Investigation of host glycan requirements for the transmission of influenza viruses at the human-animal interface

Abstract Influenza A viruses (IAV) pose a constant threat to human health through both seasonal epidemics and occasional pandemics, which are often caused by transmission of IAV strains from zoonotic reservoirs. With the exception of bat IAV, all other IAV strains infect host cells by binding to sialic acid on glycoconjugates (sialoglycans). Various types of cell surface sialoglycans (N-glycans, O-glycans, glycolipids) display significant diversity in both structure and carbohydrate composition. In addition, the sialoglycan repertoire can vary between cell types and across different IAV host species. Thus, defining the structural features in sialoglycans necessary for IAV infection across different host species is critical for our understanding of zoonotic transmission into humans. Importantly, there are no reliable strategies that can comprehensively assess and identify zoonotic IAV strains capable of causing human infections. To define the types of sialoglycans that facilitate IAV infection, we utilized the CRISPR/Cas9 technique and truncated different types of sialoglycans in a human lung epithelial cell line either individually or in combination, by targeting glycosyltransferases essential to biosynthesis. Our studies show that sialic acid on N-glycans, O-glycans and glycolipids can independently serve as a receptor for several IAV strains from both human and zoonotic hosts. Interestingly, truncation of all three types of glycans significantly decreased the replication of human by not avian IAV strains, demonstrating that IAV strains from avian hosts are more flexible in their requirement of sialoglycan structures. Here we propose to utilize the CRISPR/Cas9 technique to define the structural features of sailoglycans necessary for IAV infection and adaptation across various host species using primary differentiated cells. Importantly, we will develop a single cell multi-omics platform to reliably identify zoonotic IAV strains with the potential to cause human infections. These studies will provide significant insights into our understanding of how the sialoglycan repertoire shapes host adaptation and fitness of IAV strains.