Of all the etiologies of infectious diseases, one of the coolest has to be the prion. Prions are the smallest infectious agents and broke all the paradigm when they were definitively linked to diseases. It was almost heresy to postulate that a proteinaceous infectious particle--devoid of nucleic acid--could cause disease. But today's heresy is tomorrow's Nobel Prize, as Carleton Gajdusek and Stanley Prusiner showed.
Prions cause disease in a unique way. Though they are definitely transmissible prion diseases they are, in essence, misfolded proteins that cause a cascade of protein misfolding leading to neurologic dysfunction. In some instances, the initial misfolding is the result of a sporadic genetic mutation and in others it is because of introduction of a misfolded protein causing the cascade. It is an impressive process.
Eventually prions, first linked to scrapie in sheep, were linked to human diseases known as the Creutzfeldt-Jakob Diseases (CJD), the most famous of which is new variant CJD (vCJD)--the human form of mad cow disease--as well as the human cannibalism-linked kuru. The story of vCJD is well documented. In short it has to do with changes in industrial farming practices allowing scrapie in sheep to get into cows and then into humans. The human outbreak, which captured headlines in the 1990s, is essentially over as farming practices have changed so as to eliminate exposure to the prion.
Prions may have slipped from the headlines but research on them continued nonetheless and this week it was announced that a novel prion (alpha-synuclein) was linked to another neurologic disease: Multiple System Atrophy (MSA). Not surprisingly, this discovery came from Dr. Prusiner's lab.
The biggest implication of this finding is further evidence supporting the hypothesis that other neurodegenerative diseases may have a prion component to their cause. Such an understanding may open up new avenues for treatment and screening for these dreaded diseases.