cord-015235-lv8mll28	2014	The receptor-binding domain (RBD) positioned in S1 can specifically bind to angiotensin-converting enzyme 2 (ACE2) on target cells, and ACE2 regulates the balance between vasoconstrictors and vasodilators within the heart and kidneys. Infection of SARS-CoV is initiated by binding of the S protein to the angiotensin-converting enzyme 2 (ACE2) functional receptor expressed on target cells (Li et al. Our cellular enzyme-linked immunosorbent assay (ELISA) and competitive binding assay using a polyclonal ACE2 antibody indicated that our prepared recombinant RBD fusion protein binds to various tissues as well as NIH3T3 and HEK293 cells through ACE2. After washing with PBS, the RBD fusion protein was incubated for 1 h at room temperature to bind with the ACE2 molecules on the cell membranes. Next, we examined whether RBD binding was blocked by the ACE2 antibody in a Western blot using mouse tissue cell lysates with a pair of membranes.
cord-024319-isbqs7hg	2020	title: Isolation of a human monoclonal antibody specific for the receptor binding domain of SARS-CoV-2 using a competitive phage biopanning strategy SARS-CoV-2 relies on its spike protein, in particular the receptor binding domain (RBD), to bind human cell receptor angiotensin-converting enzyme 2 (ACE2) for viral entry, and thus targeting RBD holds the promise for preventing SARS-CoV-2 infection. It was proved to competitively block the binding of RBD to ACE2 and potently inhibit SARS-CoV-2 pseudovirus infection with IC(50) values of 12 nM. Several high-affinity antibodies targeting SARS-CoV-2 RBD and blocking its binding to ACE2 were isolated, and the top 1 lead exhibited a neutralization activity of SARS-CoV-2 pseudotyped VSV infection. These antibodies all compete with ACE2 to bind SARS-CoV RBD, but their epitopes only have limited overlaps of the Two SARS-CoV-2 RBD-specific antibodies selected from different strategies showed different neutralization activities.
cord-102920-z5q3wo7v	2020	Previous reports using structural analysis of the viral spike protein (S) binding its cell receptor of angiotensin-converting enzyme 2 (ACE2), indicate a broad SARS-CoV2 susceptibility in wild and particularly domestic animals. In addition to showing a broad susceptibility potential across mammalian species based on structural analysis, our results also reveal that domestic animals including dogs, pigs, cattle and goats may evolve ACE2-related immunogenetic diversity to restrict SARS-CoV2 infections. Along with showing a broad susceptibility potential across mammalian species based on structural analysis [26] [27] [28] , our results further reveal that domestic animals including dogs, pigs, cattle and goats may evolve previously unexamined immunogenetic diversity to restrict SARS-CoV2 infections. In addition to structural analysis of simulated S-RBD-ACE2 interaction, we propose that several immunogenetic factors, including the evolution of S-binding-void ACE2 isoforms in some domestic animals, the species-specific IFN system, and epigenetic regulation of IFN-stimulated property of host ACE2 genes, contribute to the viral susceptibility and the development of COVID-19-like symptoms in certain animal species [15, 38, 39, 49] .
cord-103940-a2cqw8kg	2020	Currently, structural studies have shown that Alpha-coronavirus (HCoV-229E) and Beta-coronavirus (SARS-CoV and SARS-CoV-2) RBDs are in lying and standing state, respectively. In this study, 130 we selected SARS-CoV, SARS-CoV-2, and HCoV-229E as models, which adopt the 131 two RBD states, and evaluated and compared immune responses to the S trimers and 132 7 RBDs of these coronaviruses through immunological and bioinformatics approaches. 133 We also investigated the mechanism through which the HCoV-229E S trimer 134 produced effective nAbs. Finally, we provide possible vaccine strategies for alphaTo address this issue, we performed B-cell epitope predictions for the S trimers 152 and RBDs of alpha-CoV (HCoV-229E) and beta-CoVs (SARS-CoV and 153 SARS-CoV-2). Taken together, these results showed that the intact and stable S1 subunit of 240 HCoV-229E is a prerequisite for the production of effective nAbs. Furthermore, our experimental results show that RBD has a higher ability to bind 242 12 to the receptor hAPN (Fig. 4B) , which indicates that the characteristics of RBD itself 243 may lead to the generation of less neutralizing antibodies.
cord-133453-23rfdkuw	2020	By integrating genetics, biophysics, deep learning, and algebraic topology, we deduce that some of the mutations such as M153I, S254F, and S255F may weaken the binding of S protein and antibodies, and potentially disrupt the efficacy and reliability of antibody therapies and vaccines in the development. The vaccination mechanism is to stimulate the primary immune response of the human body, which will activate T cells and B cells to generate the antibodies and long-lived memory cells that prevent infectious diseases, which is one of the most effective and economical means for combating with COVID-19 at this stage. Notably, understanding how mutations have changed the SARS-CoV-2 structure, function, infectivity, activity, and virulence is of great importance for coming up with life-saving strategies in virus control, containment, prevention, and medication, especially in the antibodies and vaccines development. Next, we study the BFE changes ∆∆G induced by 39 mutations on the SARS-CoV-2 S protein RBD for the antibody Fab 2-4 (PDB: 6XEY) in Figure 6 .
cord-183197-dxmto1tu	2020	Tetracycline appears to target viral residues that are usually involved in significant hydrogen bonding with ACE2; this inhibition of cellular infection complements the anti-inflammatory and cytokine suppressing capability of Tetracycline, and may further reduce the duration of ICU stays and mechanical ventilation induced by the coronavirus SARS-CoV-2. The amino acid residues of the RBD involved in hydrogen bonding with the Tetracycline molecule are Tyr 449, Asn 501, Gly 496, and Tyr 505 (Fig. 1) , which have been shown to be crucial for the SARS-CoV 2 RBD in binding to ACE2 for cellular access 8 . To verify this statement, steered molecular dynamics simulations were carried out to find the potential of mean force (PMF) along a singular dissociation pathway for the inhibited and uninhibited RBD-ACE2 complexes. The tetracycline class of antibiotics, including Tetracycline, Oxytetracycline, and Doxycycline may be helpful in the fight against the coronavirus SARS-CoV-2, due to its preferential association with the important residues in the viral receptor binding domain and the resulting strong inhibition of the RBD-ACE2 complex.
cord-252919-647zcjgu	2020	We performed a structural analysis of the receptor binding domain (RBD) of spike glycoprotein responsible for entry of coronaviruses into host cells. Structural analysis suggests that ACE2 from these animals can potentially bind RBD of 2019-nCoV, making them all possible natural hosts for the virus. In this study, we analyzed the structure of spike glycoprotein RBD of 2019-nCoV and identified a unique feature that potentially allows a high affinity binding to ACE2 in human cells. There are 16 amino acid residues in SARS-CoV RBD that are directly in contact with ACE2, of which 8 are conserved in 2019-nCoV (see Fig. 1B ). Among the 16 amino acid residues in RBD of SARS that are in contact with ACE2, 14, 14, 7, and 8 are shared by SARSv, civet, bat, and 2019-nCoV, respectively (Fig. 1B) . Our study suggests unique structural features of the spike glycoprotein RBD of 2019-nCoV that confers potentially higher affinity binding for its receptor than found with SARS-CoV.
cord-253438-k8iqv1jb	2020	We found that ACE2 orthologs of a wide range of domestic and wild mammals, including camels, cattle, horses, goats, sheep, cats, rabbits, and pangolins, were able to support cell entry of SARS-CoV-2, suggesting that these species might be able to harbor and spread this virus. In this study, we found that ACE2 orthologs of a wide range of domestic and wild animals can support cell entry of SARS-CoV-2 and three related coronaviruses, providing insights into identifying animal hosts of these viruses. The RBD of Bat-CoV RaTG13 then showed a binding profile significantly different and narrower than the other three RBDs. Note that human ACE2 and ACE2 orthologs of some domestic animals, including camels, cattle, horses, goats, sheep, cats, and rabbits, support efficient binding to all the four tested RBDs, suggesting that these ACE2 orthologs might be generally functional for supporting cell entry of the four tested viruses.
cord-253447-4w6caxwu	2020	title: Blocking antibodies against SARS-CoV-2 RBD isolated from a phage display antibody library using a competitive biopanning strategy SARS-CoV-2 relies on its spike protein, in particular the receptor binding domain (RBD), to bind human cell receptor angiotensin-converting enzyme 2 (ACE2) for viral entry, and thus targeting RBD holds the promise for preventing SARS-CoV-2 infection. In this work, a competitive biopanning strategy of a phage display antibody library was applied to screen blocking antibodies against RBD. It was proved to competitively block the binding of RBD to ACE2 protein, and potently inhibit SARS-CoV-2 pseudovirus infection of ACE2-overexpressing Hela cells with IC50 values of 12nM. Several high-affinity antibodies targeting SARS-CoV-2 RBD and blocking its binding to ACE2 were isolated, and the top 1 lead exhibited a neutralization activity of SARS-CoV-2 pseudotyped VSV infection. A high-affinity antibody against the target protein can be screened from a phage display antibody library using the standard biopanning process, but its binding epitopes are identified by some extra steps, such as epitope mapping and competitive ELISA.
cord-254735-8reu45yz	2012	Here we describe the crystal structures of the receptor-binding domains (RBDs) of two closely related CoV strains, transmissible gastroenteritis virus (TGEV) and porcine respiratory CoV (PRCV), in complex with their receptor, porcine APN (pAPN), or with a neutralizing antibody. The report uncovers a unique virus-receptor recognition mode that engages a glycan N-linked to the pAPN ectodomain, revealing structural determinants of the receptor-binding specificity in CoVs. Neutralizing antibodies target viral residues used for binding to the APN receptor and entry into host cells, showing that efficient CoV neutralization requires immune responses focused toward key receptor binding motifs in the virus envelope. The RBD tip, shown here as the pAPN-binding edge of the domain (Figure 3) , is the main S protein determinant of antigenic site A, recognized by the most effective neutralizing antibodies of TGEV and related CoV infections [25, 26] .
cord-256156-mywhe6w9	2020	We show that SARS-CoV-2 spike protein interacts with both cellular heparan sulfate and angiotensin converting enzyme 2 (ACE2) through its Receptor Binding Domain (RBD). Unfractionated heparin, non-anticoagulant heparin, heparin lyases, and lung heparan sulfate potently block spike protein binding and/or infection by pseudotyped virus and authentic SARS-CoV-2 virus. In this report, we show that the ectodomain of the SARS-CoV-2 spike (S) protein interacts with cell surface HS through the Receptor Binding Domain (RBD) in the S1 subunit. Adjacent to the ACE2 binding site and exposed in the RBD lies a group of positively-charged amino acid residues that represents a potential site that could interact with heparin or heparan sulfate ( Fig. 1A and Suppl. The SARS-CoV-2 spike protein depends on cellular heparan sulfate for cell binding. Heparin inhibits cellular invasion by SARS-CoV-2: structural dependence of the interaction of the surface protein (spike) S1 receptor binding domain with heparin
cord-256572-sqz8yc7b	2020	The causal coronavirus (SARS-CoV-2) binds host cells via a trimeric Spike whose receptor binding domain (RBD) recognizes angiotensin-converting enzyme 2 (ACE2), initiating conformational changes that drive membrane fusion. We find that monoclonal antibody CR3022 binds the RBD tightly, neutralising SARS-CoV-2 and report the crystal structure at 2.4 Å of the Fab/RBD complex. Potent nanomolar affinity neutralising human monoclonal antibodies against the SARS-CoV RBD have been identified that attach at the ACE2 receptor binding site (including M396, CR3014 and 80R (Ter Meulen et al., 2006; Sui et al., 2004; Zhu et al., 2007) ). We determined the crystal structure of the SARS-CoV-2 RBD-CR3022 Fab complex (see Methods and Table S3 ) to investigate the relationship between the binding epitopes of ACE2 and CR3022. Full interpretation of the detailed interactions between CR3022 and the RBD was enabled by the second crystal form which diffracted to high resolution, 2.4 Å, and the structure of which was refined to give an R-work/R-free of 0.213/0.239 and good stereochemistry (Methods, Table S3, Figure S5 ).
cord-258902-h0wrs01h	2020	title: Enhanced Elicitation of Potent Neutralizing Antibodies by the SARS-CoV-2 Spike Receptor Binding Domain Fc Fusion Protein in Mice The cell-cell fusion assay results correlated well with the virus neutralization potency and could be used for high-throughput screening of large panels of anti-SARS-CoV-2 antibodies and vaccines without the requirement of live virus infection in BSL3 containment. Based on its highly homology to SARS-CoV, SARS-CoV-2 RBD is corroborated to contain immune dominant epitopes capable of eliciting antibodies that can neutralize viral infection and block viral entry by competing hACE2 Pseudovirus neutralization assay was then performed by incubation of SARS-CoV-2 pseudovirus with serially diluted mice serum for 1h at 37 °C, followed by addition of the mixture into pre-seeded 293T-ACE2 cells. On day 0 (pre-immunization), day 13 and day 27, mouse sera were collected and analyzed for RBD binding, pseudovirus and live virus neutralization, and cell-cell fusion inhibition.
cord-259185-qg4jwbes	2020	In this work, we report the synthesis of a cheap yet highly sensitive cobalt-functionalized TiO2 nanotubes (Co-TNTs)-based electrochemical biosensor and its efficacy for rapid detection of spike glycoprotein of SARS-CoV-2 by examining S-RBD protein as the reference material. Our manuscript reports the synthesis of a cheap yet highly sensitive cobalt-functionalized TiO2 nanotubes (Co-TNTs)-based electrochemical biosensor for rapid detection of spike glycoprotein of SARS-CoV-2. . https://doi.org/10.1101/2020.09.07.20190173 doi: medRxiv preprint asymptomatic individuals are needed, which is feasible only after the development of a simple, portable and rapid point-of-use sensor for the detection of SARS-CoV-2. In the current work, we have determined the potential of Co-functionalized TiO2 nanotubes (Co-TNTs) for the electrochemical detection of S-RBD protein of SARS-CoV-2. Our data showed that cobalt functionalized TNTs could selectively detect the S-RBD protein of SARS-CoV-2 using the amperometry electrochemical technique in ~ 30 secs.
cord-260334-xo8ruswo	2019	Murine antisera with neutralising activity for the coronavirus causative of Middle East respiratory syndrome (MERS) were induced by immunisation of Balb/c mice with the receptor binding domain (RBD) of the viral Spike protein. To test the neutralising capacity of these antisera in vivo, susceptibility to MERS-CoV was induced in naive recipient Balb/c mice by the administration of an adenovirus vector expressing the human DPP4 receptor (Ad5-hDPP4) for MERS-CoV, prior to the passive transfer of the RBD-specific murine antisera to the transduced mice. The data gained indicate that this dual-route vaccination with novel formulations of the RBD-Fc, induced systemic and mucosal anti-viral immunity with demonstrated in vitro and in vivo neutralisation capacity for clinical strains of MERS-CoV. We have used this transduced mouse model to test the capacity of the antiserum derived from the dual route immunisation to neutralise MERS-CoV in vivo, by passive transfer prior to challenge with the EMC2012 strain and we have demonstrated a significant reduction in viral load in lung tissue in transduced mice.
cord-260406-qvc2fb0c	2020	
cord-260412-yjr83ef6	2020	Our group is developing a two-pronged approach to advance recombinant protein-based vaccines to prevent COVID-19 caused by SARS-CoV-2 and other coronavirus infections. One vaccine is based on a yeast-derived (Pichia pastoris) recombinant protein comprised of the receptor-binding domain (RBD) of the SARS-CoV formulated on alum and referred to as the CoV RBD219-N1 Vaccine. In addition to their low cost and suitability for use in public immunization programs in lowand middle-income countries, we pursued RBD recombinant protein-based vaccines as a technology to maximize safety relative to other platforms, such as virus vectors that have previously been found to induce immune enhancement. Optimization of the Production Process and Characterization of the Yeast-Expressed SARS-CoV Recombinant Receptor-Binding Domain (RBD219-N1), a SARS Vaccine Candidate Potential for developing a SARS-CoV receptor-binding domain (RBD) recombinant protein as a heterologous human vaccine against coronavirus infectious disease (COVID)-19 Yeast-Expressed SARS-CoV Recombinant Receptor-Binding Domain (RBD219-N1) Formulated with Alum Induces Protective Immunity and Reduces Immune Enhancement
cord-261877-4y37676n	2020	Recent cryoelectron microscopy (cryo-EM) studies on the stabilized ectodomain of SARS-CoV-2 S protein revealed a closed state of S trimer with three RBD domains in "down" conformation (Walls et al., 2020) , as well as an open state with one RBD in the "up" conformation, corresponding to the receptor-accessible state (Walls et al., 2020; Wrapp et al., 2020) . To gain a thorough picture on how the receptor ACE2 binding induces conformational dynamics of the SARS-CoV-2 S trimer and triggers transition towards the postfusion state, we determine the cryo-EM structure of SARS-CoV-2 S trimer in complex with human ACE2 PD domain to 3.8 Å resolution (termed SARS-CoV-2 S-ACE2, Figs. Based on the data, we put forward a mechanism of ACE2 binding-induced conformational transitions of SARS-CoV-2 S trimer from the tightly closed ground prefusion state transforming towards the postfusion state (Fig. 6) . Cryo-electron microscopy structures of the SARS-CoV spike glycoprotein reveal a prerequisite conformational state for receptor binding
cord-262043-66qle52a	2020	Spike (S) glycoprotein is the structural protein of SARS-CoV-2 located on the envelope surface, involve in interaction with angiotensin converting enzyme 2 (ACE2), a cell surface receptor, followed by entry into the host cell. The protein-protein docking and molecular dynamic simulation showed that tACE2 has higher binding affinity for RBD and form more stabilized complex with RBD than the intact ACE2. We designed a truncated version (tACE2) of ACE2 receptor covering the binding residues and performed protein-protein docking and molecular dynamic simulations to analyze its binding affinity for RBD and complex stability. Based on the HADDOCK score and the docking RMSD value, the docked complexes of ACE2 and tACE2 with RBD were analyzed for binding affinity DG (kcal mol À1 ) and stability using protein binding energy prediction (PRODIGY) server (Xue et al., 2016) .
cord-262145-i29e3fge	2020	A subset of anti-spike (10 of 32) and over half of anti-nucleocapsid (19 of 35) antibodies cross-reacted with other betacoronaviruses tested and harboured extensive somatic mutations, indicative of an expansion of memory B cells upon SARS-CoV-2 infection. The MAbs with 161 strong anti-RBD binding have a relatively long heavy chain CDR3 length (50% 162 binding concentration <0.5 µg/ml versus >0.5 µg/ml, p=0.03, two-tailed Mann-163 Whitney test; Supplemental Figure 3 The 32 anti-spike glycoprotein MAbs were systematically examined by plaque 173 reduction neutralisation (PRNT) assay for neutralisation of wild type SARS-CoV-2 174 virus (see methods; summarised in Table 1 ). Potent neutralising antibodies to the RBD of SARS-CoV-2 spike glycoprotein were 188 identified and we thus analyse the blockade of the ACE2-RBD interaction by anti-189 RBD antibodies in two assays ( Figure 3 , Table 1 The structure of VHH72-Fc bound to RBD is known (17) and its footprint on the 198 RBD does not overlap that of ACE2, so inhibition is thought to occur by steric 199 hindrance.
cord-263042-qdmunb9l	2016	Passive transfer of equine immune antibodies significantly reduced virus titers and accelerated virus clearance from the lungs of MERS-CoV infected mice. Our data show that horses immunized with MERS-CoV VLPs can serve as a primary source of protective F(ab'')(2) for potential use in the prophylactic or therapeutic treatment of exposed or infected patients. Several research groups have developed and produced anti-MERS patientderived or humanized monoclonal neutralizing antibodies in vitro that were able to protect MERS-CoV infected mice (Corti et al., 2015; Li et al., 2015; Zhao et al., 2014) . Prophylactic or therapeutic treatment of MERS-CoV infected mice with either IgG or F(ab'') 2 significantly decreased the virus load in their lungs. In both prophylactic and therapeutic settings, passive transfer of equine immune antibodies resulted in a 2e4 log reduction of virus titers in the lungs of MERS-CoV infected mice, and accelerated virus clearance in the serum treated group (Fig. 5A, B) .
cord-263090-29n9tsk9	2020	In this study, a structural-topology based model Hamiltonian of C3 symmetric trimeric spike is developed to explore its complete conformational energy landscape using molecular dynamic simulations. B. Side and top views of the homo-trimeric structure of SARS-CoV-2 spike protein with one RBD of the S1 subunit head rotated in the up conformation. A number of Cryo-EM structures captured the ''up'' and ''down'' conformations of the RBD domain of spike proteins of other coronaviruses including SARS-CoV-2 where the S1 subunit undergoes a hinge-like conformational movement prerequisite for receptor binding (Fig. 2C) (7, 8, 10, 17) . Analysis of all the simulations yields the 2-D free energy landscape of the trimeric spike protein of SARS-CoV-2 ( Fig 3B) with its all possible conformations. This generates a homo-trimeric SARS-CoV-2 spike where this initial structure has important components in terms of intra and inter-chain contacts (interaction) leading to an ''S1-head-up'' and an ''S1-head-down'' conformation for each protomer.
cord-263167-es806qhz	2020	We showed that passive transfer of a nAb provides protection against disease in high-dose SARS-CoV-2 challenge in Syrian hamsters, as revealed by maintained weight and low lung viral titers in treated animals. Donor plasma were tested for binding to recombinant SARS-CoV-2 and SARS-CoV-1 S and receptor binding domain (RBD) proteins, for binding to cell surface expressed spikes and for neutralization in both live replicating virus and pseudovirus assays (Fig. 2, B to D, and fig. The bulk-transformed ligation products for both the heavy chain and light chain were transfected and tested for binding to RBD and S protein, and for neutralization in the SARS-CoV-2 pseudovirus assay using HeLa-ACE2 target cells ( fig. To investigate the relationship between in vitro neutralization and protection in vivo against SARS-CoV-2, we selected two mAbs for passive transfer/challenge experiments in a Syrian hamster animal model based on a summary of the nAb data (table S3 and fig.
cord-263481-w5ytp1q7	2020	MERS-CoV uses dipeptidyl peptidase-4 (DPP4) as entry receptor [11] whereas SARS-CoV and SARS-CoV-2 utilize ACE-2 (angiotensin converting enzyme-2) [12] , abundantly available in lung alveolar epithelial cells and enterocytes, suggesting S glycoprotein as a potential drug target to halt the entry of SARS-with remarkable properties like glutamine-rich 42 aa long exclusive molecular signature (DSQQTVGQQDGSEDNQTTTIQTIVEVQPQLEMELTPVVQTIE) in position 983-1024 of polyprotein 1ab (pp1ab) [16] , diversified receptor-binding domain (RBD), unique furin cleavage site (PRRAR↓SV) at S1/S2 boundary in S glycoprotein which could play roles in viral pathogenesis, diagnosis and treatment [17] . There is growing evidence that spike protein, a 1273 amino acid long glycoprotein having multiple domains, possibly plays a major role in SARS-CoV-2 pathogenesis. In this study, we have analyzed 320 genomic sequences of SARS-CoV-2 to identify mutations between the available genomes followed by the amino acid variations in the glycoprotein S to foresee their impact on the viral entry to host cell from structural biology viewpoint.
cord-265697-bbvlowyo	2020	
cord-267001-csgmc155	2020	Moreover, immunization with rASP-1 co-administered with the alum-adjuvanted RBD vaccine in separate sites resulted in an enhanced frequency of TfH and GC B cells within the draining lymph nodes, both of which were positively associated with the titers of the neutralizing antibody response related to anti-MERS-CoV protective immunity. When the total IgG response to the MERS-RBD antigen was studied using the MERS-CoV S1 protein as the target protein, we found that although the RBD-specific total IgG antibody titers were ~8 times higher in mice that were vaccinated by co-administrating rASP-1 and the alum-adjuvanted RBD vaccine in separate sites (G6-142,525 end point titer), they were not significantly different from those elicited by immunization with RBD + rASP-1 + alum administered in a single inoculum (G5-18,149 end point titer), or with the alum-adjuvanted RBD vaccine (G4-53,104 end point titer; Figure S1A ).
cord-268144-maa8c4a4	2007	The sequential determination of crystal structures of the SARS coronavirus spike receptor-binding domain (RBD) in complex with its cellular receptor or neutralizing antibody opened a door for the design and development of antiviral competitive inhibitors. As an envelope glycoprotein, the spike protein of severe acute respiratory syndrome coronavirus (SARS-CoV) plays a key role in the viral entry and neutralization (Bartlam et al., 2005; Denison, 2004; Lau and Peiris, 2005; Xu and Gao, 2004; Zhu, 2004) . Receptor-binding domain of SARS-CoV spike protein induces highly potent neutralizing antibodies: implication for developing subunit vaccine Receptor-binding domain of severe acute respiratory syndrome coronavirus spike protein contains multiple conformation-dependent epitopes that induce highly potent neutralizing antibodies Structure of severe acute respiratory syndrome coronavirus receptor-binding domain complexed with neutralizing antibody Potent neutralization of severe acute respiratory syndrome (SARS) coronavirus by a human mAb to S1 protein that blocks receptor association
cord-268894-amfv3z2y	2020	
cord-273891-7w334xgt	2018	The viral spike glycoprotein (S) utilizes angiotensin-converting enzyme 2 (ACE2) as a host protein receptor and mediates fusion of the viral and host membranes, making S essential to viral entry into host cells and host species tropism. Subsequent studies of the highly pathogenic human coronavirus S proteins of SARS-64 CoV 15,22 and MERS-CoV 17,22 showed that these viral S1 RBD do indeed sample an ''up'' 65 conformation where the receptor-binding site is accessible. 70 To examine the hypothesized conformational transitions induced by proteolysis and 71 receptor binding, we used single-particle cryo-EM to determine structures of S in uncleaved, 72 S1/S2 cleaved and ACE2-bound states. Three-dimensional classification of the S1 RBD 73 positions and corresponding atomic protein models revealed that neither ACE2-binding nor 74 trypsin cleavage at the S1/S2 boundary induced substantial conformational changes in the CoV may use a distinct mechanism of FP2 membrane insertion. Cryo-electron microscopy structures of the SARS-CoV spike glycoprotein 381 reveal a prerequisite conformational state for receptor binding
cord-273893-3nd6ptrg	2013	Here we delineate the molecular basis of this specific interaction by presenting the first crystal structures of both the free receptor binding domain (RBD) of the MERS-CoV spike protein and its complex with CD26. Here we delineate the molecular basis of this specific interaction by presenting the first crystal structures of both the free receptor binding domain (RBD) of the MERS-CoV spike protein and its complex with CD26. Sequence alignment indicates, among betacoronaviruses, a possible structural conservation for the region homologous to the MERS-CoV RBD core, but a high variation in the external receptor binding motif region for virus-specific pathogenesis such as receptor recognition. Sequence alignment indicates, among betacoronaviruses, a possible structural conservation for the region homologous to the MERS-CoV RBD core, but a high variation in the external receptor binding motif region for virus-specific pathogenesis such as receptor recognition.
cord-274280-x5s4l0pp	2020	
cord-274480-aywdmj6o	2014	Middle East respiratory syndrome coronavirus (MERS-CoV) infects host cells through binding the receptor binding domain (RBD) on its spike glycoprotein to human receptor dipeptidyl peptidase 4 (hDPP4). Previously, we have generated a panel of MERS-CoV mutant RBD proteins at the residues D539, Y499, D510, E513, L506, W553 and V555 to characterize their impacts on binding activity to hDPP4 and the entry efficiency into target cells. To study the impacts of the substitutions of the critical residues on hDPP4 described above on the interaction between MERS-CoV RBD and hDDP4, we determined the binding efficiency between these two proteins by employing SPR technique. To further study the importance of the critical residues on hDPP4 on viral entry, we measured the entry efficiency of pseudovirus into COS7 cells expressing the wide-type and mutant forms of hDPP4. These results are consistent with our findings and suggest these residues play an important role in RBD binding and viral entry, and determining the tropism to MERS-CoV infection.
cord-275185-9br8lwma	2020	Following CP transfusion, six out of eight patients showed improved oxygen support status; chest CT indicated varying degrees of absorption of pulmonary lesions in six patients within 8 days; the viral load was decreased to a negative level in five patients who had the previous viremia; other laboratory parameters also tended to improve, including increased lymphocyte counts, decreased C-reactive protein, procalcitonin, and indicators for liver function. Herein, we performed a retrospective observational study involving eight critical or severe patients with COVID-19 from four designated hospitals in the southwest region of China, aiming to explore the potential efficacy and safety of CP therapy, and to provide more evidence for the quality control of donated plasma and reasonable clinical application of CP transfusion. 23 Assessing the effects of neutralizing activity of CP on the patients'' clinical efficacy, we found that patients treated by CP with high NAT50 (>1:640) had more obvious improvement than patients receiving low NAT50 value (≤1:640) of CP, including shorter negative conservation time of viral RNA, and higher increment of IgG level after CP transfusion.
cord-276493-hoaxv5e0	2020	With increasing structural data of key proteins in both SARS-CoV-2 and the host, such as the spike glycoprotein (S), the main protease (M pro ), RNA-dependent RNA polymerase (RdRp), and human angiotensin-converting enzyme 2 (hACE2), the structure-based design of new drugs has emerged as the most promising antiviral strategy. Several structure-based drug discovery studies have investigated the interaction of inhibitors in the substrate-binding pockets of SARS-CoV-2 M pro ( Figure 3C ) (Dai et al., 2020; Jin et al., 2020; Zhang et al., 2020b) . Because most inhibitors occupy the substrate binding pocket of SARS-CoV-2 FIGURE 4 | CryoEM structure of RdRp in complex with cofactors (nsp7 and nsp8), RNA template, and remdesivir. In addition, we provided structural insights into the mechanism of action of well-characterized drugs targeting the interaction between hACE2 and the spike protein of SARS-CoV-2 for viral entry, as well as M pro and RdRp for viral replication.
cord-276833-haci44cy	2019	We analyzed the mechanisms by which HBD 2 primes innate antiviral immunity and polarized activation of macrophage-like THP-1 cells using the receptor-binding domain (RBD) of Middle East respiratory syndrome coronavirus (MERS-CoV) spike protein (S RBD) as a model antigen. We previously reported that HBD 2 promotes an antiviral innate immune response in macrophage-like THP-1 cells and elicits an enhanced Ag-specific and virus-neutralizing antibody (Ab) response in vivo using the receptor binding domain (RBD) of MERS-CoV spike protein (S RBD) as a model Ag (Kim et al., 2018) . In this study, we investigated the mechanism by which HBD 2 enhances the type I IFN immune response in THP-1 cells by modulating Nod2 signaling pathways using HBD 2-conjugated S RBD of MERS-CoV. HBD 2-conjugated Ag stimulates the Nod2 signaling procedure, which leads to type I IFN production in macrophage-like THP-1 cells MERS-CoV infection inhibits the production of IFN-α/β and the host antiviral immune response .
cord-278869-7zr1118b	2020	To better understand antibody response induced by spike protein-based vaccines, we immunized rabbits with various SARS-CoV-2 spike protein antigens: S-ectodomain (S1+S2) (aa 16-1213), which lacks the cytoplasmic and transmembrane domains (CT-TM), the S1 domain (aa 16-685), the receptor-binding domain (RBD) (aa 319-541), and the S2 domain (aa 686-1213 as control). The spike ectodomain (S1+S2) generated antibodies that predominantly bound to S1+S2 108 6 (black bar), followed by the S1 protein (blue bar), and 3-fold lower antibody binding to the RBD 109 and the S2 domain (red and green bars, respectively) (Fig. 1D ). Antibody off-rate constants, which describe the fraction of antigen-antibody complexes 119 that decay per second, were determined directly from the serum sample interaction with SARS-120 CoV-2 spike ectodomain (S1+S2), S1, S2, and RBD using SPR in the dissociation phase only for 121 sensorgrams with Max RU in the range of 20-100 RU (Suppl.
cord-280939-d478p8u6	2020	Here, we present a safe and efficient protein-based assay for the detection of serum and plasma antibodies that block the interaction of the SARS-CoV-2 spike protein receptor binding domain (RBD) with its receptor, angiotensin-converting enzyme 2 (ACE2). Here, we present a safe and efficient protein-based assay for the detection of serum and plasma antibodies that block the interaction of the SARS-CoV-2 spike protein receptor binding domain (RBD) with its receptor, angiotensin-converting enzyme 2 (ACE2). SARS-CoV-2 ELISAs are performed by immobilizing a recombinantly produced viral antigen (such as the spike trimer or RBD) ( Figure 1B and Supplemental Figures 1 and 2; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.142362DS1) (see Methods) onto multiwell plastic plates that are then incubated with diluted patient serum or plasma samples.
cord-280941-ds6x0yym	2018	The receptor-binding domain (RBD) of Middle East respiratory syndrome-coronavirus (MERS-CoV) was fused with the RNA-interaction domain (RID) and bacterioferritin, and expressed in Escherichia coli in a soluble form. The concentration of the ion Fe(2+), salt, and fusion linker also contributed to the assembly in vitro, and the stability of the NPs. The kinetic "pace-keeping" role of chaperna in the super molecular assembly of antigen monomers holds promise for the development and delivery of NPs and virus-like particles as recombinant vaccines and for serological detection of viral infections. Taken together, the results confirmed the immunologically relevant conformation of the MERS-CoV RBD displayed on the hybrid ferritin particles, and the crucial role of RNA in controlling the kinetic pathway for the assembly of viral antigen monomers into stable NPs. To evaluate the immunogenicity of ferritin-based NPs, BALB/c mice (n = 5) were immunized with RBD, RBD-FR, and RBD-[SSG]-FR NPs antigens.
cord-281005-6gi18vka	2020	title: Mutations in SARS-CoV-2 Leading to Antigenic Variations in Spike Protein: A Challenge in Vaccine Development Therefore, we aimed to predict the mutations in the spike protein (S) of the SARS-CoV-2 genomes available worldwide and analyze its impact on the antigenicity. A total of 1,604 spike proteins were extracted from 1,325 complete genome and 279 partial spike coding sequences of SARS-CoV-2 available in NCBI till May 1, 2020 and subjected to multiple sequence alignment to find the mutations corresponding to the reported single nucleotide polymorphisms (SNPs) in the genomic study. In this study, we aimed to predict the mutations in the spike protein (S) of SARS-CoV-2 genomes available in the database (whole genome sequences as well as partial coding sequences of spike protein) and analyze the effect of each mutation on the antigenicity of the predicted epitopes.
cord-281536-8y7yxcp4	2020	
cord-281793-tj4m01s4	2020	Crossreactive antibodies (e.g., 47D11, S309, and VHH-72) that bind highly conserved epitopes on the RBDs of SARS-CoV and SARS-CoV-2 could have broad neutralization activities against viral infection. The receptor binding domain (RBD) of the SARS-CoV-2 S protein contains several novel residues that might be introduced through recombination with the pangolin coronavirus, indicating a possible critical step in the evolution of the ability of SARS-CoV-2 to infect humans [10] . isolated a human monoclonal antibody (named "rRBD-15") that inhibits the interaction of the RBD of SARS-CoV-2 and the ACE2 and neutralizes the pseudovirus infection [5] . The structure complex of 47D11 and the RBD (or the S1/S protein) would reveal a novel conserved site on the RBD for broad-neutralizing antibodies against SARSr-CoVs. In addition to 47D11, another human antibody (S309) isolated from memory B cells of a SARS survivor infected in 2003 neutralizes SARS-CoV-2 [18] .
cord-284102-rovyvv45	2020	Here we identified 11 unique nanobodies (Nbs) with high binding affinities to the SARS-CoV-2 spike receptor domain (RBD). Considering that Nbs targeting diverse epitopes within the RBD:ACE2 interface are beneficial 201 in both reducing viral infectivity and preventing mutational escape, we next combined the most 202 potent inhibitory and neutralizing candidates derived from Nb-Set1 (NM1226, NM1228) and 203 We incubated our previously generated color-coded beads 232 comprising RBD, S1 domain or homotrimeric spike with serum samples from patients or non-233 infected individuals, in addition to dilution series of the combinations NM1226/ NM1230 or 234 NM1228/ NM1230 and used this to detect patient-derived IgGs bound to the respective 235 antigens. As a result, we modified our previously described multiplex immunoassay 303 (MULTICOV-AB, 20 ) and developed a novel diagnostic test called NeutrobodyPlex to monitor 304 the presence and the emergence of neutralizing antibodies in serum samples of SARS-CoV-2 305 infected individuals. Neutralizing nanobodies bind SARS-CoV-2 spike RBD and block 681 interaction with ACE2
cord-285039-9piio754	2019	Three-dimensional structures of the receptor-binding domain (RBD) of MERS-CoV spike glycoprotein bound to cellular receptor and monoclonal antibodies (mAbs) have been determined by X-ray crystallography, providing structural information about receptor recognition and neutralizing mechanisms of mAbs at the atomic level. The first three-dimensional structure of the MERS-CoV spike glycoprotein receptor-binding domain (RBD), providing the molecular basis of viral attachment to host cells, was determined in the complex with it cellular receptor dipeptidyl peptidase 4 (DPP4, also called CD26) by X-ray crystallography [1] . After obtaining the phases of these diffracted X-rays by heavy-atom derivative, anomalous scattering or molecular replacement methods, a protein crystallographer then calculates the density of electrons with the protein crystal and builds a structural model based on the density map. MER-CoV RBD can be expressed using the Bac-to-Bac baculovirus expression system (Fig. 1 ), collected and captured using NTA Sepharose (GE Healthcare) and then further purified by gel filtration chromatography using a Superdex 200 High Performance column (GE Healthcare).
cord-285758-c18arb6s	2005	The spike (S) protein of SARS-CoV is the major inducer of neutralizing antibodies, and the receptor-binding domain (RBD) in the S1 subunit of S protein contains multiple conformational neutralizing epitopes. (30) reported that mucosal immunization of African green monkeys with an attenuated parainfluenza virus expressing S protein resulted in production of neutralizing antibodies and protected animals from infection by challenge with SARS-CoV. These findings suggest that RBD contains the major neutralizing epitopes in the S protein and is an ideal SARS vaccine candidate because RBD contains the receptor-binding site, which is critical for virus attachment to the target cell for infection (15, (17) (18) (19) . Epitope mapping and biological function analysis of antibodies produced by immunization of mice with an inactivated Chinese isolate of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) 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 Receptor-binding domain of SARS-CoV spike protein induces highly potent neutralizing antibodies: implication for developing subunit vaccine
cord-285900-3rr0j5tk	2016	
cord-287205-k64svq6n	2020	
cord-288761-fyvr0tc1	2017	These structures identified three distinct APN conformations, based on active site accessibility, which we termed closed, intermediate and open forms (Fig. 1a) . The phenylalanine was located in the loop that connects α 26 and α 27 in the single domain IV ARM repeat of human and pig APN (Fig. 2a) ; it penetrated the active site groove in the closed conformation and locked the peptide, ready for hydrolysis. CoV binding to APN would lock the protein in its open conformation (Fig. 2b) , preventing the ectodomain movement probably necessary for peptide hydrolysis (Fig. 2a) . In flow cytometry, we determined the binding of an RBD-Fc fusion protein to cells that expressed pAPN or an active site mutant (pAPN-HH/AA), alone or with various drugs (Fig. 4a,b) . Disulfide bonds that lock the APN closed conformation or drugs that prevent opening of the ectodomain inhibited CoV protein binding and cell infection, whereas porcine CoV S proteins probably hinder APN transition to the closed form and peptide hydrolysis.
cord-290290-wyx9ib7s	2020	
cord-291420-40xsypzt	2020	title: Mutational landscape and in silico structure models of SARS-CoV-2 Spike Receptor Binding Domain reveal key molecular determinants for virus-host interaction Formation of a stable binding interface between the Spike (S) protein Receptor Binding Domain (RBD) of SARS-CoV-2 and Angiotensin-Converting Enzyme 2 (ACE2) of host actuates viral entry. In silico structure modelling of interfaces induced by mutations on residues which directly engage ACE2 or lie in the near vicinity revealed molecular rearrangements and binding energies unique to each RBD mutant. The structural analysis of the mutated spike glycoprotein of SARS-CoV-2 RBD domain was done to assess the impact of interface amino acid residue mutations on binding affinity towards the human ACE2 (hACE2) receptor. Comparative analysis of structures showed key differences in all three binding clusters of SARS-CoV-2 RBD wild type and mutant interfaces with human or mouse ACE2 (Figure 2C, 2D and Table S1 ).
cord-291790-z5rwznmv	2020	
cord-292578-co5essuw	2020	
cord-292883-7hvq9qaj	2020	
cord-295482-qffg6r91	2017	Here we report the X-ray crystal structure of the receptor-binding domain (RBD) of the human coronavirus, HCoV-229E, in complex with the ectodomain of its receptor, aminopeptidase N (APN). Phylogenetic analysis shows that the natural HCoV-229E receptor-binding loop variation observed defines six RBD classes whose viruses have successively replaced each other in the human population over the past 50 years. The structure shows that receptor binding is mediated solely by three extended loops, a feature shared by HCoV-NL63 and the closely related porcine respiratory coronavirus, PRCoV. The six RBDs differ in their receptor-binding affinity and their ability to be bound by a neutralizing antibody (9.8E12) and taken together, our findings suggest that the HCoV-229E sequence variation observed arose through adaptation and selection. HCoV-229E infection in humans does not provide protection against different isolates 37 , and viruses that contain a new RBD class that cannot be bound by the existing repertoire of loop-binding neutralizing antibodies provide an explanation for this observation.
cord-296187-nnv2e7gr	2020	
cord-296319-fwn97wds	2020	
cord-296657-mymndjvd	2020	The extracellular domain of modified ACE2 fused to the Fc region of the human immunoglobulin IgG1 had stable structure and neutralized SARS-CoV-2 pseudotyped lentivirus and authentic virus with more than 100-fold lower concentration than wild-type. Engineering ACE2 decoy receptors with directed evolution is a promising approach to develop a SARS-CoV-2 neutralizing drug that has affinity comparable to monoclonal antibodies yet displaying resistance to escape mutations of virus. Three cycles of screening resulted in an identification of mutant ACE2 clones with more than 100-fold higher binding affinity to the RBD and lower half-maximal inhibitory concentration (IC50) for SARS-CoV-2 pseudotyped lentivirus as well as authentic virus. We engineered ACE2 to bind the RBD of the SARS-CoV-2 spike protein with the combination of surface display of mutagenized library and fluorescence-activated cell sorting (FACS) to perform the evolution in 293T human cells.
cord-297072-f5lmstyn	2012	title: A hexapeptide of the receptor-binding domain of SARS corona virus spike protein blocks viral entry into host cells via the human receptor ACE2 Peptide (438)YKYRYL(443) is part of the receptor-binding domain (RBD) of the spike protein of SARS-CoV. The interaction of SARS-CoV with its receptor ACE2 is an attractive drug target as epitopes of the RBD on the spike protein may serve as leads for the design of effective entry inhibitors (Du et al., 2009) . This method allows the determination of the binding specificity, as Table 2 Synthetic peptide library of fourteen 6mer peptides comprising RBD-residues N435-E452 and A471-S500 of SARS-CoV spike protein. We found a hexapeptide in the receptor-binding domain (RBD) of the S protein of SARS-CoV that carries a significant portion of the binding affinity of the virus to the human cell. Inhibition of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) infectivity by peptides analogous to the viral spike protein
cord-297747-kifqgskc	2020	Using homology modeling and molecular dynamics (MD) simulation methods, we report here the detailed structure of the ACE2 in complex with the receptor binding domain (RBD) of the SARS-CoV-2 spike protein. The simulation data further revealed critical residues at the complex interface and provided more details about the interactions between the SARS-CoV-2 RBD and human ACE2. When this study was started, neither the crystal structure of the SARS-CoV-2 spike protein nor the RBD segment were determined, so the homology modeling approach was applied to construct the model of the SARS-CoV-2 spike RBD in complex with the human ACE2 binding domain (denoted as CoV2-RBD/ACE2 in the following). Although the crystal structure and the predicted model of the CoV2-RBD/ACE2 complex provide important information about the binding interactions at the molecular interfaces, MD simulations can extend the knowledge to a dynamics regime in a fully solvated environment.
cord-299783-8ti6r0eh	2020	
cord-300707-k9uk14b3	2020	
cord-300784-4jeaqqn9	2020	
cord-300847-ycuiso0g	2020	We identified panels of fully human monoclonal antibodies (mAbs) from eight large phage-displayed Fab, scFv and VH libraries by panning against the receptor binding domain (RBD) of the SARS-CoV-2 spike (S) glycoprotein. By using phage display we have previously identified a number of potent fully human mAbs (m396, m336, m102.4) against emerging viruses including severe acute respiratory syndrome coronavirus (SARS-CoV) (4) , Middle East respiratory syndrome coronavirus (MERS-CoV) (5) and henipaviruses (6, 7) , respectively, which are also highly effective in animal models of infection (8) (9) (10) (11) ; one of them was administered on a compassionate basis to humans exposed to henipaviruses and successfully evaluated in a clinical trial (12) . Thus, to generate high affinity and safe mAbs we used eight very large (size ~ 10 11 clones each) naive human antibody libraries in Fab, scFv or VH format using PBMCs from 490 individuals total obtained before the SARS-CoV-2 outbreak.
cord-301347-22lt6h40	2016	Phylogenetic analysis of the complete genome sequence data revealed high rates of recombination, resulting in differing evolutionary patterns in phylogenies inferred for the spike region versus whole genomes. Despite excising a large portion of the genome prior to analysis, the Bayesian trees illustrate two distinct entries of PEDV into the US and characterize the evolution of PEDV compared to other CoVs. Modeling of the pAPN RBD region has revealed that Asian strains have increasing diversity compared to previously developed vaccines, and the variability in both the American and Asian strains needs to be considered for future vaccine development. Phylogenetic analysis of porcine epidemic diarrhea virus (PEDV) field strains in central China based on the ORF3 gene and the main neutralization epitopes Complete genome sequence of porcine epidemic diarrhea virus strain USA/Colorado/2013 from the United States Cell culture isolation and sequence analysis of genetically diverse US porcine epidemic diarrhea virus strains including a novel strain with a large deletion in the spike gene
cord-303868-aes92l6s	2020	
cord-305742-wf6qxplf	2020	
cord-306438-db2rqz4d	2020	
cord-308310-wtmjt3hf	2020	Higly repetitive display of RBD on immunologically optimized virus-like particles derived from cucumber mosaic virus resulted in a vaccine candidate (RBD-CuMVTT) that induced high levels of specific antibodies in mice which were able to block binding of spike protein to ACE2 and potently neutralized the SARS-CoV-2 virus in vitro. Higly repetitive display of RBD on immunologically optimized virus-like particles derived from cucumber mosaic virus resulted in a vaccine candidate (RBD-CuMVTT) that induced high levels of specific antibodies in mice which were able to block binding of spike protein to ACE2 and potently neutralized the SARS-CoV-2 virus in vitro. The receptor binding domain (RBD) of the SARS spike protein binds to ACE2 and is an important target for neutralizing antibodies [5] [6] [7] . Hence, the RBD-CuMVTT vaccine candidate is able to induce high levels of SARS-CoV-2 neutralizing antibodies. Receptor-binding domain of SARS-CoV spike protein induces highly potent neutralizing antibodies: implication for developing subunit vaccine
cord-308428-zw26usmh	2020	Here, we report the generation of synthetic nanobodies, known as sybodies, against the receptor-binding domain (RBD) of SARS-CoV-2 spike protein. We identified a sybody pair (Sb#15 and Sb#68) that can bind simultaneously to the RBD, and block ACE2 binding, thereby neutralizing pseudotyped and live SARS-CoV-2 viruses. However, binders of the isolated RBD may not effectively engage the aforementioned pre-fusion conformation of the spike protein, which could account for the poor neutralization ability of recently described single-domain antibodies that were raised against the RBD of SARS-CoV-2 spike protein [29] . Since Sb#15 and Sb#68 can bind simultaneously to the RBD and the full-length spike protein, we mixed Sb#15 and Sb#68 together to investigate potential additive or synergistic neutralizing activity of these two independent sybodies. To gain structural insights into how Sb#15 and Sb#68 recognize the RBD, we performed single particle cryo-EM analysis of the spike protein in complex with the sybodies. Neutralizing nanobodies bind SARS-CoV-2 spike RBD and block interaction with ACE2
cord-309182-t9ywnshj	2020	
cord-309411-2dfiwo65	2020	
cord-309898-sju15hev	2020	
cord-310230-9wfb43gt	2020	Our goal is to provide a detailed structural mechanism of how nCOV-2019 recognizes and establishes contacts with ACE2 and its difference with an earlier coronavirus SARS-COV in 2002 via extensive molecular dynamics (MD) simulations. 7 Based on the sequence similarity between RBD of nCOV-2019 and SARS-COV and also the tight binding between RBD of nCOV-2019 and ACE2, it is most probable that nCOV-2019 uses this receptor on human cells to gain entry into the body. The focus of this article is to elucidate the differences between the interface of SARS-COV and nCOV-2019 with ACE2 to understand with atomic resolution the interaction mechanism and hotspot residues at the RBD/ACE2 interface using long-timescale molecular dynamics (MD) simulation. The binding energetics between ACE2 and the RBD of SARS-COV, nCOV-2019 and all its mutant complexes were investigated by the MMPBSA method. Computational Simulations Reveal the Binding Dynamics between Human ACE2 and the Receptor Binding Domain of SARS-CoV-2 Spike Protein
cord-310636-y7n22ykt	2020	
cord-311035-s3tkbh9r	2020	A deep mutational scan of ACE2 expressed on human cells identified mutations that increase S affinity and guided the engineering of a potent and broad soluble receptor decoy. • The experimental mutational landscape of ACE2 for binding the RBD of SARS-CoV-2 provides a blueprint for engineering high affinity decoy receptors. Following FACS selection of the human culture to enrich a cell population with high binding activity for SARS-CoV-2 protein S, RNA transcripts were isolated and Illumina sequenced. The deep mutational scan of ACE2 revealed that mutations can indeed be found to enhance binding toward SARS-CoV-2 RBD (Figure 2) , suitable for engineering high affinity soluble decoy receptors [15] . A soluble ACE2 variant that combines three mutations, called sACE2 2 .v2.4, was found to be highly expressed, is a stable monodisperse dimer, binds SARS-CoV-2 S with picomolar affinity and potently neutralizes infection of a susceptible cell line by authentic virus.
cord-312560-onfabcfv	2020	The data demonstrate high prevalence of spike-and RBD-specific IgM and IgA, similar to that of IgG1, in plasma/serum from COVID-19 patients and their significant contributions to virusneutralizing activities. In Fig. 3 , comparing levels of total Ig with the different Ig isotypes showed a highly significant correlation with IgG1 for both Abs specific for spike and RBD indicating that IgG1 is the major isotype induced by SARS-CoV-2 infection. To ask directly to what extent Abs of different isotypes mediate neutralization, we evaluated the neutralization activities of IgM, IgG, and IgA fractions purified from plasma from five COVID-19-convalescent individuals (RP#1-5). Several SARS-CoV-2 vaccine candidates tested in animal models and humans were shown to induce IgG responses against spike and RBD as well as virus neutralizing activities, but in many of these studies, the induction of other Ig isotypes was not evaluated 46-49 .
cord-314574-3e6u4aza	2020	Considering the relatively high identity of receptor-binding domain (RBD) in 2019-nCoV and SARS-CoV, it is urgent to assess the cross-reactivity of anti-SARS CoV antibodies with 2019-nCoV spike protein, which could have important implications for rapid development of vaccines and therapeutic antibodies against 2019-nCoV. Interestingly, some of the most potent SARS-CoV-specific neutralizing antibodies (e.g. m396, CR3014) that target the ACE2 binding site of SARS-CoV failed to bind 2019-nCoV spike protein, implying that the difference in the RBD of SARS-CoV and 2019-nCoV has a critical impact for the cross-reactivity of neutralizing antibodies, and that it is still necessary to develop novel monoclonal antibodies that could bind specifically to 2019-nCoV RBD. Next, we expressed and purified several representative SARS-CoV-specific antibodies which have been reported to target RBD and possess potent neutralizing activities, including m396 [3] , CR3014 [4] , CR3022 [5] , as well as a MERS-CoV-specific human monoclonal antibody m336 developed by our laboratory [15] , and measured their binding ability to 2019-nCoV RBD by ELISA (Figure 1(e)) .
cord-314676-ndke9agh	2020	
cord-315415-3aotsb2g	2020	
cord-315437-h6xjudm0	2018	
cord-318018-ybdkp398	2020	Sera from healthcare workers affected by non-severe COVID-19 were longitudinally collected over four weeks, and compared to sera from patients hospitalized in Intensive Care Units (ICU) and SARS-CoV-2-negative subjects for the presence of IgM, IgG and IgA antibodies as well as soluble pro-inflammatory mediators in the sera. Our data show that humoral immune responses against SARS-CoV-2 correlated with disease severity in terms of both antibody titers, persistence over time and serum levels of pro-inflammatory cytokines. Here we show that humoral immune responses against SARS-CoV-2 correlated with disease severity in terms of both antibody titers, persistence over time and serum levels of pro-inflammatory mediators. Moreover, we showed that the vast majority of COVID-19 mildly symptomatic patients analyzed in the study halved their anti-RBD antibody titers after 4 weeks from viral negativization, thus confirming the short lifespan of humoral immune responses against SARS-CoV-2.
cord-318444-sgm24q1i	2020	
cord-319571-fspmgg4s	2020	
cord-319590-f9qcabcx	2020	
cord-319855-78xmxymu	2020	
cord-320238-qbjrlog1	2020	
cord-321166-nvphu1fm	2020	
cord-321854-cy8vyb6j	2020	
cord-321918-9jwma2y6	2020	The spike protein can be divided into two domains; S1 is responsible for angiotensin-converting enzyme II(ACE2) recognition, the recently identified host cell receptor, and S2 mediates membrane fusion (Figure 2 ). 98 99 On the basis of this approach, they identified two small molecules, TGG (12, Table 4 ) and luteolin (13) , that can bind avidly to the SARS-CoV S2 protein and inhibit viral entry of SARS-CoV into Vero E6 cells with IC 50 values of 4.5 and 10.6 μM, respectively. 113 A high-throughput screen (HTS) of a 1000-compound library that resulted in the identification of MDL28170 (17 , Table 4 ) by Bates et al., and in an antiviral activity assay, 17 specifically inhibited cathepsin L-mediated substrate cleavage and blocked SARS-CoV viral entry, with an IC 50 value of 2.5 nM and EC 50 value in the range of 100 nM.
cord-323324-h2a25xym	2020	
cord-323514-jaom3p6s	2006	Abstract The spike (S) protein of severe acute respiratory syndrome coronavirus (SARS-CoV) has two major functions: interacting with the receptor to mediate virus entry and inducing protective immunity. Coincidently, the receptor-binding domain (RBD, residues 318–510) of SAR-CoV S protein is a major antigenic site to induce neutralizing antibodies. We also demonstrated that the RBD-Fc bearing R441A mutation could not bind to soluble and cell-associated angiotensin-converting enzyme 2 (ACE2), the functional receptor for SARS-CoV and failed to block S protein-mediated pseudovirus entry, indicating that this point mutation also disrupted the receptor-binding motif (RBM) in the RBD. In this study, we used the RBD-Fc as a model to study how a single residue mutation in the RBD can abolish the major function of full-length S protein, since this molecule can efficiently bind to the receptor ACE2 and contains multiple conformation-dependent epitopes (Conf I-VI) capable of inducing highly potent neutralizing antibodies [29] .
cord-323967-2mo915u1	2020	
cord-326282-uxn64olw	2020	
cord-326337-s0fp5z1q	2020	Deep mutagenesis of the isolated receptor-binding domain (RBD) by yeast surface display 44 has easily identified mutations in S that retain high expression and ACE2 affinity, yet are no longer bound 45 by monoclonal antibodies and confer resistance (19) . An alternative protein-based antiviral to monoclonal antibodies is to use soluble ACE2 (sACE2) as a 56 decoy to compete for receptor-binding sites on the viral spike (6, (22) (23) (24) (25) of diverse SARS-associated betacoronaviruses that use ACE2 for entry. The sequence 162 diversity observed among natural betacoronaviruses, which display high diversity at the ACE2 binding 163 site, is therefore replicated in the deep mutational scan, which predicts the SARS-CoV-2 spike tolerates 164 substantial genetic diversity at the receptor-binding site for function. From this accessible sequence 165 diversity SARS-CoV-2 might feasibly mutate to acquire resistance to monoclonal antibodies or 166 engineered decoy receptors targeting the ACE2-binding site.
cord-327654-9g8zcxaa	2020	
cord-327711-welf0eb1	2020	Cryo-EM analyses of the pre-fusion Spike incubated with EY6A Fab reveal a complex of the intact trimer with three Fabs bound and two further multimeric forms comprising destabilized Spike attached to Fab. EY6A binds what is probably a major neutralising epitope, making it a candidate therapeutic for COVID-19. A neutralisation test for EY6A based on quantitative PCR detection of virus in the supernatant bathing infected Vero E6 cells after 5 days of culture, showed a ~1000-fold reduction in virus signal (Methods, Extended Data Fig. 3 ) indicating that it is highly neutralising. To elucidate the epitope of EY6A, we determined the crystal structures of the deglycosylated SARS-CoV-2 RBD in complex with EY6A Fab alone and in a ternary complex incorporating a nanobody (Nb) which has been shown to compete with ACE2 (for data on a closely related Nb see Huo 2020, submitted), as a crystallisation chaperone.
cord-328003-yovp8squ	2020	Here, we provide a comprehensive overview of the wealth of research related to the SARS-CoV-2 S glycoprotein biosynthesis, structure, function, and antigenicity, aiming to provide useful insights into the design and development of the S protein-based vaccines as well as therapeutics to prevent or treat the ongoing global spread of SARS-CoV-2/COVID-19. Prefusion structures of human coronavirus HKU1 (HCoV-HKU1) and mouse hepatitis virus S protein ectodomains without two consecutive proline mutations reveal only fully closed conformation (37, 42) , similar to that observed for a full-length, wild-type prefusion form of the SARS-CoV-2 S glycoprotein (41) . Therefore, SARS-CoV-2 evades immune surveillance also through conformational masking, which is well-documented for HIV-1 (43, 44) ; while at the same time, the S protein could transiently sample the functional state to engage ACE2, consistent with the notion that the fusion glycoprotein of highly pathogenic viruses have evolved to perform its functions while evading host neutralizing antibody responses.
cord-328189-jpkxjn6e	2020	We compare the interaction between the human ACE2 receptor and the SARS-CoV-2 spike protein with that of other pathogenic coronaviruses using molecular dynamics simulations. Herein, we analyze the binding of several CoV RBDs to ACE2 with molecular dynamics (MD) simulations and compare the stability, relative interaction strength, and dynamics of the interaction between the viral spike protein and the human ACE2 receptor. While the sequence identity between the RBDs of COVID-19 and SARS-2002 is 73% (Table 1) , we observe a significantly higher residue substitution rate at the interaction interface with the ACE2 receptor. Our MD simulation analysis reveals that the SARS-des has a substantially lower interaction scores with ACE2 (median of -2199.2, Fig. S2) , as expected for an optimized human ACE2-binding RBD design. We relied on the crystal structure of the spike protein receptor-binding domain from a SARS coronavirus designed human strain complexed with the human receptor ACE2 (PDB 3SCI, resolution 2.9Å) as a template for comparative modeling.
cord-328578-9qzo18v3	2020	When immunized in mice, the S1 domain induced much higher IgG and IgA antibody levels than the RBD and more efficiently neutralized SARS‐CoV‐2 when adjuvanted with alum. Article SARS-CoV-2 S1 induces higher IgG and IgA titers than RBD 2 weeks after the third intramuscular immunization (Figure 2A) , both S1-specific (S1-coated plate in Figure 2 ) and RBD-specific (RBD-coated plate in Figure 2 ) antibodies were analyzed. HEK293K cell-expressed recombinant S1 (S1 immunized) and E.coli-expressed norovirus shell domain-S1 fusion protein (S-S1 immunized) induced similar S1-specific IgG titers (64 000) and similar RBD-specific titers (8 000) ( Figure 2B ). HEK293K cell-expressed recombinant RBD (RBD immunized) and E.coli-expressed norovirus shell domain-RBD fusion proteins (S-RBD immunized) induced low levels of IgG1 and IgG2a titers specific to both S1 (S1 coated in Figure 3A&B ) and the RBD (RBD coated in Figure 3A&B ).
cord-329011-spiuqngp	2020	The spike (S) protein of SARS-CoV-2, which plays a key role in the receptor recognition and cell membrane fusion process, is composed of two subunits, S1 and S2. A large number of glycosylated S proteins cover the surface of SARS-CoV-2 and bind to the host cell receptor angiotensinconverting enzyme 2 (ACE2), mediating viral cell entry [8] . The SARS-CoV-2 S protein is highly conserved among all human coronaviruses (HCoVs) and is involved in receptor recognition, viral attachment, and entry into host cells. Structure of the S1 subunit The binding of virus particles to cell receptors on the surface of the host cell is the initiation of virus infection; therefore, receptor recognition is an important determinant of viral entry and a drug design target. Therefore, the development of antibodies targeting this functional motif may cross-bind and neutralize these two viruses and related CoVs. Antiviral peptides prevent SARS-CoV-2 membrane fusion and can potentially be used for the prevention and treatment of infection.
cord-329392-fufattj8	2020	
cord-331786-wgt7kg6f	2020	For this purpose, we tested our ability to produce, in the framework of an academic lab and in a matter of weeks, milligram amounts of six different recombinant monoclonal antibodies against SARS-CoV-2 in Nicotiana benthamiana. In parallel, we also produced the recombinant SARS-CoV-2 N protein and its Receptor Binding Domain (RBD) in planta and used them to test the binding specificity of the recombinant mAbs. Finally, for two of the antibodies we assayed a simple scale-up production protocol based on the extraction of apoplastic fluid. Finally, we performed sandwich ELISA tests of sybody17 and nanobody72 ( Fig 5E and Fig 5F, respectively) using the total and concentrated apoplastic fluid as detection reagent against serial dilutions of crude plant extracts from RBD-producing plants, showing that this simple antibody preparation can be directly employed in detection procedures without the need of additional purification steps.
cord-332134-88wfcc3y	2020	
cord-332185-a96r1k7a	2020	
cord-332855-u0amf1oh	2019	In silico docking experiments with the recently published cryo-EM structure of the M41 IBV spike protein and our glycosylation results revealed a potential ligand receptor site that is ringed by four glycosylation sites that dramatically impact ligand binding. However, the Beaudette strain is a cell culture-adapted strain, is nonvirulent in chickens (15) , and does not bind chicken tissues known to be important for infectivity (11) , making it difficult to extrapolate these results to clinically relevant IBVs. To characterize and assess the role that glycosylation plays when interacting with host tissues through the RBD of pathogenic IBV strain M41, we used a combination of molecular and analytical techniques, including histochemistry, ELISA, circular dichroism (CD), MS, and docking analyses as listed in Table 1 . Six of the 10 glycosylation sites in the RBD domain of IBV M41 were essential for binding to chicken trachea tissue and an ELISA-presented sialylated oligosaccharide ligand.
cord-332948-h297ukuu	2020	authors: Olotu, Fisayo A.; Omolabi, Kehinde F.; Soliman, Mahmoud E.S. title: Leaving no stone unturned: Allosteric targeting of SARS-CoV-2 Spike protein at putative druggable sites disrupts human angiotensin-converting enzyme interactions at the receptor binding domain. 30 Identification of other functional (allosteric) sites on the prefusion S protein could present another dynamic and effective approach of preventing SARS-CoV-2 infectivity relative to its interaction with the host cell ACE2 and proteases. 53 Relatively, this study was implemented to (i) identify potential druggable sites across the S1 and S2 domains of the SARS-CoV-2 S protein other than the RBD-hACE2 interface (ii) perform high-throughput (virtual) screening of ~1500 FDA approved drugs against the most druggable site(s) (iii) investigate the binding dynamics and interaction mechanisms of the compounds and their consequential effects on the S-protein RBD-ACE2 complex. We believe this systematic study will be able to provide structural and molecular insights into possible allosteric sites on SARS-CoV-2 S protein suitable for selective targeting and structureComputational methodologies
cord-333089-ufyzqgqk	2020	Based on the structural complementarity and steric impediments between the S protein and human ACE2 (hACE2) protein membranes, we mapped the glycosylation sites of both models [21] [22] [23] [24] and performed molecular dynamics simulations (MDS) by 250 ns to stabilize the glycosylated SARS-CoV2 spike (S) and hACE2 complex (suppl. Given the possibility that occupancy at glycosylated residues or S-RBD binding sites by estrogens could modify the affinity of the SARS-CoV2 virus and alter entry into the cell thereby reducing infectivity, we sought to further examine these interactions using a range of complementary experimental approaches (see Table S1 ). In an effort to explore the potential protective effects of female sex hormones against SARS-CoV-2 infection, we examined the impact of estradiol (17β-diol) and a dietary-derived phytoestrogen (S-equol) on hACE2 structure and protein expression by a combination of in silico modeling, in vitro, and in vivo analysis.
cord-333264-jdvb8px4	2020	Here, we report the isolation and characterization of an alpaca-derived single domain antibody fragment, Ty1, that specifically targets the receptor binding domain (RBD) of the SARS-CoV-2 spike, directly preventing ACE2 engagement. While fusion to an Fc domain renders Ty1 extremely potent, Ty1 neutralizes SARS-CoV-2 spike pseudovirus as a 12.8 kDa nanobody, which can be expressed in high quantities in bacteria, presenting opportunities for manufacturing at scale. The S ectodomain was purified from filtered supernatant on Streptactin XT resin (IBA Lifesciences), followed by size-exclusion chromatography on a Superdex 200 in 5 mM Tris pH 8, 200 mM NaCl. The RBD domain (RVQ-VNF) of SARS-CoV-2 was cloned upstream of an enterokinase cleavage site and a human IgG1 Fc. This plasmid was used to transiently transfect FreeStyle 293F cells using the FreeStyle MAX reagent. Neutralizing nanobodies bind SARS-CoV-2 spike RBD and block interaction with ACE2
cord-333465-cha7ndv5	2020	Patient mortality, sex, blood type, and age were all associated with differences in antibody production to SARS-CoV-2 antigens which may help explain variation in immunity between these populations. We evaluated anti-193 SARS-CoV-2 antibody production to 3 antigens (RBD, N, and S1) in 82 in-patients 194 Table 1 ) by developing a novel rapid-ELISA technique. Our survey of SARS-CoV-2 positive patients demonstrated that antibody (IgG) 198 production to RBD, N, and S1 proteins developed over the first 10 to 20 days post-199 symptom onset (Figure 1a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. To accurately assess 223 differences in antibody production independently of disease outcome, we quantified anti-224 SARS-CoV-2 IgG production in patients who survived infection grouped by biological sex, 225 . . https://doi.org/10.1101/2020.08.24.20180877 doi: medRxiv preprint significantly increased in patients that did not survive SARS-CoV-2 infection compared to 272 those that did (Figure 4d ).
cord-333703-1ku3jc9s	2020	Exposure of larvae to SARS-CoV-2 Spike (S) receptor binding domain (RBD) recombinant protein was sufficient to elevate larval heart rate and treatment with captopril, an ACE inhibitor, reverted this effect. In mice and humans, ace2 expression is detected in 121 sustentacular cells, olfactory stem cells known as horizontal and globose basal cells in the 122 olfactory epithelium, and vascular cells (pericytes) in the olfactory bulb (Brann et al., 2020 The present study reports for the first time that zebrafish larvae exposed to SARS-CoV-2 appear 134 to mount innate immune responses that resemble cytokine responses of mild COVID-19 patients. There are copious amounts of immune cells in the teleost olfactory organ ( Intranasal delivery of SARS-CoV-2 S RBD induces inflammatory responses and 318 widespread loss of olfactory receptor expression in adult zebrafish olfactory organ 319 320
cord-335118-oa9jfots	2020	By performing all-atom Molecular Dynamics (MD) simulations, we identified an extended network of salt bridges, hydrophobic and electrostatic interactions, and hydrogen bonding between the receptor-binding domain (RBD) of the S protein and ACE2. Initial studies have constructed a homology model of SARS-CoV-2 RBD in complex with ACE2, based on the SARS-CoV crystal structure (8, 14) and performed conventional MD (cMD) simulations totaling 10 ns (15, 16) and 100 ns (17, 18) in length to estimate binding free energies (15, 16) and interaction scores (18) . In this study, we performed a comprehensive set of all-atom MD simulations totaling 16.5 µs in length using the recently-solved structure of the RBD of the SARS-CoV-2 S protein in complex with the PD of ACE2 (7) . In 20 SMD simulations (each 15 ns, totaling 300 ns in length, table S1), the average work applied to unbind RBD from PD was 71.1 ± 12.7 kcal/mol (mean ± s.d.), demonstrating that the S protein binds stably to ACE2 (Fig. 3B) .
cord-335316-x2t5h5gu	2020	This was a prospective open label clinical study to assess the feasibility, safety and immunological impact of delivering anti-SARS-CoV-2 convalescent plasma to hospitalized patients aged 18 years or older with severe or life-threatening COVID-19 disease within 21 days from the onset of their illness. Univariate regression analysis for antibody titer (anti-RBD and anti-spike) was conducted against age, sex, body mass index (BMI), previous pregnancy, previous blood donation, blood type, symptoms (fever, cough, sore throat, dyspnea, abdominal pain, aguesia, anosmia, fatigue, myalgia, headache), co-morbidities (respiratory, cardiovascular, renal, diabetes, autoimmune disease, cancer, liver disease), smoking history, travel in the past 3 months to the United States, Asia or Europe, symptom duration, interval from symptoms resolution to plasma donation, and hospitalization. To determine predictors of anti-RBD and anti-spike antibody titer, we performed best subset multivariable analysis including age, sex, blood type, history of previous blood donation, fever, cough, fatigue, myalgia, symptom duration, hospitalization and travel in the United States within the past 3 months.
cord-336150-l8w7xk0b	2020	The essential surface glycoprotein of SARS-CoV-2 known as spike (S) protein, essential for host cell receptor binding, showed only 72% similarity with SARS-CoV at the nucleotide level. Comparative genome analysis of RaTG13, a virus from a Rhinolophusaffinis (i.e. horseshoe) bat sampled from Yunnan province in China in 2013, with SARS-CoV-2, showed that SARS-CoV-2 has 96% similarity at the nucleotide sequence level . Later, it was found that the disease was caused by a virus designated as a novel human coronavirus, MERS-CoV, phylogenetic data showed that it belonged to lineage C of the Betacoronavirusgenus and was highly similar to bat coronaviruses HKU4 (Tylonycterispachypus) and HKU5 (Pipistrelluspipistrellus; Lau et al. When cell lines over-expressed the transmembrane protein ''angiotensin-converting enzyme 2'' (ACE2) from humans, bats, pig or civet cats and were infected with SARS-CoV-2, results showed that they became hypersensitized to infection, thus indicating that ACE2 is a SARS-CoV-2 receptor . Recently, neutralizing monoclonal antibodies and nanobodies against the RBD domain of S protein showed protection against SARS-CoV and MERS-CoV (Du et al.
cord-338517-1mxcssjj	2020	The phage display method, allowing rapid and wide display of proteins directly correlated to their associated genes, can detect NAbs against SARS-CoV from both naïve and immune antibody libraries, capable of blocking the binding of S1 domain, thereby showing virus neutralization and prophylaxis capability either in vitro or in the animal models (31, 33, 36) . Another method, possibly allowing the production and utilization of existing NAbs, may include the use of Epstein-Barr virus (EBV) transformation of human B cells to improve the isolation of NAbs from the memory B cells harvested from the SARS-CoV infected patients (11) . Experimental and clinical data on the use of convalescent plasma products and humanized monoclonal antibodies for H5N1 influenza infection have also shown positive outcomes, and this treatment was proposed as a mean for overcoming anti-viral drug resistance (62, 79, 80) . In a study involving 20 patients with severe pandemic influenza A (H1N1) 2009 virus infection, administration of convalescent plasma reduced respiratory tract viral load, serum cytokine response, and mortality (81) .
cord-338538-uea9kwge	2019	Herein, we generated a bacterial outer membrane vesicles (OMVs)-based vaccine presenting the antigenic stable chimeric fusion protein of the H1-type haemagglutinin (HA) of the pandemic influenza A virus (H1N1) strain from 2009 (H1N1pdm09) and the receptor binding domain (RBD) of the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) (OMVs-H1/RBD). In addition, the OMVs-H1/RBD vaccinated mice showed a significant increase of neutralizing antibodies against the MERS-CoV strain HKU-NRCE-270 at week 2 and reached the highest neutralizing titer 160 (7.3 log2) at week eight compared to the control group (p < 0.001) (Figures 2c and 3a) . Based on these observations we engineered the expression of antigenically-stable and immunogenic (OMVs)-based bivalent vaccine that elicits protective antibodies (Abs) following immunization to control infections with H1N1pdm09 and MERS-CoV. In summary, the results show that the generated (OMVs-H1/RBD)-based vaccine presenting the antigenic stable chimeric fusion protein of H1-type HA of the pandemic influenza A virus (H1N1) strain and RBD of MERS-CoV induces specific neutralizing antibodies against H1N1pdm09 and MERS-CoV leading to protection of immunized mice against both viruses.
cord-339093-mwxkvwaz	2020	It potently neutralized mouse adapted SARS-CoV-2 in wild type mice at a dose as low as 2 mg/kg and exhibited high prophylactic and therapeutic efficacy in a hamster model of SARS-CoV-2 infection, possibly enhanced by its relatively small size. To identify potent neutralizing V H s against SARS-CoV-2, we panned our large (10 11 clones) and diverse phage-displayed human V H antibody library against recombinant RBD. One of those V H s, ab8, in an Fc (human IgG1, crystallizable fragment) fusion format, showed potent neutralization activity and specificity against SARS-CoV-2 both in vitro and in two animal models. They also suggest that the double mutations Q498T/P499Y on RBD did not influence V H -Fc ab8 binding and contribute to the validation of the mouse adapted SARS-CoV-2 model for evaluation of neutralizing antibody efficacy. In conclusion, we identified a fully human antibody V H domain that shows strong competition with ACE2 for binding to RBD and potent neutralization of SARS-CoV-2 in vitro and in two animal models.
cord-339724-roj8ksvc	2014	title: Tailoring Subunit Vaccine Immunity with Adjuvant Combinations and Delivery Routes Using the Middle East Respiratory Coronavirus (MERS-CoV) Receptor-Binding Domain as an Antigen Interestingly, robust RBD-specific antibody and T-cell responses were induced in mice immunized with the rRBD protein in combination with IFA and CpG ODN, but low level of neutralizing antibodies were elicited. In this study, different adjuvants combination regimens including alum, IFA, CpG and poly(I:C) were compared in an effort to promote balance between Th1 and Th2 immune response to bystander rRBD antigen spanning residues 367-606 of MERS-CoV S in a murine model to develop an effective vaccine against MERS-CoV infection. The results indicated that rRBD protein combined with any adjuvant, including alum, IFA, CpG or poly(I:C), could induce a RBD-specific IgG antibody response in the majority of mice after the second immunisation.
cord-340472-9ijlj4so	2005	Figure 3B -D shows three views of the crystal structure of human ACE2, in which residues that convert rat ACE2 to an efficient SARS-CoV receptor are shown in red, and additional residues whose alteration interferes with S1-Ig association are shown in yellow. (C) Murine leukemia viruses (MLV) expressing green fluorescent protein (GFP), lacking its endogenous envelope glycoprotein (MLV-GFP), and pseudotyped with the S protein of SARS-CoV (TOR2 isolate) were incubated with HEK293T cells transfected with plasmids encoding the indicated human or rat ACE2 variants. We have shown that entry is the primary barrier to SARS-CoV infection of murine Surface plasmon resonance experiments in which the indicated RBD-Ig TOR2 variants shown in Figure 6B bound to immobilized anti-human antibody were assayed for association with soluble human ACE2. S-protein alterations at residues 479 and 487 are important for high-affinity association with human ACE2, and for efficient infection of cells expressing this receptor.
cord-340960-abanr641	2020	In a mixed‐design evaluation study, we compared the diagnostic accuracy of serological immunoassays that are based on various SARS‐CoV‐2 proteins and assessed the neutralizing activity of antibodies in patient sera. A total of 54 randomly selected sera from individuals who were tested positive in either of the three ELISA immunoassays as well as 6 negative controls were assessed in a live SARS-CoV-2 neutralization assay (all collected in April 2020). Recombinantly expressed RBD has been used to establish an in-house ELISA for the detection of IgM and IgG anti-SARS-CoV-2 antibodies in human serum samples (supplementary Fig. 1a,b) . A total of 54 randomly selected sera from individuals who were tested positive in either of the three ELISA immunoassays as well as 6 negative controls were assessed in a live SARS-CoV-2 neutralization assay using ACE2-expressing Vero-E6 cells (34 inpatient samples, and 26 samples of medical personnel).
cord-341396-0tn06al2	2020	In this study, we collected blood from COVID-19 patients who have recently become 5 virus-free and therefore were discharged, and analyzed their SARS-CoV-2-specific antibody 6 and T cell responses. NP-and S-RBD-specific 9 IgM and IgG antibodies were both detected in the sera of newly discharged patients, 10 compared with healthy donor groups. Anti-SARS-CoV-2 IgG antibodies were also more 11 obviously observed than IgM in the follow-up patients (#9-14), when compared with healthy 12 donors ( Figure 1B ). As shown in Figure 3C , compared with healthy donors, 25 the numbers of IFN-γ-secreting NP-specific T cells in patients #1, 2, 4, 5 and 8 were much 26 higher than other patients, suggesting that they had developed SARS-CoV-2-specific T cell responses. More interestingly, when combining all 14 patients in our analysis, there 9 was a significant correlation between the neutralizing antibody titers and the numbers of NPIn this study, we characterized SARS-CoV-2-specific humoral and cellular immunity in 2 recovered patients.
cord-342312-rnq1hfsj	2020	To evaluate the effect of specific antibodies on RP status, we compared the levels of anti-SARS-CoV-2 IgG to the S, RBD, HR1-HR2, N, and M proteins in these patients during their convalescent period ( Fig. 1c; Fig. S3 ). The P value was calculated using a two-tailed Mann-Whitney U test the level of IgM to the RBD protein among these recovered patients also correlated with the S, HR1-HR2, and N proteins (r = 0.67, p < 0.0001; r = 0.56, p < 0.0001; and r = 0.60, p < 0.0001, respectively) (Fig. S6b) . In addition, a positive correlation was also observed between age and IgG level to the RBD, S, HR1-HR2, and N proteins (r = 0.38, P = 0.0077; r = 0.40, P = 0.0055; r = 0.45, P = 0.0017; and r = 0.44, P = 0.0021, respectively; Fig. S7 ), indicating the important role of age in the generation of specific binding antibodies. The online version of this article (https://doi.org/10.1038/s41423-020-00528-0) contains supplementary material.Competing interests: The authors declare no competing interests.
cord-342557-a7q8vp8m	2020	[Image: see text] Over 50 peptides, which were known to inhibit SARS-CoV-1, were computationally screened against the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2. Peptides that showed higher S protein-binding affinity compared to the α-helix (AH) of the ACE2 peptidase were further analyzed with molecular dynamics (MD) simulation and the structure− activity relationship (SAR) in order to achieve a high-affinity binder for the S protein. 30 Initially, stepwise multiple linear regression (MLR) was performed considering these properties as variables to predict the calculated binding affinity of the test peptides with the RBD of the SARS CoV-2 spike protein. All 51 peptides were docked to the RBD of the SARS CoV-2 spike protein using PatchDock. Various residues including Glu484, Tyr449, and Tyr505 present in the ACE2 binding site of the RBD were involved in noncovalent interaction with the antiviral peptides ( Figure 1a) .
cord-343107-oj1re34k	2019	Most neutralizing antibodies against Middle East respiratory syndrome coronavirus (MERS-CoV) target the receptor-binding domain (RBD) of the spike glycoprotein and block its binding to the cellular receptor dipeptidyl peptidase 4 (DPP4). Here we report the monoclonal antibody 7D10 that binds to the N-terminal domain (NTD) of the spike glycoprotein and inhibits the cell entry of MERS-CoV with high potency. The 7D10 antibody recognizes the NTD of MERS-CoV S glycoprotein and neutralizes the infectivity of pseudotyped and live virus with a potency comparable to those of the most active RBD-targeting antibodies. The NTD N222Q mutation also dramatically reduced the binding and neutralization by 7D10, but did not dramatically affect the cell infection of pseudotyped MERS-CoV ( Supplementary Fig. 11) . A conformation-dependent neutralizing monoclonal antibody specifically targeting receptor-binding domain in Middle East respiratory syndrome coronavirus spike protein A humanized neutralizing antibody against MERS-CoV targeting the receptor-binding domain of the spike protein
cord-343185-lbmbp9ca	2020	Here we have developed novel flexible ELISA-based assays for specific detection of SARS-CoV-2 antibodies against the receptor-binding domain (RBD): An antigen sandwich-ELISA relevant for large population screening and three isotype-specific assays for in-depth diagnostics. Detection of IgM, IgA and IgG antibodies against SARS-CoV-2 protein N was evaluated by analyzing 136 positive samples and 174 negative controls and ROC curve analyses were assessed to estimate the assay performance . To provide a better insight into antibody seroconversion during SARS-CoV-2 infection and reactivity against different locations on protein S and protein N, we conducted IgM, IgA and IgG detection in 90 positive samples against 14 protein fragments and short peptides located on the protein S and protein N structures, full-length RBD, protein S and protein N (Figure 2A ). We have developed an ELISA-based platform for detection SARS-CoV-2 antibodies comprising an indirect RBD S-ELISA for pan Ig detection and direct ELISAs for in-depth analyses of the IgM, IgA and IgG isotype responses towards RBD and protein N.
cord-344180-v8xs5ej8	2020	In this work, we report the synthesis of a cheap, yet highly sensitive, cobalt-functionalized TiO(2) nanotubes (Co-TNTs)-based electrochemical sensor for rapid detection of SARS-CoV-2 through sensing the spike (receptor binding domain (RBD)) present on the surface of the virus. In the current work, we have determined the potential of Co-functionalized TiO2 nanotubes (Co-TNTs) for the electrochemical detection of S-RBD protein of SARS-CoV-2. In the current work, we have determined the potential of Co-functionalized TiO2 nanotubes (Co-TNTs) for the electrochemical detection of S-RBD protein of SARS-CoV-2. Our data shows that cobalt functionalized TNTs can selectively detect the S-RBD protein of SARS-CoV-2 using the amperometry electrochemical technique in ~30 s. Our data shows that cobalt functionalized TNTs can selectively detect the S-RBD protein of SARS-CoV-2 using the amperometry electrochemical technique in ~30 s. In this study, we developed a Co-metal functionalized TNT as a sensing material for electrochemical detection of SARS-CoV-2 infection through the detection of the receptor binding domain (RBD) of spike glycoprotein.
cord-344871-486sk4wc	2016	We have previously shown that a non-structural protein 1 (NS1)-binding monoclonal antibody, termed as 2H6, can significantly reduce influenza A virus (IAV) replication when expressed intracellularly. As comparative ELISA in this and previous studies 29 showed that residues N48 and T49 in NS1(RBD) are important for the interaction with mAb 2H6, they were defined as active residues involved in the binding interaction to generate a series of models of the NS1(RBD) and 2H6-Fab complex. Overall, the predicted model from cluster 2 is consistent with our comparative ELISA data and suggests that residues N48 and T49 are important for the binding between NS1(RBD) and 2H6-Fab because their side-chains could make hydrogen bonds with residues in the VH-CDR2 of the Fab. In addition, R44 of NS1(RBD) was distal from the antibody-antigen interface, which is consistent with the results from comparative ELISA ( Figure S1 ) showing that substitution of R44 of NS1(RBD) with K did not affect its interaction with mAb 2H6.
cord-346670-34wfy52f	2020	Most structures of the SARS-CoV-2 S ectodomain currently available include two mutations, one to disrupt the furin cleavage site (RRAR to GSAS = S-GSAS), and a double proline mutation (PP) of residues 986-987, designed to prevent conformational change to the post-fusion state (Wrapp et al., 2020) . While the SARS-CoV-2 S ectodomain construct that includes mutations of residues K986 and V987, between the HR1 and CH subdomains (S2 domain), to prolines (PP) (named S-GSAS/PP in this study) (Figure 1 ) is widely used in the field, the origin of this PP construct was based upon the stabilization of the pre-fusion conformation of other coronavirus spikes (Pallesen et al., 2017; Walls et al., 2020; Wrapp et al., 2020) . Similar to observations made with the S-GSAS/D614G S ectodomain structure, the RBD up/down motion in the furin-cleaved G614 S ectodomain was associated with a movement in the SD1 domain and in the region of the RBD-to-NTD linker that joined the SD1 b sheet ( Figure 7C, S8B) .
cord-347587-auook38y	2018	title: A Novel Nanobody Targeting Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Receptor-Binding Domain Has Potent Cross-Neutralizing Activity and Protective Efficacy against MERS-CoV In this study, we developed a novel neutralizing Nb (NbMS10) and its human-Fc-fused version (NbMS10-Fc), both of which target the MERS-CoV spike protein receptor-binding domain (RBD). Identification and characterization of MERS-CoV-RBD-specific Nbs. To construct the Nb (i.e., VHH) library, we immunized llama with recombinant MERS-CoV RBD (residues 377 to 588, EMC2012 strain) containing a C-terminal human IgG1 Fc tag (i.e., RBD-Fc) and isolated peripheral blood mononuclear cells (PBMCs) from the immunized llama. To examine of the role of the D539A mutation in DPP4 binding, we carried out an ELISA to detect the binding between DPP4 and The plates were coated with RBD-Fd protein (2 g/ml) and treated with or without DTT, followed by sequential incubation with serial dilutions of NbMS10 or NbMS10-Fc and goat anti-llama and HRP-conjugated anti-goat IgG antibodies.
cord-348455-vcxalkeo	2020	title: Kinetics and Isotype Assessment of Antibodies Targeting the Spike Protein Receptor Binding Domain of SARS-CoV-2 In COVID-19 Patients as a function of Age and Biological Sex. date: 2020-07-22 The receptor-binding domain of the CoV spike (RBD-S) protein is important in host cell recognition and infection and antibodies targeting this domain are often neutralizing. We first piloted our antigen preps for the RBD-S IgG screening assay using serum 81 samples from a PCR-confirmed severe COVID-19 patient (defined as admission to the Intensive 82 Care Unit, ICU) who was admitted to the hospital 10 days following symptom onset and based 83 on an early report suggesting that SARS-CoV-2 could trigger antibody responses in this 84 timeframe (24). Anti-S titers in patients with a negative RBD-S test were 138 generally low and in RBD-positive samples, followed the same trends as RBD-reactivity, 139 providing further confirmation of robust serological responses to SARS-CoV-2 during acute 140 COVID-19.
cord-351760-698voi9y	2018	The receptor-binding domain (RBD) in the spike protein of MERS-CoV is a major target, and mouse, camel, or human-derived neutralizing mAbs targeting RBD have been developed. In vivo study demonstrated that prophylaxis with m336 reduced virus titers in the lung of rabbits infected with MERS-CoV [15] , and m336 also provided transgenic mice expressing human DPP4 with full prophylactic and therapeutic protection from MERS-CoV [16] . A Conformation-Dependent Neutralizing Monoclonal Antibody Specifically Targeting Receptor-Binding Domain in Middle East Respiratory Syndrome Coronavirus Spike Protein Prophylaxis with a Middle East Respiratory Syndrome Coronavirus (MERS-CoV)-Specific Human Monoclonal Antibody Protects Rabbits From MERS-CoV Infection Passive Transfer of a Germline-like Neutralizing Human Monoclonal Antibody Protects Transgenic Mice Against Lethal Middle East Respiratory Syndrome Coronavirus Infection Human Neutralizing Monoclonal Antibody Inhibition of Middle East Respiratory Syndrome Coronavirus Replication in the Common Marmoset A Novel Nanobody Targeting Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Receptor-Binding Domain Has Potent Cross-Neutralizing Activity and Protective Efficacy against MERS-CoV
cord-352527-eeyqh9nc	2019	A number of MERS vaccines have been developed based on viral RBD, including nanoparticles, virus-like particles (VLPs), and recombinant proteins, and their protective efficacy has been evaluated in animal models, including mice with adenovirus 5 (Ad5)-directed expression of human DPP4 (Ad5/hDPP4), hDPP4-transgenic (hDPP4-Tg) mice, and non-human primates (NHPs) [88] [89] [90] [91] [92] [93] [94] . Receptor usage of a novel bat lineage C Betacoronavirus reveals evolution of Middle East respiratory syndrome-related coronavirus spike proteins for human dipeptidyl peptidase 4 binding Recombinant receptor-binding domains of multiple Middle East respiratory syndrome coronaviruses (MERS-CoVs) induce cross-neutralizing antibodies against divergent human and camel MERS-CoVs and antibody escape mutants A conformation-dependent neutralizing monoclonal antibody specifically targeting receptor-binding domain in Middle East respiratory syndrome coronavirus spike protein A novel nanobody targeting Middle East respiratory syndrome coronavirus (MERS-CoV) receptor-binding domain has potent cross-neutralizing activity and protective efficacy against MERS-CoV
cord-352934-ypls4zau	2020	title: Human IgG neutralizing monoclonal antibodies block SARS-CoV-2 infection We screened sera samples from 11 patients recently recovered from COVID-19, and 119 found all individuals showed certain levels of serological responses, with #507 and 120 #501 being the weakest, to SARS-CoV-2 Spike RBD and S1 proteins ( Figure 1A ). We 121 also found that 10 sera, except for 507, showed neutralization abilities against 122 SARS-CoV-2 pseudoviral infection of HEK293T cells stably expressing human ACE2 123 ( Figure 1B ). In order to screen for SARS-CoV-2 spike antigen specific monoclonal antibodies, we 143 used two primary assays based on ELISA (enzyme linked immunosorbent assay) and 144 FCA (flow cytometry assay), respectively. Human monoclonal antibodies block the binding of SARS-CoV-2 spike protein to angiotensin 561 converting enzyme 2 receptor A potent neutralizing human antibody reveals the N-terminal domain of the 564 Spike protein of SARS-CoV-2 as a site of vulnerability Potent binding of 2019 novel coronavirus spike protein by a SARS coronavirus-specific 612 human monoclonal antibody
cord-353161-mtq6yh25	2020	We found that species known not to be susceptible to SARS-CoV-2 infection have non-conservative mutations in several ACE2 amino acid residues that disrupt key polar and charged contacts with the viral spike protein. Collectively, our results provide a structural framework that explains why certain animal species are not susceptible to SARS-CoV-2 infection, and also suggests potential mutations that can enhance binding to the viral RBD. Although it is well-known that docking scores do not quantitatively correlate with experimental binding affinities [19] , these scores suggest that SARS-CoV-2 neg species lack one or more key ACE2 residues that contribute significantly to the interaction with RBD. Models of SARS-CoV-2 neg species -chicken, duck, guinea pig, mouse, and rat -generally have higher (worse) HADDOCK scores than average (Figure 2 ), suggesting that these species'' non-susceptibility to infection could stem from deficient RBD binding to ACE2.
cord-353748-y1a52z8e	2021	title: A natural food preservative peptide nisin can interact with the SARS-CoV-2 spike protein receptor human ACE2 Nisin, a food-grade antimicrobial peptide produced by lactic acid bacteria has been examined for its probable interaction with the human ACE2 (hACE2) receptor, the site where spike protein of SARS-CoV-2 binds. Among the eight nisin variants examined, nisin H, nisin Z, nisin U and nisin A showed a significant binding affinity towards hACE2, higher than that of the RBD (receptor binding domain) of the SARS-CoV-2 spike protein. The present study attempts to investigate the ability of food-grade nisin A and its natural variants to block the interaction between hACE2 and the spike protein of SARS-CoV-2, a key step of COVID-19 disease initiation. The binding affinity of docked structures of all eight variants of nisin in complex with hACE2 was calculated as ΔG derived from analysis with Prodigy for each complex in comparison with the RBD of spike protein of SARS-CoV-2.
cord-354868-pqn59ojj	2020	title: A high-affinity RBD-targeting nanobody improves fusion partner''s potency against SARS-CoV-2 Considerable research have been devoted to the development of neutralizing antibodies, including llama-derived single-chain nanobodies, to target the receptor-binding motif (RBM) and to block ACE2-RBD binding. A high-affinity RBD binder without neutralizing activity 85 Previously, we generated 99 sybodies from three highly diverse synthetic libraries by ribosome and phage display with in vitro selections against the SARS-CoV-2 RBD. Consistent with its inability to neutralize SARS-CoV-2 pseudovirus, SR31 did not affect RBD-ACE2 binding (Fig. 1C) . Most RBD-targeting neutralizing antibodies, including neutralizing nanobodies characterized so far (8, 13-15, 19, 20, 22-24, 26-28, 34, 35, 37) , engage the RBD at the receptor-binding motif (RBM) (Fig. 3A) , thus competing off ACE2 and preventing viral entry. Taken together, the structural data rationalize the high-affinity binding between SR31 and RBD, and its inability to neutralize SARS-CoV-2. Neutralizing nanobodies bind SARS-CoV-2 spike RBD and block interaction with ACE2
cord-355728-wivk0bm0	2020	Here, we develop single-domain antibodies (nanobodies) that potently disrupt the interaction between the SARS-CoV-2 Spike and ACE2. Cryogenic electron microscopy (cryo-EM) revealed that one exceptionally stable nanobody, Nb6, binds Spike in a fully inactive conformation with its receptor binding domains (RBDs) locked into their inaccessible down-state, incapable of binding ACE2. Class I nanobodies emerged with highly 144 variable activity in this assay with Nb6 and Nb11 as two of the most potent clones with IC50 145 values of 370 and 540 nM, respectively (Table 1) To define the binding sites of Nb6 and Nb11, we determined their cryogenic electron 156 microscopy (cryo-EM) structures bound to Spike* ( Fig. 2A state RBDs only contacts a single RBD (Fig. 2D) . 277 278 mNb6-tri displays further gains in potency in both pseudovirus and live SARS-CoV-2 infection 279 assays with IC50 values of 120 pM (5.0 ng/mL) and 54 pM (2.3 ng/mL), respectively (Fig. 4H-I, 280 Table 1).
cord-355807-q3bngari	2020	Molecular modeling was carried out to evaluate the potential antiviral properties of the components of the medicinal herb Uncaria tomentosa (cat''s claw) focusing on the binding interface of the RBD–ACE-2 and the viral spike protein. tomentosa against focusing both on the binding interface of the RBD-ACE-2 and inside SARS-CoV-2 RBD spike protein, (2) simulations of ligand pathway of the best predicted compounds from step 1 to evaluate convenient entrance mechanism of the compounds to the binding site, (3) MD simulation to assess the stability of the best protein-ligand complexes from 1, (4) calculation of pharmacokinetics parameters for the most qualified compounds resulting from the previous parts of the docking protocol. Next, we used the cryo-EM structure of SARS-CoV-2 spike protein (PDB code: 6VYB) in their open state (Lipinski et al., 2012) to explore the potential inhibition of components of the cat''s claw, selecting ACE-2-binding pocket to this study.
cord-356264-q0yqnlyl	2020	With this analysis, we determine a region inside the receptor-binding domain with putative sites under positive selection interspersed among highly conserved sites, which are implicated in structural stability of the viral spike protein and its union with human receptor hACE2. We employ a multidisciplinary approach to look for evidence of diversifying selection on the S-protein gene, and model the interactions between human ACE2 (hACE2) and the RBD of selected coronavirus strains, which ultimately afforded us novel insights detailing virus and host cell interactions. All these experiments were performed again using the S-protein genes of a shorter list of accessions and more distantly related (broad dataset) to SARS-COV-2 (AY304488, AY395003, DQ412043, FJ882957, KY417144, MG772933, MG772934, MN908947, NC_004718) to test the reproducibility of the predicted branches and sites under positive selection. Modeling results suggest that interference with the hot spot 353 could be and effective strategy for inhibiting the recognition of the RBD of the SARS-COV-2 spike protein by its human host receptor ACE2 and hence prevent infections.