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virology > lecture 7 > Flashcards

lecture 7 Flashcards

1
Q

Replication of Viruses

A
  • do not have genetic capability to multiply by division
  • hijacks and utilizes host cell machinery to produce its proteins and nucleic acid for next generation of virus
  • process of virus replication in host cell resembles assembly line
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2
Q

permissive cell

A

cell is which a virus is able to replicate

the cell machinery supports replication of the virus

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3
Q

non-permissive cell

A

cells in which a factor or factors necessary to viral reproduction is not present or one detrimental to viral reproduction is absent

eg. absence of appropriate receptors

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4
Q

MOI (multiplicity of infection)

A

refers to the number of virions that are added per cell during infection

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5
Q

latent period

A

after uncoating and till just before 1st appearance and release of extracellular new virus particle

no extracellular virions detected

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6
Q

eclipse period

A

after uncoating and till just before first appearance of intracellular new virus progeny particles

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7
Q

adsorption

A

during this period virus attaches to and enters cell, titer of free virus in medium may decline

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8
Q

burst size

A

number of infectious virions released per average cell

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9
Q

virus attachment

A
  • attachment to receptor/s on host cells is/are very specific, lock and key like
  • each virus has its own specific receptor/receptors on specific host cells
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10
Q

attachment to the host cell surface

A
  • mediated by interaction between the virus and complimentary receptor on host cell surface, cell that lacks appropriate receptor escape being infected by virus
  • some cases, binding to cellular receptor is not sufficient for infection, additional cell surface molecule, or co-receptor required for entry
  • some viruses may use more than one host cell receptor, such as HIV
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11
Q

co-receptor

A

in some cases, binding to a cellular receptor is not sufficient for infection
-additional cell surface molecule, or co-receptor is required for entry

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12
Q

viruses can enter the host cell using any receptor present on surface of host cell

T/F

A

F

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13
Q

penetration /uncoating of non-enveloped/naked viruses

A
  1. receptor mediated endocytosis (commonly seen)

2. pore mediated penetration (in some naked viruses)

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14
Q

penetration and uncoating of enveloped viruses (depends on type of fusion protein)

A
  1. surface membrane fusion (have pH independent fusion protein)”
  2. receptor mediated endocytosis (have pH dependent fusion protein)
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15
Q

other/ uncommon methods of entry into host cell

A

-antibody- mediated attachment and penetration, as in FIPV

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16
Q

Virus penetration in many non-enveloped viruses

A

-Clathrin-mediated endocytosis or receptor-mediated endocytosis of virus by host

17
Q

less common virus penetration in non-enveloped viruses

A

pore-mediated penetration of viral genome into host cell

18
Q

surface membrane fusion of enveloped viruses

A
  • fusion of virus envelope with host cell membrane occurs directly on surface of host cell
  • facilitated by pH independent fusion protein
19
Q

receptor mediated endocytosis of enveloped viruses

A
  • pH dependent fusion protein
  • fusion of virus membrane with host endosomal membrane release viral genome
  • fusion protein requires low pH to be activated which is achieved in the endosome
20
Q

True/false antibody mediated attachment is used by viruses to penetrate the host cell

A

true

21
Q

virus uncoating

A
  • release of viral genome into the host cell

- virion can no longer be detected

22
Q

uncoating results in…..

A

loss of infectivity of virions

23
Q

functions of the parent virus in the host cell

A
  1. produce multiple copies of new viruses (children/progeny)
  2. produce viral proteins for capsid and successful replication
24
Q

reverse transcriptase

A

converts viral RNA to cDNA during virus replication

25
Q

processing of primary RNA transcript (Pre-mRNA)

A
  • viral mRNA must conform to requirements of host cell translation system i.e the host cell can recognize mRNA and translate
  • series of modification occurs known as processing of primary RNA transcript/pre-RNA
  • after processing mRNAs are translated into the cytoplasm
  • viral mRNAs produced in the nucleus must also be exported to the cytoplasm
26
Q

processing of primary RNA transcript (Pre-mRNA)

A
  1. capping
  2. addition of 3’ poly-adenylated tails
  3. splicing
27
Q

capping

A

-addition of 7-methylguanosine to the 5’ end of RNA

28
Q

RNA splicing

A

process which removes introns (non-coding region) and joins exons (coding region) in primary transcript

29
Q

monocistronic mRNA

A

mRNA that encodes one polypeptide

30
Q

polycistronic mRNA

A

mRNA encodes several polypeptides

31
Q

assembly and maturation

A
  • assembly of virus genome and proteins into new virions follow a specific order
  • all components, including nucleic acids and proteins, are packaged to form mature virions
  • may take place in nucleus, cytoplasm, plasma/ cell membrane (most enveloped viruses)
32
Q

naked virions release progeny by….

A

lysis of host cell (cannot exit by budding because they lack envelope)

33
Q

enveloped virions release progeny by….

A

budding through the plasma membrane

34
Q

exocytosis

A

viruses that acquire envelope while budding from ER, golgi apparatus, or nuclear/nucleus membrane leave infected host cell by exocytosis

35
Q

replication of retroviruses uses….

A
  • reverse transcriptase (synthesizes RNA into DNA)

- integrase (integrates viral DNA to host genome)

36
Q

viruses can acquire the lipid envelope only from the cell membrane of infected host cells?

T/F

A

F

37
Q

methods of cell-to-cell spread of viruses

A
  1. extracellular spread
  2. intercellular spread
  3. nuclear spread of virus genome
38
Q

intercellular spread

A

results in rapid virus dissemination, evasion of immune system, and persistent infections

virology (12 decks)

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