HSV 1 and 2 Flashcards
HSV 1 and 2 replicate where?
Epithelial cells
Where do HSV 1 and 2 reside?
trigeminal or sacral ganglia
HSV structure?
Large, ds DNA, icosahedral capsid, lipid envelope
After viral attachment, HSV fuses with the plasma membrane in a pH- INDEPENDENT MANNER
Know
What is significant about the initial transcription/translation (immediate early expression) process for HSV?
produces proteins that act as transcriptional regulators that modify host RNA polymerase so that it preferentially transcribes viral genes over host genes.
What are early proteins?
Proteins whose role is to replicate virus genome to produce progeny genomes.
Examples of early proteins?
Thymidine Kinase and DNA polymerase
What is clinicaly important about thymidine kinase?
it is needed to phosphorylate acyclovir and its derivatives. Acyclovir is the DOC in most HSV infections
ACV is interesting because, due to it needing the viral thymidine kinase in order to be activated, it is much more specific for infected cells than non-infected cells. However, Thymidine kinase mutants are often resistant to ACV.
ok
Thymidine kinase mutants seen most often in?
AIDS pts
Viral DNA polymerase is the ultimate target of….
Acyclovir
The “late” proteins encode what?
capsomeres, envelope glycoproteins, other structural proteins
Virus assembly occurs where ?
Nucleus
KNOW THIS: Because the viral glycoproteins responsible for the initial fusion/ entry are still present in the plasma membrane of the infected cells late in infection, infected cells can fuse with adjacent uninfected cells. This leads to the formation of syncytia (cells with more than one nucleus).
This means that HSV can spread from cell to cell without the formal release of virus progeny.
Which diagnostic test for HSV tests for Syncytia?
Tzanck Smear
What specifically does a Tzanck Smear look for?
Smears of cells are taken from an ulcerous lesion and viewed under a microscope looking for multinucleated giant cells with Nuclear Inclusion Bodies
During latency, HSV’s virus genome is stored
extrachromosomally
The only HSV gene expressed during the maintenance of latency is called
LAT (Latency associated transcript)
What is LAT
it is a gene that codes an RNA species that silences a subset of cellular genes to prevent apoptosis
HSV 1 is traditionally
Above the belt
HSV 2 is traditionally
Below the belt
Disseminated disease caused by HSV is a problem among who?
Immunocompromised patients and neonates
Symptoms
- significant percentage = asymptomatic
- if symptomatic, multiple blisters form on the infected skin about two weeks following infection. These blisters rupture and produce mildly to severely painful lesions which take up to 2 weeks to heal.
Recurrent infections occur when
When cell mediated immunity is low
Primary gingivostomatitis
Vesicles occur on the lips, tongue, and facial skin surrounding the mouth
Recurrent oral infections generally result in
fever blisters
HSV 2 genital infections recur more frequently that HSV1 genital infections
ok
KNOW
virus shedding can occur in the absence of recurrent vesicles and well after lesions are unapparent
Ocular HSV
Blepharitis and conjunctivitis are most often seen in children and are usually present as small vesicles or pustules around the eye lid
Keratitis
can result in significant corneal scarring if left untreated, chartacteized by red painful eye, blurred vision, photophobia
Encephalitis is a result of:
result of recurrent HSV1 in adults and primary HSV 2 in neonates
Herpes encephalitis is severe
70% mortality if left untreated
Meningitis
occurs in 10% of primary HSV 2 and is goes away in a week usually
Genital herpes diagnosis
- Culture: takes 3-10 days depending on the inoculum for the cytopathic effect to appear
- Flourescent antibody screeening
- Serology: detects antibody to glycoprotein G , can distinguis 1 and 2 but only indicates past infection
- Tzanck smear:
