Prions Flashcards
what are prions
protein infectious particles that lack nucleic acid
Stanly Prusiner’s ‘protein only prion theory’
what types of prion diseases effect cattle sheep elk humans
cattle: BSE (can transfer to humans)
sheep: scrapie
Elk: chronic wasting disease
humans: kuru, creutzfeidt-jakob disease
what is the pathology for prions
large vacuoles in CNS, motor disturbances
slow disease 1-35 years between infection and symptoms (vCJD)
what is the weight of a prion
where is it mainly expressed
30-35kDa host encoded glycoprotein
expressed mainly on the surface of nerve cells
PrPc
uninfective
alpha-helical conformation
protease susceptible
PrPsc
infective
beta-sheet
protease resistant -accumulation (wont break down)
how can a PrPc become a PrPsc
normal cells express PrPc at the cell membrane as linear proteins
PrPsc exists as a free globular glycoprotein, which can interact with PrPc
PrPc is released from the cell membrane and is converted into PrPsc
cells produce more PrPc and teh cycle repeats
PrPsc accumulates as plaque and is internalized by cells
how do prion diseases develop and transmit
mutations in codon 129 of PrPc in chromosome 20
CJD and two other human diseases -Gertsmann-Scheinke syndrome and fatal familial insomnia
exposure:
contaminated food, medical products (latrogenic) -blood/transplants, surgical equipment (strong binding to metal surface)
prion mother to fetus transmission?
no conclusive proof but speculated
how can prions shed
skin feces urine milk nasal secretions saliva placenta
can humans get scrapie from sheep?
no
where can we get CJD from?
prions from cattle become a new variant in humans to become CJD
kuru spread by cannibalism
diagnosis of prions
difficult
no culturing or serology
no inflammation
tonsillar tissue, good source of PrPsc
treatment of prions
none to date
experimental studies in rodents
polyanionic nd tricyclic compounds -extend life
mucosal vaccine
