SARS-CoV动物模型研究之中国现状

目的综合对比SARS-CoV感染的恒河猴、布氏田鼠及Lewis大鼠的病理学、免疫学以及病毒的复制与外排情况的变化,来探讨此三种动物在建立SARS模型上的特点。方法SARS病毒感染8只恒河猴、9只Lewis大鼠和20只布氏田鼠,在感染后不同时间安乐死动物,应用光镜对动物的各脏器进行病理观察研究;用病毒分离和RT-PCR方法检测病毒外排与复制的情况;用ELISA法检测动物产生特异性抗体情况。结果在SARS-CoV感染恒河猴、Lewis大鼠和布氏田鼠后,肺组织均出现一定的与人类SARS疾病相似的病理改变,在动物体内均可检测到活病毒或病毒核酸,并可检测到特异性IgG抗体的存在。在病死率上布氏田鼠最高;在病毒的复制与外排方面恒河猴的检出率最高,持续时间最长;在抗体产生情况上恒河猴与Lewis大鼠基本相似;在病理变化上恒河猴病变最重且最为复杂,与人类SARS疾病的病理变化最为接近。结论布氏田鼠,Lewis大鼠,特别是恒河猴动物模型可以用于SARS发病机制、疫苗和药物的研发,恒河猴动物模型是目前研究SARS疾病最理想的动物模型。     

SARS冠状病毒感染恒河猴的病毒、血清学检测研究

[目的]对感染SARS-CoV的恒河猴进行病毒、血清学等指标检测及研究,确定模型动物成功感染,并为SARS发病机制,疫苗评价,药物筛选确定参考指标。[方法]SARSCo-V经鼻腔接种8只恒河猴,在感染的第1天开始到5、7、10、15、20、30和60天分别安乐死时,不同时间取咽拭子、血液和脏器,进行病毒分离,RT-PCR检测和抗体测定。[结果]用巢式RT-PCR在感染后每天提取的咽拭子标本中检测SARS-CoV的RNA,以细胞培养冠状病毒为阳性对照,以正常恒河猴咽拭子为阴性对照,在8只动物病毒接种第5天开始可检测到大小为797bp的目的条带,阳性检出最长可持续到第15天。进一步用病毒分离实验对PCR结果进行确证,8只动物中的5只恒河猴接种5天的咽拭子标本中,经Vero细胞培养,细胞产生了典型细胞病变(CPE),提示SARS冠状病毒能感染恒河猴并有病毒的复制和排毒。IFA方法证实为SRAS-CoV抗原存在。SARS-CoV感染恒河猴后,可以检测出免疫反应。在SARS冠状病毒接种前和接种后第5、8、11、15、19、23、26、30、34、每隔4-7天以及安乐死时采血,制备血清测定抗体,8只恒河猴接种病毒前均血清中SARS冠状病毒特异性抗体IgG为阴性,10天后安乐处死的5只感染猴在11-15天开始,至安乐死时,均为阳性。IgG阳性的5只恒河猴均有一定的中和抗体产生,且对SARS病毒感染细胞有一定的保护性。感染SARS病毒猴后与正常猴比较,其细胞杀伤效应明显增强。感染SARS-CoV的恒河猴不仅出现与SARS患者类似的临床和病理学改变,也在一定时期内排毒,出现特异免疫反应,这些指标均可作为药物筛选、疫苗评价等方面的重要参数。     

SARS动物模型的研究

利用分离的SARS CoV毒株BJ 0 1,经滴鼻等途径感染大鼠、豚鼠、黑线仓鼠、白化仓鼠和雏鸡等 5个种属的动物 ,筛选对SARS易感的小动物。在此基础上 ,选择食蟹猴和恒河猴进行SARS的人工感染实验 ,评价其作为SARS动物模型的可能性。结果表明 ,大鼠、豚鼠、黑线仓鼠、白化仓鼠和雏鸡等动物对SARS均不易感 ,感染后未观察到任何的临床及病理学改变 ,不过从感染 2周后的大鼠和豚鼠的肺和咽等组织样本中检测到了的特异的核酸 ,提示SARS CoV能够在这两种动物的体内复制。从感染猴子的分泌物和脏器中分离出了病毒 ,证明SARS CoV也能够在猴子体内复制。临床和病理组织学检查结果显示 ,SARS病毒接种食蟹猴和恒河猴后 ,可以引起所有实验猴发生间质性肺炎 ,其病理学改变与人类感染SARS病毒后肺部病变近似 ,但病变的严重程度比较人类的轻得多 ,除此之外无任何其它的明显的临床表现及组织病理学改变 ,按照动物模型的指标判断食蟹猴和恒河猴并不是SARS的理想动物模型 ,不过在目前尚没有更理想的动物模型情况下 ,以间质性肺炎为病理学检查指标 ,恒河猴和食蟹猴可以作为评价抗SARS药物和疫苗的模型动物     

SARS灵长类动物模型

Greenough TC等人2005年8月在美国病理学杂志上报道了普通绒猴(Callithrixjacchus)感染SARS-CoV的试验结果。两组绒猴通过气管内感染含SARS-CoV的细胞培养物后,在第2、4、7天,动物出现了病理形态学改变和病毒复制。所有的动物都出现了多灶性单核细胞性间质性肺炎,多数动物伴有多核合体细胞、水肿、支气管炎。通过免疫组化的方法在肺泡巨噬细胞和I型上皮细胞中检测到了SARS病毒抗原。感染动物尸检中,在支气管淋巴结和心肌中都检测到了病毒RNA,并有炎性改变。多数动物还出现了肝炎,以多灶性淋巴细胞性感染为主,伴有个别肝细胞的坏死…     

老龄ICR小鼠对SARS-CoV的易感性

目的为探讨SARS的发病机制并提供易感的SARS动物模型。方法利用RT-PCR和病毒分离后免疫荧光技术检测成龄鼠和老龄鼠接种SARS-CoV后肺组织内病毒复制情况,同时观察两组动物的肺脏和肺外组织器官的病理变化,对肺组织进行免疫组化分析,观察SARS-CoV在肺内复制的主要部位。结果老龄鼠的感染率明显高于成龄鼠;老龄鼠肺脏出现更为严重的弥漫性肺泡损伤,其中两只老龄鼠的肺外器官出现了变性、灶状坏死以及血管广泛的扩张充血等全身中毒性变化;肺脏内病毒抗原主要存在于肺泡上皮细胞和间质的血管内皮细胞。结论老龄ICR小鼠对SARS-CoV的易感性明显高于成龄鼠,有可能作为研究SARS发病机制以及药物评价的动物模型。     

恒河猴感染SARS-CoV的病毒学、血清学检测

目的对感染SARS-CoV的8只恒河猴进行病毒学、血清学指标检测。方法SARS-CoV经鼻腔接种8只恒河猴,在感染的第1天开始到5、7、10、15、20、30和60天分别安乐处死时,不同时间取咽拭子、血液和脏器,进行病毒分离,RT-PCR检测和抗体测定。结果RT-PCR证实感染病毒检出时间为5~16d,8只猴中的5只分离到了病毒,感染15d后可检测到抗体。结论感染SARS-CoV的恒河猴不仅出现与SARS患者类似的临床和病理学改变,也在一定时期内排毒,出现特异免疫反应,这些指标均可作为药物筛选、疫苗评价等方面的重要参数。     

重组人干扰素α2b鼻腔喷雾剂预防治疗恒河猴感染SARS-CoV病毒的作用效果试验

[目的]评价重组人干扰素α2b鼻腔喷雾剂对预防治疗SARS-CoV病毒感染恒河猴的作用。[方法]10只恒河猴随机分为2组,每组5只。分别为试验组(重组人干扰素α2b鼻腔喷雾剂)和对照组(空白干扰素)。分别在攻毒前19h和1h,攻毒后7h、23h、31h、47h、55h、71h、95h和119h不同时间经鼻吸入受试物,0.4ml/只。按计划定时取咽拭子做real-timePCR检测和病毒分离;取静脉血做病毒分离检测、中和抗体、IgG、血常规、血生化和血凝指标。[结果]1.SARS感染对照组:全部动物咽拭子标本经real-timePCR均检出SARS-CoV病毒,持续时间从攻毒后2天至8天。攻毒后2天3只、5天1只、7天2只,其咽拭子标本中病毒分离阳性,进一步证实病毒在体内的复制。攻毒后,诱导产生高滴度的抗体和中和抗体,证实病毒感染。大体解剖全部动物肺脏为灰白色,有大面积出血,其中2只动物肺脏与胸壁有粘连,组织病理称典型SARS肺炎性病变。2.干扰素试验组:和对照组相同时间取的咽拭子等标本中,real-timePCR检测和病毒分离均未检出病毒。攻毒后病毒导致机体产生的中和抗体和IgG抗体的反应很弱。血常规、血生化和血凝指标结果表明干扰素试验组动物攻毒后各项指标较试验前比较没有显著性改变;大体解剖动物肺脏为灰粉色,4只动物肺脏有少量出血,其中1只动物肺脏与胸壁有粘连,组织病理未见典型SARS肺炎性病变。因而认为,重组人干扰素α2b鼻腔喷雾剂可以有效阻断SARS-CoV病毒对恒河猴的感染;;为预防人类感染SARS提供参考。     

SARS-CoV对幼年和成年布氏田鼠的感染研究

采用鼻腔喷雾法(CCID50=105.7)研究了SARS冠状病毒(SARS-CoV)对成年和幼年布氏田鼠的感染效果.成年动物攻毒后出现死亡,表现为口鼻有出血,肠道出血;肺组织呈出血性间质性肺炎改变,肝、脾、肾、胰腺组织均呈淤血性改变;存活动物肺组织呈间质性肺炎,局灶出血及肺气肿改变,其他脏器未见明显病变.幼年动物攻毒后未见死亡但行动较为迟缓,主要脏器未见明显异常;早期肺组织有局限性肺炎改变,且病毒分离为阳性;同居对照组的一只动物有肺组织局灶性肺炎.结果表明,SARS-CoV可以很强地感染布氏田鼠;成年布氏田鼠比幼年动物对SARS-CoV更敏感;布氏田鼠有望成为一种比较理想的小型SARS动物模型。     

SARS冠状病毒的起源研究进展

SARS冠状病毒（SARS-CoV）是一种新现病毒,可感染多种动物,果子狸是人类sARs-CoV重要的动物宿主之一,是已知较理想的实验动物模型。遗传因素在SARS-CoV的出现过程中起重要作用,它很可能是哺乳动物和鸟类冠状病毒之间重组产生的新物种,但发生基因重组不是SARS在人群中暴发的原因。     

SARS冠状病毒的起源研究进展*

SARS冠状病毒(SARS—CoV)是一种新现病毒,可感染多种动物,果子狸是人类SARS—CoV重要的动物宿主之一,是已知较理想的实验动物模型。遗传因素在SARS-CoV的出现过程中起重要作用,它很可能是哺乳动物和鸟类冠状病毒之间重组产生的新物种,但发生基因重组不是SARS在人群中暴发的原因。     

Participation of both host and virus factors in induction of severe acute respiratory syndrome (SARS) in F344 rats infected with SARS coronavirus

To understand the pathogenesis and develop an animal model of severe acute respiratory syndrome (SARS)-associated coronavirus (SARS-CoV), the Frankfurt 1 SARS-CoV isolate was passaged serially in young F344 rats. Young rats were susceptible to SARS-CoV but cleared the virus rapidly within 3 to 5 days of intranasal inoculation. After 10 serial passages, replication and virulence of SARS-CoV were increased in the respiratory tract of young rats without clinical signs. By contrast, adult rats infected with the passaged virus showed respiratory symptoms and severe pathological lesions in the lung. Levels of inflammatory cytokines in sera and lung tissues were significantly higher in adult F344 rats than in young rats. During in vivo passage of SARS-CoV, a single amino acid substitution was introduced within the binding domain of the viral spike protein recognizing angiotensin-converting enzyme 2 (ACE2), which is known as a SARS-CoV receptor. The rat-passaged virus more efficiently infected CHO cells expressing rat ACE2 than did the original isolate. These results strongly indicate that host and virus factors such as advanced age and virus adaptation are critical for the development of SARS in rats.     

The aetiology of SARS: Koch's postulates fulfilled

Proof that a newly identified coronavirus, severe acute respiratory syndrome coronavirus (SARS-CoV) is the primary cause of severe acute respiratory syndrome (SARS) came from a series of studies on experimentally infected cynomolgus macaques (Macaca fascicularis). SARS-CoV-infected macaques developed a disease comparable to SARS in humans; the virus was re-isolated from these animals and they developed SARS-CoV-specific antibodies. This completed the fulfilment of Koch's postulates, as modified by Rivers for viral diseases, for SARS-CoV as the aetiological agent of SARS. Besides the macaque model, a ferret and a cat model for SARS-CoV were also developed. These animal models allow comparative pathogenesis studies for SARS-CoV infections and testing of different intervention strategies. The first of these studies has shown that pegylated interferon-alpha, a drug approved for human use, limits SARS-CoV replication and lung damage in experimentally infected macaques. Finally, we argue that, given the worldwide nature of the socio-economic changes that have predisposed for the emergence of SARS and avian influenza in Southeast Asia, such changes herald the beginning of a global trend for which we are ill prepared.     

Severe acute respiratory syndrome coronavirus infection of human ciliated airway epithelia: role of ciliated cells in viral spread in the conducting airways of the lungs

Severe acute respiratory syndrome coronavirus (SARS-CoV) emerged in 2002 as an important cause of severe lower respiratory tract infection in humans, and in vitro models of the lung are needed to elucidate cellular targets and the consequences of viral infection. The SARS-CoV receptor, human angiotensin 1-converting enzyme 2 (hACE2), was detected in ciliated airway epithelial cells of human airway tissues derived from nasal or tracheobronchial regions, suggesting that SARS-CoV may infect the proximal airways. To assess infectivity in an in vitro model of human ciliated airway epithelia (HAE) derived from nasal and tracheobronchial airway regions, we generated recombinant SARS-CoV by deletion of open reading frame 7a/7b (ORF7a/7b) and insertion of the green fluorescent protein (GFP), resulting in SARS-CoV GFP. SARS-CoV GFP replicated to titers similar to those of wild-type viruses in cell lines. SARS-CoV specifically infected HAE via the apical surface and replicated to titers of 10(7) PFU/ml by 48 h postinfection. Polyclonal antisera directed against hACE2 blocked virus infection and replication, suggesting that hACE2 is the primary receptor for SARS-CoV infection of HAE. SARS-CoV structural proteins and virions localized to ciliated epithelial cells. Infection was highly cytolytic, as infected ciliated cells were necrotic and shed over time onto the luminal surface of the epithelium. SARS-CoV GFP also replicated to a lesser extent in ciliated cell cultures derived from hamster or rhesus monkey airways. Efficient SARS-CoV infection of ciliated cells in HAE provides a useful in vitro model of human lung origin to study characteristics of SARS-CoV replication and pathogenesis.     

The r144 major histocompatibility complex class I-like gene of rat cytomegalovirus is dispensable for both acute and long-term infection in the immunocompromised host

The rat cytomegalovirus (RCMV) r144 gene encodes a polypeptide homologous to major histocompatibility complex class I heavy chains. To study the role of r144 in virus replication, an RCMV r144 null mutant strain (RCMVDeltar144) was generated. This strain replicated with efficiency similar to that of wild-type (WT) RCMV in vitro. Additionally, WT RCMV and RCMVDeltar144 were found not to differ in their replication characteristics in vivo. First, the survival rate was similar among groups of immunosuppressed rats infected with either RCMVDeltar144 or WT RCMV. Second, the dissemination of virus did not differ in either RCMVDeltar144- or WT RCMV-infected, immunosuppressed rats, either in the acute phase of infection or approximately 1 year after infection. These data indicate that the RCMV r144 gene is essential neither for virus replication in the acute phase of infection nor for long-term infection in immunocompromised rats. Interestingly, in a local infection model in which footpads of immunosuppressed rats were inoculated with virus, a significantly higher number of infiltrating macrophage cells as well as of CD8(+) T cells was observed in WT RCMV-infected paws than in RCMVDeltar144-infected paws. This suggests that r144 might function in the interaction with these leukocytes in vivo.     

Lack of Innate Interferon Responses during SARS Coronavirus Infection in a Vaccination and Reinfection Ferret Model

In terms of its highly pathogenic nature, there remains a significant need to further define the immune pathology of SARS-coronavirus (SARS-CoV) infection, as well as identify correlates of immunity to help develop vaccines for severe coronaviral infections. Here we use a SARS-CoV infection-reinfection ferret model and a functional genomics approach to gain insight into SARS immunopathogenesis and to identify correlates of immune protection during SARS-CoV-challenge in ferrets previously infected with SARS-CoV or immunized with a SARS virus vaccine. We identified gene expression signatures in the lungs of ferrets associated with primary immune responses to SARS-CoV infection and in ferrets that received an identical second inoculum. Acute SARS-CoV infection prompted coordinated innate immune responses that were dominated by antiviral IFN response gene (IRG) expression. Reinfected ferrets, however, lacked the integrated expression of IRGs that was prevalent during acute infection. The expression of specific IRGs was also absent upon challenge in ferrets immunized with an inactivated, Al(OH)₃-adjuvanted whole virus SARS vaccine candidate that protected them against SARS-CoV infection in the lungs. Lack of IFN-mediated immune enhancement in infected ferrets that were previously inoculated with, or vaccinated against, SARS-CoV revealed 9 IRG correlates of protective immunity. This data provides insight into the molecular pathogenesis of SARS-CoV and SARS-like-CoV infections and is an important resource for the development of CoV antiviral therapeutics and vaccines.     

Severe acute respiratory syndrome coronavirus evades antiviral signaling: role of nsp1 and rational design of an attenuated strain

The severe acute respiratory syndrome (SARS) epidemic was caused by the spread of a previously unrecognized infectious agent, the SARS-associated coronavirus (SARS-CoV). Here we show that SARS-CoV could inhibit both virus- and interferon (IFN)-dependent signaling, two key steps of the antiviral response. We mapped a strong inhibitory activity to SARS-CoV nonstructural protein 1 (nsp1) and show that expression of nsp1 significantly inhibited the activation of all three virus-dependent signaling pathways. We show that expression of nsp1 significantly inhibited IFN-dependent signaling by decreasing the phosphorylation levels of STAT1 while having little effect on those of STAT2, JAK1, and TYK2. We engineered an attenuated mutant of nsp1 in SARS-CoV through reverse genetics, and the resulting mutant virus was viable and replicated as efficiently as wild-type virus in cells with a defective IFN response. However, mutant virus replication was strongly attenuated in cells with an intact IFN response. Thus, nsp1 is likely a virulence factor that contributes to pathogenicity by favoring SARS-CoV replication.     

Yeast based small molecule screen for inhibitors of SARS-CoV

Severe acute respiratory coronavirus (SARS-CoV) emerged in 2002, resulting in roughly 8000 cases worldwide and 10% mortality. The animal reservoirs for SARS-CoV precursors still exist and the likelihood of future outbreaks in the human population is high. The SARS-CoV papain-like protease (PLP) is an attractive target for pharmaceutical development because it is essential for virus replication and is conserved among human coronaviruses. A yeast-based assay was established for PLP activity that relies on the ability of PLP to induce a pronounced slow-growth phenotype when expressed in S. cerevisiae. Induction of the slow-growth phenotype was shown to take place over a 60-hour time course, providing the basis for conducting a screen for small molecules that restore growth by inhibiting the function of PLP. Five chemical suppressors of the slow-growth phenotype were identified from the 2000 member NIH Diversity Set library. One of these, NSC158362, potently inhibited SARS-CoV replication in cell culture without toxic effects on cells, and it specifically inhibited SARS-CoV replication but not influenza virus replication. The effect of NSC158362 on PLP protease, deubiquitinase and anti-interferon activities was investigated but the compound did not alter these activities. Another suppressor, NSC158011, demonstrated the ability to inhibit PLP protease activity in a cell-based assay. The identification of these inhibitors demonstrated a strong functional connection between the PLP-based yeast assay, the inhibitory compounds, and SARS-CoV biology. Furthermore the data with NSC158362 suggest a novel mechanism for inhibition of SARS-CoV replication that may involve an unknown activity of PLP, or alternatively a direct effect on a cellular target that modifies or bypasses PLP function in yeast and mammalian cells.     

Quantitative analysis of severe acute respiratory syndrome (SARS)-associated coronavirus-infected cells using proteomic approaches: implications for cellular responses to virus infection

We present the first proteomic analysis on the cellular response to severe acute respiratory syndrome-associated coronavirus (SARS-CoV) infection. The differential proteomes of Vero E6 cells with and without infection of the SARS-CoV were resolved and quantitated with two-dimensional differential gel electrophoresis followed by ESI-MS/MS identification. Moreover isotope-coded affinity tag technology coupled with two-dimensional LC-MS/MS were also applied to the differential proteins of infected cells. By combining these two complementary strategies, 355 unique proteins were identified and quantitated with 186 of them differentially expressed (at least 1.5-fold quantitative alteration) between infected and uninfected Vero E6 cells. The implication for cellular responses to virus infection was analyzed in depth according to the proteomic results. Thus, the present work provides large scale protein-related information to investigate the mechanism of SARS-CoV infection and pathogenesis.