Prion diseases are rare fatal neurodegenerative diseases of humans and animals which are transmissible by exposure to diseased tissues via ingestion, injection or transplantation. These diseases are often characterized by spongiform degeneration or vacuolation of gray matter, astrogliosis and microgliosis, and deposition of a partially proteinase K-resistant disease-associated form of the normal host prion protein (PrP) [5, 24]. The disease-related PrP, known as PrP scrapie (PrPSc), is generated by a seeded conversion mechanism where small aggregates of PrPSc bind normal PrP and mediate its conversion to PrPSc .