Chapter 13: Reoviruses and other dsRNA Flashcards

1
Q

Reoviridae

A

Respiratory
Enteric
Orphan (“no” disease association)

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2
Q

Reoviridae Virion

A
  • Spherical (icosahedral symmetry)
  • 60-80 nm in diameter
  • Genome: dsRNA, 10~20 segments, 18~32 kbp
  • Usually naked
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3
Q

Rotavirus

A

“wheel” in Latin

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4
Q

Rotavirus Virion

A

Spherical, wheel like
Icosahedral symmetry
75 nm in diameter
Triple layer particle

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5
Q

Triple Layered Particle

A

Inner layer made of VP2
Middle layer made of VP6, contain “spokes” of the wheel
Outer layer made of VP7 (glycoprotein)

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6
Q

VP1

A

RNA polymerase

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7
Q

VP3

A

capping enzyme

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8
Q

Rotavirus Genome

A

11 dsRNA segments, 22 kbp
(+) strands are all capped
No poly A
12 gene products

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9
Q

Each segment in Rotavirus genome

A

Associated with VP1 and VP3
Has unique sequence for assembly
Has 1 ORF except that RNA 11 has 2 ORFs in different reading frames

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10
Q

Rotavirus Attachment

A

Many details unclear
Cleavage of Spike protein VP4
Spike proteins and capsid glycoprotein interact with cell surface proteins

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11
Q

Cleavage of VP4

A

Into VP8* and VP5* by trypsin

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12
Q

Rotavirus Entry

A
Direct penetration (mediate by hydrophobic VP5*)
or endocytosis
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13
Q

Rotavirus Entry Events

A

Remove outer layer
Early transcription inside double-layered particle
Translation and modification
NSP2 and NSP5 assemble viroplasm
VP1, VP3 bind to (+) RNA, then to VP2 -> form core
(-) RNA synthesis inside core
VP6 attach core -> double layer particle

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14
Q

Viroplasm

A

viral protein accumulating region for viral replication/assembly

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15
Q

Rotavirus Late Events

A

Late transcription inside double-layered particles -> late mRNA not capped
Cell translation machinery changes
NSP4 and VP7 synthesized in rough ER
Virus controls the quantity of each of 12 viral proteins produced
NSP4 binds VP4 and double-layered particles
The complex buds through ER into a vesicle
VP7 cleaved from vesicle membrane -> build outer layer
VP4- form spikes
Virions released via cell lysis

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16
Q

Rotavirus disease

A

leading cause of severe diarrhea among young children

17
Q

Transmission, Infection, Disease

A

fecal-oral route
enterocytes at the tips of villi in small intestine
Gastroenteritis

18
Q

Rotavirus Pathogenesis

A

destroy enterocytes of villi -> malabsorption of water solutes from gut-> diarrhea

19
Q

Rotavirus Syptoms

A

vomiting, profuse watery diarrhea, fever

20
Q

Other Rotavirus disease facts

A
Incubation 2 days
Infectious does 10-100 virions
Death due to dehydration
Treatment is rehydration
Self-limiting
21
Q

Other dsRNA viruses

A

most naked and have icosahedral symmetry

dsRNA is a potent inducer of cell defense mechanisms

22
Q

Cell defense mechanisms

A

Apoptosis
Interferon production
RNA silencing