Poxvirus

Question 1

types of infection virion present

Answer 1

i) intracellular mature virions
ii) extracellular enveloped virions

Question 2

Difference between each infection virion

Answer 2

i) membranes present
- 2 in total for intracellular
- 3 in total for extracellular
ii) stability: intracellular more stbale than extracellular outside of host
iii) entry
- IMV directly fuse with plasma membrane (at cell surface or after endocytosis)
- EEV: outer membrane ruptures, then use IMV membrane to fuse with plasma membrane

Question 3

function for intracellular mature virions

Answer 3

spread from 1 host to another

Question 4

function of extracellular enveloped virion

Answer 4

for cell to cell spread within host

Question 5

features of genome of poxvirus

Answer 5

i) ends have inverted terminal repeats
ii) 2 dna strands connected by hairpin loop

Question 6

How does IMV enter cells?

Answer 6

outer membrane fuse to plasma membrane
–> cell surface or in endosomal vesicle

Question 7

how does EEV enter cells?

Answer 7

i) outer membrane ruptures after touching cell surface
ii) IMV fuse with plasma membrane

Question 8

Can all cells be used for viral replication of poxvirus?

Answer 8

no, even though virus can enter any cell

Question 9

What happens after poxvirus enters the cells?

Answer 9

i) uncoating of nucleoprotein from core
ii) core transported with help of microtubules to place close to ER
–> DNA release from core

Question 10

Types of genes in poxvirus gene expression

Answer 10

early, intermediate, late

Question 11

across all DNA viruses in Dr. Frappier section, what is special abt poxvirus transcription?

Answer 11

lack splicing

Question 12

what helps with early gene expression in poxvirus?

Answer 12

RAP94, VETF (vaccinia early transcription factor), RNA polymerase (belong to pox)

Question 13

What proteins do early gene encode for?

Answer 13

involved in intermediate gene expression, host interaction, DNA replication

Question 14

When are intermediate genes expressed?

Answer 14

after DNA replication

Question 15

Differences between gene expression of each classes in poxvirus

Answer 15

i) timing
- early: 1st one
- intermediate: after DNA replication
- late: after intermediate
ii) promoter: different for each class
iii) protein needed to start transcription
- early: RAP94, VETF
- intermediate: VITF (from early)
- Late: VLTF (from intermediate)

Question 16

similarities between intermediate and late mRNA

Answer 16

i) 5’ polyA head
ii) heterogenous 3’ ends (transcription terminate at diff. spots)

Question 17

Where does DNA replication of poxvirus occur?

Answer 17

viral factories

Question 18

What acts as primer for vaccinia DNA replication?

Answer 18

3’OH of nick

Question 19

Describe steps for DNA replication of poxvirus

Answer 19

i) nick made near end of genome
ii) 3’OH of nick as primer, replication goes continuously by strand displacement
iii) tail to tail dimer made, later form concatemers
iv) resolved into individual genomes in later stages

Question 20

mechanism of DNA replication for poxvirus

Answer 20

strand displacement

Question 21

What processes happen in viral factory?

Answer 21

DNA replication, transcription, translation

Question 22

where does virion assembly occur?

Answer 22

cytoplasm

Question 23

virion assembly for IMV

Answer 23

i) immature virions assembled
–> get 2nd membrane from golgi
ii) IVs then mature to brick shaped IMV
iii) IMV released from cells if cell lyses

Question 24

virion assembly for EEV

Answer 24

first two steps same
iii) IMV acquire two more membranes form golgi
–> form intracellular enveloped virions (IEV)
iv) IEV transported to plasma membrane
–> release EEV from cells

Question 25

what are EEVs that remain associated to cell surface called?

Answer 25

CEV (cell associated enveloped virion)

Question 26

what are CEV important for?

Answer 26

cell to cell transmissionW

Question 27

What helps with infection of CEV?

Answer 27

actin

Question 28

how does actin help CEV infect neigbouring cells?

Answer 28

i) induce actin tail formation near where CEV attaches
ii) actin tails push CEV from cell surface to nearby ones

Question 29

Ways to combat host immune response for poxvirus

Answer 29

i) immediate inhibition of host DNA synthesis
ii) immediate inhibition of host protein synthesis
iii) inhibits apoptosis
iv) inhibits anti-viral responses

Question 30

How does poxvirus inhibit host protein synthesis?

Answer 30

i) degrade host mRNA
ii) inhibit host mRNA synthesis and processing

Question 31

How does poxvirus inhibit anti-viral response?

Answer 31

i) inhibits PKR, allow viral translation to continue
ii) inhibit cytokine and complement based signalling pathways by viral proteins

Question 32

How does monkeypox spread?

Answer 32

men who have sex with men

Question 33

what does myxoma virus infect?

Answer 33

European rabbits only, south american rabbits not affected

Question 34

Myxoma virus and cancer?

Answer 34

recently shown to infect and kill several types of human tumor cells