Design and delivery of a cryptic PrPC epitope for the induction of a PrPSc-specific antibody response
Transmissible spongiform encephalopathies (TSEs) represent a unique category of diseases known as protein misfolding diseases. Pathogenesis is dependent on the misfolding of normal cellular prion protein (PrPC), which is thought to occur following physical interaction with the infectious conformation PrPSc and a yet unknown cofactor molecule(s). Most common immunotherapeutic strategies involve targeting an immune response against the PrPC protein since evidence has shown that functional membrane-expressed PrPC is an absolute requirement for the development of a prion infection. As of yet, however, the true function of PrPC is not known, therefore, stimulating such an immune response against this widely-expressed cell membrane protein may have harmful consequences. Targeting the PrPSc conformation avoids the potential initiation of an autoimmune response and may circumvent PrPC tolerance mechanisms allowing for a greater Ab mediated immune response; thus representing a safer, and more effective, immunotherapeutic strategy. A weakly immunogenic PrPC epitope (YYR), which induces antibodies specific for the PrPSc conformation, was used as the starting point for the development of a prion vaccine. By optimizing epitope design, as well as vaccine formulation and delivery, immunogenicity was enhanced while PrPSc-specificity was retained. One epitope in particular, QVYYRPVDQYSNQN, when created as a genetic fusion with the leukotoxin carrier molecule, appeared to be an immunogenic vaccine candidate. The immune response following two vaccinations with this construct induced a robust and sustained serum PrPSc-specific IgG antibody response. Specific antibody was also detected in the nasal secretions and cerebral spinal fluid of vaccinated animals. Allowing for the possibility that epitope spreading may occur, resulting in the production of auto-reactive anti-PrPC antibodies, both ELISA and immunoprecipitation experiments were performed and were unable to detect the presence of anti-PrPC antibodies. Altogether the evidence suggests that this epitope may be a good candidate for the development of a TSE vaccine.
DegreeDoctor of Philosophy (Ph.D.)
CommitteeGriebel, Philip; Lee, Jeremy; Warrington, Robert; Roesler, William
Copyright DateSeptember 2011