Prions

Question 1

What are prions?

Answer 1

unusual infectious agents associated with a number of human, animal and fungal diseases

• they lack a nucleic acid genome like other pathogens
• “proteinaceous”

Question 2

How do prions cause disease?

Answer 2

converting normal protein into more abnormal forms

- can be acquired endogenously by mutation or inheritance, or can be acquired exogenously via ingestion

Question 3

What are the most common prion disease that infects sheep?

Answer 3

scrapie

Question 4

What is the most common prion disease in cattle?

Answer 4

bovine spongiform encephalopathy

Question 5

What is the most common prion disease in cattle?

Answer 5

chronic wasting disease

Question 6

What is the most common prion disease in humans?

Answer 6

kuru

creurzfelt jakob disease

Question 7

What is the typical pathology of a disease caused by prions?

Answer 7

will show as being large vacuoles in the CNS, accompanied by motor disturbances - almost all prion diseases have this

Question 8

How long does it take for an infection of prions to develop?

Answer 8

1-35 years between infection and the presence of symptoms

– very slow progression

Question 9

How large approximately is a prion?

Answer 9

30-35 kDa

Question 10

Where are prions typically expressed?

Answer 10

Typically expressed on the surface of nerve cells

Question 11

What are the two different parts of a prion?

Answer 11

PrPc and PrPSc

Question 12

What is the PrPc portion of a prion and what does it do?

Answer 12

• uninfective
• alpha helical conformation
• protease susceptible

Question 13

What is the PrpSc portion of the prion and what does it do?

Answer 13

• infective
• beta sheet
• protease resistant- accumulation

Question 14

Normal cells express ____ at the cell membrane as linear proteins

Answer 14

PrPc

Question 15

____ exists as a free globular glycoprotein, which can interact with PrPc

Answer 15

PrPSc

Question 16

____ is released from the cell membrane and is converted into _____

Answer 16

PrPc

converted to — PrPSc

Question 17

Cells then produce more ____ and the cycle is repeated

Answer 17

PrPc

Question 18

_____ accumulates as plaques and is internalized by cells

Answer 18

PrPSc

Question 19

What are the two ways that prion disease can be developed and transmitted?

Answer 19

• 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

Question 20

What are the different ways that prions are shed from the body?

Answer 20

• skin, feces, urine, milk, nasal secretions, saliva, placenta

Question 21

Are prion diseases likely to cross between species?

Answer 21

yes

Question 22

Describe the diagnosis process of prions?

Answer 22

• difficult, as there is no culturing or serology required
• no inflammation
• tonsillar tissue however is a good source of PrPSc

Question 23

What is the treatment regimen or prions?

Answer 23

• none to date

- experimental studies being done in rodents