Are Prions infectious agents?

Creutzfeldt-Jakob disease

What are prions?

Prions are infectious agents which consist of an abnormally folded protein. These are similar in size to viruses. These are encoded by the PRNP gene and are particularly composed of 253 amino acids. Stanley Prusiner gave the term prion, derived from infectious protein. 

Prions are infectious agents

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Prions are infectious agents: Diseases

Prion diseases are also termed transmissible spongiform encephalopathies (TSEs). Transmissible refers to the fact that the causative agent is infectious. Spongiform refers to the development of holes in the brain, making it appear like a sponge. Encephalopathy means a disease of the brain.

They are fatal neurodegenerative disorders that have caught our eye not only because of their unique biological features but also because of their disease-causing nature. Prions (proteinaceous infectious particles) are thought to consist of abnormally folded proteins (PrPsc), that can induce normal forms of the protein (PrPP), to fold abnormally. The number of diseases and the fatal nature of those diseases clearly suggest that prions are infectious agents. They are known to cause diseases in animals and no prion diseases of plants are known. However, recent studies suggest that plants can serve as potential carriers of prions (taken from infected soil). Read more- Grass plants bind, retain, uptake, and transport infectious prions – PubMed (nih.gov)

Prions are infectious agents

Image Source: Prescott Harley Kleins Microbiology

Kuru

This disease was first discovered in the Fore tribe of New Guinea. Carlton Gadjusek depicted that a disease was transmitted by a ritual called cannibalism in which brains and spinal cords were consumed. A major symptom of Kuru was seen to be dementia in which there is motor dysfunction such as cerebral ataxia (muscle activity not coordinated) and myoclonus (there are shocklike contractions of muscle groups). Kuru was more common in women and children. The incubation period for this disease is months to years.

Kuru

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Fatal familial insomnia (FFI)

Fatal familial insomnia

Fatal familial insomnia is another prion disease characterized by dysautonomia (a term for the abnormal functioning of the ANS) and sleep disturbances. These symptoms are seen in middle to late adult life. 

Bovine spongiform encephalopathy (BSE) 

It is commonly called mad cow disease. It is a brain disorder in adult cattle. It is a progressive neurologic disease (it tends to get worse with time). The neurologic term refers to the damage to the central nervous system (brain and spinal cord). It has been seen experimentally that the cattle infected orally tested positive for the BSE prion agent in various locations like the brain, retina, spinal cord,  bone marrow and distal ileum. The results suggest that the BSE agent tends to survive along the gastrointestinal tract. Thus, it was concluded that the BSE agent is neurotropic. The incubation period for this disease is months to years.

 Bovine spongiform encephalopathy (BSE)

Microscopic images in BSE (Image Source: https://www.fda.gov)

Creutzfeldt-Jakob disease (CJD)

Creutzfeldt-Jakob disease

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The analogous variant of Bovine spongiform encephalopathy (BSE of cattle) is Creutzfeldt-Jacob disease (CJD) in humans. If humans consume diseased meat products from that of infected cattle, they can have this disease. Symptoms are rapid mental deterioration, usually in a time span of a few months. Dementia is a common condition reported in CJD. It is a fatal disease.

Gerstmann-Sträussler-Scheinker disease (GSD)

Gerstmann-Straussler-Scheinker disease is a neurodegenerative brain prion disease. Some of the symptoms in the early stages include ataxia (a term for the lack of muscle coordination). This leads to difficulty in walking. In complex cases, dementia can be seen. Dysarthria that is slurring of speech is also reported in many cases along with spasticity (a term for rigid muscle tone).  Visual and hearing problems are also seen sometimes. 

Hope this article explained to you that prions are infectious agents that are highly dangerous. 

Thank you for reading at MBD.

Gerstmann-Sträussler-Scheinker disease (GSD)

 

 

 

 

 

 

 

 

 

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