Cell Surface Glycan Engineering to Examine Receptor Specificities of Influenza and Other Viruses
The transmission of viruses from animal reservoirs to humans poses great threats to public health. Preparedness for future zoonotic outbreaks requires a fundamental understanding how viruses of animal origin have adapted to replication in humans. In particular, it necessitates insight how viruses have evolved to binding to a cell surface component, or receptor, of the new host. We have developed glycan arrays and glycan cell surface engineering strategies to examine receptor specificities of viruses. The approaches were employed to examine receptor specificities of evolutionary distinct A/H3N2 influenza viruses. Recent A/H3N2 influenza viruses exhibit altered receptor specificities, and as a result they have lost the ability to agglutinate erythrocytes critical for antigenic characterization and give low yields and acquire adaptive mutations when cultured in eggs and cells, contributing to recent vaccine challenges. Glycan array technology showed that these viruses have compensated for decreased binding of the prototypic human receptor by recognizing α2,6-sialosides on extended LacNAc moieties. Erythrocyte glycomics showed an absence of extended glycans, providing a rationale for lack of agglutination by recent A/H3N2 viruses. A glycan remodeling approach installed functional receptors on erythrocytes, allowing antigenic characterization of recent A/H3N2 viruses and confirming the cocirculation of antigenically different viruses in humans. Computational studies of HAs in complex with sialosides having extended LacNAc moieties reveal that mutations distal to the RBD reoriented the Y159 side chain, resulting in an extended receptor binding site. The approach was extended to examining the receptor specificity of Lass Virus.