prions and prion based disease Flashcards
(25 cards)
What is a prion?
A non-living, infectious particle/ agent.
It is a protein molecule
Can be transmitted in the same ways that infectious organisms (viruses) can be to cause infectious disease
Give 4 examples of prions:
BSE - Bovine Spongiform Encephalitis (Mad cow disease)
CJD - Creutzfeldt Jakob disease
Scrapie
Kuru
What is Kuru?
In 1950s, a tribe of people practiced cannibalism in New Guinea. They consumed human flesh containing prions to honour members of the dead by eating their brains. They then were associated with shivering disease.
Where do prions accumulate?
Brain and spinal cord
Who isolated the first prion and when?
Stanley Prusiner and team in 1980s from a scrapie-infected sheep
When the first prion was isolated, what did research lead to?
Sequencing of the protein led to a discovery that the protein indentified with the PrP gene, expressed in the brain.
Give two types of prion and a description:
- PrP-sen (non-disease causing) typical/normal variant protein
- PrP-res (disease causing) atypical variant protein
What do the terms ‘sen’ and ‘res’ refer to?
Sen - Sensitive to degradation in body
Res - Resistant - cannot be broken down and therefore accumulates in body
How are the sen and res types of prion different?
Folding is different in structure
Both have alpha-helices, res type has more beta-pleated sheets.
What is the current theory for the role of PrP-sen in the body?
Present in large numbers in nerve cells, may be involved in communication between nerve cells; sleep patterns and in cell death.
How are prions different from viruses and bacteria?
Prions have no genetic material
Made of proteins and amino acids
How do PnP-res accumulate in the body?
Mechanisms not fully understood
Upon contact with sen isoform, res isoform of protein converts sen to res
leading to accumulation of res proteins
explaining why diseases lead to progressive neurological degeneration.
Prions stack into long chains, what are these called?
Amyloid fibres - toxic to nerve cells. Accumulation leads to cell death.
What are astrocytes?
cells that move through the brain and digest dead nerve cells, leaving gaps in tissue.
Different prions affect different regions of the brain - symptoms vary. Give four examples:
Cerebral cortex - Classic CJD
Thalamus - fatal familial insomnia
Brain stem - Scrapie, BSE and chronic wasting disease
Cerebellum - Kuru
What is BSE?
Bovine Spongiform Encephalitis (BSE). First seen in 1980s in the UK.
BSE is a progressive neurodegenerative disease of cattle, affecting the brain and spinal cord
Cattle on UK farms started displaying symptoms: Aggression, weight loss, lack of coordination and ability to walk
In 1990s human diseases similar to BSE in cattle started to occur in the UK with symptoms like: dementia, weakened muscles and a loss of coordination.
How was BSE transferred from cattle to humans?
Consumption of contaminated beef.
What is an incubation period?
The period between exposure to an infection and the appearance of first symptoms
What does BSE look like under the microscope after a biopsy?
Spongy appearance
What is CJD?
Creutzfeldt-Jackob Disease Neurodegenerative disease in humans Symptoms similar to BSE. Always fatal Can occur as sporadic disease or it can be inherited No treatment
If a disease is sporadic what does this mean?
Randomly occurring, no pattern of tranmission
How do you detect CJD
Presence of 14-3-3 protein in cerebrospinal fluid
Prions cause what?
Transmissible Spongiform Encephalitis (TSE)
There are two types of Scrapie, what are they?
Typical -(affects 2-5year old sheep) transmitted via colostrum/milk
Atypical- (affecting animals >5years old) less contagious
