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Site-specific steric control of SARS-CoV-2 spike glycosylation

ABSTRACT: A central tenet in the design of vaccines is the display of native-like antigens in the elicitation of protective immunity. The abundance of N-linked glycans across the SARS-CoV-2 spike protein is a potential source of heterogeneity between the many different vaccine candidates under investigation. Here, we investigate the glycosylation of recombinant SARS-CoV-2 spike proteins from five different laboratories and compare them against infectious virus S protein. We find patterns which are conserved across all samples and this can be associated with site-specific stalling of glycan maturation which act as a highly sensitive reporter of protein structure. Molecular dynamics (MD) simulations of a fully glycosylated spike support s a model of steric restrictions that shape enzymatic processing of the glycans. These results suggest that recombinant spike-based SARS-CoV-2 immunogen glycosylation reproducibly recapitulates signatures of viral glycosylation. https://doi.org/10.1101/2021.03.08.433764 This folder contains the RAW MS files used in the glycopeptide analysis for recombinant SARS proteins from a range of different labs outlined in Figure 1 and 2 and additionally the analysis performed on monomeric RBD

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Max Crispin

PROVIDER: MSV000087308 | MassIVE | Tue Apr 27 04:10:00 BST 2021

REPOSITORIES: MassIVE

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Project description:The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus utilizes an extensively glycosylated spike protein that protrudes from the viral envelope to bind to angiotensin-converting enzyme-related carboxypeptidase (ACE2) as its primary receptor to mediate host-cell entry. Currently, the predominant recombinant spike protein production hosts are Chinese hamster ovary (CHO) and human embryonic kidney (HEK) cells. In this study, recombinant full-size spike protein was produced transiently in CHO and HEK cell suspensions. To further evaluate the sialic acid linkages presenting on spike glycans, a two-step amidation process, employing dimethylamine and ammonium hydroxide reactions in a solid support system, was developed to differentially modify the sialic acid linkages on glycans and glycopeptides from spike protein. We determined global and site-specific N-linked glycosylation patterns in soluble SARS-CoV-2 spike using MALDI-TOF and LC-MS/MS with electron-transfer/higher-energy collision dissociation (EThcD) fragmentation. We identified the glycan compositions at 21 and 19 out of the 22 predicted N-glycosylation sites of the SARS-CoV-2 spike proteins produced in CHO and HEK, respectively. The N-glycan site at 1158 position (N1158) and the N-glycan sites at 122 ,282 and 1158 positions (N122, N282 and N1158) were found to be unoccupied on spike secreted from CHO and HEK cells, respectively. The structural mapping of glycans of recombinant human spike proteins revealed that CHO-Spike presented more complex and higher sialylation (α2,3-linked) content while HEK-Spike displayed more high-mannose and minor content of α2,3- and α2,6-linked sialic acids. The N74 site represents the most heavily N-glycosylated site on both spike proteins while some high-mannose abundant sites (N17, N234, N343, N616, N709, N717, N801 and N1134) on HEK-Spike may differentially shield the virus compared to CHO-spike and provide a different host immune system interaction strategy. Collectively, these data underscore the importance of characterizing site-specific glycosylation on recombinant human spike protein from HEK and CHO cells in order to better understand the impact of the production host on this complex and important protein used in diagnostics and vaccines.

Project description:Despite the clinical success of anti-spike vaccines, the effectiveness of neutralizing antibodies and vaccines by rapidly spreading SARS-CoV-2 variants has been compromised. Viruses can hijack the glycosylation machinery of host cells to shield themselves from the host’s immune response and attenuate antibody efficiency. However, it still remains unclear whether targeting glycosylation on spike can impair SARS-CoV-2 and its variants infectivity. Methods: To assess the binding ability of glycosylated or deglycosylated spike with ACE2, we performed flow cytometry, ELISA, and BioLayer Interferometry methods. Viral entry ability was determined by luciferase intensity, immunoblotting, and immunofluorescence assay. A genome-wide association study (GWAS) was performed to identify the relationship of STT3A and COVID-19 severity. N-glycosylation regulated by NF-kB/STT3A axis was investigated by knockdown approach, chromatin immunoprecipitation, and promoter assay. To specifically target SARS-CoV-2 infected cells, we developed an antibody-drug conjugate coupling non-neutralization anti-spike antibody with NGI-1 (4G10-ADC) on inhibitory effects of SARS-CoV-2 infection. Results: We found receptor binding domain and three SARS-CoV-2 distinct surface Nglycosylation sites in 57,311 spikes retrieved from NCBI-Virus-database are highly evolutionarily conserved (99.67%) and involved in ACE2 interaction. We further identified STT3A as a key glycosyltransferase that catalyzed spike glycosylation and positively correlated with COVID-19 severity. Inhibition of STT3A by N-linked glycosylation inhibitor-1 (NGI-1) impaired SARS-CoV-2 and its variants (B.1.1.7, and B.1.351) infectivity. Most importantly, 4G10-ADC internalized SARS-CoV-2 infected cells and subsequently released NGI-1 to deglycosylate spike protein. Thereby, it reinforces the neutralizing abilities in antibodies, vaccines, or convalescent sera, inhibiting SARS-CoV-2 and its variants’ infectivity. Our results suggest targeting STT3A-mediated evolution conserved glycosylation via ADC can provide a widespread impact on SARS-CoV-2 variants infection. Together, we identified a novel deglycosylation method to eradicate SARS-CoV-2 variants infection.

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Site-specific steric control of SARS-CoV-2 spike glycosylation

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