scholarly journals Plant-Produced Glycosylated and In Vivo Deglycosylated Receptor Binding Domain Proteins of SARS-CoV-2 Induce Potent Neutralizing Responses in Mice

Viruses ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1595
Author(s):  
Tarlan Mamedov ◽  
Damla Yuksel ◽  
Merve Ilgın ◽  
Irem Gurbuzaslan ◽  
Burcu Gulec ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Plant Biomass ◽  
Specific Binding ◽  
High Titer ◽  
Binding Domain ◽  
Receptor Binding Domain ◽  
S Protein ◽  
Vaccine Candidates ◽  
Neutralizing Activity

The COVID-19 pandemic, caused by SARS-CoV-2, has rapidly spread to more than 222 countries and has put global public health at high risk. The world urgently needs cost-effective and safe SARS-CoV-2 vaccines, antiviral, and therapeutic drugs to control it. In this study, we engineered the receptor binding domain (RBD) of the SARS-CoV-2 spike (S) protein and produced it in the plant Nicotiana benthamiana in a glycosylated and deglycosylated form. Expression levels of both glycosylated (gRBD) and deglycosylated (dRBD) RBD were greater than 45 mg/kg fresh weight. The purification yields were 22 mg of pure protein/kg of plant biomass for gRBD and 20 mg for dRBD, which would be sufficient for commercialization of these vaccine candidates. The purified plant-produced RBD protein was recognized by an S protein-specific monoclonal antibody, demonstrating specific reactivity of the antibody to the plant-produced RBD proteins. The SARS-CoV-2 RBD showed specific binding to angiotensin converting enzyme 2 (ACE2), the SARS-CoV-2 receptor. In mice, the plant-produced RBD antigens elicited high titers of antibodies with a potent virus-neutralizing activity. To our knowledge, this is the first report demonstrating that mice immunized with plant-produced deglycosylated RBD form elicited high titer of RBD-specific antibodies with potent neutralizing activity against SARS-CoV-2 infection. Thus, obtained data support that plant-produced glycosylated and in vivo deglycosylated RBD antigens, developed in this study, are promising vaccine candidates for the prevention of COVID-19.

scholarly journals A Recombinant Protein SARS-CoV-2 Candidate Vaccine Elicits High-titer Neutralizing Antibodies in Macaques.

2021 ◽  
Author(s):  
Gary Baisa ◽  
David Rancour ◽  
Keith Mansfield ◽  
Monika Burns ◽  
Lori Martin ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
High Titer ◽  
Binding Domain ◽  
Pseudotyped Virus ◽  
Receptor Binding Domain ◽  
Binding Assays ◽  
Neutralizing Activity ◽  
Terminal Domain

Abstract BackgroundVaccines that generate robust and long-lived protective immunity against SARS-CoV-2 infection are urgently required. MethodsWe assessed the potential of vaccine candidates based on the SARS-CoV-2 spike in cynomolgus macaques (M. fascicularis) by examining their ability to generate spike binding antibodies with neutralizing activity. Antigens were derived from two distinct regions of the spike S1 subunit, either the N-terminal domain or an extended C-terminal domain containing the receptor-binding domain and were fused to the human IgG1 Fc domain. Three groups of 2 animals each were immunized with either antigen, alone or in combination. The development of antibody responses was evaluated through 20 weeks post-immunization. ResultsA robust IgG response to the spike protein was detected as early as 2 weeks after immunization with either protein and maintained for over 20 weeks. Sera from animals immunized with antigens derived from the RBD were able to prevent binding of soluble spike proteins to the ACE2 receptor, shown by in vitro binding assays, while sera from animals immunized with the N-terminal domain alone lacked this activity. Crucially, sera from animals immunized with the extended receptor binding domain but not the N-terminal domain had potent neutralizing activity against SARS-CoV-2 pseudotyped virus, with titers in excess of 10,000, greatly exceeding that typically found in convalescent humans. Neutralizing activity persisted for more than 20 weeks. ConclusionsThese data support the utility of spike subunit-based antigens as a vaccine for use in humans.

scholarly journals Engineering, production and characterization of Spike and Nucleocapsid structural proteins of SARS–CoV-2 in Nicotiana benthamiana as vaccine candidates against COVID-19

2020 ◽  
Author(s):  
Tarlan Mamedov ◽  
Damla Yuksel ◽  
Merve Ilgın ◽  
İrem Gürbüzaslan ◽  
Burcu Gulec ◽  
...  
Keyword(s):  
Nicotiana Benthamiana ◽  
Plant Biomass ◽  
Specific Binding ◽  
Polyclonal Antibodies ◽  
High Titer ◽  
Protein S ◽  
Global Public Health ◽  
S Protein ◽  
Vaccine Candidates ◽  
Protein Variants

AbstractThe COVID-19 pandemic, which is caused by SARS-CoV-2 has rapidly spread to more than 216 countries and has put global public health at high risk. The world urgently needs a cost-effective and safe SARS-CoV-2 coronavirus vaccine, antiviral and therapeutic drugs to control the COVID-19 pandemic. In this study, we engineered the Nucleocapsid (N) and Spike protein (S) variants (Receptor binding domain, RBD and S1 domain) of SARS-CoV-2 genes and produced in Nicotiana benthamiana plant. The purification yields were at least 20 mg of pure protein/kg of plant biomass for each target protein. The S protein variants of SARS-CoV-2 showed specific binding to angiotensin converting enzyme 2 (ACE2), the SARS-CoV-2 receptor. The purified plant produced N and S variants were recognized by N and S protein specific monoclonal and polyclonal antibodies demonstrating specific reactivity of mAb to plant produced N and S protein variants. In addition, IgG responses of plant produced N and S antigens elicited significantly high titers of antibody in mice. This is the first report demonstrating production of functional active S1 domain and Nucleocapsid protein of SARC-CoV-2 in plants. In addition, in this study, for the first time, we report the co-expression of RBD with N protein to produce a cocktail antigen of SARS-CoV-2, which elicited high-titer antibodies compared to RBD or N proteins. Thus, obtained data support that plant produced N and S antigens, developed in this study, are promising vaccine candidates against COVID-19.

scholarly journals 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

2018 ◽  
Vol 92 (18) ◽  
Author(s):  
Guangyu Zhao ◽  
Lei He ◽  
Shihui Sun ◽  
Hongjie Qiu ◽  
Wanbo Tai ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Broad Spectrum ◽  
Half Life ◽  
Cost Effective ◽  
Binding Domain ◽  
Humanized Mice ◽  
Receptor Binding Domain ◽  
Neutralizing Activity ◽  
High Affinity

ABSTRACT The newly emerged Middle East respiratory syndrome coronavirus (MERS-CoV) continues to infect humans and camels, calling for efficient, cost-effective, and broad-spectrum strategies to control its spread. Nanobodies (Nbs) are single-domain antibodies derived from camelids and sharks and are potentially cost-effective antivirals with small size and great expression yield. 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). We further tested their receptor-binding affinity, recognizing epitopes, cross-neutralizing activity, half-life, and efficacy against MERS-CoV infection. Both Nbs can be expressed in yeasts with high yield, bind to MERS-CoV RBD with high affinity, and block the binding of MERS-CoV RBD to the MERS-CoV receptor. The binding site of the Nbs on the RBD was mapped to be around residue Asp539, which is part of a conserved conformational epitope at the receptor-binding interface. NbMS10 and NbMS10-Fc maintained strong cross-neutralizing activity against divergent MERS-CoV strains isolated from humans and camels. Particularly, NbMS10-Fc had significantly extended half-life in vivo; a single-dose treatment of NbMS10-Fc exhibited high prophylactic and therapeutic efficacy by completely protecting humanized mice from lethal MERS-CoV challenge. Overall, this study proves the feasibility of producing cost-effective, potent, and broad-spectrum Nbs against MERS-CoV and has produced Nbs with great potentials as anti-MERS-CoV therapeutics. IMPORTANCE Therapeutic development is critical for preventing and treating continual MERS-CoV infections in humans and camels. Because of their small size, nanobodies (Nbs) have advantages as antiviral therapeutics (e.g., high expression yield and robustness for storage and transportation) and also potential limitations (e.g., low antigen-binding affinity and fast renal clearance). Here, we have developed novel Nbs that specifically target the receptor-binding domain (RBD) of MERS-CoV spike protein. They bind to a conserved site on MERS-CoV RBD with high affinity, blocking RBD's binding to MERS-CoV receptor. Through engineering a C-terminal human Fc tag, the in vivo half-life of the Nbs is significantly extended. Moreover, the Nbs can potently cross-neutralize the infections of diverse MERS-CoV strains isolated from humans and camels. The Fc-tagged Nb also completely protects humanized mice from lethal MERS-CoV challenge. Taken together, our study has discovered novel Nbs that hold promise as potent, cost-effective, and broad-spectrum anti-MERS-CoV therapeutic agents.

scholarly journals Cross-reactive neutralization of SARS-CoV-2 by serum antibodies from recovered SARS patients and immunized animals

2020 ◽  
Vol 6 (45) ◽  
pp. eabc9999 ◽  
Author(s):  
Yuanmei Zhu ◽  
Danwei Yu ◽  
Yang Han ◽  
Hongxia Yan ◽  
Huihui Chong ◽  
...  
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Receptor Binding ◽  
Binding Domain ◽  
Full Length ◽  
Receptor Binding Domain ◽  
Serum Antibodies ◽  
Serum Samples ◽  
S Protein ◽  
Novel Coronavirus

The current coronavirus disease 2019 (COVID-19) pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel coronavirus genetically close to SARS-CoV. To investigate the effects of previous SARS-CoV infection on the ability to recognize and neutralize SARS-CoV-2, we analyzed 20 convalescent serum samples collected from individuals infected with SARS-CoV during the 2003 SARS outbreak. All patient sera reacted strongly with the S1 subunit and receptor binding domain (RBD) of SARS-CoV; cross-reacted with the S ectodomain, S1, RBD, and S2 proteins of SARS-CoV-2; and neutralized both SARS-CoV and SARS-CoV-2 S protein–driven infections. Analysis of antisera from mice and rabbits immunized with a full-length S and RBD immunogens of SARS-CoV verified cross-reactive neutralization against SARS-CoV-2. A SARS-CoV–derived RBD from palm civets elicited more potent cross-neutralizing responses in immunized animals than the RBD from a human SARS-CoV strain, informing strategies for development of universal vaccines against emerging coronaviruses.

scholarly journals Xeno-Nucleic Acid (XNA) 2’-Fluoro-Arabino Nucleic Acid (FANA) Aptamers to the Receptor-Binding Domain of SARS-CoV-2 S Protein Block ACE2 Binding

Viruses ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1983
Author(s):  
Irani Alves Ferreira-Bravo ◽  
Jeffrey J. DeStefano
Keyword(s):  
Nucleic Acid ◽  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Dissociation Constants ◽  
High Specificity ◽  
Binding Domain ◽  
Host Cells ◽  
Receptor Binding Domain ◽  
S Protein ◽  
Equilibrium Dissociation Constants

The causative agent of COVID-19, SARS-CoV-2, gains access to cells through interactions of the receptor-binding domain (RBD) on the viral S protein with angiotensin-converting enzyme 2 (ACE2) on the surface of human host cells. Systematic evolution of ligands by exponential enrichment (SELEX) was used to generate aptamers (nucleic acids selected for high binding affinity to a target) to the RBD made from 2ʹ-fluoro-arabinonucleic acid (FANA). The best selected ~79 nucleotide aptamers bound the RBD (Arg319-Phe541) and the larger S1 domain (Val16-Arg685) of the 1272 amino acid S protein with equilibrium dissociation constants (KD,app) of ~10–20 nM, and binding half-life for the RBD, S1 domain, and full trimeric S protein of 53 ± 18, 76 ± 5, and 127 ± 7 min, respectively. Aptamers inhibited the binding of the RBD to ACE2 in an ELISA assay. Inhibition, on a per weight basis, was similar to neutralizing antibodies that were specific for RBD. Aptamers demonstrated high specificity, binding with about 10-fold lower affinity to the related S1 domain from the original SARS virus, which also binds to ACE2. Overall, FANA aptamers show affinities comparable to previous DNA aptamers to RBD and S1 protein and directly block receptor interactions while using an alternative Xeno-nucleic acid (XNA) platform.

scholarly journals An Engineered Receptor-Binding Domain Improves the Immunogenicity of Multivalent SARS-CoV-2 Vaccines

mBio ◽  
2021 ◽  
Vol 12 (3) ◽  
Author(s):  
Yan Guo ◽  
Wenhui He ◽  
Huihui Mou ◽  
Lizhou Zhang ◽  
Jing Chang ◽  
...  
Keyword(s):  
Amino Acid ◽  
Receptor Binding ◽  
Binding Domain ◽  
Full Length ◽  
Vaccine Antigen ◽  
Receptor Binding Domain ◽  
Protein Vaccine ◽  
Wild Type ◽  
S Protein ◽  
Glycosylation Sites

ABSTRACT The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein mediates viral entry into cells expressing angiotensin-converting enzyme 2 (ACE2). The S protein engages ACE2 through its receptor-binding domain (RBD), an independently folded 197-amino-acid fragment of the 1,273-amino-acid S-protein protomer. The RBD is the primary SARS-CoV-2 neutralizing epitope and a critical target of any SARS-CoV-2 vaccine. Here, we show that this RBD conjugated to each of two carrier proteins elicited more potent neutralizing responses in immunized rodents than did a similarly conjugated proline-stabilized S-protein ectodomain. Nonetheless, the native RBD is expressed inefficiently, limiting its usefulness as a vaccine antigen. However, we show that an RBD engineered with four novel glycosylation sites (gRBD) is expressed markedly more efficiently and generates a more potent neutralizing responses as a DNA vaccine antigen than the wild-type RBD or the full-length S protein, especially when fused to multivalent carriers, such as a Helicobacter pylori ferritin 24-mer. Further, gRBD is more immunogenic than the wild-type RBD when administered as a subunit protein vaccine. Our data suggest that multivalent gRBD antigens can reduce costs and doses, and improve the immunogenicity, of all major classes of SARS-CoV-2 vaccines. IMPORTANCE All available vaccines for coronavirus disease 2019 (COVID-19) express or deliver the full-length SARS-CoV-2 spike (S) protein. We show that this antigen is not optimal, consistent with observations that the vast majority of the neutralizing response to the virus is focused on the S-protein receptor-binding domain (RBD). However, this RBD is not expressed well as an independent domain, especially when expressed as a fusion protein with a multivalent scaffold. We therefore engineered a more highly expressed form of the SARS-CoV-2 RBD by introducing four glycosylation sites into a face of the RBD normally occluded in the full S protein. We show that this engineered protein, gRBD, is more immunogenic than the wild-type RBD or the full-length S protein in both genetic and protein-delivered vaccines.

scholarly journals Antibodies with potent and broad neutralizing activity against antigenically diverse and highly transmissible SARS-CoV-2 variants

2021 ◽  
Author(s):  
Lingshu Wang ◽  
Tongqing Zhou ◽  
Yi Zhang ◽  
Eun Sung Yang ◽  
Chaim A. Schramm ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Binding Domain ◽  
Receptor Binding Domain ◽  
Therapeutic Antibodies ◽  
Resistance Development ◽  
Neutralizing Activity ◽  
Escape Mutants

AbstractThe emergence of highly transmissible SARS-CoV-2 variants of concern (VOC) that are resistant to therapeutic antibodies highlights the need for continuing discovery of broadly reactive antibodies. We identify four receptor-binding domain targeting antibodies from three early-outbreak convalescent donors with potent neutralizing activity against 12 variants including the B.1.1.7 and B.1.351 VOCs. Two of them are ultrapotent, with sub-nanomolar neutralization titers (IC50 <0.0006 to 0.0102 μg/mL; IC80 < 0.0006 to 0.0251 μg/mL). We define the structural and functional determinants of binding for all four VOC-targeting antibodies, and show that combinations of two antibodies decrease the in vitro generation of escape mutants, suggesting potential means to mitigate resistance development. These results define the basis of therapeutic cocktails against VOCs and suggest that targeted boosting of existing immunity may increase vaccine breadth against VOCs.One Sentence SummaryUltrapotent antibodies from convalescent donors neutralize and mitigate resistance of SARS-CoV-2 variants of concern.

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