There is compelling evidence [7] that, according to the “protein-only” hypothesis [8], TSE are caused by the conversion of normal mammalian prion protein (PrPc) into its pathological conformation, or scrapie-associated prion protein (PrPSc), which is abnormally folded, β-sheet enriched and protease resistant [9]. Here, PRNP is linked to human prion disease.