Single‐dose immunisation with a multimerised SARS‐CoV‐2 receptor binding domain (RBD) induces an enhanced and protective response in mice

Abstract

The COVID-19 pandemic, caused by the SARS-CoV-2 coronavirus, has triggered a worldwide health emergency. Here, we show that ferritin-like Dps from hyperthermophilic Sulfolobus islandicus, covalently coupled with SARS-CoV-2 antigens via the SpyCatcher system, forms stable multivalent dodecameric vaccine nanoparticles that remain intact even after lyophilisation. Immunisation experiments in mice demonstrated that the SARS-CoV-2 receptor binding domain (RBD) coupled to Dps (RBD-S-Dps) elicited a higher antibody titre and an enhanced neutralising antibody response compared to monomeric RBD. A single immunisation with RBD-S-Dps completely protected hACE2-expressing mice from serious illness and led to viral clearance from the lungs upon SARS-CoV-2 infection. Our data highlight that multimerised SARS-CoV-2 subunit vaccines are a highly efficacious modality, particularly when combined with an ultrastable scaffold.

Natural and Experimental SARS-CoV-2 Infection in Domestic and Wild Animals

“…Together, the combination of multiple transgenic hACE2-expressing mouse models under various promoters, adenovirus-based methods for transduction of multiple mouse strains with hACE2, mouse-adapted SARS-CoV-2 strains, and the susceptibility of mice to emerging VOC has resulted in laboratory mice becoming highly useful models for SARS-CoV-2 infection studies and efficacy testing of vaccines and therapeutics [ 220 , 221 , 222 , 223 , 224 ].…”

A Novel Bacterial Protease Inhibitor Adjuvant in RBD-Based COVID-19 Vaccine Formulations Containing Alum Increases Neutralizing Antibodies, Specific Germinal Center B Cells and Confers Protection Against SARS-CoV-2 Infection in Mice

“…Different cell types have been used to produce RBD antigens, such as yeast, plant, and insect cells (33,(41)(42)(43)(44). However, production in mammalian cells (12,(45)(46)(47)(48)(49) may produce an RBD antigenic domain that more closely resembles that generated during virus infection in human cells (including post-translational modifications such as glycosylation and correct folding) (50). Our results showing binding to hACE2expressing cells and the induction of neutralizing antibody titers confirm the preservation of the RBD structure and the suitable exposition of the receptor binding motif (RBM).…”

“…While RBD+alum induces significant immune responses, it has been suggested that its immunogenicity should be increased. Different approaches have been proposed to increase its immunogenicity, such as (i) expression as dimer ( 43 , 49 , 65 , 67 ) or trimers ( 45 ), (ii) fusion to carrier proteins like human IgG Fc moiety ( 44 , 67 ), tetanus toxoid ( 12 ), and interferon-α ( 67 ), (iii) addition of pan HLA-DR-binding epitope to enhance helper T cell responses ( 67 ), (iv) using nanoparticles as delivery system ( 42 , 46 , 48 , 53 , 59 ), or (v) addition of immunopotentiators as CpG ( 42 , 43 , 47 , 59 ), MPLA ( 44 ), 3M-052, or a TLR-7/8 agonist ( 45 , 59 ). Here, we demonstrated that the addition of U-Omp19 to RBD + alum formulation was able to increase the induction and breadth of SARS-CoV-2 neutralizing antibody responses, increase the frequency of RBD-specific germinal center B cells, and induce antigen-specific Th1 and CD8 + T cells.…”

A novel bacterial protease inhibitor adjuvant in RBD-based COVID-19 vaccine formulations increases neutralizing antibodies, specific germinal center B cells and confers protection against SARS-CoV-2 infection

“…The copyright holder for this preprint this version posted December 9, 2021. ; https://doi.org/10.1101/2021.12.07.471590 doi: bioRxiv preprint Different cell types have been used to produce RBD antigens, such as yeast, plant and insect cells 32,[40][41][42][43] . However, production in mammalian cells 11,[44][45][46][47][48] may produce a RBD antigenic domain that more closely resembles that generated during virus infection in human cells (including post-translational modifications such as glycosylation and correct folding) 49 . Our results showing binding to hACE2 expressing cells and the induction of neutralizing antibody titers confirm the preservation of the RBD structure and the suitable exposition of the receptor binding motif (RBM).…”

“…While RBD+Alum induces significant immune responses, it has been suggested that its immunogenicity should be increased. Different approaches have been proposed to increase its immunogenicity, such as i) expression as dimer 42,48,65,67 or trimers 44 , ii) fusion to carrier proteins like human IgG Fc moiety 43,67 , tetanus toxoid 11 , interferon-α 67 , iii) addition of pan HLA-DR-binding epitope to enhance helper T cell responses 67 , iv) using nanoparticles as delivery system 41,45,47,52,59 or v) addition of immunopotentiators as CpG 41,42,46,59 , MPLA 43 , 3M-052 or a TLR-7/8 agonist 44,59 .…”