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Rational design of structure based vaccines targeting prion diseases
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- Author / Creator
- Fang, Jiarui
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Prion diseases are neurodegenerative disorders that arise from the misfolding of the cellular prion protein (PrPC) into the infectious prion protein (PrPSc), resulting in a conformational change in the protein structure. Despite being extensively studied, high-resolution structural information regarding PrPSc is only beginning to be discovered. While recently resolved structures show PrPSc to contain a parallel‐in‐register intermolecular β‐sheet (PIRIBS) structure, it has also been previously suggested to contain a four-rung β-solenoid (4RβS) structure. No treatment currently exists for any prion diseases and prion prophylactics or vaccines are essentially nonexistent. Prior prion vaccine attempts have minimally considered the structural differences between PrPC and PrPSc, resulting in low to no efficacy when tested in vivo.
A fungal prion protein “HET-s” was shown to contain a two-rung β-solenoid structure. A 4RβS version of HET-s termed “HET-2s’’ was engineered via a linker connecting the prion-forming domain (PFD) of HET-s twice. This mimic acts as a protein scaffold to strategically place prion amino acid residues on its surface and allows us to control for structural differences between PrPC and PrPSc, marking a new approach in amyloid vaccine design.
The protein scaffold was optimized for β-solenoid formation, and several vaccine candidates were designed with proper folding verified via transmission electron microscopy (TEM) to ensure correct epitope exposure. One particular vaccine candidate, “14R1”, produced an immune response in mice that preferentially recognized PrPSc over PrPC. Its efficacy against genetic prion disease was tested in a mouse model of Gerstmann-Sträussler-Scheinker disease (GSS), and it delayed the onset of disease. 14R1 was also tested against peripheral prion infection using hamsters infected with the hyper strain of transmissible mink encephalopathy (TME) (HY), which was less effective. Lastly, its efficacy was also tested in elk naturally exposed to chronic wasting disease (CWD), producing a PrPSc-specific immune response.
A monoclonal antibody derived from 14R1 was created, and was shown to recognize various human and animal prion strains. Its structural epitope was resolved, and this same epitope is presumed to be shared by PrPSc. The effects of immunologic adjuvants combined with 14R1 was also examined, with certain adjuvants giving higher antibody titres over others. The structural stability of 14R1 was also investigated, and it showed that a high salt concentration or lyophilization was required to maintain the structural epitopes as designed.
Taken together, these results show that rationally designed vaccines against prion disease and monoclonal antibodies that are PrPSc-specific are both possible. These results have implications beyond just prion diseases, providing a novel approach to preventing neurodegenerative disorders.
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- Graduation date
- Fall 2022
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.