1. An Engineered Receptor-Binding Domain Improves the Immunogenicity of Multivalent SARS-CoV-2 Vaccines.
- Author
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Guo Y, He W, Mou H, Zhang L, Chang J, Peng S, Ojha A, Tavora R, Parcells MS, Luo G, Li W, Zhong G, Choe H, Farzan M, and Quinlan BD
- Subjects
- Angiotensin-Converting Enzyme 2 immunology, Animals, Binding Sites, COVID-19 Vaccines chemistry, Female, Genetic Engineering, Glycosylation, HEK293 Cells, Humans, Mice, Mice, Inbred BALB C, Models, Molecular, Protein Domains, Rats, Rats, Sprague-Dawley, Receptors, Coronavirus immunology, Spike Glycoprotein, Coronavirus genetics, Spike Glycoprotein, Coronavirus immunology, Vaccines, Conjugate genetics, Vaccines, Conjugate immunology, Vaccines, Synthetic chemistry, Vaccines, Synthetic immunology, Angiotensin-Converting Enzyme 2 genetics, COVID-19 Vaccines immunology, Immunogenicity, Vaccine, Receptors, Coronavirus genetics
- Abstract
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein mediates viral entry into cells expressing angiotensin-converting enzyme 2 (ACE2). The S protein engages ACE2 through its receptor-binding domain (RBD), an independently folded 197-amino-acid fragment of the 1,273-amino-acid S-protein protomer. The RBD is the primary SARS-CoV-2 neutralizing epitope and a critical target of any SARS-CoV-2 vaccine. Here, we show that this RBD conjugated to each of two carrier proteins elicited more potent neutralizing responses in immunized rodents than did a similarly conjugated proline-stabilized S-protein ectodomain. Nonetheless, the native RBD is expressed inefficiently, limiting its usefulness as a vaccine antigen. However, we show that an RBD engineered with four novel glycosylation sites (gRBD) is expressed markedly more efficiently and generates a more potent neutralizing responses as a DNA vaccine antigen than the wild-type RBD or the full-length S protein, especially when fused to multivalent carriers, such as a Helicobacter pylori ferritin 24-mer. Further, gRBD is more immunogenic than the wild-type RBD when administered as a subunit protein vaccine. Our data suggest that multivalent gRBD antigens can reduce costs and doses, and improve the immunogenicity, of all major classes of SARS-CoV-2 vaccines. IMPORTANCE All available vaccines for coronavirus disease 2019 (COVID-19) express or deliver the full-length SARS-CoV-2 spike (S) protein. We show that this antigen is not optimal, consistent with observations that the vast majority of the neutralizing response to the virus is focused on the S-protein receptor-binding domain (RBD). However, this RBD is not expressed well as an independent domain, especially when expressed as a fusion protein with a multivalent scaffold. We therefore engineered a more highly expressed form of the SARS-CoV-2 RBD by introducing four glycosylation sites into a face of the RBD normally occluded in the full S protein. We show that this engineered protein, gRBD, is more immunogenic than the wild-type RBD or the full-length S protein in both genetic and protein-delivered vaccines., (Copyright © 2021 Guo et al.)
- Published
- 2021
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