Section 8 - Prions Flashcards
What do classical pathogens all contain?
Nucleic acid
Define prions
Proteinaceous infectious particles that lack nucleic acid
Prions are highly resistant to ______
Denaturation by temperature or pH
How do prions cause disease?
By converting normal protein into further abnormal forms
What disease do prions cause in sheep?
Scrapie
What disease do prions cause in cattle?
Bovine spongiform encephalopathy (BSE)
What disease do prions cause in elk?
Chronic wasting disease
What diseases do prions cause in humans?
Kuru and Creutzfeldt-Jakob disease (CJD)
What is the main pathology of prions?
Poke holes (through large vacuoles) in the CNS
Are diseases caused by prions slow or fast diseases?
Slow
What are prion proteins?
Host-encoded glycoproteins
Where are prion proteins expressed?
Surface of nerve cells
What are characteristics of PrPc?
- Uninfective
- Alpha helix
- Protease susceptible
- Found in everyone
What are characteristics of PrPsc?
- Infective
- Beta sheet
- Protease resistant
What does PrPsc exist as?
A free globular glycoprotein
Can PrPsc and PrPc interact with each other?
Yes
Where is PrPc released from and what is it converted into?
- Released from the cell membrane
- Converted into PrPsc
What happens to PrPsc?
It accumulates as plaques and is internalized by cells, causing holes in the brain
There is high concentration of prions in the ______
Tonsils
How can prion diseases arise?
- Endogenously by mutation or inheritance
- Exogenously during medical procedures or by ingestion of contaminated material
What mutation causes prion diseases, and what diseases does this mutation cause?
- Mutation in codon 129 of PrPc in chromosome 20
- CJD, Gertsmann-Straussler-Scheinker syndrome, and fatal familial insomnia
How can prions be transmitted through contaminated food?
Prions survive digestion and are taken up across the intestinal mucosa
Prions have strong binding to _____
Metal surfaces
How can prions be shed?
Skin, feces, urine, milk, saliva, placenta, and nasal secretions
