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MIMM 324 > 16. Parvovirus > Flashcards

16. Parvovirus Flashcards

1
Q

2 general characteristics of parvovirus

A
  1. icosahedral
  2. 18-26nm diameter
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2
Q

3 characteristics of parvovirus genome

A
  1. ssDNA
  2. 4-6kb
  3. linear
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3
Q

2 general types of parvovirus

A
  1. autonomous
  2. requires helper virus
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4
Q

what is an autonomous virus?

A

infects cells that are already dividing

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5
Q

what does it mean for parvoviruses to require a helper virus?

A

requires adenovirus to be able to replicate

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6
Q

example of parvovirus requiring helper virus

A

dependovirus

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7
Q

what does densovirus infect?

A

insects, silkworms

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8
Q

what happens with canine parvovirus?

A

infects puppies and can cause death

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9
Q

what happens with feline panleukopenia?

A

infects cats and affects blood formation and cause death

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10
Q

why do parvoviruses often infect young animals?

A

because they are still growing so their cells are still dividing –> better for parvovirus

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11
Q

what parvovirus infects humans?

A

B19

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12
Q

what type of parvovirus is B19?

A

autonomous

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13
Q

what happens if a pregnant person is infected with B19 for the first time?

A

can cause severe anemia, Hydrops fetalis which can lead to miscarriage

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13
Q

what happens with B19 infection?

A

infects erythroid progenitors, leading to anemia and reduced blood cells in circulation

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14
Q

what disease in children can B19 cause? what symptom does it cause? how is it treated?

A

Erythema Infectiosum aka Fifth Disease

causes rash on cheeks

just wait for it to be resolved

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15
Q

how was B19 discovered?

A

in sera of patient with severe anemia

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16
Q

why does B19 infect erythroid precursor?

A

they still have their nuclei and are rapidly proliferating

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17
Q

what are the main capsid proteins in parvovirus? and their relative amounts

A

VP1: 60 copies, 3 per face
less VP2 and VP3

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18
Q

do parvovirus capsid proteins self-assemble?

A

yes, they self-assemble into VLP

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19
Q

do the positive or negative regions of parvovirus interact with receptors?

A

positive

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20
Q

why does AAV have spiky proteins on the outside?

A

to reduce antibody efficacy in animals

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21
Q

why does densovirus not have spiky proteins on the outside?

A

because densovirus infects insects but insects don’t have antibodies

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22
Q

describe general parvovirus genome structure

A
  1. 2 promoters
  2. encodes non-structural/replicase protein and viral/cap protein
  3. each end has different structures
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23
Q

describe general dependovirus genome structure

A
  1. 3 promoters
  2. encodes non-structural/replicase protein and viral/cap protein
  3. each end has identical structures
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24
Q

describe general B19 genome structure

A
  1. 1 promoter
  2. encodes non-structural/replicase protein, viral/cap protein, and extra protein
  3. each end has identical structures
25
Q

describe general densovirus structure

A
  1. 2 promoters in opposite direction
  2. encodes non-structural/replicase protein and viral/cap protein
  3. each end has identical structures
26
Q

what is the purpose of the dsDNA structures on the ends of ssDNA? how do they form?

A

form via complementary repeats for replication and packaging

27
Q

do all parvoviruses use the same receptor for entry?

A

no

28
Q

what receptor is used by B19 for entry?

A

erythrocyte P antigen –> surface protein on erythrocytes and pre-erythrocytes

29
Q

what receptor is used by CPV/FPV for entry?

A

transferin receptor –> found on most cells for iron transport

30
Q

what receptor is used by AAV for entry?

A

heparin sulphate or EGFR integrins –> diff receptors by diff AAV

31
Q

how does parvovirus enter the cell?

A

endocytosis

32
Q

how is the virus released from the endosome?

A

endosome acidifies, which changes conformation of capsid and releases phospholipase so it can leave endosome

33
Q

how does the virus enter the nucleus?

A

via a nuclear localization signal from the virus

34
Q

function of inverted terminal repeats on the ends of DNA?

A

DNA polymerase can use them as primer for dsDNA

35
Q

does parvovirus use primers?

A

no, it is self-priming

36
Q

describe the 5 steps of DNA replication:

A
  1. DNA pol extends 3’ end from inverted terminal repeat
  2. NS1/rep protein binds original strand and nicks with endonuclease activity
  3. NS1/rep protein unwinds the hairpin and the 3’ OH at the nick site can be extended by DNA pol
  4. hairpin refolds and DNA pol continues extending 3’ end
  5. 1 ssDNA and 1 dsDNA product are produced
37
Q

what is the name for parvovirus replication?

A

Rolling Hairpin Replication

38
Q

describe the promoter and coding/non-coding regions of MVM genome and how this corresponds to early/late genes

A

p4 promoter for early genes (NS1/2) in coding region at beginning of transcript (end of transcript is non-coding in early phase)

then, p38 promoter for late genes (VP1/VP2) in coding region at end of transcript

39
Q

describe the promoter and coding/non-coding regions of AAV genome and how this corresponds to early/late genes

A

p5 and p19 make diff truncated versions of replicase in coding region at beginning of transcript (end of transcript is non-coding in early phase)

p40 promoter for late genes (VP1/2/3) in coding region at end of transcript

40
Q

parvovirus genomes has binding sites for ______ ________

A

parvovirus genomes has binding sites for transcription factors

41
Q

what is an important transcription factor that binds MVM and other autonomous parvovirus genome?

A

E2F

42
Q

why is it important that autonomous parvovirus genomes bind E2F?

A

Allows the virus to sense that Rb is phosphorylated so the cell is actively replicating and making S phase genes

43
Q

what binds both the early and late transcripts for autonomous parvovirus?
why?

A

NS1 –> binds at promoter region to increase transcription

44
Q

how does adenovirus help AAV?

A

E1A protein turns on early and late promoter

45
Q

besides E1A, what protein binds AAV transcript? early or late?

A

NS1/rep78 binds early transcript to make NS1

46
Q

what allows for AAV early transcription?

A

E1A induced S phase activation

47
Q

what happens if a dependovirus infects a cell that is not actively replicating / no adenovirus is present? (3 steps)

A
  1. ssDNA is turned into dsDNA
  2. Rep78 allows dsDNA to integrate into host chromosome
  3. virus sits latent
48
Q

what happens if an adenovirus infects a cell with latent parvovirus? (3 steps)

A
  1. adenovirus mediates S phase
  2. Rep78 allows parvovirus genome to be released
  3. parvovirus co-replicates with adenovirus
49
Q

besides replication, how are the dsDNA structures used?

A

recognized by capsid proteins for assembly

50
Q

if the genome has inverted repeats on the ends, is the (+) or (-) sense strand added?

A

either, bc both ends have the same structure

51
Q

if the genome has unique structures on each end, is the (+) or (-) sense strand added?

A

it depends, but a specific virus will only use one or the other

52
Q

4 functions of NS1/Rep78

A
  1. binding viral DNA to induce late gene expression
  2. ATPase dependent helicase to unwind viral DNA
  3. sequence specific endonuclease to begin replication
  4. keeps cells in S phase
53
Q

what type of therapy is AAV used for?

A

AAV is used as a vector for gene therapy

54
Q

5 advantages of gene therapy vector

A
  1. does not cause disease in humans
  2. different AAV serotypes use diff receptors so can target specific tissue
  3. low toxicity
  4. stable expression (observed up to 1 year)
  5. can genetically manipulate bc small genome
55
Q

3 steps of producing AAV as gene therapy vector

A
  1. remove rep and cap from genome and add transgene with strong promoter
  2. transfect in E1-expressing cell with AAV helper and AD helper
  3. produces recombinant virus particles that cannot replicate and only deliver genes of interest
56
Q

what is the AAV helper?

A

contains rep and cap

57
Q

what is the AD helper?

A

contains E2A, E4, VARNA

58
Q

why do you need AAV and AD helpers?

A

bc the virus with transgene is dead so must have genes that can allow virus particles to be made

59
Q

AAV vectors have different _____ to target different areas

A

AAV vectors have different capsids to target different areas of body

60
Q

7 diseases that AAV can be used for:

A
  1. PKU
  2. Hemophilia A
  3. Hemophilia B
  4. Duchenne’s Muscular Dystrophy
  5. Aromatic amino acid decarboxylase (AADC) deficiency
  6. mutation associated retinal dystrophy
  7. spinal muscular atrophy
61
Q

how much does 1 dose of Zolgensma cost for spinal muscular atrophy?

A

$2.8 million

MIMM 324 (37 decks)

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