Ebolaviruses: New roles for old proteins

Deep sequencing of serially passaged Sudan virus in guinea pigs uncovers adaptive mutations

Orthoebolaviruses are non-segmented, negative sense RNA viruses that make up the genus Orthoebolavirus in the family Filoviridae. Sudan virus (SUDV) is a highly pathogenic orthoebolavirus that causes severe disease in humans. In the last 45 years, SUDV has been responsible for several outbreaks in eastern Africa, particularly in Sudan and Uganda, with an average case fatality rate of approximately 50 %. Despite having caused numerous outbreaks, including a recent outbreak in 2022, no licensed therapeutics or prophylactics currently exist for Sudan virus disease. Small animal models like mice, hamsters, and guinea pigs have paved the way for the initial evaluation of filovirus countermeasures; however, since filoviruses are apathogenic in immunocompetent rodents, they must first be adapted through serial passaging. As a result of this process, viruses acquire genomic changes that may contribute to increased virulence and lethality. Currently, only a single immunocompetent small animal model exists for SUDV, where the virus was serially passaged in guinea pigs until uniform lethality was observed. To better understand the serial passaging process, we used next-generation sequencing to identify and quantify the mutations that arose throughout the adaptation process in guinea pigs. We identified 7 nonsynonymous and 9 synonymous mutations that were present at frequencies near 100 % at the end of serial passaging. The glycoprotein and virion protein (VP) 40 harboured many of the substitutions, most of which were nonsynonymous, while VP35 and VP24 each maintained a single nonsynonymous mutation. These results are consistent with the previously determined genome sequence, obtained by Sanger sequencing, with two notable exceptions: we identified a novel mutation in VP40, but we were unable to confirm the mutation in the genome leader, due to poor sequence coverage. This analysis has allowed us to identify adaptive hotspots within the viral genome, which may hint at the molecular determinants contributing to pathogenicity.

Guardians at the Gate: Optimization of Small Molecule Entry Inhibitors of Ebola and Marburg Viruses

Ebola and Marburg (EBOV and MARV) filoviral infections lead to fatal hemorrhagic fevers and have caused over 30 outbreaks in the last 50 years. Currently, there are no FDA-approved small molecule therapeutics for effectively treating filoviral diseases. To address this unmet medical need, we have conducted a systematic structural optimization of an early lead compound, N-(4-(4-methylpiperidin-1-yl)-3-(trifluoromethyl)phenyl)-4-(morpholinomethyl)benzamide (1), borne from our previously reported hit-to-lead effort. This secondary round of structure-activity relationship (SAR) involved the design and synthesis of several deconstructed and reconstructed analogs of compound 1, which were then tested against pseudotyped EBOV and MARV. The antiviral activities of the most promising leads were further validated in infectious assays. The optimized analogs exhibited desirable antiviral activity against different ebolaviruses and reduced off-target activity. Additionally, they also possessed druglike properties, that make them ideal candidates for in vivo efficacy studies as part of our ongoing drug discovery campaign against EBOV and MARV.

Lineage classification and selective site identification of Orthoebolavirus zairense

As the high pathogenic species of Filoviridae virus family, Orthoebolavirus zairense (EBOV) shows frequent outbreaks in human in recently years since its first emerging in 1976 in Democratic Republic of the Congo (COD), bringing ongoing risks and burden on public health safety. Here, the phylogenetic relationship among major outbreaks was analyzed. The results showed that EBOV isolates could be divided into four lineages according to spatial and temporal epidemics. Then, the positive selection sites (PSSs) were detected on all proteins of the EBOV, exhibiting lineage characteristic. Particularly, sites in GP and VP24 were identified to be significantly under positive selection, and partial of which were maintained in the latest isolates in 2021. GP and L were found to have high variability between lineages. Substitutions including F443L and F443S in GP, as well as F1610L and I1951V in L could be characteristic of the two large outbreaks in COD (2018) and West Africa (2014), respectively. Further, substitutions of significant PSSs in VP24 and L proteins were visualized for analysis of structural changes, which may affect EBOV pathogenesis. In summary, our results gains insights in genetic characteristic and adaptive evolution of EBOV, which could facilitate gene functional research against EBOV.

Ebola virus sequesters IRF3 in viral inclusion bodies to evade host antiviral immunity

Viral inclusion bodies (IBs) commonly form during the replication of Ebola virus (EBOV) in infected cells, but their role in viral immune evasion has rarely been explored. Here, we found that interferon regulatory factor 3 (IRF3), but not TANK-binding kinase 1 (TBK1) or IκB kinase epsilon (IKKε), was recruited and sequestered in viral IBs when the cells were infected by EBOV transcription- and replication-competent virus-like particles (trVLPs). Nucleoprotein/virion protein 35 (VP35)-induced IBs formation was critical for IRF3 recruitment and sequestration, probably through interaction with STING. Consequently, the association of TBK1 and IRF3, which plays a vital role in type I interferon (IFN-I) induction, was blocked by EBOV trVLPs infection. Additionally, IRF3 phosphorylation and nuclear translocation induced by Sendai virus or poly(I:C) stimulation were suppressed by EBOV trVLPs. Furthermore, downregulation of STING significantly attenuated VP35-induced IRF3 accumulation in IBs. Coexpression of the viral proteins by which IB-like structures formed was much more potent in antagonizing IFN-I than expression of the IFN-I antagonist VP35 alone. These results suggested a novel immune evasion mechanism by which EBOV evades host innate immunity.

Navigating the Complex Landscape of Ebola Infection Treatment: A Review of Emerging Pharmacological Approaches

In 1976 Ebola revealed itself to the world, marking the beginning of a series of localized outbreaks. However, it was the Ebola outbreak that began in 2013 that incited fear and anxiety around the globe. Since then, our comprehension of the virus has been steadily expanding. Ebola virus (EBOV), belonging to the Orthoebolavirus genus of the Filoviridae family, possesses a non-segmented, negative single-stranded RNA genome comprising seven genes that encode multiple proteins. These proteins collectively orchestrate the intricate process of infecting host cells. It is not possible to view each protein as monofunctional. Instead, they synergistically contribute to the pathogenicity of the virus. Understanding this multifaceted replication cycle is crucial for the development of effective antiviral strategies. Currently, two antibody-based therapeutics have received approval for treating Ebola virus disease (EVD). In 2022, the first evidence-based clinical practice guideline dedicated to specific therapies for EVD was published. Although notable progress has been made in recent years, deaths still occur. Consequently, there is an urgent need to enhance the therapeutic options available to improve the outcomes of the disease. Emerging therapeutics can target viral proteins as direct-acting antivirals or host factors as host-directed antivirals. They both have advantages and disadvantages. One way to bypass some disadvantages is to repurpose already approved drugs for non-EVD indications to treat EVD. This review offers detailed insight into the role of each viral protein in the replication cycle of the virus, as understanding how the virus interacts with host cells is critical to understanding how emerging therapeutics exert their activity. Using this knowledge, this review delves into the intricate mechanisms of action of current and emerging therapeutics.

Extracellular vesicle storm during the course of Ebola virus infection in primates

Introduction

Ebola virus (EBOV) is an RNA virus of the Filoviridae family that is responsible for outbreaks of hemorrhagic fevers in primates with a lethality rate as high as 90%. EBOV primarily targets host macrophages leading to cell activation and systemic cytokine storm, and fatal infection is associated with an inhibited interferon response, and lymphopenia. The EBOV surface glycoprotein (GP) has been shown to directly induce T cell depletion and can be secreted outside the virion via extracellular vesicles (EVs), though most studies are limited to epithelial cells and underlying mechanisms remain poorly elucidated.

Methods

To assess the role of GP on EBOV-induced dysregulation of host immunity, we first utilized EBOV virus-like particles (VLPs) expressing VP40 and NP either alone (Bald-VLP) or in conjunction with GP (VLP-GP) to investigate early inflammatory responses in THP-1 macrophages and in a murine model. We then sought to decipher the role of non-classical inflammatory mediators such as EVs over the course of EBOV infection in two EBOV-infected rhesus macaques by isolating and characterizing circulatory EVs throughout disease progression using size exclusion chromatography, nanoparticle tracking-analysis, and LC-MS/MS.

Results

While all VLPs could induce inflammatory mediators and recruit small peritoneal macrophages, pro-inflammatory cytokine and chemokine gene expression was exacerbated by the presence of GP. Further, quantification of EVs isolated from infected rhesus macaques revealed that the concentration of vesicles peaked in circulation at the terminal stage, at which time EBOV GP could be detected in host-derived exosomes. Moreover, comparative proteomics conducted across EV populations isolated from serum at various time points before and after infection revealed differences in host-derived protein content that were most significantly pronounced at the endpoint of infection, including significant expression of mediators of TLR4 signaling.

Discussion

These results suggest a dynamic role for EVs in the modification of disease states in the context of EBOV. Overall, our work highlights the importance of viral factors, such as the GP, and host derived EVs in the inflammatory cascade and pathogenesis of EBOV, which can be collectively further exploited for novel antiviral development.

High-efficiency genetic engineering toolkit for virus based on lambda red-mediated recombination

PURPOSE

Viruses, such as Ebola virus (EBOV), evolve rapidly and threaten the human health. There is a great demand to exploit efficient gene-editing techniques for the identification of virus to probe virulence mechanism for drug development.

METHODS

Based on lambda Red recombination in Escherichia coli (E. coli), counter-selection, and in vitro annealing, a high-efficiency genetic method was utilized here for precisely engineering viruses. EBOV trVLPs assay and dual luciferase reporter assay were used to further test the effect of mutations on virus replication.

RESULTS

Considering the significance of matrix protein VP24 in EBOV replication, the types of mutations within vp24, including several single-base substitutions, one double-base substitution, two seamless deletions, and one targeted insertion, were generated on the multi-copy plasmid of E. coli. Further, the length of the homology arms for recombination and in vitro annealing, and the amount of DNA cassettes and linear plasmids were optimized to create a more elaborate and cost-efficient protocol than original approach. The effects of VP24 mutations on the expression of a reporter gene (luciferase) from the EBOV minigenome were determined, and results indicated that mutations of key sites within VP24 have significant impacts on EBOV replication.

CONCLUSION

This precise mutagenesis method will facilitate effective and simple editing of viral genes in E. coli.

Ethnopharmacological Potential of Phytochemicals and Phytogenic Products against Human RNA Viral Diseases as Preventive Therapeutics

RNA viruses have been the most destructive due to their transmissibility and lack of control measures. Developments of vaccines for RNA viruses are very tough or almost impossible as viruses are highly mutable. For the last few decades, most of the epidemic and pandemic viral diseases have wreaked huge devastation with innumerable fatalities. To combat this threat to mankind, plant-derived novel antiviral products may contribute as reliable alternatives. They are assumed to be nontoxic, less hazardous, and safe compounds that have been in uses in the beginning of human civilization. In this growing COVID-19 pandemic, the present review amalgamates and depicts the role of various plant products in curing viral diseases in humans.

Virus-CKB 2.0: Viral-Associated Disease-Specific Chemogenomics Knowledgebase

Transmissible and infectious viruses can cause large-scale epidemics around the world. This is because the virus can constantly mutate and produce different variants and subvariants to counter existing treatments. Therefore, a variety of treatments are urgently needed to keep up with the mutation of the viruses. To facilitate the research of such treatment, we updated our Virus-CKB 1.0 to Virus-CKB 2.0, which contains 10 kinds of viruses, including enterovirus, dengue virus, hepatitis C virus, Zika virus, herpes simplex virus, Andes orthohantavirus, human immunodeficiency virus, Ebola virus, Lassa virus, influenza virus, coronavirus, and norovirus. To date, Virus-CKB 2.0 archived at least 65 antiviral drugs (such as remdesivir, telaprevir, acyclovir, boceprevir, and nelfinavir) in the market, 178 viral-related targets with 292 available 3D crystal or cryo-EM structures, and 3766 chemical agents reported for these target proteins. Virus-CKB 2.0 is integrated with established tools for target prediction and result visualization; these include HTDocking, TargetHunter, blood-brain barrier (BBB) predictor, Spider Plot, etc. The Virus-CKB 2.0 server is accessible at https://www.cbligand.org/g/virus-ckb. By using the established chemogenomic tools and algorithms and newly developed tools, we can screen FDA-approved drugs and chemical compounds that may bind to these proteins involved in viral-associated disease regulation. If the virus strain mutates and the vaccine loses its effect, we can still screen drugs that can be used to treat the mutated virus in a fleeting time. In some cases, we can even repurpose FDA-approved drugs through Virus-CKB 2.0.

Structural and Functional Aspects of Ebola Virus Proteins

Ebola virus (EBOV), member of genus Ebolavirus, family Filoviridae, have a non-segmented, single-stranded RNA that contains seven genes: (a) nucleoprotein (NP), (b) viral protein 35 (VP35), (c) VP40, (d) glycoprotein (GP), (e) VP30, (f) VP24, and (g) RNA polymerase (L). All genes encode for one protein each except GP, producing three pre-proteins due to the transcriptional editing. These pre-proteins are translated into four products, namely: (a) soluble secreted glycoprotein (sGP), (b) Δ-peptide, (c) full-length transmembrane spike glycoprotein (GP), and (d) soluble small secreted glycoprotein (ssGP). Further, shed GP is released from infected cells due to cleavage of GP by tumor necrosis factor α-converting enzyme (TACE). This review presents a detailed discussion on various functional aspects of all EBOV proteins and their residues. An introduction to ebolaviruses and their life cycle is also provided for clarity of the available analysis. We believe that this review will help understand the roles played by different EBOV proteins in the pathogenesis of the disease. It will help in targeting significant protein residues for therapeutic and multi-protein/peptide vaccine development.

Filovirus Neutralising Antibodies: Mechanisms of Action and Therapeutic Application

Filoviruses, especially Ebola virus, cause sporadic outbreaks of viral haemorrhagic fever with very high case fatality rates in Africa. The 2013–2016 Ebola epidemic in West Africa provided large survivor cohorts spurring a large number of human studies which showed that specific neutralising antibodies played a key role in protection following a natural Ebola virus infection, as part of the overall humoral response and in conjunction with the cellular adaptive response. This review will discuss the studies in survivors and animal models which described protective neutralising antibody response. Their mechanisms of action will be detailed. Furthermore, the importance of neutralising antibodies in antibody-based therapeutics and in vaccine-induced responses will be explained, as well as the strategies to avoid immune escape from neutralising antibodies. Understanding the neutralising antibody response in the context of filoviruses is crucial to furthering our understanding of virus structure and function, in addition to improving current vaccines & antibody-based therapeutics.

Modulation of immune response in Ebola virus disease

Ebola virus disease targets and destroys immune cells, including macrophages and dendritic cells, leading to impairment of host response. After infection, a combination of strategies including alteration and evasion of immune response culminating in a strong inflammatory response can lead to multi-organ failure and death in most infected patients. This review discusses immune response dynamics, mainly focusing on how Ebola manipulates innate and adaptive immune responses and strategizes to thwart host immune responses. We also discuss the challenges and prospects of developing therapeutics and vaccines against Ebola.

Genome structure and genetic diversity in the Ebola virus

Ebola is a deadly pathogen responsible for Ebola virus disease, first came to prominence in the year 1976. This rapidly evolving virus imposed a serious threat to the human population in the last few decades and also continues to be a probable threat to our race. A better understanding of the virus in terms of its genomic structure is very much needed to develop an effective antiviral therapy against this deadly pathogen. Complete knowledge of its genomic structure and variations will help us and the entire scientific community to design effective therapy in terms of either vaccine development or the development of proper antiviral medicine.

Conserved immunogenic peptides of Ebola glycoprotein elicit immune response in human peripheral blood mononuclear cells

In the past 45 years, ebolaviruses have periodically caused epidemics on the African continent. In December 2019, approval of a recombinant vector-based EBOV vaccine, named Ervebo, came as encouraging news; still, there is a long way to go in the development of an accessible, global, and pan-ebolavirus vaccine. The current study expanded our previous in silico work which was conducted on ebolavirus glycoprotein and this resulted in the identification of three potentially immunogenic peptides (P1 - FKRTSFFLWVIILFQRTFSIPL, P2 - LANETTQALQLF, and P3 - RATTELRTFSILNRKAIDF). An analysis to estimate the number of expected human leukocyte antigen (HLA) responders revealed that P1, P2, and P3 can potentially interact with 2540, 2150, and 2802 HLA alleles, respectively. Further, these peptides were subject to in vitro analysis wherein the human peripheral blood mononuclear cell proliferation and interferon-gamma (IFN-γ) production by peptide stimulated cells was studied in 10 healthy human blood samples with the help of a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and a sandwich enzyme-linked immunosorbent assay (ELISA) respectively. P3 presented the best results, a significant (P < 0.05) peptide induced cell proliferation and IFN-γ stimulation for 8 and 10 samples, respectively, followed by P1 (5 and 6) and P2 (5 and 7). The in silico and in vitro results obtained in this study indicate the immunogenic potential of these peptides and warrant exploration of the effects on other cytokines as well as in vivo experimental validation.

Potential pharmacological strategies targeting the Niemann-Pick C1 receptor and Ebola virus glycoprotein interaction

Niemann-Pick C1 (NPC1) receptor is an intracellular protein located in late endosomes and lysosomes whose main function is to regulate intracellular cholesterol trafficking. Besides being postulated as necessary for the infection of highly pathogenic viruses in which the integrity of cholesterol transport is required, this protein also allows the entry of the Ebola virus (EBOV) into the host cells acting as an intracellular receptor. EBOV glycoprotein (EBOV-GP) interaction with NPC1 at the endosomal membrane triggers the release of the viral material into the host cell, starting the infective cycle. Disruption of the NPC1/EBOV-GP interaction could represent an attractive strategy for the development of drugs aimed at inhibiting viral entry and thus infection. Some of the today available EBOV inhibitors were proposed to interrupt this interaction, but molecular and structural details about their mode of action are still preliminary thus more efforts are needed to properly address these points. Here, we provide a critical discussion of the potential of NPC1 and its interaction with EBOV-GP as a therapeutic target for viral infections.

Plant-derived exosomal microRNAs inhibit lung inflammation induced by exosomes SARS-CoV-2 Nsp12

Lung inflammation is a hallmark of coronavirus disease 2019 (COVID-19). In this study, we show that mice develop inflamed lung tissue after being administered exosomes released from the lung epithelial cells exposed to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Nsp12 and Nsp13 (exosomes^Nsp12Nsp13). Mechanistically, we show that exosomes^Nsp12Nsp13 are taken up by lung macrophages, leading to activation of nuclear factor κB (NF-κB) and the subsequent induction of an array of inflammatory cytokines. Induction of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β from exosomes^Nsp12Nsp13-activated lung macrophages contributes to inducing apoptosis in lung epithelial cells. Induction of exosomes^Nsp12Nsp13-mediated lung inflammation was abolished with ginger exosome-like nanoparticle (GELN) microRNA (miRNA aly-miR396a-5p. The role of GELNs in inhibition of the SARS-CoV-2-induced cytopathic effect (CPE) was further demonstrated via GELN aly-miR396a-5p- and rlcv-miR-rL1-28-3p-mediated inhibition of expression of Nsp12 and spike genes, respectively. Taken together, our results reveal exosomes^Nsp12Nsp13 as potentially important contributors to the development of lung inflammation, and GELNs are a potential therapeutic agent to treat COVID-19.

Immunization and Drug Metabolizing Enzymes: Focus on Hepatic Cytochrome P450 3A

OBJECTIVE

Infectious disease emergencies like the 2013-2016 Ebola epidemic and the 2009 influenza and current SARS-CoV-2 pandemics illustrate that vaccines are now given to diverse populations with preexisting pathologies requiring pharmacological management. Many natural biomolecules (steroid hormones, fatty acids, vitamins) and ~60% of prescribed medications are processed by hepatic cytochrome P450 (CYP) 3A4. The objective of this work was to determine the impact of infection and vaccines on drug metabolism.

METHODS

The impact of an adenovirus-based vaccine expressing Ebola glycoprotein (AdEBO) and H1N1 and H3N2 influenza viruses on hepatic CYP 3A4 and associated nuclear receptors was evaluated in human hepatocytes (HC-04 cells) and in mice.

RESULTS

CYP3A activity was suppressed by 55% in mice 24 h after administration of mouse-adapted H1N1, while ˂10% activity remained in HC-04 cells after infection with H1N1 and H3N2 due to global suppression of cellular translation capacity, indicated by reduction (70%, H1N1, 56%, H3N2) of phosphorylated eukaryotic translation initiation factor 4e (eIF4E). AdEBO suppressed CYP3A activity in vivo (44%) and in vitro (26%) 24 hours after infection.

CONCLUSION

As the clinical evaluation of vaccines for SARS-CoV-2 and other global pathogens rise, studies to evaluate the impact of new vaccines and emerging pathogens on CYP3A4 and other metabolic enzymes are warranted to avoid therapeutic failures that could further compromise the public health during infectious disease emergencies.

The Role of Type I Interferons in the Pathogenesis and Treatment of COVID-19

Type I interferons (IFN-I) were first discovered over 60 years ago in a classical experiment by Isaacs and Lindenman, who showed that IFN-Is possess antiviral activity. Later, it became one of the first approved protein drugs using heterologous protein expression systems, which allowed its large-scale production. It has been approved, and widely used in a pleiotropy of diseases, including multiple-sclerosis, hepatitis B and C, and some forms of cancer. Preliminary clinical data has supported its effectiveness against potential pandemic pathogens such as Ebola and SARS. Still, more efficient and specific drugs have taken its place in treating such diseases. The COVID-19 global pandemic has again lifted the status of IFN-Is to become one of the more promising drug candidates, with initial clinical trials showing promising results in reducing the severity and duration of the disease. Although SARS-CoV-2 inhibits the production of IFNβ and thus obstructs the innate immune response to this virus, it is sensitive to the antiviral activity of externally administrated IFN-Is. In this review I discuss the diverse modes of biological actions of IFN-Is and how these are related to biophysical parameters of IFN-I-receptor interaction and cell-type specificity in light of the large variety of binding affinities of the different IFN-I subtypes towards the common interferon receptor. Furthermore, I discuss how these may guide the optimized use IFN-Is in combatting COVID-19.

Ebola Virus Nucleocapsid-Like Structures Utilize Arp2/3 Signaling for Intracellular Long-Distance Transport

The intracellular transport of nucleocapsids of the highly pathogenic Marburg, as well as Ebola virus (MARV, EBOV), represents a critical step during the viral life cycle. Intriguingly, a population of these nucleocapsids is distributed over long distances in a directed and polar fashion. Recently, it has been demonstrated that the intracellular transport of filoviral nucleocapsids depends on actin polymerization. While it was shown that EBOV requires Arp2/3-dependent actin dynamics, the details of how the virus exploits host actin signaling during intracellular transport are largely unknown. Here, we apply a minimalistic transfection system to follow the nucleocapsid-like structures (NCLS) in living cells, which can be used to robustly quantify NCLS transport in live cell imaging experiments. Furthermore, in cells co-expressing LifeAct, a marker for actin dynamics, NCLS transport is accompanied by pulsative actin tails appearing on the rear end of NCLS. These actin tails can also be preserved in fixed cells, and can be visualized via high resolution imaging using STORM in transfected, as well as EBOV infected, cells. The application of inhibitory drugs and siRNA depletion against actin regulators indicated that EBOV NCLS utilize the canonical Arp2/3-Wave1-Rac1 pathway for long-distance transport in cells. These findings highlight the relevance of the regulation of actin polymerization during directed EBOV nucleocapsid transport in human cells.

A Conserved Tryptophan in the Ebola Virus Matrix Protein C-Terminal Domain Is Required for Efficient Virus-Like Particle Formation

The Ebola virus (EBOV) harbors seven genes, one of which is the matrix protein eVP40, a peripheral protein that is sufficient to induce the formation of virus-like particles from the host cell plasma membrane. eVP40 can form different structures to fulfil different functions during the viral life cycle, although the structural dynamics of eVP40 that warrant dimer, hexamer, and octamer formation are still poorly understood. eVP40 has two conserved Trp residues at positions 95 and 191. The role of Trp⁹⁵ has been characterized in depth as it serves as an important residue in eVP40 oligomer formation. To gain insight into the functional role of Trp¹⁹¹ in eVP40, we prepared mutations of Trp¹⁹¹ (W191A or W191F) to determine the effects of mutation on eVP40 plasma membrane localization and budding as well as eVP40 oligomerization. These in vitro and cellular experiments were complemented by molecular dynamics simulations of the wild-type (WT) eVP40 structure versus that of W191A. Taken together, Trp is shown to be a critical amino acid at position 191 as mutation to Ala reduces the ability of VP40 to localize to the plasma membrane inner leaflet and form new virus-like particles. Further, mutation of Trp¹⁹¹ to Ala or Phe shifted the in vitro equilibrium to the octamer form by destabilizing Trp¹⁹¹ interactions with nearby residues. This study has shed new light on the importance of interdomain interactions in stability of the eVP40 structure and the critical nature of timing of eVP40 oligomerization for plasma membrane localization and viral budding.

Ebola virus glycoprotein GP1-host cell-surface HSPA5 binding site prediction

Ebola virus (EBOV) infection is a widespread infection that has created a bad memory in Africa. In the 2014 and 2015 outbreak, more than 28,000 infections were reported by the World Health Organization, with about 11,300 deaths in Guinea, Liberia, and Sierra Leone. Heat shock protein A5 (HSPA5), termed also GRP78, is a host cell chaperone protein responsible for the unfolded protein response in the endoplasmic reticulum. Under stress, HSPA5 is upregulated and becomes cell-surface exposed. Recent studies report the association of cell-surface HSPA5 with EBOV glycoproteins GP1 and GP2. In this study, structural and sequence analysis and molecular docking are used to predict the possible binding site between the cell-surface HSPA5 and EBOV GP1. The results show a promising binding site that supports the hypothesis of HSPA5 selectivity for binding to a specific peptide sequence (pep42). This study paves the way to suggest possible inhibitors to stop viral association with cell-surface receptors and subsequently reduce viral infection.

Ebola virus disease: An emerging and re-emerging viral threat

The genus Ebolavirus from the family Filoviridae is composed of five species including Sudan ebolavirus, Reston ebolavirus, Bundibugyo ebolavirus, Taï Forest ebolavirus, and Ebola virus (previously known as Zaire ebolavirus). These viruses have a large non-segmented, negative-strand RNA of approximately 19 kb that encodes for glycoproteins (i.e., GP, sGP, ssGP), nucleoproteins, virion proteins (i.e., VP 24, 30,40) and an RNA dependent RNA polymerase. These viruses have become a global health concern because of mortality, their rapid dissemination, new outbreaks in West-Africa, and the emergence of a new condition known as "Post-Ebola virus disease syndrome" that resembles inflammatory and autoimmune conditions such as rheumatoid arthritis, systemic lupus erythematosus and spondyloarthritis with uveitis. However, there are many gaps in the understanding of the mechanisms that may induce the development of such autoimmune-like syndromes. Some of these mechanisms may include a high formation of neutrophil extracellular traps, an uncontrolled "cytokine storm", and the possible formation of auto-antibodies. The likely appearance of autoimmune phenomena in Ebola survivors suppose a new challenge in the management and control of this disease and opens a new field of research in a special subgroup of patients. Herein, the molecular biology, pathogenesis, clinical manifestations, and treatment of Ebola virus disease are reviewed and some strategies for control of disease are discussed.

Computational Drug Design against Ebola Virus Targeting Viral Matrix Protein VP30

Ebola viral disease (EVD) is a deadly infectious hemorrhagic viral fever caused by the Ebola virus with a high mortality rate. Until date, there is no effective drug or vaccination available to combat this condition. This study focuses on designing an effective antiviral drug for Ebola viral disease targeting viral protein 30 (VP30) of Ebola virus, highly required for transcription initiation. The lead molecules were screened for Lipinski rule of five, ADMET study following which molecular docking and bioactivity prediction was carried out. The compounds with the least binding energy were analyzed using interaction software. The results revealed that 6-Hydroxyluteolin and (-)-Arctigenin represent active lead compounds that inhibit the activity of VP30 protein and exhibits efficient pharmacokinetics. Both these compounds are plant-derived flavonoids and possess no known adverse effects on human health. In addition, they bind strongly to the predicted binding site centered on Lys180, suggesting that these two lead molecules can be imperative in designing a potential drug for EVD.

Ebola virus replication is regulated by the phosphorylation of viral protein VP35

Ebola virus (EBOV) is a zoonotic pathogen, the infection often results in severe, potentially fatal, systematic disease in human and nonhuman primates. VP35, an essential viral RNA-dependent RNA polymerase cofactor, is indispensable for Ebola viral replication and host innate immune escape. In this study, VP35 was demonstrated to be phosphorylated at Serine/Threonine by immunoblotting, and the major phosphorylation sites was S187, S205, T206, S208 and S317 as revealed by LC-MS/MS. By an EBOV minigenomic system, EBOV minigenome replication was shown to be significantly inhibited by the phosphorylation-defective mutant, VP35 S187A, but was potentiated by the phosphorylation mimic mutant VP35 S187D. Together, our findings demonstrate that EBOV VP35 is phosphorylated on multiple residues in host cells, especially on S187, which may contribute to efficient viral genomic replication and viral proliferation.

Chaperoning the Mononegavirales: Current Knowledge and Future Directions

The order Mononegavirales harbors numerous viruses of significant relevance to human health, including both established and emerging infections. Currently, vaccines are only available for a small subset of these viruses, and antiviral therapies remain limited. Being obligate cellular parasites, viruses must utilize the cellular machinery for their replication and spread. Therefore, targeting cellular pathways used by viruses can provide novel therapeutic approaches. One of the key challenges confronted by both hosts and viruses alike is the successful folding and maturation of proteins. In cells, this task is faced by cellular molecular chaperones, a group of conserved and abundant proteins that oversee protein folding and help maintain protein homeostasis. In this review, we summarize the current knowledge of how the Mononegavirales interact with cellular chaperones, highlight key gaps in our knowledge, and discuss the potential of chaperone inhibitors as antivirals.