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Y3 Medical Micro > L8 Prions and TSE > Flashcards

L8 Prions and TSE Flashcards

1
Q

what are prion diseases

A

group of fatal neurodegenerative disorders

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2
Q

what do prions infect

A

humans and animals

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3
Q

where does the prion disease affect

A

CNS neurodegeneration usually with spongiform change – PrPSc accumulation

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4
Q

how are prions transmitted

A

experimentally

naturally

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5
Q

what is the histology of normal cerebellum like

A

no gaps between cells here

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6
Q

what is the histology of spongiform cerebellum

A

Vacuoles within cells = give brain characteristic spongy texture

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7
Q

what are prion diseases known as

A

spongiform encephalopathies

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8
Q

what do prions affect

A

brain

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9
Q

what is transmissible dementias

A

dementia is a cardinal feature of these transmissible features

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10
Q

what transmissible spongiform encephalopathies/transmissible dementias/prion diseases infect humans

A

kuru
creutzfeldt-jacob disease
gerstmann-straussler syndrome

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11
Q

what is BSE

A

bovine spongy forming encephalopathies

infects cows

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12
Q

what is scrapie

A

prion disease that infects sheep

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13
Q

what is TME

A

prion disease that infects mink

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14
Q

what is chronic wasting disease

A

prion disease that infects mule deer, elk

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15
Q

what are TSE proteins sensitive to

A

proteases
SDS
phenol

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16
Q

what are the TSE nucleic acids resistant to

A 
nucleases (DNase, RNase)					
ionising or UV irradiation				
psoralen photoadducts			
hydroxylamine					
aldehydes
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17
Q

what do TSE causative agents include

A

protein
no evidence causative agent contains nucleic acid
scrapie associated fibrils
PrP 27-30

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18
Q

how can TSE have reduced infectivity

A

treat in a way to alter protein structures

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19
Q

what is SAF

A

scrapie-associated fibrils

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20
Q

what are the single protein species in scrapie

A

PrP27-30

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21
Q

what is PrP from

A

PrP33-35

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22
Q

where is PrPc present

A

it is a normal cellular gene that we all have encodes PrPc

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23
Q

which PrP 33-35 is sensitive to proteinaseK

A

PrPc 33-35

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24
Q

what is PrPSc 33-35 digested to

A

proteinase K resistant digested to PrP 27-30 and no further digestion

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25
Q

what causes prion disease

A

when PrP27-30 is made and no further digestion leads to accumulation

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26
Q

what causes scrapie

A

PrPSc accumulates in scrapie infected brains

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27
Q

what differs in the brain of infected and normal

A

infective brain is protease resistant but normal brain is sensitive – different protein structure of PrPC

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28
Q

what are the PrP isoforms

A

PrPC 33-35

PrPSc 33-35

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29
Q

when is there change in the PrP isoforms

A

post translational

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30
Q

what is the biochemical difference to PrP isoforms

A

none

same gene sequence, mRNA, amino acid sequence

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31
Q

what happens when PrPc is present in infected = lifecycle

A

PrPC sporadic structural change to PrPSc

PrPSc digested to PrP27-30 and is stuck

PrP27-30 catalyses conversion of PrPC into PrPSc

= large amounts of indigestible PrP27-30

= neurodegenerative disease

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32
Q

what are the routes of infection for scrapie

A

intra-cerebral
oral – spread along vagus nerve to brainstem OR splanchnic sympathetic nerves to spinal cord
accumulation in lymphoid tissue e.g. spleen

33
Q

what does Kuru, CJD and GSS cause

A

dementia

cerebellar syndrome

34
Q

what is the incubation period for Kuru like

A

5-40 years

35
Q

how are kuru, CJD, GSS diagnosed

A

clinical

brain has spongy characteristic post mortem

36
Q

how long is survival with kuru, CJD, GSS

A

less than a year

37
Q

where are human TSEs present

38
Q

how many cases of human TSEs are there

A

1 million a year (not common disease)

39
Q

is it genetic disease

A

familial forms (some patients that develop it have a family history)

40
Q

what is the age at onset for human TSEs

A

7th decade

41
Q

what is the change in the PrP to make it a scrapie one

A

have a specific gene

protein converting into scrapie conformation misfolding of protein

42
Q

what is the cause of GSS

A

chromosome has a leucine present

whereas normal one doesnt

43
Q

what is the cause of familial CJD

A

has a lysine present

44
Q

what causes iatrogenic CJD

A

modern medicine

  • corneal transplant
  • eeg electrodes not sterile into brain
  • neurosurgery
  • dura mater graft (dura meter fill holes when part brain removed contains CJD)
  • human pituitary-derived hormones
45
Q

ways to get CJD

A

inherit mutated prion gene
prion protein turns to scrapie form
modern medicine can cause it

46
Q

how was scrapie treated

A

FSH pituitary derived hormone

47
Q

when was bovine spongiform encephalopathy identified

48
Q

how is ovine/bovine spongiform encephalopathy transmitted

A

ingestion of contaminated meat/bone meal

49
Q

how does vCJD differ to CJD

A

younger age onset of new variant CJD – looks like new disease in younger people

50
Q

what did all vCJD have

A

all in methionine 129 homozygotes

51
Q

what is the vCJD prion from

52
Q

what is the treatment course length for vCJD

A

average 14 months

53
Q

what is the prion distribution like in vCJD

A

distribution unusual – found in peripheral lymphoid tissue preclinically
florid plaques within brain

54
Q

where is it thought people caught vCJD

A

eating meat

55
Q

if you were MM% PRNP codon 129 what is it likely you would get

A

vCJD 100% or 62% sCJD

56
Q

how many are incubating vCJD

57
Q

how can vCJD be spread - secondary

A

secondary spread e.g. via blood donation, surgical instruments

58
Q

how are vCJD studied

A

tonsillectomy studies – stain for abnormal prion protein

59
Q

what does PrP stand for

A

prion protein

60
Q

where does the word prion come from

A

proteinaceous infective material

61
Q

what is the PRPC -C suffix mean

A

cellular prion protein

62
Q

what is the PRPSc -Sc suffix mean

63
Q

what is the PRPres -res suffix mean

64
Q

what causes the spongiform texture

A

intracellular vacuoles

65
Q

what is the role of the gene in prions disease

A

non they are the same as in healthy cells

66
Q

what is the role of mRNA in prions disease

A

non they are the same as in healthy cells

67
Q

what is the role of protein in prions disease

A

healthy cells = PrPC, protease sensitive

infected cells – PrPSc or PrPRes, protease resistant

68
Q

what is the difference between the healthy and infected protein

A

3D structure has 40% more beta sheets

69
Q

what is the difference between the PrPC and PrPSc

A

there is post translational changes

no biochemical difference found

70
Q

how many PrPSc are needed for neurodegenerative disease

A

1 as the loop is continuous

71
Q

what happens if PrP27-30 injected into healthy person

A

PrPC forms PrPSc and continuous cycle and causes own accumulation

72
Q

how is scrapie treated

A

no treatment

73
Q

what is the cause of sporadic CJD

A

there are no mutations

74
Q

what is the annual risk of PrPC to PrPSc conversion

A

1 in a million

75
Q

what is the risk of PrPSc generation if have familial CJD mutation

76
Q

what happened when it was found that cows were spreading scrapie

A

ban on meat/bone meal 1988

77
Q

what was the problem with the ban of meat/bone meal

A

cattle had consumed it already so were infected

78
Q

what are the amino acids at PRNP codon 129

A

encode methionine or valine

Inherit one from mother and one from father = can be MM / MV / VV

Y3 Medical Micro (16 decks)

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