Avian influenza A viruses exhibit plasticity in sialylglycoconjugate receptor usage in human lung cells.

It is well known that influenza A viruses (IAV) initiate host cell infection by binding to sialic acid, a sugar molecule present at the ends of various sugar chains called glycoconjugates. These sugar chains can vary in chain length, structure, and composition. However, it remains unknown if IAV strains preferentially bind to sialic acid on specific glycoconjugate type(s) for host cell infection. Here, we utilized CRISPR gene editing to abolish sialic acid on different glycoconjugate types in human lung cells, and evaluated human versus avian IAV infections. Our studies show that both human and avian IAV strains can infect human lung cells by utilizing any of the three major sialic acid-containing glycoconjugate types, specifically N-glycans, O-glycans, and glycolipids. Interestingly, simultaneous elimination of sialic acid on all three major glycoconjugate types in human lung cells dramatically decreased human IAV infection, yet had little effect on avian IAV infection. These studies show that avian IAV strains effectively utilize other less prevalent glycoconjugates for infection, whereas human IAV strains rely on a limited repertoire of glycoconjugate types. The remarkable ability of avian IAV strains to utilize diverse glycoconjugate types may allow for easy transmission into new host species.