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Enhanced stability of the SARS CoV-2 spike glycoprotein following modification of an alanine cavity in the protein core.

Authors :
Pantelis Poumbourios
Christine Langer
Irene Boo
Tasnim Zakir
Rob J Center
Anouschka Akerman
Vanessa Milogiannakis
Anupriya Aggarwal
Bronte A Johnstone
Jungmin Ha
Fasséli Coulibaly
Stuart G Turville
Heidi E Drummer
Source :
PLoS Pathogens, Vol 19, Iss 5, p e1010981 (2023)
Publication Year :
2023
Publisher :
Public Library of Science (PLoS), 2023.

Abstract

The spike (S) glycoprotein of SARS CoV-2 is the target of neutralizing antibodies (NAbs) that are crucial for vaccine effectiveness. The S1 subunit binds ACE2 while the S2 subunit mediates virus-cell membrane fusion. S2 is a class I fusion glycoprotein subunit and contains a central coiled coil that acts as a scaffold for the conformational changes associated with fusion function. The coiled coil of S2 is unusual in that the 3-4 repeat of inward-facing positions are mostly occupied by polar residues that mediate few inter-helical contacts in the prefusion trimer. We examined how insertion of bulkier hydrophobic residues (Val, Leu, Ile, Phe) to fill a cavity next to Ala1016 and Ala1020 in the 3-4 repeat affects the stability and antigenicity of S trimers. Substitution of Ala1016 with bulkier hydrophobic residues in the context of a prefusion-stabilized S trimer, S2P-FHA, was associated with increased thermal stability. S glycoprotein membrane fusion function was retained with Ala1016/Ala1020 cavity-filling mutations associated with improved recombinant S2P-FHA thermostability, however 2 mutants, A1016L and A1016V/A1020I, lacked ability to mediate entry of S-HIV-1 pseudoparticles into 293-ACE2 cells. When assessed as immunogens, two thermostable S2P-FHA mutants derived from the ancestral isolate, A1016L (16L) and A1016V/A1020I (VI) elicited neutralizing antibody with 50%-inhibitory dilutions (ID50s) in the range 2,700-5,110 for ancestral and Delta-derived viruses, and 210-1,744 for Omicron BA.1. The antigens elicited antibody specificities directed to the receptor-binding domain (RBD), N-terminal domain (NTD), fusion peptide and stem region of S2. The VI mutation enabled the production of intrinsically stable Omicron BA.1 and Omicron BA.4/5 S2P-FHA-like ectodomain oligomers in the absence of an external trimerization motif (T4 foldon), thus representing an alternative approach for stabilizing oligomeric S glycoprotein vaccines.

Details

Language :
English
ISSN :
15537366 and 15537374
Volume :
19
Issue :
5
Database :
Directory of Open Access Journals
Journal :
PLoS Pathogens
Publication Type :
Academic Journal
Accession number :
edsdoj.6d3cf0974e2e42daa96111a1d687d350
Document Type :
article
Full Text :
https://doi.org/10.1371/journal.ppat.1010981