6 Herpesviruses

Question 1

where are herpesviruses

Answer 1

widely disseminated in nature

Question 2

how many herpes viruses are there

Answer 2

eight human herpesviruses have been isolated

Question 3

what are the herpesviruses

Answer 3

• herpes simplex virus 1 and 2
• varicella zoster virus
• human cytomegalovirus
• Epstein-Barr virus
• human herpesviruses 6-8

Question 4

herpesviruses genome

Answer 4

contain a linear, ds DNA genome

Question 5

what encloses the capsid

Answer 5

capsid enclosed in viral tegument, lipid and glycoprotein envelope

Question 6

Herpes simplex virus 1 (HIV-1) components

Answer 6

1. core
2. icosahedral capsid
3. tegument
4. envelope
   Linear, dsDNA genome

Question 7

Herpesvirus DNA - genome difference

Answer 7

• herpesvirus genomes vary greatly in size, base composition and structure
• genomes vary in length from 120kb to 230kb and contain different arrangements of unique and repeat sequences

Question 8

what are HSV-1 genomes like

Answer 8

Segmented linear genomes
Unique long (UL) and Unique short (US) covalently attached molecules

Question 9

genes in unique long segment in HSV-1

Answer 9

> 62

Question 10

genes in unique short segment in HSV-1

Answer 10

> 12

Question 11

HSV-1 genomes UL and US segments

Answer 11

Both segments can be inverted

Question 12

what effect does the inversion of UL and US segments cause

Answer 12

resulting in 4 different genome rearrangement possibilities

Question 13

what are the 4 genome rearrangement possibilities

Answer 13

P, IL, IS or ILS

Question 14

what are the sub divided herpesviruses

Answer 14

three sub-families on basis of differences in:

• host range and tissue tropism in vivo
• host cell range and growth characteristics in vitro
• site of latent infection

Question 15

Herpesviridae classification

Answer 15

Beta, gamma and alpha

Question 16

what do all herpesvirus encode

Answer 16

all encode many enzymes involved in metabolism (encode virtually all the genes that they need)

Question 17

what occurs in nucleus

Answer 17

viral DNA synthesis and capsid assembly

Question 18

what destroys the infected cell

Answer 18

release of progeny virus

Question 19

what happens in cell entry

Answer 19

Herpes simplex expresses a range of surface proteins
Virus first has to be stabilised on the surface
Herpes virus glycoproteins interact with cell receptors
Will start a fusion with cell membrane and herpes will enter the cell

Question 20

Endocytosed

Answer 20

low pH-dependent fusion

Question 21

Micropinocytosis

Answer 21

pH-independent fusion

Question 22

Expression of viral genes

Answer 22

Occurs in regulated cascade:

• immediate early genes: essential for co-ordinate regulation of other viral genes
• delayed early genes: encode proteins essential for viral DNA replication
• late genes: encode structural proteins

Question 23

HSV-1 genome genes encode

Answer 23

Some genes encode early transcription factors ( genes)

Question 24

Enhancer region

Answer 24

increase expression

Question 25

where is the TAATGARAT sequence

Answer 25

upstream

Question 26

in viral replication what is need

Answer 26

Enters as linear DNA Organised into nucleosomes – tight and DNA condensed Simplex genome enters – will be shut off unless HCF-1 opens it HCF-1 host cell factor 1 open chromatin

Question 27

what happens when virus first expressed

Answer 27

innate immune response acts quickly

Question 28

how are cells killed

Answer 28

interaction between nucleofector that turns on all genes e.g. interferon, innate lead to cell being killed

Question 29

how is HSV-2 transmitted

Answer 29

sexual contact

Question 30

how many adults are seropositive for HSV-2

Answer 30

10-30%

Question 31

what is latency

Answer 31

establish latent infection infection in dorsal root ganglia of sensory nerves (stay at stable number in dorsal root ganglia – only one region of virus expressed – latent)

Question 32

how can HSV-1 infect

Answer 32

Can enter through crack in e.g. nail

Question 33

HSV-1 in eye effect

Answer 33

replicate in cornea (denrditic ulcer, then infect anterior chamber)

Question 34

how can HSV-2 infect

Answer 34

Sexual organs | Mother giving birth with herpes simplex – high mortality rate for baby

Question 35

which HSV causes brain bleeding

Answer 35

HSV-2

Question 36

what is Alphaherpesvirus

Answer 36

VZV is endemic in most populations - chicken pox | Primary infection

Question 37

how does Alphaherpesviruses infect

Answer 37

occur via the respiratory route

Question 38

how many are infected by Alphaherpesviruses

Answer 38

At least 10% of population remain uninfected

Question 39

what is HCMV

Answer 39

human cytomegalovirus

Question 40

what are the herpesvirus 6 and 7

Answer 40

Betaherpesviruses

Question 41

how prevalent is HCMV

Answer 41

Prevalence of HCMV in adult populations is 70%

Question 42

what is HCMV a result of

Answer 42

- intrauterine infection - perinatal infection - intimate or sexual contact - transfusion of whole blood, cellular products or solid organs

Question 43

what is the seroprevalence of EBV

Answer 43

80-90%

Question 44

where does EBV replicate

Answer 44

in epithelial cells of oro-pharynx

Question 45

where does EBV establish latency

Answer 45

EBV establishes latent infection in dividing populations of B cells

Question 46

what can primary infection with EBV cause

Answer 46

'glandular fever’ syndrome

Question 47

what is chronic infection associated with

Answer 47

associated with three important diseases: - Burkitt’s lymphoma - nasopharyngeal carcinoma - other lymphomas

Question 48

where is Burkitt’s lymphoma problematic

Answer 48

Burkitt’s lymphoma is endemic in the malaria belt of equatorial Africa

Question 49

what is Burkitt's lymphoma associated with

Answer 49

100% of endemic BL is associated with EBV infection

Question 50

what causes Burkitt’s lymphoma

Answer 50

arises in B cells expressing type 1 latency

Question 51

how does Nasopharyngeal carcinoma arise

Answer 51

Arises from epithelial cells expressing ‘type II’ EBV latency genes

Question 52

what does Nasopharyngeal carcinoma require

Answer 52

additional environmental and genetic co-factors