Prion consists of

Prion is an abnormal form of a normally harmless protein found in the brain that is responsible for a variety of fatal neurodegenerative diseases of animals including humans. All prion diseases in mammals affect the structure of the brain or other neural tissue and have no known effective treatment. Prion diseases are always fatal. Creutzfeldt Jakob disease is the prion disease in humans. So the correct answer is 'protein'.