N-Glycans as Receptors for Influenza A Viruses

Abstract

The influenza virus has created a major burden for human health throughout the last centuries. Seasonal epidemics and reoccurring pandemics continuously infect a substantial percentage of the global population, making influenza one of the most devastating infectious diseases for humans. In Chapter 1, the introduction, the reader is familiarized with the influenza A virus, its impact on humans and its structure. The focus of the introduction is laid on receptors for influenza A, the molecules crucial for initiating viral attachment to the host cell and facilitating the infection by the virus. The research described in this dissertation deals with the role of N-glycans as receptors for the influenza A virus. More specifically, selected structural elements of N-glycans were analyzed and it was investigated how they affect influenza A binding. In Chapter 2, the focus is on N-glycolylneuraminic acid, a sialic acid modification that is common in several mammalian species and has not been studied extensively thus far. In chapter 3 and 4, the focus is shifted towards another structural element, LacNAc units. Despite their ubiquitous occurrence in N-glycans (and other cell surface glycans), there are only a few studies that attempt to comprehensively investigate their impact on viral binding. Therefore, Chapter 3 of this dissertation is dedicated to the development of a suitable glycan microarray platform that can facilitate achieving this goal. While analyzing binding preferences of different viruses to specific structures is essential to explain infectivity and pathogenesis, it is equally important to confirm their presence on relevant tissues. This is the focus of Chapter 4, in which a glycomic analysis of erythrocytes from various animal species is presented. Applying a mass spectrometry-based method, the extent of LacNAc repeating units on N-glycans on these cells was analyzed. The knowledge obtained from Chapters 3 and 4 is turned into practice in Chapter 5. Here, the evolution of A/H3N2 receptor specificity is studied in detail on N-glycans and a glycan remodeling approach to install suitable N-glycan receptors on erythrocytes was developed. These remodeled erythrocytes facilitated the antigenic analysis of contemporary influenza A/H3N2 viruses by the standard hemagglutination inhibition assay and thereby provided a solution for the challenging characterization of these viruses.