Section 8 - Prions

Question 1

What do classical pathogens all contain?

Answer 1

Nucleic acid

Question 2

Define prions

Answer 2

Proteinaceous infectious particles that lack nucleic acid

Question 3

Prions are highly resistant to ______

Answer 3

Denaturation by temperature or pH

Question 4

How do prions cause disease?

Answer 4

By converting normal protein into further abnormal forms

Question 5

What disease do prions cause in sheep?

Answer 5

Scrapie

Question 6

What disease do prions cause in cattle?

Answer 6

Bovine spongiform encephalopathy (BSE)

Question 7

What disease do prions cause in elk?

Answer 7

Chronic wasting disease

Question 8

What diseases do prions cause in humans?

Answer 8

Kuru and Creutzfeldt-Jakob disease (CJD)

Question 9

What is the main pathology of prions?

Answer 9

Poke holes (through large vacuoles) in the CNS

Question 10

Are diseases caused by prions slow or fast diseases?

Answer 10

Slow

Question 11

What are prion proteins?

Answer 11

Host-encoded glycoproteins

Question 12

Where are prion proteins expressed?

Answer 12

Surface of nerve cells

Question 13

What are characteristics of PrPc?

Answer 13

• Uninfective
• Alpha helix
• Protease susceptible
• Found in everyone

Question 14

What are characteristics of PrPsc?

Answer 14

• Infective
• Beta sheet
• Protease resistant

Question 15

What does PrPsc exist as?

Answer 15

A free globular glycoprotein

Question 16

Can PrPsc and PrPc interact with each other?

Answer 16

Yes

Question 17

Where is PrPc released from and what is it converted into?

Answer 17

• Released from the cell membrane

- Converted into PrPsc

Question 18

What happens to PrPsc?

Answer 18

It accumulates as plaques and is internalized by cells, causing holes in the brain

Question 19

There is high concentration of prions in the ______

Answer 19

Tonsils

Question 20

How can prion diseases arise?

Answer 20

• Endogenously by mutation or inheritance

- Exogenously during medical procedures or by ingestion of contaminated material

Question 21

What mutation causes prion diseases, and what diseases does this mutation cause?

Answer 21

• Mutation in codon 129 of PrPc in chromosome 20

- CJD, Gertsmann-Straussler-Scheinker syndrome, and fatal familial insomnia

Question 22

How can prions be transmitted through contaminated food?

Answer 22

Prions survive digestion and are taken up across the intestinal mucosa

Question 23

Prions have strong binding to _____

Answer 23

Metal surfaces

Question 24

How can prions be shed?

Answer 24

Skin, feces, urine, milk, saliva, placenta, and nasal secretions

Question 25

Is there evidence of cross-infection between species?

Answer 25

No

Question 26

Why is diagnosis of prion diseases difficult?

Answer 26

• Long time for symptoms to emerge
• No culturing
• No inflammation

Question 27

Why don’t prions produce inflammation?

Answer 27

Because they aren’t recognized as foreign agents

Question 28

How are prions identified?

Answer 28

Through antibodies

Question 29

What is the treatment for prion diseases?

Answer 29

None to date, but studies in rodents

Question 30

________ provide some protection against prions when given shortly after infection

Answer 30

Polyanionic and tricyclic compounds