Transmissible spongiform encephalopathy

Transmissible spongiform encephalopathies (TSEs), also known as prion diseases, are a group of rare fatal degenerative brain disorders with no cure. These diseases are characterized by tiny holes that give the brain a "spongy" appearance. The holes can be seen when brain tissue is viewed under a microscope.

Research suggests that TSEs are caused by an abnormal version of a protein called a prion (prion is short for proteinaceous infectious particle). Prion proteins occur in both a normal form, which is a harmless protein found in the body's cells, and in an infectious form, which causes disease. The harmless and infectious forms of the prion protein are nearly identical, but the infectious form takes on a different folded shape from the normal protein.

Human TSEs can occur three ways: sporadically; as hereditary diseases; or through transmission from infected individuals. Sporadic TSEs may develop because some of a person's normal prions spontaneously change into the infectious form of the protein and then alter the prions in other cells in a chain reaction. Inherited cases arise from a change, or mutation, in the prion protein gene that causes the prions to be shaped in an abnormal way. This genetic change may be transmitted to an individual's offspring. Transmission of TSEs from infected individuals is relatively rare. TSEs cannot be transmitted through the air or through touching or most other forms of casual contact. However, they may be transmitted through contact with infected tissue, body fluids, or contaminated medical instruments. Normal sterilization procedures such as boiling or irradiating materials do not prevent transmission of TSEs.

Symptoms of TSEs vary, but they commonly include personality changes, psychiatric problems such as depression, lack of coordination, and/or an unsteady gait. Patients also may experience involuntary jerking movements called myoclonus[?], unusual sensations, insomnia, confusion, or memory problems. In the later stages of the disease, patients have severe mental impairment and lose the ability to move or speak.

Prion Diseases

The following diseases are believed to be caused by prions thus belonging to the TSE family of diseases:

• In animals
  • Scrapie in sheep
  • BSE Bovine Spongiform Encephalopathy in cows
  • TME Transmissible mink encephalopathy[?] in mink
  • CWD Chronic wasting disease in elk and deer
• In humans
  • CJD Creutzfeldt-Jakob Disease
  • GSS Gerstmann Straussler Schenker Syndrome[?]
  • FFI Fatal Familial Insomnia
  • Kuru

In addition to above mentioned diseases, there is accumulating evidence that Alpers syndrome[?] might be a childhood prion disease.

In a few rare cases, TSEs have occurred in other mammals such as zoo animals. These cases are probably caused by contaminated feed. CJD and other TSEs also can be transmitted experimentally to mice and other animals in the laboratory.

Possible Cure or Vaccine

Recent research from the University of Toronto and Caprion Pharmaceuticals have discovered one possible avenue which might lead to quicker diagnosis, a vaccine or possibly even treatement for prion diseases. The abnormally folded prions which cause the disease have been found to expose a side chain of amino acids which the properly folder prion does not expose. Antibodies specifically coded to this side chain amino acid sequence have been found to stimulate an immune response to the abnormal prions and leave the normal prions intact. [1] (http://www.sciencedaily.com/releases/2003/06/030602025719.htm)

Reference

• This entry incorporates public domain text originally from the National Institute of Neurological Disorders and Stroke, National Institutes of Health. [2] (http://www.ninds.nih.gov/health_and_medical/disorders/tse.htm)