scholarly journals Prime-boost protein subunit vaccines against SARS-CoV-2 are highly immunogenic in mice and macaques

2020 ◽  
Author(s):  
Hyon-Xhi Tan ◽  
Jennifer A Juno ◽  
Wen Shi Lee ◽  
Isaac Barber-Axthelm ◽  
Hannah G Kelly ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Receptor Binding ◽  
Cell Activity ◽  
Receptor Binding Domain ◽  
Protein Subunit ◽  
Neutralising Antibodies ◽  
Subunit Vaccines ◽  
Vaccine Candidates ◽  
Follicular Helper ◽  
T Follicular Helper Cell

SummarySARS-CoV-2 vaccines are advancing into human clinical trials, with emphasis on eliciting high titres of neutralising antibodies against the viral spike (S). However, the merits of broadly targeting S versus focusing antibody onto the smaller receptor binding domain (RBD) are unclear. Here we assessed prototypic S and RBD subunit vaccines in homologous or heterologous prime-boost regimens in mice and non-human primates. We find S is highly immunogenic in mice, while the comparatively poor immunogenicity of RBD was associated with limiting germinal centre and T follicular helper cell activity. Boosting S-primed mice with either S or RBD significantly augmented neutralising titres, with RBD-focussing driving moderate improvement in serum neutralisation. In contrast, both S and RBD vaccines were comparably immunogenic in macaques, eliciting serological neutralising activity that generally exceed levels in convalescent humans. These studies confirm recombinant S proteins as promising vaccine candidates and highlight multiple pathways to achieving potent serological neutralisation.

scholarly journals Immunogenicity of prime-boost protein subunit vaccine strategies against SARS-CoV-2 in mice and macaques

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hyon-Xhi Tan ◽  
Jennifer A. Juno ◽  
Wen Shi Lee ◽  
Isaac Barber-Axthelm ◽  
Hannah G. Kelly ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Subunit Vaccine ◽  
Cell Activity ◽  
Receptor Binding Domain ◽  
Protein Subunit ◽  
Neutralising Antibodies ◽  
Subunit Vaccines ◽  
Vaccine Candidates ◽  
Follicular Helper ◽  
T Follicular Helper Cell

AbstractSARS-CoV-2 vaccines are advancing into human clinical trials, with emphasis on eliciting high titres of neutralising antibodies against the viral spike (S). However, the merits of broadly targeting S versus focusing antibody onto the smaller receptor binding domain (RBD) are unclear. Here we assess prototypic S and RBD subunit vaccines in homologous or heterologous prime-boost regimens in mice and non-human primates. We find S is highly immunogenic in mice, while the comparatively poor immunogenicity of RBD is associated with limiting germinal centre and T follicular helper cell activity. Boosting S-primed mice with either S or RBD significantly augments neutralising titres, with RBD-focussing driving moderate improvement in serum neutralisation. In contrast, both S and RBD vaccines are comparably immunogenic in macaques, eliciting serological neutralising activity that generally exceed levels in convalescent humans. These studies confirm recombinant S proteins as promising vaccine candidates and highlight multiple pathways to achieving potent serological neutralisation.

scholarly journals COVID-19: Insights into Potential Vaccines

2021 ◽  
Vol 9 (3) ◽  
pp. 605
Author(s):  
Ke-Yan Loo ◽  
Vengadesh Letchumanan ◽  
Hooi-Leng Ser ◽  
Siew Li Teoh ◽  
Jodi Woan-Fei Law ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Viral Vector ◽  
Phase Iii ◽  
Effective Vaccine ◽  
Pharmaceutical Companies ◽  
Protein Subunit ◽  
Subunit Vaccines ◽  
Vaccine Candidates ◽  
Phase Iii Clinical Trials ◽  
Positive Results

People around the world ushered in the new year 2021 with a fear of COVID-19, as family members have lost their loved ones to the disease. Millions of people have been infected, and the livelihood of many has been jeopardized due to the pandemic. Pharmaceutical companies are racing against time to develop an effective vaccine to protect against COVID-19. Researchers have developed various types of candidate vaccines with the release of the genetic sequence of the SARS-CoV-2 virus in January. These include inactivated viral vaccines, protein subunit vaccines, mRNA vaccines, and recombinant viral vector vaccines. To date, several vaccines have been authorized for emergency use and they have been administered in countries across the globe. Meanwhile, there are also vaccine candidates in Phase III clinical trials awaiting results and approval from authorities. These candidates have shown positive results in the previous stages of the trials, whereby they could induce an immune response with minimal side effects in the participants. This review aims to discuss the different vaccine platforms and the clinical trials of the candidate vaccines.

scholarly journals SARS-CoV-2 B.1.617 emergence and sensitivity to vaccine-elicited antibodies

2021 ◽  
Author(s):  
Isabella Ferreira ◽  
Rawlings Datir ◽  
Guido Papa ◽  
Steven Kemp ◽  
Bo Meng ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Growth Rates ◽  
Cleavage Site ◽  
Syncytium Formation ◽  
Binding Domain ◽  
Spike Protein ◽  
Receptor Binding Domain ◽  
Additive Effects ◽  
Neutralising Antibodies ◽  
Indian State

The B.1.617 variant emerged in the Indian state of Maharashtra in late 2020 and has spread throughout India and to at least 40 countries. There have been fears that two key mutations seen in the receptor binding domain L452R and E484Q would have additive effects on evasion of neutralising antibodies. Here we delineate the phylogenetics of B.1.617 and spike mutation frequencies, in the context of others bearing L452R. The defining mutations in B.1.617.1 spike are L452R and E484Q in the RBD that interacts with ACE2 and is the target of neutralising antibodies. All B.1.617 viruses have the P681R mutation in the polybasic cleavage site region in spike. We report that B.1.617.1 spike bearing L452R, E484Q and P681R mediates entry into cells with slightly reduced efficiency compared to Wuhan-1. This spike confers modestly reduced sensitivity to BNT162b2 mRNA vaccine-elicited antibodies that is similar in magnitude to the loss of sensitivity conferred by L452R or E484Q alone. Furthermore we show that the P681R mutation significantly augments syncytium formation upon the B.1.617.1 spike protein, potentially contributing to increased pathogenesis observed in hamsters and infection growth rates observed in humans.

scholarly journals Yeast-expressed Recombinant SARS-CoV-2 Receptor Binding Domain, RBD203-N1 as a COVID-19 Protein Vaccine Candidate

2021 ◽  
Author(s):  
Wen-Hsiang Chen ◽  
Jeroen Pollet ◽  
Ulrich Strych ◽  
Jungsoon Lee ◽  
Zhuyun Liu ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Vaccine Candidate ◽  
Total Yield ◽  
Development Program ◽  
Exchange Chromatography ◽  
Binding Domain ◽  
Receptor Binding Domain ◽  
Protein Vaccine ◽  
Protein Subunit

Background: SARS-CoV-2 protein subunit vaccines are being evaluated by multiple manufacturers to fill the need for low-cost, easy to scale, safe, and effective COVID-19 vaccines for global access. Vaccine candidates relying on the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein have been the focus of our development program. In this paper, we report on the generation of the RBD203-N1 yeast expression construct, which produces a recombinant protein that when formulated with alum and the TLR-9 agonist, CpG1826 elicits a robust immune response and protection in mice. Method: The RBD203-N1 antigen was expressed in the yeast Pichia pastoris X33. After fermentation at the 5 L scale, the protein was purified by hydrophobic interaction chromatography followed by anion exchange chromatography. The purified protein was characterized biophysically and biochemically, and after its formulation, the immunogenicity and efficacy were evaluated in mice. Results, Conclusions, and Significance: The RBD203-N1 production process yielded 492.9 ± 3.0 mg/L of protein in the fermentation supernatant. A two-step purification process produced a >96% pure protein with a recovery rate of 55 ± 3% (total yield of purified protein: 270.5 ± 13.2 mg/L fermentation supernatant). The protein was characterized as a homogeneous monomer with well-defined secondary structure, thermally stable, antigenic, and when adjuvanted on alum and CpG, it was immunogenic and induced robust levels of neutralizing antibodies against SARS-CoV-2 pseudovirus. These characteristics show that this vaccine candidate is well suited for technology transfer with feasibility of its transition into the clinic to evaluate its immunogenicity and safety in humans.

scholarly journals Targeting SARS-CoV-2 receptor-binding domain to cells expressing CD40 improves protection to infection in convalescent macaques

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Romain Marlin ◽  
Veronique Godot ◽  
Sylvain Cardinaud ◽  
Mathilde Galhaut ◽  
Severin Coleon ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Viral Vector ◽  
Binding Domain ◽  
Long Term Memory ◽  
High Dose ◽  
Receptor Binding Domain ◽  
Humanized Mouse Model ◽  
Subunit Vaccines ◽  
Antigen Presenting

AbstractAchieving sufficient worldwide vaccination coverage against SARS-CoV-2 will require additional approaches to currently approved viral vector and mRNA vaccines. Subunit vaccines may have distinct advantages when immunizing vulnerable individuals, children and pregnant women. Here, we present a new generation of subunit vaccines targeting viral antigens to CD40-expressing antigen-presenting cells. We demonstrate that targeting the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein to CD40 (αCD40.RBD) induces significant levels of specific T and B cells, with long-term memory phenotypes, in a humanized mouse model. Additionally, we demonstrate that a single dose of the αCD40.RBD vaccine, injected without adjuvant, is sufficient to boost a rapid increase in neutralizing antibodies in convalescent non-human primates (NHPs) exposed six months previously to SARS-CoV-2. Vaccine-elicited antibodies cross-neutralize different SARS-CoV-2 variants, including D614G, B1.1.7 and to a lesser extent B1.351. Such vaccination significantly improves protection against a new high-dose virulent challenge versus that in non-vaccinated convalescent animals.

scholarly journals SARS-CoV-2 preS dTM vaccine booster candidates increase functional antibody responses and cross-neutralization against SARS-CoV-2 variants of concern in non-human primates

2021 ◽  
Author(s):  
Vincent Pavot ◽  
Catherine Berry ◽  
Michael Kishko ◽  
Natalie Anosova ◽  
Dean Huang ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Neutralizing Antibodies ◽  
Neutralizing Antibody ◽  
Antibody Responses ◽  
Protein Vaccine ◽  
Preclinical Models ◽  
Protein Subunit ◽  
Vaccine Candidates ◽  
Vaccine Booster ◽  
Cross Neutralization

Abstract The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants that partly evade neutralizing antibodies has raised concerns of reduced vaccine effectiveness and increased infection. We previously demonstrated in preclinical models and in human clinical trials that our SARS-CoV-2 recombinant spike protein vaccine adjuvanted with AS03 (CoV2 preS dTM-AS03) elicits robust neutralizing antibody responses in naïve subjects. Here, the objective was to document the potency of various booster vaccine formulations in macaques previously vaccinated with mRNA or protein subunit vaccine candidates. We show that one booster dose of AS03-adjuvanted CoV2 preS dTM, D614 (parental) or B.1.351 (Beta), in monovalent or bivalent (D614 + B.1.351) formulations, significantly boosted pre-existing neutralizing antibodies and elicited high and stable cross-neutralizing antibodies covering the four known SARS-CoV-2 variants of concern (Alpha, Beta, Gamma and Delta) and, unexpectedly, SARS-CoV-1, in primed macaques. Interestingly, the non-adjuvanted CoV2 preS dTM B.1.351 vaccine formulation also significantly boosted and broadened the neutralizing antibody responses. Our findings show that these vaccine candidates used as a booster have the potential to offer cross-protection against a broad spectrum of variants. This has important implications for vaccine control of SARS-CoV-2 variants of concern and informs on the benefit of a booster with our vaccine candidates currently under evaluation in phase 2 and 3 clinical trials (NCT04762680 and NCT04904549).

scholarly journals Decline of humoral responses against SARS-CoV-2 Spike in convalescent individuals

2020 ◽  
Author(s):  
Guillaume Beaudoin-Bussières ◽  
Annemarie Laumaea ◽  
Sai Priya Anand ◽  
Jérémie Prévost ◽  
Romain Gasser ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
Receptor Binding Domain ◽  
Wild Type ◽  
Positive Role ◽  
Neutralization Activity ◽  
Specific Igg ◽  
Humoral Responses ◽  
Over Time

ABSTRACTIn the absence of effective vaccines and with limited therapeutic options, convalescent plasma is being collected across the globe for potential transfusion to COVID-19 patients. The therapy has been deemed safe and several clinical trials assessing its efficacy are ongoing. While it remains to be formally proven, the presence of neutralizing antibodies is thought to play a positive role in the efficacy of this treatment. Indeed, neutralizing titers of ≥1:160 have been recommended in some convalescent plasma trials for inclusion. Here we performed repeated analyses at one-month interval on 31 convalescent individuals to evaluate how the humoral responses against the SARS-CoV-2 Spike, including neutralization, evolve over time. We observed that receptor-binding domain (RBD)-specific IgG slightly decreased between six and ten weeks after symptoms onset but RBD-specific IgM decreased much more abruptly. Similarly, we observed a significant decrease in the capacity of convalescent plasma to neutralize pseudoparticles bearing SARS-CoV-2 S wild-type or its D614G variant. If neutralization activity proves to be an important factor in the clinical efficacy of convalescent plasma transfer, our results suggest that plasma from convalescent donors should be recovered rapidly after symptoms resolution.

scholarly journals Targeting SARS-CoV-2 receptor-binding domain to cells expressing CD40 improves protection to infection in convalescent macaques

2021 ◽  
Author(s):  
Romain Marlin ◽  
Véronique Godot ◽  
Sylvain Cardinaud ◽  
Mathilde Galhaut ◽  
Severin Coleon ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Neutralizing Antibodies ◽  
High Efficiency ◽  
Viral Vector ◽  
Binding Domain ◽  
Long Term Memory ◽  
High Dose ◽  
Human Populations ◽  
Receptor Binding Domain ◽  
Subunit Vaccines

Abstract Controlling the circulation of the recently emerged SARS-CoV-2 in the human populations requires massive vaccination campaigns. Achieving sufficient worldwide vaccination coverage will require additional approaches to first generation of approved viral vector and mRNA vaccines. Subunit vaccines have excellent safety and efficacy records and may have distinct advantages, in particular when immunizing individuals with vulnerabilities or when considering the vaccination of children and pregnant women.. We have developed a new generation of subunit vaccines with enhanced immunogenicity by the targeting of viral antigens to CD40-expressing antigen-presenting cells, thus harnessing their intrinsic immune-stimulant properties. Here, we demonstrate that targeting the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein to CD40 (αCD40.RBD) induces significant levels of specific T and B cells, with a long-term memory phenotype, in a humanized mouse model. In addition, we demonstrate that a single dose of the αCD40.RBD vaccine, injected without adjuvant, is sufficient to boost a rapid increase in neutralizing antibodies in convalescent non-human primates (NHPs) exposed six months previously to SARS-CoV-2. Such vaccination thus significantly improved protection against a new high-dose virulent challenge versus that in non-vaccinated convalescent animals. Viral dynamics modelling showed the high efficiency of the vaccine at controlling the viral dissemination.

scholarly journals 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

2016 ◽  
Vol 91 (1) ◽  
Author(s):  
Wanbo Tai ◽  
Yufei Wang ◽  
Craig A. Fett ◽  
Guangyu Zhao ◽  
Fang Li ◽  
...  
Keyword(s):  
Middle East ◽  
Receptor Binding ◽  
Broad Spectrum ◽  
Neutralizing Antibodies ◽  
Middle East Respiratory Syndrome ◽  
Receptor Binding Domain ◽  
Vaccine Candidates ◽  
Vaccine Target ◽  
Protein Receptor ◽  
Escape Mutants

ABSTRACT Middle East respiratory syndrome coronavirus (MERS-CoV) binds to cellular receptor dipeptidyl peptidase 4 (DPP4) via the spike (S) protein receptor-binding domain (RBD). The RBD contains critical neutralizing epitopes and serves as an important vaccine target. Since RBD mutations occur in different MERS-CoV isolates and antibody escape mutants, cross-neutralization of divergent MERS-CoV strains by RBD-induced antibodies remains unknown. Here, we constructed four recombinant RBD (rRBD) proteins with single or multiple mutations detected in representative human MERS-CoV strains from the 2012, 2013, 2014, and 2015 outbreaks, respectively, and one rRBD protein with multiple changes derived from camel MERS-CoV strains. Like the RBD of prototype EMC2012 (EMC-RBD), all five RBDs maintained good antigenicity and functionality, the ability to bind RBD-specific neutralizing monoclonal antibodies (MAbs) and the DPP4 receptor, and high immunogenicity, able to elicit S-specific antibodies. They induced potent neutralizing antibodies cross-neutralizing 17 MERS pseudoviruses expressing S proteins of representative human and camel MERS-CoV strains identified during the 2012-2015 outbreaks, 5 MAb escape MERS-CoV mutants, and 2 live human MERS-CoV strains. We then constructed two RBDs mutated in multiple key residues in the receptor-binding motif (RBM) of RBD and demonstrated their strong cross-reactivity with anti-EMC-RBD antibodies. These RBD mutants with diminished DPP4 binding also led to virus attenuation, suggesting that immunoevasion after RBD immunization is accompanied by loss of viral fitness. Therefore, this study demonstrates that MERS-CoV RBD is an important vaccine target able to induce highly potent and broad-spectrum neutralizing antibodies against infection by divergent circulating human and camel MERS-CoV strains. IMPORTANCE MERS-CoV was first identified in June 2012 and has since spread in humans and camels. Mutations in its spike (S) protein receptor-binding domain (RBD), a key vaccine target, have been identified, raising concerns over the efficacy of RBD-based MERS vaccines against circulating human and camel MERS-CoV strains. Here, we constructed five vaccine candidates, designated 2012-RBD, 2013-RBD, 2014-RBD, 2015-RBD, and Camel-RBD, containing single or multiple mutations in the RBD of representative human and camel MERS-CoV strains during the 2012-2015 outbreaks. These RBD-based vaccine candidates maintained good functionality, antigenicity, and immunogenicity, and they induced strong cross-neutralizing antibodies against infection by divergent pseudotyped and live MERS-CoV strains, as well as antibody escape MERS-CoV mutants. This study provides impetus for further development of a safe, highly effective, and broad-spectrum RBD-based subunit vaccine to prevent MERS-CoV infection.

scholarly journals Single-component, self-assembling, protein nanoparticles presenting the receptor binding domain and stabilized spike as SARS-CoV-2 vaccine candidates

2021 ◽  
Vol 7 (12) ◽  
pp. eabf1591
Author(s):  
Linling He ◽  
Xiaohe Lin ◽  
Ying Wang ◽  
Ciril Abraham ◽  
Cindy Sou ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Vaccine Candidate ◽  
Neutralizing Antibody ◽  
Binding Domain ◽  
Heptad Repeat ◽  
Receptor Binding Domain ◽  
Vaccine Candidates ◽  
Self Assembling ◽  
Cell Immunity ◽  
Promising Vaccine Candidate

Vaccination against SARS-CoV-2 provides an effective tool to combat the COVID-19 pandemic. Here, we combined antigen optimization and nanoparticle display to develop vaccine candidates for SARS-CoV-2. We first displayed the receptor-binding domain (RBD) on three self-assembling protein nanoparticle (SApNP) platforms using the SpyTag/SpyCatcher system. We then identified heptad repeat 2 (HR2) in S2 as the cause of spike metastability, designed an HR2-deleted glycine-capped spike (S2GΔHR2), and displayed S2GΔHR2 on SApNPs. An antibody column specific for the RBD enabled tag-free vaccine purification. In mice, the 24-meric RBD-ferritin SApNP elicited a more potent neutralizing antibody (NAb) response than the RBD alone and the spike with two stabilizing proline mutations in S2 (S2P). S2GΔHR2 elicited twofold higher NAb titers than S2P, while S2GΔHR2 SApNPs derived from multilayered E2p and I3-01v9 60-mers elicited up to 10-fold higher NAb titers. The S2GΔHR2-presenting I3-01v9 SApNP also induced critically needed T cell immunity, thereby providing a promising vaccine candidate.

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