(6-15) Cannibals & Cows [Prions] Flashcards
1. Define and differentiate between a virus and a prion. 2. Define transmissible spongiform encephalopathy and describe the etiological agent. 3. Describe and explain the major symptoms of transmissible spongiform encephalopathies. 4. Describe the proposed replication method of prions
What are the symptoms of Kuru?
- Unsteady gait
- Slurring of speech
- Muscle jerking
- Incontinence
- Lack of immune response
What is the cause of symptoms in kuru?
Brain dysfunction
What is kuru and when did it first arise?
In the early 1900s, a fatal neurodegenerative disease arose in Papua New Guinea
How many of South Fore people (women and children) Died of kuru from 1957 - 1968?
Over 1100
What happened when chimpanzees were injected with brain tissue from Kuru victims?
18 to 21 months later, they developed symptoms similar to Kuru.
How was kuru transmitted from person-to-person in the south fore?
People in the South Fore partake in ritual acts of mortuary cannibalism. The women and children who lived apart from the men cooked and ate their dead relatives.
What did scientists believe that Kuru was?
A slow virus
What is Scrapie?
Neurodegenerative sheep disease first described in early 18th century
What are the symptoms of Scrapie?
Sheep trembled, stumbled, and scraped against fences
How do the brains of Scrapie sheep appear?
Brains were spongiform, hence the disease name, Scrapie spongiform encephelopathy.
How is Scrapie transmitted?
Scrapie is known to be transmissible from one sheep to another via brain tissue
What is a prion?
Proteinaceous Infectious particles, which contain protein, but nut nucleic acid.
How did prions arise?
Prions apparently arose from mutations in the gene encoding normal prion proteins in humans and animals.
What is fractionation?
A process that uses heat to separate a substance into its components.
Can prions “reproduce” without nucleic acids?
- Yes– sort-of.
- Abnormal protein can cause normal cellular protein to change to abnormal form
- PP + NP → PP + PP
How can PP change NP into PP?
PP interacts with NP in such a way as to facilitate the re-folding to the PP confirmation.
How do point-mutations in the NP affect its resistance to prions?
Some point-mutations in the NP make it more prone to abnormal re-folding
How do normal protein conformations differ from abnormal ones?
- Normal protease-sensitive conformation has normal cellular function in cells
- Abnormal protease-resistant conformation accumulates and cause neuron death
How structurally similar are PPs and NPs?
~ PPs were found to be almost identical to a normal human cellular protein (NP)
~Normal protein not protease resistant
~ Sequences are almost identical
~ Explains lack of immune response
What did Stanley Prusiner win the 1997 Nobel Prize in Physiology or Medicine for?
He suggested infectious disease could be transmitted by protein alone.
Why do prions appear to have a long “incubation time”?
Re-folding NP to the PP confirmation continues (slowly) inside neurons until pathology occurs
What is Genetic Creutzfeldt-Jacob Disease (CJD)?
Inheritance of a form of NP that folds into the abnormal form very easily
What is Sporadic CJD, whom does it affect, and how frequently does it occur?
Sometimes your NP spontaneously fold into the abnormal form
~ Rare (1 case in 1,000,000)
~ Primarily in age >45
What is Variant CJD and whom does it affect?
PP from ‘Mad Cows’ leads to disease by re-folding NP
~ Younger people infected
Do cured “mad cows” mean no more Mad Cow Disease in humans?
No. The occurrence of BSE in humans lags behind that in cows.
Which prion disease affects sheep?
Scrapie spongiform encephalophathy
Which prion disease affects cows and humans?
Mad cow spongiform encephalophathy
Which 2 prion diseases affect humans?
- Creutzfeldt-Jacob Disease
2. Kuru spongiform encephalophathy
Which prion disease affects Deer and Elk?
Chronic wasting disease
How did the spread of kuru stop?
The South Fore stopped eating their dead.
Are there still Kuru cases today? Who is affected?
The long incubation time means that even today there are a few kuru cases every year, in 50 to 60 year olds who ate infected tissue as young children.
