Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1175175 (SARS)
 19,188 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human monoclonal antibodies (MAbs) were selected from semisynthetic antibody phage display libraries by using whole irradiated severe acute respiratory syndrome (SARS) coronavirus (CoV) virions as target. We identified eight human MAbs binding to virus and infected cells, six of which could be mapped to two SARS-CoV structural proteins: the nucleocapsid (N) and spike (S) proteins. Two MAbs reacted with N protein. One of the N protein MAbs recognized a linear epitope conserved between all published human and animal SARS-CoV isolates, and the other bound to a nonlinear N epitope. These two N MAbs did not compete for binding to SARS-CoV. Four MAbs reacted with the S glycoprotein, and three of these MAbs neutralized SARS-CoV in vitro. All three neutralizing anti-S MAbs bound a recombinant S1 fragment comprising residues 318 to 510, a region previously identified as the SARS-CoV S receptor binding domain; the nonneutralizing MAb did not. Two strongly neutralizing anti-S1 MAbs blocked the binding of a recombinant S fragment (residues 1 to 565) to SARS-CoV-susceptible Vero cells completely, whereas a poorly neutralizing S1 MAb blocked binding only partially. The MAb ability to block S1-receptor binding and the level of neutralization of the two strongly neutralizing S1 MAbs correlated with the binding affinity to the S1 domain. Finally, epitope mapping, using recombinant S fragments (residues 318 to 510) containing naturally occurring mutations, revealed the importance of residue N479 for the binding of the most potent neutralizing MAb, CR3014. The complete set of SARS-CoV MAbs described here may be useful for diagnosis, chemoprophylaxis, and therapy of SARS-CoV infection and disease.
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PMID:Molecular and biological characterization of human monoclonal antibodies binding to the spike and nucleocapsid proteins of severe acute respiratory syndrome coronavirus. 1565 Jan 89

We have identified the membrane-active regions of the severe acute respiratory syndrome coronavirus (SARS CoV) spike glycoprotein by determining the effect on model membrane integrity of a 16/18-mer SARS CoV spike glycoprotein peptide library. By monitoring the effect of this peptide library on membrane leakage in model membranes, we have identified three regions on the SARS CoV spike glycoprotein with membrane-interacting capabilities: region 1, located immediately upstream of heptad repeat 1 (HR1) and suggested to be the fusion peptide; region 2, located between HR1 and HR2, which would be analogous to the loop domain of human immunodeficiency virus type 1; and region 3, which would correspond to the pretransmembrane region. The identification of these membrane-active regions, which are capable of modifying the biophysical properties of phospholipid membranes, supports their direct role in SARS CoV-mediated membrane fusion, as well as facilitating the future development of SARS CoV entry inhibitors.
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PMID:Identification of the membrane-active regions of the severe acute respiratory syndrome coronavirus spike membrane glycoprotein using a 16/18-mer peptide scan: implications for the viral fusion mechanism. 1565 Jan 99

Coronavirus (CoV) entry is mediated by the viral spike (S) glycoprotein, a class I viral fusion protein. During viral and target cell membrane fusion, the heptad repeat (HR) regions of the S2 subunit assume a trimer-of-hairpins structure, positioning the fusion peptide in close proximity to the C-terminal region of the ectodomain. The formation of this structure appears to drive apposition and subsequent fusion of viral and target cell membranes; however, the exact mechanism is unclear. Here, we characterize an aromatic amino acid rich region within the ectodomain of the S2 subunit that both partitions into lipid membranes and has the capacity to perturb lipid vesicle integrity. Circular dichroism analysis indicated that peptides analogous to the aromatic domains of the severe acute respiratory syndrome (SARS)-CoV, mouse hepatitis virus (MHV) and the human CoV OC43 S2 subunits, did not have a propensity for a defined secondary structure. These peptides strongly partitioned into lipid membranes and induced lipid vesicle permeabilization at peptide/lipid ratios of 1:100 in two independent leakage assays. Thus, partitioning of the peptides into the lipid interface is sufficient to disorganize membrane integrity. Our study of the S2 aromatic domain of three CoVs provides supportive evidence for a functional role of this region. We propose that, when aligned with the fusion peptide and transmembrane domains during membrane apposition, the aromatic domain of the CoV S protein functions to perturb the target cell membrane and provides a continuous track of hydrophobic surface, resulting in lipid-membrane fusion and subsequent viral nucleocapsid entry.
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PMID:The aromatic domain of the coronavirus class I viral fusion protein induces membrane permeabilization: putative role during viral entry. 1565 51

Spike glycoprotein of SARS coronavirus (S protein) plays a pivotal role in SARS coronavirus (SARS_CoV) infection. The immunological fragment of the S protein (Ala251-His641, SARS_S1b) is believed to be essential for SARS_CoV entering the host cell through S protein-ACE-2 interaction. We have quantitatively characterized the thermally induced and GuHCl-induced unfolding features of SARS_S1b using circular dichroism (CD), tryptophan fluorescence, and stopped-flow spectral techniques. For the thermally induced unfolding at pH 7.4, the apparent activation energy (E(app)) and transition midpoint temperature (Tm) were determined to be 16.3 +/- 0.2 kcal/mol and 52.5 +/- 0.4 degrees C, respectively. The CD spectra are not dependent on temperature, suggesting that the secondary structure of SARS_S1b has a relatively high thermal stability. GuHCl strongly affected SARS_S1b structure. Both the CD and fluorescent spectra resulted in consistent values of the transition middle concentration of the denaturant (Cm, ranging from 2.30 to 2.45 M) and the standard free energy change (deltaG(o), ranging from 2.1 to 2.5 kcal/mol) for the SARS_S1b unfolding reaction. Moreover, the kinetic features of the chemical unfolding and refolding of SARS_S1b were also characterized using a stopped-flow CD spectral technique. The obvious unfolding reaction rates and relaxation times were determined at various GuHCl concentrations, and the Cm value was obtained, which is very close to the data that resulted from CD and fluorescent spectral determinations. Secondary and three-dimensional structural predictions by homology modeling indicated that SARS_S1b folded as a globular-like structure by beta-sheets and loops; two of the four tryptophans are located on the protein surface, which is in agreement with the tryptophan fluorescence result. The three-dimensional model was also used to explain the recently published experimental results of S1-ACE-2 binding and immunizations.
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PMID:Folding of the SARS coronavirus spike glycoprotein immunological fragment (SARS_S1b): thermodynamic and kinetic investigation correlating with three-dimensional structural modeling. 1568 30

Immunization with a killed or inactivated viral vaccine provides significant protection in animals against challenge with certain corresponding pathogenic coronaviruses (CoVs). However, the promise of this approach in humans is hampered by serious concerns over the risk of leaking live severe acute respiratory syndrome (SARS) viruses. In this study, we generated a SARS vaccine candidate by using the live-attenuated modified vaccinia virus Ankara (MVA) as a vector. The full-length SARS-CoV envelope Spike (S) glycoprotein gene was introduced into the deletion III region of the MVA genome. The newly generated recombinant MVA, ADS-MVA, is replication incompetent in mammalian cells and highly immunogenic in terms of inducing potent neutralizing antibodies in mice, rabbits, and monkeys. After two intramuscular vaccinations with ADS-MVA alone, the 50% inhibitory concentration in serum was achieved with reciprocal sera dilutions of more than 1,000- to 10,000-fold in these animals. Using fragmented S genes as immunogens, we also mapped a neutralizing epitope in the region of N-terminal 400 to 600 amino acids of the S glycoprotein (S400-600), which overlaps with the angiotensin-converting enzyme 2 (ACE2) receptor-binding region (RBR; S318-510). Moreover, using a recombinant soluble RBR-Fc protein, we were able to absorb and remove the majority of the neutralizing antibodies despite observing that the full S protein tends to induce a broader spectrum of neutralizing activities in comparison with fragmented S proteins. Our data suggest that a major mechanism for neutralizing SARS-CoV likely occurs through blocking the interaction between virus and the cellular receptor ACE2. In addition, ADS-MVA induced potent immune responses which very likely protected Chinese rhesus monkeys from pathogenic SARS-CoV challenge.
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PMID:Recombinant modified vaccinia virus Ankara expressing the spike glycoprotein of severe acute respiratory syndrome coronavirus induces protective neutralizing antibodies primarily targeting the receptor binding region. 1570 87

Foreign viral proteins expressed by rabies virus (RV) have been shown to induce potent humoral and cellular immune responses in immunized animals. In addition, highly attenuated and, therefore, very safe RV-based vectors have been constructed. Here, an RV-based vaccine vehicle was utilized as a novel vaccine against severe acute respiratory syndrome coronavirus (SARS-CoV). For this approach, the SARS-CoV nucleocapsid protein (N) or envelope spike protein (S) genes were cloned between the RV glycoprotein G and polymerase L genes. Recombinant vectors expressing SARS-CoV N or S protein were recovered and their immunogenicity was studied in mice. A single inoculation with the RV-based vaccine expressing SARS-CoV S protein induced a strong SARS-CoV-neutralizing antibody response. The ability of the RV-SARS-CoV S vector to confer immunity after a single inoculation makes this live vaccine a promising candidate for eradication of SARS-CoV in animal reservoirs, thereby reducing the risk of transmitting the infection to humans.
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PMID:A single immunization with a rhabdovirus-based vector expressing severe acute respiratory syndrome coronavirus (SARS-CoV) S protein results in the production of high levels of SARS-CoV-neutralizing antibodies. 1583 55

The coronavirus spike glycoprotein is a class I membrane fusion protein with two characteristic heptad repeat regions (HR1 and HR2) in its ectodomain. Here, we report the X-ray structure of a previously characterized HR1/HR2 complex of the severe acute respiratory syndrome coronavirus spike protein. As expected, the HR1 and HR2 segments are organized in antiparallel orientations within a rod-like molecule. The HR1 helices form an exceptionally long (120 A) internal coiled coil stabilized by hydrophobic and polar interactions. A striking arrangement of conserved asparagine and glutamine residues of HR1 propagates from two central chloride ions, providing hydrogen-bonding "zippers" that strongly constrain the path of the HR2 main chain, forcing it to adopt an extended conformation at either end of a short HR2 alpha-helix.
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PMID:Central ions and lateral asparagine/glutamine zippers stabilize the post-fusion hairpin conformation of the SARS coronavirus spike glycoprotein. 1584 May 26

Polyclonal antibodies have a century-old history of being effective against some viruses and, recently, monoclonal antibodies (mAbs) have also shown some clinical success. Human mAbs to the severe acute respiratory syndrome (SARS) coronavirus spike glycoprotein have been developed by several research groups at an amazing pace. These antibodies potently neutralize infectious virus in tissue cultures and animal models, and, alone or in combination with vaccines and other drugs, may have potential for the prevention and treatment of SARS.
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PMID:Human monoclonal antibodies to the S glycoprotein and related proteins as potential therapeutics for SARS. 1584 23

Severe acute respiratory syndrome-associated coronavirus (SARS-CoV) is a newly identified member of the family Coronaviridae and poses a serious public health threat. Recent studies indicated that the SARS-CoV viral spike glycoprotein is a class I viral fusion protein. A fusion peptide present at the N-terminal region of class I viral fusion proteins is believed to initiate viral and cell membrane interactions and subsequent fusion. Although the SARS-CoV fusion protein heptad repeats have been well characterized, the fusion peptide has yet to be identified. Based on the conserved features of known viral fusion peptides and using Wimley and White interfacial hydrophobicity plots, we have identified two putative fusion peptides (SARS(WW-I) and SARS(WW-II)) at the N terminus of the SARS-CoV S2 subunit. Both peptides are hydrophobic and rich in alanine, glycine, and/or phenylalanine residues and contain a canonical fusion tripeptide along with a central proline residue. Only the SARS(WW-I) peptide strongly partitioned into the membranes of large unilamellar vesicles (LUV), adopting a beta-sheet structure. Likewise, only SARS(WW-I) induced the fusion of LUV and caused membrane leakage of vesicle contents at peptide/lipid ratios of 1:50 and 1:100, respectively. The activity of this synthetic peptide appeared to be dependent on its amino acid (aa) sequence, as scrambling the peptide rendered it unable to partition into LUV, assume a defined secondary structure, or induce both fusion and leakage of LUV. Based on the activity of SARS(WW-I), we propose that the hydrophobic stretch of 19 aa corresponding to residues 770 to 788 is a fusion peptide of the SARS-CoV S2 subunit.
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PMID:Identification and characterization of the putative fusion peptide of the severe acute respiratory syndrome-associated coronavirus spike protein. 1589 Sep 58

The fusion subunit of the SARS-CoV S glycoprotein contains two regions of hydrophobic heptad-repeat amino acid sequences that have been shown in biophysical studies to form a six-helix bundle structure typical of the fusion-active core found in Class I viral fusion proteins. Here, we have applied serine-scanning mutagenesis to the C-terminal-most heptad-repeat region in the SARS-CoV S glycoprotein to investigate the functional role of this region in membrane fusion. We show that hydrophobic sidechains at a and d positions only within the short helical segment of the C-terminal heptad-repeat region (I1161, I1165, L1168, A1172, and L1175) are critical for cell-cell fusion. Serine mutations at outlying heptad-repeat residues that form an extended chain in the core structure (V1158, L1179, and L1182) do not affect fusogenicity. Our study provides genetic evidence for the important role of alpha-helical packing in promoting S glycoprotein-mediated membrane fusion.
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PMID:Serine-scanning mutagenesis studies of the C-terminal heptad repeats in the SARS coronavirus S glycoprotein highlight the important role of the short helical region. 1608 Nov 24


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