Prions are...

"proteinaceous infectious particles that resist inactivation by procedures that modify nucleic acids" as defined by their discoverer, Stanley Prusiner.

History of Prions:

1998 Prions website by Dr.Robert Siegel

Hallmarks of Prions:

- atypical resistance to chemical and UV damage that would usually destroy nucleic acids
- conformational change from PrP(C) to PrP(Sc), in which many alpha helices are changed to beta-pleated sheets
- normal prion protein counterparts in the brain
- at least 20 different strains of prions, each with its own pathology
- three classes of prion diseases - sporadic, inherited and infectious
- no immune response
- latency period (many years between infection and symptoms)

A Heretical Notion:

- Prions violate the Central Dogma of Biology because unlike other pathogens, they do not use nucleic acids (DNA or RNA) to infect their hosts.
- Prions not only cause communicable diseases, but also heritable ones as well.

Questions for the Future:

- What is the precise mechanism of prion infection, are there any cofactors or receptors?
- How are different prion strains targetted to different parts of the brain?
- What is the role of the immune system in the prion pathogenesis?
- What should therapies target, possibly the conversion from normal to mutant form?
- What are the modes of transmissions of prions?
- Exactly how rigid is the species barrier?
- Are there any other disease that are caused by prions?

References:

- Prusiner, Stanley B. "Prions." Proceedings of the National Academy of Sciences USA Vol. 95, p. 13363-133383.
- Flint SJ et al. Principles of Virology: Molecular Biology, Pathogenesis, and Control: Washington D.C.: ASM Press, 2000. p. 546-550.

To get a more indepth background on prions, check out the following resources. . .

12 Excellent Prion Links
Comprehensive Overview
1999 Student Prions Website