Max Crispin - May 20, 2020

Max Crispin, DPhil, University of Southampton, "Site-specific glycan analysis of the SARS-CoV-2 spike"

Their studies focus on understanding the surface structure of the virus. Viral spike proteins can be extensively glycosylated. Glycosylation occurs in endoplasmic reticulum (ER) and Golgi. The attachment sites are dictated by protein sequence (and hence genome). Ser/Thr-linked or O-linked glycans generally occur in flexible loops. The talk focuses on N-linked glycans. There is a selection pressure for these molecules to fold correctly. The CoV glycans are important for considerations in vaccine design. We can learn about immunogen integrity, processing/trafficking, presentation of glycan-based epitopes and also degree of shielding by the viral glycans from the glycosylation of recombinant spikes. They are interested in studying glycosylation as glycans can influence immunogen trafficking to (for instance) B cells and studying neutralizing antibodies. HIV is antigenically diverse but conserved regions include dense carbohydrates (and resistant to mutations), so antibodies can recognize and penetrate the glycan shield in HIV. In their HIV model, they were able to analyze quantitative site-specific structures and map glycans, which would allow them to study antibodies recognizing the site-specific glycans. Using a similar approach, they did site-specific glycan analysis of the recombinant native-like SARS-CoV-2 spikes. This is followed by LC-MS glycopeptide analysis. When they plot on the surface, they showed the distribution of different glycans (i.e. oligomannose). Then comparing the oligomannose content to different viruses, they are more processed, which is more encouraging for antibody development. In addition, the coronaviruses have lower degree of glycan shielding compared to other viruses. As a future direction, they are interested in understanding the role of glycosylation in pathology and utilizing native-like trimers in serological assays.