SARS-CoV-2 spike protein arrested in the closed state induces potent neutralizing responses

Abstract

The majority of SARS-CoV-2 vaccines in use or in advanced clinical development are based on the viral spike protein (S) as their immunogen. S is present on virions as pre-fusion trimers in which the receptor binding domain (RBD) is stochastically open or closed. Neutralizing antibodies have been described that act against both open and closed conformations. The long-term success of vaccination strategies will depend upon inducing antibodies that provide long-lasting broad immunity against evolving, circulating SARS-CoV-2 strains, while avoiding the risk of antibody dependent enhancement as observed with other Coronavirus vaccines. Here we have assessed the results of immunization in a mouse model using an S protein trimer that is arrested in the closed state to prevent exposure of the receptor binding site and therefore interaction with the receptor. We compared this with a range of other modified S protein constructs, including representatives used in current vaccines. We found that all trimeric S proteins induce a long-lived, strongly neutralizing antibody response as well as T-cell responses. Notably, the protein binding properties of sera induced by the closed spike differed from those induced by standard S protein constructs. Closed S proteins induced more potent neutralising responses than expected based on the degree to which they inhibit interactions between the RBD and ACE2. These observations suggest that closed spikes recruit different, but equally potent, virus-inhibiting immune responses than open spikes, and that this is likely to include neutralizing antibodies against conformational epitopes present in the closed conformation. Together with their improved stability and storage properties we suggest that closed spikes may be a valuable component of refined, next-generation vaccines.

SARS-CoV-2 Spike protein binding of glycated serum albumin - its potential role in the pathogenesis of the COVID-19 clinical syndromes and bias towards individuals with pre-diabetes/type 2 diabetes & metabolic diseases

“…The viral Spike protein (S-protein) is present on virions as a pre-fusion trimers with the receptor binding domain of the S1 region stochastically open or closed, an intermediary where the S1 region is cleaved and discarded, and the S2 undergoes major confirmation changes to expose and then retract its fusion peptide domain [17]. Here the S-protein was modified to disable the S1/S2 cleavage site and maintain the pre-fusion stochastic confirmation [18].…”

“…where the S1 region is cleaved and discarded, and the S2 undergoes major confirmation changes to expose and then retract its fusion peptide domain [17]. Here the S-protein was modified to disable the S1/S2 cleavage site and maintain the pre-fusion stochastic confirmation [18].…”

SARS-CoV-2 Spike Protein Binding of Glycated Serum Albumin—Its Potential Role in the Pathogenesis of the COVID-19 Clinical Syndromes and Bias towards Individuals with Pre-Diabetes/Type 2 Diabetes and Metabolic Diseases

“…The viral spike protein (S protein) is present on virions as a pre-fusion trimer with the receptor-binding domain of the stochastically open or closed S1 region, an intermediary where the S1 region is cleaved and discarded, and S2 undergoes major conformational changes to expose and then retract its fusion peptide domain [32]. Here, the S protein was modified to disable the S1/S2 cleavage site and maintain the pre-fusion stochastic conformation [33]. Protein-G-coupled magnetic beads were purchased from Cytivia Ltd. (Amersham Place, Little Chalfont, Buckinghamshire, UK).…”

Determination of IgG1 and IgG3 SARS-CoV-2 spike protein and nucleocapsid binding – Who is binding who and why?

“…The viral spike protein (S-protein) is present on virions as a pre-fusion trimers with the receptor binding domain of the S1 region stochastically open or closed, an intermediary where the S1 region is cleaved and discarded, and the S2 undergoes major confirmation changes to expose and then retract its fusion peptide domain [14]. Here the S-protein was modified to disable the S1/S2 cleavage site and maintain the pre-fusion stochastic confirmation [15].…”