埃博拉病毒快速检测技术研究进展

埃博拉病毒(ebola virus,EBOV)是引起埃博拉病毒病(ebola hemorrhagic fever,EBHF)的病原体,属丝状病毒科。EBOV传染性强,致死率高;2014—2016年西非暴发埃博拉疫情共造成2.8万余人感染,1.1万余人死亡。早期、准确、灵敏的EBOV快速检测技术,可降低EBOV的传播风险。现从核酸检测及蛋白质检测技术两方面对EBOV快速检测的研究进展作一综述。     

SYBR Green Ⅰ荧光定量RT-PCR检测埃博拉病毒方法的建立

为了建立一种快速准确的检测埃博拉病毒(EBOV)亚型的方法。本研究根据GenBank中公布的EBOV NP基因序列,通过设计引物和优化反应条件,建立了一种SYBR GreenⅠ荧光定量RT-PCR检测方法检测EBOV。以体外转录的EBOV RNA为模板进行试验,该方法检测的灵敏度可以达到1.0×102个拷贝/μL,检测范围达到9个数量级为102～1010,可检测5种亚型EBOV。建立的方法对马尔堡病毒(MARV)、登革病毒(DENV)、新疆出血热病毒(XHFV)、乙型脑炎病毒(JEV)、流感病毒(H1N1和H3N2)和猪繁殖和呼吸综合征病毒(PRRSV)E基因组RNA无非特异性扩增。本文将荧光定量RT-PCR技术用于埃博拉病毒的定量检测中,并且建立了EBOV SYBRGreenⅠ荧光定量RT-PCR检测方法。     

埃博拉病毒来源miRNA的研究综述

近年来,随着对microRNA（miRNA）的广泛研究,人们发现,不仅有细胞结构的生物具有产生miRNA的能力,无细胞结构的病毒同样具有产生miRNA从而影响自身复制及调控宿主基因表达和信号通路的能力。埃博拉病毒（Ebola virus,EBOV）已经多次导致一定规模的流行,病毒的高致死率和复杂的致病机制引起了人们的高度重视,多项研究指出EBOV具有产生miRNA的能力,且在其感染过程中发挥一定的作用。本文对埃博拉病毒来源miRNA的预测、证实及检测相关研究进行综述,以期为全面了解EBOV来源的miRNA提供参考。     

以副流感病毒为载体的三价埃博拉病毒疫苗诱导的抗体介导的保护机制

<正>埃博拉病毒扎伊尔(Ebolaviruses Zaire,EBOV)、本迪布焦(Bundibugyo,BDBV)和苏丹(Sudan,EBOV)毒株造成人类疾病,病死率高。使用单一包膜糖蛋白(Glycoprotein ,GP)的实验性单价疫苗都不能提供抵御异源埃博拉病毒的保护。以副流感病毒为载体的三价埃博拉病毒疫苗具有无针给药和诱导呼吸道黏膜应答等优点。采取多种途径来诱导针对三种埃博拉病毒的广泛保护。虽然以糖蛋白(GP)共有序列为基础的抗原     

埃博拉假病毒小鼠攻毒模型的建立与评估

埃博拉病毒具有极大的危险性,对其活病毒相关的操作必须严格限制在生物安全四级实验室（BSL-4）中,阻碍了疫苗和治疗药物的研发进程。本研究将扎伊尔埃博拉病毒（EBOV）膜表面糖蛋白（GP）表达质粒与携带荧光素酶报告基因的pNL4-3.Luc.R-E-慢病毒载体共转染至HEK293T细胞,包装HIV骨架的EBOV GP-Fluc假病毒颗粒,建立了BSL-2条件下基于假病毒和生物发光成像（BLI）技术的BALB/c小鼠EBOV感染模型,并通过不同给药时间、途径和抗体种类的系统评估对其可靠性进行了验证。腹腔注射包含GP全长的假病毒在第4d可检测到集中于胸腺部位的最大发光信号,测试抗体在预防性静脉给药时可完全阻断假病毒的感染,在暴露后腹腔给药时表现出与其在活病毒小鼠模型中一致的保护效力。该模型为埃博拉病毒以及类似烈性病原体防治药物研发提供了一种简单有效的前期筛选方案。     

埃博拉病毒NP蛋白的单克隆抗体制备及抗原肽的定位

埃博拉病毒(Ebola virus,EBOV)是一种能导致人类及脊椎动物出血热的致死性病毒,对公共卫生具有较严重的危害。EBOV的NP蛋白在病毒复制中具有重要作用,也是诊断该病重要的靶蛋白。文中原核表达重组扎伊尔型EBOV的NP蛋白,重组蛋白免疫bal/c小鼠,制备了一株小鼠抗EBOV-NP的单克隆抗体。利用Western blotting方法,该抗体能特异识别真核表达和原核表达的重组EBOV-NP,并能同莱斯顿型(RestonEbola virus,REBOV)、科特迪瓦型(Cote-d’Ivoire Ebola virus,CIEBOV)和本迪布焦型(Bundibugyo Ebola virus,BEBOV)埃博拉病毒产生交叉反应,而不与苏丹型(the Sudan Ebola virus,SEBOV)和马堡型(the Marburgvirus,MARV)埃博拉病毒产生反应。利用突变PCR和Western blotting方法,定位了该抗体识别的抗原决定簇序列,该序列(PPLESD)位于EBOV-NP蛋白的C端583-588aa。生物信息学研究表明,该序列在已经公布的ZEBOV、CIEBOV、BEBOV共16个型和REBOV的4个型中高度保守。研究结果为建立以上各型埃博拉病毒的检测方法提供了工具,也为研究埃博拉病毒复制及致病机理提供了基础。     

EBOV-Z和MARV的NP基因在杆状病毒表达系统的表达及反应原性鉴定

利用昆虫杆状病毒表达系统,成功地对埃博拉(EBOV)扎伊尔型病毒和马尔堡病毒(MARV)的NP基因进行表达。Western blot结果显示,重组EBOV蛋白和重组MARV-NP与各自阳性血清有特异的反应原性,在血清学上无交叉反应。IFA检测感染重组昆虫杆状病毒的Sf9细胞表明,EBOV和MARV NP获得大量表达,呈现强烈的荧光,对照组细胞无特异荧光。该研究为EBOV和MARV流行病学调查和研制诊断试剂盒奠定了基础。     

埃博拉病毒(EBOV)蛋白的最新研究进展

埃博拉病毒(EBOV)是一种高致死性的病毒,在其RNA编码的7种蛋白中,糖蛋白GP、基质蛋白VP40以及膜蛋白VP24在病毒粒子的装配、出芽以及致病过程中起着关键的作用。详细介绍了这三种蛋白的结构、功能以及作用机制的最新研究进展,并对EBOV蛋白的研究前景作出了展望。     

关于在科学研究中防控埃博拉病毒的建议

自今年2月以来,从几内亚开始的新一轮埃博拉疫情正呈加速蔓延之势,截至9月7日,几内亚、利比里亚、塞拉利昂等国共报告埃博拉出血热病例4366例,死亡2218人。8月8日,WHO正式宣布,西非埃博拉疫情是＂国际关注的公共卫生突发紧急事件＂,是近40年来这类疫情最复杂的一次暴发。埃博拉病毒病（Ebola virus disease,EVD）是由埃博拉病毒（Ebola virus,EBOV）引起的一种急性出血性传染病。世界卫生组织已将EBOV列为对人类危害最严重的第4级病毒,按照中华人民共和国卫生部制定的《人间传染的病原微生物名录》中的要求,EBOV危害程度属于一类,     

丝状病毒糖蛋白突变及治疗性抗体的研究进展

埃博拉病毒(Ebola virus,EBOV)和马尔堡病毒(Marburg virus,MARV)同属丝状病毒科,均是传染率和致死率极高的四级烈性病毒,可感染人类及非人灵长类动物等。病毒表面的糖蛋白(glycoprotein,GP)与受体结合、病毒入胞密切相关,是导致病毒致病性最重要的蛋白,在抗体和疫苗的研发中被认为是重要靶点。在EBOV暴发期间已有4种针对GP的抗体(ZMAPP、Regn-EB3、m Ab114和MIL77)成功救治了多名感染EBOV的患者,但目前还没有MARV抗体进行过临床试验。现就丝状病毒EBOV和MARV的GP突变及治疗性抗体作一概述。     

Zoonotic risk factors associated with seroprevalence of Ebola virus GP antibodies in the absence of diagnosed Ebola virus disease in the Democratic Republic of Congo

BackgroundEbola virus (EBOV) is a zoonotic filovirus spread through exposure to infected bodily fluids of a human or animal. Though EBOV is capable of causing severe disease, referred to as Ebola Virus Disease (EVD), individuals who have never been diagnosed with confirmed, probable or suspected EVD can have detectable EBOV antigen-specific antibodies in their blood. This study aims to identify risk factors associated with detectable antibody levels in the absence of an EVD diagnosis.MethodologyData was collected from September 2015 to August 2017 from 1,366 consenting individuals across four study sites in the DRC (Boende, Kabondo-Dianda, Kikwit, and Yambuku). Seroreactivity was determined to EBOV GP IgG using Zaire Ebola Virus Glycoprotein (EBOV GP antigen) ELISA kits (Alpha Diagnostic International, Inc.) in Kinshasa, DRC; any result above 4.7 units/mL was considered seroreactive. Among the respondents, 113 (8.3%) were considered seroreactive. Several zoonotic exposures were associated with EBOV seroreactivity after controlling for age, sex, healthcare worker status, location, and history of contact with an EVD case, namely: ever having contact with bats, ever having contact with rodents, and ever eating non-human primate meat. Contact with monkeys or non-human primates was not associated with seroreactivity.ConclusionsThis analysis suggests that some zoonotic exposures that have been linked to EVD outbreaks can also be associated with EBOV GP seroreactivity in the absence of diagnosed EVD. Future investigations should seek to clarify the relationships between zoonotic exposures, seroreactivity, asymptomatic infection, and EVD.     

Evidence for distinct mechanisms of small molecule inhibitors of filovirus entry

Many small molecules have been identified as entry inhibitors of filoviruses. However, a lack of understanding of the mechanism of action for these molecules limits further their development as anti-filoviral agents. Here we provide evidence that toremifene and other small molecule entry inhibitors have at least three distinctive mechanisms of action and lay the groundwork for future development of anti-filoviral agents. The three mechanisms identified here include: (1) direct binding to the internal fusion loop region of Ebola virus glycoprotein (GP); (2) the HR2 domain is likely the main binding site for Marburg virus GP inhibitors and a secondary binding site for some EBOV GP inhibitors; (3) lysosome trapping of GP inhibitors increases drug exposure in the lysosome and further improves the viral inhibition. Importantly, small molecules targeting different domains on GP are synergistic in inhibiting EBOV entry suggesting these two mechanisms of action are distinct. Our findings provide important mechanistic insights into filovirus entry and rational drug design for future antiviral development.     

Differences in the Comparative Stability of Ebola Virus Makona-C05 and Yambuku-Mayinga in Blood

In support of the response to the 2013–2016 Ebola virus disease (EVD) outbreak in Western Africa, we investigated the persistence of Ebola virus/H.sapiens-tc/GIN/2014/Makona-C05 (EBOV/Mak-C05) on non-porous surfaces that are representative of hospitals, airplanes, and personal protective equipment. We performed persistence studies in three clinically-relevant human fluid matrices (blood, simulated vomit, and feces), and at environments representative of in-flight airline passenger cabins, environmentally-controlled hospital rooms, and open-air Ebola treatment centers in Western Africa. We also compared the surface stability of EBOV/Mak-C05 to that of the prototype Ebola virus/H.sapiens-tc/COD/1976/Yambuku-Mayinga (EBOV/Yam-May), in a subset of these conditions. We show that on inert, non-porous surfaces, EBOV decay rates are matrix- and environment-dependent. Among the clinically-relevant matrices tested, EBOV persisted longest in dried human blood, had limited viability in dried simulated vomit, and did not persist in feces. EBOV/Mak-C05 and EBOV/Yam-May decay rates in dried matrices were not significantly different. However, during the drying process in human blood, EBOV/Yam-May showed significantly greater loss in viability than EBOV/Mak-C05 under environmental conditions relevant to the outbreak region, and to a lesser extent in conditions relevant to an environmentally-controlled hospital room. This factor may contribute to increased communicability of EBOV/Mak-C05 when surfaces contaminated with dried human blood are the vector and may partially explain the magnitude of the most recent outbreak, compared to prior outbreaks. These EBOV persistence data will improve public health efforts by informing risk assessments, structure remediation decisions, and response procedures for future EVD outbreaks.     

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.     

A New Approach for Monitoring Ebolavirus in Wild Great Apes

Background

Central Africa is a “hotspot” for emerging infectious diseases (EIDs) of global and local importance, and a current outbreak of ebolavirus is affecting multiple countries simultaneously. Ebolavirus is suspected to have caused recent declines in resident great apes. While ebolavirus vaccines have been proposed as an intervention to protect apes, their effectiveness would be improved if we could diagnostically confirm Ebola virus disease (EVD) as the cause of die-offs, establish ebolavirus geographical distribution, identify immunologically naïve populations, and determine whether apes survive virus exposure.

Methodology/Principal findings

Here we report the first successful noninvasive detection of antibodies against Ebola virus (EBOV) from wild ape feces. Using this method, we have been able to identify gorillas with antibodies to EBOV with an overall prevalence rate reaching 10% on average, demonstrating that EBOV exposure or infection is not uniformly lethal in this species. Furthermore, evidence of antibodies was identified in gorillas thought previously to be unexposed to EBOV (protected from exposure by rivers as topological barriers of transmission).

Conclusions/Significance

Our new approach will contribute to a strategy to protect apes from future EBOV infections by early detection of increased incidence of exposure, by identifying immunologically naïve at-risk populations as potential targets for vaccination, and by providing a means to track vaccine efficacy if such intervention is deemed appropriate. Finally, since human EVD is linked to contact with infected wildlife carcasses, efforts aimed at identifying great ape outbreaks could have a profound impact on public health in local communities, where EBOV causes case-fatality rates of up to 88%.     

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.     

Assessment of Environmental Contamination and Environmental Decontamination Practices within an Ebola Holding Unit,Freetown, Sierra Leone

Evidence to inform decontamination practices at Ebola holding units (EHUs) and treatment centres is lacking. We conducted an audit of decontamination procedures inside Connaught Hospital EHU in Freetown, Sierra Leone, by assessing environmental swab specimens for evidence of contamination with Ebola virus by RT-PCR. Swabs were collected following discharge of Ebola Virus Disease (EVD) patients before and after routine decontamination. Prior to decontamination, Ebola virus RNA was detected within a limited area at all bedside sites tested, but not at any sites distant to the bedside. Following decontamination, few areas contained detectable Ebola virus RNA. In areas beneath the bed there was evidence of transfer of Ebola virus material during cleaning. Retraining of cleaning staff reduced evidence of environmental contamination after decontamination. Current decontamination procedures appear to be effective in eradicating persistence of viral RNA. This study supports the use of viral swabs to assess Ebola viral contamination within the clinical setting. We recommend that regular refresher training of cleaning staff and audit of environmental contamination become standard practice at all Ebola care facilities during EVD outbreaks.     

Induction of Cell-Cell Fusion by Ebola Virus Glycoprotein: Low pH Is Not a Trigger

Ebola virus (EBOV) is a highly pathogenic filovirus that causes hemorrhagic fever in humans and animals. Currently, how EBOV fuses its envelope membrane within an endosomal membrane to cause infection is poorly understood. We successfully measure cell-cell fusion mediated by the EBOV fusion protein, GP, assayed by the transfer of both cytoplasmic and membrane dyes. A small molecule fusion inhibitor, a neutralizing antibody, as well as mutations in EBOV GP known to reduce viral infection, all greatly reduce fusion. By monitoring redistribution of small aqueous dyes between cells and by electrical capacitance measurements, we discovered that EBOV GP-mediated fusion pores do not readily enlarge—a marked difference from the behavior of other viral fusion proteins. EBOV GP must be cleaved by late endosome-resident cathepsins B or L in order to become fusion-competent. Cleavage of cell surface-expressed GP appears to occur in endosomes, as evidenced by the fusion block imposed by cathepsin inhibitors, agents that raise endosomal pH, or an inhibitor of anterograde trafficking. Treating effector cells with a recombinant soluble cathepsin B or thermolysin, which cleaves GP into an active form, increases the extent of fusion, suggesting that a fraction of surface-expressed GP is not cleaved. Whereas the rate of fusion is increased by a brief exposure to acidic pH, fusion does occur at neutral pH. Importantly, the extent of fusion is independent of external pH in experiments in which cathepsin activity is blocked and EBOV GP is cleaved by thermolysin. These results imply that low pH promotes fusion through the well-known pH-dependent activity of cathepsins; fusion induced by cleaved EBOV GP is a process that is fundamentally independent of pH. The cell-cell fusion system has revealed some previously unappreciated features of EBOV entry, which could not be readily elucidated in the context of endosomal entry.     

Multiple Cationic Amphiphiles Induce a Niemann-Pick C Phenotype and Inhibit Ebola Virus Entry and Infection

Ebola virus (EBOV) is an enveloped RNA virus that causes hemorrhagic fever in humans and non-human primates. Infection requires internalization from the cell surface and trafficking to a late endocytic compartment, where viral fusion occurs, providing a conduit for the viral genome to enter the cytoplasm and initiate replication. In a concurrent study, we identified clomiphene as a potent inhibitor of EBOV entry. Here, we screened eleven inhibitors that target the same biosynthetic pathway as clomiphene. From this screen we identified six compounds, including U18666A, that block EBOV infection (IC₅₀ 1.6 to 8.0 µM) at a late stage of entry. Intriguingly, all six are cationic amphiphiles that share additional chemical features. U18666A induces phenotypes, including cholesterol accumulation in endosomes, associated with defects in Niemann–Pick C1 protein (NPC1), a late endosomal and lysosomal protein required for EBOV entry. We tested and found that all six EBOV entry inhibitors from our screen induced cholesterol accumulation. We further showed that higher concentrations of cationic amphiphiles are required to inhibit EBOV entry into cells that overexpress NPC1 than parental cells, supporting the contention that they inhibit EBOV entry in an NPC1-dependent manner. A previously reported inhibitor, compound 3.47, inhibits EBOV entry by blocking binding of the EBOV glycoprotein to NPC1. None of the cationic amphiphiles tested had this effect. Hence, multiple cationic amphiphiles (including several FDA approved agents) inhibit EBOV entry in an NPC1-dependent fashion, but by a mechanism distinct from that of compound 3.47. Our findings suggest that there are minimally two ways of perturbing NPC1-dependent pathways that can block EBOV entry, increasing the attractiveness of NPC1 as an anti-filoviral therapeutic target.