What are Prions?

Prion: A small proteinaceous infectious disease-causing agent that is believed to be the smallest infectious particle.

A prion is neither bacterial nor fungal nor viral and contains no genetic material.
Prions are virus-like organisms made up of a prion protein. These elongated fibrils (green) are believed to be aggregations of the protein that makes up the infectious prion. Prions attack nerve cells producing neurodegenerative brain disease. “Mad cow” symptoms include glazed eyes and uncontrollable body tremor.

Prions are misfolded proteins with the ability to transmit their misfolded shape onto normal variants of the same protein. They characterize several fatal and transmissible neurodegenerative diseases in humans and many other animals.

A prion is a type of protein that can cause disease in animals and humans by triggering normally healthy proteins in the brain to fold abnormally. The prion mode of action is very different to bacteria and viruses as they are simply proteins, devoid of any genetic material.

Prions are counted with virus, they are not even complete virus and of course they are even smaller than virus. As a typical virus they do not have a genetic material, they are consist of only protein particles those are called misfolded. Prions are highly infectious.

Not only are prions not alive (and contain no DNA), they can survive being boiled, being treated with disinfectants, and can still infect other brains years after they were transferred to a scalpel or other tool.
All known prion diseases in mammals affect the structure of the brain or other neural tissue; all are progressive, have no known effective treatment, and are always fatal.

What do prions looks like?

“When they are healthy, they look like tiny spheres; when they are malignant, they appear as cubes” stated Giuseppe Legname, principal investigator of the Prion Biology Laboratory at the Scuola Internazionale Superiore di Studi Avanzati (SISSA) in Trieste, when describing prion proteins.

Why do prions exist?

“Some researchers believe that the prions are formed when PrP associates with a foreign pathogenic nucleic acid. This is called the virino hypothesis. (Viruses consist of proteins and nucleic acids that are specified by the virus genome.
In human beings the abnormal prion has been reported in the brain, tonsils, spleen, lymph node, retina, and proximal optic nerve. Infectivity, although present in peripheral tissues, is at lower levels than in the central nervous system (CNS).

This year’s Nobel Prize in Physiology or Medicine has been awarded to Stanley B. Prusiner for his discovery of prions – a new biological principle of infection. What is a prion? It is a small infectious protein capable of causing fatal dementia-like diseases in man and animals.

Prions are proteinaceous particles that are able to self-propagate within hosts in a similar way as classic infectious agents.

Animal Prion Diseases and Humans

NIAID scientists use various experimental models to study how prions from one animal species can infect different animal species. These include studies to determine whether animal diseases such as CWD can infect people and cause Creutzfeldt-Jakob disease (CJD).

Scientists have shown that prions, bits of infectious protein that can cause fatal neurodegenerative disease such as bovine spongiform encephalopathy (BSE) or “mad cow disease,” have the ability to adapt to survive in a new host environment.

Mode of transmission


Scientists believe CWD proteins (prions) likely spread between animals through body fluids like feces, saliva, blood, or urine, either through direct contact or indirectly through environmental contamination of soil, food or water.

The CWD prion has been shown to experimentally infect squirrel monkeys, and also laboratory mice that carry some human genes. An additional study begun in 2009 by Canadian and German scientists, which has not yet been published in the scientific literature, is evaluating whether CWD can be transmitted to macaques—a type of monkey that is genetically closer to people than any other animal that has been infected with CWD previously.

Chronic wasting disease (CWD) is caused by a misfolded protein called a prion. All mammals produce normal prions that are used by cells, then degraded and eliminated, or recycled, within the body. When disease-associated prions contact normal prions, they cause them to refold into their own abnormal shape.

Good prions


Researchers have found nearly 50 helpful prions in yeast and comparable proteins in humans, suggesting that this dreaded protein type can boost survival and plays a role in evolution.

Gaurav Singh

Editor in Chief Medical Microbiology & RDT Labs - RDT Labs Magazine

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