Decoding Glycosylation Signatures of Viral Envelope Proteins: From Structural Analysis to Vaccine Development Strategies

Abstract

Glycoproteins incorporated into the viral envelope are critical for virus-host interactions as they mediate viral attachment to cells as well as membrane fusion between the cellular and viral membranes, allowing viral entry into the cell. The exposure of glycoproteins on viral surfaces makes them key targets for the immune system. Despite the biological significance of viral glycoproteins, there is a lack of information regarding their glycan distribution, composition, and immunomodulatory properties. This thesis investigates the glycoprofile of selected viral glycoproteins and the impact of the glycosylation on antibody reactivity and adaptive immune activation, using native and recombinant glycoproteins from tick-borne encephalitis virus (TBEV), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), varicella zoster virus (VZV) and herpes simplex virus type 2 (HSV-2).

We characterized the glycosylation sites and glycoform distribution of both N-linked and O-linked glycans on a key viral envelope glycoprotein from each virus studied. This included the identification of novel O-linked glycans and confirmation of previously reported O- and N-linked glycans. In addition, we analysed convalescent serum samples from previously infected patients to assess antibody reactivity toward glycoproteins with varying glycan profiles, revealing individual differences in B-cell epitope recognition patterns. Lastly immunization with a recombinant form of glycoprotein G from HSV-2 (mgG- 2) showed that its glycans are facilitating protection against neuronal spread and severe disease, and that the recombinant viral glycoprotein show potential as a vaccine candidate due to the ability to elicit strong B- and T-cell responses. To verify this finding, we utilized a murine genital challenge model and showed that neuronal spread of HSV-2 is hampered in a mgG-2 deficient HSV-2 strain.

The data presented in this thesis emphasizes that the development of effective glycoprotein-based vaccines requires a comprehensive understanding of glycosylation patterns, the factors shaping the glycan landscape, and their impact on antigenicity and immunogenicity.