Lec 13 - Latent infections 2 Flashcards

1
Q

which gene products are made and which are made less

A
  • those promoting replication not made, or little bit
  • those promoting latency are expressed
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2
Q

3 types of genomes in latent/persistent viruses

A
  • non replicating genome in non divinding cell
  • autonomously replicating genome in dividing cell
  • integrated in host chromosome
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3
Q

wha is biggest viral family that uses latency

A

herpesviridae

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4
Q

what does epstein barr virus code for in the host cell

A

restricted number of transcripts
so a restricted number of proteins
so the host immune defences dont recognise it

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5
Q

alphaherpesvirus: role of envelope proteins

A
  • recognsiing host cell
  • bind to it
  • getting in
  • assist trafficking
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6
Q

alphaherpesviridae: tegument layer

A

function is unknown
but important for viral replication

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7
Q

what type of structure does alphaherpesviridae have

A

dsDNA
icosahedral

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8
Q

how many people sero positive for HSV1

A

80%
many wont experience reactivation and cold sores

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9
Q

where is the resovoir HSV

A

periperal nervous system

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10
Q

how does HSV end up infecting a sensory ganglion

A
  • replicate in oral mucosal epithelial cells initially
  • get into epi tissue
  • get into sensory neurones and move to cell body via fast axonal transport
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11
Q

what happens once HSV gets into cell body

A
  • cant be seen by immune system
  • becomes latent
  • if it gets reactivated, then can move back down peripheral neurone and reinfect mucosal epithelial cells
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12
Q

what could happen in HSV if immune system highly compromised

A

can move the other way from the cell body into the CNS
which would be fatal

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13
Q

what is the nucelosome-associated episome

A

virus is not integrated in host genome, but its genome exists in host cell nucleus

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14
Q

name of transcript that is expressed in HSV latency

A

latency associated transcript (LAT)

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15
Q

what does LAT transcript do

A

prevents expression of genes associated with lytic phase
and viral replication and assembly

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16
Q

during HSV acute infection: what is the trancriptional activator/tegument protein needed to encode immediate early genes

A

VP16

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16
Q

when does VP16 enter the cell

A

when the nucleocapsid enters the nucleus, it also enters

17
Q

HSV1: how are genes usually transcribed

A

3 batches:
- immediate early = transc factors made etc
- early = proteins for replication
- late = assembly proteins

18
Q

how is HSV infection of the neurons different

A

vp16 does not enter the nucleus = no transc of imm early genes
and only thing that is made is the LAT transcript

19
Q

what key transcription factor does LAT transcript suppress

A

ICP0

20
Q

what has been iimplicated as a possible reason for reactivation and why

A

-stress
-cortisol rises
- chromatin remodelling occurs
- may lead to release of the transcriptional silencing on the gene to code to VP16

21
Q

varicella zoster: what complications might someone w chicken pox get

A

pneumonia
encephalitis

22
Q

varicella zoster: where does it remain dormant

A

human ganglionic neurons

23
Q

varicella zoster: when reactivates, what symptoms does shingles cause

A

painful vesicular skin eruption along sensory dermatomes

24
Q

varicella zoster: where does it first replicate

A

macrophage
pneumocytes
(in lymph nodes and resp mucosa) = primary viremia

25
Q

varicella zoster: secondary viremia

A

leaves blood vessels in T cells
infects epithelial tissue throughout body = rash, can be shed from lungs also

26
Q

varicella zoster: during latency, how many genes are trancribed

A

5

27
Q

varicella zoster: which of the genes transcribed in latency inhibit apoptosis

A

63

28
Q

what family is epstein barr virus in

A

gammaherpesviridae

29
Q

what % of people carrying EPV

A

85% of adults

30
Q

where does EBV lie latent

A

non proliferating B lymphocytes

31
Q

what cells initially get infected by EBV and how

A

subpharyngeal epithelial saliva
by saliva

32
Q

what happens when a resting B cell is infected by EBV

A

replication of B cell is triggered

33
Q

EBV: what are the 2 viral proteins expressed on surface of B cells

A

LMP-1 and LMP-2
which are targets for the immune system

34
Q

EBV: how many survive and persist after the immune attack

A

1 in 100,000 only
and persist as non proliferating memory B cells

35
Q

EBV: in the latent B cell, what viral protein is made in the nuclus

A

EBVNA-1
hidden from immune system

36
Q

EBV: what protein is thought to initiate reactivation and how

A

Zta
by activating host erg1 gene = important for replication of EBV

37
Q

measles: what is SSPE

A

subacute sclerosing panencephalitis

38
Q

measles: when might SSPE happen

A

6-8 yrs after measles infection

39
Q

measles: SSPE

A

cognitive decline
behavioural changes
seizures
gradual decline with no known treatment

40
Q

measles: how might the virus enter neuronal cells in SSPE

A

fusion protein on measles virus gets mutated which allows it to recognise neuronal receptors which allows it access