Medical Microbiology

DNAViruses 425

— EBNA(Epstein-Barrnuclearantigen).AntibodiestoEBNAarenotpro-

duceduntiltwotofourweeksafterdiseasemanifestation,thenpersist

forlife.

ChronicmononucleosisischaracterizedbyantibodiestoVCAandEA.

Thediagnosticproceduresinlymphoproliferativediseases(seeabove)in-

volvehistologyandcellularimmunotyping.

Epidemiology,prevention,andtherapy.EBVisexcretedinsalivaandpha-

ryngealsecretionsandistransmittedbyclosecontact(“kissingdisease”).As

withallherpesvirusesthelevelofgeneralizedcontaminationishigh,with

theprocessbeginninginchildhoodandcontinuingthroughoutadolescence.

Neitherimmunoprophylacticnorchemoprophylacticmeasureshavebeen

developedasyet.Lymphoproliferativediseasesinvolvingviralreplication

canbetreatedwithacyclovirandganciclovir.

HumanHerpesvirus(HHV) 6

Pathogen,pathogenesis,clinicalpicture.HHV-6wasisolatedin 1986 in

patientssufferingfromlymphoproliferativediseasesandAIDS.Thevirus

showsT-celltropismandisbiologicallyrelatedtothecytomegalovirus.

HHV-6existsintwovariants,HHV-6AandHHV-6B.Thepathogenicimplica-

tionsoftheirreactivationhavenotyetbeendescribed.

HHV-6Bisthecausalpathogeninexanthemasubitum(roseolainfantum),

adiseasethatisnearlyalwaysharmless,characterizedbysuddenonsetwith

highfeverandmanifestsasatypicalexantheminsmallchildren.Reportsof

HHV-6-causedillnessinadultsarerareandtheclinicalpicturesdescribed

resemblemononucleosis(EBV-negativemononucleosis).Apparently,how-

ever,thisviruscanalsocausesevereinfectionsinbonemarrowtransplant

patients (pulmonaryandencephalitic infections).HHV-6Ahas notyet

beenconvincinglyimplicatedinanyclinicaldisease.

Diagnosisandepidemiology.HHV-6canbeculturedinstimulatedumbilical

lymphocytes.Potentiallyusefuldiagnostictoolsincludeantibodyassayand

PCR.

GeneralizedcontaminationwithHHV 6 beginsinearlychildhood,even-

tuallyreachinglevelsexceeding 90 %intheadultpopulation.Thevirusper-

sistsinlatentforminthesalivarygland,sothatmother-to-childtransmission

ismostlikelytobeinsaliva.

HumanHerpesvirus(HHV) 8

Pathogen,clinicalpicture.HHV 8 hasrecentlybeenidentifiedasadecisive

cofactorininductionofKaposisarcoma.Theclassic,sporadicformofthis

malignancywasdescribedin 1872 intheMediterraneanarea.Italsooccurs

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Kayser, Medical Microbiology © 2005 Thieme