Unravelling the Role of O-glycans in Influenza A Virus Infection

TLDR

Influenza A virus initiates infection by hemagglutinin binding to cell‑surface glycans, with established preference for sialylated Galβ(1,4)Glc/GlcNAc linked α2,6 or α2,3 residues, yet the contribution of sialylated Galβ(1,3)GalNAc core‑1 O‑glycans remains poorly understood. The study aims to determine whether influenza A viruses can engage sialyl‑Galβ(1,3)GalNAc O‑glycoforms for cell attachment. This was investigated through a multidisciplinary approach combining NMR spectroscopy, virus neutralization assays, and molecular modelling. Our results show that H5N1‑derived VLPs exploit the GalNAc residue of sialylated Galβ(1,3)GalNAc O‑glycans via an EQTKLY motif in HPAI strains, while pandemic H1N1 viruses prefer avian‑like α2,3 linkages on these glycans without relying on GalNAc, indicating that core‑1 O‑glycans play a key role in the influenza A virus life cycle, especially for highly pathogenic avian strains.

Abstract

Abstract The initial stage of host cell infection by influenza A viruses (IAV) is mediated through interaction of the viral haemagglutinin (HA) with cell surface glycans. The binding requirement of IAVs for Galβ(1,4)Glc/ GlcNAc (lactose/lactosamine) glycans with a terminal α(2,6)-linked (human receptors) or α(2,3)-linked (avian receptors) N -acetylneuraminic residue commonly found on N -glycans, is well-established. However the role and significance of sialylated Galβ(1,3)GalNAc (core 1) epitopes that are typical O -glycoforms in influenza virus pathogenesis remains poorly detailed. Here we report a multidisciplinary study using NMR spectroscopy, virus neutralization assays and molecular modelling, into the potential for IAV to engage sialyl-Galβ(1,3)GalNAc O -glycoforms for cell attachment. H5 containing virus like particles (VLPs) derived from an H5N1 avian IAV strain show a significant involvement of the O -glycan-specific GalNAc residue, coordinated by a EQTKLY motif conserved in highly pathogenic avian influenza (HPAI) strains. Notably, human pandemic H1N1 influenza viruses shift the preference from ‘human-like’ α(2,6)-linkages in sialylated Galβ(1,4)Glc/GlcNAc fragments to ‘avian-like’ α(2,3)-linkages in sialylated Galβ(1,3)GalNAc without involvement of the GalNAc residue. Overall, our study suggests that sialylated Galβ(1,3)GalNAc as O -glycan core 1 glycoforms are involved in the influenza A virus life cycle and play a particularly crucial role during infection of HPAI strains.