Assessing Antigen Structural Integrity through Glycosylation Analysis of the SARS-CoV-2 Viral Spike
Brun J., VASILJEVIC S., GANGADHARAN B., HENSEN M., Chandran A., HILL M., KIAPPES J., Dwek R., ALONZI D., STRUWE W., ZITZMANN N.
Severe acute respiratory syndrome coronavirus 2 is the causative pathogen of the COVID-19 pandemic which as of March 29, 2021, has claimed 2 776 175 lives worldwide. Vaccine development efforts focus on the viral trimeric spike glycoprotein as the main target of the humoral immune response. Viral spikes carry glycans that facilitate immune evasion by shielding specific protein epitopes from antibody neutralization, and antigen efficacy is influenced by spike glycoprotein production in vivo. Therefore, immunogen integrity is important for glycoprotein-based vaccine candidates. Here, we show how site-specific glycosylation differs between virus-derived spikes, spike proteins derived from a construct similar to a SARS-CoV-2 vaccine candidate, and commonly used recombinant, engineered spike glycoproteins. Furthermore, we show that their distinctive cellular secretion pathways result in different protein glycosylation and secretion patterns, including shedding of spike monomeric subunits for the vaccine candidate tested, which may have implications for the resulting immune response and vaccine design.