scholarly journals A highly thermotolerant, trimeric SARS-CoV-2 receptor binding domain derivative elicits high titers of neutralizing antibodies

2021 ◽  
Author(s):  
Sameer Kumar Malladi ◽  
Unnatiben Rajeshbhai Patel ◽  
Randhir Singh ◽  
Suman Pandey ◽  
Sahil Kumar ◽  
...  
Keyword(s):  
Mammalian Cell ◽  
Receptor Binding ◽  
Guinea Pigs ◽  
Neutralizing Antibodies ◽  
Matrix Protein ◽  
Geometric Mean ◽  
Binding Domain ◽  
Cold Chain ◽  
High Yield ◽  
Receptor Binding Domain

AbstractThe Receptor Binding Domain of SARS-CoV-2 is the primary target of neutralizing antibodies. We fused our previously described, highly thermotolerant glycan engineered monomeric RBD to a heterologous non-immunogenic trimerization domain derived from cartilage matrix protein. The protein was expressed at a good yield of ∼80-100 mg/liter in Expi293 cells, as well as in both CHO and HEK293 stable cell lines. The designed trimeric RBD was observed to form homogeneous disulfide-linked trimers. When lyophilized, the trimer possessed remarkable functional stability to transient thermal stress of upto 100 °C and was stable to long term storage of over 4 weeks at 37 °C. Two immunizations with an AddaVax adjuvanted formulation elicited antibodies with high endpoint neutralizing titers against replicative virus with geometric mean titers of ∼1114 and 1940 in guinea pigs and mice respectively. In pseudoviral assays, corresponding titers were ∼3600 and ∼16050, while the corresponding value for human convalescent sera was 137. Similar results were obtained with an Alhydrogel, CpG combination adjuvant. The same immunogen was expressed in Pichia pastoris, but this formed high molecular weight aggregates and elicited much lower ACE2 competing antibodies than mammalian cell expressed protein. The excellent thermotolerance, high yield, and robust immunogenicity of such trimeric RBD immunogens suggest that they are a promising modality to combat COVID-19.ImportanceSARS-CoV-2 is the causative agent of the ongoing COVID-19 pandemic. The viral surface exposed Spike glycoprotein is the target of neutralizing antibodies of which a major fraction targets the receptor binding domain (RBD). Thus RBD derived immunogens are attractive vaccine candidates. Monomeric, mammalian cell expressed RBD protein elicits low to moderate titers of neutralizing antibodies. We designed a highly expressed, trimeric RBD derivative with a non-immunogenic trimerization domain. In guinea pigs and mice respectively, this derivative induces 20-300 fold higher neutralizing antibody titers relative to convalescent human sera, while remaining conformationally intact after incubation for over four weeks at 37 °C and for ninety minutes at 100 °C when lyophilized. Such trimeric RBD formulations should not require a cold chain. Additionally, the high titers of neutralizing antibodies should buffer against viral sequence variation. These are both highly desirable attributes for a COVID-19 vaccine, especially in resource limited settings.

scholarly journals Rapid High-Yield Production of Functional SARS-CoV-2 Receptor Binding Domain by Viral and Non-Viral Transient Expression for Pre-Clinical Evaluation

Vaccines ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 654
Author(s):  
Omar Farnós ◽  
Alina Venereo-Sánchez ◽  
Xingge Xu ◽  
Cindy Chan ◽  
Shantoshini Dash ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Binding Domain ◽  
Added Value ◽  
High Yield ◽  
Conformational Structure ◽  
Receptor Binding Domain ◽  
Sialic Acid Content ◽  
Production Methods ◽  
Adenoviral Infection

Vaccine design strategies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are focused on the Spike protein or its subunits as the main antigen target of neutralizing antibodies. In this work, we propose rapid production methods of an extended segment of the Spike Receptor Binding Domain (RBD) in HEK293SF cells cultured in suspension, in serum-free media, as a major component of a COVID-19 subunit vaccine under development. The expression of RBD, engineered with a sortase-recognition motif for protein-based carrier coupling, was achieved at high yields by plasmid transient transfection or human type-5-adenoviral infection of the cells, in a period of only two and three weeks, respectively. Both production methods were evaluated in 3L-controlled bioreactors with upstream and downstream bioprocess improvements, resulting in a product recovery with over 95% purity. Adenoviral infection led to over 100 µg/mL of RBD in culture supernatants, which was around 7-fold higher than levels obtained in transfected cultures. The monosaccharide and sialic acid content was similar in the RBD protein from the two production approaches. It also exhibited a proper conformational structure as recognized by monoclonal antibodies directed against key native Spike epitopes. Efficient direct binding to ACE2 was also demonstrated at similar levels in RBD obtained from both methods and from different production lots. Overall, we provide bioprocess-related data for the rapid, scalable manufacturing of low cost RBD based vaccines against SARS-CoV-2, with the added value of making a functional antigen available to support further research on uncovering mechanisms of virus binding and entry as well as screening for potential COVID-19 therapeutics.

scholarly journals A Stabilized, Monomeric, Receptor Binding Domain Elicits High-Titer Neutralizing Antibodies Against All SARS-CoV-2 Variants of Concern

2021 ◽  
Vol 12 ◽  
Author(s):  
Shahbaz Ahmed ◽  
Mohammad Suhail Khan ◽  
Savitha Gayathri ◽  
Randhir Singh ◽  
Sahil Kumar ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Mammalian Cells ◽  
Neutralizing Antibodies ◽  
High Titer ◽  
Binding Domain ◽  
High Yield ◽  
High Dose ◽  
Receptor Binding Domain ◽  
Triple Mutant ◽  
Water Emulsion

Saturation suppressor mutagenesis was used to generate thermostable mutants of the SARS-CoV-2 spike receptor-binding domain (RBD). A triple mutant with an increase in thermal melting temperature of ~7°C with respect to the wild-type B.1 RBD and was expressed in high yield in both mammalian cells and the microbial host, Pichia pastoris, was downselected for immunogenicity studies. An additional derivative with three additional mutations from the B.1.351 (beta) isolate was also introduced into this background. Lyophilized proteins were resistant to high-temperature exposure and could be stored for over a month at 37°C. In mice and hamsters, squalene-in-water emulsion (SWE) adjuvanted formulations of the B.1-stabilized RBD were considerably more immunogenic than RBD lacking the stabilizing mutations and elicited antibodies that neutralized all four current variants of concern with similar neutralization titers. However, sera from mice immunized with the stabilized B.1.351 derivative showed significantly decreased neutralization titers exclusively against the B.1.617.2 (delta) VOC. A cocktail comprising stabilized B.1 and B.1.351 RBDs elicited antibodies with qualitatively improved neutralization titers and breadth relative to those immunized solely with either immunogen. Immunized hamsters were protected from high-dose viral challenge. Such vaccine formulations can be rapidly and cheaply produced, lack extraneous tags or additional components, and can be stored at room temperature. They are a useful modality to combat COVID-19, especially in remote and low-resource settings.

scholarly journals Stereotypic neutralizing VH antibodies against SARS-CoV-2 spike protein receptor binding domain in COVID-19 patients and healthy individuals

2021 ◽  
pp. eabd6990
Author(s):  
Sang Il Kim ◽  
Jinsung Noh ◽  
Sujeong Kim ◽  
Younggeun Choi ◽  
Duck Kyun Yoo ◽  
...  
Keyword(s):  
B Cells ◽  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
De Novo ◽  
Binding Domain ◽  
Host Cells ◽  
Spike Protein ◽  
Receptor Binding Domain ◽  
Healthy Individuals

Stereotypic antibody clonotypes exist in healthy individuals and may provide protective immunity against viral infections by neutralization. We observed that 13 out of 17 patients with COVID-19 had stereotypic variable heavy chain (VH) antibody clonotypes directed against the receptor-binding domain (RBD) of SARS-CoV-2 spike protein. These antibody clonotypes were comprised of immunoglobulin heavy variable (IGHV)3-53 or IGHV3-66 and immunoglobulin heavy joining (IGHJ)6 genes. These clonotypes included IgM, IgG3, IgG1, IgA1, IgG2, and IgA2 subtypes and had minimal somatic mutations, which suggested swift class switching after SARS-CoV-2 infection. The different immunoglobulin heavy variable chains were paired with diverse light chains resulting in binding to the RBD of SARS-CoV-2 spike protein. Human antibodies specific for the RBD can neutralize SARS-CoV-2 by inhibiting entry into host cells. We observed that one of these stereotypic neutralizing antibodies could inhibit viral replication in vitro using a clinical isolate of SARS-CoV-2. We also found that these VH clonotypes existed in six out of 10 healthy individuals, with IgM isotypes predominating. These findings suggest that stereotypic clonotypes can develop de novo from naïve B cells and not from memory B cells established from prior exposure to similar viruses. The expeditious and stereotypic expansion of these clonotypes may have occurred in patients infected with SARS-CoV-2 because they were already present.

scholarly journals mRNA vaccination boosts cross-variant neutralizing antibodies elicited by SARS-CoV-2 infection

Science ◽  
2021 ◽  
pp. eabg9175 ◽  
Author(s):  
Leonidas Stamatatos ◽  
Julie Czartoski ◽  
Yu-Hsin Wan ◽  
Leah J. Homad ◽  
Vanessa Rubin ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Binding Domain ◽  
Receptor Binding Domain ◽  
Previous Infection

Emerging SARS-CoV-2 variants have raised concerns about resistance to neutralizing antibodies elicited by previous infection or vaccination. We examined whether sera from recovered and naïve donors collected prior to, and following immunizations with existing mRNA vaccines, could neutralize the Wuhan-Hu-1 and B.1.351 variants. Pre-vaccination sera from recovered donors neutralized Wuhan-Hu-1 and sporadically neutralized B.1.351, but a single immunization boosted neutralizing titers against all variants and SARS-CoV-1 by up to 1000-fold. Neutralization was due to antibodies targeting the receptor binding domain and was not boosted by a second immunization. Immunization of naïve donors also elicited cross-neutralizing responses, but at lower titers. Our study highlights the importance of vaccinating both uninfected and previously infected persons to elicit cross-variant neutralizing antibodies.

scholarly journals A COVID-19 vaccine candidate using SpyCatcher multimerization of the SARS-CoV-2 spike protein receptor-binding domain induces potent neutralising antibody responses

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tiong Kit Tan ◽  
Pramila Rijal ◽  
Rolle Rahikainen ◽  
Anthony H. Keeble ◽  
Lisa Schimanski ◽  
...  
Keyword(s):  
Antibody Response ◽  
Receptor Binding ◽  
Binding Domain ◽  
Cold Chain ◽  
Receptor Binding Domain ◽  
Cell Infection ◽  
Protein Receptor ◽  
Virus Like Particle ◽  
Human Sera ◽  
Escape Mutants

AbstractThere is need for effective and affordable vaccines against SARS-CoV-2 to tackle the ongoing pandemic. In this study, we describe a protein nanoparticle vaccine against SARS-CoV-2. The vaccine is based on the display of coronavirus spike glycoprotein receptor-binding domain (RBD) on a synthetic virus-like particle (VLP) platform, SpyCatcher003-mi3, using SpyTag/SpyCatcher technology. Low doses of RBD-SpyVLP in a prime-boost regimen induce a strong neutralising antibody response in mice and pigs that is superior to convalescent human sera. We evaluate antibody quality using ACE2 blocking and neutralisation of cell infection by pseudovirus or wild-type SARS-CoV-2. Using competition assays with a monoclonal antibody panel, we show that RBD-SpyVLP induces a polyclonal antibody response that recognises key epitopes on the RBD, reducing the likelihood of selecting neutralisation-escape mutants. Moreover, RBD-SpyVLP is thermostable and can be lyophilised without losing immunogenicity, to facilitate global distribution and reduce cold-chain dependence. The data suggests that RBD-SpyVLP provides strong potential to address clinical and logistic challenges of the COVID-19 pandemic.

scholarly journals Comprehensive Deep Mutational Scanning Reveals the Immune-Escaping Hotspots of SARS-CoV-2 Receptor-Binding Domain Targeting Neutralizing Antibodies

2021 ◽  
Vol 12 ◽  
Author(s):  
Keng-Chang Tsai ◽  
Yu-Ching Lee ◽  
Tien-Sheng Tseng
Keyword(s):  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Binding Domain ◽  
Receptor Binding Domain ◽  
Human Immune System ◽  
Angiotensin Converting Enzyme 2 ◽  
Study Results ◽  
Rapid Spread ◽  
Care Systems ◽  
Computational Analyses

The rapid spread of SARS-CoV-2 has caused the COVID-19 pandemic, resulting in the collapse of medical care systems and economic depression worldwide. To combat COVID-19, neutralizing antibodies have been investigated and developed. However, the evolutions (mutations) of the receptor-binding domain (RBD) of SARS-CoV-2 enable escape from neutralization by these antibodies, further impairing recognition by the human immune system. Thus, it is critical to investigate and predict the putative mutations of RBD that escape neutralizing immune responses. Here, we employed computational analyses to comprehensively investigate the mutational effects of RBD on binding to neutralizing antibodies and angiotensin-converting enzyme 2 (ACE2) and demonstrated that the RBD residues K417, L452, L455, F456, E484, G485, F486, F490, Q493, and S494 were consistent with clinically emerging variants or experimental observations of attenuated neutralizations. We also revealed common hotspots, Y449, L455, and Y489, that exerted comparable destabilizing effects on binding to both ACE2 and neutralizing antibodies. Our results provide valuable information on the putative effects of RBD variants on interactions with neutralizing antibodies. These findings provide insights into possible evolutionary hotspots that can escape recognition by these antibodies. In addition, our study results will benefit the development and design of vaccines and antibodies to combat the newly emerging variants of SARS-CoV-2.

scholarly journals Persistence and decay of human antibody responses to the receptor binding domain of SARS-CoV-2 spike protein in COVID-19 patients

2020 ◽  
Vol 5 (52) ◽  
pp. eabe0367 ◽  
Author(s):  
Anita S. Iyer ◽  
Forrest K. Jones ◽  
Ariana Nodoushani ◽  
Meagan Kelly ◽  
Margaret Becker ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Symptom Onset ◽  
Neutralizing Antibodies ◽  
Serum Antibody ◽  
Cross Reactivity ◽  
Binding Domain ◽  
Antibody Responses ◽  
Human Antibody ◽  
Receptor Binding Domain ◽  
Recent Infection

We measured plasma and/or serum antibody responses to the receptor-binding domain (RBD) of the spike (S) protein of SARS-CoV-2 in 343 North American patients infected with SARS-CoV-2 (of which 93% required hospitalization) up to 122 days after symptom onset and compared them to responses in 1548 individuals whose blood samples were obtained prior to the pandemic. After setting seropositivity thresholds for perfect specificity (100%), we estimated sensitivities of 95% for IgG, 90% for IgA, and 81% for IgM for detecting infected individuals between 15 and 28 days after symptom onset. While the median time to seroconversion was nearly 12 days across all three isotypes tested, IgA and IgM antibodies against RBD were short-lived with median times to seroreversion of 71 and 49 days after symptom onset. In contrast, anti-RBD IgG responses decayed slowly through 90 days with only 3 seropositive individuals seroreverting within this time period. IgG antibodies to SARS-CoV-2 RBD were strongly correlated with anti-S neutralizing antibody titers, which demonstrated little to no decrease over 75 days since symptom onset. We observed no cross-reactivity of the SARS-CoV-2 RBD-targeted antibodies with other widely circulating coronaviruses (HKU1, 229 E, OC43, NL63). These data suggest that RBD-targeted antibodies are excellent markers of previous and recent infection, that differential isotype measurements can help distinguish between recent and older infections, and that IgG responses persist over the first few months after infection and are highly correlated with neutralizing antibodies.

Construction and immunogenic studies of a mFc fusion receptor binding domain (RBD) of spike protein as a subunit vaccine against SARS-CoV-2 infection

2020 ◽  
Vol 56 (61) ◽  
pp. 8683-8686 ◽  
Author(s):  
Xiaoxiao Qi ◽  
Bixia Ke ◽  
Qian Feng ◽  
Deying Yang ◽  
Qinghai Lian ◽  
...  
Keyword(s):  
Amino Acid ◽  
Fusion Protein ◽  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Subunit Vaccine ◽  
Binding Domain ◽  
Spike Protein ◽  
Receptor Binding Domain ◽  
Humoral And Cellular Immunity ◽  
A Subunit

Herein, we report that a recombinant fusion protein, containing a 457 amino acid SARS-CoV-2 receptor binding domain and a mouse IgG1 Fc domain, could induce highly potent neutralizing antibodies and stimulate humoral and cellular immunity in mice.

scholarly journals Isolation of a human monoclonal antibody specific for the receptor binding domain of SARS-CoV-2 using a competitive phage biopanning strategy

2020 ◽  
Vol 3 (2) ◽  
pp. 95-100 ◽  
Author(s):  
Xin Zeng ◽  
Lingfang Li ◽  
Jing Lin ◽  
Xinlei Li ◽  
Bin Liu ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Magnetic Beads ◽  
Human Monoclonal Antibody ◽  
Binding Domain ◽  
Receptor Binding Domain ◽  
Antibody Library ◽  
Synthetic Antibody ◽  
Blocking Antibodies

Abstract The infection of the novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused more than 200 000 deaths, but no vaccine or therapeutic monoclonal antibody is currently available. 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. High-affinity antibodies were enriched after the first round using a standard panning process in which RBD-His was immobilized as a bait. At the next two rounds, immobilized ACE2-Fc and free RBD-His were mixed with the enriched phage antibodies. Antibodies binding to RBD at epitopes different from ACE2-binding site were captured by the immobilized ACE2-Fc, forming a “sandwich” complex. Only antibodies competed with ACE2 can bind to the free RBD-His in the supernatant and be subsequently separated by the nickel-nitrilotriacetic acid magnetic beads. rRBD-15 from the competitive biopanning of our synthetic antibody library, Lib AB1, was produced as the full-length IgG1 format. It was proved to competitively block the binding of RBD to ACE2 and potently inhibit SARS-CoV-2 pseudovirus infection with IC50 values of 12 nM. Nevertheless, rRBD-16 from the standard biopanning can only bind to RBD in vitro, but not have the blocking or neutralization activity. Our strategy can efficiently isolate the blocking antibodies of RBD, and it would speed up the discovery of neutralizing antibodies against SARS-CoV-2.

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