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1.
Vaccine ; 39(45): 6601-6613, 2021 10 29.
Article in English | MEDLINE | ID: covidwho-1541007

ABSTRACT

AKS-452 is a biologically-engineered vaccine comprising an Fc fusion protein of the SARS-CoV-2 viral spike protein receptor binding domain antigen (Ag) and human IgG1 Fc (SP/RBD-Fc) in clinical development for the induction and augmentation of neutralizing IgG titers against SARS-CoV-2 viral infection to address the COVID-19 pandemic. The Fc moiety is designed to enhance immunogenicity by increasing uptake via Fc-receptors (FcγR) on Ag-presenting cells (APCs) and prolonging exposure due to neonatal Fc receptor (FcRn) recycling. AKS-452 induced approximately 20-fold greater neutralizing IgG titers in mice relative to those induced by SP/RBD without the Fc moiety and induced comparable long-term neutralizing titers with a single dose vs. two doses. To further enhance immunogenicity, AKS-452 was evaluated in formulations containing a panel of adjuvants in which the water-in-oil adjuvant, Montanide™ ISA 720, enhanced neutralizing IgG titers by approximately 7-fold after one and two doses in mice, including the neutralization of live SARS-CoV-2 virus infection of VERO-E6 cells. Furthermore, ISA 720-adjuvanted AKS-452 was immunogenic in rabbits and non-human primates (NHPs) and protected from infection and clinical symptoms with live SARS-CoV-2 virus in NHPs (USA-WA1/2020 viral strain) and the K18 human ACE2-trangenic (K18-huACE2-Tg) mouse (South African B.1.351 viral variant). These preclinical studies support the initiation of Phase I clinical studies with adjuvanted AKS-452 with the expectation that this room-temperature stable, Fc-fusion subunit vaccine can be rapidly and inexpensively manufactured to provide billions of doses per year especially in regions where the cold-chain is difficult to maintain.


Subject(s)
COVID-19 Vaccines/immunology , COVID-19 , Spike Glycoprotein, Coronavirus/immunology , Animals , Antibodies, Neutralizing , Antibodies, Viral , COVID-19/prevention & control , Immunoglobulin G , Mice , Primates , Rabbits , Recombinant Fusion Proteins/immunology , SARS-CoV-2 , Vaccines, Subunit
2.
Signal Transduct Target Ther ; 6(1): 389, 2021 11 10.
Article in English | MEDLINE | ID: covidwho-1510582

ABSTRACT

SARS-CoV-2 and SARS-CoV are genetically related coronavirus and share the same cellular receptor ACE2. By replacing the VSV glycoprotein with the spikes (S) of SARS-CoV-2 and SARS-CoV, we generated two replication-competent recombinant viruses, rVSV-SARS-CoV-2 and rVSV-SARS-CoV. Using wild-type and human ACE2 (hACE2) knock-in mouse models, we found a single dose of rVSV-SARS-CoV could elicit strong humoral immune response via both intranasal (i.n.) and intramuscular (i.m.) routes. Despite the high genetic similarity between SARS-CoV-2 and SARS-CoV, no obvious cross-neutralizing activity was observed in the immunized mice sera. In macaques, neutralizing antibody (NAb) titers induced by one i.n. dose of rVSV-SARS-CoV-2 were eight-fold higher than those by a single i.m. dose. Thus, our data indicates that rVSV-SARS-CoV-2 might be suitable for i.n. administration instead of the traditional i.m. immunization in human. Because rVSV-SARS-CoV elicited significantly stronger NAb responses than rVSV-SARS-CoV-2 in a route-independent manner, we generated a chimeric antigen by replacing the receptor binding domain (RBD) of SARS-CoV S with that from the SARS-CoV-2. rVSV expressing the chimera (rVSV-SARS-CoV/2-RBD) induced significantly increased NAbs against SARS-CoV-2 in mice and macaques than rVSV-SARS-CoV-2, with a safe Th1-biased response. Serum immunized with rVSV-SARS-CoV/2-RBD showed no cross-reactivity with SARS-CoV. hACE2 mice receiving a single i.m. dose of either rVSV-SARS-CoV-2 or rVSV-SARS-CoV/2-RBD were fully protected against SARS-CoV-2 challenge without obvious lesions in the lungs. Our results suggest that transplantation of SARS-CoV-2 RBD into the S protein of SARS-CoV might be a promising antigen design for COVID-19 vaccines.


Subject(s)
COVID-19 Vaccines/immunology , COVID-19/prevention & control , Spike Glycoprotein, Coronavirus/immunology , Animals , Antibodies, Neutralizing/blood , Antibodies, Viral/blood , Gene Knock-In Techniques , HEK293 Cells , Humans , Mice , Mice, Inbred C57BL , Neutralization Tests , Recombinant Fusion Proteins/immunology , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/genetics
3.
Int J Mol Sci ; 22(20)2021 Oct 18.
Article in English | MEDLINE | ID: covidwho-1470893

ABSTRACT

SputnikV is a vaccine against SARS-CoV-2 developed by the Gamaleya National Research Centre for Epidemiology and Microbiology. The vaccine has been shown to induce both humoral and cellular immune responses, yet the mechanisms remain largely unknown. Forty SputnikV vaccinated individuals were included in this study which aimed to demonstrate the location of immunogenic domains of the SARS-CoV-2 S protein using an overlapping peptide library. Additionally, cytokines in the serum of vaccinated and convalescent COVID-19 patients were analyzed. We have found antibodies from both vaccinated and convalescent sera bind to immunogenic regions located in multiple domains of SARS-CoV-2 S protein, including Receptor Binding Domain (RBD), N-terminal Domain (NTD), Fusion Protein (FP) and Heptad Repeats (HRs). Interestingly, many peptides were recognized by immunized and convalescent serum antibodies and correspond to conserved regions in circulating variants of SARS-CoV-2. This breadth of reactivity was still evident 90 days after the first dose of the vaccine, showing that the vaccine has induced a prolonged response. As evidenced by the activation of T cells, cellular immunity strongly suggests the high potency of the SputnikV vaccine against SARS-CoV-2 infection.


Subject(s)
COVID-19 Vaccines/administration & dosage , COVID-19/prevention & control , Immunity, Cellular , Immunity, Humoral , Adult , Amino Acid Sequence , COVID-19/immunology , COVID-19/virology , COVID-19 Vaccines/immunology , Cytokines/metabolism , Female , Humans , Male , Peptides/chemistry , Peptides/immunology , Principal Component Analysis , Recombinant Fusion Proteins/biosynthesis , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunology , SARS-CoV-2/isolation & purification , SARS-CoV-2/metabolism , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/immunology , T-Lymphocytes/cytology , T-Lymphocytes/immunology , T-Lymphocytes/metabolism , Vaccination
4.
Proc Natl Acad Sci U S A ; 118(44)2021 11 02.
Article in English | MEDLINE | ID: covidwho-1470027

ABSTRACT

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in over 100 million infections and millions of deaths. Effective vaccines remain the best hope of curtailing SARS-CoV-2 transmission, morbidity, and mortality. The vaccines in current use require cold storage and sophisticated manufacturing capacity, which complicates their distribution, especially in less developed countries. We report the development of a candidate SARS-CoV-2 vaccine that is purely protein based and directly targets antigen-presenting cells. It consists of the SARS-CoV-2 Spike receptor-binding domain (SpikeRBD) fused to an alpaca-derived nanobody that recognizes class II major histocompatibility complex antigens (VHHMHCII). This vaccine elicits robust humoral and cellular immunity against SARS-CoV-2 and its variants. Both young and aged mice immunized with two doses of VHHMHCII-SpikeRBD elicit high-titer binding and neutralizing antibodies. Immunization also induces strong cellular immunity, including a robust CD8 T cell response. VHHMHCII-SpikeRBD is stable for at least 7 d at room temperature and can be lyophilized without loss of efficacy.


Subject(s)
COVID-19 Vaccines/immunology , COVID-19 Vaccines/pharmacology , COVID-19/immunology , COVID-19/prevention & control , Pandemics , SARS-CoV-2/immunology , Amino Acid Sequence , Animals , Antibodies, Neutralizing/biosynthesis , Antibodies, Viral/biosynthesis , Antigen-Presenting Cells/immunology , CD8-Positive T-Lymphocytes/immunology , COVID-19/epidemiology , COVID-19 Vaccines/administration & dosage , Camelids, New World/immunology , Female , Histocompatibility Antigens Class II/immunology , Humans , Immunity, Cellular , Immunity, Humoral , Immunization, Secondary , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Transgenic , Pandemics/prevention & control , Recombinant Fusion Proteins/administration & dosage , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunology , SARS-CoV-2/genetics , Single-Domain Antibodies/administration & dosage , Single-Domain Antibodies/immunology , Spike Glycoprotein, Coronavirus/administration & dosage , Spike Glycoprotein, Coronavirus/genetics , Spike Glycoprotein, Coronavirus/immunology
5.
Immunogenetics ; 73(6): 459-477, 2021 12.
Article in English | MEDLINE | ID: covidwho-1427234

ABSTRACT

Since 2019, the world was involved with SARS-CoV-2 and consequently, with the announcement by the World Health Organization that COVID-19 was a pandemic, scientific were an effort to obtain the best approach to combat this global dilemma. The best way to prevent the pandemic from spreading further is to use a vaccine against COVID-19. Here, we report the design of a recombinant multi-epitope vaccine against the four proteins spike or crown (S), membrane (M), nucleocapsid (N), and envelope (E) of SARS-CoV-2 using immunoinformatics tools. We evaluated the most antigenic epitopes that bind to HLA class 1 subtypes, along with HLA class 2, as well as B cell epitopes. Beta-defensin 3 and PADRE sequence were used as adjuvants in the structure of the vaccine. KK, GPGPG, and AAY linkers were used to fuse the selected epitopes. The nucleotide sequence was cloned into pET26b(+) vector using restriction enzymes XhoI and NdeI, and HisTag sequence was considered in the C-terminal of the construct. The results showed that the proposed candidate vaccine is a 70.87 kDa protein with high antigenicity and immunogenicity as well as non-allergenic and non-toxic. A total of 95% of the selected epitopes have conservancy with similar sequences. Molecular docking showed a strong binding between the vaccine structure and tool-like receptor (TLR) 7/8. The docking, molecular dynamics, and MM/PBSA analysis showed that the vaccine established a stable interaction with both structures of TLR7 and TLR8. Simulation of immune stimulation by this vaccine showed that it evokes immune responses related to humoral and cellular immunity.


Subject(s)
COVID-19 Vaccines/immunology , Epitopes, B-Lymphocyte/immunology , Epitopes, T-Lymphocyte/immunology , SARS-CoV-2/immunology , Amino Acid Sequence , Base Sequence , COVID-19/prevention & control , COVID-19 Vaccines/genetics , COVID-19 Vaccines/metabolism , Computational Biology , Epitopes, B-Lymphocyte/chemistry , Epitopes, B-Lymphocyte/genetics , Epitopes, T-Lymphocyte/chemistry , Epitopes, T-Lymphocyte/genetics , HLA Antigens/immunology , Humans , Immunogenicity, Vaccine , Molecular Docking Simulation , Molecular Dynamics Simulation , Molecular Weight , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunology , Toll-Like Receptor 7/chemistry , Toll-Like Receptor 8/chemistry , Vaccines, Subunit/genetics , Vaccines, Subunit/immunology , Vaccines, Subunit/metabolism , Vaccinology , Viral Proteins/chemistry , Viral Proteins/genetics , Viral Proteins/immunology
6.
Front Immunol ; 12: 679841, 2021.
Article in English | MEDLINE | ID: covidwho-1369665

ABSTRACT

Understanding the course of the antibody response directed to individual epitopes of SARS-CoV-2 proteins is crucial for serological assays and establishment of vaccines. Twenty-one synthetic peptides were synthesized that have ten amino acids overlap and cover the complete membrane (M) protein. Plasma samples from 32 patients having acute disease and 30 patients from the convalescent phase were studied. Only peptide M01 (aa 1-20) and to a lesser extent peptide M21 (aa 201-222) showed specific reactivity as compared to historical control plasma samples. Peptide M01 was recognized by IgM- (71.9%) and IgG-specific antibodies (43.8%) during the acute phase as early as day 8 PIO. In a longitudinal analysis, a higher reactivity was observed for the IgM response directed to peptide M01 following day 20 PIO as compared to earlier time points of the acute phase. In the convalescent phase, antibody reactivity to the two M-specific peptides was significantly lower (<30% seropositivity). A fusion protein encoding major parts of RBD also showed higher rates of recognition during acute (50.0%) and lower rates in the convalescent phase (23.3%). Taken together, our results suggest that during the acute phase of COVID-19 antibodies are raised to two linear epitopes of the SARS-CoV-2 M protein, located at the very N- and C-termini, showing almost similar levels of reactivity as immunodominant linear epitopes derived from the spike and nucleocapsid protein. Anti-M is also present in the convalescent phase of COVID-19 patients, however at lower levels, with the N-terminus of the M protein as a preferred target.


Subject(s)
Antibodies, Viral/immunology , COVID-19/immunology , SARS-CoV-2/immunology , Viral Matrix Proteins/immunology , Adult , Aged , Aged, 80 and over , Antibodies, Viral/biosynthesis , Convalescence , Coronavirus Nucleocapsid Proteins/immunology , Female , Humans , Immunodominant Epitopes/immunology , Immunoglobulin M/immunology , Male , Middle Aged , Patient Acuity , Peptide Fragments/immunology , Recombinant Fusion Proteins/immunology , SARS-CoV-2/genetics , Spike Glycoprotein, Coronavirus/immunology , Viral Matrix Proteins/genetics
7.
Commun Biol ; 4(1): 366, 2021 03 19.
Article in English | MEDLINE | ID: covidwho-1351981

ABSTRACT

GFP fusion-based fluorescence-detection size-exclusion chromatography (FSEC) has been widely employed for membrane protein expression screening. However, fused GFP itself may occasionally affect the expression and/or stability of the targeted membrane protein, leading to both false-positive and false-negative results in expression screening. Furthermore, GFP fusion technology is not well suited for some membrane proteins, depending on their membrane topology. Here, we developed an FSEC assay utilizing nanobody (Nb) technology, named FSEC-Nb, in which targeted membrane proteins are fused to a small peptide tag and recombinantly expressed. The whole-cell extracts are solubilized, mixed with anti-peptide Nb fused to GFP for FSEC analysis. FSEC-Nb enables the evaluation of the expression, monodispersity and thermostability of membrane proteins without the need for purification but does not require direct GFP fusion to targeted proteins. Our results show FSEC-Nb as a powerful tool for expression screening of membrane proteins for structural and functional studies.


Subject(s)
Chromatography, Gel , Green Fluorescent Proteins/metabolism , Membrane Proteins/metabolism , Nanotechnology , Peptides/metabolism , Single-Domain Antibodies/immunology , Animals , Cryoelectron Microscopy , Cysteine Loop Ligand-Gated Ion Channel Receptors/genetics , Cysteine Loop Ligand-Gated Ion Channel Receptors/immunology , Cysteine Loop Ligand-Gated Ion Channel Receptors/metabolism , Fish Proteins/genetics , Fish Proteins/immunology , Fish Proteins/metabolism , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/immunology , HEK293 Cells , Humans , Membrane Proteins/genetics , Membrane Proteins/immunology , Oryzias/genetics , Oryzias/metabolism , Peptides/genetics , Peptides/immunology , Protein Stability , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunology , Recombinant Fusion Proteins/metabolism , SARS-CoV-2/genetics , SARS-CoV-2/immunology , SARS-CoV-2/metabolism , Spectrometry, Fluorescence , Temperature , Viral Proteins/genetics , Viral Proteins/immunology , Viral Proteins/metabolism
8.
Sci Adv ; 7(32)2021 08.
Article in English | MEDLINE | ID: covidwho-1343936

ABSTRACT

Host antibody responses are pivotal for providing protection against infectious agents. We have pioneered a new class of self-assembling micelles based on pentablock copolymers that enhance antibody responses while providing a low inflammatory environment compared to traditional adjuvants. This type of "just-right" immune response is critical in the rational design of vaccines for older adults. Here, we report on the mechanism of enhancement of antibody responses by pentablock copolymer micelles, which act as scaffolds for antigen presentation to B cells and cross-link B cell receptors, unlike other micelle-forming synthetic block copolymers. We exploited this unique mechanism and developed these scaffolds as a platform technology to produce antibodies in vitro. We show that this novel approach can be used to generate laboratory-scale quantities of therapeutic antibodies against multiple antigens, including those associated with SARS-CoV-2 and Yersinia pestis, further expanding the value of these nanomaterials to rapidly develop countermeasures against infectious diseases.


Subject(s)
Antibody Formation , Antigen Presentation/immunology , Cross-Linking Reagents/chemistry , Receptors, Antigen, B-Cell/chemistry , Recombinant Fusion Proteins/immunology , Spike Glycoprotein, Coronavirus/immunology , Yersinia pestis/immunology , Adjuvants, Immunologic , Animals , Female , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Polymers/chemistry , Receptors, Antigen, B-Cell/metabolism
9.
Sci Adv ; 7(22)2021 05.
Article in English | MEDLINE | ID: covidwho-1247308

ABSTRACT

Since the emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), various vaccines are being developed, with most vaccine candidates focusing on the viral spike protein. Here, we developed a previously unknown subunit vaccine comprising the receptor binding domain (RBD) of the spike protein fused with the tetanus toxoid epitope P2 (RBD-P2) and tested its efficacy in rodents and nonhuman primates (NHPs). We also investigated whether the SARS-CoV-2 nucleocapsid protein (N) could increase vaccine efficacy. Immunization with N and RBD-P2 (RBDP2/N) + alum increased T cell responses in mice and neutralizing antibody levels in rats compared with those obtained using RBD-P2 + alum. Furthermore, in NHPs, RBD-P2/N + alum induced slightly faster SARS-CoV-2 clearance than that induced by RBD-P2 + alum, albeit without statistical significance. Our study supports further development of RBD-P2 as a vaccine candidate against SARS-CoV-2. Also, it provides insights regarding the use of N in protein-based vaccines against SARS-CoV-2.


Subject(s)
COVID-19 Vaccines/immunology , COVID-19/prevention & control , Coronavirus Nucleocapsid Proteins/immunology , Recombinant Fusion Proteins/immunology , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus/immunology , Tetanus Toxoid/immunology , Animals , COVID-19/genetics , COVID-19/immunology , COVID-19 Vaccines/genetics , Chlorocebus aethiops , Coronavirus Nucleocapsid Proteins/genetics , Female , Macaca fascicularis , Mice , Mice, Inbred BALB C , Mice, Transgenic , Phosphoproteins/genetics , Phosphoproteins/immunology , Protein Domains , Rats , Recombinant Fusion Proteins/genetics , SARS-CoV-2/genetics , Sf9 Cells , Spike Glycoprotein, Coronavirus/genetics , Spodoptera , Tetanus Toxoid/genetics , Vero Cells
10.
Front Immunol ; 12: 637654, 2021.
Article in English | MEDLINE | ID: covidwho-1138709

ABSTRACT

A coronavirus SARS-CoV-2, which has caused the pandemic viral pneumonia disease COVID-19, significantly threatens global public health, highlighting the need to develop effective and safe vaccines against its infection. In this study, we developed a novel DNA vaccine candidate against SARS-CoV-2 by expressing a chimeric protein of its receptor-binding domain (RBD) fused to a 33-bp sequence (11 aa) from the hepatitis B virus (HBV) preS1 region with a W4P mutation (W4P-RBD) at the N-terminal region and evaluated its immunogenicity. In vitro transfection experiments in multiple cell lines demonstrated that W4P-RBD vs. wild-type RBD protein (W-RBD) led to enhanced production of IL-6 and TNFα at the transcription and translation levels, suggesting the adjuvant potential of N-terminal HBV preS1 sequences for DNA vaccines against SARS-CoV-2. W4P-RBD also led to enhanced production of IgG and IgA, which can neutralize and block SARS-CoV-2 infection in both blood sera and bronchoalveolar lavage (BAL) fluid from the lung in vaccinated mice. Additionally, W4P-RBD led to an enhanced T-cell-mediated cellular immune response under S1 protein stimulation. In summary, W4P-RBD led to robust humoral and cell-mediated immune responses against SARS-CoV-2 in vaccinated mice, highlighting its feasibility as a novel DNA vaccine to protect against SARS-CoV-2 infection.


Subject(s)
COVID-19 Vaccines/immunology , COVID-19/prevention & control , Hepatitis B Surface Antigens/genetics , Hepatitis B Surface Antigens/immunology , Mutation , Protein Domains/immunology , Protein Precursors/genetics , Protein Precursors/immunology , Recombinant Fusion Proteins/immunology , SARS-CoV-2/immunology , Vaccines, DNA/immunology , Animals , Antibodies, Neutralizing/blood , Antibodies, Neutralizing/immunology , Antibodies, Viral/blood , Antibodies, Viral/immunology , COVID-19/virology , Cell Line, Tumor , Chlorocebus aethiops , HEK293 Cells , Humans , Immunogenicity, Vaccine , Male , Mice , Mice, Inbred C57BL , Vaccination/methods , Vero Cells
11.
Biochem Biophys Res Commun ; 553: 165-171, 2021 05 14.
Article in English | MEDLINE | ID: covidwho-1135259

ABSTRACT

The COVID-19 pandemic has caused significant morbidity and mortality. There is an urgent need for serological tests to detect antibodies against SARS-CoV-2, which could be used to assess past infection, evaluate responses to vaccines in development, and determine individuals who may be protected from future infection. Current serological tests developed for SARS-CoV-2 rely on traditional technologies such as enzyme-linked immunosorbent assays (ELISA) and lateral flow assays, which have not scaled to meet the demand of hundreds of millions of antibody tests so far. Herein, we present an alternative method of antibody testing that depends on one protein reagent being added to patient serum/plasma or whole blood with direct, visual readout. Two novel fusion proteins, RBD-2E8 and B6-CH1-RBD, were designed to bind red blood cells (RBCs) via a single-chain variable fragment (scFv), thereby displaying the receptor-binding domain (RBD) of SARS-CoV-2 spike protein on the surface of RBCs. Mixing mammalian-derived RBD-2E8 and B6-CH1-RBD with convalescent COVID-19 patient serum and RBCs led to visible hemagglutination, indicating the presence of antibodies against SARS-CoV-2 RBD. B6-CH1-RBD made in bacteria was not as effective in inducing agglutination, indicating better recognition of RBD epitopes from mammalian cells. Given that our hemagglutination test uses methods routinely used in hospital clinical labs across the world for blood typing, we anticipate the test can be rapidly deployed at minimal cost. We anticipate our hemagglutination assay may find extensive use in low-resource settings for detecting SARS-CoV-2 antibodies.


Subject(s)
Antibodies, Viral/analysis , Antibodies, Viral/immunology , COVID-19 Serological Testing/methods , COVID-19/blood , COVID-19/immunology , Hemagglutination Tests/methods , Point-of-Care Systems , SARS-CoV-2/immunology , Antigens, Viral/immunology , COVID-19/diagnosis , COVID-19/virology , COVID-19 Serological Testing/economics , Erythrocytes/immunology , Hemagglutination Tests/economics , Humans , Point-of-Care Systems/economics , Recombinant Fusion Proteins/immunology , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/immunology , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/immunology , Time Factors
12.
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
13.
Front Immunol ; 11: 602254, 2020.
Article in English | MEDLINE | ID: covidwho-1081589

ABSTRACT

Given the aggressive spread of COVID-19-related deaths, there is an urgent public health need to support the development of vaccine candidates to rapidly improve the available control measures against SARS-CoV-2. To meet this need, we are leveraging our existing vaccine platform to target SARS-CoV-2. Here, we generated cellular heat shock chaperone protein, glycoprotein 96 (gp96), to deliver SARS-CoV-2 protein S (spike) to the immune system and to induce cell-mediated immune responses. We showed that our vaccine platform effectively stimulates a robust cellular immune response against protein S. Moreover, we confirmed that gp96-Ig, secreted from allogeneic cells expressing full-length protein S, generates powerful, protein S polyepitope-specific CD4+ and CD8+ T cell responses in both lung interstitium and airways. These findings were further strengthened by the observation that protein-S -specific CD8+ T cells were induced in human leukocyte antigen HLA-A2.1 transgenic mice thus providing encouraging translational data that the vaccine is likely to work in humans, in the context of SARS-CoV-2 antigen presentation.


Subject(s)
CD8-Positive T-Lymphocytes/immunology , COVID-19 Vaccines/immunology , COVID-19/prevention & control , Lung/immunology , Spike Glycoprotein, Coronavirus/administration & dosage , Animals , COVID-19 Vaccines/pharmacology , Genetic Vectors/immunology , Genetic Vectors/pharmacology , Humans , Immunoglobulin G/immunology , Membrane Glycoproteins/administration & dosage , Membrane Glycoproteins/immunology , Mice , Mice, Inbred C57BL , Recombinant Fusion Proteins/administration & dosage , Recombinant Fusion Proteins/immunology , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus/immunology
14.
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
15.
J Biol Chem ; 296: 100346, 2021.
Article in English | MEDLINE | ID: covidwho-1056842

ABSTRACT

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has developed into a global pandemic since its first outbreak in the winter of 2019. An extensive investigation of SARS-CoV-2 is critical for disease control. Various recombinant monoclonal antibodies of human origin that neutralize SARS-CoV-2 infection have been isolated from convalescent patients and will be applied as therapies and prophylaxis. However, the need for dedicated monoclonal antibodies suitable for molecular pathology research is not fully addressed. Here, we produced six mouse anti-SARS-CoV-2 spike monoclonal antibodies that not only exhibit robust performance in immunoassays including western blotting, ELISA, immunofluorescence, and immunoprecipitation, but also demonstrate neutralizing activity against SARS-CoV-2 infection to VeroE6/TMPRSS2 cells. Due to their mouse origin, our monoclonal antibodies are compatible with the experimental immunoassay setups commonly used in basic molecular biology research laboratories, providing a useful tool for future research. Furthermore, in the hope of applying the antibodies of clinical setting, we determined the variable regions of the antibodies and used them to produce recombinant human/mouse chimeric antibodies.


Subject(s)
Antibodies, Monoclonal/biosynthesis , Antibodies, Neutralizing/biosynthesis , Antibodies, Viral/biosynthesis , COVID-19/prevention & control , SARS-CoV-2/genetics , Spike Glycoprotein, Coronavirus/genetics , Animals , Antibodies, Monoclonal/chemistry , Antibodies, Monoclonal/isolation & purification , Antibodies, Neutralizing/chemistry , Antibodies, Neutralizing/isolation & purification , Antibodies, Viral/chemistry , Antibodies, Viral/isolation & purification , Binding Sites , COVID-19/immunology , COVID-19/virology , Cloning, Molecular , Escherichia coli/genetics , Escherichia coli/metabolism , Gene Expression , Genetic Vectors/chemistry , Genetic Vectors/metabolism , Humans , Mice , Neutralization Tests , Protein Binding , Protein Interaction Domains and Motifs , Protein Subunits/administration & dosage , Protein Subunits/genetics , Protein Subunits/immunology , Recombinant Fusion Proteins/administration & dosage , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunology , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus/administration & dosage , Spike Glycoprotein, Coronavirus/immunology , Vaccination
16.
EMBO Mol Med ; 13(3): e13549, 2021 03 05.
Article in English | MEDLINE | ID: covidwho-1038772

ABSTRACT

A correct identification of seropositive individuals for the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is of paramount relevance to assess the degree of protection of a human population to present and future outbreaks of the COVID-19 pandemic. We describe here a sensitive and quantitative flow cytometry method using the cytometer-friendly non-adherent Jurkat T-cell line that stably expresses the full-length native spike "S" protein of SARS-CoV-2 and a truncated form of the human EGFR that serves a normalizing role. S protein and huEGFRt coding sequences are separated by a T2A self-cleaving sequence, allowing to accurately quantify the presence of anti-S immunoglobulins by calculating a score based on the ratio of fluorescence intensities obtained by double-staining with the test sera and anti-EGFR. The method allows to detect immune individuals regardless of the result of other serological tests or even repeated PCR monitoring. As examples of its use, we show that as much as 28% of the personnel working at the CBMSO in Madrid is already immune. Additionally, we show that anti-S antibodies with protective neutralizing activity are long-lasting and can be detected in sera 8 months after infection.


Subject(s)
Antibodies, Neutralizing/blood , Antibodies, Viral/blood , COVID-19 Serological Testing/methods , COVID-19/diagnosis , COVID-19/immunology , Flow Cytometry/methods , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus/immunology , Adult , COVID-19/virology , COVID-19 Serological Testing/statistics & numerical data , Enzyme-Linked Immunosorbent Assay , ErbB Receptors/genetics , Female , Flow Cytometry/statistics & numerical data , Hep G2 Cells , Humans , Jurkat Cells , Male , Middle Aged , Neutralization Tests , Pandemics , Polymerase Chain Reaction , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunology , SARS-CoV-2/genetics , Spike Glycoprotein, Coronavirus/genetics
17.
Immunity ; 53(6): 1315-1330.e9, 2020 12 15.
Article in English | MEDLINE | ID: covidwho-967948

ABSTRACT

Various vaccine strategies have been proposed in response to the global COVID-19 pandemic, each with unique strategies for eliciting immune responses. Here, we developed nanoparticle vaccines by covalently conjugating the self-assembled 24-mer ferritin to the receptor binding domain (RBD) and/or heptad repeat (HR) subunits of the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) spike (S) protein. Compared to monomer vaccines, nanoparticle vaccines elicited more robust neutralizing antibodies and cellular immune responses. RBD and RBD-HR nanoparticle vaccinated hACE2 transgenic mice vaccinated with RBD and/or RBD-HR nanoparticles exhibited reduced viral load in the lungs after SARS-CoV-2 challenge. RBD-HR nanoparticle vaccines also promoted neutralizing antibodies and cellular immune responses against other coronaviruses. The nanoparticle vaccination of rhesus macaques induced neutralizing antibodies, and T and B cell responses prior to boost immunization; these responses persisted for more than three months. RBD- and HR-based nanoparticles thus present a promising vaccination approach against SARS-CoV-2 and other coronaviruses.


Subject(s)
Bacterial Proteins/immunology , COVID-19 Vaccines/immunology , COVID-19/immunology , Ferritins/immunology , Helicobacter pylori/metabolism , Recombinant Fusion Proteins/immunology , SARS-CoV-2/physiology , Spike Glycoprotein, Coronavirus/immunology , Angiotensin-Converting Enzyme 2/genetics , Angiotensin-Converting Enzyme 2/metabolism , Animals , Antibodies, Neutralizing/metabolism , Antibodies, Viral/metabolism , Bacterial Proteins/chemistry , COVID-19 Vaccines/chemistry , Ferritins/chemistry , Humans , Macaca mulatta , Mice , Mice, Inbred BALB C , Nanoparticles/chemistry , Pandemics , Protein Binding , Spike Glycoprotein, Coronavirus/chemistry , Vaccination
18.
EMBO Mol Med ; 13(1): e12828, 2021 01 11.
Article in English | MEDLINE | ID: covidwho-914845

ABSTRACT

To circumvent the devastating pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, a humanized decoy antibody (ACE2-Fc fusion protein) was designed to target the interaction between viral spike protein and its cellular receptor, angiotensin-converting enzyme 2 (ACE2). First, we demonstrated that ACE2-Fc could specifically abrogate virus replication by blocking the entry of SARS-CoV-2 spike-expressing pseudotyped virus into both ACE2-expressing lung cells and lung organoids. The impairment of viral entry was not affected by virus variants, since efficient inhibition was also observed in six SARS-CoV-2 clinical strains, including the D614G variants which have been shown to exhibit increased infectivity. The preservation of peptidase activity also enables ACE2-Fc to reduce the angiotensin II-mediated cytokine cascade. Furthermore, this Fc domain of ACE2-Fc was shown to activate NK cell degranulation after co-incubation with Spike-expressing H1975 cells. These promising characteristics potentiate the therapeutic prospects of ACE2-Fc as an effective treatment for COVID-19.


Subject(s)
Antibodies, Monoclonal, Humanized/pharmacology , Antibodies, Viral/pharmacology , COVID-19/prevention & control , SARS-CoV-2/drug effects , Spike Glycoprotein, Coronavirus/immunology , Virus Internalization/drug effects , Angiotensin-Converting Enzyme 2/immunology , Animals , Antibodies, Monoclonal, Humanized/immunology , Antibodies, Viral/immunology , COVID-19/immunology , Chlorocebus aethiops , HEK293 Cells , Host-Pathogen Interactions/drug effects , Humans , Killer Cells, Natural/drug effects , Killer Cells, Natural/immunology , Recombinant Fusion Proteins/immunology , Recombinant Fusion Proteins/pharmacology , SARS-CoV-2/immunology , SARS-CoV-2/physiology , Vero Cells
19.
Arch Virol ; 165(3): 609-618, 2020 Mar.
Article in English | MEDLINE | ID: covidwho-824459

ABSTRACT

Porcine epidemic diarrhea virus (PEDV) targets the intestinal mucosa in pigs. To protect against PEDV invasion, a mucosal vaccine is utilized effectively. In this study, we generated a recombinant adenovirus vaccine encoding the heat-labile enterotoxin B (LTB) and the core neutralizing epitope (COE) of PEDV (rAd-LTB-COE). The fusion protein LTB-COE was successfully expressed by the recombinant adenovirus in HEK293 cells, and the immunogenicity of the vaccine candidate was assessed in BALB/c mice and piglets. Three intramuscular or oral vaccinations with rAd-LTB-COE at two-week intervals induced robust humoral and mucosal immune responses. Moreover, a cell-mediated immune response was promoted in immunized mice, and the neutralizing antibody inhibited both the vaccine strain and the emerging PEDV isolate. Immunization experiments in piglets revealed that rAd-LTB-COE was immunogenic and induced good immune responses in piglets. Further studies are required to evaluate the efficacy of rAd-LTB-COE against a highly virulent PEDV challenge.


Subject(s)
Coronavirus Infections/prevention & control , Coronavirus Infections/veterinary , Porcine epidemic diarrhea virus/immunology , Swine Diseases/prevention & control , Viral Vaccines/immunology , Adenoviridae/genetics , Adenoviridae/immunology , Animals , Cell Line , Coronavirus Infections/immunology , Enterotoxins/genetics , Enterotoxins/immunology , Epitopes/genetics , Epitopes/immunology , Escherichia coli/immunology , Escherichia coli/pathogenicity , Female , HEK293 Cells , Humans , Mice , Mice, Inbred BALB C , Porcine epidemic diarrhea virus/genetics , Recombinant Fusion Proteins/immunology , Swine , Swine Diseases/immunology , Swine Diseases/virology , Viral Vaccines/administration & dosage , Viral Vaccines/therapeutic use
20.
Vaccine ; 38(46): 7205-7212, 2020 10 27.
Article in English | MEDLINE | ID: covidwho-779733

ABSTRACT

The development of an effective vaccine against SARS-CoV-2 is urgently needed. We generated SARS-CoV-2 RBD-Fc fusion protein and evaluated its potency to elicit neutralizing antibody response in mice. RBD-Fc elicited a higher neutralizing antibodies titer than RBD as evaluated by a pseudovirus neutralization assay and a live virus based microneutralization assay. Furthermore, RBD-Fc immunized sera better inhibited cell-cell fusion, as evaluated by a quantitative cell-cell fusion assay. The cell-cell fusion assay results correlated well with the virus neutralization potency and could be used for high-throughput screening of large panels of anti-SARS-CoV-2 antibodies and vaccines without the requirement of live virus infection in BSL3 containment. Moreover, the anti-RBD sera did not enhance the pseudotyped SARS-CoV-2 infection of K562 cells. These results demonstrate that Fc fusion can significantly improve the humoral immune response to recombinant RBD immunogen, and suggest that RBD-Fc could serve as a useful component of effective vaccines against SARS-CoV-2.


Subject(s)
Antibodies, Neutralizing/immunology , Antibodies, Viral/immunology , Coronavirus Infections/prevention & control , Immunoglobulin Fc Fragments/immunology , Pandemics/prevention & control , Pneumonia, Viral/prevention & control , Spike Glycoprotein, Coronavirus/immunology , Viral Vaccines/immunology , Angiotensin-Converting Enzyme 2 , Animals , Antibodies, Neutralizing/blood , Antibodies, Viral/blood , Betacoronavirus/immunology , COVID-19 , COVID-19 Vaccines , Cell Fusion , Cell Line , Coronavirus Infections/immunology , Enzyme-Linked Immunosorbent Assay , Female , HEK293 Cells , High-Throughput Screening Assays/methods , Humans , Immunity, Humoral/immunology , Immunoglobulin Fc Fragments/genetics , Mice , Mice, Inbred BALB C , Neutralization Tests , Peptidyl-Dipeptidase A/genetics , Protein Domains/immunology , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunology , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/genetics , Vaccines, Subunit/immunology
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