Unraveling the molecular mechanisms of herpes simplex virus attachment and release using cell membrane mimics

Doctoral thesis, 2018

The herpes simplex virus is a widespread human pathogen, most commonly known for causing cold sores. Its infection cycle is initiated with the formation of multiple bonds between viral glycoproteins and cellular glycosaminoglycans, which are long polysaccharide chains found close to the cell surface. While the key molecular actors of this initial attachment have been identified, less is known about the dynamics of the herpes-glycosaminoglycan interaction.

This thesis focuses on implementing bioanalytical assays to address two main research questions. First, we investigated how specific physicochemical properties of the glycosaminoglycan chains and of the viral glycoproteins influence the binding characteristics of the virus, in particular particle mobility and binding kinetics. Second, we aimed at elucidating how new progeny virus successfully releases from the cell membrane without getting trapped. To this end, we used two different cell membrane mimics. The first one consisted of end-grafted glycosaminoglycan chains, mimicking the native brush-like architecture of glycosaminoglycans, while the second one was obtained through incorporation of native membrane material into supported lipid bilayers. To study virus mobility and measure affinities and binding forces, we mainly used total internal reflection fluorescence microscopy in combination with single particle tracking, and atomic force microscopy.

Our results showed that the type of GAG or the glycosylation of the viral glycoproteins influence the diffusive behavior of herpes simplex virions, which we attributed to a change in binding forces of the herpes-glycosaminoglycan interaction. Furthermore, we suggest that a highly glycosylated region, called mucin-like region, found on certain glycoproteins balances the herpes-glycosaminoglycan interaction to ensure successful release.

Taken together, this thesis provides new insights into the mechanisms regulating attachment and release of the herpes simplex virus to and from the cell membrane, which could be of relevance to the development of new strategies in antiviral research.