Prions (Prn)

Prions (Prn)

Prions (Prn) are infectious agents composed solely of misfolded proteins that can induce abnormal folding in normal variants of the same protein. This misfolding leads to cellular dysfunction and death, resulting in a group of fatal neurodegenerative diseases known as transmissible spongiform encephalopathies (TSEs). Prion diseases affect both humans and animals and are characterized by long incubation periods followed by rapid progression once symptoms appear.

Key Points about Prions:

Definition:
A prion is a misfolded protein that propagates its abnormal conformation to normal proteins, leading to a cascade of misfolding. Unlike other infectious agents such as bacteria and viruses, prions do not contain nucleic acids (DNA or RNA) and are resistant to conventional methods of sterilization, making them particularly challenging to eliminate from contaminated environments.

Types of Prion Diseases:

• Creutzfeldt-Jakob Disease (CJD):

• The most common prion disease in humans, CJD can occur sporadically, be inherited genetically, or be acquired through exposure to infected tissues.

• Bovine Spongiform Encephalopathy (BSE):

• Also known as “mad cow disease,” BSE affects cattle and can be transmitted to humans through the consumption of infected meat products, leading to variant CJD.

• Kuru:

• Historically found among the Fore people of Papua New Guinea, kuru was transmitted through ritualistic cannibalism. Symptoms include tremors, loss of coordination, and eventually death.

• Fatal Familial Insomnia:

• This inherited form of prion disease leads to severe sleep disturbances and neurodegeneration, ultimately resulting in death.

• Chronic Wasting Disease (CWD):

• Affects deer and elk populations; CWD is characterized by weight loss, behavioral changes, and ultimately death.

Mechanism of Action:

Prions propagate by inducing conformational changes in normal prion proteins (PrP^C) into their pathogenic forms (PrP^Sc). These misfolded proteins aggregate into amyloid plaques that disrupt normal cellular function and lead to neurodegeneration. The accumulation of these aggregates creates a spongy appearance in brain tissue, which is a hallmark of prion diseases.

Transmission:

Prion diseases can be transmitted through several routes:

• Ingestion: Consuming contaminated meat products.
• Medical Procedures: Transplantation of infected tissues or use of contaminated surgical instruments.
• Genetic Mutation: Inherited mutations in the prion protein gene can lead to familial forms of the disease.

Conclusion

Prions represent a unique class of infectious agents that challenge traditional concepts of infection due to their protein-only composition and ability to induce disease without nucleic acids. Understanding prions is crucial for developing strategies for prevention, diagnosis, and potential treatment of prion diseases.

For further information on prions, you can refer to the following source:

• Prion Diseases (2021). In Nature Reviews Disease Primers. https://doi.org/10.1038/s41572-021-00280-4