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1.
Proc Natl Acad Sci U S A ; 119(31): e2205412119, 2022 Aug 02.
Article in English | MEDLINE | ID: covidwho-1947766

ABSTRACT

Camelid single-domain antibodies, also known as nanobodies, can be readily isolated from naïve libraries for specific targets but often bind too weakly to their targets to be immediately useful. Laboratory-based genetic engineering methods to enhance their affinity, termed maturation, can deliver useful reagents for different areas of biology and potentially medicine. Using the receptor binding domain (RBD) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein and a naïve library, we generated closely related nanobodies with micromolar to nanomolar binding affinities. By analyzing the structure-activity relationship using X-ray crystallography, cryoelectron microscopy, and biophysical methods, we observed that higher conformational entropy losses in the formation of the spike protein-nanobody complex are associated with tighter binding. To investigate this, we generated structural ensembles of the different complexes from electron microscopy maps and correlated the conformational fluctuations with binding affinity. This insight guided the engineering of a nanobody with improved affinity for the spike protein.


Subject(s)
Antibodies, Neutralizing , Antibodies, Viral , Antibody Affinity , SARS-CoV-2 , Single-Domain Antibodies , Spike Glycoprotein, Coronavirus , Antibodies, Neutralizing/chemistry , Antibodies, Neutralizing/genetics , Antibodies, Viral/chemistry , Antibodies, Viral/genetics , Antibody Affinity/genetics , Cryoelectron Microscopy , Entropy , Genetic Engineering , Humans , Protein Binding , Protein Domains , SARS-CoV-2/immunology , Single-Domain Antibodies/chemistry , Single-Domain Antibodies/genetics , Spike Glycoprotein, Coronavirus/immunology
2.
Commun Biol ; 5(1): 669, 2022 Jul 06.
Article in English | MEDLINE | ID: covidwho-1921727

ABSTRACT

We are amid the historic coronavirus infectious disease 2019 (COVID-19) pandemic. Imbalances in the accessibility of vaccines, medicines, and diagnostics among countries, regions, and populations, and those in war crises, have been problematic. Nanobodies are small, stable, customizable, and inexpensive to produce. Herein, we present a panel of nanobodies that can detect the spike proteins of five SARS-CoV-2 variants of concern (VOCs) including Omicron. Here we show via ELISA, lateral flow, kinetic, flow cytometric, microscopy, and Western blotting assays that our nanobodies can quantify the spike variants. This panel of nanobodies broadly neutralizes viral infection caused by pseudotyped and authentic SARS-CoV-2 VOCs. Structural analyses show that the P86 clone targets epitopes that are conserved yet unclassified on the receptor-binding domain (RBD) and contacts the N-terminal domain (NTD). Human antibodies rarely access both regions; consequently, the clone buries hidden crevasses of SARS-CoV-2 spike proteins that go undetected by conventional antibodies.


Subject(s)
COVID-19 , Single-Domain Antibodies , Antibodies, Viral , Humans , Membrane Glycoproteins/metabolism , Neutralization Tests , SARS-CoV-2/genetics , Single-Domain Antibodies/genetics , Spike Glycoprotein, Coronavirus/genetics , Viral Envelope Proteins/metabolism
3.
Sheng Wu Gong Cheng Xue Bao ; 38(6): 2250-2258, 2022 Jun 25.
Article in Chinese | MEDLINE | ID: covidwho-1912218

ABSTRACT

Nanobodies derived from camelid single-chain antibodies have the advantages of being small, simple, highly soluble and stable. Nanobodies can be administered by inhalation and therefore is potentially valuable for the prevention and control of respiratory viruses. Trichoderma reesei is a food-grade protein expression host with a cellulase production capacity of up to 80 g/L, which can be employed for low-cost production of therapeutic proteins. In this study, a codon-optimized SARS-CoV-2 neutralizing nanobody Nb20 was expressed in T. reesei under a strong constitutive promoter Pcdna1. Nb20 protein was fused downstream of the N-terminal fragment of cellobiohydrolase Ⅰ, and the fusion protein can be intracellularly cleaved by the KEX2 protease to release Nb20. In a shake-flask fermentation using glucose medium, 47.4 mg/L Nb20 was detected in the culture after 48 h of cultivation. The expressed Nb20 showed the ability to interact with the receptor-binding domain of SARS-CoV-2 spike protein, suggesting that it can be used for the neutralization of SARS-CoV-2. The results indicate that T. reesei has the potential for recombinant production of nanobodies.


Subject(s)
COVID-19 , Single-Domain Antibodies , Humans , Hypocreales , SARS-CoV-2/genetics , Single-Domain Antibodies/genetics , Spike Glycoprotein, Coronavirus
4.
Structure ; 30(5): 707-720.e5, 2022 05 05.
Article in English | MEDLINE | ID: covidwho-1829569

ABSTRACT

Because of the evolutionary variants of SARS-CoV-2, development of broad-spectrum neutralizing antibodies resilient to virus escape is urgently needed. We identified a group of high-affinity nanobodies from camels immunized with receptor-binding domain (RBD) of SARS-CoV-2 spike protein and resolved the structures of two non-competing nanobodies (NB1A7 and NB1B11) in complex with RBD using X-ray crystallography. The structures show that NB1A7 targets the highly conserved cryptic epitope shared by SARS-CoV-2 variants and some other coronaviruses and blocks ACE2 receptor attachment of the spike protein, and NB1B11 epitope overlaps with the contacting surface of ACE2 and is different from the binding site of NB1A7. These two nanobodies were covalently linked into multivalent and bi-paratopic formats, which significantly improved the avidity and neutralization potency and may further inhibit viral escape. The results contribute to the structure-guided design of antibodies against future variants of SARS-CoV-2 virus to combat coronavirus epidemics and pandemics.


Subject(s)
COVID-19 , Single-Domain Antibodies , Angiotensin-Converting Enzyme 2 , Antibodies, Neutralizing , Broadly Neutralizing Antibodies , Epitopes/metabolism , Humans , Protein Binding , SARS-CoV-2/genetics , Single-Domain Antibodies/chemistry , Single-Domain Antibodies/genetics , Spike Glycoprotein, Coronavirus/chemistry
5.
Proc Natl Acad Sci U S A ; 119(18): e2201433119, 2022 05 03.
Article in English | MEDLINE | ID: covidwho-1815698

ABSTRACT

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike is a trimer of S1/S2 heterodimers with three receptor-binding domains (RBDs) at the S1 subunit for human angiotensin-converting enzyme 2 (hACE2). Due to their small size, nanobodies can recognize protein cavities that are not accessible to conventional antibodies. To isolate high-affinity nanobodies, large libraries with great diversity are highly desirable. Dromedary camels (Camelus dromedarius) are natural reservoirs of coronaviruses like Middle East respiratory syndrome CoV (MERS-CoV) that are transmitted to humans. Here, we built large dromedary camel VHH phage libraries to isolate nanobodies that broadly neutralize SARS-CoV-2 variants. We isolated two VHH nanobodies, NCI-CoV-7A3 (7A3) and NCI-CoV-8A2 (8A2), which have a high affinity for the RBD via targeting nonoverlapping epitopes and show broad neutralization activity against SARS-CoV-2 and its emerging variants of concern. Cryoelectron microscopy (cryo-EM) complex structures revealed that 8A2 binds the RBD in its up mode with a long CDR3 loop directly involved in the ACE2 binding residues and that 7A3 targets a deeply buried region that uniquely extends from the S1 subunit to the apex of the S2 subunit regardless of the conformational state of the RBD. At a dose of ≥5 mg/kg, 7A3 efficiently protected transgenic mice expressing hACE2 from the lethal challenge of variants B.1.351 or B.1.617.2, suggesting its therapeutic use against COVID-19 variants. The dromedary camel VHH phage libraries could be helpful as a unique platform ready for quickly isolating potent nanobodies against future emerging viruses.


Subject(s)
COVID-19 , Single-Domain Antibodies , Animals , Camelus , Humans , Mice , SARS-CoV-2/genetics , Single-Domain Antibodies/genetics
6.
Front Immunol ; 13: 822159, 2022.
Article in English | MEDLINE | ID: covidwho-1742216

ABSTRACT

Virus-neutralizing antibodies are one of the few treatment options for COVID-19. The evolution of SARS-CoV-2 virus has led to the emergence of virus variants with reduced sensitivity to some antibody-based therapies. The development of potent antibodies with a broad spectrum of neutralizing activity is urgently needed. Here we isolated a panel of single-domain antibodies that specifically bind to the receptor-binding domain of SARS-CoV-2 S glycoprotein. Three of the selected antibodies exhibiting most robust neutralization potency were used to generate dimeric molecules. We observed that these modifications resulted in up to a 200-fold increase in neutralizing activity. The most potent heterodimeric molecule efficiently neutralized each of SARS-CoV-2 variant of concern, including Alpha, Beta, Gamma, Delta and Omicron variants. This heterodimeric molecule could be a promising drug candidate for a treatment for COVID-19 caused by virus variants of concern.


Subject(s)
Antibodies, Neutralizing/metabolism , Antibodies, Viral/metabolism , COVID-19/immunology , SARS-CoV-2/physiology , Single-Domain Antibodies/metabolism , Epitopes/immunology , Humans , Neutralization Tests , Single-Domain Antibodies/genetics , Spike Glycoprotein, Coronavirus/immunology
7.
EMBO Rep ; 23(4): e54199, 2022 04 05.
Article in English | MEDLINE | ID: covidwho-1732510

ABSTRACT

The ongoing COVID-19 pandemic represents an unprecedented global health crisis. Here, we report the identification of a synthetic nanobody (sybody) pair, Sb#15 and Sb#68, that can bind simultaneously to the SARS-CoV-2 spike RBD and efficiently neutralize pseudotyped and live viruses by interfering with ACE2 interaction. Cryo-EM confirms that Sb#15 and Sb#68 engage two spatially discrete epitopes, influencing rational design of bispecific and tri-bispecific fusion constructs that exhibit up to 100- and 1,000-fold increase in neutralization potency, respectively. Cryo-EM of the sybody-spike complex additionally reveals a novel up-out RBD conformation. While resistant viruses emerge rapidly in the presence of single binders, no escape variants are observed in the presence of the bispecific sybody. The multivalent bispecific constructs further increase the neutralization potency against globally circulating SARS-CoV-2 variants of concern. Our study illustrates the power of multivalency and biparatopic nanobody fusions for the potential development of therapeutic strategies that mitigate the emergence of new SARS-CoV-2 escape mutants.


Subject(s)
COVID-19 , Single-Domain Antibodies , Antibodies, Neutralizing , Antibodies, Viral/metabolism , COVID-19/drug therapy , Drug Resistance , Humans , Pandemics , Protein Binding , SARS-CoV-2/genetics , Single-Domain Antibodies/genetics , Single-Domain Antibodies/metabolism , Single-Domain Antibodies/pharmacology , Spike Glycoprotein, Coronavirus/genetics , Spike Glycoprotein, Coronavirus/metabolism
8.
Int J Mol Sci ; 23(6)2022 Mar 08.
Article in English | MEDLINE | ID: covidwho-1732071

ABSTRACT

Nanobodies provide important advantages over traditional antibodies, including their smaller size and robust biochemical properties such as high thermal stability, high solubility, and the ability to be bioengineered into novel multivalent, multi-specific, and high-affinity molecules, making them a class of emerging powerful therapies against SARS-CoV-2. Recent research efforts on the design, protein engineering, and structure-functional characterization of nanobodies and their binding with SARS-CoV-2 S proteins reflected a growing realization that nanobody combinations can exploit distinct binding epitopes and leverage the intrinsic plasticity of the conformational landscape for the SARS-CoV-2 S protein to produce efficient neutralizing and mutation resistant characteristics. Structural and computational studies have also been instrumental in quantifying the structure, dynamics, and energetics of the SARS-CoV-2 spike protein binding with nanobodies. In this review, a comprehensive analysis of the current structural, biophysical, and computational biology investigations of SARS-CoV-2 S proteins and their complexes with distinct classes of nanobodies targeting different binding sites is presented. The analysis of computational studies is supplemented by an in-depth examination of mutational scanning simulations and identification of binding energy hotspots for distinct nanobody classes. The review is focused on the analysis of mechanisms underlying synergistic binding of multivalent nanobodies that can be superior to single nanobodies and conventional nanobody cocktails in combating escape mutations by effectively leveraging binding avidity and allosteric cooperativity. We discuss how structural insights and protein engineering approaches together with computational biology tools can aid in the rational design of synergistic combinations that exhibit superior binding and neutralization characteristics owing to avidity-mediated mechanisms.


Subject(s)
Binding Sites , Molecular Docking Simulation , Molecular Dynamics Simulation , Single-Domain Antibodies/chemistry , Spike Glycoprotein, Coronavirus/chemistry , Amino Acids , Antibody Affinity , Epitopes/chemistry , Epitopes/metabolism , Humans , Multiprotein Complexes/chemistry , Mutagenesis , Protein Binding , Protein Engineering , Protein Interaction Domains and Motifs , Single-Domain Antibodies/genetics , Single-Domain Antibodies/metabolism , Spike Glycoprotein, Coronavirus/genetics , Spike Glycoprotein, Coronavirus/metabolism
9.
J Virol ; 96(4): e0162221, 2022 02 23.
Article in English | MEDLINE | ID: covidwho-1706888

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can induce mild to life-threatening symptoms. Especially individuals over 60 years of age or with underlying comorbidities, including heart or lung disease and diabetes, or immunocompromised patients are at a higher risk. Fatal multiorgan damage in coronavirus disease 2019 (COVID-19) patients can be attributed to an interleukin-6 (IL-6)-dominated cytokine storm. Consequently, IL-6 receptor (IL-6R) monoclonal antibody treatment for severe COVID-19 cases has been approved for therapy. High concentrations of soluble IL-6R (sIL-6R) were found in COVID-19 intensive care unit patients, suggesting the involvement of IL-6 trans-signaling in disease pathology. Here, in analogy to bispecific antibodies (bsAbs), we developed the first bispecific IL-6 trans-signaling inhibitor, c19s130Fc, which blocks viral infection and IL-6 trans-signaling. c19s130Fc is a designer protein of the IL-6 trans-signaling inhibitor cs130 fused to a single-domain nanobody directed against the receptor binding domain (RBD) of the SARS-CoV-2 spike protein. c19s130Fc binds with high affinity to IL-6:sIL-6R complexes as well as the spike protein of SARS-CoV-2, as shown by surface plasmon resonance. Using cell-based assays, we demonstrate that c19s130Fc blocks IL-6 trans-signaling-induced proliferation and STAT3 phosphorylation in Ba/F3-gp130 cells as well as SARS-CoV-2 infection and STAT3 phosphorylation in Vero cells. Taken together, c19s130Fc represents a new class of bispecific inhibitors consisting of a soluble cytokine receptor fused to antiviral nanobodies and principally demonstrates the multifunctionalization of trans-signaling inhibitors. IMPORTANCE The availability of effective SARS-CoV-2 vaccines is a large step forward in managing the pandemic situation. In addition, therapeutic options, e.g., monoclonal antibodies to prevent viral cell entry and anti-inflammatory therapies, including glucocorticoid treatment, are currently developed or in clinical use to treat already infected patients. Here, we report a novel dual-specificity inhibitor to simultaneously target SARS-CoV-2 infection and virus-induced hyperinflammation. This was achieved by fusing an inhibitor of viral cell entry with a molecule blocking IL-6, a key mediator of SARS-CoV-2-induced hyperinflammation. Through this dual action, this molecule may have the potential to efficiently ameliorate symptoms of COVID-19 in infected individuals.


Subject(s)
COVID-19 , Cytokine Receptor gp130 , Interleukin-6/metabolism , Recombinant Fusion Proteins , Signal Transduction/drug effects , Single-Domain Antibodies , Spike Glycoprotein, Coronavirus/metabolism , Animals , COVID-19/drug therapy , COVID-19/metabolism , Chlorocebus aethiops , Cytokine Receptor gp130/chemistry , Cytokine Receptor gp130/genetics , Humans , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/pharmacology , Single-Domain Antibodies/chemistry , Single-Domain Antibodies/genetics , Single-Domain Antibodies/pharmacology , Vero Cells
10.
Signal Transduct Target Ther ; 7(1): 44, 2022 02 09.
Article in English | MEDLINE | ID: covidwho-1683982

ABSTRACT

The wide transmission and host adaptation of SARS-CoV-2 have led to the rapid accumulation of mutations, posing significant challenges to the effectiveness of vaccines and therapeutic antibodies. Although several neutralizing antibodies were authorized for emergency clinical use, convalescent patients derived natural antibodies are vulnerable to SARS-CoV-2 Spike mutation. Here, we describe the screen of a panel of SARS-CoV-2 receptor-binding domain (RBD) targeted nanobodies (Nbs) from a synthetic library and the design of a biparatopic Nb, named Nb1-Nb2, with tight affinity and super-wide neutralization breadth against multiple SARS-CoV-2 variants of concern. Deep-mutational scanning experiments identify the potential binding epitopes of the Nbs on the RBD and demonstrate that biparatopic Nb1-Nb2 has a strong escape-resistant feature against more than 60 tested RBD amino acid substitutions. Using pseudovirion-based and trans-complementation SARS-CoV-2 tools, we determine that the Nb1-Nb2 broadly neutralizes multiple SARS-CoV-2 variants at sub-nanomolar levels, including Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), Lambda (C.37), Kappa (B.1.617.1), and Mu (B.1.621). Furthermore, a heavy-chain antibody is constructed by fusing the human IgG1 Fc to Nb1-Nb2 (designated as Nb1-Nb2-Fc) to improve its neutralization potency, yield, stability, and potential half-life extension. For the new Omicron variant (B.1.1.529) that harbors unprecedented multiple RBD mutations, Nb1-Nb2-Fc keeps a firm affinity (KD < 1.0 × 10-12 M) and strong neutralizing activity (IC50 = 1.46 nM for authentic Omicron virus). Together, we developed a tetravalent biparatopic human heavy-chain antibody with ultrapotent and broad-spectrum SARS-CoV-2 neutralization activity which highlights the potential clinical applications.


Subject(s)
Antibodies, Neutralizing/pharmacology , Antibodies, Viral/pharmacology , Immunoglobulin Fc Fragments/pharmacology , Recombinant Fusion Proteins/pharmacology , SARS-CoV-2/drug effects , Single-Domain Antibodies/pharmacology , Antibodies, Neutralizing/biosynthesis , Antibodies, Neutralizing/genetics , Antibodies, Viral/biosynthesis , Antibodies, Viral/genetics , Antibody Affinity , Enzyme-Linked Immunosorbent Assay , Epitopes/chemistry , Epitopes/immunology , Escherichia coli/genetics , Escherichia coli/metabolism , Gene Expression , Humans , Immunoglobulin Fc Fragments/biosynthesis , Immunoglobulin Fc Fragments/genetics , Models, Molecular , Neutralization Tests , Protein Binding/drug effects , Protein Conformation , Protein Interaction Domains and Motifs , Recombinant Fusion Proteins/biosynthesis , Recombinant Fusion Proteins/genetics , SARS-CoV-2/growth & development , SARS-CoV-2/immunology , Single-Domain Antibodies/biosynthesis , Single-Domain Antibodies/genetics , Spike Glycoprotein, Coronavirus/antagonists & inhibitors , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/genetics , Spike Glycoprotein, Coronavirus/immunology
11.
STAR Protoc ; 3(1): 101101, 2022 03 18.
Article in English | MEDLINE | ID: covidwho-1626432

ABSTRACT

The generation of high-affinity nanobodies for diverse biomedical applications typically requires immunization or affinity maturation. Here, we report a simple protocol using complementarity-determining region (CDR)-swapping mutagenesis to isolate high-affinity nanobodies from common framework libraries. This approach involves shuffling the CDRs of low-affinity variants during the sorting of yeast-displayed libraries to directly isolate high-affinity nanobodies without the need for lead isolation and optimization. We expect this approach, which we demonstrate for SARS-CoV-2 neutralizing nanobodies, will simplify the generation of high-affinity nanobodies. For complete details on the use and execution of this profile, please refer to Zupancic et al. (2021).


Subject(s)
COVID-19 , Single-Domain Antibodies , Complementarity Determining Regions/genetics , Humans , Mutagenesis , Peptide Library , SARS-CoV-2 , Single-Domain Antibodies/genetics
12.
MAbs ; 14(1): 2002236, 2022.
Article in English | MEDLINE | ID: covidwho-1585298

ABSTRACT

Coronavirus disease 2019 (COVID-19) is an evolving global public health crisis in need of therapeutic options. Passive immunization of monoclonal antibodies (mAbs) represents a promising therapeutic strategy capable of conferring immediate protection from SARS-CoV-2 infection. Herein, we describe the discovery and characterization of neutralizing SARS-CoV-2 IgG and VHH antibodies from four large-scale phage libraries. Each library was constructed synthetically with shuffled complementarity-determining region loops from natural llama and human antibody repertoires. While most candidates targeted the receptor-binding domain of the S1 subunit of SARS-CoV-2 spike protein, we also identified a neutralizing IgG candidate that binds a unique epitope on the N-terminal domain. A select number of antibodies retained binding to SARS-CoV-2 variants Alpha, Beta, Gamma, Kappa and Delta. Overall, our data show that synthetic phage libraries can rapidly yield SARS-CoV-2 S1 antibodies with therapeutically desirable features, including high affinity, unique binding sites, and potent neutralizing activity in vitro, and a capacity to limit disease in vivo.


Subject(s)
Antibodies, Neutralizing/immunology , Antibodies, Viral/immunology , COVID-19/immunology , Cell Surface Display Techniques , Immunoglobulin G/immunology , Peptide Library , SARS-CoV-2/immunology , Single-Domain Antibodies/immunology , Spike Glycoprotein, Coronavirus/immunology , Animals , Antibodies, Neutralizing/genetics , Antibodies, Neutralizing/metabolism , Antibodies, Neutralizing/pharmacology , Antibodies, Viral/genetics , Antibodies, Viral/metabolism , Antibody Specificity , Binding Sites, Antibody , COVID-19/metabolism , COVID-19/prevention & control , COVID-19/virology , Chlorocebus aethiops , Disease Models, Animal , Epitopes , Female , Host-Pathogen Interactions , Immunoglobulin G/genetics , Immunoglobulin G/metabolism , Immunoglobulin G/pharmacology , Mesocricetus , SARS-CoV-2/pathogenicity , Single-Domain Antibodies/genetics , Single-Domain Antibodies/metabolism , Single-Domain Antibodies/pharmacology , Vero Cells
13.
EMBO Rep ; 23(2): e53865, 2022 02 03.
Article in English | MEDLINE | ID: covidwho-1579708

ABSTRACT

The ongoing COVID-19 pandemic and the emergence of new SARS-CoV-2 variants of concern (VOCs) requires continued development of effective therapeutics. Recently, we identified high-affinity neutralizing nanobodies (Nbs) specific for the receptor-binding domain (RBD) of SARS-CoV-2. Taking advantage of detailed epitope mapping, we generate two biparatopic Nbs (bipNbs) targeting a conserved epitope outside and two different epitopes inside the RBD:ACE2 interface. Both bipNbs bind all currently circulating VOCs with high affinities and are capable to neutralize cellular infection with VOC B.1.351 (Beta) and B.1.617.2 (Delta) in vitro. To assess if the bipNbs NM1267 and NM1268 confer protection against SARS-CoV-2 infection in vivo, human ACE2 transgenic mice are treated intranasally before infection with a lethal dose of SARS-CoV-2 B.1, B.1.351 (Beta) or B.1.617.2 (Delta). Nb-treated mice show significantly reduced disease progression and increased survival rates. Histopathological analyses further reveal a drastically reduced viral load and inflammatory response in lungs. These data suggest that both bipNbs are broadly active against a variety of emerging SARS-CoV-2 VOCs and represent easily applicable drug candidates.


Subject(s)
COVID-19 , Single-Domain Antibodies , Animals , Antibodies, Neutralizing , Antibodies, Viral , Humans , Mice , Mice, Transgenic , Pandemics , SARS-CoV-2 , Single-Domain Antibodies/genetics , Spike Glycoprotein, Coronavirus
14.
Nat Commun ; 12(1): 5506, 2021 09 17.
Article in English | MEDLINE | ID: covidwho-1428815

ABSTRACT

Antibody engineering technologies face increasing demands for speed, reliability and scale. We develop CeVICA, a cell-free nanobody engineering platform that uses ribosome display for in vitro selection of nanobodies from a library of 1011 randomized sequences. We apply CeVICA to engineer nanobodies against the Receptor Binding Domain (RBD) of SARS-CoV-2 spike protein and identify >800 binder families using a computational pipeline based on CDR-directed clustering. Among 38 experimentally-tested families, 30 are true RBD binders and 11 inhibit SARS-CoV-2 pseudotyped virus infection. Affinity maturation and multivalency engineering increase nanobody binding affinity and yield a virus neutralizer with picomolar IC50. Furthermore, the capability of CeVICA for comprehensive binder prediction allows us to validate the fitness of our nanobody library. CeVICA offers an integrated solution for rapid generation of divergent synthetic nanobodies with tunable affinities in vitro and may serve as the basis for automated and highly parallel nanobody engineering.


Subject(s)
Antibodies, Neutralizing/immunology , Protein Engineering , SARS-CoV-2/drug effects , Single-Domain Antibodies/chemistry , Single-Domain Antibodies/pharmacology , Antibodies, Viral , COVID-19/drug therapy , Humans , Protein Binding , Reproducibility of Results , Single-Domain Antibodies/genetics , Spike Glycoprotein, Coronavirus
15.
Cell Chem Biol ; 28(9): 1379-1388.e7, 2021 09 16.
Article in English | MEDLINE | ID: covidwho-1385232

ABSTRACT

There is widespread interest in facile methods for generating potent neutralizing antibodies, nanobodies, and other affinity proteins against SARS-CoV-2 and related viruses to address current and future pandemics. While isolating antibodies from animals and humans are proven approaches, these methods are limited to the affinities, specificities, and functional activities of antibodies generated by the immune system. Here we report a surprisingly simple directed evolution method for generating nanobodies with high affinities and neutralization activities against SARS-CoV-2. We demonstrate that complementarity-determining region swapping between low-affinity lead nanobodies, which we discovered unintentionally but find is simple to implement systematically, results in matured nanobodies with unusually large increases in affinity. Importantly, the matured nanobodies potently neutralize both SARS-CoV-2 pseudovirus and live virus, and possess drug-like biophysical properties. We expect that our methods will improve in vitro nanobody discovery and accelerate the generation of potent neutralizing nanobodies against diverse coronaviruses.


Subject(s)
Antibodies, Neutralizing/genetics , Complementarity Determining Regions/genetics , Single-Domain Antibodies/genetics , Animals , Antibodies, Neutralizing/chemistry , Chlorocebus aethiops , Epitopes , HEK293 Cells , Humans , Mutagenesis , SARS-CoV-2 , Saccharomyces cerevisiae , Single-Domain Antibodies/chemistry , Spike Glycoprotein, Coronavirus/chemistry , Vero Cells
17.
Nat Chem Biol ; 17(10): 1057-1064, 2021 10.
Article in English | MEDLINE | ID: covidwho-1281726

ABSTRACT

The predominant approach for antibody generation remains animal immunization, which can yield exceptionally selective and potent antibody clones owing to the powerful evolutionary process of somatic hypermutation. However, animal immunization is inherently slow, not always accessible and poorly compatible with many antigens. Here, we describe 'autonomous hypermutation yeast surface display' (AHEAD), a synthetic recombinant antibody generation technology that imitates somatic hypermutation inside engineered yeast. By encoding antibody fragments on an error-prone orthogonal DNA replication system, surface-displayed antibody repertoires continuously mutate through simple cycles of yeast culturing and enrichment for antigen binding to produce high-affinity clones in as little as two weeks. We applied AHEAD to generate potent nanobodies against the SARS-CoV-2 S glycoprotein, a G-protein-coupled receptor and other targets, offering a template for streamlined antibody generation at large.


Subject(s)
Antibody Formation/immunology , Protein Engineering/methods , Recombinant Proteins/biosynthesis , Antibodies/immunology , Antigens , COVID-19/immunology , Humans , Peptide Library , Recombinant Proteins/metabolism , SARS-CoV-2/immunology , SARS-CoV-2/pathogenicity , Saccharomyces cerevisiae/metabolism , Single-Domain Antibodies/genetics , Single-Domain Antibodies/metabolism , Spike Glycoprotein, Coronavirus/immunology
18.
Nature ; 595(7866): 278-282, 2021 07.
Article in English | MEDLINE | ID: covidwho-1258586

ABSTRACT

Since the start of the COVID-19 pandemic, SARS-CoV-2 has caused millions of deaths worldwide. Although a number of vaccines have been deployed, the continual evolution of the receptor-binding domain (RBD) of the virus has challenged their efficacy. In particular, the emerging variants B.1.1.7, B.1.351 and P.1 (first detected in the UK, South Africa and Brazil, respectively) have compromised the efficacy of sera from patients who have recovered from COVID-19 and immunotherapies that have received emergency use authorization1-3. One potential alternative to avert viral escape is the use of camelid VHHs (variable heavy chain domains of heavy chain antibody (also known as nanobodies)), which can recognize epitopes that are often inaccessible to conventional antibodies4. Here, we isolate anti-RBD nanobodies from llamas and from mice that we engineered to produce VHHs cloned from alpacas, dromedaries and Bactrian camels. We identified two groups of highly neutralizing nanobodies. Group 1 circumvents antigenic drift by recognizing an RBD region that is highly conserved in coronaviruses but rarely targeted by human antibodies. Group 2 is almost exclusively focused to the RBD-ACE2 interface and does not neutralize SARS-CoV-2 variants that carry E484K or N501Y substitutions. However, nanobodies in group 2 retain full neutralization activity against these variants when expressed as homotrimers, and-to our knowledge-rival the most potent antibodies against SARS-CoV-2 that have been produced to date. These findings suggest that multivalent nanobodies overcome SARS-CoV-2 mutations through two separate mechanisms: enhanced avidity for the ACE2-binding domain and recognition of conserved epitopes that are largely inaccessible to human antibodies. Therefore, although new SARS-CoV-2 mutants will continue to emerge, nanobodies represent promising tools to prevent COVID-19 mortality when vaccines are compromised.


Subject(s)
Antibodies, Neutralizing/immunology , Camelids, New World/immunology , SARS-CoV-2/immunology , Single-Domain Antibodies/chemistry , Single-Domain Antibodies/immunology , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/immunology , Animals , Antibodies, Neutralizing/chemistry , Antibodies, Neutralizing/genetics , Antibodies, Neutralizing/isolation & purification , CRISPR-Cas Systems , Camelids, New World/genetics , Female , Gene Editing , Humans , Male , Mice , Mice, Inbred C57BL , Models, Molecular , Mutation , Neutralization Tests , SARS-CoV-2/chemistry , SARS-CoV-2/genetics , Single-Domain Antibodies/genetics , Single-Domain Antibodies/isolation & purification , Somatic Hypermutation, Immunoglobulin/genetics
19.
PLoS Pathog ; 17(3): e1009328, 2021 03.
Article in English | MEDLINE | ID: covidwho-1115314

ABSTRACT

A key step to the SARS-CoV-2 infection is the attachment of its Spike receptor-binding domain (S RBD) to the host receptor ACE2. Considerable research has 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. Simple and effective strategies to increase potency are desirable for such studies when antibodies are only modestly effective. Here, we identify and characterize a high-affinity synthetic nanobody (sybody, SR31) as a fusion partner to improve the potency of RBM-antibodies. Crystallographic studies reveal that SR31 binds to RBD at a conserved and 'greasy' site distal to RBM. Although SR31 distorts RBD at the interface, it does not perturb the RBM conformation, hence displaying no neutralizing activities itself. However, fusing SR31 to two modestly neutralizing sybodies dramatically increases their affinity for RBD and neutralization activity against SARS-CoV-2 pseudovirus. Our work presents a tool protein and an efficient strategy to improve nanobody potency.


Subject(s)
Angiotensin-Converting Enzyme 2/immunology , Antibodies, Neutralizing/immunology , Antibodies, Viral/immunology , SARS-CoV-2/immunology , Single-Domain Antibodies/immunology , Antibodies, Neutralizing/chemistry , Antibodies, Neutralizing/genetics , Antibodies, Viral/chemistry , Antibodies, Viral/genetics , Antibody Affinity , Binding Sites , Crystallography, X-Ray , HEK293 Cells , Humans , Models, Molecular , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunology , Single-Domain Antibodies/chemistry , Single-Domain Antibodies/genetics
20.
ACS Synth Biol ; 10(2): 379-390, 2021 02 19.
Article in English | MEDLINE | ID: covidwho-1061167

ABSTRACT

Generating and characterizing immunoreagents to enable studies of novel emerging viruses is an area where ensembles of synthetic genes, recombinant antibody pipelines, and modular antibody-reporter fusion proteins can respond rapidly. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to spread through the global population causing widespread morbidity, mortality, and socioeconomic chaos. Using SARS-CoV-2 as our model and starting with a gBlocks encoded nucleocapsid (N) gene, we purified recombinant protein from E. coli, to serve as bait for selecting semisynthetic nanobodies from our Nomad single-pot library. Clones were isolated in days and first fused to Gaussia luciferase to determine EC50 in the tens of nM range, and second fused to the ascorbate peroxidase derivative APEX2 for sensitive detection of SARS-CoV-2 infected cells. To generate inherently fluorescent immunoreagents, we introduce novel periplasmic sdAb fusions made with mNeonGreen and mScarlet-I, which were produced at milligram amounts. The fluorescent fusion proteins enabled concise visualization of SARS-CoV-2 N in the cytoplasm but not in the nucleus 24 h post infection, akin to the distribution of SARS-CoV N, thereby validating these useful imaging tools. SdAb reactivity appeared specific to SARS-CoV-2 with very much weaker binding to SARS-CoV, and no noticeable cross-reactivity to a panel of overexpressed human codon optimized N proteins from other CoV. High periplasmic expression levels and in silico immortalization of the nanobody constructs guarantees a cost-effective and reliable source of SARS-CoV-2 immunoreagents. Our proof-of-principle study should be applicable to known and newly emerging CoV to broaden the tools available for their analysis and help safeguard human health in a more proactive than reactive manner.


Subject(s)
COVID-19/epidemiology , COVID-19/virology , Coronavirus Nucleocapsid Proteins/genetics , Molecular Probes/genetics , Pandemics , SARS-CoV-2/genetics , SARS-CoV-2/immunology , Antibodies, Viral/genetics , Antibody Specificity/genetics , COVID-19/immunology , Communicable Diseases, Emerging/virology , Coronavirus Nucleocapsid Proteins/immunology , Escherichia coli/genetics , Fluorescent Antibody Technique , Genes, Synthetic , Genes, Viral , HEK293 Cells , Humans , Molecular Probes/immunology , Pandemics/prevention & control , Peptide Library , Phosphoproteins/genetics , Phosphoproteins/immunology , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunology , SARS-CoV-2/pathogenicity , Single-Domain Antibodies/genetics , Synthetic Biology
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