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.)