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Virology > 5: Multiplication > Flashcards

5: Multiplication Flashcards

1
Q

Multiplication cycle of viruses?

short

A
  • Adsorption
  • Penetration
  • Decapsidation
  • Eclipse
  • Maturation
  • Release
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2
Q

What happens during adsorption?

A

attachement to the host cell

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3
Q

What happens during penetration?

A

entry into the host cell

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4
Q

What happens during decapsidation?

A

nucleic acid release

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5
Q

What happens during eclipse?

A
  • expression and copy of the viral genetic information
  • transcription, translation and NA replication
  • different strategies according to the type of NA – > the Baltimore-system
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6
Q

What happens during maturation?

A
  • assembly of progeny virions
  • Polipeptide –> protein
  • Glycosylation, dimer formation, antigen development at the ER, Golgi
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7
Q

What happens during release?

A

evacuation from the host cell

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8
Q

What are the different types of receptors in Adsorption?

A
  • cell surface receptor

- virus surface antireceptor

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9
Q

What is characteristic for the Cell surface receptor of Adsorption?

A
  • 10^4-5/cell (stable)
  • usually already expressed in the embryo
  • necessary for cellular functions
    (ie. CD4 - HIV, acetylcholine receptor - rabies virus)
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10
Q

What is characteristic for the Virus surface antireceptor of Adsorption?

A
  • more variable
  • viruses adapt the cellular surface receptors dring their evolution
  • related viruses usually target the same cell surface receptor
  • sometimes non-related viruses have the same receptor
    (ie. CAR = Coxackie-adeno receptor)
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11
Q

how is the stability of Virus surface antireceptor determined?

A

determined by the tissue or species receptor protein

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12
Q

What happens if the Virus surface antireceptor is negatively charged?

A
  • repulsion

- collision by chance

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13
Q

What happens if the Virus surface antireceptor has reversible connection?

A

Cations neutralize the electrostatic power

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14
Q

What happens if the Virus surface antireceptor has irreversible connection?

A

Chemical bonds between the proteins

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15
Q

Penetration can be?

A
  • energy dependent

- energy consuming

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16
Q

What are the 2 forms of Penetration?

A
  • General

- Alternative

17
Q

What are the General forms of penetration?

A
  • Translocation
  • endocytosis
  • membrane fusion
18
Q

What are the Alternative forms of penetration?

A
  • injection
  • sexfimbria
  • passive
19
Q

What is translocation?

penetration form

A
  • ie picornavirus

- “trapdoor” mechanism, amorphous RNA-protein complex

20
Q

What is endocytosis?

penetration form

A
  • mostly non-enveloped viruses + herpes, pox.

- cell nutrition endosome –> phagolysosome –> decapsidation

21
Q

What is membrane fusion?

penetration form

A
  • only enveloped viruses
  • viral fusion (F) protein induces
  • the viral envelope merges into the cytoplasmic membrane of the host cell –> only the nucleocapsid gets into the cytosol
22
Q

What is injection?

penetration form

A
  • tailed bacteriophage

- lysozyme enzyme + contractile proteins

23
Q

What is sexfimbria?

penetration form

A
  • ribophages

- lack of cellular wall –> “bacterial sexual disease”

24
Q

What is passive?

penetration form

A
  • plant viruses

- cellular wall injuries, arthropod bites

25
Q

Describe decapsidation

A
  • uncoating
  • release of the NA from the capsid
  • dangerous for the virus, but necessary for the transcription
26
Q

What are the strategies of Decapsidation?

A
  • use of cellular proteases (in lysosomes)
  • viral uncoating proteins (ie. poxviruses)
  • partial decapsidation
  • simulatneous penetration and decapsidation
27
Q

What is Partial decapsidation?

A
  • hiding the NA until the early virus protein production

- ie. DNA viruses in the nucleus, Reo-, orthomyxo-, paramyxoviruses.

28
Q

How does simultaneous penetration and decapsidation happen?

A

by translocation and/or injection

29
Q

Where does Virus assembly occur?

A

Usually at the site of replication –> protection

  • RNA viruses + Pox, Asfarviridae –> cytoplasm
  • other DNA viruses –> nucleus
30
Q

Methods of virus assembly:

A
  • the nucleic acid enters into the capsid –> Icosahedral

- The capsomers surround the nucleic acid –> helical

31
Q

What helps regulate the virus assembly?

A

Scaffolding proteins

- envelope and matrix proteins are acquired from cellular membranes.

32
Q

Types of Virus release

A

Passive/active way

33
Q

Virus release in Non-enveloped viruses:

A
  • -> cytolysis
  • Rapid (picornav.)
  • Slow (Parvov.)
  • Apoptosis (adenoviridae)
34
Q

Virus release in Enveloped viruses:

A

Budding

  • Rapid (togav., paramyxov., rhabdov.)
  • Slow (arenav., retrov.)
35
Q

Budding sites of enveloped virus release:

A

Budding site is virus-specific.

  • Herpesv: nuclear membrane
  • Flaviv: ER
  • Coronav., Bunyav: Golgi
  • Asfarv., Togav., Orthomyxov., Paramyxov., Rhabdov: Cytoplasmic membrane
36
Q

Virus release in Cell-associated viruses (Gammaherpesvirinae):

A

release at cell death or injuries

37
Q

Virus release in Cell fusion (syncytium formation):

A
  • -> membrane tunnels

- safe way of spreading (herpesv., paramyxov.)

38
Q

Alternative forms of virus release:

A
  • lysosome disintegrations (herpesviridae)
  • T bacteriophages: lysyme enzyme digests the cellular wall
  • plant cells are firmly connected to each other:
  • -> virus spread from cell to cell
  • -> mosaic pattern

Virology (25 decks)

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