研发动态

<正>中科院微生物所发现新型人冠状病毒感染机制中科院微生物所高福课题组对2012年在中东发现的高致病性新型冠状病毒MERS-CoV进行了研究,发现人CD26分子(又称二肽基肽酶4)是MERS-CoV在细胞表面的受体,从而揭示了该病毒对人的感染机制,相关研究成果发表在最新出版的Nature上。     

新型冠状病毒致病机理及其疫苗的研发进展

新型冠状病毒(severe acute respiratory syndrome coronavirus-2, SARS-CoV-2)是一种可引起人新型冠状病毒肺炎(novel coronavirus pneumonia, NCP;亦称为COVID-19)的新发呼吸道病原体,与中东呼吸综合征冠状病毒(Middle East respiratory syndrome coronavirus, MERS-CoV)和严重急性呼吸综合征冠状病毒(severe acute respiratory syndrome coronavirus, SARS-CoV)同属β-冠状病毒,其受体与SARS-CoV的受体相同,均利用血管紧张素转化酶2(angiotensin-converting enzyme 2, ACE2)受体入侵人体细胞。SARS-CoV-2主要通过呼吸系统和消化系统感染,具有较高的传染性和致死率。目前,新冠病毒引起的肺炎已在全球范围内大规模蔓延,接种疫苗是根除病毒性传染病最有效的方法,国内外各大科研机构已快速展开COVID-19疫苗的研制工作,这是有效控制疫情的重点和难点。现就新冠病毒的致病机理、感染途径及疫苗研发作一综述,旨在为相关研究人员提供参考。     

中东呼吸综合征冠状病毒RT-RAA快速检测方法的建立及应用

建立基于重组酶介导的中东呼吸综合征冠状病毒(MERS-CoV)核酸检测方法。本研究设计、合成特异性中东呼吸综合征冠状病毒基因的重组酶介导检测(RAA)引物及探针,制备MERS-CoV假病毒颗粒阳性对照品,通过一系列条件优化建立了MERS-CoV的快速、灵敏、特异的RT-RAA检测方法,分别与荧光定量RT-PCR检测方法做比较,并且采用首例中国MERS-CoV韩国地区输入病例的咽拭子样品、其它类似呼吸道病毒样本以及英国QCMD的MERS-CoV室间质评灭活样本做临床验证。结果显示:建立的RT-RAA方法检测中东呼吸综合征冠状病毒灵敏度为10拷贝,高于本实验室建立的荧光RT-PCR方法灵敏度(100拷贝),且检测时间(4.8～13.6min)大大低于荧光RT-PCR检测时间(90min);用该方法检测中东呼吸综合征冠状假病毒颗粒为阳性,而检测其他8种对照呼吸道病毒均呈阴性;检测临床阳性样本也与实际结果相符。本研究建立的中东呼吸综合征冠状病毒RT-RAA检测方法灵敏、特异、快速,可用于中东呼吸综合征冠状病毒感染的现场快速诊断和流行病学调查。     

猪肠道冠状病毒与入侵受体氨基肽酶N的相互作用

猪肠道冠状病毒是目前危害养猪产业的重要病原。目前已发现能够感染猪肠道的致病性冠状病毒有4种：猪传染性胃肠炎病毒、猪流行性腹泻病毒、猪丁型冠状病毒和猪肠道甲型冠状病毒。冠状病毒感染宿主的第一步是识别宿主细胞膜受体分子并与之结合,随后启动入侵及膜融合进而使病毒基因组进入宿主细胞内部。因此,冠状病毒受体是决定其宿主范围及组织嗜性的关键因素。确定冠状病毒受体及病毒与受体的结合机制对预防新发病毒及开发冠状病毒治疗性药物具有重要意义。猪传染性胃肠炎病毒利用猪氨基肽酶N（aminopeptidase N,APN）作为感染宿主的功能性受体,并利用唾液酸作为辅助结合因子。猪APN最初也被鉴定为猪流行性腹泻病毒的功能性受体,但近年的研究结果与前面的报道存在较大的差异,产生了较大的争议。最近的研究认为,猪丁型冠状病毒的功能性受体也是APN,并且猪丁型冠状病毒能够利用多个物种的APN作为功能性受体,这与其跨物种传播具有密切关系。最新发现的猪肠道甲型冠状病毒则不使用APN作为其入侵受体。本文综述了前面3种猪肠道病毒感染宿主细胞的受体及结合机制的研究进展,并比较分析了猪APN及唾液酸在不同猪肠道冠状病毒入侵宿主过程中结合方式的异同,为进一步研究新发猪肠道冠状病毒受体提供参考。     

关于新型冠状病毒动物宿主和动物感染的研究进展

新型冠状病毒（Severe acute respiratory syndrome coronavirus 2, SARS-CoV-2）是一种全新的病毒,是继严重急性呼吸综合征冠状病毒（Severe acute respiratory syndrome coronavirus, SARS-CoV）和中东呼吸综合征冠状病毒（Middle East Respiratory Syndrome Syndrome Coronavirus, MERS-CoV）之后引起人类大范围感染的第三种冠状病毒。目前不少研究提示SARS-CoV-2可能来源于动物,动物在疫情的发生与传播过程中起着重要作用。这篇综述总结了目前关于SARS-CoV-2动物宿主和动物易感性的最新研究进展。现有研究提示,SARS-CoV-2很可能起源于蝙蝠,穿山甲是中间宿主。恒河猴,水貂、白尾鹿,动物园里的老虎、狮子,以及宠物猫、狗等动物可能在暴露后发生SARS-CoV-2感染,此外实验室动物感染实验也证明了一些动物对SARS-CoV-2易感,提示下一步需要加强对动物宿主中的SARS-CoV-2监测,为病毒溯源、变异进化规律与传播机制分析...     

不同剂量DPP4转导后MERS-CoV感染小鼠模型的临床及生物学特征比较

本研究探讨不同剂量DPP4转导小鼠后对中东呼吸综合征冠状病毒(Middle East respiratory syndrome coronavirus,MERS-CoV)感染建模及其生物特性的影响。首先将表达MERS-CoV受体DPP4的重组腺病毒以高剂量(2.5×108 PFU/只)、低剂量(0.5×108 PFU/只)分别转导转导BALB/c小鼠,继而滴鼻接种MERS-CoV,建立MERS-CoV感染小鼠模型。对成功构建的小鼠感染模型分别进行体征、病毒复制、免疫病理及抗体应答的比较分析。结果表明:两种剂量DPP4转导后MERS-CoV感染小鼠,均可引起典型肺炎表征,在小鼠肺部能检测到病毒复制及免疫病理,但高剂量DPP4转导组小鼠肺炎体征与肺病理损伤更明显,病毒复制水平亦高于低剂量DPP4转导组。小鼠感染建模后2w后可检测到结构蛋白特异抗体与中和抗体,高剂量DPP4转导组抗体应答亦明显高于低剂量转导组。本研究以两种剂量DPP4转导小鼠,均成功建立了MERS-CoV感染的小鼠模型,受体DPP4转导水平可影响MERS-CoV感染小鼠体征、病毒复制及抗体应答。     

新型冠状病毒疫苗研究策略分析

新型冠状病毒(SARS-CoV-2)是一种可引起人新型冠状病毒肺炎(COVID-19)的新发呼吸道病原体,与重症急性呼吸道综合症冠状病毒(SARS-CoV)和中东呼吸综合征冠状病毒(MERS-CoV)同属于β-冠状病毒,具有较高的传染性和一定的致死率。2019年12月在我国武汉被发现,随后蔓延到我国大部分省份,给我国人民健康和经济发展造成巨大损失。疫苗接种是预防和控制传染病的常规和有效手段,国内外多个机构已启动COVID-19疫苗研究工作。文中基于SARS和MERS疫苗研究的经验和教训,对COVID-19疫苗的研究策略和需要注意的关键问题进行了阐述,为相关研究人员提供参考。     

高致病性冠状病毒感染时的固有免疫应答:精准治疗的潜在靶点

21世纪初,包括严重急性呼吸综合征冠状病毒（SARS-CoV）和中东呼吸综合征冠状病毒（MERS-CoV）在内的高致病性冠状病毒对人类健康构成了巨大威胁。随着新型冠状病毒肺炎（COVID-19）在全球的暴发,冠状病毒尤其是能够引起严重下呼吸道感染的高致病性冠状病毒（HPCoVs）再次引起了人们的关注。在HPCoVs不断出现的大背景下,阐明其致病机制并控制感染过程中的宿主免疫对抵抗病毒感染,避免过度反应至关重要。在病毒感染过程中,多种天然免疫信号在冠状病毒感染过程发挥关键作用。本文就近年来出现的HPCoVs特征及其感染过程中天然免疫的应答情况作一综述,借此探寻重症感染患者炎症反应旺盛的原因并解释其临床表现,为进一步探寻精准治疗的潜在靶点。     

hDPP4转基因及定点敲入小鼠模型的建立及其对MERS-CoV易感性比较

中东呼吸系统综合征冠状病毒(Middle East respiratory syndrome coronavirus,MERS-CoV)是2012年发现的新型高致病性冠状病毒,其病死率高达34.4%。人二肽基肽酶-4(human dipeptidyl peptidase-4,hDPP4)分子是MERS-CoV进入宿主细胞的受体。为了获得稳定的MERS-CoV易感小鼠模型,本文分别利用Tol2转基因技术和CRISPR/Cas9技术将hDPP4受体导入C57BL/6小鼠,筛选获得转基因小鼠hDPP4-Tg、定点敲入小鼠hDPP4-KI;通过Q-PCR、Western Blot及活体成像技术,分析了hDPP4基因的表达特征。结果显示,在hDPP4-Tg小鼠中,其表达水平较低,在脑中高表达;而在hDPP4-KI中整体表达水平高,表达优势脏器为肺。假病毒感染实验表明,hDPP4-Tg几乎不易感,而hDPP4-KI小鼠对假病毒高度易感。进而,对假病毒感染hDPP4-KI小鼠的感染途径、感染剂量、是否剃除被毛等条件进行优化,获得了稳定易感的MERS-CoV假病毒感染模型,并利用该模型初步评价了单克隆抗体hMS-1的体内活性。本研究显示,即使相同的受体基因,不同策略构建的遗传修饰小鼠模型的效果差异较大;受体分子表达水平与模型的易感性高度相关;本研究获得的高效而稳定的MERS-CoV假病毒感染模型可望在抗体评价、疫苗研制、药物筛选等领域提供模型工具,提示将受体分子定点插入小鼠基因组、高表达受体基因是成功构建病毒易感模型首选策略。     

人类冠状病毒调节宿主抗病毒天然免疫分子机制

SARS冠状病毒和正在全球流行的猪源H1N1型流感病毒等人类新发呼吸道病毒对人类生命健康构成严重威胁.人类重要呼吸道病毒与宿主抗病毒天然免疫的关系是近年来研究热点.SARS冠状病毒等很多RNA病毒能够编码某种蛋白质,抑制干扰素表达以及干扰素介导的抗病毒信号通路.人类冠状病毒木瓜样蛋白酶(papain-like protease,PLP)利用其自身去泛素化酶(DUB)活性,使干扰素表达通路中重要调节蛋白发生去泛素化,从而抑制干扰素信号传导.同时,PLP蛋白酶通过阻碍干扰素表达信号通路中最新发现的重要调节蛋白ERIS(也称MITA/STING)二聚化,使其失活并丧失激活干扰素通路的功能,这些发现对于阐明人类重要呼吸道病毒对宿主细胞抗病毒天然免疫反应的调节作用及其机制具有重要意义,为人类新发病毒致病机理、免疫防治以及抗病毒药物研究提供新的思路.     

Modulation of the immune response by Middle East respiratory syndrome coronavirus

Coronavirus (CoV) infections are commonly associated with respiratory and enteric disease in humans and animals. In 2012, a new human disease called Middle East respiratory syndrome (MERS) emerged in the Middle East. MERS was caused by a virus that was originally called human coronavirus-Erasmus Medical Center/2012 but was later renamed as Middle East respiratory syndrome coronavirus (MERS-CoV). MERS-CoV causes high fever, cough, acute respiratory tract infection, and multiorgan dysfunction that may eventually lead to the death of the infected individuals. The exact origin of MERS-CoV remains unknown, but the transmission pattern and evidence from virological studies suggest that dromedary camels are the major reservoir host, from which human infections may sporadically occur through the zoonotic transmission. Human to human transmission also occurs in healthcare facilities and communities. Recent studies on Middle Eastern respiratory continue to highlight the need for further understanding the virus-host interactions that govern disease severity and infection outcome. In this review, we have highlighted the major mechanisms of immune evasion strategies of MERS-CoV. We have demonstrated that M, 4a, 4b proteins and Plppro of MERS-CoV inhibit the type I interferon (IFN) and nuclear factor-κB signaling pathways and therefore facilitate innate immune evasion. In addition, nonstructural protein 4a (NSP4a), NSP4b, and NSP15 inhibit double-stranded RNA sensors. Therefore, the mentioned proteins limit early induction of IFN and cause rapid apoptosis of macrophages. MERS-CoV strongly inhibits the activation of T cells with downregulation of antigen presentation. In addition, uncontrolled secretion of interferon ɣ-induced protein 10 and monocyte chemoattractant protein-1 can suppress proliferation of human myeloid progenitor cells.     

CD26/DPP4 Cell-Surface Expression in Bat Cells Correlates with Bat Cell Susceptibility to Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Infection and Evolution of Persistent Infection

Middle East respiratory syndrome coronavirus (MERS-CoV) is a recently isolated betacoronavirus identified as the etiologic agent of a frequently fatal disease in Western Asia, Middle East respiratory syndrome. Attempts to identify the natural reservoirs of MERS-CoV have focused in part on dromedaries. Bats are also suspected to be reservoirs based on frequent detection of other betacoronaviruses in these mammals. For this study, ten distinct cell lines derived from bats of divergent species were exposed to MERS-CoV. Plaque assays, immunofluorescence assays, and transmission electron microscopy confirmed that six bat cell lines can be productively infected. We found that the susceptibility or resistance of these bat cell lines directly correlates with the presence or absence of cell surface-expressed CD26/DPP4, the functional human receptor for MERS-CoV. Human anti-CD26/DPP4 antibodies inhibited infection of susceptible bat cells in a dose-dependent manner. Overexpression of human CD26/DPP4 receptor conferred MERS-CoV susceptibility to resistant bat cell lines. Finally, sequential passage of MERS-CoV in permissive bat cells established persistent infection with concomitant downregulation of CD26/DPP4 surface expression. Together, these results imply that bats indeed could be among the MERS-CoV host spectrum, and that cellular restriction of MERS-CoV is determined by CD26/DPP4 expression rather than by downstream restriction factors.     

Protective Efficacy of Recombinant Modified Vaccinia Virus Ankara Delivering Middle East Respiratory Syndrome Coronavirus Spike Glycoprotein

Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe respiratory disease in humans. We tested a recombinant modified vaccinia virus Ankara (MVA) vaccine expressing full-length MERS-CoV spike (S) glycoprotein by immunizing BALB/c mice with either intramuscular or subcutaneous regimens. In all cases, MVA-MERS-S induced MERS-CoV-specific CD8⁺ T cells and virus-neutralizing antibodies. Vaccinated mice were protected against MERS-CoV challenge infection after transduction with the human dipeptidyl peptidase 4 receptor. This MERS-CoV infection model demonstrates the safety and efficacy of the candidate vaccine.     

Two Mutations Were Critical for Bat-to-Human Transmission of Middle East Respiratory Syndrome Coronavirus

To understand how Middle East respiratory syndrome coronavirus (MERS-CoV) transmitted from bats to humans, we compared the virus surface spikes of MERS-CoV and a related bat coronavirus, HKU4. Although HKU4 spike cannot mediate viral entry into human cells, two mutations enabled it to do so by allowing it to be activated by human proteases. These mutations are present in MERS-CoV spike, explaining why MERS-CoV infects human cells. These mutations therefore played critical roles in the bat-to-human transmission of MERS-CoV, either directly or through intermediate hosts.     

Adenosine Deaminase Acts as a Natural Antagonist for Dipeptidyl Peptidase 4-Mediated Entry of the Middle East Respiratory Syndrome Coronavirus

Middle East respiratory syndrome coronavirus (MERS-CoV) replicates in cells of different species using dipeptidyl peptidase 4 (DPP4) as a functional receptor. Here we show the resistance of ferrets to MERS-CoV infection and inability of ferret DDP4 to bind MERS-CoV. Site-directed mutagenesis of amino acids variable in ferret DPP4 thus revealed the functional human DPP4 virus binding site. Adenosine deaminase (ADA), a DPP4 binding protein, competed for virus binding, acting as a natural antagonist for MERS-CoV infection.     

Middle East Respiratory Syndrome Coronavirus Accessory Protein 4a Is a Type I Interferon Antagonist

Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe acute respiratory infection with as yet unclear epidemiology. We previously showed that MERS-CoV counteracts parts of the innate immune response in human bronchiolar cells. Here we analyzed accessory proteins 3, 4a, 4b, and 5 for their abilities to inhibit the type I interferon response. Accessory protein 4a was found to block interferon induction at the level of melanoma differentiation-associated protein 5 (MDA5) activation presumably by direct interaction with double-stranded RNA.     

Mouse Dipeptidyl Peptidase 4 Is Not a Functional Receptor for Middle East Respiratory Syndrome Coronavirus Infection

Human dipeptidyl peptidase 4 (hDPP4) was recently identified as the receptor for Middle East respiratory syndrome coronavirus (MERS-CoV) infection, suggesting that other mammalian DPP4 orthologs may also support infection. We demonstrate that mouse DPP4 cannot support MERS-CoV infection. However, employing mouse DPP4 as a scaffold, we identified two critical amino acids (A288L and T330R) that regulate species specificity in the mouse. This knowledge can support the rational design of a mouse-adapted MERS-CoV for rapid assessment of therapeutics.     

Identification of a Receptor-Binding Domain in the S Protein of the Novel Human Coronavirus Middle East Respiratory Syndrome Coronavirus as an Essential Target for Vaccine Development

A novel human Middle East respiratory syndrome coronavirus (MERS-CoV) caused outbreaks of severe acute respiratory syndrome (SARS)-like illness with a high mortality rate, raising concerns of its pandemic potential. Dipeptidyl peptidase-4 (DPP4) was recently identified as its receptor. Here we showed that residues 377 to 662 in the S protein of MERS-CoV specifically bound to DPP4-expressing cells and soluble DPP4 protein and induced significant neutralizing antibody responses, suggesting that this region contains the receptor-binding domain (RBD), which has a potential to be developed as a MERS-CoV vaccine.     

A novel human coronavirus: Middle East respiratory syndrome human coronavirus

In 2012,a novel coronavirus,initially named as human coronavirus EMC(HCoV-EMC) but recently renamed as Middle East respiratory syndrome human coronavirus(MERS-CoV),was identified in patients who suffered severe acute respiratory infection and subsequent renal failure that resulted in death.Ongoing epidemiological investigations together with retrospective studies have found 61 laboratory-confirmed cases of infection with this novel coronavirus,including 34 deaths to date.This novel coronavirus is culturable and two complete genome sequences are now available.Furthermore,molecular detection and indirect immunofluorescence assay have been developed.The present paper summarises the limited recent advances of this novel human coronavirus,including its discovery,genomic characterisation and detection.     

The Receptor Binding Domain of the New Middle East Respiratory Syndrome Coronavirus Maps to a 231-Residue Region in the Spike Protein That Efficiently Elicits Neutralizing Antibodies

The spike (S) protein of the recently emerged human Middle East respiratory syndrome coronavirus (MERS-CoV) mediates infection by binding to the cellular receptor dipeptidyl peptidase 4 (DPP4). Here we mapped the receptor binding domain in the S protein to a 231-amino-acid fragment (residues 358 to 588) by evaluating the interaction of spike truncation variants with receptor-expressing cells and soluble DPP4. Antibodies to this domain—much less so those to the preceding N-terminal region—efficiently neutralize MERS-CoV infection.