InfectiousmononucleosisisanacutelymphoproliferativediseasethatiscommoninchildrenandyoungadultsandiscausedbytheEpstein-Barrvirus(EBV).TheEBVisoneoftheherpesviruses4(gamma).
Characteristicclinicalfeaturesinclude:

1.fever,sorethroat,andlymhadenopathy
2.anassociatedabsolutelymphocytosisgreaterthan50%,containingatleast10%ofatypicallymphocytesintheperipheralblood
3.developmentoftransientheterophilandpersistentantibodyresponsesagainstEBV
4.abnormalliverfunctiontests

4%ofinfectedyoungadultsshowanictericmanifestationand50%havesplenomegaly.Inaddition,EBVisimplicatedinnasopharyngealcarcinoma,BurkittlymphomaandHodgkin´sdisease.
Aninfectiousmononucleosissimilarsyndromecanbecausedbycytomegalovirus,toxoplasmosisandotherviralinfection;differentialdiagnosisdependsonlaboratoryresults,withonlyEBVstimulatingtheproductionofheterophilantibodies.
EBVispresentinsalivaofpatientswithacuteinfectiousmononucleosis,andexcretionofthevirusfromtheoropharynx,whichpersistsforseveralmonthsaftertheoutbreakofthedisease,isoneofthemajorwaysofvirustransmission.InfectedpersonskeeptheEpstein-Barrvirusforlifetime,butaremostlyasymptomatic.Indevelopingcountriespracticallythewholepopulationisinfected;inwesterncountriesprevalenceisabout80–90%.Transmission,possIBLyfromthemother,alreadytakesplaceatchild’sageandmainlyviasaliva.
Ofgreatimportancefordiagnosisisthedetectionofanincreaseinrelativeandabsolutenumberoflymphocytesandatypicallymphocytes.Duringthedisease50–60%ofleukocytesintheperipheralbloodcanbelymphaticcells,ofwhichnormally10%areatypicallymphocytes.Inaddition,abnormalliverfunctiontestsandhightitersofheterophilantibodiesareseen.
SEROlogicaltestslikeELISAareveryusefulforthedetectionofanti-EBVantibodies,especiallyifheterophilantibodiesareabsent.ThedifferentstagesofanEBVinfection(acute,reactivated,past)arecharacterizedbytheappearanceofdifferentantibodies(IgA,IgG,IgM)againstdifferentviralantigens(viruscapsidantigen=VCA,earlyantigen=EAandEpstein-Barrvirusnuclearantigen=EBNA).
ThesixparametersproducedbyIBL(VCAIgA/IgG/IgM,EAIgA/IgGundEBNAIgG)enabletodetectanddifferentiateallstagesofanEBVinfection.AwelldirectedselectionofantigensforIBLEBVELISAsresultsinanextraordinarysensitivityandspecificityforthediagnosisofacutediseasesandforthedetectionofpastinfections.
TheassaysforthedetectionsofantibodiesagainstEAandEBNAusehighlyspecificrecombinantantigens–EAp54antigenexpressedinE.coliandEBNA-1p72antigenexpressedinSf9cells;affinitypurifiedVCAgp125fromP3HR1cellsisresponsibleforthehighsensitivityoftheVCAELISAs.
Thisselectionofantigenstogetherwithapurposefulregulationofassaycharacteristicsresultsinacleardistinctionbetweenpositiveandnegativesamples,i.e.asmallgreyzone.
TheveryhighsensitivityoftheVCAIgAassayandthe100%specificityoftheEAIgAELISAareofparticularimportance;thecombinationofthesetwoassaysallowsthecorrectdetectionofreactivatedinfectionswithextremelyhighreliABIlity.
The?-captureprincipleappliedfortheVCAIgMassayresultsinahigherspecificitycomparedtoIgMELISAsfollowingthesandwichprinciple,i.e.falsepositiveresultsareminimized.
InformationaboutantibodycombinationsthataretypicalforthedifferentstagesofaninfectionisgiveninchapterPERFORMANCE.