Prions.pdf

Transmissible spongiform encephalopathies (TSEs) are a group of diseases caused by abnormal prion proteins, including variant Creutzfeld-Jacob disease (vCJD), scrapie in sheep, and bovine spongiform encephalopathy (BSE or mad cow disease) in cattle. TSEs create large fluid-filled holes in brain tissue, leading to symptoms such as coordination and balance problems, shakiness, and uncontrollable jerking movements. In humans, TSEs also cause personality changes, depression, confusion, memory problems, and insomnia, ultimately resulting in the loss of most mental functions and death.

Prions are specific proteins found mainly in the nervous system, where they may have important functions, such as in memory formation. Infectious prions are abnormal forms of prion proteins that replicate inside the host, forcing normal proteins to adopt the aberrant structure, leading to disease. Prions are the only known self-propagating pathogenic proteins, able to cause severe illness without containing nucleic acids.

Research into prions began in the 1960s, and Stanley Prusiner was awarded the Nobel Prize in Physiology or Medicine in 1997 for his work on prions and TSEs. The "protein-only hypothesis" suggests that prions are the causative agents of TSEs, and recent studies have provided further evidence for this theory. The most worrying prion strain is the one that causes vCJD, which has crossed the species barrier to infect humans, with 168 reported deaths in the UK and cases in other countries.

The main infection route for vCJD is thought to be through eating infected beef, but prions could also be spread through blood transfusions, as they have been found in tissues such as blood, tonsils, and appendices. This opens up new ways of transmission to the entire population, not just the elderly. Scientists fear a vCJD epidemic due to the potential for widespread infection and the lack of a cure or preventative measures.