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HELENP CBG VIROLOGY AND IMMUNITY > CBG Lecture 22: Virus Cell Interactions > Flashcards

CBG Lecture 22: Virus Cell Interactions Flashcards

1
Q

what morphological effects do viruses have on host cell

A

effects on nucleus (nuclear inclusion)
inclusion bodies: due to virus factories sometimes remain till cell lysis
cytoskeletal effects
syncytia giant cell formation

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2
Q

what are inclusion bodies

A

viral replicating factories

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3
Q

what cytoskeletal changes do viruses have on cells

A

RNA virus is associated with microtubules so changes the cytoskeleton and bends cell into new shapes

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4
Q

what are syncytia

A

giant cell formaiton -giant multinucleate cell caused by fusion of infected and non infected cell due to viral envelope

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5
Q

which viruses use syncytia

A

measles and retroviruses

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6
Q

outline main effects viruses have on host cells

A
  1. morphological
  2. biochemical
  3. genetic
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7
Q

what biochemical effects do viruses have on host cell

A
  1. activate cellular protein kinases and transcription factors
    activates cell oncogenes, cell cycle arrest
    inhibit DNA synthesis
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8
Q

what genetic effects do viruses have on host cell

A

genralised chromosomal damage
transformation
introduction of oncogenes

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9
Q

give example of induced viral defence

A

interferon stimualtion of cells which acts to induce a viral state

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10
Q

what does interferon effect the activation of

A

transcription, translation, protein processing and virus maturation inhibitors

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11
Q

how does interferon block viral activation of transcription inhibitor

A

by blocking mRNA synthesis

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12
Q

how does interferon block viral activation of translation inhibitor

A

by blocking mRNA cap methylation, viral RNA function and tRNA

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13
Q

how does interferon block viral activation ofprotein processing inhibior

A

by blocking protein glycosylation

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14
Q

how does interferon block viral activation of virus maturation inhibiot

A

by blocking glycoprotein maturation and budding

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15
Q

what is the HIV combination theory

A

combo of different drugs allowing normal lifespan for HIV sufferes :AZT to inhibit RT, then protease -> attack many stages of lifecycle

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16
Q

give an exmaple of induced effect by TIP

A

activation of TIP = translation inhibitory protein

17
Q

how does TIP activation work

A

interferon binds to outside of cell
TIP produces TIP RNA, translated = TIP protein, bunds to ribosome and modifies it slowing its speed but makes ribosome more careful about the RNA it translates therefore more likely to transfer host RNA and not viral

18
Q

what is a viral counterdefernce to TIP activation

A

Influenza has a cap snatching mechanism, it original RNA is capless but takes host cap and puts on its virus therefore host cant get its protein

19
Q

give an example of a non induced effect against retrovirus

A

APOBEC3G defends against retroviruses (HIV has overcome this defence by acquisition of vif gene -viral infectivity factor gene)

20
Q

how has HIV overcome APOBEC

A

acquired vif gene

21
Q

how does non induced APOBEC effect work

A

APOBEC is human antiviral defence eenzyme which catalyses the deamination of C to U in ssDNA on noncoding strand (G -> A on coding strand) this is HYPERMUTATION

22
Q

how does vif work

A

vif gene disrupts the antiviral activity of APOBEC by targeting it for ubiquitination

23
Q

what is base change caused by APOBEC

A

hypermutation of C to U in ssDNA non coding strand which is G to A hypermutation on coding

24
Q

despite vif, on what % of viruses does APOBEC work

A

30%

25
Q

what is TRIM5

A

retrovirus restriction factor - uncoats viruses by binding to capsid proteins

26
Q

what factor inactivates retroviruses by binding to capsid proteins and uncoating

A

TRIM5

27
Q

what is RSV

A

Rous sarcoma Virus - a transforming virus that cn be generated when a cellular protooncogene is captured by insertion into the viral genome during viral replication

28
Q

how can transforming viruses be generated

A

when a cellular protooncogene is captured by insertion into the viral genome during viral replication

29
Q

name a transforming virus

A

Rous Sarcoma Virus -RSV

30
Q

what did Peyton Rous do

A

isolated RSV rous sarcoma virus from a chicken fibrosarcoma

31
Q

what type of viruses are most oncogene containing viruses

A

retroviruses

32
Q

what are viruses related to RSV called

A

ALVs - dont contain oncogenes

33
Q

what is src

A

protein tyrosine kinase -causes ALVs to not be oncogenes

34
Q

besides encoding src (protein tyrosine kinase) how else can retroviruses transform cells

A

by altering the expression of cellular oncogenes eg. cellular (c) myc oncogene

35
Q

give an example of a DNA virus that can cause cell transformation

A

papillomavirus

36
Q

what happens if chromosome of papillomavirus remains in an episome - away from host chromosome

A

get benign growth or wart - not uncontrollable

37
Q

what happens if theres accidental integration of papillomavirus virus DNa into host chromosome

A

lead to malignant uncontrollable tumour and cause unrestricted production of viral protein and interfere with p53

38
Q

name a protooncogene

A

p53

HELENP CBG VIROLOGY AND IMMUNITY (8 decks)

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