Prions Flashcards
What are prions?
unusual infectious agents associated with a number of human, animal and fungal diseases
- they lack a nucleic acid genome like other pathogens
- “proteinaceous”
How do prions cause disease?
converting normal protein into more abnormal forms
- can be acquired endogenously by mutation or inheritance, or can be acquired exogenously via ingestion
What are the most common prion disease that infects sheep?
scrapie
What is the most common prion disease in cattle?
bovine spongiform encephalopathy
What is the most common prion disease in cattle?
chronic wasting disease
What is the most common prion disease in humans?
kuru
creurzfelt jakob disease
What is the typical pathology of a disease caused by prions?
will show as being large vacuoles in the CNS, accompanied by motor disturbances - almost all prion diseases have this
How long does it take for an infection of prions to develop?
1-35 years between infection and the presence of symptoms
– very slow progression
How large approximately is a prion?
30-35 kDa
Where are prions typically expressed?
Typically expressed on the surface of nerve cells
What are the two different parts of a prion?
PrPc and PrPSc
What is the PrPc portion of a prion and what does it do?
- uninfective
- alpha helical conformation
- protease susceptible
What is the PrpSc portion of the prion and what does it do?
- infective
- beta sheet
- protease resistant- accumulation
Normal cells express ____ at the cell membrane as linear proteins
PrPc
____ exists as a free globular glycoprotein, which can interact with PrPc
PrPSc
____ is released from the cell membrane and is converted into _____
PrPc
converted to — PrPSc
Cells then produce more ____ and the cycle is repeated
PrPc
_____ accumulates as plaques and is internalized by cells
PrPSc
What are the two ways that prion disease can be developed and transmitted?
- mutations in codon 129 of PrPc in chromosome 20
(happens in CJD and 2 other human diseases- Gertsmann-Straussler-Scheinker syndrome and fatal familial insomnia) - exposure to infective agents (most common)
– contaminated food, contaminated medical products, contaminated surgical instruments, mother- fetus transmission
What are the different ways that prions are shed from the body?
- skin, feces, urine, milk, nasal secretions, saliva, placenta
Are prion diseases likely to cross between species?
yes
Describe the diagnosis process of prions?
- difficult, as there is no culturing or serology required
- no inflammation
- tonsillar tissue however is a good source of PrPSc
What is the treatment regimen or prions?
- none to date
- experimental studies being done in rodents
