DNA Virus Replication Herpes Varicella Zoster

Question 1

Herpetoviridae (4):

Answer 1

• DS DNA wound around a protein core.
• 4 configurations of DNA.
• Icosahedral capsid.
• Envelope with glycoprotein spikes.

Question 2

HSV-1 virus entry (4):

Answer 2

• Virus particle attaches to a receptor on surface of permissive cell.
• Virus envelope fuses with cell membrane.
• Capsid containing DNA moves to nucleus of cell.
• Genome is released into the nucleus (site of viral replication).

Question 3

HSV-1 DNA replication (3):

Answer 3

• Linear genomic DNA circularizes.
• Concatemer formation by rolling circle mechanisms.
• Specific cleavage of concatemer into unit size DNAs with reorientation.

Question 4

Three types of mRNA:

Answer 4

1. Immediate early - alpha.
2. Early - beta.
3. Late - gamma.

Question 5

Alpha proteins:

Answer 5

Regulatory.

Question 6

Beta proteins:

Answer 6

Enzymatic, required for DNA replication.

Question 7

Gamma proteins:

Answer 7

Structural, used to form progeny virus.

Question 8

HSV-1 assembly (3):

Answer 8

• Nucleocapsid formation in nucleus.
• Capsid passes through nuclear membrane site.
• Acquires envelope from modified membranes of cytoplasmic vesicles that have viral glycoproteins.

Question 9

Two serological types of HSV:

Answer 9

HSV-1: Oral

HSV-2: Genital

Question 10

HSV CNS infection:

Answer 10

Adult (HSV-1):
- Spread along olfactory nerve to temporal lobe.
Neonate (HSV-2):
- Infected birth canal leads to viremia and spread to the brain.

Question 11

HSV latent state:

Answer 11

After primary infection HSV transported up nerves to ganglia:

• HSV-1: trigeminal.
• HSV-2: sacral.

Question 12

Laboratory diagnosis of HSV (3):

Answer 12

• Tzanck smear - cells from base of lesion.
• Virus isolation in cell culture.
• Serological - fluorescent antibody attached to viral proteins.

Question 13

Varicella infection (3):

Answer 13

• Respiratory route.
• Two week incubation period.
• Successive crops of rash, fever with each crop.

Question 14

Varicella complications:

Answer 14

Adult:
- Pneumonitis: x-ray shows calcified nodules.
Children:
- Encephalitis: males 2x females.

Question 15

Reyes syndrome:

Answer 15

Aspirin related hepatic failure, encephalopathy.

Question 16

Zoster (2):

Answer 16

• Latency in dorsal root ganglia.

- Macular rash –> papule –> vesicle (–> pustule) –> crust.

Question 17

Zoster tx:

Answer 17

Zoster immune globulins.

Question 18

Zoster vaccine:

Answer 18

Attenuated live vaccine.