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Parasitology > T.bruci AV > Flashcards

T.bruci AV Flashcards

1
Q

What is the name of the African trypanosome?

A

T.brucei

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2
Q

What are the two forms of T.brucei?

A

T.brucei rhodesiense

T.brucei gambiense

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3
Q

Which form of T.brucei is the West African form?

A

T.brucei gambiense

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4
Q

Which form of T.brucei is the East African form?

A

T.brucei rhodesiense

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5
Q

Which form of T.brucei has an extensive reservoir in ungulates?

A

Rhodesiense

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6
Q

East African?

A

Rhodesiense

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7
Q

West African?

A

Gambiense

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8
Q

Which form of T.brucei primarily infects humans?

A

Gambiense

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9
Q

Are the East and West African forms morphologically distinguishable?

A

No

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10
Q

Lifecycle stages?

A

1) Metacyclic trypomastigotes are injected
2) Form blood stream trypomastigotes
3) Binary fission
4) Taken up by tsetse fly and become procyclic trypomastigotes in the midgut
5) Binary fission
6) Become epimastigotes as they leave the midgut, move to the salivary gland
7) Binary fission
8) Becomes metacyclic trypomastigotes

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11
Q

How many stages of infection are there?

A

Two

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12
Q

What occurs in the first stage of infection?

A

There is cyclic/relapsing fever

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13
Q

What occurs in the second stage of infection?

A

There is penetration of the blood-brain barrier, they infect the CNS

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14
Q

What are the symptoms of the second stage of infection?

A

Confusion
Loss of coordination
Interruption of sleep cycle

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15
Q

What disease does T.brucei cause?

A

Sleeping sickness

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16
Q

What is the antigenic variant present?

A

VSG

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17
Q

VSG stands for?

A

Variant Surface Glycoprotein

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18
Q

VSG is attached via a?

A

Lipid GPI anchor

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19
Q

Which form is VSG coat not present in?

A

The procylic form

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20
Q

What does the procyclic form have?

A

A procyclin invariant coat

21
Q

VSGs all share a?

A

Conserved tertiary structure

22
Q

VSG coat is internalised every?

A

12 minutes

23
Q

Where does endocytosis occur?

A

Flagellar pocket

24
Q

The movement of T.brucei generates?

A

Hydrodynamic forces

25
Q

What do the hydrodynamic forces do?

A

They cause the rearward translocation of VSG

26
Q

VSG antibody complexes move towards the flagellar pocket faster as?

A

The antibody acts as a sail

27
Q

What is the flagellar pocket?

A

It is where the flagellum emerges
It is where endocytosis takes place
It is a membrane invagination

28
Q

What is located posterior to the flagellar pocket, flagellum and basal bodies?

A

Kinetoplast DNA

29
Q

VSG expression sites are located where?

A

At telomeres

30
Q

What are VSG bloodstream expression sites?

A

Polycistronic transcriptional units

31
Q

VSG bloodstream ES are located where?

A

Telomeres

32
Q

VSG bloodstream ES encode?

A

VSG gene

ESAGs

33
Q

ESAGs?

A

Expression Site Associated Genes

34
Q

Expression sites are transcribed by?

A

RNA Pol I

35
Q

How can VSG expression be switched?

A
  • Expression site switch
  • Telomere exchange
  • Duplicative gene conversion
  • Segmental gene conversion
36
Q

What does duplicative gene conversion require?

A

5’ homology = 70bp repears

3’ homology= part of VSG, conserved 3’ region of VSG genes

37
Q

How many VSG genes and pseudogenes are there?

A

> 1500

38
Q

What produces chimaeric/mosaic VSG?

A

Segmental gene conversion

39
Q

What are telomeres?

A

Highly recombinogenic regions of the genome

40
Q

Where can VSG genes be located?

A

ES sites
Telomeres
Subtelomeres

41
Q

What is always located at the telomeres?

A

VSG expression sites (ES)

42
Q

Switching from one variant is not random as there is a?

A

Preferential hierarchy of VSG activation, switch is not a random process

43
Q

What are the mechanisms of T.brucei immune evasion?

A
  • Dense VSG coat
  • Sheltering invariant surface receptors
  • Invariant surface receptors in the flagellar pocket
  • Coat cleaning
  • Antigenic variation
44
Q

Metacyclic trypomastigotes express what and why?

A

VSG in preparation for entry into humans

45
Q

How many MC-ES?

A

~25

46
Q

Similarities between B-ES and M-ES?

A

Both telomeric

Both transcribed by RNA Pol I

47
Q

Main difference between M-ES and B-ES?

A 
M-ES has ~25 ES
Promoter directly upstream of VSG gene
No ESAGs, only VSG is expressed
Inefficient/no gene conversion due to the lack of 70bp repeats 
Monocistronic
48
Q

B-ES is?

A

A polycistronic transcriptional unit

49
Q

M-ES is?

A

A monocistronic transcriptional unit

Parasitology (17 decks)

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