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Micro/Immuno Part 2 > RNA Virus 1 > Flashcards

RNA Virus 1 Flashcards

1
Q

Picorna

A

-colds and polio

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2
Q

flavi

A

hep C and dengue

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3
Q

retro

A

HIV

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4
Q

corona

A

MERS-middle east resp syndrome

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5
Q

filo

A

ebola

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6
Q

rhabdo

A

rabies

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7
Q

orthomyxo

A

flu

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8
Q

paramyxo

A

croup

measles

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9
Q

relevance of RNA viruses

A

-huge medical problem-flu, colds, diarrhea, hep C, AIDS
-high mutation rates:
-resistance to antivirals
-barriers to vaccines
-reassortment of genome segments
-pandemics
“scariest new bugs”-Quammen

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10
Q

common features of RNA viruses

A
  • RNA is genetic material and template for protein synthesis
  • the dual purpose of replication is to copy the genome and make mRNA
  • diverse strategies have evolved to accomplish these dual goals
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11
Q

double stranded RNA

A

-uses RDRP to make + sense mRNA for proteins

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12
Q

ss RNA +

A
  • can be used for protein synthesis
  • must use RDRP to make - strand to make copies for more protein synthesis, and RDRP changes - back to + before reading it
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13
Q

ssRNA -

A

-can be replicated or transcribed to + by RDRP

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14
Q

+strand

A

-sense strand, coding= mRNA

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15
Q
  • strand
A
  • antisense strand

- template for mRNA

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16
Q

how to make RNA from RNA?

A
  • RDRP

- allows viruses to cope their RNA genomes and to synthesize mRNA from RNA templates

17
Q

RDRP

A
  • cells do not have the enzymes to transcribe RNA from RNA
  • therefore all rNA viruses encode and RNA pol to copy their RNA genome and make mRNA
  • RDRP is highly efficient-poliovirus makes 50K copies in 8 hours!
18
Q

where does RDRP do its job?

A
  • cytoplasm-except flu- anchored to something
  • RNA, RDRP, nucleoproteins, and accessory proteins don’t float freely in cytoplasm
  • replication often occurs on cell membranes (endo, lyso, ER vesicles)
  • this concentrates all the components and increases efficiency
19
Q

fidelity of RDRP is low

A
  • doesn’t proofread, works as an octomer
  • error rates of 1 in 10^3-4
  • all RNA virus stocks are mixtures of wild type and mutant forms
20
Q

rapid evolution by recombination

A
  • exchanging larger sections produces new genomes
  • hybrid viruses may have new features (antigens, virulence)
  • high freq event-up to 20% of poliovirus genomes are recombinant after 1 growth cycle
21
Q

reassortment of genome segments

A
  • segmented RNA viruses-Reo, Retro, Bunya, Arena, Orthomyxo
  • segments can mix if cell is infected with multiple strains
  • new variant can be highly virulent-fluuuuu
22
Q

consequences of RNA virus genetic diversity

A
  • mutants arise frequently
  • new variants may cause new diseases
  • drugs and vaccines lose effectiveness
  • viruses are not pure populations-quasispecies
23
Q

polio!

A
  • +ssRNA linear mRNA molecule
  • infects GI epithelial cells, may spread to muscles and neurons
  • vaccination with live or killed virus induces protective antibodies
  • WHO Global eradication program underway
  • annual cases-296 as of oct 2, 2013
24
Q

polio disease

A
  • fecal oral
  • persists in water
  • humans only host
  • 95% asymptomatic acute GI infection
  • 5% mile disseminated disease
  • 1% paralytic infection of motor neurons
25
Q

polio cycle

A
  • enters cell via endocytosis or just docks- CD155
  • ejects genome because capsid is pulled open by interaction with receptors (become hydrophobic)
  • mRNA immediately translated to protein-then cleaved by self proteases
  • RDRP replicates genome into - strand and copies it many times
  • RDRP also transcribes - strand back to + strand so it can be translated
  • when there is enough mRNA, RDRP just makes RNA genome to be packaged-when there are enough capsids around
26
Q

issues with + RNA

A
  • collisions occur b/n RDRP and ribosomes, not big problem
  • translation first when RDRP is scarce
    • RNA synthesis occurs later when RDRP is abundant-then must be changed back into plus to be packaged
27
Q

association of RDRP with virions

A
  • all RNA viruses encode RDRP (retro-RT)
  • dsRNA and - RNA must package RDRP into virion- can’t be translated first
  • +RNA may or may not package
  • if RDRP not present, must translate first
28
Q

polio clinical features

A
  • motor neuron involvement
  • serology and culture
  • control symptoms, breathing support
  • vaccine, sanitation, peace

Micro/Immuno Part 2 (17 decks)

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