9.2 Prions And Prion Diseases Flashcards
What is the definition of a prion?
A proteinaceous infectious particle ,, prion disease is caused by a change in shape of cellular protein and the term ‘prions’ refers to abnormal, pathogenic agents that are transmissible and are able to induce abnormal folding of specific normal cellular proteins called prion proteins that are more abundantly found in the brain.
Describe ‘recruitment’
When PrPsc directly contains PrPc, catalyse conversion of PrPc to beta sheet structure changing it to PrPsc (recruitment)
Give two characteristics of TSE
Long incubation periods (months to years) + progressive and fatal disease that affects the central nervous system
What are the differences between sporadic and new variant CJD?
Sporadic
- dementia and recurrent seizures
- several year incubation period
- death after a few months of symptoms
What is the typical pathology associated with spongiform encephalopathy in humans?
It multiples in the spleen, spreads to central nervous system and is not visible inflammation wise or immune response wise
Compare and contrast the PrPc and PrPsc proteins
PrPc (prion cellular) ,, alpha helix structure, normal cellular PrP, found on the surface of neuron’s + function unknown
PrPsc (prion scrapie) ,, beta sheet structure, abnormal PrP, different tertiary structure + copy itself by recruitment
Briefly describe a model for the formation of PrPsc
The formation of PrPsc results from a mutation in the PrP gene which encodes for an abnormally conformed and unstable PrP with the propensity to convert into PrPsc.
How does the prion hypothesis explain the inheritance of familial forms of CJD?
The protein only hypothesis posits that prion self replicates by conveying the infectious protein conformation to its normally folded counterpart
How does the prion hypothesis explain the appearance of spontaneous CJD?
The protein only hypothesis posits that prion self replicates by conveying the infectious protein conformation to its normally folded counterpart
How is the epidemic of vCJD being controlled?
To prevent cows from getting BSE
How is iatrogenic transmission of CJD prevented?
Tightened guidelines on the reuse of surgical equipment
What evidence is there for CJD being an infectious disease?
Comes from contaminated meat
What evidence is there for CJD being an inherited disease?
10-15% of CJD is inherited, autosomal dominant pattern f inheritance
What is kuru and how is it transmitted?
A disease similar to scrapie but identified in humans, it is transmitted to chimps by injections of kuru brain directly into the cerebellum. This can be considered ritualistic cannibalism and is transmitted via the inoculation of infected material onto mucous membranes.
How did BSE (mad cow disease) start?
The protein derived from waste meat products and the bonemeal from sheep and cattle was used as a food supplement. Scrapie is an epidemic in Britain and it was assumed that this was the source of the infectious agent in the feed. Scrapie then crossed species barriers to cause BSE and thus the meat from cattle was consumed by humans.
