Receptor Specificity of Influenza A H3N2 Viruses Isolated in Mammalian Cells and Embryonated Chicken Eggs

Isolation of human subtype H3N2 influenza viruses in embryonated chicken eggs yields viruses with amino acid substitutions in the hemagglutinin (HA) that often affect binding to sialic acid receptors. We used a glycan array approach to analyze the repertoire of sialylated glycans recognized by viruses from the same clinical specimen isolated in eggs or cell cultures. The binding profiles of whole virions to 85 sialoglycans on the microarray allowed the categorization of cell isolates into two groups. Group 1 cell isolates displayed binding to a restricted set of alpha 2-6 and alpha 2-3 sialoglycans, whereas group 2 cell isolates revealed receptor specificity broader than that of their egg counterparts. Egg isolates from group 1 showed binding specificities similar to those of cell isolates, whereas group 2 egg isolates showed a significantly reduced binding to alpha 2-6- and alpha 2-3-type receptors but retained substantial binding to specific O- and N-linked alpha 2-3 glycans, including alpha 2-3GalNAc and fucosylated alpha 2-3 glycans (including sialyl Lewis x), both of which may be important receptors for H3N2 virus replication in eggs. These results revealed an unexpected diversity in receptor binding specificities among recent H3N2 viruses, with distinct patterns of amino acid substitution in the HA occurring upon isolation and/or propagation in eggs. These findings also suggest that clinical specimens containing viruses with group 1-like receptor binding profiles would be less prone to undergoing receptor binding or antigenic changes upon isolation in eggs. Screening cell isolates for appropriate receptor binding properties might help focus efforts to isolate the most suitable viruses in eggs for production of antigenically well-matched influenza vaccines.