Glycobiology studies of influenza virus

Abstract

Glycans represent a class of macromolecules that exhibit vital biological roles in living organisms. They are not only essential for maintaining the normal functionalities of a cell, but are also involved in many pathogenic processes. The influenza A virus binds to glycan receptors that are expressed on the surface of respiratory epithelial cells of human airway and thereby initiates infection. Deciphering the structural features of glycans and comprehending their functional implications are thus crucial to expand our understandings of the disease. To validate the alternative models that are used in the studies of influenza, we generated the glycomic profiles from in vivo and in vitro experimental systems by mass spectrometry. A combination of MALDI-TOF MS, MALDI-TOF-TOF MS/MS, GC-EI-MS and enzymatic digestion experiments were utilised to characterise the structure of glycans. The ferret has been used as an experimental animal to investigate the transmission and replication of influenza viruses. To verify the validity of this model, we carried out glycomic characterisation of ferret respiratory tissues to complement the data that was generated from human airway tissues. The mass spectrometric analysis indicates that the respiratory glycosylation of ferret highly resembles that of human, although distinctive expression of glycans displaying the Sda epitope are detected exclusively in ferret. Nonetheless, in comparison to other lab animals such as mouse and swine, ferret remains a better alternative model for studying the pathogenicity of influenza viruses. In the second project, we generated the glycomic profiles from human and ferret respiratory epithelial cells that were cultured under experimental conditions. Glycosylation patterns between these two in vitro systems are largely comparable, except the presence of the Sda epitope in ferret cells. However, when compared to their corresponding in vivo tissues, diminished structural repertoires especially the high-mass structures were observed.