Prions are proteinaceous infectious particles that lack nucleic acid and are a type of infectious agent made only of protein.

Prion

Prions are proteinaceous infectious particles that lack nucleic acid and are a type of infectious agent made only of protein. Prions are believed to infect and propagate by refulding abnormally into a structure which is able to convert normal molecules of the protein into the abnormally structured form, and they are generally quite resistant to denaturation by protease, heat, radiation, and formalin treatments although potency or infectivity can be reduced.

Diseases caused by prions are fatal familial insomnia, kuruscrapie chronic wasting disease, variant Creutzfeldt-Jakob disease and bovine spongiform encephalopathy. All of these diseases affect the structure of the brain or other neural tissue, and all are untreatable and fatal.