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MB 461 Final > Influenza A Virus > Flashcards

Influenza A Virus Flashcards

1
Q

Family

A

Orthomyxoviridae

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2
Q

Genus

A

Influenzavirus A

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3
Q

HA spike

A
  • hemagluttinin
  • binds to sialic acid
  • glues together red blood cells
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4
Q

NA spike

A
  • neuraminidase
  • cleaves silica acid from glycoproteins
  • inhibited by Tamiflu
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5
Q

antigenic drift

A
  • mutations in the HA and NA spikes
  • Flu A and Flu B
  • enough mutations can create a new subtype
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6
Q

antigenic shift

A
  • reassortment of segmented genome

- Flu A only

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7
Q

Stages

A 
Attachment
Penetration
Uncoating
Gene Expression
Genome Replication
Preparation for Release
Assembly
Release
Maturation
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8
Q

Attachment

A
  • receptor mediated (sialic acid)

- attachment protein is HA spike

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9
Q

penetration

A
  • clathrin mediated endocytosis
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10
Q

Uncoating

A
  • acidification of the late endosome causes two events to occur in parallel
    1. HA spike undergoes conformational change and viral envelope fuses with endosomal membrane
    2. M1 dissociates from nucleocapsid due to M2 ion channel allowing protons in
  • nucleocapsid (without M1) now free to go into cytoplasm and exported to nucleus since it has NLS exposed
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11
Q

Gene Expression

A
  • transcription of vRNP by viral RdRP without free NP
  • the mature mRNA is 5’ capped (through 5’ cap stealing), 3’ polyadenylated (through transcription of oligoU sequence), and naked
  • differential splicing may occur
  • mRNA is not a complete copy of vRNA - exported to cytoplasm for translation to NP, M1, and NS2
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12
Q

Genome Replication

A
  • only in presence of NP
  • cap independent initiation of RNA synthesis by viral RdRp
  • vRNPs copied to make cRNPs (+cRNA)
  • cRNPs copied to make vRNPs (-vRNA)
  • absence of 5’ cap on cRNA causes RdRp to ignore transcription termination signals so cRNA are full length copies of vRNA
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13
Q

Preparation for Release

A
  • HA0 (immature form of HA), NA, M2 translated in RER and shuttled through Golgi to plasma membrane
  • NA cleaves sialic acid from host and viral glycoproteins to prevent clumping
  • M1 coated nucleocapsids exported from nucleus to plasma membrane
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14
Q

Assembly

A
  • M1 coated vRNPs associate into a 7+1 bundle
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15
Q

Release

A
  • 7+1 bundles bind to spike proteins at the plasma membrane and bud
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16
Q

Maturation

A
  • HA0 cleaved by extracellular matrix serine protease on the plasma membrane before, during or after release

MB 461 Final (7 decks)

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