DNA Virus Replication Herpes Varicella Zoster Flashcards
Herpetoviridae (4):
- DS DNA wound around a protein core.
- 4 configurations of DNA.
- Icosahedral capsid.
- Envelope with glycoprotein spikes.
HSV-1 virus entry (4):
- 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).
HSV-1 DNA replication (3):
- Linear genomic DNA circularizes.
- Concatemer formation by rolling circle mechanisms.
- Specific cleavage of concatemer into unit size DNAs with reorientation.
Three types of mRNA:
- Immediate early - alpha.
- Early - beta.
- Late - gamma.
Alpha proteins:
Regulatory.
Beta proteins:
Enzymatic, required for DNA replication.
Gamma proteins:
Structural, used to form progeny virus.
HSV-1 assembly (3):
- Nucleocapsid formation in nucleus.
- Capsid passes through nuclear membrane site.
- Acquires envelope from modified membranes of cytoplasmic vesicles that have viral glycoproteins.
Two serological types of HSV:
HSV-1: Oral
HSV-2: Genital
HSV CNS infection:
Adult (HSV-1):
- Spread along olfactory nerve to temporal lobe.
Neonate (HSV-2):
- Infected birth canal leads to viremia and spread to the brain.
HSV latent state:
After primary infection HSV transported up nerves to ganglia:
- HSV-1: trigeminal.
- HSV-2: sacral.
Laboratory diagnosis of HSV (3):
- Tzanck smear - cells from base of lesion.
- Virus isolation in cell culture.
- Serological - fluorescent antibody attached to viral proteins.
Varicella infection (3):
- Respiratory route.
- Two week incubation period.
- Successive crops of rash, fever with each crop.
Varicella complications:
Adult:
- Pneumonitis: x-ray shows calcified nodules.
Children:
- Encephalitis: males 2x females.
Reyes syndrome:
Aspirin related hepatic failure, encephalopathy.
