13. Poxvirus

Question 1

are poxviruses enveloped or naked?

Answer 1

enveloped

Question 2

what shape is the virus?

Answer 2

brick

Question 3

is poxvirus small or large?

Answer 3

very big –> 200x250x300nm

Question 4

3 characteristics of poxvirus genome

Answer 4

1. dsDNA
2. 130-300kb
3. linear

Question 5

what are the 2 main subfamilies of poxvirus?

Answer 5

1. Chordopoxvirinae
2. Entomopoxvirinae

Question 6

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

Answer 6

1. Orthopoxviruses
2. Molluscipoxviruses

Question 7

what type of diseases do poxviruses cause?

Answer 7

skin diseases –> can become systemic in organs

Question 8

when was poxvirus eradicated?

Answer 8

1980

Question 9

describe the clinical progression of smallpox (4 steps)

Answer 9

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

Question 10

what did Edward Jenner do?

Answer 10

• 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

Question 11

what is variolazation?

Answer 11

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

Question 12

what is vaccinia?

Answer 12

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

Question 13

describe the smallpox vaccine

Answer 13

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

Question 14

what was the problem with the vaccinia in smallpox vaccine?

Answer 14

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

Question 15

is smallpox or monkeypox more pathogenic?

Answer 15

smallpox

Question 16

where is monkeypox most common in the world?

Answer 16

Africa

Question 17

how do you protect against monkeypox?

Answer 17

smallpox vaccine works for monkeypox

Question 18

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

Answer 18

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

Question 19

how is Monkeypox spread?

Answer 19

zoonotic infection from rodents

Question 20

describe the imvamune vaccine

Answer 20

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

this one is actually injected

Question 21

which virus causes molluscipoxvirus?

Answer 21

molluscum contagiosum

Question 22

is molluscum contagiosum common?

Answer 22

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

Question 23

how does molluscum contagiosum spread?

Answer 23

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

Question 24

is molluscum contagiosum severe?

Answer 24

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

Question 25

where in the cell do ALL poxviruses replicate?

Answer 25

in cytoplasm --> nucleus remains intact

Question 26

what is the shape of the core of the virus?

Answer 26

barbell

Question 27

what contributes to most of the weight of the virus?

Answer 27

proteins!! holds many proteins inside

Question 28

what are 4 special features of the poxvirus genome?

Answer 28

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

Question 29

describe the terminal loops

Answer 29

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

Question 30

what are tandem repeats?

Answer 30

repeats of the same sequence on the end of the DNA

Question 31

why does the DNA have a loose double-strand?

Answer 31

A-T rich (weaker) and mismatched bases

Question 32

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

Answer 32

random locations within genome --> expressed based on promoters

Question 33

what is the first step of poxvirus lifecycle?

Answer 33

attachment

Question 34

how does vaccinia attach to its target cell?

Answer 34

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

Question 35

what is packaged in the virus?

Answer 35

ALL enzymes and factors required for early gene expression

Question 36

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

Answer 36

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

Question 37

describe the genetic cascade (4 steps)

Answer 37

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

Question 38

how does genome replication begin?

Answer 38

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

Question 39

describe the "self" priming mechanism of poxvirus DNA replication

Answer 39

uses its terminal repeats to replicate

Question 40

what is resolvase?

Answer 40

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

Question 41

describe the steps of virus exit

Answer 41

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

Question 42

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

Answer 42

secretes factors called VIROCEPTORS to attenuate the immune system

Question 43

how do viroceptors attenuate the immune system

Answer 43

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