Abstract
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, wild-type, non-stabilized spikes expressed from a plasmid with a CMV promoter and tPA signal sequence, 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 non-stabilized wild-type spike tested, which may have implications for the resulting immune response and vaccine design.
Highlights
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
Several COVID-19 vaccine candidates are based on viral vectors encoding SARS-CoV-2 S protein, including ChAdOx1 nCoV-19 (AZD1222).[10,11]
After trimerization and initial N-glycan processing in the endoplasmic reticulum (ER) by resident sugar modifying enzymes, membrane anchored S trimers travel to the ER−Golgi intermediate compartment (ERGIC) where they are incorporated into viruses budding into the ERGIC lumen.[13,14]
Summary
From immunogen producing cells is reminiscent of HIV vaccine development, where early immunogens were hampered. Glycosylation at N234 affects the up/down orientation of the RBD domain and ACE-2 binding.[3] Plausibly, enhanced glycan processing on shed S1vaccine‐antigen could negatively affect antibody recognition due to a change in in fundamental ways from antigens present during viral infection, where factors other than a single protein coding sequence may play decisive roles in immunogen presentation (Figure 4) These include the (intra)cellular location of viral morphogenesis (i.e., from which organelle a virus buds), as well as the overall macromolecular assembly of an immunogen as it encounters the host glycosylation machinery during a glycan charge and size Characterizing and understanding the correct glycosylation of the virus, as we have done here, will inform vaccine design strategies and the development of a high-quality immune response, aimed at achieving the correct immunogen presentation, in this and future pandemics
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
