carotid atherosclerosis, associated with a favorable effect on serum lipid levels and a good tolerability profile.

The transcription factor STAT-1 couples macrophage synthesis of 25-hydroxycholesterol to the interferon antiviral response

Recent studies suggest that the sterol metabolic network participates in the interferon (IFN) antiviral response. However, the molecular mechanisms linking IFN with the sterol network and the identity of sterol mediators remain unknown. Here we report a cellular antiviral role for macrophage production of 25-hydroxycholesterol (cholest-5-en-3β,25-diol, 25HC) as a component of the sterol metabolic network linked to the IFN response via Stat1. By utilizing quantitative metabolome profiling of all naturally occurring oxysterols upon infection or IFN-stimulation, we reveal 25HC as the only macrophage-synthesized and -secreted oxysterol. We show that 25HC can act at multiple levels as a potent paracrine inhibitor of viral infection for a broad range of viruses. We also demonstrate, using transcriptional regulatory-network analyses, genetic interventions and chromatin immunoprecipitation experiments that Stat1 directly coupled Ch25h regulation to IFN in macrophages. Our studies describe a physiological role for 25HC as a sterol-lipid effector of an innate immune pathway.

Identification of cellular proteins required for replication of human immunodeficiency virus type 1

Cellular proteins are essential for human immunodeficiency virus type 1 (HIV-1) replication and may serve as viable new targets for treating infection. Using gene trap insertional mutagenesis, a high-throughput approach based on random inactivation of cellular genes, candidate genes were found that limit virus replication when mutated. Disrupted genes (N=87) conferring resistance to lytic infection with several viruses were queried for an affect on HIV-1 replication by utilizing small interfering RNA (siRNA) screens in TZM-bl cells. Several genes regulating diverse pathways were found to be required for HIV-1 replication, including DHX8, DNAJA1, GTF2E1, GTF2E2, HAP1, KALRN, UBA3, UBE2E3, and VMP1. Candidate genes were independently tested in primary human macrophages, toxicity assays, and/or Tat-dependent β-galactosidase reporter assays. Bioinformatics analyses indicated that several host factors present in this study participate in canonical pathways and functional processes implicated in prior genome-wide studies. However, the genes presented in this study did not share identity with those found previously. Novel antiviral targets identified in this study should open new avenues for mechanistic investigation.

Effect of statin treatments on highly pathogenic avian influenza H5N1, seasonal and H1N1pdm09 virus infections in BALB/c mice

Statins are used to control elevated cholesterol or hypercholesterolemia, but have previously been reported to have antiviral properties. AIMS: To show efficacy of statins in various influenza virus mouse models. MATERIALS & METHODS: BALB/c mice were treated intraperitoneally or orally with several types of statins (simvastatin, lovastatin, mevastatin, pitavastatin, atorvastatin or rosuvastatin) at various concentrations before or after infection with either influenza A/Duck/ MN/1525/81 H5N1 virus, influenza A/Vietnam/1203/2004 H5N1 virus, influenza A/ Victoria/3/75 H3N2 virus, influenza A/NWS/33 H1N1 virus or influenza A/CA/04/09 H1N1pdm09 virus. RESULTS: The statins administered intraperitoneally or orally at any dose did not significantly enhance the total survivors relative to untreated controls. In addition, infected mice receiving any concentration of statin were not protected against weight loss due to the infection. None of the statins significantly increased the mean day of death relative to mice in the placebo treatment group. Furthermore, the statins had relatively few ameliorative effects on lung pathology or lung weights at day 3 and 6 after virus exposure, although mice treated with simvastatin did have improved lung function as measured by arterial saturated oxygen levels in one experiment. CONCLUSION: Statins showed relatively little efficacy in any mouse model used by any parameter tested.

Statin therapy decreases serum levels of high-sensitivity C-reactive protein and tumor necrosis factor-α in HIV-infected patients treated with ritonavir-boosted protease inhibitors

BACKGROUND

Statins are lipid-lowering drugs that exhibit anti-inflammatory and immune-modulatory properties, leading to a reduction of serum levels of C-reactive protein (CRP) in the general population.

OBJECTIVE

Because very limited data are available today, our objective was to assess the lipid-lowering effects of statins and their capacity to decrease selected soluble markers of inflammation in HIV-infected patients.

METHODS

Retrospective cohort study of HIV-infected adult patients with hypercholesterolemia who were receiving a stable antiretroviral regimen including a ritonavir-boosted protease inhibitor and who started a lipid-lowering therapy with rosuvastatin (10 mg daily), atorvastatin (10 mg daily), or pravastatin (40 mg daily) and were followed-up for at least 12 months. One hundred and fifty-one patients were enrolled in the study: 51 in the rosuvastatin group, 47 in the atorvastatin group, and 53 in the pravastatin group. The primary observation was change in plasma lipid levels and serum markers of inflammation (high-sensitivity C-reactive protein [hsCRP], interleukin-6 [IL-6], and tumor necrosis factor-α [TNF- α]), while secondary observations include immunovirological parameters and safety profile of statins.

RESULTS

One year after starting the statin therapy, patients treated with rosuvastatin had significantly greater decreases in total cholesterol and LDL cholesterol than subjects on atorvastatin or pravastatin. All statins led to a similar, significant reduction in serum levels of hsCRP and TNF-α, without correlation between biomarkers and lipid values, and toxicity rates were similar for all 3 statins.

CONCLUSION

Our findings suggest that rosuvastatin has a significantly greater lipid-lowering effect than atorvastatin or pravastatin, but all 3 statins exert a similar effect in lowering markers of inflammation as hsCRP and TNF-α.

Inhibition or deficiency of cathepsin B leads defects in HIV-1 Gag pseudoparticle release in macrophages and HEK293T cells

Human immunodeficiency virus type 1 (HIV-1) egresses from infected cells through utilizing the host membrane budding mechanisms. Assembly of HIV-1 Gag particles occurs on membranes where the Gag multimers subsequently bud off and form enveloped viral particles. In certain cell types such as macrophages, HIV-1 Gag particles have shown to be released into intracellular virus containing compartments (VCC) such as late endosomes, multivesicular bodies (MVBs) or invaginated plasma membrane pockets. Here, we showed that macrophages or HEK293T cells treated with the cathepsin B (CTSB)-specific inhibitor CA-074Me or cells deficient in CTSB failed to release HIV-1 Gag pseudoparticles into the extracellular environment. Based on immunofluorescence and electron microscopy, these cells retained the pseudoparticles in heterogeneous intracellular VCC. CA-074Me was also able to inhibit propagation of two enveloped viruses, herpes simplex virus and influenza A virus, but not non-enveloped enterovirus. These results suggest that CTSB is required for the efficient release of HIV-1 Gag pseudoparticles and targeting CTSB can be a new therapeutic strategy for inhibiting egress of HIV-1 and other enveloped viruses.

Association between use of HMG CoA reductase inhibitors and mortality in HIV-infected patients

INTRODUCTION

HIV infection is a disease associated with chronic inflammation and immune activation. Antiretroviral therapy reduces inflammation, but not to levels in comparable HIV-negative individuals. The HMG-coenzyme A reductase inhibitors (statins) inhibit several pro-inflammatory processes and suppress immune activation, and are a logical therapy to assess for a possible salutary effect on HIV disease progression and outcomes.

METHODS

Eligible patients were patients enrolled in the Johns Hopkins HIV Clinical Cohort who achieved virologic suppression within 180 days of starting a new highly active antiretroviral therapy (HAART) regimen after January 1, 1998. Assessment was continued until death in patients who maintained a virologic suppression, with right-censoring of their follow-up time if they had an HIV RNA > 500 copies/ml. Cox proportional hazards regression was used to assess statin use as a time-varying covariate, as well as other demographic and clinical factors.

RESULTS

A total of 1538 HIV-infected patients fulfilled eligibility criteria, of whom 238 (15.5%) received a statin while taking HAART. There were 85 deaths (7 in statin users, 78 in non-users). By multivariate Cox regression, statin use was associated with a relative hazard of 0.33 (95% CI: 0.14, 0.76; P =  0.009) after adjusting for CD4, HIV-1 RNA, hemoglobin and cholesterol levels at the start of HAART, age, race, HIV risk group, prior use of ART, year of HAART start, NNRTI vs. PI-based ART, prior AIDS-defining illness, and viral hepatitis coinfection. Malignancy, non-AIDS-defining infection and liver failure were particularly prominent causes of death.

DISCUSSION

Statin use was associated with significantly lower hazard of dying in these HIV-infected patients who were being effectively treated with HAART as determined by virologic suppression. Our results suggest the need for confirmation in other observational cohorts, and if confirmed, the need for a clinical trial of statin use in HIV infection.

Approach to dyslipidemia, lipodystrophy, and cardiovascular risk in patients with HIV infection

There is a significant prevalence (20%–80% depending on the population and the study) of lipid disorders and other cardiovascular risk factors in people living with HIV infection. This review focuses on HIV and HIV treatment–associated metabolic and cardiovascular concerns, including dyslipidemias, lipodystrophy syndromes, endothelial dysfunctions, and associated metabolic events such as insulin resistance. Emerging hypotheses of the underlying pathophysiology of these issues, with impact on selection of specific antiretroviral treatment (ART) strategies, therapy, and preventive approaches to decreasing cardiovascular risk and other problems associated with these syndromes are discussed. Screening for cardiovascular risk as part of the decision of starting antiretroviral therapy, and during care of patients with HIV regardless of ART therapy status, is suggested with particular areas of focus. Statins, other hyperlipidemic therapies, treatment for specific problems arising due to lipodystrophy, and implications on ART selection to avoid drug interactions and adverse effects are also discussed.