Prions - Fatal Proteins that can kill you

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Most of the people think that microorganisms like virus and bacteria are only thing that cause life threatening diseases, but let me tell you that there are some proteins named "prions" that are more fatal than any bacteria or virus. A prion can kill a person very easily and there is no treatment for it.

History of Prions

During 1950s, Carleton Gajdusek was doing a research on kuru disease when he found a possibly a new infectious agent. In 1960s, Tikvah Alper and John Stanley Griffith, found that those infectious agent consist solely of proteins. In 1982, Stanley B. Prusiner announced that his team had purified the hypothetical infectious protein. Prusiner won the Nobel Prize in Physiology or Medicine in 1997 for his research into prions.

What are Prions ?

The word prion derives from "proteinaceous infectious particle", taken from the words protein and infection. Prions are misfolded  proteins, and nobody knows what causes the normal protein to misfold. Normal form of prion protein in found in cell membrane, but when a person get infected with prions, a misfolded version of same proteins, it becomes fatal. Prions have got the ability to transmit their misfolded shape onto normal variants of same protein. It causes neurodegenerative diseases, which damage brain and nervous system of mammals and finally kills the host as there is no known effective treatment.

Prions Diseases in Animals

  • Transmissible spongiform encephalopathies (TSEs): It is known as scrapie in sheep, chronic wasting disease (CWD) in deer.
  • Bovine spongiform encephalopathy (BSE): It infects cattle and commonly known as mad cow disease.

Prions Diseases in Humans

  • Creutzfeldt-Jakob disease (CJD)
  • variant Creutzfeldt-Jakob disease(vCJD)
  • Gerstmann–Sträussler–Scheinker syndrome (GSS)
  • fatal familial insomnia (FFI)
  • kuru
Some researchers believe that amyloids, abnormal aggregates of proteins formed by prions, are responsible for neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis (ALS).

Can we destroy Prions ?

Our body has got proteases, the enzymes that can break down proteins. But prions are resistant to proteases, hence it can't be destroyed by body. Prion aggregates are stable due to their structural stability, thus resistant to denaturation by chemical and physical agents. We can't even destroy them through normal disinfection or cooking.

How does prion infection spread ?

Before we tell you about prion infection spread, you must know that prion disease is very rare, as only 1 to 2 people in every 1 million people die due to it each year.
One can get affected with prions in three ways: acquired, genetic or sporadic.

  • Acquired: means a person gets exposed to prions and  gets infected. For example kuru (a prion disease) spread in a tribe through cannibalism, which was a tradition there as they eat their dead relatives. Similarly mad cow disease spread from cows to humans through contaminated cow meat. The acquired form of prion disease "vCJD" killed 200 people in UK since 1994. Apart from contaminated meat, there are some cases where prions spread through contaminated surgical instruments and transplants of dura matter (tissues surrounding brain).
  • Genetic: means that this disease was in the genes of the infected person. Mutations in the DNA (PRNP gene) produces these misfolded proteins at some point in their life. Most of the times such people live their whole life without this disease, but chances of getting this disease increase with age. Nobody knows what causes it to form these misfolded proteins. There are 40 genetic mutations that can cause prion disease. Here an interesting fact is that 60% of genetic prion disease patients have no family history of this disease. It shows how rarely this mutant gene expresses itself. 
  • Sporadic: It means that we don't know. In other words, you can say that protein misfolds by chance and then spreads. There are some cases where there is no significant evidence of  mutant genes or eating contaminated meat. There are 6 known strains of sporadic prion disease. Here an interesting fact is that 85% of prion disease is sporadic. Around 15% is genetic and less than 1% are aquired

This disease need a lot more research in future to keep humans on safer side. However this disease is very rare but still very scary.

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