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MIMM 324 > 13. Poxvirus > Flashcards

13. Poxvirus Flashcards

1
Q

are poxviruses enveloped or naked?

A

enveloped

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2
Q

what shape is the virus?

A

brick

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3
Q

is poxvirus small or large?

A

very big –> 200x250x300nm

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4
Q

3 characteristics of poxvirus genome

A
  1. dsDNA
  2. 130-300kb
  3. linear
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5
Q

what are the 2 main subfamilies of poxvirus?

A
  1. Chordopoxvirinae
  2. Entomopoxvirinae
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6
Q

what are the 2 main genera of Chordopoxvirinae that we will look at in this lecture?

A
  1. Orthopoxviruses
  2. Molluscipoxviruses
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7
Q

what type of diseases do poxviruses cause?

A

skin diseases –> can become systemic in organs

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8
Q

when was poxvirus eradicated?

A

1980

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9
Q

describe the clinical progression of smallpox (4 steps)

A
  1. infection by aerosol droplet
  2. virus incubates for some days
  3. leads to fever and rash all over body
  4. 30% ppl will die
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10
Q

what did Edward Jenner do?

A
  • noticed that milkmaids never got smallpox bc exposed to cowpox
  • took pus from cowpox lesions and gave to a young boy
  • a month later, gave him pus from smallpox lesions and he never got the disease
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11
Q

what is variolazation?

A

give person the pus of smallpox –> develop smallpox but only have 1% chance of dying

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12
Q

what is vaccinia?

A

the strain of poxvirus in the vaccine –> but its not cowpox as Jenner originally used, we don’t know where it came from

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13
Q

describe the smallpox vaccine

A
  1. very stable so dried down in vial, then reconstituted upon use
  2. use bifurcated needle with a little bit of virus
  3. lesion will develop but goes away and patient is immune
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14
Q

what was the problem with the vaccinia in smallpox vaccine?

A

it was a live, replicating virus so in some cases it can spread and kill ppl –> esp if immunocompromised

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15
Q

is smallpox or monkeypox more pathogenic?

A

smallpox

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16
Q

where is monkeypox most common in the world?

A

Africa

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17
Q

how do you protect against monkeypox?

A

smallpox vaccine works for monkeypox

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18
Q

what are the 2 types of the virus? which is worse?

A
  1. West African
  2. Congo Basin –> more pathogenic and fatal
19
Q

how is Monkeypox spread?

A

zoonotic infection from rodents

20
Q

describe the imvamune vaccine

A

passaged thru chicken eggs so it can’t replicate in human cells –> much safer

this one is actually injected

21
Q

which virus causes molluscipoxvirus?

A

molluscum contagiosum

22
Q

is molluscum contagiosum common?

A

yes –> accounts for 1% of all diagnosed skin conditions

23
Q

how does molluscum contagiosum spread?

A

by physical contact, mainly in moist areas, back of legs

24
Q

is molluscum contagiosum severe?

A

no, it is self-resolving and doesn’t get systemic

25
Q

where in the cell do ALL poxviruses replicate?

A

in cytoplasm –> nucleus remains intact

26
Q

what is the shape of the core of the virus?

A

barbell

27
Q

what contributes to most of the weight of the virus?

A

proteins!! holds many proteins inside

28
Q

what are 4 special features of the poxvirus genome?

A
  1. terminal loops
  2. tandem repeats
  3. DNA is A-T rich
  4. has many bulges of 1 base that doesn’t match
29
Q

describe the terminal loops

A

the ends of the DNA are covalently closed so there are no 5’/3’ ends

30
Q

what are tandem repeats?

A

repeats of the same sequence on the end of the DNA

31
Q

why does the DNA have a loose double-strand?

A

A-T rich (weaker) and mismatched bases

32
Q

how are early/intermediate/late genes dispersed throughout the genome?

A

random locations within genome –> expressed based on promoters

33
Q

what is the first step of poxvirus lifecycle?

A

attachment

34
Q

how does vaccinia attach to its target cell?

A

vaccinia can infect any cell, not very specific –> likely by glycosaminoglycans

35
Q

what is packaged in the virus?

A

ALL enzymes and factors required for early gene expression

36
Q

why does the virus package all enzymes and factors required for early gene expression?

A

because poxvirus only replicates in cytoplasm, doesn’t go into cell nucleus

37
Q

describe the genetic cascade (4 steps)

A
  1. all enzymes/factors for early gene expression packed in virus
  2. early mRNAs encode enzymes for viral DNA synthesis and factors for expression of intermediate genes
  3. intermediate mRNAs encode enzymes for expression of late genes
  4. late transcription factors activate the enzymes and factors for early gene expression to be packaged into new virus particles
38
Q

how does genome replication begin?

A

early enzyme makes a nick in the terminal loop to allow exposed 3’ OH to be accessible by polymerase

39
Q

describe the “self” priming mechanism of poxvirus DNA replication

A

uses its terminal repeats to replicate

40
Q

what is resolvase?

A

encoded by virus to snip the end of the 2 completed genomes at the terminal loop once replication is complete

41
Q

describe the steps of virus exit

A
  1. crescent-shaped lipid membrane
  2. Immature Virion forms full circle
  3. machinery brings in genome to form Nucleoid
  4. forms Mature Virion
  5. buds off golgi to get a 2nd membrane and form Wrapped Virion
  6. fully mature virus is released
42
Q

in addition to intermediate stage enzymes and factors, what do the early genes produce?

A

secretes factors called VIROCEPTORS to attenuate the immune system

43
Q

how do viroceptors attenuate the immune system

A

act as homologues of cytokine receptors or bind different immune factors to block their function

MIMM 324 (37 decks)

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