PRIONS

Question 1

What does the term prion mean?

Answer 1

“Infectious protein” or “rogue protein”

Question 2

What is a characteristic of ALL prion diseases?

Answer 2

Spongiform degeneration of the grey matter of the brain

Causing **transmissible spongiform encephalopathies

Question 3

What are prions?

Answer 3

Normal cellular proteins that have undergone conformational changes and have become pathogenic

Question 4

What is PrPc?

Answer 4

The normal protein (before it transformed into a prion) alpha helices structure

Question 5

Where are prions most commonly expressed?

Answer 5

Neurons and lymphoreticular cells

Question 6

What is the PrPsc?

Answer 6

The abnormal protein - prion (beta sheet structure)

**has a change in conformation from the normal protein that makes it pathogenic

Question 7

T/F: amino acid sequences of PrPc and PrPsc in a given host are identical

Answer 7

TRUE

Question 8

Who discovered the prion?

Who discovered the kuru prion?

Answer 8

Dr. Prusiner

Dr. Gajdusek

Question 9

T/F: Prions induce inflammatory or immune responses in hosts

Answer 9

FALSE

They DO NOT induce inflammation or immune response

**therefore looking for antibodies will not be a logical dx test – none will be made

Question 10

T/F: Prions are resistant to chemical and physical conditions, such as UV rays

Answer 10

TRUE

Question 11

What are PrPsc aggregates in cells called? (build of of these cells)

Answer 11

Scrapie associated fibrils (SAF)

**can reach high titers

Question 12

How do prions replicate

Answer 12

Normal protein becomes prion protein - then these will accumulate since they are very resistant

The PrPsc catalyses the conversion of PrPc into PrPsc

Question 13

Who does Scrapie dx infect?

Answer 13

SHEEP

Suffolk and Hampshire sheep breeds are more susceptible

Question 14

What is the mode of transmission of scrapie?

Answer 14

*Oral route

Contamination of wounds with placental tissue or body fluids

maybe vertical transmission

Question 15

What clinical signs might you see in a sheep with Scrapie?

Answer 15

Weight loss, pruritus, loss of wool, ataxia, paralysis of hind limbs

Question 16

What might you see on histo of a brain infected with Scrapie?

Answer 16

Neuronal vacuolation and degeneration
astrocytic hypertrophy and hyperplasia
*no inflammatory reaction

Question 17

How do you tx scrapie?

Answer 17

Eliminate the animal

Question 18

How do you dx scrapie?

Answer 18

cased on clinical signs and histopath of brains (immunohistochemistry)

western blot of brain tissue

*ante-mortem sampling of lymphoid tissue of nictitating membrane, tonsils, or rectal mucosa

Question 19

What dx does Bovine spongiform encephalopathy (BSE) cause?

Answer 19

MAD COW DISEASE

Question 20

How is it transmitted?

Answer 20

Through ingestion of infected meat/bone

Question 21

What clinical signs might you see in a cow with BSV?

Answer 21

**mostly in cows 3-5yrs old

temors, decreased milk production, abnormal posture, wt loss, aggression, hind limb ataxia and paralysis

Question 22

How long does it typically take mad cow dz to become fatal?

Answer 22

2-3 weeks, up to 1 year after onset of clinical signs

Question 23

can humans become infected with mad cow dz?

Answer 23

YES!! and cats too

Question 24

What will be seen on histo of a cow with made cow dz?

Answer 24

neuronal vacillations, degeneration and loss of neurons, astrocytic hypertrophy and hyperplasia, lesions in midbrain, brain stem, cervical spine (Test the pons)

Lesions are MININAL in cerebral cortex, cerebellum, hippocampus

Question 25

T/F: There are diagnostics established to test for BSE before clinical signs

Answer 25

FALSE

Dx is based on clinical signs, herd history, immunohistochemistry of brain sample