HSV, VZV Ryan Flashcards
describe herpesvirus structure
icosahedral capsid, lipid env (from host cell), dozen glycoproteins (from virus–help attach, release)
describe herpesvirus genome
linear ds DNA
where does herpesvirus replication, assembly occur
nucleus
lifethreatening herpesvirus infections occur when
immunocomp and neonates
3 classifications of herpesvirus
alpha, beta, gamma
what are the alpha herpesvirus
HSV-1, HSV-2, VZV
what do all 3 alpha herpesviruses have in common?
replicate in epith cells, neutropic latency, BLISTERS
3 important proteins in alpha herpes lytic cycle?
IE (TF), E (repln), L (structure)
LYTIC CYCLE
- bind hep sulfate on host cell surface, e-static
- lock and key intrxn with glycoprots (fusion)
- transloc –> nuc
- IE expressed from virus; host RNA pol
- E protein req for rep’n
- virus DNA pol rep’n in nucleus –> L genes exp
- L genes –> cyto, translated, –> nuc
- packaged in nuc, exocytosed
- virus rel from ER –> trans golgi network, take env
- bud
what cells do alpha herpesvirus replicate in
epith but ALSO neurons!
describe herpesvirus neuronal rep’n
uptake by periph sensory neurons from progeny of epith replication. occurs soon after infection
as herpesvirus replicates in neurons, what happens to progeny?
trans-synaptically transported retrograde towards CNS
challenges to herpesvirus for latency?
prevent lytic rep’n, apop of neuron, and immune recognition
how does herpesvirus stay latent?
Latency-assoc transcript: LAT
role of LAT
prodcues miRNAs that repress viral gene expression, apop, and CD8
what herpesviruses express LAT
HSV. not VZV
where does HSV-1 cause infection
skin, ocular, encephalitis
where does HSV-2 cause infeciton
Urogenital, meningitis
when is herpesvirus fatal
CNS, dissemination esp neonate and immunocomp
HSV pathogenesis
- secretions –> breaks in skin/mucosa
- primary inf often not noticed
- replicate in epith cell at site of inf –> nodes
- also taken up by sensory periph nn –> latency
recurrence of HSV?
not as painful if the primary infection was noticeable/ painful. Can occur 5-8x/year. due to lapse in immunity. Remain local bc so many Abs
HSV epidemiology
adult US HSV-1: >55%
adult US female HSV-2: 20%
adult male/young adult HSV-2: 10%
dx HSV
clinical dx. Serology only for primary inf
culture was gold standard, but now PCR if needed like in meningitis
Tzanck smear: take base of vesicle, look for giant cell
VZV pathogenesis
primary –> chickenpox. VERY communicable aero
winter
fever, itchy rash on scalp/trunk.
in adult? severe, PNA
replication of VZV
rep in nodes, primary viremia, rep in organs, secondary viremia, then RASH
zoster
VZV reactivated infection. SHINGLES! sudden onset pain, rash on unilat thoracic dermatome or forehead
rash 2-4 weeks, pain LONG (posttherpetic neuralgia)
dx VZV
clinical dx. Tzanck smear poss
