Fig. 1: Computational analysis of PNGS and non-glycosylation related mutations in H3 viruses over time.

A Schematic representation highlighting HA domains: head (blue), RBS (burgundy), RBS proximal regions (salmon), vestigial esterase subdomain (pink) and stem (yellow). B Stacked graph showing the frequency of each PNGS within circulating strains from 1968 to 2022. This analysis includes ~ 11,000 sequences, which were downloaded from the influenza research database NCBI Virus⁶⁷. Supplementary Table 1 contains the frequency of all PNGS over time. C HA structural domains represented on HK/68 (PDB ID: 4FNK). HK/68 glycans are highlighted in red and Sing/16 glycans in cyan. All residues on HA are named according to H3 consensus numbering A/Aichi/1968. D Residue conservation of HK/68 and Sing/16 using ~ 11,000 sequences from the influenza research database projected as a colormap on the HA structure. Glycans are highlighted in blue. E HA residues with distinct amino acid identities between HK/68 and Sing/16 H3N2 strains are depicted as brown spheres on a single protomer of the HK/68 HA trimer (PDB ID: 4FNK). F Mutations appearing in H3 viruses at the same time as the emergence of new PNGS. The different structural regions of HA are highlighted in brown, salmon, pink and blue for globular head, RBS, vestigial esterase and stem regions, respectively.