Glycan remodeled erythrocytes facilitate antigenic characterization of recent A/H3N2 influenza viruses

Abstract

During circulation in humans and natural selection to escape antibody recognition for decades, A/H3N2 influenza viruses emerged with altered receptor specificities. These viruses 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. Examination of receptor specificities of A/H3N2 viruses reveals that recent viruses compensated for decreased binding of the prototypic human receptor by recognizing α2,6-sialosides on extended LacNAc moieties. Erythrocyte glycomics shows an absence of extended glycans providing a rationale for lack of agglutination by recent A/H3N2 viruses. A glycan remodeling approach installing functional receptors on erythrocytes, allows antigenic characterization of recent A/H3N2 viruses confirming the cocirculation of antigenically different viruses in humans. Computational analysis of HAs in complex with sialosides having extended LacNAc moieties reveals that mutations distal to the RBD reoriented the Y159 side chain resulting in an extended receptor binding site.

Here, Broszeit et al. show that circulating A/H3N2 viruses have evolved binding specificity to α2,6-sialosides on extended LacNAc moieties and therefore cannot agglutinate erythrocytes. Applying glycan remodeling allows to install functional receptors on erythrocytes and promotes identification of newly circulating variants to facilitate vaccine design.