HSV-1/2: Ryan Flashcards
HSV virus structure differs from HPV by:
Having a lipid envelope that surrounds the icosahedral capsid
Why are HSVs termed “neurotropic”
They infect and replicate in epithelial cells, then reside (their genomes, not progeny) latently in trigeminal or sacral ganglia (depending on site of infxn).
HSV2 generally causes facial or genital lesions?
Genital
1- above waist (and below, sometimes)
2- below waist
What is thymadine kinase and why are mutants of it a problem for treatment of HSV?
Thymadine kinase (TK) is a component of virally-encoded DNA polymerase that activates acyclovir used to treat HSV. Mutants of TK won’t activate acyclovir, thus rendering the HSV resistant to treatment with that first-line drug.
How do the syncitia (multinucleated giant cells) of HSV infection form?
Bc the same viral glycoproteins responsible for initial fusion (entry) into the host cell are also present in the PM of infected cells late in infxn, infected cells may fuse with adjacent, uninfected cells.
What are we looking for in a Tzanck smear to Dx HSV?
multinucleated giant cells with nuclear inclusions (due to viral assembly in the nucleus)
Is the viral genome maintained chromosomally or extrachromasomally in the latent phase in ganglia?
Describe the only gene expressed during latency and its function.
Extrachromosomally, like a plasmid
LAT (latency associated transcript) is expressed during latency to silence a subset of cellular genes that would otherwise “give the hiding virus away” to the host immune system, thus compromising its latency.
How is it that HSV infections presenting superficially do not spread all over the place?
Limited in size and duration by neutralizing host abs.
Describe the ocular infections caused by HSV.
Primary blepharitis and conjunctivitis most commonly seen in children. Usually present as small vesicles or pustules around the eye lid.
Recurrent: keratitis can result in significant corneal scarring if left untreated.
Describe the CNS infections of HSV.
Encephalitis, the result of recurrent HSV1 in adults but primary HSV2 in neonates exposed during vaginal birth.
Adults: headache/fever—> confusion, seizures
Meningitis (HSV2): headache, stiff neck, vomiting. Resolves after 1 wk.
Neonates: present 1-2 wks PP. Some infxn limited to skin, eyes, mouth. Good prog.
CNS infxn of neonates: seizures, irritability, coma. 75% die or have sequelae.
Gold standard for distinguishing HSV1 from HSV2:
PCR
How do we tx HSV meningitis?
Wait it out. Self-limiting to 1 wk. Supportive care.
You suspect systemic HSV in your neonate pt. Check…
Liver enzymes
Can we cure a pt of HSV infection?
How do we treat it?
No, herpes is for life.
But, Acyclovir is good at lessening episodes.
MOA: inhibits DNA polymerase (needs thymidine kinase for activation)
AEs: Nausea, skin rash, diarrhea
High dose AEs: renal failure, seizures, disorientation
What do we use as back-up tx when ACV fails due to thymidine kinase mutation?
Foscarnet- does not require phosphorylation. Works the same way.
