Current updates on the epidemiology,pathogenesis and development of small molecule therapeutics for the treatment of Ebola virus infections

Ebola virus disease(EVD)is a rare,highly contagious and a deadly disease with a variable fatality rate ranging from 30%to 90%.Over the past two decades,Ebola pandemic has severely affected the sub-Sahara region including Democratic Republic of the Congo(DRC),and Uganda.The causative agents of the most EVD cases are three distinct species out of six Ebolaviruses namely Zaire Ebolavirus(ZEBOV),Sudan Ebolavirus(SUDV)and Bundibugyo Ebolavirus(BDBV).In recent years,significant strides have been made in therapeutic interventions.Notably,the US Food and Drug Administration has approved two monoclonal antibodies:InmazebTM(REGN-EB3)and Ansuvimab or EbangaTM.Additionally,many small molecules are currently in the developmental stage,promising further progress in medical treatment.Addressing the critical need for preventive measures,this review provides an in-depth analysis of the licensed Ebola vaccines-Ervebo and the combination of Zabdeno(Ad26.ZEBOV)and Mvabea(MVA-BN-Filo)as well as the vaccines which are currently being tested for their efficacy and safety in clinical studies.These vaccines might play an important role in curbing the spread and mitigating the impact of this lethal disease.The current treatment landscape for EVD encompasses both nutritional(supportive)and drug therapies.The review comprehensively details the origin,pathogenesis,and epidemiology of EVD,shedding light on the ongoing efforts to combat this devastating disease.It explores small molecules in various stages of the development,discusses patents filed or granted,and delves into the clinical and supportive therapies that form the cornerstone of EVD management.This review aims to provide the recent developments made in the design and synthesis of small molecules for scientific community to facilitate a deeper understanding of the disease and fostering the development of effective strategies for prevention,treatment,and control of EVD.

Global Epidemic of Ebola Virus Disease and the Importation Risk into China: An Assessment Based on the Risk Matrix Method

Objective To analyze the global epidemic status of the Ebola virus disease(EVD) and assess the importation risk into China.Methods Data from World Health Organization reports were used. We described the global epidemic status of EVD from 1976–2021, and assessed and ranked the importation risk of EVD from the diseaseoutbreaking countries into China using the risk matrix and Borda count methods, respectively.Results From 1976–2021, EVD mainly occurred in western and central Africa, with the highest cumulative number of cases(14,124 cases) in Sierra Leone, and the highest cumulative fatality rate(85%) in the Congo. Outbreaks of EVD have occurred in the Democratic Republic of the Congo and Guinea since 2018. The importation risk into China varies across countries with outbreaks of disease.The Democratic Republic of the Congo had an extremely high risk(23 Borda points), followed by Guinea and Liberia. Countries with a moderate importation risk were Nigeria, Uganda, Congo, Sierra Leone,Mali, and Gabon, while countries with a low importation risk included Sudan, Senegal, and Co te d’Ivoire.Conclusion China is under the risk of EVD importation with the globalization and severe epidemic status of EVD. Key attention need to be paid to the Democratic Republic of the Congo, Guinea, and Liberia. Therefore, it is necessary to prevent and prepare in advance for importation risk in China.

Ebola Virus Disease: General Characteristics, Thoughts, and Perspectives

In December 2013, a new round of Ebola virus disease （EVD） first occurred in a remote countryside of Guinea and then spread in Guinea, Liberia, Sierra Leone, and Nigeria of West Africa. EVD, caused by Ebolavirus and previously known as Ebola hemorrhagic fever, is an acute infectious disease with fatality rates up to 90%. As of August 22, 2014, the number of suspected and confirmed cases was 2615, causing 1427 deaths[I]. On August 8, 2014, World Health Organization announced the current outbreak in West Africa as an international public health emergency. The global epidemic tendency remains ambiguous to date. In recent years, China closely collaborates with West Africa in labor, business, overseas education, and also sends aid medical team there. Thus, the risk of importing the disease cannot be ignored. We conduct this literature review of epidemiology, pathogen, prophylaxis, and treatment to provide evidence for controlling the risk and carrying out effective interventions.

Ebola virus disease: From epidemiology to prophylaxis

The outbreak of Ebola virus disease(EVD) continues to spread through West Africa. Since the first reported EVD in March 2014, the number of cases has increased rapidly, with the fatality rate of >50%. The most prevalent Ebola virus belongs to the species of Zaire ebolavirus, with a mortality rate as high as 90%. Although there were introduced cases in other continents, Africa is the endemic area where fruit bats and apes are suspected to be Ebola virus carriers. The virus might be transmitted from the host animals to humans if humans consume relative raw and contaminated meats; however, human-to-human transmission via close contact is the major route of current outbreaks. EVD happens at any seasons and affected people of any race in any age groups. Direct contact with body fluids of EVD patients and living in the contaminated environment greatly increase the risk of being infected. Transmission viaaerosol is less possible but the transmission via droplet is possible in humans. Thus, health care providers are facing danger of getting Ebola virus infection. So far, there are limited vaccines, drugs and/or therapies to prevent Ebola virus infection or treat EVD. Medical workers should follow the current standard prophylactic procedures. Military forces can orchestrate efficient care to mass EVD casualties. Although it is necessary to speed up the pace of developing effective vaccine and therapeutics for the prevention and treatment of EVD, public health prophylaxis is the most important issue at present to control the spread of this disease cost-effectively.

The Ebola virus:a review of progress and development in research

The Ebola virus was identified in the year 1976 and has caused periodic outbreaks in West African countries.The disease has a case fatality rate up to 90%.Ebola has been classified as a biosafety level four pathogen and there is no currently approved vaccine or treatment for the virus.However,remarkable progress has been demonstrated by researchers in understanding the pathogenicity of the Ebola virus.Several animal models have been cultivated to develop diagnostics,vaccines and therapeutic drugs.

Detection and Analysis of Ebola Virus in Sierra Leone-China Friendship Biosafety Laboratory from March 11 to April 20, 2015

Ebola virus disease reemerged in Western Africa in 2014.Chinese Center for Disease Control and Prevention dispatched the first Ebola virus（EBOV）detection team to run newly established Sierra Leone-China Friendship Biological Safety Laboratory.The aims of study were to understand epidemiology,clinical manifestations and survival time of EBOV in patient＇s blood.A total of 913specimens were tested between March 11 and April20, 2015. EBOV positivity occurred in 7.37% of the blood and 0.53% in throat swabs.

Identification of active pocket and protein druggability within envelope glycoprotein GP2 from Ebola virus

The drug searching for combating the present outbreak of Ebola virus infection is the urgent activity at present.Finding the new effective drug at present must base on the molecular analysis of the pathogenic virus.The in-depth analysis of the viral protein to find the binding site,active pocket is needed.Here,the authors analyzed the envelope glycoprotein GP2 from Ebola virus.Identification of active pocket and protein draggability within envelope glycoprotein GP2 from Ebola virus was done.According to this assessment,7 active pockets with varied draggability could be identified.

Synthetic Biology Construct of Ebola Virus in Bacteria Surrogate Is Stable and Safe for Rapid Detection Studies in a BSL-2 Laboratory Setting

Rapid detection of virulent pathogens during an outbreak is critical for public health advisories and control of the disease in a population. While many molecular techniques for point of care and clinical diagnosis abound, the US experience with the COVID-19 testing in the early stages of the pandemic underscores the critical importance of determining the appropriate target gene(s) with in-built controls that reliably detect pathogens with high sensitivity and specificity. Assays and research for diagnostics and therapy could be slowed during an epidemic because access to the required BSL-3 and BSL-4 laboratories are limited. So, during the 2014 West Africa Ebola outbreak, we tested the hypothesis that using synthetic cDNA of Ebolavirus in a bacteria surrogate (fit for all lab settings), would remain unmutated and safe after several generations, serving as an effective positive control in research settings, self test and point-of-care detection platforms. Primers were designed for the detection and quantification of the nucleoprotein (NP) gene of the 2014 Makona Ebola strain (KR781608.1, 733 - 1332 bp). To test the stability of artificially inserted translation arrest in the Orf of the model gene, it was edited to include three STOP codons in the RNA transcript using SNAP GENE. The segment was then spliced into a high copy number plasmid, cloned into One ShotTM TOP10 Escherichia coli (Invitrogen), and tested for stability and safety by periodic subculture, extraction and sequencing. Unlike COVID-19, rapid detection of blood-borne etiologies like Ebola requires optimized protocols for blood matrix. Using real-time PCR and newly designed primer pairs, the EBOV surrogate was detected and enumerated in human blood and regular broth and buffers. Based on aligned sequence analysis, the EBOV synthetic NP gene was stable (>99.9999% similarity coefficient) for at least 3 months. Detection sensitivity in broth and blood was at least 100 cells/ml or about 5.8 × 103 to 7.3 × 103 virion equivalents per ml. While the developments of transcription-and-replication-competent virus like particles (trVLP) have made it possible to study the infection and replication cycles of virulent pathogens in BSL-2 laboratories, the simplicity of our model and the reproducibility of detection and enumeration show the utility of synthetic bio-components as positive controls for point of care diagnostic tools. The inserted stop codons remained intact after many generations, suggesting that expressed virulent proteins can be easily silenced in synthetic biology models for research in BSL-1 and 2 and a wide range of pathogens. Synthetic bio-components can thereby aid further research by reducing costs and improving safety for workers and stakeholders.

Establishment and application of a surrogate model for human Ebola virus disease in BSL-2 laboratory

The Ebola virus(EBOV)is a member of the Orthoebolavirus genus,Filoviridae family,which causes severe hemorrhagic diseases in humans and non-human primates(NHPs),with a case fatality rate of up to 90%.The development of countermeasures against EBOV has been hindered by the lack of ideal animal models,as EBOV requires handling in biosafety level(BSL)-4 facilities.Therefore,accessible and convenient animal models are urgently needed to promote prophylactic and therapeutic approaches against EBOV.In this study,a recombinant vesicular stomatitis virus expressing Ebola virus glycoprotein(VSV-EBOV/GP)was constructed and applied as a surrogate virus,establishing a lethal infection in hamsters.Following infection with VSV-EBOV/GP,3-week-old female Syrian hamsters exhibited disease signs such as weight loss,multi-organ failure,severe uveitis,high viral loads,and developed severe systemic diseases similar to those observed in human EBOV patients.All animals succumbed at 2–3 days post-infection(dpi).Histopathological changes indicated that VSV-EBOV/GP targeted liver cells,suggesting that the tissue tropism of VSV-EBOV/GP was comparable to wild-type EBOV(WT EBOV).Notably,the pathogenicity of the VSV-EBOV/GP was found to be species-specific,age-related,gender-associated,and challenge route-dependent.Subsequently,equine anti-EBOV immunoglobulins and a subunit vaccine were validated using this model.Overall,this surrogate model represents a safe,effective,and economical tool for rapid preclinical evaluation of medical countermeasures against EBOV under BSL-2 conditions,which would accelerate technological advances and breakthroughs in confronting Ebola virus disease.

Ebola virus VP35 perturbs type I interferon signaling to facilitate viral replication

As one of the deadliest viruses,Ebola virus(EBOV)causes lethal hemorrhagic fevers in humans and nonhuman primates.The suppression of innate immunity leads to robust systemic virus replication of EBOV,leading to enhanced transmission.However,the mechanism of EBOV-host interaction is not fully understood.Here,we identified multiple dysregulated genes in early stage of EBOV infection through transcriptomic analysis,which are highly clustered to Jak-STAT signaling.EBOV VP35 and VP30 were found to inhibit type I interferon(IFN)signaling.Moreover,exogenous expression of VP35 blocks the phosphorylation of endogenous STAT1,and suppresses nuclear translocation of STAT1.Using serial truncated mutations of VP35,N-terminal 1–220amino acid residues of VP35 were identified to be essential for blocking on type I IFN signaling.Remarkably,VP35 of EBOV suppresses type I IFN signaling more efficiently than those of Bundibugyo virus(BDBV)and Marburg virus(MARV),resulting in stable replication to facilitate the pathogenesis.Altogether,this study enriches understanding on EBOV evasion of innate immune response,and provides insights into the interplay between filoviruses and host.

The potential epidemic threat of Ebola virus and the development of a preventive vaccine

Ebola virus(EBOV)is classified as a category A pathogen as it causes viral hemorrhagic fever,one of the most-deadly virus-related diseases.Since its discovery in 1976,EBOV has caused a number of global public health incidents,which have posed a serious threat to both humans and non-human primates.Thus,numerous preventive vaccine studies are underway,including research on inactivated vaccines,DNA vaccines,subunit vaccines,virus-like particles,Venezuelan equine encephalitis virus replicon particles,and several viral vector vaccines.The vesicular stomatitis virus-based vaccine Ervebo was recently approved by the Food and Drug Administration and the European Union,and several other vaccines have also been proven to confer potent protection in non-human primates against EBOV lethal challenge.This review provides a brief background of EBOV,with a focus on the epidemiology,available animal models,and advances in preventive approaches for EBOV infection.

Human Ebola virus infection in West Africa: a review of available therapeutic agents that target different steps of the life cycle of Ebola virus

The recent outbreak of the human Zaire ebolavirus(EBOV)epidemic is spiraling out of control in West Africa.Human EBOV hemorrhagic fever has a case fatality rate of up to 90%.The EBOV is classified as a biosafety level 4 pathogen and is considered a category A agent of bioterrorism by Centers for Disease Control and Prevention,with no approved therapies and vaccines available for its treatment apart from supportive care.Although several promising therapeutic agents and vaccines against EBOV are undergoing the Phase I human trial,the current epidemic might be outpacing the speed at which drugs and vaccines can be produced.Like all viruses,the EBOV largely relies on host cell factors and physiological processes for its entry,replication,and egress.We have reviewed currently available therapeutic agents that have been shown to be effective in suppressing the proliferation of the EBOV in cell cultures or animal studies.Most of the therapeutic agents in this review are directed against non-mutable targets of the host,which is independent of viral mutation.These medications are approved by the Food and Drug Administration(FDA)for the treatment of other diseases.They are available and stockpileable for immediate use.They may also have a complementary role to those therapeutic agents under development that are directed against the mutable targets of the EBOV.

The perspective of gender on the Ebola virus using a risk management and population health framework:a scoping review

Background:In the three decades since the first reported case of Ebola virus,most known index cases have been consistently traced to the hunting of“bush meat”,and women have consistently recorded relatively high fatality rates in most catastrophic outbreaks.This paper discusses Ebola-related risk factors,which constantly interact with cultural values,and provides an insight into the link between gender and the risk of contracting infectious diseases,using Ebola virus as an example within Africa.Method:A comprehensive search of the literature was conducted using the PubMed,Ovid Medline and Global Health CABI databases as well as CAB Abstracts,including gray literature.We used a descriptive and sex-and gender-based analysis to revisit previous studies on Ebola outbreaks since 1976 to 2014,and disaggregated the cases and fatality rates according to gender and the sources of known index cases based on available data.Results:In total,approximately 1530 people died in all previous Ebola outbreaks from 1976 to 2012 compared with over 11,310 deaths from the 2014 outbreak.Women’s increased exposure can be attributed to time spent at home and their responsibility for caring for the sick,while men’s increased vulnerability to the virus can be attributed to their responsibility for caring for livestock and to time spent away from home,as most known sources of the index cases have been infected in the process of hunting.We present a conceptual model of a circle of interacting risk factors for Ebola in the African context.Conclusion:There is currently no evidence related to biological differences in female or male sex that increases Ebola virus transmission and vulnerability;rather,there are differences in the level of exposure between men and women.Gender is therefore an important risk factor to consider in the design of health programs.Building the capacity for effective risk communication is a worthwhile investment in public and global health for future emergency responses.

Clinical presentations and outcomes of patients with Ebola virus disease in Freetown, Sierra Leone

Background:Clinical and laboratory data were collected and analysed from patients with Ebola virus disease(EVD)in Jui Government Hospital in Freetown,Sierra Leone,where patients with EVD were received and/or treated from October 1,2014 to March 21,2015 during the West Africa EVD outbreak.Methods:The study admitted 285 patients with confirmed EVD and followed them up till the endpoint(recovery or death).EVD was confirmed by quantitative RT-PCR assays detecting blood Ebola virus(EBOV).Results:Among the 285 lab-confirmed EVD cases in Jui Government Hospital,146 recovered and 139 died,with an overall survival rate of 51.23%.Patients under the age of 6 years had a lower survival rate(37.50%).Most non-survivors(79.86%)died within 7 days after admission and the mean hospitalization time for non-survivors was 5.56±6.11 days.More than half survivors(63.69%)turned blood EBOV negative within 3 weeks after admission and the mean hospitalization time for survivors was 20.38±7.58 days.High blood viral load(≥106 copies/ml)was found to be predictive of the non-survival outcome as indicated by the Receiver Operating Characteristic(ROC)curve analysis.The probability of patients’survival was less than 15%when blood viral load was greater than 106 copies/ml.Multivariate analyses showed that blood viral load(P=0.005),confusion(P=0.010),abdominal pain(P=0.003),conjunctivitis(P=0.035),and vomiting(P=0.004)were factors independently associated with the outcomes of EVD patients.Conclusions:Most death occurred within 1 week after admission,and patients at the age of 6 or younger had a lower survival rate.Most surviving patients turned blood EBOV negative within 1–4 weeks after admission.Factors such as high blood viral load,confusion,abdominal pain,vomiting and conjunctivitis were associated with poor prognosis for EVD patients.

Hsa-miR-1246, hsa-miR-320a and hsa-miR-196b-5p inhibitors can reduce the cytotoxicity of Ebola virus glycoprotein in vitro

Ebola virus （EBOV） causes a highly lethal hemorrhagic fever syndrome in humans and has been associated with mortality rates of up to 91% in Zaire, the most lethal strain. Though the viral envelope glycoprotein （GP） mediates widespread inflammation and cellular damage, these changes have mainly focused on alterations at the protein level, the role of microRNAs （miRNAs） in the molecular pathogenesis underlying this lethal disease is not fully understood. Here, we report that the miRNAs hsa-miR-1246, hsa-miR-320a and hsa-miR-196b-5p were induced in human umbilical vein endothelial cells （HUVECs） following expression of EBOV GP. Among the proteins encoded by predicted targets of these miRNAs, the adhesion-related molecules tissue factor pathway inhibitor （TFPI）, dystroglycan! （DAG1） and the caspase 8 and FADD-like apoptosis regulator （CFLAR） were significantly downregulated in EBOV GP-expressing HUVECs. Moreover, inhibition of hsa-miR-1246, hsa-miR-320a and hsa-miR-196b-5p, or overexpression of TFPI, DAG1 and CFLAR rescued the cell viability that was induced by EBOV GP. Our results provide a novel molecular basis for EBOV pathogenesis and may contribute to the development of strategies to protect against future EBOV pandemics.

Insight into the Ebola virus nucleocapsid assembly mechanism： crystal structure of Ebola virus nucleoprotein core domain at 1.8 A resolution

Ebola virus （EBOV） is a key member of Filoviridae family and causes severe human infectious diseases with high morbidity and mortality. As a typical negative-sense single-stranded RNA （-ssRNA） viruses, EBOV possess a nucleocapsid protein （NP） to facilitate genomic RNA encapsidation to form viral ribonucleoprotein complex （RNP） together with genome RNA and polymerase, which plays the most essential role in virus proliferation cycle. However, the mechanism of EBOV RNP formation remains unclear. In this work, we solved the high resolution structure of core domain of EBOV NP. The polypeptide of EBOV NP core domain （NPcore） pos- sesses an N-lobe and C-lobe to clamp a RNA binding groove, presenting similarities with the structures of the other reported viral NPs encoded by the members from Mononegavirales order. Most strikingly, a hydrophobic pocket at the surface of the C-lobe is occupied by an a- helix of EBOV NPcore itself, which is highly conserved among filoviridae family. Combined with other bio- chemical and biophysical evidences, our results provides great potential for understanding the mechanism underlying EBOV RNP formation via the mobility of EBOV NP element and enables the development of antiviral therapies targeting EBOV RNP formation.

Identification of Ebola virus microRNAs and their putative pathological function

Ebola virus(EBOV),a member of the filovirus family,is an enveloped negative-sense RNA virus that causes lethal infections in humans and primates.Recently,more than 1000 people have been killed by the Ebola virus disease in Africa,yet no specific treatment or diagnostic tests for EBOV are available.In this study,we identified two putative viral microRNA precursors(pre-miRNAs)and three putative mature microRNAs(miRNAs)derived from the EBOV genome.The production of the EBOV miRNAs was further validated in HEK293T cells transfected with a pcDNA6.2-GW/EmGFP-EBOV-pre-miRNA plasmid,indicating that EBOV miRNAs can be produced through the cellular miRNA processing machinery.We also predicted the potential target genes of these EBOV miRNAs and their possible biological functions.Overall,this study reports for the first time that EBOV may produce miRNAs,which could serve as non-invasive biomarkers for the diagnosis and prognosis of EBOV infection and as therapeutic targets for Ebola viral infection treatment.

Possible FDA-approved drugs to treat Ebola virus infection

There is currently no effective treatment for the Ebola virus(EBOV)thus far.Most drugs and vaccines developed to date have not yet been approved for human trials.Two FDA-approved c-AbI1 tyrosine kinase inhibitors Gleevec and Tasigna block the release of viral particles;however,their clinical dosages are much lower than the dosages required for effective EBOV suppression.Anα-1,2-glucosidase inhibitor Miglustat has been shown to inhibit EBOV particle assembly and secretion.Additionally,the estrogen receptor modulators Clomiphene and Toremifene prevent membrane fusion of EBOV and 50-90%of treated mice survived after Clomiphene/Toremifene treatments.However,the uptake efficiency of Clomiphene by oral administration is very low.Thus,I propose a hypothetical treatment protocol to treat Ebola virus infection with a cumulative use of both Miglustat and Toremifene to inhibit the virus effectively and synergistically.EBOV infection induces massive apoptosis of peripheral lymphocytes.Also,cytolysis of endothelial cells triggers disseminated intravascular coagulation(DIC)and subsequent multiple organ failures.Therefore,blood transfusions and active treatments with FDA-approved drugs to treat DIC are also recommended.

Repurposing of berbamine hydrochloride to inhibit Ebola virus by targeting viral glycoprotein

Ebola virus(EBOV)infection leads to staggeringly high mortality rate.Effective and low-cost treatments are urgently needed to control frequent EBOV outbreaks in Africa.In this study,we report that a natural compound called berbamine hydrochloride strongly inhibits EBOV replication in vitro and in vivo.Our work further showed that berbamine hydrochloride acts by directly binding to the cleaved EBOV glycoprotein(GPcl),disrupting GPcl interaction with viral receptor Niemann-Pick C1,thus blocking the fusion of viral and cellular membranes.Our data support the probability of developing anti-EBOV small molecule drugs by targeting viral GPcl.More importantly,since berbamine hydrochloride has been used in clinic to treat leukopenia,it holds great promise of being quickly repurposed as an anti-EBOV drug.

Serological Investigation of Laboratory-Confirmed and Suspected Ebola Virus Disease Patients During the Late Phase of the Ebola Outbreak in Sierra Leone

This study aimed to investigate the serological characteristics of Ebola virus(EBOV) infection during the late phase of the Ebola outbreak in Sierra Leone. In total, 877 blood samples from 694 suspected Ebola virus disease(EVD) cases assessed from March to December 2015, were analyzed via real-time reverse transcription polymerase chain reaction(RT-PCR) for viral RNA and enzyme-linked immunosorbent assay(ELISA) and Luminex to detect antibodies against EBOV. Viral load and EBOV-specific IgM/IgG titers displayed a declining trend during March to December 2015. Viral RNA load decreased rapidly at earlier stages after disease onset, while EBOV-specific IgM and IgG still persisted in 58.1%(18/31) and 93.5%(29/31) of the confirmed EVD patients and in 3.8%(25/663) and 17.8%(118/663) of the RNA-negative suspected patients in the later phase, respectively. Dynamic analysis of longitudinally collected samples from eight EVD patients revealed typically reversed trends of declining viral load and increasing IgM and/or IgG titers in response to the EBOV infection.The present results indicate that certain populations of Sierra Leone developed immunity to an EBOV infection in the late phase of the outbreak, providing novel insights into the risk assessment of EBOV infections among human populations.