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Veterinary Virology DMP851 > Virus Replication > Flashcards

Virus Replication Flashcards

1
Q

Viral Replication:

Steps

A
  1. Receptor mediated
  2. Attachment and Entry
  3. Uncoating
  4. Genome replications
  5. RNA and protein synthesis
  6. Assembly of nucleocapsid and maturation
  7. Release form the cell
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2
Q

Susceptible

A

has a receptor for a virus

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3
Q

Resistant

A

does not have the receptor for a virus

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4
Q

Permissive

A

Can replicate the virus

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5
Q

Susceptible and permissive

A

The virus can enter the cell and replicate

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6
Q

Viral Replication:

  1. Steps for Attachment and Entry
A
  • Virions have to diffuse across the plasma membrane and then release the genome
  • Steps for attachment and entry:
    • Adhere to the cell surface
      • not specific, happens by chance since they cannot move
    • Attache to a recepto
      • these receptors are not made for the virus they are receptors for proteins that the cell normally needs
      • Genome is then transferred into the cell
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7
Q

Viral Replication:

  1. Entry:
A

Once the virus enters it is transported to the correct location

CME = Clathrin-mediated endocytosis

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8
Q

Viral Replication:

  1. Uncoating
A

Acidic condition in the endosome triggers changes in viral structural proteins resulting in uncoating and release of the viral genome

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9
Q

Viral Replication:

make mRNA

A

Transcription

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10
Q

Viral Replication:

  1. Transcription of Viral Genes

DNA genome Viruses

A

Host or virus DNA-dependent RNA polymerase generates viral mRNA

mRNA is translated into viral proteins using cellular machinery

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11
Q

Viral Replication:

  1. Transcription of viral genes

RNA genome Viruses

A

Require a viral-encoded RNA-dependent RNA polymerase (RdRp) to make mRNA

There is no cellular RdRp to copy RNA form a viral RNA template.

Virus must possess or synthesize RdRp

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12
Q

Viral Replication:

  1. Translation of mRNA to make viral proteins
A
  • Translate the mRNA into protiens
  • Compare to cell mRNA
    • 5’ cap UTR AUG ORF stop UTR AAAAAA 3’
  • Ribosomes are needed for translation
  • tRNA also needed to add the correct amino acids
  • Translation also needs
    • initiation
    • Elongation
    • Termination proteins
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13
Q

Viral Replication:

  1. Virus Replication:

Viral Genome synthesis:

DNA viruses

A

most replicate in the nucleus

except poxvirus and mimivirus

Most us the host DNA-dependent DNA polymerase

Except poxvirus and herpesvirus

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14
Q

Viral Replication:

  1. virus replication

Viral genome synthesis

RNA viruses

A

most use viral encoded RNA-dependent RNA polymerase

except retroviruses that use reverse transcriptase

Quasispecies - not two viral genomes are identical

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15
Q

Viral Replication:

  1. Translation of Viral Proteins
A
  • All viruses use cell machinery for making proteins
  • Viral protiens:
    • often named based on timing of synthesis
  • Early Translation Products:
    • mostly nonstructural protiens
  • Late Translation Products:
    • Structural proteins
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16
Q

Viral Replication:

  1. Assembly of nucleocapsids and Virus maturation
A
  • Self assembly of the capsid:
    • many viral proteins assemble on their own
      • HIV poliovirus, Influenza HA
    • Empty shells can be the basis for vaccines
  • Assisted Assembly:
    • some need scaffold and chaperones from the cell to form the viral structure
  • All viruses have to:
    • form the protein chell from one or many viral proteins
    • Assemble the protein shell
    • Release the virion from the host cell
  • Some viruses have to:
    • Acquire an envelope
    • Go through virion maturation
17
Q

Viral Replication:

  1. Budding or Release from the cell

Envelope

A

Normally happens after the assembly of the nucleocapsid then buds

There are four strategies for budding

18
Q

Viral Replicaiton:

  1. Budding or Release from the cell

Budding:

A

Depending on the virus, budding can occur form any membrane compartment

Can make a double membrane on the virus

19
Q

Viral Replication:

  1. Budding or Release from the cell

How can viruses exit the cell

A
  • Important for pathogenesis:
    • budding:
      • aquires a membrane
    • Lysis:
      • break the cell open and release the virion
    • Release viruse without lysis (poliovirus)
    • Move from cell to cell without cell lysis
20
Q

Viral Replication:

dsDNA virus:

Steps 1-3

A

Herpesvirus Replication - replicates in the nucleus

  • Protein vhs:
    • cuts up the host cell mRNA which blocks host cell defenses
  • Protein VP16:
    • facilitates the transcription of herpesvirus RNA
21
Q

Viral Replication:

dsDNA virus:

Steps 4-5

A

Herpesvirus replication - replicates in the nucleus

  • Three types of mRNA produced by the virus
    • a - immediate earyly
    • B - early
    • y - late
22
Q

Viral Replication:

+RNA virus (Coronavirus)

A

Replicates in the cytoplasm

Buds in the ER/Golgi

Only makes 8 viral proteins

23
Q

Viral Replication:

Retrovirus

A

Retroviruses have a provirus step

They replicate in the Nucleus for the DNA step

If a retrovirus infects a germ cell there cen be a generational infections (vertical transmission)

When the cell divides the virus divides with it because of hte provirus

Veterinary Virology DMP851 (12 decks)

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