herpes Flashcards
Human Herpesviruses
genome
eveveloped?
geometry
dsDNA
enveloped
iscoshedral
herpes genome size
125,000 - 236,000 base pairs
Herpesviridae family members share four significant biological properties:
- Encode a large array of enzymes involved in
a. nucleic acid metabolism (thymidine kinase)
b. DNA synthesis (DNA polymerase, helicase, primase)
c. protein processing (protein kinases) - Synthesis of viral DNAs and capsid assembly occur in the nucleus, while final processing of virions occurs in the cytoplasm
- Production of virus results in destruction of the infected cell
- Able to exist in a latent state in their natural hosts while retaining the capacity to replicate and cause disease upon reactivation
groups of herpes virus
Alpha, beta and gamma
alpha herpes viruses
beta herpes viruses
gamma herpes viruses
HSV 1, 2 transmission/ POE
direct contact
mucus membranes and skin
VZV transmission and POE
inhalation/ direct contact
respiratory tract and mucus membrane
CMV transmission and POE
saliva and blood
mucus membrane and bloodstream
EBV transmission and POE
saliva and blood
mucus membrane and bloodstream
fragility of herpes virus
Herpes viruses are fragile (enveloped)
susceptible to heat, detergent, drying
herpes virus infection usually requires?
why mucus membranes?
CMV/EBV can transmit thru?
VZV mainly transmitted thru?
Generally require direct inoculation
mucous membranes more susceptible than skin
CMV and EBV can be transmitted through infected leukocytes
VZV is mostly transmitted by aerosols
Herpesvirus infection of cells entry? nucleus involved? gene expression? where is capsid assembly? envelope? lytic? adjacent cells affected?
similar to adenovirus- entry and uncoating with factors and nucleporteins entering the nucleus
cascade of gene expression occurs with transcription regulators present
capsid assembly occurs in nucleus
budding at ER to acquire envelope
releases at cell mem- lytic cycle
Attach to and infect adjacent cells upon release
Budding directly onto and into adjacent cells, Therefore get a local spread of virus
(predominantly)= Syncytia can form
herpesvirus and nuclei
alter of nuclei?
syncitia?
Tzanck cells?
Virus replicates and assembles in the cell nucleus
Get changes in nuclear structure - chromatin shifted to margins of nucleus
Cowdry type A acidophilic intranuclear inclusion bodies
Stained cells infected with a herpes virus show syncytia formation (multinucleated
cells)(= Tzanck cells from Tzanck smear (scraping from the base of the lesion) and
intranuclear inclusion bodies (darkly staining nuclear region).
anti herpes Ab role
Anti-herpesvirus antibodies play minor role in recovery from primary disease and
on recurrent disease
But anti-herpesvirus antibodies can help prevent primary disease=VZV vaccine is effective
Host response to alpha-herpesvirus infections (HSV-1, HSV-2, and VZV)
ages and issues with certain viruses?
Cell-mediated immune mechanisms play the major role in recovery
MHC class I and II proteins displaying viral antigens on surface of infected cell, activate T lymphocytes- directly kill the infected cell or secrete cytokines and chemokines to attract macrophages, etc.
Cell-mediated immune response varies with age: neonates: problems with HSVs; elderly: problems with VZV
herpes immune evasion effect on Ab's? interferons? MHC? latentcy effect for this?
HSV-1, HSV-2, and VZV envelope glycoproteins bind Fc domain of antibodies and complement components, blocking their ability to promote an antiviral response.
HSV proteins reduce type I interferon production and its downstream signaling
pathway
HSV proteins can prevent MHC class I and II proteins from being expressed on the surface of infected cells
Latency results in no expression of viral proteins and therefore no peptides for
MHC proteins to display
Usual Course of Herpes Simplex Virus Infection and Disease stages
acute disease
recovery
latency
recurrent disease
acute disease of Usual Course of Herpes Simplex due to exposure to? outcomes? viral replication where? spreads to?
facial or genital herpes, stomatitis, mucocutaneous lesions, or keratitis= localized
Exposure of skin, mucosa, or cornea to secretions containing virus
Replication of virus in epithelial cells, causing vescular mucocutaneous lesions, stomatitis, or keratitis
Spread to peripheral sensory or autonomic nerve endings and ganglia
HSV 1 often acquired when?
HSV-1 acquired very early in life (e.g. kissing)
2/3 of adults are Ab+
HSV 2 acquired how/when usually?
HSV-2 mostly transmitted by genital contact
uncommon before adolescence
1/5 of adults are Ab+
HSV 1 and 2 infections always symptomatic?
Most HSV-1 and HSV-2 infections are
asymptomatic
~1/3 of infections have recognizable symptoms
recovery of Usual Course of Herpes Simplex Virus Infection and Disease
Healing of lesions and establishment of latent
infections in neurons