Prion

About Prion Diseases Prion diseases or transmissible spongiform encephalopathies (TSEs) are a family of rare progressive neurodegenerative disorders that affect both humans and animals. They are distinguished by long incubation periods, characteristic spongiform changes associated with neuronal loss, and a failure to induce inflammatory response. The causative agent of TSEs is believed to be a prion. A prion is an abnormal, transmissible agent that is able to induce abnormal folding of normal cellular prion proteins in the brain, leading to brain damage and the characteristics signs and symptoms of the disease. Prion diseases are usually rapidly progressive and always fatal.

These diseases

• are transmissible — from host to host of a single species and, sometimes, even from one species to another (such as a laboratory animal)
• destroy brain tissue giving it a spongy appearance

For these reasons, prion diseases are also called transmissible spongiform encephalopathies or TSEs.

Examples

Creutzfeldt-Jakob Disease (CJD)

A number of humans have acquired CJD through accidental exposure to material contaminated with CJD prions.

• Grafts of dura mater taken from patients with inherited CJD have transmitted the disease to more than 100 recipients.
• Corneal transplants have also inadvertently transmitted CJD.
• Instruments used in brain surgery on patients with CJD have transmitted the disease to other patients. Two years after their supposed sterilization, these instruments remained infectious.
• Over 100 people have acquired CJD from injections of human growth hormone or human gonadotropins prepared from pooled pituitary glands that inadvertently included glands taken from humans with CJD.

Now that both hGH and human gonadotropins are available through recombinant DNA technology, such disastrous accidents need never recur.

Variant Creutzfeldt-Jakob Disease (vCJD)

This human disorder appeared some years after the epidemic of BSE (Mad Cow Disease) swept through the cattle herds in Great Britain. Even though the cow and human PRNP genes differ at 30 codons, the sequence of their prions suggests that these patients (155 by 2005) acquired the disease from eating contaminated beef.

All the patients are homozygous for the susceptibility polymorphism of methionine at position 129.

The BSE epidemic has waned, and slaughter techniques that allow cattle nervous tissue in beef for human consumption have been banned since 1989. Now we must wait to see whether more cases of vCJD are going to emerge or whether the danger is over.

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Prions.html#CPEB

http://www.cdc.gov/ncidod/dvrd/prions/index.htm

http://www.bioedonline.org/news/news.cfm?art=702

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