Ebola-specific therapeutic antibodies from lab to clinic: The example of ZMapp.

In the 1990s, monoclonal antibodies (mAbs) progressed from scientific tools to advanced therapeutics, particularly for the treatment of cancers and autoimmune and inflammatory disorders. In the arena of infectious disease, the inauguration of mAbs as a post-exposure treatment in humans against Ebola virus (EBOV) occurred in response to the 2013-2016 West Africa outbreak. This review recounts the history of a candidate mAb treatment, ZMapp, beginning with its emergency use in the 2013-2016 outbreak and advancing to randomized controlled trials into the 2018-2020 African outbreak. We end with a brief discussion of the hurdles and promise toward mAb therapeutic use against infectious disease.

Ebola Virus Glycoprotein Strongly Binds to Membranes in the Absence of Receptor Engagement.

Ebola virus (EBOV) is an enveloped virus that must fuse with the host cell membrane in order to release its genome and initiate infection. This process requires the action of the EBOV envelope glycoprotein (GP), encoded by the virus, which resides in the viral envelope and consists of a receptor binding subunit, GP1, and a membrane fusion subunit, GP2. Despite extensive research, a mechanistic understanding of the viral fusion process is incomplete. To investigate GP-membrane association, a key step in the fusion process, we used two approaches: high-throughput measurements of single-particle diffusion and single-molecule measurements with optical tweezers. Using these methods, we show that the presence of the endosomal Niemann-Pick C1 (NPC1) receptor is not required for primed GP-membrane binding. In addition, we demonstrate this binding is very strong, likely attributed to the interaction between the GP fusion loop and the membrane's hydrophobic core. Our results also align with previously reported findings, emphasizing the significance of acidic pH in the protein-membrane interaction. Beyond Ebola virus research, our approach provides a powerful toolkit for studying other protein-membrane interactions, opening new avenues for a better understanding of protein-mediated membrane fusion events.

Oral administration of obeldesivir protects nonhuman primates against Sudan ebolavirus.

Obeldesivir (ODV, GS-5245) is an orally administered prodrug of the parent nucleoside of remdesivir (RDV) and is presently in phase 3 trials for COVID-19 treatment. In this work, we show that ODV and its circulating parent nucleoside metabolite, GS-441524, have similar in vitro antiviral activity against filoviruses, including Marburg virus, Ebola virus, and Sudan virus (SUDV). We also report that once-daily oral ODV treatment of cynomolgus monkeys for 10 days beginning 24 hours after SUDV exposure confers 100% protection against lethal infection. Transcriptomics data show that ODV treatment delayed the onset of inflammation and correlated with antigen presentation and lymphocyte activation. Our results offer promise for the further development of ODV to control outbreaks of filovirus disease more rapidly.

Human MARCH1, 2, and 8 block Ebola virus envelope glycoprotein cleavage via targeting furin P domain.

Membrane-associated RING-CH (MARCH) family proteins were recently reported to inhibit viral replication through multiple modes. Previous work showed that human MARCH8 blocked Ebola virus (EBOV) glycoprotein (GP) maturation. Our study here demonstrates that human MARCH1 and MARCH2 share a similar pattern to MARCH8 in restricting EBOV GP-pseudotyped viral infection. Human MARCH1 and MARCH2 retain EBOV GP at the trans-Golgi network, reduce its cell surface display, and impair EBOV GP-pseudotyped virions infectivity. Furthermore, we uncover that the host proprotein convertase furin could interact with human MARCH1/2 and EBOV GP intracellularly. Importantly, the furin P domain is verified to be recognized by MARCH1/2/8, which is critical for their blocking activities. Besides, bovine MARCH2 and murine MARCH1 also impair EBOV GP proteolytic processing. Altogether, our findings confirm that MARCH1/2 proteins of different mammalian origins showed a relatively conserved feature in blocking EBOV GP cleavage, which could provide clues for subsequent MARCHs antiviral studies and may facilitate the development of novel strategies to antagonize enveloped virus infection.

Immunogenicity and Vaccine Shedding After 1 or 2 Doses of rVSVΔG-ZEBOV-GP Ebola Vaccine (ERVEBO®): Results From a Phase 2, Randomized, Placebo-controlled Trial in Children and Adults.

BACKGROUND: The rVSVΔG-ZEBOV-GP vaccine (ERVEBO®) is a single-dose, live-attenuated, recombinant vesicular stomatitis virus vaccine indicated for the prevention of Ebola virus disease (EVD) caused by Zaire ebolavirus in individuals 12 months of age and older. METHODS: The Partnership for Research on Ebola VACcination (PREVAC) is a multicenter, phase 2, randomized, double-blind, placebo-controlled trial of 3 vaccine strategies in healthy children (ages 1-17) and adults, with projected 5 years of follow-up (NCT02876328). Using validated assays (GP-ELISA and PRNT), we measured antibody responses after 1-dose rVSVΔG-ZEBOV-GP, 2-dose rVSVΔG-ZEBOV-GP (given on Day 0 and Day 56), or placebo. Furthermore, we quantified vaccine virus shedding in a subset of children's saliva using RT-PCR. RESULTS: In total, 819 children and 783 adults were randomized to receive rVSVΔG-ZEBOV-GP (1 or 2 doses) or placebo. A single dose of rVSVΔG-ZEBOV-GP increased antibody responses by Day 28 that were sustained through Month 12. A second dose of rVSVΔG-ZEBOV-GP given on Day 56 transiently boosted antibody concentrations. In vaccinated children, GP-ELISA titers were superior to placebo and non-inferior to vaccinated adults. Vaccine virus shedding was observed in 31.7% of children, peaking by Day 7, with no shedding observed after Day 28 post-dose 1 or any time post-dose 2. CONCLUSIONS: A single dose of rVSVΔG-ZEBOV-GP induced robust antibody responses in children that was non-inferior to the responses induced in vaccinated adults. Vaccine virus shedding in children was time-limited and only observed after the first dose. Overall, these data support the use of rVSVΔG-ZEBOV-GP for the prevention of EVD in at-risk children. Clinical Trials Registration. The study is registered at ClinicalTrials.gov (NCT02876328), the Pan African Clinical Trials Registry (PACTR201712002760250), and the European Clinical Trials Register (EudraCT number: 2017-001798-18).

Prevention and post-exposure management of occupational exposure to Ebola virus.

There have been significant advances in the prevention and management of Ebola virus disease (EVD) caused by Zaire Ebola virus (ZEBOV), including the development of two effective vaccines, rVSV-ZEBOV and Ad26.ZEBOV/MVA-BN-Filo. In addition, ZEBOV monoclonal antibodies have become first-line therapy for EVD. However, the 2022-23 outbreak of Sudan Ebola virus (SUDV) in Uganda has highlighted the gap in current therapies and vaccines, whose efficacy is uncertain against non-ZEBOV species. Health-care and laboratory staff working in EVD treatment centres or Ebola virus diagnostic and research laboratories face unique risks relating to potential occupational exposure to Ebola viruses. Given the substantial morbidity and mortality associated with EVD, facilities should have strategies in place to manage occupational exposures, including consideration of post-exposure therapies. In this Review, we discuss currently available evidence for prevention and post-exposure prophylaxis of EVD, including therapies currently under evaluation for SUDV.

A novel feature selection algorithm for identifying hub genes in lung cancer.

Lung cancer, a life-threatening disease primarily affecting lung tissue, remains a significant contributor to mortality in both developed and developing nations. Accurate biomarker identification is imperative for effective cancer diagnosis and therapeutic strategies. This study introduces the Voting-Based Enhanced Binary Ebola Optimization Search Algorithm (VBEOSA), an innovative ensemble-based approach combining binary optimization and the Ebola optimization search algorithm. VBEOSA harnesses the collective power of the state-of-the-art classification models through soft voting. Moreover, our research applies VBEOSA to an extensive lung cancer gene expression dataset obtained from TCGA, following essential preprocessing steps including outlier detection and removal, data normalization, and filtration. VBEOSA aids in feature selection, leading to the discovery of key hub genes closely associated with lung cancer, validated through comprehensive protein-protein interaction analysis. Notably, our investigation reveals ten significant hub genes-ADRB2, ACTB, ARRB2, GNGT2, ADRB1, ACTG1, ACACA, ATP5A1, ADCY9, and ADRA1B-each demonstrating substantial involvement in the domain of lung cancer. Furthermore, our pathway analysis sheds light on the prominence of strategic pathways such as salivary secretion and the calcium signaling pathway, providing invaluable insights into the intricate molecular mechanisms underpinning lung cancer. We also utilize the weighted gene co-expression network analysis (WGCNA) method to identify gene modules exhibiting strong correlations with clinical attributes associated with lung cancer. Our findings underscore the efficacy of VBEOSA in feature selection and offer profound insights into the multifaceted molecular landscape of lung cancer. Finally, we are confident that this research has the potential to improve diagnostic capabilities and further enrich our understanding of the disease, thus setting the stage for future advancements in the clinical management of lung cancer. The VBEOSA source codes is publicly available at https://github.com/TEHNAN/VBEOSA-A-Novel-Feature-Selection-Algorithm-for-Identifying-hub-Genes-in-Lung-Cancer .

Regulation of Ebola GP conformation and membrane binding by the chemical environment of the late endosome.

Interaction between the Ebola virus envelope glycoprotein (GP) and the endosomal membrane is an essential step during virus entry into the cell. Acidic pH and Ca2+ have been implicated in mediating the GP-membrane interaction. However, the molecular mechanism by which these environmental factors regulate the conformational changes that enable engagement of GP with the target membrane is unknown. Here, we apply fluorescence correlation spectroscopy (FCS) and single-molecule Förster resonance energy transfer (smFRET) imaging to elucidate how the acidic pH, Ca2+ and anionic phospholipids in the late endosome promote GP-membrane interaction, thereby facilitating virus entry. We find that bis(monoacylglycero)phosphate (BMP), which is specific to the late endosome, is especially critical in determining the Ca2+-dependence of the GP-membrane interaction. Molecular dynamics (MD) simulations suggested residues in GP that sense pH and induce conformational changes that make the fusion loop available for insertion into the membrane. We similarly confirm residues in the fusion loop that mediate GP's interaction with Ca2+, which likely promotes local conformational changes in the fusion loop and mediates electrostatic interactions with the anionic phospholipids. Collectively, our results provide a mechanistic understanding of how the environment of the late endosome regulates the timing and efficiency of virus entry.

Markers of antroponotic viral infections in vervet monkeys arrived from their natural habitat (Tanzania).

INTRODUCTION: Various human viruses have been identified in wild monkeys and in captive primates. Cases of transmission of viruses from wild monkeys to humans and vice versa are known. The aim of this study was to identify markers of anthroponotic viral infections in vervet monkeys (Chlorocebus pygerythrus) arrived from their natural habitat (Tanzania). MATERIALS AND METHODS: Fecal samples (n = 56) and blood serum samples (n = 75) obtained from 75 animals, respectively, on days 10 and 23 after admission to the primate center, were tested for the markers of anthroponotic viral infections (Ebola virus, Marburg virus, lymphocytic choriomeningitis, hepatitis C virus, herpes simplex virus (HSV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), parainfluenza types 1 and 3, intestinal adenoviruses, rotaviruses) by enzyme immunoassay (ELISA) and polymerase chain reaction (PCR). RESULTS AND DISCUSSION: Among the examined animals, markers of 6 out of 11 tested viral infections were identified. Detection rates of IgG antibodies to HSV-1,2 (15.9%) and CMV (15.9%) were two times as low as IgG antibodies to EBV (31.8%). Among the markers of respiratory viral infections, IgG antibodies to parainfluenza virus type 1 were found (6.8%). 14.3% of the animals had rotavirus antigen, and 94% had simian adenovirus DNA. Markers of hemorrhagic fevers Ebola, Marburg, LCM, hepatitis C, and type 3 parainfluenza were not detected. CONCLUSION: When importing monkeys from different regions of the world, an expanded screening for viral infections is needed considering the epidemiological situation both in the country of importation and in the country of destination.

Safety and immunogenicity of an Ad26.ZEBOV booster vaccine in Human Immunodeficiency Virus positive (HIV+) adults previously vaccinated with the Ad26.ZEBOV, MVA-BN-Filo vaccine regimen against Ebola: A single-arm, open-label Phase II clinical trial in Kenya and Uganda.

BACKGROUND: People living with HIV constitute an important part of the population in regions at risk of Ebola virus disease outbreaks. The two-dose Ad26.ZEBOV, MVA-BN-Filo Ebola vaccine regimen induces strong immune responses in HIV-positive (HIV+) adults but the durability of this response is unknown. It is also unclear whether this regimen can establish immune memory to enable an anamnestic response upon re-exposure to antigen. METHODS: This paper describes an open-label, phase 2 trial, conducted in Kenya and Uganda, of Ad26.ZEBOV booster vaccination in HIV+ participants who had previously received the Ad26.ZEBOV, MVA-BN-Filo primary regimen. HIV+ adults with well-controlled infection and on highly active antiretroviral therapy were enrolled, vaccinated with booster, and followed for 28 days. The primary objectives were to assess Ad26.ZEBOV booster safety and antibody responses against the Ebola virus glycoprotein using the Filovirus Animal Non-Clinical Group ELISA. RESULTS: The Ad26.ZEBOV booster was well-tolerated in HIV+ adults with mostly mild to moderate symptoms. No major safety concerns or serious adverse events were reported. Four and a half years after the primary regimen, 24/26 (92 %) participants were still classified as responders, with a pre-booster antibody geometric mean concentration (GMC) of 726 ELISA units (EU)/mL (95 %CI 447-1179). Seven days after the booster, the GMC increased 54-fold to 38,965 EU/mL (95 %CI 23532-64522). Twenty-one days after the booster, the GMC increased 176-fold to 127,959 EU/mL (95 %CI 93872-174422). The responder rate at both post-booster time points was 100 %. CONCLUSIONS: The Ad26.ZEBOV booster is safe and highly immunogenic in HIV+ adults with well-controlled infection. The Ad26.ZEBOV, MVA-BN-Filo regimen can generate long-term immune memory persisting for at least 4·5 years, resulting in a robust anamnestic response. TRIAL REGISTRATION: Pan African Clinical Trial Registry (PACTR202102747294430). CLINICALTRIALS: gov (NCT05064956).

Blocking of ebolavirus spread through intercellular connections by an MPER-specific antibody depends on BST2/tetherin.

Ebola virus (EBOV) and Bundibugyo virus (BDBV) belong to the family Filoviridae and cause a severe disease in humans. We previously isolated a large panel of monoclonal antibodies from B cells of human survivors from the 2007 Uganda BDBV outbreak, 16 survivors from the 2014 EBOV outbreak in the Democratic Republic of the Congo, and one survivor from the West African 2013-2016 EBOV epidemic. Here, we demonstrate that EBOV and BDBV are capable of spreading to neighboring cells through intercellular connections in a process that depends upon actin and T cell immunoglobulin and mucin 1 protein. We quantify spread through intercellular connections by immunofluorescence microscopy and flow cytometry. One of the antibodies, BDBV223, specific to the membrane-proximal external region, induces virus accumulation at the plasma membrane. The inhibiting activity of BDBV223 depends on BST2/tetherin.

Depletion of Bone Marrow Hematopoietic Cells in Ebolavirus-Infected Rhesus Macaques: A Possible Cause of Hematologic Abnormalities in Ebolavirus Disease.

The pathophysiology of long-recognized hematologic abnormalities in Ebolavirus (EBOV) disease (EVD) is unknown. From limited human sampling (of peripheral blood), it has been postulated that emergency hematopoiesis plays a role in severe EVD, but the systematic characterization of the bone marrow (BM) has not occurred in human disease or in nonhuman primate models. In a lethal rhesus macaque model of EVD, 18 sternal BM samples exposed to the Kikwit strain of EBOV were compared to those from uninfected controls (n = 3). Immunohistochemistry, RNAscope in situ hybridization, transmission electron microscopy, and confocal microscopy showed that EBOV infects BM monocytes/macrophages and megakaryocytes. EBOV exposure was associated with severe BM hypocellularity, including depletion of myeloid, erythroid, and megakaryocyte hematopoietic cells. These depletions were negatively correlated with cell proliferation (Ki67 expression) and were not associated with BM apoptosis during disease progression. In EBOV-infected rhesus macaques with terminal disease, BM showed marked hemophagocytosis, megakaryocyte emperipolesis, and the release of immature hematopoietic cells into the sinusoids. Collectively, these data demonstrate not only direct EBOV infection of BM monocytes/macrophages and megakaryocytes but also that disease progression is associated with hematopoietic failure, notably in peripheral cytopenia. These findings inform current pathophysiologic unknowns and suggest a crucial role for BM dysfunction and/or failure, including emergency hematopoiesis, as part of the natural history of severe human disease.

Safety, tolerability, and immunogenicity of the Ebola Sudan chimpanzee adenovirus vector vaccine (cAd3-EBO S) in healthy Ugandan adults: a phase 1, open-label, dose-escalation clinical trial.

BACKGROUND: Sudan Ebola virus can cause severe viral disease, with an average case fatality rate of 54%. A recent outbreak of Sudan Ebola virus in Uganda caused 55 deaths among 164 confirmed cases in the second half of 2022. Although vaccines and therapeutics specific for Zaire Ebola virus have been approved for use during outbreak situations, Sudan Ebola virus is an antigenically distinct virus with no approved vaccines available. METHODS: In this phase 1, open-label, dose-escalation trial we evaluated the safety, tolerability, and immunogenicity of a monovalent chimpanzee adenovirus 3 vaccine against Sudan Ebola virus (cAd3-EBO S) at Makerere University Walter Reed Project in Kampala, Uganda. Study participants were recruited from the Kampala metropolitan area using International Review Board-approved written and electronic media explaining the trial intervention. Healthy adults without previous receipt of Ebola, Marburg, or cAd3 vectored-vaccines were enrolled to receive cAd3-EBO S at either 1 × 1010 or 1 × 1011 particle units (PU) in a single intramuscular vaccination and were followed up for 48 weeks. Primary safety and tolerability endpoints were assessed in all vaccine recipients by reactogenicity for the first 7 days, adverse events for the first 28 days, and serious adverse events throughout the study. Secondary immunogenicity endpoints included evaluation of binding antibody and T-cell responses against the Sudan Ebola virus glycoprotein, and neutralising antibody responses against the cAd3 vector at 4 weeks after vaccination. This study is registered with ClinicalTrials.gov, NCT04041570, and is completed. FINDINGS: 40 healthy adults were enrolled between July 22 and Oct 1, 2019, with 20 receiving 1 × 1010 PU and 20 receiving 1 × 1011 PU of cAd3-EBO S. 38 (95%) participants completed all follow-up visits. The cAd3-EBO S vaccine was well tolerated with no severe adverse events. The most common reactogenicity symptoms were pain or tenderness at the injection site (34 [85%] of 40), fatigue (29 [73%] of 40), and headache (26 [65%] of 40), and were mild to moderate in severity. Positive responses for glycoprotein-specific binding antibodies were induced by 2 weeks in 31 (78%) participants, increased to 34 (85%) participants by 4 weeks, and persisted to 48 weeks in 31 (82%) participants. Most participants developed glycoprotein-specific T-cell responses (20 [59%, 95% CI 41-75] of 34; six participants were removed from the T cell analysis after failing quality control parameters) by 4 weeks after vaccination, and neutralising titres against the cAd3 vector were also increased from baseline (90% inhibitory concentration of 47, 95% CI 30-73) to 4 weeks after vaccination (196, 125-308). INTERPRETATION: The cAd3-EBO S vaccine was safe at both doses, rapidly inducing immune responses in most participants after a single injection. The rapid onset and durability of the vaccine-induced antibodies make this vaccine a strong candidate for emergency deployment in Sudan Ebola virus outbreaks. FUNDING: National Institutes of Health via interagency agreement with Walter Reed Army Institute of Research.

Automatic detection and classification of lung cancer CT scans based on deep learning and ebola optimization search algorithm.

Recently, research has shown an increased spread of non-communicable diseases such as cancer. Lung cancer diagnosis and detection has become one of the biggest obstacles in recent years. Early lung cancer diagnosis and detection would reliably promote safety and the survival of many lives globally. The precise classification of lung cancer using medical images will help physicians select suitable therapy to reduce cancer mortality. Much work has been carried out in lung cancer detection using CNN. However, lung cancer prediction still becomes difficult due to the multifaceted designs in the CT scan. Moreover, CNN models have challenges that affect their performance, including choosing the optimal architecture, selecting suitable model parameters, and picking the best values for weights and biases. To address the problem of selecting optimal weight and bias combination required for classification of lung cancer in CT images, this study proposes a hybrid metaheuristic and CNN algorithm. We first designed a CNN architecture and then computed the solution vector of the model. The resulting solution vector was passed to the Ebola optimization search algorithm (EOSA) to select the best combination of weights and bias to train the CNN model to handle the classification problem. After thoroughly training the EOSA-CNN hybrid model, we obtained the optimal configuration, which yielded good performance. Experimentation with the publicly accessible Iraq-Oncology Teaching Hospital / National Center for Cancer Diseases (IQ-OTH/NCCD) lung cancer dataset showed that the EOSA metaheuristic algorithm yielded a classification accuracy of 0.9321. Similarly, the performance comparisons of EOSA-CNN with other methods, namely, GA-CNN, LCBO-CNN, MVO-CNN, SBO-CNN, WOA-CNN, and the classical CNN, were also computed and presented. The result showed that EOSA-CNN achieved a specificity of 0.7941, 0.97951, 0.9328, and sensitivity of 0.9038, 0.13333, and 0.9071 for normal, benign, and malignant cases, respectively. This confirms that the hybrid algorithm provides a good solution for the classification of lung cancer.

Ebola Virus Disease Features Hemophagocytic Lymphohistiocytosis/Macrophage Activation Syndrome in the Rhesus Macaque Model.

BACKGROUND: Ebola virus (EBOV) disease (EVD) is one of the most severe and fatal viral hemorrhagic fevers and appears to mimic many clinical and laboratory manifestations of hemophagocytic lymphohistiocytosis syndrome (HLS), also known as macrophage activation syndrome. However, a clear association is yet to be firmly established for effective host-targeted, immunomodulatory therapeutic approaches to improve outcomes in patients with severe EVD. METHODS: Twenty-four rhesus monkeys were exposed intramuscularly to the EBOV Kikwit isolate and euthanized at prescheduled time points or when they reached the end-stage disease criteria. Three additional monkeys were mock-exposed and used as uninfected controls. RESULTS: EBOV-exposed monkeys presented with clinicopathologic features of HLS, including fever, multiple organomegaly, pancytopenia, hemophagocytosis, hyperfibrinogenemia with disseminated intravascular coagulation, hypertriglyceridemia, hypercytokinemia, increased concentrations of soluble CD163 and CD25 in serum, and the loss of activated natural killer cells. CONCLUSIONS: Our data suggest that EVD in the rhesus macaque model mimics pathophysiologic features of HLS/macrophage activation syndrome. Hence, regulating inflammation and immune function might provide an effective treatment for controlling the pathogenesis of acute EVD.

COVID-19 vaccines and the pandemic: lessons learnt for other neglected diseases and future threats.

Through the experiences gained by accelerating new vaccines for both Ebola virus infection and COVID-19 in a public health emergency, vaccine development has benefited from a 'multiple shots on goal' approach to new vaccine targets. This approach embraces simultaneous development of candidates with differing technologies, including, when feasible, vesicular stomatitis virus or adenovirus vectors, messenger RNA (mRNA), whole inactivated virus, nanoparticle and recombinant protein technologies, which led to multiple effective COVID-19 vaccines. The challenge of COVID-19 vaccine inequity, as COVID-19 spread globally, created a situation where cutting-edge mRNA technologies were preferentially supplied by multinational pharmaceutical companies to high-income countries while low and middle-income countries (LMICs) were pushed to the back of the queue and relied more heavily on adenoviral vector, inactivated virus and recombinant protein vaccines. To prevent this from occurring in future pandemics, it is essential to expand the scale-up capacity for both traditional and new vaccine technologies at individual or simultaneous hubs in LMICs. In parallel, a process of tech transfer of new technologies to LMIC producers needs to be facilitated and funded, while building LMIC national regulatory capacity, with the aim of several reaching 'stringent regulator' status. Access to doses is an essential start but is not sufficient, as healthcare infrastructure for vaccination and combating dangerous antivaccine programmes both require support. Finally, there is urgency to establish an international framework through a United Nations Pandemic Treaty to promote, support and harmonise a more robust, coordinated and effective global response.

Sphingosine Kinases Promote Ebola Virus Infection and Can Be Targeted to Inhibit Filoviruses, Coronaviruses, and Arenaviruses Using Late Endocytic Trafficking to Enter Cells.

Entry of enveloped viruses in host cells requires the fusion of viral and host cell membranes, a process that is facilitated by viral fusion proteins protruding from the viral envelope. These viral fusion proteins need to be triggered by host factors, and for some viruses, this event occurs inside endosomes and/or lysosomes. Consequently, these 'late-penetrating viruses' must be internalized and delivered to entry-conducive intracellular vesicles. Because endocytosis and vesicular trafficking are tightly regulated cellular processes, late-penetrating viruses also depend on specific host proteins for efficient delivery to the site of fusion, suggesting that these could be targeted for antiviral therapy. In this study, we investigated a role for sphingosine kinases (SKs) in viral entry and found that chemical inhibition of sphingosine kinase 1 (SK1) and/or SK2 and knockdown of SK1/2 inhibited entry of Ebola virus (EBOV) into host cells. Mechanistically, inhibition of SK1/2 prevented EBOV from reaching late-endosomes and lysosomes that contain the EBOV receptor, Niemann Pick C1 (NPC1). Furthermore, we present evidence that suggests that the trafficking defect caused by SK1/2 inhibition occurs independently of sphingosine-1-phosphate (S1P) signaling through cell-surface S1P receptors. Lastly, we found that chemical inhibition of SK1/2 prevents entry of other late-penetrating viruses, including arenaviruses and coronaviruses, and inhibits infection by replication-competent EBOV and SARS-CoV-2 in Huh7.5 cells. In sum, our results highlight an important role played by SK1/2 in endocytic trafficking, which can be targeted to inhibit entry of late-penetrating viruses and could serve as a starting point for the development of broad-spectrum antiviral therapeutics.

The Ebola virus VP40 matrix layer undergoes endosomal disassembly essential for membrane fusion.

Ebola viruses (EBOVs) assemble into filamentous virions, whose shape and stability are determined by the matrix viral protein 40 (VP40). Virus entry into host cells occurs via membrane fusion in late endosomes; however, the mechanism of how the remarkably long virions undergo uncoating, including virion disassembly and nucleocapsid release into the cytosol, remains unknown. Here, we investigate the structural architecture of EBOVs entering host cells and discover that the VP40 matrix disassembles prior to membrane fusion. We reveal that VP40 disassembly is caused by the weakening of VP40-lipid interactions driven by low endosomal pH that equilibrates passively across the viral envelope without a dedicated ion channel. We further show that viral membrane fusion depends on VP40 matrix integrity, and its disassembly reduces the energy barrier for fusion stalk formation. Thus, pH-driven structural remodeling of the VP40 matrix acts as a molecular switch coupling viral matrix uncoating to membrane fusion during EBOV entry.

2- and 3-Fluoro-3-deaza-1',6'-isoneplanocin: Synthesis and antiviral properties (including Ebola and Marburg).

To extend the antiviral properties of 2- and 3-fluoro-3-deazaneplanocins into the evolving 3-deaza-1',6'-isoneplanocin library, 2- (11) and 3-fluoro-1',6'-iso-3-deazaneplanocin A (12) have been explored. The requisite synthesis began with an Ullmann reaction by coupling of a protected cyclopentenyl iodide with either 2-fluoro- or 3-fluoro-3-deazaadenine. Target 12 displayed significant activity towards 5 viruses (µM): H1N1 (EC50 < 0.36, CC50 > 357, SI > 1000), hepatitis B virus (EC50 1.28, CC50 > 357, SI > 279), norovirus (EC50 0.64, CC50 > 357, SI > 558), Ebola (EC50 < 0.1, CC50 > 100, SI > 1000), and Marburg (EC50 < 0.1, CC50 > 100, SI > 1000). On the other hand, while 11 showed limited antiviral effects, its toxicity was significant, precluding any further usefulness.