PRIONS -- Beware what you eat!
Image 1 taken from:http://www.agric.gov.ab.ca/images/surveillance/prions.gif
Image 2 taken from:http://www.le.ac.uk/biology/research/phyto/prions.jpg
Prions, or infectious proteins, received a lot of media attention this year due to the revelation that it had somehow reached the United States. Although much was made of this, the focus of this page will be to look past the animal prion diseases and look more at how they affect humans.
Prions are the primary cause of Transmissible Spongiform Encephalophathies (TSEs). They occur in both humans and other animals.
Animal forms: Scrapie,BSE, Transmissible mink encephalopathy (TME), chronic wasting disease, Feline spongiform encephalopathy (FSE)(for more information on these forms please visit the website of John B. Mumm, Humans and Viruses, 1999 at http://www.stanford.edu/group/virus/prion/prion2.html )
Human forms: kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler syndrome (GSS), fatal familial insomnia (FFI)
All the TSEs are characterized by neuronal loss, accompanied by amyloid plaques or fibril formation after spongiform degeneration of brain tissue. They are progressive neuronal diseases that are always fatal.
Symptoms: Dementia, ataxia (loss of muscle control of voluntary movements) from the loss of brain function due to degeneration.
Outcome: Once symptoms appear, death results in 6 months -1 year. There is no cure and our own bodies can't even mount an immune response to this pathogen.
Pretty much all of the human TSEs occur throughout the population at an equal frequency, but Kuru was endemic among the Fore People of New Guinea until the ritualistic practice of cannibalism was ended there. (Look at to get a full look at the history of prion disesases) Also CJD tends to occur in older populations with very few cases occuring in individuals under the age of 40.
Transmission: Inoculation or ingestion of brain tissue, sporadic mutation, or it can be inherited.
Intubation period: This can be as long as 40 years as in Kuru, although it appears to be much shorter for viariant CJD cases.
GSS, FFI, and CJD are inheritable. This kind of transmission occurs when the dominant gene associated with the mutation in the prion protein is inherited. When that gene is present, there is close to a 100% likelihood that progression to one of these TSEs will result.
CJD can also occur both sporadically (at about a frequency of 1/million) or via inoculation. No matter how transmitted, once the mutation has occured in the protein to result in the prion, it can be transmitted as an infectious disease.
Prevention and Treatment
Presently there is no real treatment for any of the TSEs. Prions are very hardy and almost indestructible. Disinfection must occur with agents like environ LpH. Also, all efforts to keep out of contact with contaminated tissues should be made. More information on protocol can be found at the following websites:
This article tells of possible use of antibodies for treating prion diseases http://www.nature.com/nsu/030303/030303-7.html
This link shows the protocol for Johns Hopkins http://www.hopkins-heic.org/pdf/ifc032.pdf
Image taken from http://www1.umn.edu/eoh/hazards/hazardssite/prions/prioncontrol.html
- Fatal familial isomnia has been found for the first time in a family of Chinese descent!
check out the article from the Archives of Neurology January 2004 at http://archneur.ama-assn.org/cgi/content/full/61/1/122
Could this be a possible new strategy in preventing prion diseases in both animals and humans? To find out more, check out the article from the Journal of General Virology January 2004 at http://vir.sgmjournals.org/cgi/content/full/85/1/265
As crazy as this may sound, some researchers at Columbia University have made findings that indicate that the prion form of cytoplasmic polyadenylatin element binding protein (CPEB) is involved in the long term memory process. The article is in the January 2004 issue of SCIENCE. Check it out: http://www.sciencemag.org/cgi/content/full/303/5654/28a
Binding of copper to the normal protein PrP(C) may prevent the entry of the prion form PrP(Sc) into cells and also seems to slow down the accumulatin of PrP(Sc) in cells that are already infected. Is it possible that copper could be the new preventative agent against spongiform encephalopathies, like Mad Cow Disease?
To find out more, click on the article from the December 12 2003 issue of Brain Research:
Usually the onset of symptoms means certain death from any form of a prion disease, but in a monumental finding, destroying the protein PrP(C) before it could be transformed by the rogue protein PrP(Sc) stopped the spread of disease. The spongiosis caused by the prions also reversed.
To understand how this was done, please check out hte primary article from the October 31 2003 issue of SCIENCE:
Please feel welcome to visit the prion webpages from previous years:
Cindy Lin, Humans and Viruses 2002, http://www.stanford.edu/~cinders8/prions2002.html (this page has been having difficulty loading)
Erica Chung and Carmen Holmes, Humans and Viruses 2000, http://www.stanford.edu/group/virus/prion/2000/prions.html
John Mumm, Humans and Viruses 1999, http://www.stanford.edu/group/virus/prion/prion2.html
Sources: Prion Biology and Diseases, edited by Stanley B. Prusiner, 2004
Viruses and Human Disesase, James and Ellen Strauss, 2002
Journal of Virology, Race RE and Raymond GJ, February 2004.
Check out my pathogen cards:
Crimean-Congo hemorrhagic fever virus
Humans and Viruses, Winter 2004