Lec 13 - Latent infections 2

Question 1

which gene products are made and which are made less

Answer 1

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

Question 2

3 types of genomes in latent/persistent viruses

Answer 2

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

Question 3

wha is biggest viral family that uses latency

Answer 3

herpesviridae

Question 4

what does epstein barr virus code for in the host cell

Answer 4

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

Question 5

alphaherpesvirus: role of envelope proteins

Answer 5

• recognsiing host cell
• bind to it
• getting in
• assist trafficking

Question 6

alphaherpesviridae: tegument layer

Answer 6

function is unknown
but important for viral replication

Question 7

what type of structure does alphaherpesviridae have

Answer 7

dsDNA
icosahedral

Question 8

how many people sero positive for HSV1

Answer 8

80%
many wont experience reactivation and cold sores

Question 9

where is the resovoir HSV

Answer 9

periperal nervous system

Question 10

how does HSV end up infecting a sensory ganglion

Answer 10

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

Question 11

what happens once HSV gets into cell body

Answer 11

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

Question 12

what could happen in HSV if immune system highly compromised

Answer 12

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

Question 13

what is the nucelosome-associated episome

Answer 13

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

Question 14

name of transcript that is expressed in HSV latency

Answer 14

latency associated transcript (LAT)

Question 15

what does LAT transcript do

Answer 15

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

Question 16

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

Answer 16

VP16

Question 16

when does VP16 enter the cell

Answer 16

when the nucleocapsid enters the nucleus, it also enters

Question 17

HSV1: how are genes usually transcribed

Answer 17

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

Question 18

how is HSV infection of the neurons different

Answer 18

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

Question 19

what key transcription factor does LAT transcript suppress

Answer 19

ICP0

Question 20

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

Answer 20

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

Question 21

varicella zoster: what complications might someone w chicken pox get

Answer 21

pneumonia
encephalitis

Question 22

varicella zoster: where does it remain dormant

Answer 22

human ganglionic neurons

Question 23

varicella zoster: when reactivates, what symptoms does shingles cause

Answer 23

painful vesicular skin eruption along sensory dermatomes

Question 24

varicella zoster: where does it first replicate

Answer 24

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

Question 25

varicella zoster: secondary viremia

Answer 25

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

Question 26

varicella zoster: during latency, how many genes are trancribed

Answer 26

5

Question 27

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

Answer 27

63

Question 28

what family is epstein barr virus in

Answer 28

gammaherpesviridae

Question 29

what % of people carrying EPV

Answer 29

85% of adults

Question 30

where does EBV lie latent

Answer 30

non proliferating B lymphocytes

Question 31

what cells initially get infected by EBV and how

Answer 31

subpharyngeal epithelial saliva
by saliva

Question 32

what happens when a resting B cell is infected by EBV

Answer 32

replication of B cell is triggered

Question 33

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

Answer 33

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

Question 34

EBV: how many survive and persist after the immune attack

Answer 34

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

Question 35

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

Answer 35

EBVNA-1
hidden from immune system

Question 36

EBV: what protein is thought to initiate reactivation and how

Answer 36

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

Question 37

measles: what is SSPE

Answer 37

subacute sclerosing panencephalitis

Question 38

measles: when might SSPE happen

Answer 38

6-8 yrs after measles infection

Question 39

measles: SSPE

Answer 39

cognitive decline
behavioural changes
seizures
gradual decline with no known treatment

Question 40

measles: how might the virus enter neuronal cells in SSPE

Answer 40

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