PhD defence
Usutu too? Insights into vaccine development strategies for an emerging orthoflavivirus
- J.M. Duyvestyn
- Date
- Thursday 15 January 2026
- Time
- Location
-
Academy Building
Rapenburg 73
2311 GJ Leiden
Supervisor(s)
- Prof.dr. E.J. Snijder
- dr.ir. M. Kikkert
- dr. M.J. van Hemert
Summary
Despite major progress against infectious diseases, the world remains vulnerable to emerging viruses - including those spread by mosquitoes such as dengue, Zika, and yellow fever. Globalisation and climate change are expanding the range of such viruses, increasing their burden on human and animal health. This thesis focuses on Usutu virus (USUV), a lesser-known mosquito-borne orthoflavivirus that originated in Africa and has now become established across Europe. USUV causes fatal disease in birds and occasionally neurological illness in humans.
This work contributes to the One Health PACT consortium, which unites experts in virology, mosquito biology, ecology, and data science to improve detection and response to mosquito-borne viruses in the Netherlands. This thesis focusses specifically on improving our understanding of the pathogenicity of USUV, providing tools and models to study this virus, and developing vaccine strategies to strengthen preparedness against furture outbreaks.
Recombinant DNA clones for two USUV isolates were developed to allow precise genome editing of the virus. A lethal mouse model was also optimised, providing a reliable system to study disease severity. Two vaccine approaches were then explored: (1) rationally designed attenuated viruses, created by introducing theoretically weakening mutations, and (2) chimeric viruses, replacing yellow fever virus surface proteins with those from USUV. The findings from both these projects highlight some key challenges for USUV vaccine design.
The final discussion reflects on broader vaccine development needs - ethical research models, universal orthoflavivirus vaccines, and improved coordination across scientific and policy domains - to better prepare for future outbreaks.
PhD dissertations
Approximately one week after the defence, PhD dissertations by Leiden PhD students are available digitally through the Leiden Repository, that offers free access to these PhD dissertations. Please note that in some cases a dissertation may be under embargo temporarily and access to its full-text version will only be granted later.
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General information
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