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Zikacaninfectadultbraincells,notjustfetalcells,studysuggests ByBradyDennisAugust18at12:00PM ThemoreresearcherslearnabouttheZikavirus,theworseitseems. Agrowingbodyofresearchhasestablishedthattheviruscancauseseverebirth defects—mostnotablymicrocephaly,aconditioncharacterizedbyanabnormally smallheadandoftenincompletebraindevelopment.Thevirusalsohasbeenlinked tocasesofGuillain-Barresyndromeinadults,arareautoimmunedisorderthatcan resultinparalysisandevendeath. Now,inastudyinmice,researchershavefoundevidencethatsuggestsadultbrain cellscriticaltolearningandmemoryalsomightbesusceptibletotheZikavirus. "Thiswaskindofasurprise,"JosephGleeson,aprofessoratRockefeller Universityandoneoftheco-authorsofthestudypublishedThursdayinthejournal CellStemCell,saidinaninterview."WethinkofZikahealthconcernsbeinglimited mostlytopregnantwomen." [ForZika-infectedpregnancies,microcephalyriskmaybeashighas13percent] Inadevelopingfetus,thebrainismadeprimarilyof"neuralprogenitor"cells,atype ofstemcell.Researchersbelievethesecellsareespeciallysusceptibletoinfectionby theZikavirus,whichcanhindertheirdevelopmentanddisruptbraingrowth.Most adultneuronsarebelievedtoberesistanttoZika,whichcouldexplainwhyadults seemlessatriskfromthevirus'smostdevastatingeffects. Butsomeneuralprogenitorcellsremaininadults,wheretheyreplenishthebrain's neuronsoverthecourseofalifetime.Thesepocketsofstemcellsarevitalfor learningandmemory.GleesonandhiscolleaguessuspectedthatifZikacaninfect fetalneuralprogenitorcells,thevirusmighthavethesameabilitytoinfectadult neuralprogenitorcells.That'spreciselywhattheyfound. "Weaskedwhether[thesecells]werevulnerabletoZikainthesamewaythefetal brainis,"Glessonsaid."Theanswerisdefinitelyyes." Gleesonisthefirsttoadmitthatthefindingsrepresentonlyaninitialstepin discoveringwhetherZikacanendangeradulthumanbraincells.Forstarters,the studywasconductedonlyinmice,andonlyatasinglepointintime. Moreresearchwillbenecessarytoseewhethertheresultsofthemousemodel translatestohumans,andwhetherthedamagetoadultbraincellscancauselongtermneurologicaldamageoraffectbehavior. ButtheinitialfindingssuggestthattheZikavirus,whichhasspreadtotheUnited Statesandmorethan60othercountriesoverthepastyear,maynotbeas innocuousasitseemsforadults,mostofwhomneverrealizetheyhavebeen infected.Researchersfoundthatinfectedmicehadmorecelldeathintheirbrains andreducedgenerationofnewneurons,whichiskeytolearningandmemory.The possibleconsequencesofdamagedneuralprogenitorcellsinhumanswouldinclude cognitiveproblemsandahigherlikelihoodforconditionssuchasdepressionand Alzheimer’sdisease. [Obamaadministrationtoshift$81milliontofightZika] “Zikacanclearlyenterthebrainofadultsandcanwreakhavoc,”SujanShresta, anotherstudyco-authorandaprofessorattheLaJollaInstituteofAllergyand Immunology,saidinastatement.“Butit’sacomplexdisease—it’scatastrophicfor earlybraindevelopment,yetthemajorityofadultswhoareinfectedwithZikararely showdetectablesymptoms.Itseffectontheadultbrainmaybemoresubtle,and nowweknowwhattolookfor.” WilliamSchaffner,aninfectiousdiseaseexpertatVanderbiltUniversityMedical Center,agreedThursdaythatthefindingsarepreliminary.Buthealsocalledit troubling. "Here'sthedeal—themorewe'velearnedabouttheZikavirus,thenastieritis," saidSchaffner,whowasnotinvolvedinthestudy.Hesaidscientistshavehad concernsallalongaboutZika'sabilitytodamagethebrain,butuntilnowthe worrieshavefocusedmostlyonthedevelopingbrain."Thismousestudywill increaseouranxiety....It'sanadditionalpotentialwaythatthisviruscancause humanillness." That'sapossibilitythatdemandsfurtherexamination,hesaid,giventhehundreds ofthousandsofpeoplealreadyinfectedbyZika—anumberthatcontinuestogrow daily. "Ourattention,quiteunderstandably,hasbeendevotedtopregnantwomenand newborns,andpreventingthoseinfections,"Schaffnersaid."Thismousestudywill tellinvestigatorsthat,inadditiontopregnantwomen,youhavetoestablishsome studiesinolderchildrenandadultsaswell." Gleesonagreed."Wedon'twanttohavethisbeapanic.Zika,forthemostpart,isa benignconditioninhealthyhumans,"hesaid."Butwealsoneedtolookatthe potentialconsequencesinacarefulway."
