Medical Microbiology

DNAViruses 433

ChronichepatitisB

DevelopmentofachronichepatitisBinfectionisrevealedbyachangedantigen-

antibodyprofile:thetwoantigensHBsandHBc(andraisedtransaminases)persist

foroversixmonths,wherebyantibodiestoHBeandHBsarenotproduced.Asub-

sequent“lateseroconversion”ofHBeantigentoanti-HBeantibodiessupportsa

betterprognosis.Thoroughclarificationofchroniccasesmustincludeeither

immunohistologicaltestingforHBVantigensinliverbiopsiesorPCRtestingfor

thepresenceofviralDNA,andthusDaneparticles,inpatientserum.

Epidemiologyandprevention.HumansarethesolereservoirofHBV.Trans-

missionisparenteral,eitherwithbloodorbodyfluidscontainingHBV(sexual

intercourse)thatcomeintocontactwithmucosa,lesions,ormicrolesionsin

theskin.Intransmissionbyblood,thetiniestamountscontaminatingsyringe

needles,ear-piercingneedles,tattooinginstruments,etc.sufficetoproduce

aninfection.HepatitisBinfectionsfrombloodtransfusionshavebeengreatly

reducedbythoroughscreeningofblooddonorsforHBsantigens,despite

whichpatientsreceivingmultipletransfusionsordialysisremainahigh-

riskgroup.

Anotherhigh-riskgroupincludesallhealthcareworkerswithregular

bloodcontact.Allbloodsamplesmustbeconsideredpotentiallyinfectious

andhandledonlywithdisposablegloves.Addictswhoinjectdrugswithnee-

dlesarealsoobviouslyexposedtoaveryhighlevelofrisk.

SincenoeffectivechemotherapyagainstHBVhasbeendevelopedtodate,

theWHOrecommendsgeneralhepatitisBprophylaxisintheformofactive

immunizationwithHBsantigen.Inresponsetoasuddenhigh-levelinfection

risk(accidentalinoculationwithinfectiousmaterial),personswhoseim-

munestatusisuncertainshouldalsobepassivelyimmunizedwithhuman

anti-HBsantiserum—ifpossiblewithinhoursofpathogencontact.

IthasnotyetprovedfeasibletogrowHBVinvitro.Theantigenusedin

vaccinationscanbeisolatedfromhumanblood.FearofAIDSinfections

hasresultedinemotionallybased,unjustifiablerejectionofthisvaccine.

Analternativevaccineisnowavailablebasedondevelopmentsingeneticen-

gineering:theHBsantigencannowbesynthesizedbyayeastfungus.

Prevention:hepatitisBboostervaccines.Periodicboostershots,especially

forpersonsathighrisk,wererecommendedforsometimetomaintainsuffi-

cientimmuneprotection.However,sinceallsuccessfullyvaccinatedpersons

buildupimmunityrapidlyfollowingrenewedcontactwiththepathogen

(“immunologicalmemory,”seep. 94 ),thisrecommendationhasbeenre-

placedinanumberofcountriesbythefollowingscheme:

Followingimmunizationontheclassicmodel(0, 1 ,and 6 months),the

anti-HBsantibodytiterismeasuredwithinonetothreemonths.Responders

(titer 100 IU/l)requirenobooster.Inhyporespondersandnonresponders(ti-

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Kayser, Medical Microbiology © 2005 Thieme