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Query: UMLS:C1175175 (SARS)
 19,188 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Severe acute respiratory syndrome (SARS) is caused by a newly emerged coronavirus (CoV) designated SARS-CoV. The virus utilizes angiotensin-converting enzyme 2 (ACE2) as the primary receptor. Although the idea is less clear and somewhat controversial, SARS-CoV is thought to use C-type lectins DC-SIGN and/or L-SIGN (collectively referred to as DC/L-SIGN) as alternative receptors or as enhancer factors that facilitate ACE2-mediated virus infection. In this study, the function of DC/L-SIGN in SARS-CoV infection was examined in detail. The results of our study clearly demonstrate that both proteins serve as receptors independently of ACE2 and that there is a minimal level of synergy between DC/L-SIGN and ACE2. As expected, glycans on spike (S) glycoprotein are important for DC/L-SIGN-mediated virus infection. Site-directed mutagenesis analyses have identified seven glycosylation sites on the S protein critical for DC/L-SIGN-mediated virus entry. They include asparagine residues at amino acid positions 109, 118, 119, 158, 227, 589, and 699, which are distinct from residues of the ACE2-binding domain (amino acids 318 to 510). Amino acid sequence analyses of S proteins encoded by viruses isolated from animals and humans suggest that glycosylation sites N227 and N699 have facilitated zoonotic transmission.
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PMID:Specific asparagine-linked glycosylation sites are critical for DC-SIGN- and L-SIGN-mediated severe acute respiratory syndrome coronavirus entry. 1771 38

Severe acute respiratory syndrome (SARS) is an acute respiratory disease with significant morbidity and mortality. While its clinical manifestations have been extensively studied, its pathogenesis is not yet fully understood. A limited number of autopsy studies have revealed that the lungs and the immune system are the organs that sustain the most severe damage. Other organs affected include the kidneys, brain, digestive tract, heart, liver, thyroid gland and urogenital tract. The primary target cells are pneumocytes and enterocytes, both cell types abundantly expressing angiotensin-converting enzyme 2 which is the main SARS-CoV receptor. Other cell types infected include the epithelial cells of renal tubules, cerebral neurons, and immune cells. The pathology of this disease results from both direct and indirect injury. Direct injury is caused by infection of the target cells by the virus. Indirect injury mainly results from immune responses, circulatory dysfunction, and hypoxia. In this review, we summarize the major pathological findings at the gross, cellular and molecular levels and discuss the various possible mechanisms that may contribute to the pathogenesis of SARS. The implications of the proposed pathogenesis for prevention, diagnosis and therapy of the disease are discussed.
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PMID:Pathogenetic mechanisms of severe acute respiratory syndrome. 1782 37

Identification of the nature of severe acute respiratory syndrome (SARS)-infected cells is crucial toward understanding the pathogenesis. Using multicolor colocalization techniques, we previously reported that SARS(+) cells in the lung of fatally infected patients expressed the only known functional receptor, angiotensin-converting enzyme 2, and also a binding receptor, liver/lymph node-specific ICAM-3-grabbing non-integrin (CD209L). In this study, we show that SARS-infected cells also express the stem/progenitor cell markers CD34 and Oct-4, and do not express cytokeratin or surfactant. These putative lung stem/progenitor cells can also be identified in some non-SARS individuals and can be infected by SARS-coronavirus ex vivo. Infection of these cells may contribute to the loss of lung repair capacity that leads to respiratory failure as clinically observed.
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PMID:A novel subset of putative stem/progenitor CD34+Oct-4+ cells is the major target for SARS coronavirus in human lung. 1792 1

The identification in 2003 of a coronavirus as the aetiological agent of severe acute respiratory syndrome (SARS) intensified efforts to understand the biology of coronaviruses in general and SARS coronavirus (SARS-CoV) in particular. Rapid progress was made in describing the SARS-CoV genome, evolution and lifecycle. Identification of angiotensin-converting enzyme 2 (ACE2) as an obligate cellular receptor for SARS-CoV contributed to understanding of the SARS-CoV entry process, and helped to characterize two targets of antiviral therapeutics: the SARS-CoV spike protein and ACE2. Here we describe the role of these proteins in SARS-CoV replication and potential therapeutic strategies aimed at preventing entry of SARS-CoV into target cells.
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PMID:Severe acute respiratory syndrome coronavirus entry as a target of antiviral therapies. 1794 71

The SARS coronavirus (SARS-CoV) spike is the largest known viral spike molecule, and shares a similar function with all class 1 viral fusion proteins. Previous structural studies of membrane fusion proteins have largely used crystallography of static molecular fragments, in isolation of their transmembrane domains. In this study we have produced purified, irradiated SARS-CoV virions that retain their morphology, and are fusogenic in cell culture. We used cryo-electron microscopy and image processing to investigate conformational changes that occur in the entire spike of intact virions when they bind to the viral receptor, angiotensin-converting enzyme 2 (ACE2). We have shown that ACE2 binding results in structural changes that appear to be the initial step in viral membrane fusion, and precisely localized the receptor-binding and fusion core domains within the entire spike. Furthermore, our results show that receptor binding and subsequent membrane fusion are distinct steps, and that each spike can bind up to three ACE2 molecules. The SARS-CoV spike provides an ideal model system to study receptor binding and membrane fusion in the native state, employing cryo-electron microscopy and single-particle image analysis.
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PMID:Conformational reorganization of the SARS coronavirus spike following receptor binding: implications for membrane fusion. 1795 64

To establish a small animal model of severe acute respiratory syndrome (SARS), we developed a mouse model of human severe acute respiratory syndrome coronavirus (SARS-CoV) infection by introducing the human gene for angiotensin-converting enzyme 2 (hACE2) (the cellular receptor of SARS-CoV), driven by the mouse ACE2 promoter, into the mouse genome. The hACE2 gene was expressed in lung, heart, kidney, and intestine. We also evaluated the responses of wild-type and transgenic mice to SARS-CoV inoculation. At days 3 and 7 postinoculation, SARS-CoV replicated more efficiently in the lungs of transgenic mice than in those of wild-type mice. In addition, transgenic mice had more severe pulmonary lesions, including interstitial hyperemia and hemorrhage, monocytic and lymphocytic infiltration, protein exudation, and alveolar epithelial cell proliferation and desquamation. Other pathologic changes, including vasculitis, degeneration, and necrosis, were found in the extrapulmonary organs of transgenic mice, and viral antigen was found in brain. Therefore, transgenic mice were more susceptible to SARS-CoV than were wild-type mice, and susceptibility was associated with severe pathologic changes that resembled human SARS infection. These mice will be valuable for testing potential vaccine and antiviral drug therapies and for furthering our understanding of SARS pathogenesis.
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PMID:Mice transgenic for human angiotensin-converting enzyme 2 provide a model for SARS coronavirus infection. 1797 27

Severe acute respiratory syndrome (SARS) is caused by the SARS-associated coronavirus (SARS-CoV), which uses angiotensin-converting enzyme 2 (ACE2) as its receptor for cell entry. A group of SARS-like CoVs (SL-CoVs) has been identified in horseshoe bats. SL-CoVs and SARS-CoVs share identical genome organizations and high sequence identities, with the main exception of the N terminus of the spike protein (S), known to be responsible for receptor binding in CoVs. In this study, we investigated the receptor usage of the SL-CoV S by combining a human immunodeficiency virus-based pseudovirus system with cell lines expressing the ACE2 molecules of human, civet, or horseshoe bat. In addition to full-length S of SL-CoV and SARS-CoV, a series of S chimeras was constructed by inserting different sequences of the SARS-CoV S into the SL-CoV S backbone. Several important observations were made from this study. First, the SL-CoV S was unable to use any of the three ACE2 molecules as its receptor. Second, the SARS-CoV S failed to enter cells expressing the bat ACE2. Third, the chimeric S covering the previously defined receptor-binding domain gained its ability to enter cells via human ACE2, albeit with different efficiencies for different constructs. Fourth, a minimal insert region (amino acids 310 to 518) was found to be sufficient to convert the SL-CoV S from non-ACE2 binding to human ACE2 binding, indicating that the SL-CoV S is largely compatible with SARS-CoV S protein both in structure and in function. The significance of these findings in relation to virus origin, virus recombination, and host switching is discussed.
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PMID:Difference in receptor usage between severe acute respiratory syndrome (SARS) coronavirus and SARS-like coronavirus of bat origin. 1807 25

In 2003, severe acute respiratory syndrome coronavirus (SARS-CoV) emerged and caused over 8,000 human cases of infection and more than 700 deaths worldwide. Zoonotic SARS-CoV likely evolved to infect humans by a series of transmission events between humans and animals for sale in China. Using synthetic biology, we engineered the spike protein (S) from a civet strain, SZ16, into our epidemic strain infectious clone, creating the chimeric virus icSZ16-S, which was infectious but yielded progeny viruses incapable of propagating in vitro. After introducing a K479N mutation within the S receptor binding domain (RBD) of SZ16, the recombinant virus (icSZ16-S K479N) replicated in Vero cells but was severely debilitated in growth. The in vitro evolution of icSZ16-S K479N on human airway epithelial (HAE) cells produced two viruses (icSZ16-S K479N D8 and D22) with enhanced growth on HAE cells and on delayed brain tumor cells expressing the SARS-CoV receptor, human angiotensin I converting enzyme 2 (hACE2). The icSZ16-S K479N D8 and D22 virus RBDs contained mutations in ACE2 contact residues, Y442F and L472F, that remodeled S interactions with hACE2. Further, these viruses were neutralized by a human monoclonal antibody (MAb), S230.15, but the parent icSZ16-S K479N strain was eight times more resistant than the mutants. These data suggest that the human adaptation of zoonotic SARS-CoV strains may select for some variants that are highly susceptible to select MAbs that bind to RBDs. The epidemic, icSZ16-S K479N, and icSZ16-S K479N D22 viruses replicate similarly in the BALB/c mouse lung, highlighting the potential use of these zoonotic spike SARS-CoVs to assess vaccine or serotherapy efficacy in vivo.
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PMID:Mechanisms of zoonotic severe acute respiratory syndrome coronavirus host range expansion in human airway epithelium. 1809 88

The severe acute respiratory syndrome coronavirus (SARS-CoV) spike glycoprotein (S) is a class I viral fusion protein that binds to its receptor glycoprotein, human angiotensin converting enzyme 2 (hACE2), and mediates virus entry and cell-cell fusion. The juxtamembrane domain (JMD) of S is an aromatic amino acid-rich region proximal to the transmembrane domain that is highly conserved in all coronaviruses. Alanine substitutions for one or two of the six aromatic residues in the JMD did not alter the surface expression of the SARS-CoV S proteins with a deletion of the C-terminal 19 amino acids (S Delta19) or reduce binding to soluble human ACE2 (hACE2). However, hACE2-dependent entry of trypsin-treated retrovirus pseudotyped viruses expressing JMD mutant S Delta19 proteins was greatly reduced. Single alanine substitutions for aromatic residues reduced entry to 10 to 60% of the wild-type level. The greatest reduction was caused by residues nearest the transmembrane domain. Four double alanine substitutions reduced entry to 5 to 10% of the wild-type level. Rapid hACE2-dependent S-mediated cell-cell fusion was reduced to 60 to 70% of the wild-type level for all single alanine substitutions and the Y1188A/Y1191A protein. S Delta19 proteins with other double alanine substitutions reduced cell-cell fusion further, from 40% to less than 20% of wild-type levels. The aromatic amino acids in the JMD of the SARS-CoV S glycoprotein play critical roles in receptor-dependent virus-cell and cell-cell fusion. Because the JMD is so highly conserved in all coronavirus S proteins, it is a potential target for development of drugs that may inhibit virus entry and/or cell-cell fusion mediated by S proteins of all coronaviruses.
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PMID:Aromatic amino acids in the juxtamembrane domain of severe acute respiratory syndrome coronavirus spike glycoprotein are important for receptor-dependent virus entry and cell-cell fusion. 1819 53

While severe acute respiratory syndrome coronavirus (SARS-CoV) was initially thought to enter cells through direct fusion with the plasma membrane, more recent evidence suggests that virus entry may also involve endocytosis. We have found that SARS-CoV enters cells via pH- and receptor-dependent endocytosis. Treatment of cells with either SARS-CoV spike protein or spike-bearing pseudoviruses resulted in the translocation of angiotensin-converting enzyme 2 (ACE2), the functional receptor of SARS-CoV, from the cell surface to endosomes. In addition, the spike-bearing pseudoviruses and early endosome antigen 1 were found to colocalize in endosomes. Further analyses using specific endocytic pathway inhibitors and dominant-negative Eps15 as well as caveolin-1 colocalization study suggested that virus entry was mediated by a clathrin- and caveolae-independent mechanism. Moreover, cholesterol- and sphingolipid-rich lipid raft microdomains in the plasma membrane, which have been shown to act as platforms for many physiological signaling pathways, were shown to be involved in virus entry. Endocytic entry of SARS-CoV may expand the cellular range of SARS-CoV infection, and our findings here contribute to the understanding of SARS-CoV pathogenesis, providing new information for anti-viral drug research.
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PMID:SARS coronavirus entry into host cells through a novel clathrin- and caveolae-independent endocytic pathway. 1822 61


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