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Molecular Microbiology > Poxviruses > Flashcards

Poxviruses Flashcards

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Biology 101 flashcards
1
Q

Poxviruses

A

2 subfamilies -
chordopoviruses, vertebrates
entomopoxviruses, insects

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2
Q

Orthopox genus

A

Notably Variola, cowpox, vaccinia and monkeypox
Morphollogically indistinguishable
Immunologically realted

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3
Q

Smallpox

A

Variola virus - major (20% fatality) and minor (1-2%)
No animal reservoir
300-500 million deaths in 20th century

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4
Q

Symptoms of smallpox

A

Fever, vomiting, skin rash, mouth ulcers

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5
Q

Variola virus

A

Large + brick shaped w envelope
1 linear dsDNA genome + hairpin loop at each end
186kbp
Replication occurs in cytoplasm
DNA dependent RNAP

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6
Q

Scarification

A

Early attempt at vaccine by Edward Jenner
Scratch scabs into arms

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7
Q

Vaccinia virus

A

Similar to variola
2 types of virion - Mature and Extracellular Enveloped
260 functional proteins

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8
Q

Mature virion (IMV)

A

Single outer membrane
only released upon cell lysis
responsible for person-person transmission
good at surviving outside of body

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9
Q

Extracellular enveloped virion (EEV)

A

Membrane dissolution
Fusion with membrane like IMV
Ligand dependent
Endosomal entry with low pH

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10
Q

Poxvirus genome

A

Variable - Conserved - Variable
Variable: Non-essential functions -> host range, virulence and immunomodulation
Conserved: Essential functions -> trancription, DNA replication, structural proteins, enzymes
dsDNA 135-300kbp
Tightly packaged

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11
Q

DNA Replication poxviruses

A

Occurs in cytoplasm
Starts with nick at ends of genome, self priming
Continuous ORF
Highly conserved proteins e.g. DNAP, NTP, DNA glycolase
Semiconservative replication

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12
Q

Poxvirus transcription

A

Transcription enzymes packaged into virion core - transcribe early mRNAs
Short promoters not recognised by host RNAP2
Cascade model

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13
Q

Poxvirus transcription cascade model

A

Expression of each gene class dependent on prior expression of proteins of previous class
Proteins produced in waves

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14
Q

How does the poxvirus cascade model work?

A

3 stages: early, intermediate and late gene expression

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15
Q

Early gene expression poxvirus

A

Driven by transcription factors already present in virion
They come into the cell with the virion particle
Package the early transcription system within the infectious virus particle and sequentially synthesizing virus-encoded intermediate and late transcription factors

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16
Q

Intermediate gene expression

A

Express DNA replication enzymes
Late gene expression transcription factors

17
Q

Late gene expression

A

Structural proteins required to assembly poxvirus particle
Expressed for while then early genes expressed for next particle

18
Q

Vaccinia replication cycle

A

Microtubule network usd to move around the cell
IMV released by lysis - small proportion to golgi
golgi wraps in double membrane = IEV 3 membranes
Buds out, loses one of membrane and forms CEV

19
Q

CEV

A

Cell associated enveloped virus
Same as EEV but attached to outside of cell
Responsible for cell to cell spread

20
Q

Vaccinia virus spread

A

Cell to cell (CEV) and long range spread (EEV)

21
Q

Plaque assay for vaccinia

A

Lawn of bacteria, plaque = region on plate infected by virus
Important for determining how particles can be fatal
Titrate 10 fold dilution until you see individual plaques on plate
1 plaque = 1 viral particle, can determine how many per ml
Too fast for vaccinia plaque assay

22
Q

Model of vaccinia spread in vivo

A

Virus promotes actin tail formation
actin tail propels CEV onto adjacent cell
Cell marked with A36/33 to indicate it has been infected - prevent waste of resources
Bouncing continues to next uninfected cell - VERY FAST

23
Q

Bioterrorism with smallpox

A

Possibly unregistered stocks globally
Reduced immunity in public due to vaccine campaign being stopped
Antiviral treatments such as tecovirimat used to contain and normal pandemic procedures

24
Q

Tecovirimat

A

Impairs VP37 protein required for envelope development
Virus can’t mature
Inhibits virus induced cytopathic effects
Treatment for symptomatic smallpox

25
Q

Monkeypox

A

Usually mild illness
Less fatal than smallpox
attenuated vaccinia ankara vaccine
human-human transmission through bodily fluids

Molecular Microbiology (19 decks)

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