Herpes Simplex Viruses 1 and 2 Flashcards
Structure of herpesviruses?
Large, ds-DNA viruses whose icosahedral capsids surrounded by a lipid envelope
What is the hallmark of herpes viruses?
Their ability to establish latent infections in which the virus genome, but not the virus progeny, is maintained in a quiescent state for the reminder of the host’s life.
What is the HSV replication cycle?
The virus attaches to attachment proteins and cell surface receptors. Once attached HSV directly fuses with the plasma membrane in a pH-independent manner and the released nucleocapsi migrates to the cell’s nucleus where the genome is released.
What happens after the genome as been released into the nucleus?
Initial transcription/translation (immediate early expression) produces proteins that act as transcriptional regulators that modify host RNA polymerase so that it preferentially transcribes viral genes over host genes.
The immediate early expression leads to?
The production early proteins whose roles are to replicate the virus genome to produce progeny genomes.
What are some prominent early proteins?
Thymidine kinase and components of a virally-encoded DNA polymerase
Why is the thymidine kinase important?
It is used by Acyclovir and its derivatives to be phosphorylated into their active forms.
What happens in HSV strains with thymidine kinase mutations?
ACV is ineffective
What happens once the progeny genomes are synthesized?
The late class of proteins is produced. These encode the capsomeres, envelope glycoproteins, and other structural proteins.
Where does virus assembly occur?
Nucleus
What is syncitia? How are they formed?
Giant cells with more than one nucleus.
When infected cells fuse with adjacent uninfected cells
What is a Tzanck Smear?
Viewing a smear of cells taken from an ulcerous lesion under a microscope
What are you looking for in a Tzanck Smear?
Multinucleated giant cells with nuclear inclusion bodies
Where does HSV go latent?
Peripheral sensory neurons
How is the viral genome maintained during latency?
Extrachromosomally
What is the only HSV gene expressed during the maintenance of latency?
LAT (latency associated transcript)
What is the role of LAT?
To prevent apoptosis of the infected neuron
How long after HSV becomes symptomatic do multiple blisters form on the infected skin?
About Two Weeks
What happens during a primary infection?
The blisters will rupture producing mildly to somewhat severely PAINFUL open vesicles which will take up to two weeks to heal
When do recurrent infections occur?
During lapses in cell-mediated immunity and the resulting cold sore or genital lesions are limited in size and duration due to the presence of neutralizing antibody
What is gingivostomatitis?
Symptomatic ORAL infection by either HSV 1 or 2.
Vesicles can occur on the lips tongue, and facial skin surrounding the mouth
Where do primary symptomatic genital infections by either HSV 1 or 2 occur in a male?
Vesicles can occur anywhere on the penis or perianal region and can cause urthritis (rarely)
Where do primary symptomatic genital infections by either HSV 1 or 2 occur in a female?
Vesicles can be internal or external. Can be difficult to detect even when present –> leads to mucopurulent cervicits, vaginitis, and rarely urethritis
Which herpesvirus recur more frequently?
HSV 2 genital»_space;> HSV 1 genital
