In 1997 Prusiner was awarded the Nobel Prize in Physiology or Medicine "for his discovery of Prions - a new biological principle of infection."

In his 1982 paper Prusiner proposed a completely novel explanation for the cause of bovine spongiform encephalopathy ("mad cow disease") and its human equivalent, Creutzfeldt–Jakob disease.To describe the cause of the disease in this paper Prusiner coined the term prion, which comes from the words "proteinaceous" and "infectious," to refer to a previously undescribed form of infection, due to protein misfolding, with no DNA or RNA involved. This new concept "violated all the rules" and failed to convince the scientific community, most of whom initially thought that Prusiner was "totally insane."
See also Nos. 10842, 12835 and 7624.

Research with the biochemist Bolton enabled Prusiner to discover and characterize the specific protein causing prion disease. This paper was dated December 24, 1982.

Nearly simultaneously, Prusiner and the same co-authors published an additional, longer paper dated December 21, 1982, further characterizing the pure protein of the infectious agent:

"Further purification and characterization of Scrapie prions," Biochemistry, 21 (1982) 6942-6950. 

These papers provided the necessary evidence to convince members of the scientific community, and eventually led to Prusiner's Nobel Prize.

(Thanks to Juan Weiss for these references and their interpretation.)

The authors showed that the " 'normal prion protein' in the brains of living mice can be converted into different forms depending on the type of abnormal human prion that initiated the conversion. The result is different patterns of pathological changes in the host, as would be expected for different prion strains." Prusiner proposed that "infection with one of the misfolded proteins can induce disease by forcing healthy PrP molecules to refold themselves into abnormal prions." 

(Order of authorship in the original publication: Telling, Parchi De Armond...Prusiner.)

(Thanks to Juan Weiss for this reference and its interpretation.)

The authors modified Koch's Postulates within the context of prion disease. To do so the followed these steps:

1) They created recombinant mouse prion proteins in an E. coli and polymerized them.
2) They proved that these prion proteins were pure, and could not have any extraneous contaminating cellular or DNA/RNA material.
3) They injected these prion proteins aseptically into the brains of normal mice, fed them, reared them, and waited.
4) The mice developed neurologic dysfunction typical of a prion disease between 380 and 660 days after the injection.
5) Extracts from the brains of the mice were confirmed by Western blot analytic technique to be prionic in nature.
6) These abnormal prion proteins extracted from the mouse brains, when inoculated into and transmitted to other healthy mice, induced the typical neuropathological findings of the same prion illness.

(Order of authorship in the original publication: Legname, Baskakov, Nguyen....Prusiner.)

(Thanks to Juan Weiss for this reference and its interpretation.)

Prusiner discovered prions, the agent causing scrapie in sheep and goats, mad cow disease, and Creutzfeldt-Jakob disease in humans.