What are prions? The actual word has significance as this word is derived from protein and infection and hence called a ” proteinaceous infectious particle”. In modern science, these abnormal disease-causing protein agents are responsible for several neurological diseases that affect both human and animals. These agents are non-living likewise similar to viruses but lack genetic material such as DNA and RNA which make them unique from other infectious agents like bacteria and fungi.
This word ‘prion’ is given by Stanley B Prusiner in 1982 and he received Nobel Prize in Physiology or Medicine in 1997 and the Albert Lasker Award in 1994 for basic medical research on prions developed by him and his group.
Prions are infectious proteins that spread by changing the shape of normal proteins present in the host prompting the obliteration of neurons making a brain look like a sponge. The diseases caused by prion are referred to as transmissible spongiform encephalopathies (TSE) because of sponge-like appearance after infection.
These basically affect the brain cells and causes change in the memory, behavioural pattern and development of a life form.
SHORT HISTORY ABOUT PRIONS
- The 1730s: The earliest record of Scrapie disease in sheep which affects the nervous system and was not transferable to humans
- The 1950s: Kuru disease found in the people of New Guinea as a demonstration of human flesh consumption in which they ate the brain of dead people as part of their funeral custom
- The 1960s: Scientists experimentally transferred Kuru and CJD to chimpanzees for examining the nature of proteins
- The 1982s: Finally the term ‘prion’ is discovered by Dr Stanley Prusiner
Normal prions contain about 200-250 amino acids twisted in three telephone cord like coils known as helices, with tails of more amino acids. The mutated and infectious form is worked by the similar amino acids however takes an alternate shape structure.
DISEASE CAUSED BY PRIONS IN HUMANS:
- Creutzfeldt-Jacob disease (CJD) – It is a lethal degenerative brain disorder. Early indications incorporate memory issues, conduct changes, helpless coordination and visual disturbances.
- Variant Creutzfeldt-Jacob disease (VCJD)- It is also called human mad cow disease or human bovine spongiform encephalopathy (BSE). It is a rare, degenerative and deadly cerebrum illness that was first described in 1996 in the United Kingdom.
- Gerstmann-Staussler-Scheinker syndrome– It is an extremely rare neurodegenerative brain disorder. In the beginning stage, patients may encounter changing degrees of ataxia (absence of muscle coordination), including awkwardness, unsteadiness and trouble strolling.
- Fatal familial insomnia – This neurodegenerative disorder mainly affects the thalamus which is very rare in families. Its symptoms include insomnia, speech problems and dementia.
- Kuru – The name kuru signifies “to shudder” or “ shaking in dread”. The symptoms include muscle twitching and loss of coordination. Other symptoms include trouble strolling, involuntary movements, mood swings, dementia and trouble eating. In a later phase, it also leads to malnutrition and the cure for this disease is not yet known.
- Variably protease-sensitive prionopathy (VPSPr) – This disease was first recognised in 2008 and was later renamed in 2010. Scientists have not recognised any gene mutation that causes this sickness. But VSPRr is thought to be different from other prion diseases because enzymes called proteases can break the prions more effectively than happens in other prion infections.
DISEASE CAUSED BY PRIONS IN ANIMALS:
- SCRAPIE – It is a lethal degenerative affecting the central nervous system of goats and sheep. The disease was first recognised as affecting sheep in Great Britain and other countries of western Europe over 250 years ago. The symptoms may include pathological changes which are confined to the CNS and include vacuolation, neuronal loss and in certain people amyloid plaques may be seen.
- Bovine Spongiform Encephalopathy – It is also called mad cow disease. A common indication of BSE is incoordination. An infected cow has difficulty strolling. It generally takes four to six years for an infected cow to show its first sign of BSE.
- Transmissible Mink Encephalopathy – It is a progressive fatal neurodegenerative illness that affects ranched milk. Most of the entire grown-up animals on the farm might be influenced and once an animal gets symptomatic, death is inevitable.
- Feline Spongiform Encephalopathy – This disease affects the members of the cat family. FSE was first reported in 1990 and was apparently transferred to individual cats through BSE contaminated food.
- Ungulate Spongiform Encephalopathy – It is a rare brain disorder found in mammals with hooves.
- Chronic wasting disease of cervids – It was first recognised in 1967 in captive mule deer. This disease is mostly transmitted through body fluids such as saliva, urine and faeces.
- Spongiform encephalopathy of primates