Involvement of fatty acid synthase in dengue virus infection

Alpha and gamma mangostins inhibit wild-type B SARS-CoV-2 more effectively than the SARS-CoV-2 variants and the major target is unlikely the 3C-like protease

Background

Anti-SARS-CoV-2 and immunomodulatory drugs are important for treating clinically severe patients with respiratory distress symptoms. Alpha- and gamma-mangostins (AM and GM) were previously reported as potential 3C-like protease (3CLpro) and Angiotensin-converting enzyme receptor 2 (ACE2)-binding inhibitors in silico.

Objective

We aimed to evaluate two active compounds, AM and GM, from Garcinia mangostana for their antivirals against SARS-CoV-2 in live virus culture systems and their cytotoxicities using standard methods. Also, we aimed to prove whether 3CLpro and ACE2 neutralization were major targets and explored whether any additional targets existed.

Methods

We tested the translation and replication efficiencies of SARS-CoV-2 in the presence of AM and GM. Initial and subgenomic translations were evaluated by immunofluorescence of SARS-CoV-2 3CLpro and N expressions at 16 h after infection. The viral genome was quantified and compared with the untreated group. We also evaluated the efficacies and cytotoxicities of AM and GM against four strains of SARS-CoV-2 (wild-type B, B.1.167.2, B.1.36.16, and B.1.1.529) in Vero E6 cells. The potential targets were evaluated using cell-based anti-attachment, time-of-drug addition, in vitro 3CLpro activities, and ACE2-binding using a surrogated viral neutralization test (sVNT). Moreover, additional targets were explored using combinatorial network-based interactions and Chemical Similarity Ensemble Approach (SEA).

Results

AM and GM reduced SARS-CoV-2 3CLpro and N expressions, suggesting that initial and subgenomic translations were globally inhibited. AM and GM inhibited all strains of SARS-CoV-2 at EC50 of 0.70-3.05 μM, in which wild-type B was the most susceptible strain (EC50 0.70-0.79 μM). AM was slightly more efficient in the variants (EC50 0.88-2.41 μM), resulting in higher selectivity indices (SI 3.65-10.05), compared to the GM (EC50 0.94-3.05 μM, SI 1.66-5.40). GM appeared to be more toxic than AM in both Vero E6 and Calu-3 cells. Cell-based anti-attachment and time-of-addition suggested that the potential molecular target could be at the post-infection. 3CLpro activity and ACE2 binding were interfered with in a dose-dependent manner but were insufficient to be a major target. Combinatorial network-based interaction and chemical similarity ensemble approach (SEA) suggested that fatty acid synthase (FASN), which was critical for SARS-CoV-2 replication, could be a target of AM and GM.

Conclusion

AM and GM inhibited SARS-CoV-2 with the highest potency at the wild-type B and the lowest at the B.1.1.529. Multiple targets were expected to integratively inhibit viral replication in cell-based system.

Biased virus transmission following sequential coinfection of Aedes aegypti with dengue and Zika viruses

BACKGROUND

Mosquito-borne arboviruses are expanding their territory and elevating their infection prevalence due to the rapid climate change, urbanization, and increased international travel and global trade. Various significant arboviruses, including the dengue virus, Zika virus, Chikungunya virus, and yellow fever virus, are all reliant on the same primary vector, Aedes aegypti. Consequently, the occurrence of arbovirus coinfection in mosquitoes is anticipated. Arbovirus coinfection in mosquitoes has two patterns: simultaneous and sequential. Numerous studies have demonstrated that simultaneous coinfection of arboviruses in mosquitoes is unlikely to exert mutual developmental influence on these viruses. However, the viruses' interplay within a mosquito after the sequential coinfection seems intricated and not well understood.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted experiments aimed at examining the phenomenon of arbovirus sequential coinfection in both mosquito cell line (C6/36) and A. aegypti, specifically focusing on dengue virus (DENV, serotype 2) and Zika virus (ZIKV). We firstly observed that DENV and ZIKV can sequentially infect mosquito C6/36 cell line, but the replication level of the subsequently infected ZIKV was significantly suppressed. Similarly, A. aegypti mosquitoes can be sequentially coinfected by these two arboviruses, regardless of the order of virus exposure. However, the replication, dissemination, and the transmission potential of the secondary virus were significantly inhibited. We preliminarily explored the underlying mechanisms, revealing that arbovirus-infected mosquitoes exhibited activated innate immunity, disrupted lipid metabolism, and enhanced RNAi pathway, leading to reduced susceptibility to the secondary arbovirus infections.

CONCLUSIONS/SIGNIFICANCE

Our findings suggest that, in contrast to simultaneous arbovirus coinfection in mosquitoes that can promote the transmission and co-circulation of these viruses, sequential coinfection appears to have limited influence on arbovirus transmission dynamics. However, it is important to note that more experimental investigations are needed to refine and expand upon this conclusion.

PI3K/AKT mediated De novo fatty acid synthesis regulates RIG-1/MDA-5-dependent type I IFN responses in BVDV-infected CD8+T cells

Bovine viral diarrhea virus (BVDV) has caused massive economic losses in the cattle business worldwide. Fatty acid synthase (FASN), a key enzyme of the fatty acid synthesis (FAS) pathway, has been shown to support virus replication. To investigate the role of fatty acids (FAs) in BVDV infection, we infected CD8+T lymphocytes obtained from healthy cattle with BVDV in vitro. During early cytopathic (CP) and noncytopathic (NCP) BVDV infection in CD8+ T cells, there is an increase in de novo lipid biosynthesis, resulting in elevated levels of free fatty acids (FFAs) and triglycerides (TG). BVDV infection promotes de novo lipid biosynthesis in a dose-dependent manner. Treatment with the FASN inhibitor C75 significantly reduces the phosphorylation of PI3K and AKT in BVDV-infected CD8+ T cells, while inhibition of PI3K with LY294002 decreases FASN expression. Both CP and NCP BVDV strains promote de novo fatty acid synthesis by activating the PI3K/AKT pathway. Further investigation shows that pharmacological inhibitors targeting FASN and PI3K concurrently reduce FFAs, TG levels, and ATP production, effectively inhibiting BVDV replication. Conversely, the in vitro supplementation of oleic acid (OA) to replace fatty acids successfully restored BVDV replication, underscoring the impact of abnormal de novo fatty acid metabolism on BVDV replication. Intriguingly, during BVDV infection of CD8+T cells, the use of FASN inhibitors prompted the production of IFN-α and IFN-β, as well as the expression of interferon-stimulated genes (ISGs). Moreover, FASN inhibitors induce TBK-1 phosphorylation through the activation of RIG-1 and MDA-5, subsequently activating IRF-3 and ultimately enhancing the IFN-1 response. In conclusion, our study demonstrates that BVDV infection activates the PI3K/AKT pathway to boost de novo fatty acid synthesis, and inhibition of FASN suppresses BVDV replication by activating the RIG-1/MDA-5-dependent IFN response.

Research Advances on the Role of Lipids in the Life Cycle of Human Coronaviruses

Coronaviruses (CoVs) are emerging pathogens with a significant potential to cause life-threatening harm to human health. Since the beginning of the 21st century, three highly pathogenic and transmissible human CoVs have emerged, triggering epidemics and posing major threats to global public health. CoVs are enveloped viruses encased in a lipid bilayer. As fundamental components of cells, lipids can play an integral role in many physiological processes, which have been reported to play important roles in the life cycle of CoVs, including viral entry, uncoating, replication, assembly, and release. Therefore, research on the role of lipids in the CoV life cycle can provide a basis for a better understanding of the infection mechanism of CoVs and provide lipid targets for the development of new antiviral strategies. In this review, research advances on the role of lipids in different stages of viral infection and the possible targets of lipids that interfere with the viral life cycle are discussed.

Wolbachia interferes with Zika virus replication by hijacking cholesterol metabolism in mosquito cells

IMPORTANCE

Arthropod-borne viruses are emerging pathogens that are spread widely by mosquitos. Zika virus is an arbovirus that can infect humans and be transmitted from an infected mother to the fetus, potentially leading to microcephaly in infants. One promising strategy to prevent disease caused by arboviruses is to target the insect vector population. Recent field studies have shown that mosquito populations infected with Wolbachia bacteria suppress arbovirus replication and transmission. Here, we describe how intracellular bacteria redirect resources within their host cells and suppress Zika virus replication at the cellular level. Understanding the mechanism behind Wolbachia-induced interference of arbovirus replication could help advance strategies to control arbovirus pathogens in insect vectors and human populations.

Flying under the radar - impact and factors influencing asymptomatic DENV infections

The clinical outcome of DENV and other Flaviviruses infections represents a spectrum of severity that ranges from mild manifestations to severe disease, which can ultimately lead to death. Nonetheless, most of these infections result in an asymptomatic outcome that may play an important role in the persistent circulation of these viruses. Also, although little is known about the mechanisms that lead to these asymptomatic infections, they are likely the result of a complex interplay between viral and host factors. Specific characteristics of the infecting viral strain, such as its replicating efficiency, coupled with host factors, like gene expression of key molecules involved in the immune response or in the protection against disease, are among crucial factors to study. This review revisits recent data on factors that may contribute to the asymptomatic outcome of the world's widespread DENV, highlighting the importance of silent infections in the transmission of this pathogen and the immune status of the host.

White spot syndrome virus (WSSV) modulates lipid metabolism in white shrimp

In addition to the Warburg effect, which increases the availability of energy and biosynthetic building blocks in WSSV-infected shrimp, WSSV also induces both lipolysis at the viral genome replication stage (12 hpi) to provide material and energy for the virus replication, and lipogenesis at the viral late stage (24 hpi) to complete virus morphogenesis by supplying particular species of long-chain fatty acids (LCFAs). Here, we further show that WSSV causes a reduction in lipid droplets (LDs) in hemocytes at the viral genome replication stage, and an increase in LDs in the nuclei of WSSV-infected hemocytes at the viral late stage. In the hepatopancreas, lipolysis is triggered by WSSV infection, and this leads to fatty acids being released into the hemolymph. β-oxidation inhibition experiment reveals that the fatty acids generated by WSSV-induced lipolysis can be diverted into β-oxidation for energy production. At the viral late stage, WSSV infection leads to lipogenesis in both the stomach and hepatopancreas, suggesting that fatty acids are in high demand at this stage for virion morphogenesis. Our results demonstrate that WSSV modulates lipid metabolism specifically at different stages to facilitate its replication.

Investigation of the activity of baicalein towards Zika virus

BACKGROUND

Zika virus (ZIKV) is a mosquito transmitted virus spread primarily by Aedes species mosquitoes that can cause disease in humans, particularly when infection occurs in pregnancy where the virus can have a significant impact on the developing fetus. Despite this, there remains no prophylactic agent or therapeutic treatment for infection. Baicalein is a trihydroxyflavone, that is found in some traditional medicines commonly used in Asia, and has been shown to have several activities including antiviral properties. Importantly, studies have shown baicalein to be safe and well tolerated in humans, increasing its potential utilization.

METHODS

This study sought to determine the anti-ZIKV activity of baicalein using a human cell line (A549). Cytotoxicity of baicalein was determined by the MTT assay, and the effect on ZIKV infection determined by treating A549 cells with baicalien at different time points in the infection process. Parameters including level of infection, virus production, viral protein expression and genome copy number were assessed by flow cytometry, plaque assay, western blot and quantitative RT-PCR, respectively.

RESULTS

The results showed that baicalein had a half-maximal cytotoxic concentration (CC₅₀) of > 800 µM, and a half-maximal effective concentration (EC₅₀) of 124.88 µM. Time-of-addition analysis showed that baicalein had an inhibitory effect on ZIKV infection at the adsorption and post-adsorption stages. Moreover, baicalein also exerted a significant viral inactivation activity on ZIKV (as well as on dengue virus and Japanese encephalitis virus) virions.

CONCLUSION

Baicalein has now been shown to possess anti-ZIKV activity in a human cell line.

The buzz in the field: the interaction between viruses, mosquitoes, and metabolism

Among many medically important pathogens, arboviruses like dengue, Zika and chikungunya cause severe health and economic burdens especially in developing countries. These viruses are primarily vectored by mosquitoes. Having surmounted geographical barriers and threat of control strategies, these vectors continue to conquer many areas of the globe exposing more than half of the world's population to these viruses. Unfortunately, no medical interventions have been capable so far to produce successful vaccines or antivirals against many of these viruses. Thus, vector control remains the fundamental strategy to prevent disease transmission. The long-established understanding regarding the replication of these viruses is that they reshape both human and mosquito host cellular membranes upon infection for their replicative benefit. This leads to or is a result of significant alterations in lipid metabolism. Metabolism involves complex chemical reactions in the body that are essential for general physiological functions and survival of an organism. Finely tuned metabolic homeostases are maintained in healthy organisms. However, a simple stimulus like a viral infection can alter this homeostatic landscape driving considerable phenotypic change. Better comprehension of these mechanisms can serve as innovative control strategies against these vectors and viruses. Here, we review the metabolic basis of fundamental mosquito biology and virus-vector interactions. The cited work provides compelling evidence that targeting metabolism can be a paradigm shift and provide potent tools for vector control as well as tools to answer many unresolved questions and gaps in the field of arbovirology.

Acetyl-CoA Carboxylase (ACC) Inhibitor, CP640186, Effectively Inhibited Dengue Virus (DENV) Infection via Regulating ACC Phosphorylation

Dengue fever is the most common mosquito-borne viral disease and is caused by the dengue virus (DENV). There is still a lack of efficient drugs against DENV infection, so it is urgent to develop new inhibitors for future clinical use. Our previous research indicated the role of VEGFR2/AMPK in regulating cellular metabolism during DENV infection, while acetyl-CoA carboxylase (ACC) is located downstream of AMPK and plays a crucial role in mediating cellular lipid synthesis; therefore, we speculated that an ACC inhibitor could serve as an antiviral agent against DENV. Luckily, we found that CP640186, a reported noncompetitive ACC inhibitor, significantly inhibited DENV proliferation, and CP640186 clearly reduced DENV2 proliferation at an early stage with an EC₅₀ of 0.50 μM. A mechanism study indicated that CP640186 inhibited ACC activation and destroyed the cellular lipid environment for viral proliferation. In the DENV2 infection mice model, oral CP640186 administration (10 mg/kg/day) significantly improved the mice survival rate after DENV2 infection. In summary, our research suggests that lipid synthesis plays an important role during DENV2 proliferation and indicates that CP640186 is a promising drug candidate against DNEV2 in the future.

Metabolic syndrome and aberrant immune responses to viral infection and vaccination: Insights from small animal models

This review outlines the propensity for metabolic syndrome (MetS) to induce elevated disease severity, higher mortality rates post-infection, and poor vaccination outcomes for viral pathogens. MetS is a cluster of conditions including high blood glucose, an increase in circulating low-density lipoproteins and triglycerides, abdominal obesity, and elevated blood pressure which often overlap in their occurrence. MetS diagnoses are on the rise, as reported cases have increased by greater than 35% since 1988, resulting in one-third of United States adults currently diagnosed as MetS patients. In the aftermath of the 2009 H1N1 pandemic, a link between MetS and disease severity was established. Since then, numerous studies have been conducted to illuminate the impact of MetS on enhancing virally induced morbidity and dysregulation of the host immune response. These correlative studies have emphasized the need for elucidating the mechanisms by which these alterations occur, and animal studies conducted as early as the 1940s have linked the conditions associated with MetS with enhanced viral disease severity and poor vaccine outcomes. In this review, we provide an overview of the importance of considering overall metabolic health in terms of cholesterolemia, glycemia, triglyceridemia, insulin and other metabolic molecules, along with blood pressure levels and obesity when studying the impact of metabolism-related malignancies on immune function. We highlight the novel insights that small animal models have provided for MetS-associated immune dysfunction following viral infection. Such animal models of aberrant metabolism have paved the way for our current understanding of MetS and its impact on viral disease severity, dysregulated immune responses to viral pathogens, poor vaccination outcomes, and contributions to the emergence of viral variants.

Cell Type Variability in the Incorporation of Lipids in the Dengue Virus Virion

A lipid bilayer produced from the host membrane makes up around 20% of the weight of the dengue virus (DENV) virion and is crucial for virus entry. Despite its significance, the virion's lipid composition is still poorly understood. In tandem with lipid profiles of the cells utilised to generate the virions, this work determined a partial lipid profile of DENV virions derived from two cell lines (C6/36 and LLC-MK₂). The results showed distinctive profiles between the two cell types. In the mammalian LLC-MK₂ cells, 30.8% (73/237 identified lipid species; 31 upregulated, 42 downregulated) of lipid species were altered in response to infection, whilst in insect C6/36 cells only 12.0% (25/208; 19 upregulated, 6 downregulated) of lipid species showed alterations in response to infection. For virions from LLC-MK₂ cells, 14 lipids were detected specifically in virions with a further seven lipids being enriched (over mock controls). For virions from C6/36 cells, 43 lipids were detected that were not seen in mock preparations, with a further 16 being specifically enriched (over mock control). These results provide the first lipid description of DENV virions produced in mammalian and mosquito cells, as well as the lipid changes in the corresponding infected cells.

Diverse susceptibilities and responses of human and rodent cells to orthohantavirus infection reveal different levels of cellular restriction

Orthohantaviruses are rodent-borne emerging viruses that may cause severe diseases in humans but no apparent pathology in their small mammal reservoirs. However, the mechanisms leading to tolerance or pathogenicity in humans and persistence in rodent reservoirs are poorly understood, as is the manner in which they spread within and between organisms. Here, we used a range of cellular and molecular approaches to investigate the interactions of three different orthohantaviruses-Puumala virus (PUUV), responsible for a mild to moderate form of hemorrhagic fever with renal syndrome in humans, Tula virus (TULV) with low pathogenicity, and non-pathogenic Prospect Hill virus (PHV)-with human and rodent host cell lines. Besides the fact that cell susceptibility to virus infection was shown to depend on the cell type and virus strain, the three orthohantaviruses were able to infect Vero E6 and HuH7 human cells, but only the former secreted infectious particles. In cells derived from PUUV reservoir, the bank vole (Myodes glareolus), PUUV achieved a complete viral cycle, while TULV did not enter the cells and PHV infected them but did not produce infectious particles, reflecting differences in host specificity. A search for mature virions by electron microscopy (EM) revealed that TULV assembly occurred in part at the plasma membrane, whereas PHV particles were trapped in autophagic vacuoles in cells of the heterologous rodent host. We described differential interactions of orthohantaviruses with cellular factors, as supported by the cellular distribution of viral nucleocapsid protein with cell compartments, and proteomics identification of cellular partners. Our results also showed that interferon (IFN) dependent gene expression was regulated in a cell and virus species dependent manner. Overall, our study highlighted the complexity of the host-virus relationship and demonstrated that orthohantaviruses are restricted at different levels of the viral cycle. In addition, the study opens new avenues to further investigate how these viruses differ in their interactions with cells to evade innate immunity and how it depends on tissue type and host species.

Expression of fatty acid synthase genes and their role in development and arboviral infection of Aedes aegypti

BACKGROUND

Fatty acids are the building blocks of complex lipids essential for living organisms. In mosquitoes, fatty acids are involved in cell membrane production, energy conservation and expenditure, innate immunity, development and reproduction. Fatty acids are synthesized by a multifunctional enzyme complex called fatty acid synthase (FAS). Several paralogues of FAS were found in the Aedes aegypti mosquito. However, the molecular characteristics and expression of some of these paralogues have not been investigated.

METHODS

Genome assemblies of Ae. aegypti were analyzed, and orthologues of human FAS was identified. Phylogenetic analysis and in silico molecular characterization were performed to identify the functional domains of the Ae. aegypti FAS (AaFAS). Quantitative analysis and loss-of-function experiments were performed to determine the significance of different AaFAS transcripts in various stages of development, expression following different diets and the impact of AaFAS on dengue virus, serotype 2 (DENV2) infection and transmission.

RESULTS

We identified seven putative FAS genes in the Ae. aegypti genome assembly, based on nucleotide similarity to the FAS proteins (tBLASTn) of humans, other mosquitoes and invertebrates. Bioinformatics and molecular analyses suggested that only five of the AaFAS genes produce mRNA and therefore represent complete gene models. Expression levels of AaFAS varied among developmental stages and between male and female Ae. aegypti. Quantitative analyses revealed that expression of AaFAS1, the putative orthologue of the human FAS, was highest in adult females. Transient knockdown (KD) of AaFAS1 did not induce a complete compensation by other AaFAS genes but limited DENV2 infection of Aag2 cells in culture and the midgut of the mosquito.

CONCLUSION

AaFAS1 is the predominant AaFAS in adult mosquitoes. It has the highest amino acid similarity to human FAS and contains all enzymatic domains typical of human FAS. AaFAS1 also facilitated DENV2 replication in both cell culture and in mosquito midguts. Our data suggest that AaFAS1 may play a role in transmission of dengue viruses and could represent a target for intervention strategies.

Coronavirus disease 2019 (COVID-19) update: From metabolic reprogramming to immunometabolism

The field of immunometabolism investigates and describes the effects of metabolic rewiring in immune cells throughout activation and the fates of these cells. Recently, it has been appreciated that immunometabolism plays an essential role in the progression of viral infections, cancer, and autoimmune diseases. Regarding COVID‐19, the aberrant immune response underlying the progression of diseases establishes two major respiratory pathologies, including acute respiratory distress syndrome (ARDS) or pneumonia‐induced acute lung injury (ALI). Both innate and adaptive immunity (T cell‐based) were impaired in the course of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection. Current findings have deciphered that macrophages (innate immune cells) are involved in the inflammatory response seen in COVID‐19. It has been demonstrated that immune system cells can change metabolic reprogramming in some conditions, including autoimmune diseases, cancer, and infectious disease, including COVID‐19. The growing findings on metabolic reprogramming in COVID‐19 allow an exploration of metabolites with immunomodulatory properties as future therapies to combat this hyperinflammatory response. The elucidation of the exact role and mechanism underlying this metabolic reprograming in immune cells could help apply more precise approaches to initial diagnosis, prognosis, and in‐hospital therapy. This report discusses the latest findings from COVID‐19 on host metabolic reprogramming and immunometabolic responses.

The Evolutionary Dance between Innate Host Antiviral Pathways and SARS-CoV-2

Compared to what we knew at the start of the SARS-CoV-2 global pandemic, our understanding of the interplay between the interferon signaling pathway and SARS-CoV-2 infection has dramatically increased. Innate antiviral strategies range from the direct inhibition of viral components to reprograming the host’s own metabolic pathways to block viral infection. SARS-CoV-2 has also evolved to exploit diverse tactics to overcome immune barriers and successfully infect host cells. Herein, we review the current knowledge of the innate immune signaling pathways triggered by SARS-CoV-2 with a focus on the type I interferon response, as well as the mechanisms by which SARS-CoV-2 impairs those defenses.

Suppressing fatty acid synthase by type I interferon and chemical inhibitors as a broad spectrum anti-viral strategy against SARS-CoV-2

SARS-CoV-2 is an emerging viral pathogen and a major global public health challenge since December of 2019, with limited effective treatments throughout the pandemic. As part of the innate immune response to viral infection, type I interferons (IFN-I) trigger a signaling cascade that culminates in the activation of hundreds of genes, known as interferon stimulated genes (ISGs), that collectively foster an antiviral state. We report here the identification of a group of type I interferon suppressed genes, including fatty acid synthase (FASN), which are involved in lipid metabolism. Overexpression of FASN or the addition of its downstream product, palmitate, increased viral infection while knockout or knockdown of FASN reduced infection. More importantly, pharmacological inhibitors of FASN effectively blocked infections with a broad range of viruses, including SARS-CoV-2 and its variants of concern. Thus, our studies not only suggest that downregulation of metabolic genes may present an antiviral strategy by type I interferon, but they also introduce the potential for FASN inhibitors to have a therapeutic application in combating emerging infectious diseases such as COVID-19.

Hallmarks of Metabolic Reprogramming and Their Role in Viral Pathogenesis

Metabolic reprogramming is a hallmark of cancer and has proven to be critical in viral infections. Metabolic reprogramming provides the cell with energy and biomass for large-scale biosynthesis. Based on studies of the cellular changes that contribute to metabolic reprogramming, seven main hallmarks can be identified: (1) increased glycolysis and lactic acid, (2) increased glutaminolysis, (3) increased pentose phosphate pathway, (4) mitochondrial changes, (5) increased lipid metabolism, (6) changes in amino acid metabolism, and (7) changes in other biosynthetic and bioenergetic pathways. Viruses depend on metabolic reprogramming to increase biomass to fuel viral genome replication and production of new virions. Viruses take advantage of the non-metabolic effects of metabolic reprogramming, creating an anti-apoptotic environment and evading the immune system. Other non-metabolic effects can negatively affect cellular function. Understanding the role metabolic reprogramming plays in viral pathogenesis may provide better therapeutic targets for antivirals.

Elevation in sphingolipid upon SARS-CoV-2 infection: possible implications for COVID-19 pathology

SARS-CoV-2 infection alters the levels of sphingolipids early post infection. This phenomenon is reflected by increased levels of sphingolipids, including gangliosides, in infected cells, as well as in serum in a SARS-CoV-2 murine model.

Understanding pathways that might impact coronavirus disease 2019 (COVID-19) manifestations and disease outcomes is necessary for better disease management and for therapeutic development. Here, we analyzed alterations in sphingolipid (SL) levels upon infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2 infection induced elevation of SL levels in both cells and sera of infected mice. A significant increase in glycosphingolipid levels was induced early post SARS-CoV-2 infection, which was essential for viral replication. This elevation could be reversed by treatment with glucosylceramide synthase inhibitors. Levels of sphinganine, sphingosine, GA1, and GM3 were significantly increased in both cells and the murine model upon SARS-CoV-2 infection. The potential involvement of SLs in COVID-19 pathology is discussed.

A bioorthogonal chemical reporter for fatty acid synthase-dependent protein acylation

Mammalian cells acquire fatty acids (FAs) from dietary sources or via de novo palmitate production by fatty acid synthase (FASN). Although most cells express FASN at low levels, it is upregulated in cancers of the breast, prostate, and liver, among others, and is required during the replication of many viruses, such as dengue virus, hepatitis C, HIV-1, hepatitis B, and severe acute respiratory syndrome coronavirus 2, among others. The precise role of FASN in disease pathogenesis is poorly understood, and whether de novo FA synthesis contributes to host or viral protein acylation has been traditionally difficult to study. Here, we describe a cell-permeable and click chemistry-compatible alkynyl acetate analog (alkynyl acetic acid or 5-hexynoic acid [Alk-4]) that functions as a reporter of FASN-dependent protein acylation. In an FASN-dependent manner, Alk-4 selectively labels the cellular protein interferon-induced transmembrane protein 3 at its known palmitoylation sites, a process that is essential for the antiviral activity of the protein, and the HIV-1 matrix protein at its known myristoylation site, a process that is required for membrane targeting and particle assembly. Alk-4 metabolic labeling also enabled biotin-based purification and identification of more than 200 FASN-dependent acylated cellular proteins. Thus, Alk-4 is a useful bioorthogonal tool to selectively probe FASN-mediated protein acylation in normal and diseased states.

Berberine Inhibits Dengue Virus through Dual Mechanisms

Mosquito transmitted viruses, particularly those of the genus Flavivirus, are a significant healthcare burden worldwide, especially in tropical and sub-tropical areas. However, effective medicines for these viral infections remains lacking. Berberine (BBR) is an alkaloid found in some plants used in traditional medicines in Southeast Asia and elsewhere, and BBR has been shown to possess anti-viral activities. During a screen for potential application to mosquito transmitted viruses, BBR was shown to have virucidal activity against dengue virus (DENV; IC₅₀ 42.87 µM) as well as against Zika virus (IC₅₀ 11.42 µM) and chikungunya virus (IC₅₀ 14.21 µM). BBR was shown to have cellular effects that lead to an increase in cellular DENV E protein without a concomitant effect on DENV nonstructural proteins, suggesting an effect on viral particle formation or egress. While BBR was shown to have an effect of ERK1/2 activation this did not result in defects in viral egress mechanisms. The primary effect of BBR on viral production was likely to be through BBR acting through AMPK activation and disruption of lipid metabolism. Combined these results suggest that BBR has a dual effect on DENV infection, and BBR may have the potential for development as an anti-DENV antiviral.

Rickettsia conorii survival in THP-1 macrophages involves host lipid droplet alterations and active rickettsial protein production

Rickettsia conorii is a Gram-negative, cytosolic intracellular bacterium that has classically been investigated in terms of endothelial cell infection. However, R. conorii and other human pathogenic Rickettsia species have evolved mechanisms to grow in various cell types, including macrophages, during mammalian infection. During infection of these phagocytes, R. conorii shifts the host cell's overall metabolism towards an anti-inflammatory M2 response, metabolically defined by an increase in host lipid metabolism and oxidative phosphorylation. Lipid metabolism has more recently been identified as a key regulator of host homeostasis through modulation of immune signalling and metabolism. Intracellular pathogens have adapted mechanisms of hijacking host metabolic pathways including host lipid catabolic pathways for various functions required for growth and survival. In the present study, we hypothesised that alterations of host lipid droplets initiated by lipid catabolic pathways during R. conorii infection is important for bacterial survival in macrophages. Herein, we determined that host lipid droplet modulation is initiated early during R. conorii infection, and these alterations rely on active bacteria and lipid catabolic pathways. We also find that these lipid catabolic pathways are essential for efficient bacterial survival. Unlike the mechanisms used by other intracellular pathogens, the catabolism of lipid droplets induced by R. conorii infection is independent of upstream host peroxisome proliferator-activated receptor-alpha (PPARα) signalling. Inhibition of PPARɣ signalling and lipid droplet accumulation in host cells cause a significant decrease in R. conorii survival suggesting a negative correlation with lipid droplet production and R. conorii survival. Together, these results strongly suggest that the modulation of lipid droplets in macrophage cells infected by R. conorii is an important and underappreciated aspect of the infection process. TAKE AWAYS: Host lipid droplets are differentially altered in early and replicative stages of THP-1 macrophage infection with R. conorii. Lipid droplet alterations are initiated in a bacterial-dependent manner and do not require host peroxisome proliferator-activated receptors α or ɣ activation. Pharmacological inhibition of host lipid catabolic processes during R. conorii infection indicates a requirement of lipid catabolism for bacterial survival and initiation of lipid droplet modulation. A significant increase in host lipid droplets during infection has a negative impact on R. conorii survival in THP-1 macrophages.

Inhibitors of VPS34 and fatty-acid metabolism suppress SARS-CoV-2 replication

Coronaviruses rely on host membranes for entry, establishment of replication centers, and egress. Compounds targeting cellular membrane biology and lipid biosynthetic pathways have previously shown promise as antivirals and are actively being pursued as treatments for other conditions. Here, we test small molecule inhibitors that target the PI3 kinase VPS34 or fatty acid metabolism for anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) activity. Our studies determine that compounds targeting VPS34 are potent SARS-CoV-2 inhibitors. Mechanistic studies with compounds targeting multiple steps up- and downstream of fatty acid synthase (FASN) identify the importance of triacylglycerol production and protein palmitoylation as requirements for efficient viral RNA synthesis and infectious virus production. Further, FASN knockout results in significantly impaired SARS-CoV-2 replication that can be rescued with fatty acid supplementation. Together, these studies clarify roles for VPS34 and fatty acid metabolism in SARS-CoV-2 replication and identify promising avenues for the development of countermeasures against SARS-CoV-2.

Metabolic reprogramming and immune regulation in viral diseases

The recent outbreak and transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) worldwide and the ensuing coronavirus disease 2019 (COVID-19) pandemic has left us scrambling for ways to contain the disease and develop vaccines that are safe and effective. Equally important, understanding the impact of the virus on the host system in convalescent patients, healthy otherwise or with co-morbidities, is expected to aid in developing effective strategies in the management of patients afflicted with the disease. Viruses possess the uncanny ability to redirect host metabolism to serve their needs and also limit host immune response to ensure their survival. An ever-increasingly powerful approach uses metabolomics to uncover diverse molecular signatures that influence a wide array of host signalling networks in different viral infections. This would also help integrate experimental findings from individual studies to yield robust evidence. In addition, unravelling the molecular mechanisms harnessed by both viruses and tumours in their host metabolism will help broaden the repertoire of therapeutic tools available to combat viral disease.

Antiviral Compounds for Blocking Arboviral Transmission in Mosquitoes

Mosquito-borne arthropod-borne viruses (arboviruses) such as the dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) are important human pathogens that are responsible for significant global morbidity and mortality. The recent emergence and re-emergence of mosquito-borne viral diseases (MBVDs) highlight the urgent need for safe and effective vaccines, therapeutics, and vector-control approaches to prevent MBVD outbreaks. In nature, arboviruses circulate between vertebrate hosts and arthropod vectors; therefore, disrupting the virus lifecycle in mosquitoes is a major approach for combating MBVDs. Several strategies were proposed to render mosquitoes that are refractory to arboviral infection, for example, those involving the generation of genetically modified mosquitoes or infection with the symbiotic bacterium Wolbachia. Due to the recent development of high-throughput screening methods, an increasing number of drugs with inhibitory effects on mosquito-borne arboviruses in mammalian cells were identified. These antivirals are useful resources that can impede the circulation of arboviruses between arthropods and humans by either rendering viruses more vulnerable in humans or suppressing viral infection by reducing the expression of host factors in mosquitoes. In this review, we summarize recent advances in small-molecule antiarboviral drugs in mammalian and mosquito cells, and discuss how to use these antivirals to block the transmission of MBVDs.

The Fatty Acid Lipid Metabolism Nexus in COVID-19

Enteric symptomology seen in early-stage severe acute respiratory syndrome (SARS)-2003 and COVID-19 is evidence of virus replication occurring in the intestine, liver and pancreas. Aberrant lipid metabolism in morbidly obese individuals adversely affects the COVID-19 immune response and increases disease severity. Such observations are in line with the importance of lipid metabolism in COVID-19, and point to the gut as a site for intervention as well as a therapeutic target in treating the disease. Formation of complex lipid membranes and palmitoylation of coronavirus proteins are essential during viral replication and assembly. Inhibition of fatty acid synthase (FASN) and restoration of lipid catabolism by activation of AMP-activated protein kinase (AMPK) impede replication of coronaviruses closely related to SARS-coronavirus-2 (CoV-2). In vitro findings and clinical data reveal that the FASN inhibitor, orlistat, and the AMPK activator, metformin, may inhibit coronavirus replication and reduce systemic inflammation to restore immune homeostasis. Such observations, along with the known mechanisms of action for these types of drugs, suggest that targeting fatty acid lipid metabolism could directly inhibit virus replication while positively impacting the patient's response to COVID-19.

Temperature modulates immune gene expression in mosquitoes during arbovirus infection

The principal vector of dengue, Zika and chikungunya viruses is the mosquito Aedes aegypti, with its ability to transmit pathogens influenced by ambient temperature. We use chikungunya virus (CHIKV) to understand how the mosquito transcriptome responds to arbovirus infection at different ambient temperatures. We exposed CHIKV-infected mosquitoes to 18, 28 and 32°C, and found that higher temperature correlated with higher virus levels, particularly at 3 days post infection, but lower temperature resulted in reduced virus levels. RNAseq analysis indicated significantly altered gene expression levels in CHIKV infection. The highest number of significantly differentially expressed genes was observed at 28°C, with a more muted effect at the other temperatures. At the higher temperature, the expression of many classical immune genes, including Dicer-2, was not substantially altered in response to CHIKV. The upregulation of Toll, IMD and JAK-STAT pathways was only observed at 28°C. Functional annotations suggested that genes in immune response and metabolic pathways related to energy supply and DNA replication were involved in temperature-dependent changes. Time post infection also led to substantially different gene expression profiles, and this varied with temperature. In conclusion, temperature significantly modulates mosquito gene expression in response to infection, potentially leading to impairment of immune defences at higher temperatures.

Broad-Spectrum Flavivirus Inhibitors: a Medicinal Chemistry Point of View

Infections by flaviviruses, such as Dengue, West Nile, Yellow Fever and Zika viruses, represent a growing risk for global health. There are vaccines only for few flaviviruses while no effective treatments are available. Flaviviruses share epidemiological, structural, and ecologic features and often different viruses can co-infect the same host. Therefore, the identification of broad-spectrum inhibitors is highly desirable either for known flaviviruses or for viruses that likely will emerge in the future. Strategies targeting both virus and host factors have been pursued to identify broad-spectrum antiflaviviral agents. In this review, we describe the most promising and best characterized targets and their relative broad-spectrum inhibitors, identified by drug repurposing/libraries screenings and by focused medicinal chemistry campaigns. Finally, we discuss about future strategies to identify new broad-spectrum antiflavivirus agents.

Modulation of acyl-carnitines, the broad mechanism behind Wolbachia-mediated inhibition of medically important flaviviruses in Aedes aegypti

Wolbachia-infected mosquitoes are refractory to flavivirus infections, but the role of lipids in Wolbachia-mediated virus blocking remains to be elucidated. Here, we use liquid chromatography mass spectrometry to provide a comprehensive picture of the lipidome of Aedes aegypti (Aag2) cells infected with Wolbachia only, either dengue or Zika virus only, and Wolbachia-infected Aag2 cells superinfected with either dengue or Zika virus. This approach identifies a class of lipids, acyl-carnitines, as being down-regulated during Wolbachia infection. Furthermore, treatment with an acyl-carnitine inhibitor assigns a crucial role for acyl-carnitines in the replication of dengue and Zika viruses. In contrast, depletion of acyl-carnitines increases Wolbachia density while addition of commercially available acyl-carnitines impairs Wolbachia production. Finally, we show an increase in flavivirus infection of Wolbachia-infected cells with the addition of acyl-carnitines. This study uncovers a previously unknown role for acyl-carnitines in this tripartite interaction that suggests an important and broad mechanism that underpins Wolbachia-mediated pathogen blocking.

Inhibitors of VPS34 and lipid metabolism suppress SARS-CoV-2 replication

Therapeutics targeting replication of SARS coronavirus 2 (SARS-CoV-2) are urgently needed. Coronaviruses rely on host membranes for entry, establishment of replication centers and egress. Compounds targeting cellular membrane biology and lipid biosynthetic pathways have previously shown promise as antivirals and are actively being pursued as treatments for other conditions. Here, we tested small molecule inhibitors that target membrane dynamics or lipid metabolism. Included were inhibitors of the PI3 kinase VPS34, which functions in autophagy, endocytosis and other processes; Orlistat, an inhibitor of lipases and fatty acid synthetase, is approved by the FDA as a treatment for obesity; and Triacsin C which inhibits long chain fatty acyl-CoA synthetases. VPS34 inhibitors, Orlistat and Triacsin C inhibited virus growth in Vero E6 cells and in the human airway epithelial cell line Calu-3, acting at a post-entry step in the virus replication cycle. Of these the VPS34 inhibitors exhibit the most potent activity.

Metabolic profiles of fish nodavirus infection in vitro: RGNNV induced and exploited cellular fatty acid synthesis for virus infection

Red-spotted grouper nervous necrosis virus (RGNNV), the causative agent of viral nervous necrosis disease, has caused high mortality and heavy economic losses in marine aquaculture worldwide. However, changes in host cell metabolism during RGNNV infection remain largely unknown. Here, the global metabolic profiling during RGNNV infection and the roles of cellular fatty acid synthesis in RGNNV infection were investigated. As the infection progressed, 71 intracellular metabolites were significantly altered in RGNNV-infected cells compared with mock-infected cells. The levels of metabolites involved in amino acid biosynthesis and metabolism were significantly decreased, whereas those that correlated with fatty acid synthesis were significantly up-regulated during RGNNV infection. Among them, tryptophan and oleic acid were assessed as the most crucial biomarkers for RGNNV infection. In addition, RGNNV infection induced the formation of lipid droplets and re-localization of fatty acid synthase (FASN), indicating that RGNNV induced and required lipogenesis for viral infection. The exogenous addition of palmitic acid (PA) enhanced RGNNV infection, and the inhibition of FASN and acetyl-CoA carboxylase (ACC) significantly decreased RGNNV replication. Additionally, not only inhibition of palmitoylation and phospholipid synthesis, but also destruction of fatty acid β-oxidation significantly decreased viral replication. These data suggest that cellular fatty acid synthesis and mitochondrial β-oxidation are essential for RGNNV to complete the viral life cycle. Thus, it has been demonstrated for the first time that RGNNV infection in vitro overtook host cell metabolism and, in that process, cellular fatty acid synthesis was an essential component for RGNNV replication.

Small Molecule Inhibitor of ATPase Activity of HSP70 as a Broad-Spectrum Inhibitor against Flavivirus Infections

Flaviviruses including Zika virus, Dengue virus, Japanese Encephalitis virus, and Yellow Fever virus cause heavy burdens to public health around the world. No specific antiviral drug is available in the clinic against these flavivirus infections. Heat-shock protein 70 (HSP70) has recently been proven to be a promising antiviral target against Zika virus and Dengue virus. Here, we report that Apoptozole, a small molecule inhibitor of ATPase activity of HSP70, has broad-spectrum anti-flavivirus potential. The mode of action analysis revealed that Apoptozole acted at the post-entry step. Transcriptome analysis revealed that genes related to cholesterol metabolism, fatty acid synthesis, and innate immunity were differentially expressed after treatment with Apoptozole. In vivo data suggested Apoptozole exerted protection effects against Zika virus (ZIKV) infection in a mouse model by enhancing the innate immune response, which suggested a novel anti-ZIKV mechanism of HSP70 inhibitors.

Evaluation of the antiviral activity of orlistat (tetrahydrolipstatin) against dengue virus, Japanese encephalitis virus, Zika virus and chikungunya virus

Many mosquito transmitted viruses of the genera Alphavirus and Flavivirus are human pathogens of significant concern, and there is currently no specific antiviral for any member of these two genera. This study sought to investigate the broad utility of orlistat (tetrahydrolipstatin) in reducing virus infection for several mosquito borne viruses including flaviviruses (dengue virus (DENV; nine isolates analyzed), Japanese encephalitis virus (JEV; one isolate analyzed) and Zika virus (ZIKV; 2 isolates analyzed)) as well as an alphavirus (chikungunya virus; CHIKV; 2 isolates analyzed). Three different treatment regimens were evaluated, namely pre-treatment (only), post-treatment (only) and pre- and post-treatment, and three factors were evaluated, namely level of infection, virus titer and genome copy number. Results showed that all three treatment modalities were able to significantly reduce virus titer for all viruses investigated, with the exception of three isolates of DENV in the pre-treatment only regimen. Pre- and post-treatment was more effective in reducing the level of infection and genome copy number of all viruses investigated than either pre-treatment or post-treatment alone. Collectively, these results suggest orlistat has potential as a broad-spectrum agent against multiple mosquito transmitted viruses.

Labyrinthopeptins Exert Broad-Spectrum Antiviral Activity through Lipid-Binding-Mediated Virolysis

To counteract the serious health threat posed by known and novel viral pathogens, drugs that target a variety of viruses through a common mechanism have attracted recent attention due to their potential in treating (re)emerging infections, for which direct-acting antivirals are not available. We found that labyrinthopeptins A1 and A2, the prototype congeners of carbacyclic lanthipeptides, inhibit the proliferation of diverse enveloped viruses, including dengue virus, Zika virus, West Nile virus, hepatitis C virus, chikungunya virus, Kaposi's sarcoma-associated herpesvirus, cytomegalovirus, and herpes simplex virus, in the low micromolar to nanomolar range. Mechanistic studies on viral particles revealed that labyrinthopeptins induce a virolytic effect through binding to the viral membrane lipid phosphatidylethanolamine (PE). These effects are enhanced by a combined equimolar application of both labyrinthopeptins, and a clear synergism was observed across a concentration range corresponding to 10% to 90% inhibitory concentrations of the compounds. Time-resolved experiments with large unilamellar vesicles (LUVs) reveal that membrane lipid raft compositions (phosphatidylcholine [PC]/PE/cholesterol/sphingomyelin at 17:10:33:40) are particularly sensitive to labyrinthopeptins in comparison to PC/PE (90:10) LUVs, even though the overall PE amount remains constant. Labyrinthopeptins exhibited low cytotoxicity and had favorable pharmacokinetic properties in mice (half-life [t _1/2] = 10.0 h), which designates them promising antiviral compounds acting by an unusual viral lipid targeting mechanism.IMPORTANCE For many viral infections, current treatment options are insufficient. Because the development of each antiviral drug is time-consuming and expensive, the prospect of finding broad-spectrum antivirals that can fight multiple, diverse viruses-well-known viruses as well as (re)emerging species-has gained attention, especially for the treatment of viral coinfections. While most known broad-spectrum agents address processes in the host cell, we found that targeting lipids of the free virus outside the host cell with the natural products labyrinthopeptin A1 and A2 is a viable strategy to inhibit the proliferation of a broad range of viruses from different families, including chikungunya virus, dengue virus, Zika virus, Kaposi's sarcoma-associated herpesvirus, and cytomegalovirus. Labyrinthopeptins bind to viral phosphatidylethanolamine and induce virolysis without exerting cytotoxicity on host cells. This represents a novel and unusual mechanism to tackle medically relevant viral infections.

Fatty acid synthase and stearoyl-CoA desaturase-1 are conserved druggable cofactors of Old World Alphavirus genome replication

Chikungunya virus (CHIKV) is a rapidly emerging mosquito-borne RNA virus that causes epidemics of debilitating disease in tropical and sub-tropical regions with autochtonous transmission in regions with temperate climate. Currently, there is no licensed vaccine or specific antiviral drug available against CHIKV infection. In this study, we examine the role, in the CHIKV viral cycle, of fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD1), two key lipogenic enzymes required for fatty acid production and early desaturation. We show that both enzymes and their upstream regulator PI3K are required for optimal CHIKV infection. We demonstrate that pharmacologic manipulation of FASN or SCD1 enzymatic activity by non-toxic concentrations of cerulenin or CAY10566 decreases CHIKV genome replication. Interestingly, a similar inhibitory effect was also obtained with Orlistat, an FDA-approved anti-obesity drug that targets FASN activity. These drugs were also effective against Mayaro virus (MAYV), an under-studied arthritogenic Old world Alphavirus endemic in South American countries with potential risk of emergence, urbanization and dispersion to other regions. Altogether, our results identify FASN and SCD1 as conserved druggable cofactors of Alphavirus genome replication and support the broad-spectrum activity of drugs targeting the host fatty acids metabolism.

A new scope for orlistat: Effect of approved anti-obesity drug against experimental microsporidiosis

As the current therapies for intestinal microsporidiosis are either inconsistent in their efficacies or hampered by several adverse effects, alternative antimicrosporidial agents are being sought. The present study is the first that was designed to evaluate the potency of orlistat, an approved anti-obesity drug, against intestinal microsporidiosis caused by both Enterocytozoon bieneusi and Encephalitozoon intestinalis. Results were assessed through studying fecal and intestinal spore load, intestinal histopathological changes, viability, and infectivity of spores from treated animals. Results showed that orlistat has promising antimicrosporidia potential, with better results in E. intestinalis than E. bieneusi. The animals that received orlistat showed statistically significant decrease in the fecal and intestinal spore load, when compared to the corresponding control infected nontreated mice. The results were insignificant compared to fumagillin and albendazole. Light microscopic examination of stained intestinal sections revealed amelioration of the pathological changes and decreased inflammatory cells detected in the control infected nontreated mice. Spores encountered from stool of orlistat-treated E. bieneusi and E. intestinalis mice showed low viability and significant reduction of infectivity versus their control. Thus, considering the results of the present work, orlistat proved its effectiveness against the intestinal microsporidial infection.

The potential contribution of impaired brain glucose metabolism to congenital Zika syndrome

The Zika virus (ZIKV) became a major worldwide public concern in 2015 due to the congenital syndrome which presents the highest risk during the first trimester of pregnancy and includes microcephaly and eye malformations. Several cellular, genetic and molecular studies have shown alterations in metabolic pathways, endoplasmic reticulum (ER) stress, immunity and dysregulation of RNA and energy metabolism both in vivo and in vitro. Here we summarise the main metabolic complications, with a particular focus on the possibility that brain energy metabolism is altered following ZIKV infection, contributing to developmental abnormalities. Brain energetic failure has been implicated in neurological conditions such as autism disorder and epilepsy, as well as in metabolic diseases with severe neurodevelopmental complications such as Glut-1 deficiency syndrome. Therefore, these energetic alterations are of wide-ranging interest as they might be directly implicated in congenital ZIKV syndrome. Data showing increased glycolysis during ZIKV infection, presumably required for viral replication, might support the idea that the virus can cause energetic stress in the developing brain cells. Consequences may include neuroinflammation, cell cycle dysregulation and cell death. Ketone bodies are non-glycolytic brain fuels that are produced during neonatal life, starvation or fasting, ingestion of high-fat low-carbohydrate diets, and following supplementation with ketone esters. We propose that dietary ketones might alter the course of the disease and could even provide some degree of prevention of ZIKV-associated abnormalities and potentially related neurological conditions characterised by brain glucose impairment.

Analysis of cellular proteome changes in response to ZIKV NS2B-NS3 protease expression

The recent emergence of Zika virus (ZIKV) has caused global concern as a result of the association with neurological disorders, and brain development dysfunction in fetuses of mothers who become infected with ZIKV during pregnancy. The NS2B-NS3 protease is important for viral replication and offers an attractive drug target. In addition to processing the viral polypeptide, evidence has shown that the NS2B-NS3 protease also targets cellular proteins as part of the viral replication process. This study sought to determine new host cell protein targets of ZIKV NS2B-NS3 (zNS2B-NS3). Plasmids encoding the protease domains of zNS2B-NS3pro and an inactive zNS2B-NS3(S135A) were transfected into HEK293T/17 cells and differentially expressed proteins were detected by 2D gel electrophoresis. A total of 18 protein spots were observed as differentially expressed between zNS2B-NS3pro and zNS2B-NS3(S135A), of which 7 were selected for identification by mass spectrometry. Four proteins (protein disulfide-isomerase A3 (PDIA3), heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1), voltage-dependent anion-selective channel (VDAC) and aldolase A (ALDOA)) were selected for validation by independent transient expression and western blot analysis. Three proteins (PDIA3, hnRNP A2/B1 and ALDOA) were successfully validated, but only two proteins (PDIA3 and ALDOA) were shown to be regulated in ZIKV infection in agreement with the results of the transfection experiments. This study has identified two proteins, PDIA3 an ALDOA whose expression is modulated by the ZIKV NS2B-NS3 protease, and these proteins are involved in the ER stress response and glycolysis respectively, two critical cellular processes in ZIKV infection.

Role of Host Cell Secretory Machinery in Zika Virus Life Cycle

The high human cost of Zika virus infections and the rapid establishment of virus circulation in novel areas, including the United States, present an urgent need for countermeasures against this emerging threat. The development of an effective vaccine against Zika virus may be problematic because of the cross reactivity of the antibodies with other flaviviruses leading to antibody-dependent enhancement of infection. Moreover, rapidly replicating positive strand RNA viruses, including Zika virus, generate large spectrum of mutant genomes (quasi species) every replication round, allowing rapid selection of variants resistant to drugs targeting virus-specific proteins. On the other hand, viruses are ultimate cellular parasites and rely on the host metabolism for every step of their life cycle, thus presenting an opportunity to manipulate host processes as an alternative approach to suppress virus replication and spread. Zika and other flaviviruses critically depend on the cellular secretory pathway, which transfers proteins and membranes from the ER through the Golgi to the plasma membrane, for virion assembly, maturation and release. In this review, we summarize the current knowledge of interactions of Zika and similar arthropod-borne flaviviruses with the cellular secretory machinery with a special emphasis on virus-specific changes of the secretory pathway. Identification of the regulatory networks and effector proteins required to accommodate the trafficking of virions, which represent a highly unusual cargo for the secretory pathway, may open an attractive and virtually untapped reservoir of alternative targets for the development of superior anti-viral drugs.

The Effect of Permethrin Resistance on Aedes aegypti Transcriptome Following Ingestion of Zika Virus Infected Blood

Aedes aegypti (L.) is the primary vector of many emerging arboviruses. Insecticide resistance among mosquito populations is a consequence of the application of insecticides for mosquito control. We used RNA-sequencing to compare transcriptomes between permethrin resistant and susceptible strains of Florida Ae. aegypti in response to Zika virus infection. A total of 2459 transcripts were expressed at significantly different levels between resistant and susceptible Ae. aegypti. Gene ontology analysis placed these genes into seven categories of biological processes. The 863 transcripts were expressed at significantly different levels between the two mosquito strains (up/down regulated) more than 2-fold. Quantitative real-time PCR analysis was used to validate the Zika-infection response. Our results suggested a highly overexpressed P450, with AAEL014617 and AAEL006798 as potential candidates for the molecular mechanism of permethrin resistance in Ae. aegypti. Our findings indicated that most detoxification enzymes and immune system enzymes altered their gene expression between the two strains of Ae. aegypti in response to Zika virus infection. Understanding the interactions of arboviruses with resistant mosquito vectors at the molecular level allows for the possible development of new approaches in mitigating arbovirus transmission. This information sheds light on Zika-induced changes in insecticide resistant Ae. aegypti with implications for mosquito control strategies.

Perturbation of Intracellular Cholesterol and Fatty Acid Homeostasis During Flavivirus Infections

Cellular lipid homeostasis is maintained through an intricately linked array of anabolic and catabolic pathways. Upon flavivirus infections, these are significantly altered: on the one hand, these viruses can co-opt lipid metabolic pathways to generate ATP to facilitate replication, or to synthesize membrane components to generate replication sites; on the other hand, more recent evidence suggests counter strategies employed by host cells, which actively modulate several of these networks in response to infection, enhancing interferon signaling by doing so, and thus creating an antiviral environment. In this review, we discuss recent data on mechanisms of alteration of lipid metabolic pathways during infection by flaviviruses, with a focus on cholesterol and fatty acid biosynthesis, which can be manipulated by the invading viruses to support replication, but can also be modulated by the host immune system itself, as a means to fight infection.

Screening of melatonin, α-tocopherol, folic acid, acetyl-L-carnitine and resveratrol for anti-dengue 2 virus activity

OBJECTIVE

Infections with the mosquito transmitted dengue virus (DENV) are a significant public health burden in many parts of the world. Despite the introduction of a commercial vaccine in some parts of the world, the majority of the populations at risk of infection remain unprotected against this disease, and there is currently no treatment for DENV infection. Natural compounds offer the prospect of cheap and sustainable therapeutics to reduce the disease burden during infection, and thus potentially alleviate the risk of more severe disease. This study evaluated the potential anti-DENV 2 activity of five natural compounds namely melatonin, α-tocopherol, folic acid, acetyl-L-carnitine and resveratrol in two different cell lines.

RESULTS

Screening of the compounds showed that one compound (acetyl-L-carnitine) showed no effect on DENV infection, three compounds (melatonin, α-tocopherol and folic acid) slightly increased levels of infection, while the 5th compound, resveratrol, showed some limited anti-DENV activity, with resveratrol reducing virus output with an EC₅₀ of less than 25 μM. These results suggest that some commonly taken natural compounds may have beneficial effects on DENV infection, but that others may potentially add to the disease burden.

Transcriptional Changes during Naturally Acquired Zika Virus Infection Render Dendritic Cells Highly Conducive to Viral Replication

Although dendritic cells are among the human cell population best equipped for cell-intrinsic antiviral immune defense, they seem highly susceptible to infection with the Zika virus (ZIKV). Using highly purified myeloid dendritic cells isolated from individuals with naturally acquired acute infection, we here show that ZIKV induces profound perturbations of transcriptional signatures relative to healthy donors. Interestingly, we noted a remarkable downregulation of antiviral interferon-stimulated genes and innate immune sensors, suggesting that ZIKV can actively suppress interferon-dependent immune responses. In contrast, several host factors known to support ZIKV infection were strongly upregulated during natural ZIKV infection; these transcripts included AXL, the main entry receptor for ZIKV; SOCS3, a negative regulator of ISG expression; and IDO-1, a recognized inducer of regulatory T cell responses. Thus, during in vivo infection, ZIKV can transform the transcriptome of dendritic cells in favor of the virus to render these cells highly conducive to ZIKV infection.