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Microbiology- Virology
Herpesvirus: EBV, CMV, HHV6, HHV8 (T Pierce)
23
Medical
Professional
11/10/2009

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Cards

Term
EBV: cellular and genetic characteristics
Definition
  • gamma herpesvirus
  • DNA virus, icosahedra capsid, lipid envelope
  • envelop glycoproteins that:
    • mediate attachement
    • important for making vaccine
  • latency in B lymphocytes
    • circular viral DNA as episome into nucleus
    • expression of specific viral proteins leads to cellular transformation
      • latent infection membrane proteins
Term
EBV: epidemiology
Definition
  • developing countries: childhood (oncogenic potential: Burkett's lymphoma)
  • developed countries: adolescence, early adulthood
    • 90% of adults in US have serum Ab
  • EBV excretion in oropharyngeal secretions
    • almost always in immunocompromised hosts
    • sometimes in healthy adults
  • "close" personal contact
Term
EBV: pathogenesis
Definition
  1. EBV multiplies in pharyngeal lymphoid tissue and possibly oropharyngeal epithelial cells
  2. dissemination throughout the lymphoreticular system (ex: spleen, lymph nodes, liver)
  3. EBV latency and reactivation leads to periodic asymptomatic shedding
  4. EBV cause transformation of B lymphocytes
    • cytotoxic T lymphocytes or "atypical lymphocytes" directed against infected B cells can be seen on peripheral blood film
Term
EBV: clinical presentation
Definition
  • asymptomatic
  • infectious mononucleosis
  • sore throat, fever, lymphadenopathy
  • tonsillar enlargement with exudate
  • palatal petechiae at junction of hard and soft palate
  • cervical lymphadenopathy
  • splenomegaly and hepatomegaly
    • splenic trauma may result in splenic rupture
  • rash to ampicillin
Term
EBV: complications and tx for them
Definition
  • hemolytic anemia
  • splenic rupture, usually after trauma
  • neurologic disease

tx for complication is corticosteroids (but no effective tx for EBV)

Term
EBV: malignancies its associated with
Definition
  • B cell lymphomas (remember, EBV infects B cells)
    • Hodgkin's lymphoma
    • Burkitt's lymphoma
    • CNS lymphoma
  • lymphoproliferative syndromes
  • nasopharyngeal carcinoma
Term
EBV: dx
Definition
  • atypical lymphocytosis
    • large lymphocyte with basophilic vacuolated cytoplasm, lobulated eccentric nuclei
  • thrombocytopenia common
  • mild elevation in transaminases
  • differential dx
    • CMV
    • HIV
    • toxoplasmosis
Term
EBV: dx
Definition
  • monospot (heterophile Ab's)
    • latex agglutination of horse RBC's
    • positive in most cases of acute mononucleus
  • specific Ab's (IgM- within first 2 months; IgG- last for years)
    • viral capsid Ag (VCA)- Ig's bind to this
    • early Ag (EA)
    • Epstein Barr nuclear Ag (EBNA)- found in latent infection
  • EBV DNA PCR
Term
Patients who tend to undergo reactivation of EBV
Definition
usually only happens if you are immunocompromised
Term
CMV: cellular and genetic characteristics
Definition
  • beta herpesvirus
  • largest human virus: linear DNA, icosahedra capsid, lipid envelope
  • causes increase size of infected cells (cytomegaly)
  • encodes proteins that prevent MHC I molecules from reaching cell surface
    • downregulates cytotoxic CD8 response
Term
CMV: transmission
Definition
  • contact with body fluids: shed in
    • saliva
    • urine
    • semen
  • many adults seropositive
  • sexual contact
  • contaminated blood products
  • perinatal- intrapartum, at delivery, via breast milk
  • day care settins
Term
CMV: immunocompetent host clinical syndrome
Definition
  • asymptomatic
  • mononucleosis
  • congenital CMV
Term
CMV: immunocompromised host clinical syndromes
Definition
  • retinitis
  • pneumonitis
  • GI: colitis, esophagitis
  • CNS: encephalitis, myelitis
Term
CMV: retinitis
Definition
  • primarily in patients with HIV infection
  • necrotizing chorioretinitis: peripheral or central (half is bilateral)
  • irregular sheathing of bv's
  • later development of scattered white granular lesions with hemorrhage
  • several antiviral have been used for tx (ganciclovir, foscarnet, cidofovir)
Term
CMV: congenital syndrome symptoms and transmission
Definition
  • several manifestations involving multiple organ systems
    • jaundice
    • hepatosplenomegaly
    • petechial rash
    • microcephaly
    • low birth rate
    • developmental delay
    • motor disability
    • chorioretinitis
    • cerebral calcifications
  • intrapartum transmission
    • primary infection during pregnancy
    • rarely, infection prior to pregnancy
Term
CMV: dx
Definition
  • tissue: cytoplasmic and nuclear inclusions ("owl's eye" inclusion)
    • aggregates of CMV nucleoprotein cores
  • serology: IgM/IgG (usually heterophilic negative)
  • culture
    • shell vial technology
    • assay supernatant for early Ag, more rapid detection
  • CMV DNA PCR
Term
HHV6: cellular and genetic characteristics
Definition
  • beta herpesvirus (some homology with CMV and HHV7)
  • can infect multiple cell types
    • T cells
    • B cells
    • NK cells
    • epitheial cells
    • macrophages
    • glial cells
  • detect Ab in 70% of infants 12 months old and 90% in 24 months
  • 80% of blood donors are seropositive
Term
HHV6: epidemiology
Definition
  • mainly in kids
  • usually in spring/fall
  • spread by contacts with saliva
Term
HHV6: clinical manifestation
Definition
  • roseola infantum (exanthem subitum: 6th disease) in some cases
  • usually benign illness of children

 

Term
HHV6: roseola infantum (clinical characteristics)
Definition
  • incubation period: 10 days
  • abrupt onset high fever with well appearance, suboccipital adenopathy, red throat
  • abrupt disappearance of fever with onset of macular rash
  • drop in WBC prior to rash (may have atypical lymphocytes)
  • duration: 6 days
  • mononucleosis like illness in adults
Term
HHV6: complication, tx, dx
Definition
  • complication
    • usually self limited, mild
    • febrile seizures, rare encephalitis
  • dx: serologic testing (IgG/IgM)
  • tx: usually not indicated unless immunocompromised (mostly investigational)
Term
HHV8: genetic and cellular characteristics
Definition
  • gamma herpesvirus
    • indistinguishable from other herpesviruses on EM
  • also called Kaposi's sarcoma associated herpesvirus (KSHV)
  • attach to heparan sulfate, integrin alpha 3 and beta 1
  • target tissues
    • endothelial or spindle cells (Kaposi's sarcoma)
    • B lymphocytes: lymphomas
  • latency: lymphocytes, endothelial cells
Term
HHV8: transmission, clinical associations
Definition
  • transmission likely via sexual contact
  • associated with malignancy
    • Kaposi's sarcoma
      • vascular tumors usually associated with HIV
      • 90% of KS lesions positive for HHV8 DNA or proteins by in situ hybridization
      • seen in HIV associated KS, African variety, those associated with transplantation
    • Castleman's disease- focal or multicentric lymphoma
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