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67 Cards in this Set
- Front
- Back
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what virus family is varicella zoster virus a part of?
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herpesviridae
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what kind of vaccines are given for VZV?
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1. approved in 1995: prevents both acute and latent infections for previously uninfected ppl
2. new vaccine, 2006: recommended for previously infected, older ppl to prevent shingles. |
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Poxviruses
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largest and most complex viruses
associated w/ skin lesions |
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what's the most serious poxvirus?
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variola
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what does variola cause?
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smallpox
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what was the first virus to be declared eradicated by the WHO in 1979?
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small pox
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what was the first disease controlled by immunization
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smallpox
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what's vaccinia?
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poxvirus descended from Jenner's original vaccine against smallpox
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which poxviruses are human viruses rather than transmitted from animals?
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smallpox and molluscum contagiosum
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what's the structure of VZV?
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same as all Herpes:
1. enveloped, icosahedral 2. tegument 3. No viral pol in virion 4. sensitive to inactivation 5. ds, linear DNA 6. large, but smallest herpesvirus 7. encodes >100 proteins, >35 in virion |
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what are the steps of VZV replication?
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1. bind cell R, envelope fuses w/ cell membrane
2. nucleocapsid, viral proteins in tegument released into cytopl 3. nucleocapsid to nuc.memb. and genome ejected into nuc 4. genome tsc by host DdRpol and replic by vDNA pol in cell nucleus 5. viral proteins synth in cytopl and transp to nuc for assembly 6. capsids form, genome inserted, envelope at nuc memb by "budding" 7. virions accum. in golgi, modification of envelope 8. release by exocytosis/lysis |
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what's the difference in gene expression in lytic vs. latent VZV infections?
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different genes expressed
genome NOT replicated during latentcy |
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what does immediate early gene expression produce in VZV?
where? |
viral proteins for viral gene replication
include mRNA and tsc factors for more viral RNA viral proteins synth in cytoplasm and transported to nucleus for assembly |
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what does early gene expression produce in VZV?
where? |
more tsc factors and enzymes like:
viral DNA pol thymidine kinase in cell nucleus |
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how is the VZV genome replicated?
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by viral DNA pol in the cell nucleus
involves many viral proteins (good Tx targets) |
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what does late gene expression produce in VZV? When does this take place?
where? |
after genome replication, mainly structural proteins produced
in the cytoplasm, then transported to nucleus for viral assembly |
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where do VZV virions accumulate in the cell?
what happens there? |
accumulate in Golgi apparatus
viral envelope may be modified there |
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how are VZV virions released?
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exocytosis and lysis
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where is VZV found?
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worldwide, no seasonal variation
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How contagious and when is VZV contagious?
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very contagious before and during Sx
90% attack rate |
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how is VZV transmitted?
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by respiratory route or contact w/ skin vesicles (think chicken pox)
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who gets VZV infections?
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everyone:
common childhood illness (age 5-9 yo)--textbook chickenpox teens/adults at risk for more severe form, pneumonia immunocompromised/newborns: at risk of life threatening complications of chickenpox |
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what are some life threatening complications of chicken pox seen in newborns, immunocompromised?
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pneumonia
encephalitis progressive disseminated varicella |
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whats a consequence of severe adult chickenpox?
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pneumonia
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what kind of recurrent dz are elderly/immunocompromised at risk for who have been previously infected w/ chickenpox?
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herpes zoster (shingles)
post-herpetic neuralgia |
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where's the primary replication site of VZV?
How does it spread? |
upper respiratory tract mucosa
lymphatics, blood (primary viremia) and targets reticuloendothelial cells: forms syncytia and can spread cell to cell |
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what is primary viremia of VZV?
what are the Sx? |
when virus spreading through blood, lymph to reticuloendothelial cells
prodromal symptoms |
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what is secondary viremia of VZV?
Sx? |
spread of virus throughout body to the skin
vesicular rash in successive crops fever, systemic sx same time as rash higher viral titer than primary b/c multiplication in multiple sites |
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where does VZV become latent?
what is the replication rate? |
dorsal root ganglia
doesn't reproduce |
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when does VZV reactivate?
what does it cause? |
when CMI reduced by age, stress, immunosuppresion
(about 10-20%) shingles or post-herpetic neuralgia |
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how is the rash of chickenpox different from smallpox?
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"non-synchronized":
macule to papule to vesicle to pustule to crust all seen at same time in small pox, the rash starts on the trunk and is synchronized at each stage. |
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whats the pathology of VZV reactivation?
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virus produced in neurons where it was latent, travel along neural pathway to skin
produces rash in dermatomal distribution can be very painful lasting for weeks (shingles) or months (post herpetic neuralgia) |
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what is the effect of humoral response on VZV
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can limit viremia
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what is necessary to resolve chickenpox?
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CMI (humoral responses only limit viremia)
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what's the clinical course of chickenpox?
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incubation 1-2 wks
prodromal Sx: fever, malaise rash appears trunk 1st then on head and extremities itching can be severe |
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is the rash associated w/ chickenpox only on the skin?
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no, it can occur in the mouth, conjunctiva and vagina
usually assoc w/ older individuals and more sever dz |
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what's the problem w/ giving aspirin for chickenpox (VZV) or influenza B virus in kids?
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reye's syndrome
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what are some complications in normal hosts with chickenpox
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adults: pnuemonia (hepatitis, encephalitis)
bacterial infections secondary to scratching |
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how is the dx of chickenpox made?
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usually clinical
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what test would be used for presumptive dx of chickenpox?
how is it done? |
Tzanck smear
detect viral Ag's in skin scrapings, or specimen inoculated in cell culture |
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how is a presumptive lab test (tzanck smear) for VZV confirmed?
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clinical dg, PCR, rise in Ab titer
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what's the tx for VZV?
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1. none for mild dz
2. valacyclovir limits duration and severity of Sx 3. varicella zoster Ig (VZIG) can protect immunosuppressed pts from severe dz, but not during active case |
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what can be done to protect immunocompromised pts from severe VZV infection?
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VZIG, but cant be given during active infection
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what are some classic childhood rashes? which are caused by herpesviruses?
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roseola (herpes)
chickenpox (herpes) measles parvovirus fifth disease |
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can chickenpox be serious?
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yes, about 12,000 ppl/yr hospitalized in US
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what's the vaccine for VZV?
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1. live, attenuated (Varivax) given to kids >1 yo
induces humoral and CMI response cannot prevent zoster in previously infected avoid giving to immunocompromised or pregnant limited protection time... 2. higher dose booster of live, attenuated vaccine (2006) for ppl >60 yo to prevent shingles |
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does poxvirus have an envelope?
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yes, but its not required for infectivity
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how tough is poxvirus?
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even though it has an envelope, its virion's still highly resistant to environment, drying, disinfectants
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what does a poxvirus look like?
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pretty large, with complex ovoid symmetry (Brick shaped)
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what surrounds the core of a poxvirus?
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an outer membrane and an envelope (not req'd for infection)
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what's the viral genome of poxvirus like?
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huge
ds, linear DNA |
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what's the only known DNA virus that replicates in the cytoplasm?
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poxviruses
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how do poxviruses replicate
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1. bind cell R and enter by fusion
2. all tsc enzymes in virion core 3. synthesize viral DNApol 4. after DNA replicates, assembly takes place in cytoplasmic factories 5. complex process to acquire an envelope 6. some bud, most through lysis |
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what are lateral bodies?
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in core of poxvirus, may contain tsc factors
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why is pox virus the "exception virus"?
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1. has envelope but still resistant and doesn't need it for infection
2. replicates in the CYTOPLASM contains DNA dependent RNA pol and DNA dep DNA pol |
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how is poxvirus transmitted?
source? when is it infectious? |
contact w/ active case, usually by humans (molloscum contagiosum) or farm animals (orf, monkeypox)
only active case, not infectious during incubation period |
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what virus causes small pox
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variola
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what are some strains of smallpox you can get from cows, sheep, goats?
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orf
monkeypox |
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what's the pathogenesis of smallpox?
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primary trans: close contact (respiratory aerosol, contact w/ skin lesion/fomite like bedding)
incubation 1-2 weeks--infect URT and local LNs followed by primary viremia then secondary targets followed by secondary viremia (characteristic rash) |
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what are the secondary targets infected in smallpox?
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liver, spleen, marrow, lungs
this is followed by secondary viremia |
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what does secondary viremia of pox virus lead to?
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infection of the skin and the rash
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upon recovery from smallpox, where does the virus remain latent?
what's the immunity to re-infection? |
it doesn't, the virus is eliminated from the body
lifelong immunity |
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how are other poxviruses transmitted? what kind of disease do they cause?
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trans by direct contact with lesions.
virus remains localized. |
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which type of immunity protects from small pox infection?
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both CMI and humoral important for infection resolution
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what are the clinical manifestations of smallpox?
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day 4- asymptomatic viremia
day 8- 1st sign of fever day 12-14 - rise in fever, aching pains, prostration day 16-18 - papular rash develops, spreads to extremities, becomes vesicular, pustular (2 wks), crusts |
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what's the mortality associated with variola major (smallpox)
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20-50% mortality
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what kind of rash is seen in smallpox?
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synchronized:
papular rash develops on face and spreads to extremities becomes vesicular, pustular (2 weeks) then crusts rash appear about 16-18 days after infection ALL infections symptomatic |
