Prions

Question 1

What is a prion

Answer 1

Protinacious infectious particles

- no nucleic acids!!

Question 2

Chronic Wasting Disease

Answer 2

Progressive, fatal neurological disease of captive and/or free ranging mule deer, mule deer hybrids, black and white tailed deer, Rocky Mountain elk in NA

• mule deer: 1-14.3%
• elk: 1-2.4%
• moose: 1%
• reported in 25 states (including MS)
• import infected animals from states with CWD

Question 3

Which prion is in sheep

Answer 3

Scrapie

• incubation period: 2-5 years
• transmission: contact with placenta and placental fluids, oral
• sheep may live 1-6 months after onset of clinical signs
• spread in Europe and North America, sporadically Africa and Asian

Question 4

How to inactivate a prion

Answer 4

Only incineration can destroy/inactivate

• combo of chemical and physical inactivation
• temp of 100 C is necessary to destroy prion, but is impractical to environment
• incinerate brain, spinal cord, eye

Question 5

What is prohibited in the food chain with regard to cattle

Answer 5

Cattle by-products

- brain, trigeminal ganglia, eye, skull, tonsils, dorsal root ganglia, vertebral column, spinal cord, distal ileum

Question 6

How are prions transmitted

Answer 6

Oral or intracerebral routes

Question 7

Control of mad cow disease

Answer 7

• control in UK: exclusion meat, offal, and other materials from cattle for feed products
• EU: restrict import of beef, live cattle, meat, bone meal, and other cattle products from UK
• biohazard: UK declared BSE agent as a human pathogen, so lab safety precautions for Creutzfelt-Jacob disease

Question 8

Characteristics of prions

Answer 8

• incubation period of 1.5 to 30 years
• most infectious particles concentrate in brain, spinal cord, not in muscles
• resistant to UV and gamma-irradiation
• no detectable acquired immune response
• basic lesions: spongiform degeneration of the brain, astroglial hypertrophy and proliferation

Question 9

PRNP gene

Answer 9

Ubiquitous, high levels in neurons and follicular dendritic cells

Question 10

PrPc

Answer 10

Normal cellular isoform, 209 amino acids, function is unclear but important in myelin maintenance

Question 11

PrPsc

Answer 11

Abnormal conformer, same amino acids, convert PrPc into PrPsc molecules
- PrPsc builds up, creates microscopic plaques = neuronal degeneration and neurological dysfunction

Question 12

Prions result in a _______ change

Answer 12

Conformational

- modify protein functions, cellular phenotypes, cause fatal disease

Question 13

Clinical sings of CWD

Answer 13

Weight loss, lose appetite, salivate, polydipsia, grind teeth, polyuria, stay away herds, walk in patterns, carry head low, die a few months with clinical signs

Question 14

CWD infected cervids harbor prion aggregates in:

Answer 14

Pancreas, adrenal gland, peripheral nerves, muscle, lymphoid tissues throughout the body

Question 15

Where to find prions after CWD infection

Answer 15

• lymph node, tonsils, Peyer’s patches within 3 months post oral exposure
• detected in dorsal motor nucleus of vagus nerve by 6 months

Question 16

Transmission of CWD

Answer 16

Feces, saliva, urine from prion infected deer and vertical transmission

Question 17

Prion reservoirs in the environment

Answer 17

Prion binding to soil components increases the chance of future infection
- prion maintains infectivity when bound to minerals