DFG Research Unit RU 2327, Teilprojekt: New roles of Glycans in Norovirus infection: From structure to function to inhibition

Our recently established group has a keen interest in the entry process of caliciviruses, focusing on the role of glycans in infection. Caliciviruses infect a variety of host species and binding to distinct glycans constitutes a universal feature of all members of this virus family. Noroviruses, members of the caliciviridae, are responsible for the majority of acute gastroenteritis in humans and a significant global health concern. The ability of human noroviruses to establish infection is linked to the ability of the viral capsid to bind fucosylated glycans related to histo-blood group antigens (HBGA). While this argues for a critical role of HBGAs initiating human norovirus infection, the molecular mechanism of this interaction is not understood. Studying human norovirus infection is challenging because of the lack of a suitable infectious platform. Animal noroviruses like their human counterparts bind distinct glycans but the functional impact of this interaction on infection is still unclear. Murine noroviruses (MNV) are the only noroviruses that can be efficiently cultivated and recapitulate key aspects of human norovirus infection. Furthermore, MNV comes with a broad set of molecular tools, including a reverse genetics system to genetically manipulate the virus, an efficient cell culture system, and a tractable animal model. This makes MNV the model of choice to study norovirus infection. Recent data indicate that MNVs bind both sialylated and fucosylated glycans in vitro. We therefore hypothesize that these glycans play an important role during MNV infection. To test our hypothesis, we will investigate glycan-binding of MNV using biophysical and functional approaches. First, we will obtain detailed information on specificity and dynamics of the MNV-glycan interactions at atomic detail using saturation transfer difference (STD)-NMR spectroscopy and mass spectrometry (MS). Second, we will characterize glycan-binding epitope(s) using high resolution x-ray crystallography and determine the rules of engagement by mutagenesis and functional analysis. Third, using cell-based assays and mice, we will study the impact of glycan-binding on MNV infection. Following this approach, we will not only learn about the entry process of noroviruses and the role of glycans in viral infection in general but also derive possible new targets and antiviral strategies. An overarching objective of this proposal within this research unit is to understand the role and biophysical parameters of glycan-binding in viral infection and to establish a pipeline to develop novel inhibitors of glycan-binding and test their efficacy in vitro and in vivo using the MNV model.