Prusiner received his A.B. in chemistry in 1964 and his M.D. in 1968 from the University of Pennsylvania. Following his internship at the University of California, San Francisco (UCSF), he came to the National Heart and Lung Institute, part of the National Institutes of Health (NIH), in 1969. Working there in Earl Stadtman's laboratory, he learned various aspects of the research process in biochemistry: developing assays, purifying macromolecules, documenting a discovery by many approaches, and writing clear manuscripts describing what is known and what remains to be investigated. As he later recalled, his three years at NIH were critical in his scientific education.
In 1972, Prusiner began a residency at UCSF in the department of neurology, where he became interested in a "slow virus" infection called Creutzfeld-Jakob disease (CJD) and the seemingly related diseases -- kuru of the Fore people of New Guinea and scrapie of sheep. Prusiner joined the UCSF faculty in 1974 and continued his studies on scrapie. Finally in 1982, he published a paper in which he claimed to have isolated the scrapie-causing agent. This agent, which he termed a "prion," was not like other known pathogens, such as viruses and bacteria, because it consisted only of protein and lacked the nucleic acid having genetic information. Prusiner's paper immediately set off a firestorm of criticism, especially from virologists, but by the mid-1990s, his discovery had become widely accepted. And in 1997 he was awarded the Nobel Prize in Physiology or Medicine.
The Nobel Assembly awarded Prusiner the Prize "for his pioneering discovery of an entirely new genre of disease-causing agents and the elucidation of the underlying principles of their mode of action. Stanley Prusiner has added prions to the list of well known infectious agents including bacteria, viruses, fungi and parasites."