The initial step of the influenza A virus (IAV) infection is the binding of the hemagglutinin (HA) protein to the sialylated host glycans. The HA protein forms trimers, each of the monomers has a relatively conserved receptor binding site (RBS) that functions to engage the virus with the sialylated glycans on the host cells. The binding specificity and the binding affinity of an IAV to the glycan receptors, which can be expressed differentially on different cells and different hosts, are two of the key factors determining the virus cell and host tropisms.  Typically, avian IAV prefers sialic acids (SAs) that are linked to galactose (Gal) by the α2,3-linkage (SA2,3Gal) whereas human IAV binds to terminal SAs with a α2,6-linkage (SA2,6Gal). In this study, we generated a total of 200 mutants targeting the HA RBS of A/California/04/2009(H1N1) and further characterized replication efficiency of these mutants in MDCK cell and chicken embryonated egg. To identify the glycan motifs determining phenotypic diversity of these mutants, we performed virus-glycan binding analyses against 75 glycan isoformers using glycan array. Machine learning analyses showed that increasing the binding ratio of α2-3 sialic acid glycans to α2-6 sialic acid glycans can help expand the receptor spectrometry for IAV binding and that increasing of IAV binding ability to the non-sialic acid glycans can increase virus replication efficiency in both MDCK cells and eggs. In addition, a number of novel glycan substructures and mutations in HA RBS determining IAV tropisms in MDCK cell and chicken embryonated egg were also identified. In summary, the results from this study can be useful in optimization of influenza vaccine seed production and in selecting high yield influenza vaccine strains during surveillance.

Glycan substructures specific for influenza cell and host tropisms

2019 Spring National Meeting

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