In the 1950s, Australia administered Papua New Guinea and wanted to gain control over its primitive tribal people to reduce:
The constant tribal warfare
The practice of cannibalism
On an early pacification mission, the young doctor Vincent Zigas became aware of a disease of the Fore tribe:
“I observed a small girl sitting down beside a fire. She was shivering violently, and her head was jerking spasmodically from side to side. I was told that she was a victim of sorcery, and would continue this shivering unable to eat until death claimed her within a few weeks.”
The disease was called kuru, a Fore word meaning “trembling.”
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Carl Gajdusek Makes a Series of Important Observations
In 1957, Carl Gajdusek (Guy-doo-shek), an American physician on his way home from a fellowship in Australia, stopped in Papua New Guinea, and discovered his life's work.
Observations regarding kuru:
The victims' brains were sent to NIH and recognized to be similar to the brains of CJD victims.
The incidence of Kuru was greatest in women and children—not adult males.
The Fore were cannibals: they ate their dead relatives as an act of homage.
Men ate the muscle; woman and children ate the brains.
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Gajdusek's Nobel-Prize–Winning Discovery
Through a series of experiments, Gajdusek established that kuru was a disease transmitted through the cannibalistic practices of the Fore.
He was able to get the Fore to stop cannibalism.
Incidence of kuru peaked in the 1960s and has been decreasing ever since.
However, symptoms of the disease may not appear for decades.
Recently a person died of kuru, even though cannibalism has been discontinued for over 40 years!
Gajdusek won the Nobel Prize in 1976 for demonstrating for the first time in the history of medicine that human diseases causing central nervous system degeneration could be infectious.
A new category of disease was identified: transmissible spongiform encephalopathies (TSEs).
First sentence: Kuru was the first chronic degenerative disease of man shown to be a slow virus infection, with incubation periods measured in years with a progressive accumulative pathology always leading to death.
Is TSE Caused By A Virus?
In the 1960s most scientists believed that viruses caused TSEs, which included kuru and a similar disease in sheep, called scrapie.
A number of experimental results caused them to begin to question the viral hypothesis:
The agent remained infectious after being exposed to temperatures of 600° C, which was highly unusual for viruses.
Using a high-energy beam of electrons, the agent was shown to be smaller, by a factor of 10, than any known virus.
Ultraviolet treatment to destroy nucleic acids did not affect the infectivity of the agent.
Problems still existed for researchers studying TSEs:
No good model animal existed on which to research TSEs.
Scrapie in sheep was hard to study because it took several years for them to come down with the disease, etc.
Stanley Prusiner's Breakthrough
Finally, by the early 1980s, Stanley Prusiner of UCSF made a huge breakthrough: he caused hamsters to come down with scrapie.
This shortened the disease incubation time.
It was also easier to raise hamsters.
Experimental results using this new method:
It was impossible to impede the infectivity using sophisticated compounds that destroyed nucleic acids (e.g. nucleases).
Chemicals that denatured or digested protein inactivated the infective agent.
The size of the agent was determined to be about 250 amino acids long!
His 1982 publication in Science:
Because the dominant characteristics of the scrapie agent resemble those of a protein, an acronym is introduced to emphasize this feature. In place of such terms as ‘unconventional virus’ or ‘unusual slow virus-like agent,’ the term ‘prion’ is suggested.
Prion is pronounced pree-on.
A prion is a “proteinaceous infectious particle.”
Prusiner won the 1997 Nobel Prize for his discovery of a “new biological principle of infection.”
