Herpeviruses

Question 1

Herpevirus structure

Answer 1

Core surrounding dsDNA surrounded by proteinaceous core
Complex icosahedral capsid
Tegument
Envelope with Glycoproteins

Question 2

2 lifecycles of herpeviruses

Answer 2

Lytic and latent

Question 3

Herpevirus subfamily alpha host range

Answer 3

Variable

Question 4

Herpevirus subfamily alpha spread speed

Answer 4

Rapid in tissue culture

Question 5

Where is latency maintained in alpha herpeviruses

Answer 5

Sensory ganglia

Question 6

What is host range of beta herpreviruses

Answer 6

Restricted

Question 7

Rate of spread for beta herpeviruses

Answer 7

Slow, cells become enlarged

Question 8

Where is latency mainted in beta herpeviruses

Answer 8

Lymphoreticular cells

Question 9

What is host range of gamma herpeviruses

Answer 9

Very restricted

Question 10

Where do herpevirus gamma replicate

Answer 10

Lymphoblastid cells and epitheliod cells

Question 11

Where are gamma herpeviruses latent in?

Answer 11

T and B cells

Question 12

How is HSV genome organised?

Answer 12

Long and short segments covalently linked flanked by inverted repeats

Question 13

Lytic replication cycle steps

Answer 13

Virus entry
Transcription- IE, DE, late gene expression
Genome replication
Virus assembly
Release

Question 14

Virus entry of herpeviruses steps

Answer 14

gB and gC bind to cell surface proteoglycans, heparin sulphate
Attatchment is stabilised by gD binding to herpesvirus entry mediators

Question 15

Penetration of host cell by herpevirus

Answer 15

pH independent fusion where gB, gD, gH and gL are involved

Question 16

Upon cell entry of herpevirus where is the nucleocapsid transported

Answer 16

Nuclear pore via microtubules

Question 17

In lytic gene expression (herpes) how are viral protein groups expressed

Answer 17

Temporal cascade, IE, E and L. IE is needed to make E, E is need for L.

Question 18

IE

Answer 18

Switch on expression for viral genes

Question 19

E

Answer 19

Enzymes required for DNA metabolism and replication

Question 20

L

Answer 20

Structural genes form virus particle

Question 21

Initation of IE expression steps

Answer 21

• First genes transcribed during viral lytic infection are the IE genes
• Transcription initates by recruitment of cellular factors to IE promoters
• Enhanced by the tegument protein, VP16 or alpha-TIF binding to viral promoter
• VP16 interacts with Oct-1, HCF, TFIIB and TFIID transcription factors

Question 22

IE proteins

Answer 22

ICP0, ICP4, ICP27, ICP47

Question 23

ICP0 functions

Answer 23

Promiscous transactivator of all classes of HSV genes
Disrupts cellular ND10

Question 24

Function of ICP4

Answer 24

Essential for transactivating all early and late genes

Question 25

Function of ICP27

Answer 25

Transactivates late genes acts at postranscriptional level. Stabilises mRNA

Question 26

ICP27

Answer 26

Interferes with host immune response, affect MHc class I presentation

Question 27

Where does herpevirus replication occur?

Answer 27

Replication compartments

Question 28

What seven viral genes are essential for virus genome replication

Answer 28

UL9 - origin binding protein
ICP8- ss DNA binding protein
UL5/UL8/UL52 helicase/primase complex
UL30/UL42 DNApol

Question 29

Early steps of HSV1 genome replication

Answer 29

1. To initiate DNA replication UL9 binds to 1 of 3 origins of replication (ori) after
   viral genome circularises
2. UL9 in conjunction with ICP8 , causes a bend in the DNA, forming a stem loop
   and unwinding of the DNA
3. Helicase/primase complex (UL5, 8, 52) binds the single stranded DNA and
   synthesises RNA primers
4. Viral polymerase (UL30, 42) binds RNA primers and starts synthesis of DNA