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HELENP CBG VIROLOGY AND IMMUNITY > CBG Lecture 21: Viral Replication > Flashcards

CBG Lecture 21: Viral Replication Flashcards

1
Q

what are MAIN steps of viral replicaiton

A

infection and disassembly of infectious virus particle
replication viral genome
synthesis viral proteins using host cell machinery
reassembly into progeny virus particles

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2
Q

what is eclipse phase

A

basically see no virus: virus starts to build up proteins and switch to replication

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3
Q

what is phase called where you “see” no virus, but virus is building up and using host cells machinery to swtich to replication

A

eclipse phase (think lag)

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4
Q

what is maturation and release phase

A

virus matures morphologically and can occur outside of cell

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5
Q

what is the phase where the virus matures morphologically

A

maturation and release phase

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6
Q

what is cell/tissue tropism

A

where different viruses recognise different cell receptors on cell surface - determining which cells get infected

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7
Q

what type of viral receptors are there

A 
integrins for DNA viruses
CD21 fir estein barr virus
CD4 for HIV1/2
Glycoproteins
Ach receptor for rabies
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8
Q

which receptor does rabies use

A

ACh

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9
Q

which receptor does HIV use

A

CD4

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10
Q

which receptor does epstein barr use

A

CD21

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11
Q

which receptor does adenovirus use

A

integrins

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12
Q

how does HIV show cellular tropisms

A

mutations allow switching between cell targets as HIV can attach to either alpha or beta chemokine receptro

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13
Q

which receptor can HIV attach to

A

CD4 with alphaa OR beta chemokine receptor

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14
Q

which virus attaches to CD4 with alpha or beta chemokine receptor

A

HIV

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15
Q

what are common mechanisms used by viruses to infect a host cell as a prelude to viral replication

A

fusion or endocytosis

uncoating = disassembly

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16
Q

how does HIV undergo infection and disassembly

A

fusion then uncoating, leave env proteins on membrane

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17
Q

how does influenz undergo infection and disassembly

A

endocytosed, then fusion and uncoating within an endosome as it becomes acidified

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18
Q

how does polio undergo infection and disassembly

A

endocytosed then uncoating

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19
Q

which virus undergoes fusion then uncoating, leave env proteins on membrane

A

HIV

20
Q

which virus undergoes endocytosed, then fusion and uncoating within an endosome

A

influenz

21
Q

how do non envelope proteins enter host cell

A 
capsid binds to cell receptor as no env proteins
cant fuse cos no lipid membrane
endocytosis
conformational change
extruded RNA
22
Q

why cant non env proteins fuse with cell membrane

A

they have no env proteins

23
Q

where do RNA viruses tend to end up

A

in cytoplasm

24
Q

where do most DNA viruses replicate

A

in nucleus

25
Q

which dna virus doesnt replicate in nucleus

A

poxvirus

26
Q

which rna virus doesnt replicate in cytoplasm

A

retrovirus

27
Q

which viral rna genome is equivalent to mRNA and can therefore have direct translation

A

ssRNA+

28
Q

what is ssRNA+ the same as

A

mRNA

29
Q

how does ssRNA+ viruses replicate

A

genome is mRNA so can translate dirctly

uses cells RNa dep. RNAP to turn from +sense to -sense so that product is +sense

30
Q

how does ssRNA- virus replicate

A

its antisense to mRNA so RNA dep RNAP mst be carried to synthesis mRNA
cant translate directly so needs viral polymerase to transfer to +sense then translate

31
Q

how is dsDNA virus replicated

A

normal transcription in nucleus using cells DNAP

32
Q

why doesnt poxvirus need nucleus to replicate

A

becuase they carry a transcription mechanism

33
Q

how do retroviruses replicate

A

they carry a RT to make DNA out of the RNA

use their RT to made dsDNA out of their RNA, then integrate the dsDNA into chromosome

34
Q

where does capsid assembly normally happen

A

@ site of viral genome replication- often self assembly with simultaneous binding of viral genome to capsid rpoteins

35
Q

where are viruses with envelopes usually assembled

A

either on surgace of cell or in sub cellular compartment

36
Q

where is viral membrane derived from

A

the host cell

37
Q

what two types of assembly of viruses are there

A

subsurface-smallpox

surface- retroviruses

38
Q

outline the lifecycle of HIV1

A 
entry into cell
loss envelope
RT makes DNA/RN then DNAds
integration of DNA copy into host
transcription
translation of capsid protein,env protein and RT then spontaneous assembly
39
Q

what are the main domains of HIV1 genome

A

gag- make capsid
pol - non structural:replicative function proteins:RT/protease/integrase
env=envelope

40
Q

what does pol domain do

A

make non structural proteins eg.enzymes: RT protease integrase

41
Q

what is vpr gene on Retroviruses

A

counteract defence protein+immune system of host cell - budding

42
Q

which gene involved in counteractng immune system and budding of HIV

A

vpr

43
Q

which genes regulate expression of HIV

A

tat and rev

44
Q

which gene is a cell cycle arrest in HIV

A

vpu

45
Q

what is vif gene

A

in absence of vif, a virus is hypermutated (G to A in DNA sequence) caused by host defence protein
vif is virus counter defence protein for hypermutation and prevents tetherin stopping viruses

46
Q

what gene counteracts hypermutation by host cell

A

vif stops host hypermutating

HELENP CBG VIROLOGY AND IMMUNITY (8 decks)

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