冠状病毒课件.ppt
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1、Coronavirus刘根梅 IntroductionnCoronaviruses infect many species of animals, including humansnSchalk ,1931 avian infectious bronchitis(IB) Beaudette ,1936 Infectious bronchitis virus(IBV)nThe name “coronavirus,” coined in 1968, is derived from the“corona”-like or crown-like morphology observed for thes
2、e viruses in the electron microscopenIn 1975, the Coronaviridae family was establishedn2002年SARSn2002年11月16日于广东顺德首发, 并扩散至东南亚乃至全球,直至2003年中期疫情才被逐渐消灭的一次全球性传染病疫潮,其死亡率接近11%。 Classification Coroavirus GenomenNon-segmented, single-stranded, (+)sense RNA, 27-31 kb (dependent on virus) - the longest of any R
3、NA virus. The genome has a 5 methylated cap and 3 poly-A and functions directly as mRNAnthe nonstructural proteins are encoded within the 5,-proximal two-thirds of the genome on gene 1nThe structural proteins are encoded within the 3,-proximal one-third of the genome5-ORF1-(HE)-S-E-M-N-3 Coronavirus
4、 receptornVirus receptor: viruses must first bind to their target cells surface before infection can proceed; this is mediated by specific molecular receptors for certain viral antigensnIBV receptor:a 2,3-linked sialic acid Coronavirus transcription and replicationntranscriptionnthe 5 20kb of the (+
5、)sense genome translated to produce a viral polymerase, which then produces a (-)sense strand .This is used as a template to produce mRNA as a nested set of transcripts, all with an identical 5 non-translated leader sequence of 72nt & coincident 3 polyadenylated endsn不连续转录机制 模型一: 病毒转录时,以负链RNA为模板,首先合
6、成 leader sequence,在某些原因的作用下 leader sequence 可脱落,依靠 TRS 的保守性,可结合到其下游的任意基因前端的 TRS,继续转录,从而产生了一系列的亚基因组。n模型二: 以mRNA为模板合成一系列的负链亚基因组RNA, 以anti-leader sequences 为引物,负链亚基因组RNA 为模板,合成一系列的亚基因组。n移码机制:ORF1a和 ORF1b 之间存在特殊的发夹结构,称为假节体。其上游 28nt处为滑动序列,为保守的“UUUAAAC”。ORF1a 的终止密码子在其下游 27nt 处。在移码信号的作用下,核糖体读取滑动序列的下游序列时向-1
7、 位移码,从而将 ORF1a 和 ORF1b 读通,产生了融合蛋白 1abreplicationnCoronavirus replication is slow compared to other enveloped virusesnMinimum Sequence Requirements for Genome Replication: gene 1 products5,and 3, UTRs,N genenat least two stem-loops (stem-loops III and IV) function as higher-order cis-acting signaling
8、 elements Stems C, D,and F have been shown to be required for replication of both the DI RNA and virus genomenA 74-nt bulged stem-loop mapping from nt 68 to 142 from the 3, terminus contains two stems that demonstrated importance as cis-acting replication structuresna specified gene order per se is
9、not essential for coronavirus replication in cell culture, but that order contributes in some way to a more robust virus yieldnGene Order for Genome ReplicationProteins Replicase Proteins the nonstructural proteins involved in proteolytic processing, genome replication, and subgenomic mRNA synthesis
10、 npapain-like proteases :PLP1 and PLP2; n3C-like protease : 3CLpro nputative RNA-dependent RNA polymerase:RdRpnHelicase:Helstructure ProteinsnThe genome is associated with a basic phos-phoprotein, N. nThe envelope carries three glycoproteins:nS - Spike protein: receptor binding, cell fusion, major a
11、ntigen nE - Envelope protein: small, envelope- associated protein nM - Membrane protein: transmembrane - budding & envelope formation nIn a few types, there is a third glycoprotein:nHE - Haemagglutinin-esterase NnN protein, the virus RNA binding protein, is one of the most abundant viral proteins.it
12、 can localize to both the cytoplasm and nucleus/nucleolus.nit plays a role in transcription and also in pathogenesis. it is necessary for efficient recovery of virus from infectious cDNA clones and can enhance the virus replication.nSeveral coronavirus N proteins have been shown to be phosphorylated
13、, it was predicted to play a role in determining the affinity of binding of viral RNA. MnM is the most abundant protein in the viral envelope and is important for virus maturation, interacting with E, S, and the nucleocapsid during assembly. nThe matrix (M) protein is a glycoprotein with three trans
14、membrane domains; its large C terminus is thought to bind to the nucleocapsid during budding. it have functions in host interactions SnThe coronavirus spike protein is less abundant than M in virions and plays vital roles in viral entry,cell-to-cell spread, and determining tissue tropism and pathoge
15、nesisn It is a dimer or trimer , usually in a cleaved form,as two subunits,amino-terminal S1 and carboxy-terminal S2。 S1 form the bulbous head, S2 is anchored in the membranenThe cleavage site is usually associated with one or more pairs of basic amino acidsn eg:Arg-Arg-Ser-Arg-ArgS spike determinin
16、g tissue tropism EnE protein is an integral membrane ,and an important role in viral assembly with the M protein.nIt expressed alone or when expressed together with M, forms virus-like particlesnSARS-CoV E:cationselective ion channel activity, enhance viral morphogenesis and assemblynMHV-A59 E:play
17、a role in hostvirus interaction, specifically in induction of apoptosis HEnThe virions of some zntigenic group 2 coronavirus (MHV, BCoV) and turkey coronavirus(TcoV;group 3)have a hemagglutinin-esterase(HE) glycoprotein attached to the surface of the virion.nhemagglutinin/esterase (HE) protein which
18、 is assumed to be acquired from influenza virus C and is not essential for viral replication in vivo or in vitro.nIt may play a role in tropismnIt forms a second type of spikeProperties and functions of coronavirus structural proteinsIB(infectious bronchitis virus)n禽传染性支气管炎是由禽传染性支气管炎病毒的鸡的一种急性、高度接触性传
19、染病。该病主要侵害鸡的呼吸系统、泌尿生殖系统和消化系统,使病鸡出现呼吸困难、肾脏病变和产蛋下降等症状。目前,该病已呈世界范围流行,是严重危害世界养禽业的重大传染病之一。 IBV genome IBV 毒株n目前超过 100多个毒株n呼吸型:为经典型鸡传染性支气管炎,是由 Schalk 和 Hawn (1931)在美国北部的 Dakota州首先发现的 H120, H52 , M41, Massn肾型:Winterfield和Hitchner于1962年首次报道了肾型IB,证实了某些IBV毒株可引发肾脏病变 T,Gray ,Holte, Iowa699,11731n 肠型: EI-Houaadfi
20、 等 1985 年从摩洛哥分离出 6 株 IBV,其中 G 毒株对肠道有亲和性 。n1992 年,在英国 R.E.Gough 报道了一种主要侵害肉鸡的传染性支气管炎:4/91 or 793Bn 腺胃型:1994年以来,我国的江苏、山东先后流行了一种以腺胃肿胀、腺胃乳头溃疡为特征的传染病 The most epidemic:M41、T、H120、H52、Hotle、Grayn原因:n病毒的不连续转录方式,使的病毒基因更易发生突变,缺失,置换,从而导致新型毒株的出现n在高密度免疫的情况下,IBV 野毒和多个疫苗株会通过基因重组等产生新的变异株(Kapczynski DR. et al. 2003)
21、,这是免疫选择压力下 IBV 变异的另一重要途径。n流行病学n本病主要通过呼吸道排毒,经空气飞沫传给易感鸡,传染性极强,与感染鸡同舍的易感鸡通常在48h内出现症状。病鸡康复后仍带毒,排毒时间长达140天之久,因此也可被污染的饲料、饮水、用具等经消化道使鸡感染。本病一年四季均可发生,但以寒冷季节多发。临床症状临床症状n呼吸型: 多在 5 周龄以下发病,除衰弱、精神不振等一般症状外,4 周龄以下鸡常表现为伸颈、张口呼吸、咳嗽、打喷嚏、气管啰音等;56 周龄以上的鸡症状较轻,表现气管啰音、气喘和微咳,并以夜间较为明显。产蛋鸡呼吸道症状温和,但会出现产蛋率下降,产软壳蛋、畸形蛋等症状n肾型: 目前发生
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