Transmissible Spongiform Encephalopathies

Definition

Transmissible spongiform encephalopathies (TSEs) are a group of rare, fatal neurodegenerative disorders caused by abnormally folded proteins called prions. These disorders primarily affect the brain and nervous system, leading to sponge-like changes in brain tissue.

5 Must Know Facts For Your Next Test

1. TSEs are caused by the conversion of normal, cellular prion proteins into abnormal, infectious prion proteins that aggregate and spread throughout the brain.
2. TSEs can be acquired through exposure to contaminated tissue or medical procedures, inherited due to genetic mutations, or occur sporadically with no known cause.
3. Common TSEs include Creutzfeldt-Jakob disease (CJD), bovine spongiform encephalopathy (BSE or 'mad cow disease'), chronic wasting disease (CWD) in deer and elk, and scrapie in sheep and goats.
4. TSEs are characterized by long incubation periods, ranging from months to years, before the onset of clinical symptoms.
5. There are currently no effective treatments or cures for TSEs, and they are invariably fatal once symptoms appear.

Review Questions

• Explain how the misfolding of prion proteins leads to the development of transmissible spongiform encephalopathies.
  • The key feature of transmissible spongiform encephalopathies (TSEs) is the conversion of normal, cellular prion proteins into abnormal, infectious prion proteins. These misfolded prions can then induce the misfolding of additional normal prion proteins, leading to the formation of aggregates that accumulate in the brain. This prion propagation and aggregation results in the characteristic sponge-like degeneration of brain tissue, ultimately causing the neurological symptoms and progressive, fatal nature of TSEs.
• Describe the different ways in which transmissible spongiform encephalopathies can be acquired.
  • Transmissible spongiform encephalopathies (TSEs) can be acquired through three main pathways: 1) Exposure to contaminated tissue or medical procedures, such as the use of improperly sterilized surgical instruments; 2) Inheritance due to genetic mutations in the prion protein gene; and 3) Sporadic occurrence with no known cause. The specific mode of transmission can vary depending on the type of TSE, but all involve the introduction or propagation of the abnormal prion proteins that ultimately lead to the characteristic sponge-like degeneration of the brain.
• Evaluate the significance of the long incubation periods and the lack of effective treatments for transmissible spongiform encephalopathies.
  • The long incubation periods of transmissible spongiform encephalopathies (TSEs), ranging from months to years, pose significant challenges for diagnosis and prevention. By the time clinical symptoms appear, the disease is often well-established and rapidly progressing, making it difficult to intervene effectively. Furthermore, the lack of any known cures or effective treatments for TSEs is particularly concerning, as these invariably fatal disorders leave patients and their families with limited options. The combination of long incubation periods and the absence of therapeutic interventions highlights the importance of continued research to better understand the underlying mechanisms of TSEs and develop strategies to detect, manage, and potentially cure these devastating neurological disorders.

Related terms

Prions:

Infectious agents composed of misfolded proteins that can induce the misfolding of normal versions of the same protein, leading to disease.

Spongiform Degeneration: The hallmark pathological feature of TSEs, characterized by the formation of numerous small holes in the brain tissue, giving it a sponge-like appearance.

Creutzfeldt-Jakob Disease (CJD): The most common human TSE, characterized by rapidly progressive dementia, ataxia, and other neurological symptoms leading to death.