Throughout history,  revolutionary discoveries that contradict common knowledge have been made while searching for solutions to relatively insignificant problems.  In  the 1960’s scientists were searching for the cause of a degenerative brain disease found in sheep called scrapie.  They discovered the existence of a new infectious agent containing neither DNA nor RNA.  Later, in 1980, a neurologist named Stanley B. Prusiner hypothesized that this new agent was a protein.  Through a test, Prusiner found his hypothesis to be true.  This protein now called a Prion, short for proteinaceous infectious particle has been found to be the cause of degenerative brain diseases found in humans, cows, sheep and other mammals.  This discovery contradicted the common belief that DNA and RNA are the only substances that can replicate in body tissues and it shook up the world of biological sciences by introducing an unprecedented agent of infectious diseases.  This discovery was to have an impact not only on basic science, but on world economics and government regulations (Encarta).

 The road to the discovery began when Prusiner joined the University of California, San Francisco in 1972.  In his experiments he exposed tissue infected with scrapie to a treatment that destroyed proteins and found that the carrier was indeed a protein.  In 1982 Prusiner and his colleagues published their first work introducing and labeling prions.  This work talked about the fact that all animals have the gene that produces prions, a corkscrew-shaped protein found on the outside of brain cells (Encarta).  However in an infected sheep these prions mutate from a normal PrPC protein to a PrPSc protein and fold flat like an accordion.  When a large number of prions are infected the brain takes on a sponge-like look (Gee, 1).  The disease causes hallucinations, dementia, panic attacks and eventually death (Schardt and Schmidt, 4).
 The diseases caused by prions are called Transmissible Spongiform Encephalopathies or TSEs.  The name is derived from encephalopathy, meaning brain, spongiform, because the diseases leave infected tissue looking like a sponge and transmissible, because they can spread (Schardt and Schmidt, 4).  In the beginning TSEs such as scrapie, found in sheep, were quite misunderstood, and were not believed to be a threat to humans.  The only research being done was by small groups, competing over small scientific grants for funds.  It wasn’t until cows started showing symptoms much like those of scrapie-infected sheep, that scientists started to notice.  It was decided that the cows had contracted the disease through eating the brains of scrapie-infected sheep.  Even with the discovery of this new disease, commonly known as Mad Cow Disease or scientifically called Bovine Spongiform Encephalopathies (BSE), scientists were not afraid that the disease could spread to humans (Dealler, 2-4).  Paul Brown at National Institutes of Health explained that in order to infect a rat with BSE it, “requires an injection into the brain of a thousand times more infected tissue than it takes to give BSE to another cow.  We’re counting on this species barrier to help protect us. (Schardt and Schmidt, 5)”   The British government was insistent that humans could continue to eat BSE infected meat because BSE could not be transmitted to humans (Dealler, 3).
 There are other known TSE’s such as Creutzfeldt-Jakob disease (CJD) and kuru, which both effect humans.  There are several different types of CJD,  sporadic, genetic, iatrogenic.  The sporadic type is a spontaneous mutation of the prion gene.  This accounts for nearly eighty-five percent of all CJD cases.  The genetic disease is passed on from one generation to another.  About half of a CJD carrying family will die from the disease.  The iatrogenic disease results from contact with an infected carrier through surgery or transfusion.  These three were the only known types of CJD at the beginning of the BSE breakout (Encarta).
 In 1995 a new case of CJD began showing up.  Stephen Churchill a 19-year old boy in Great Britain was the first case of variant-CJD or V-CJD.  This type of CJD is believed to have been passed from infected cow meat to Churchill.  Churchill died five months after it was first noticed.  Churchill’s father said, “I can still see his expression.  It was as if he could see what was happening but couldn’t work out how he could stop it.”  Many more would soon follow, including two more teenagers, a 42-year-old businessman and a pregnant woman, who delivered her baby in a coma (Scardt and Schmidt, 4-6).  These incidents proved that humans weren’t safe from “Mad Cow Disease.”   After this discovery the British government’s credibility was damaged.  Throughout the incident, government officials tried to control hysteria so that British beef could still be exported.  With this development new meat bans were created and new regulations about beef processing were made in Great Britain (Dealler, 2). The U.S. began taking precautions against a possible attack of BSE or V-CJD in North America.  Joe Gibbs, the acting chief of the Laboratory of Central Nervous System Studies at the National Institutes of Health, said, “I think it is essential for everybody to know that the USDA (United States Department of Agriculture) is looking and we’re all ready to jump when it happens... if it happens (Schardt and Schmidt, 6).” In addition to beef exports, the export of blood from Great Britain might also be banned, for it is believed that blood may carry the infectious prion protein as well (Johnson and Gibbs, 1999).  At any rate, preventive health measures for the public and health care workers regarding blood and brain tissue handling have changed because of prion discoveries.
 The discovery of prions, the cause of BSE, CJD, kuru and scrapie, had an impact well beyond the British beef industry and the handling of diseased tissues.  Now that the prion has been identified, it will be much easier for a cure for all TSEs to be found.  Prusiner’s discovery might also affect the research of other neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis (ALS) (Encarta).
 Although Prusiner’s discovery won him the 1997 Nobel Prize in physiology or medicine, there are some scientists that would still argue its validity.  There is disagreement as to whether a virus or other infectious agent may accompany prions, and that the prions cannot cause infection without them.  Others believe that TSEs are cause by an unidentified slow-acting virus.  Still more scientists think that another protein, called a “chaperone,” initiates the folding of the normal prion proteins (Dealler).  Whether or not any of these theories prove true, Prusiner’s breakthrough is invaluable for its impact on medicine, health safety measures and perhaps most importantly the questions it has raised for future research.

     Bibliography

Dealler, Steve. History of BSE.  <www.airtime.co.uk/bse/hist.htm> (2/21/99): 1-7.

Dealler, Steve.  Hypotheses for the origin and spread of BSE.        <www.airtime.co.uk/bse/hypoth.htm> (2/21/99): 1-7

Gee, Henry.  Molecular Evolution of Prions.  <www.mad-cow.org/~tom/prion_evol.html>   (1/11/99): 1-3.

Haywood, Anne M., M.D.  “Mechanisms of Disease.” The New England Journal of Medicine.   December 1997: 1821-1827.

Johnson,  Richard T., M.D. and Gibbs, Clarence J., M.D.  “Medical Progress.”  The New    England Journal of Medicine.  December 1998: 1994-2003.

“Prions” Microsoft Encarta Encyclopedia 99.  1993-98.

Prusiner B. Stanley.  “Prion Disease and the BSE Crisis.”  Science.  October, 10, 1997:  245-251.

Schardt, David and Schmidt, Stephen.  “Mad About BSE.”  Nutrition Action: HealthLetter.    July/August 1997: 4-7.

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