In the early 1950s, Australian officers that were surveying the highlands of Papua New Guinea reported descriptions of a new disease that were affecting the Fore people in that area. The victims of this disease would exhibit strange psychological symptoms such as emotional instability and uncontrollable laughter before eventually succumbing to death. The condition was termed 'kuru' and at the time, kuru was believed to be caused by the practice of sorcery by the Fore tribe in the region.
But what exactly causes kuru? As you've probably learned from your high school biology class, there are a handful of microorganisms that are capable of causing diseases. Some of these microorganisms include bacteria, viruses and fungi, but have you ever heard of a prion? Most likely not.
Photo Credit: R. Dourmashkin, Wellcome Images.
To put it simply, prions are proteins that have acquired the ability to become infectious. Proteins are delicate, as these biomolecules retain a specific shape and perform a myriad of functions inside the human body. Proteins that are incorrectly shaped can have the ability to turn into prions. Unlike regular proteins, prions can also promote normal proteins to become infectious, leading to a positive feedback loop. Once enough of these prions aggregate inside the body, they can cause a number of conditions, such as kuru. As more of these prions have been studied, many more prion diseases have been discovered, including:
Mad cow disease (bovine spongiform encephalopathy): This disease affects cows and results when cows are fed tainted food infected with this prion. The human version of this disease, called Variant Creutzfeldt-Jakob disease (CJD), results when humans eat beef infected with this prion.
Fatal familial insomnia: This disease eventually results in the total inability to sleep, with death following after.
Gerstmann-Straussler-Scheinker syndrome: This disease usually affects people between the age of 35 - 60, leading to apraxia, deafness, and blindness.
Much is still unknown about prions, but one of the causes that results in proteins to become misfolded is due to a mutation in the PNRP gene. Although the function of this gene is still unknown, more than 30 mutations in the gene have been identified to cause multiple prion diseases. Due to this, some prion diseases (such as fatal familial insomnia) can also be inherited.
But why are these prions so frightening? For starters, prions are especially resistant to proteases, enzymes that can be used to break down regular proteins. For beef that has been infected with the prion that causes mad cow disease, cooking this beef won't help either, as these prions are also capable of withstanding high temperatures. Because of these factors, prions are often regarded as being indestructible. Unfortunately, prion diseases also have a 100% mortality rate and there is currently no cure for any prion disease.
Although these prions do seem frightening, it is important to note that prion diseases are extremely rare, with the World Health Organization reporting 1 case of Creutzfeldt-Jakob disease per 1 million people each year. To put this into perspective, the CDC estimates that millions of people are diagnosed with the flu each year with thousands of people dying from it per year. As new things are discovered about prions constantly, research still remains strong on uncovering the mysteries of these infectious agents to discover a cure for these rare diseases.
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