Synthetic glycolipids to investigate the interactome of viral glycan-binding proteins

Pandemic RNA-based viruses such as SARS-CoV2 and influenza A strains are associated with a varying mutational burden to evade attack by components of the adaptive immune system. Their often rapidly evolving nature has made these viruses challenging targets for vaccine development: influenza vaccines have to be updated annually, and new SARS-CoV2 strains with impaired efficacy of neutralizing antisera are emerging. Being produced by human host cells, these viruses are highly glycosylated on Asn-Xaa-Ser/Thr sequons (e.g. 22 for SARS-Cov2 Spike). Addition or ablation of glycosylation sites is considerably slower than the antigenic drift of peptide sequences, with some glycans being essential for virus entry. Given that a large part of the surface of viral glycoproteins is covered by glycans, glycopeptides are likely to be important targets for antibody recognition. For instance, a neutralizing antibody recognizing a conserved glycopeptide epitope on coronaviruses including SARS-CoV2 was found serendipidously by cryo-electron microscopy. The epitope occupies a large 300 Å2 surface but crucially relies on the presence of the glycan. However, the field is currently lacking diagnostic technologies to profile immune responses against defined glycopeptides simply because these probes are much less straightforward to synthesise and immobilize than non-glycosylated peptides. At the same time, assessing the capability of sera from infected or vaccinated individuals to neutralise infection relies on cumbersome, low-throughput cell culture experiments. We hypothesise that antibodies against viral glycopeptides play a crucial role for neutralisation. This project will leverage the potential of synthetic glycopeptides to develop targeted diagnostics that profile the neutralising capacity of patient sera against respiratory viruses, with SARS-CoV2 as a case study. We will develop a method to append photo-switchable lipid tags to synthetic glycans. Photoswitches will be designed to enable binding experiments by glycan microarray analysis. This physical sciences innovation will allow us to cover a large structural space, as different orientations of glycans can be probed. Thereby, our data will feed into the generation of diagnostic devices and optimized vaccine antigens that should be much more resistant towards antigenic drift than pure peptide epitopes.