PRION 2017 Deciphering Neurodegenerative Disorders...

PRION2017DecipheringNeurodegenerativeDisorders

Edinburgh23-26.05.17PRION2017wasthelatestoftheannualinternationalPrionDiseaseConferencesand,thisyear,tookplaceinEdinburgh,Scotland,over4daysfrom23rdto26thMay2017.OVERVIEWThesemeetingsareattendedbypeoplefrommanycountriesandmanydifferentdisciplinessuchas:proteinchemistry,genetics,clinicalneurology,epidemiology,publichealthandagriculture/animalmedicine.Thisyear,therewerearound350attendeesand,mostimportantly,membersoftheCJDInternationalAllianceweretheretopresentthehumansideofthestory.Thispresentationfromthepatient/familypointofviewisalwaysgreatlyappreciatedbytheresearchersandhelpstogiveadditionalmotivationtotheirworkinunderstandingthesediseases.ThosewhoarepersonallyaffectedbyCJDshouldtakeheartthatthereissuchaconcertedinternationaleffortinthisdifficultarea.Themeeting’ssubtitlereflectedthegrowinginterestintherelationshipbetweenpriondiseases(includingCJD)andother,morecommon,illnessessuchasAlzheimer’sDisease,Parkinson’sDiseaseandMotorNeuronDisease.Whateverthedifferencesbetweenthesediseases(inwhytheyoccurandhowtheyaffectpeople),theyallhaveaparticularkindofdiseasefeaturecalled‘neurodegeneration’.Thisisdifficulttodefinesuccinctlybut,inessence,inaneurodegenerativedisease,particulargroupsofneurons(nervecells)dysfunctionanddieassociatedwiththetissuedepositionofabnormallyfoldedprotein(inthecaseofpriondisease,itistheprionprotein).Researchersintothesedifferentdiseasesare,increasingly,lookingtoseehowtheirknowledgemaybehelpfultoeachother.Togiveabroadoverviewofthetopicscovered,themeetingprogrammewasdividedintothesemainareas:

MechanismsofProteinMisfoldingMechanismsofNeurodegenerationCurrentconcernsinPrionDiseaseDiseaseTransmissionandPathogenesisClinicalAspectsofPrionDiseaseDiagnostics/Therapeutics

ThemeetingopenedwithanaddressbytheChiefScientistfromtheScottishGovernmentHealthDirectorates,followedbytwodetailedreviewswhatweknowofpopulation,publichealth,cellularandmolecularaspectsofpriondiseases.ThesewerefollowedbySallyMagnusson’smovingpersonalaccountofhowdementiaaffectedhermotherandhowmusichadimprovedherqualityofhermother’slifeduringthattime.Itisimpossibletogivedetailsofallthemeetingpresentationsand,naturally,differentattendeeswouldprobablyselectdifferentonesasmostimportant-reflectingtheirparticularresearchinterests.Whatfollowsisaselectivesummary,withgeneralcommentsmorethanspecificdetail,designedtogiveanoverallflavouroftheconferenceand,hopefully,tohighlightthoseareasofmostinteresttofamilies.DISEASEPROCESSTherewerepresentationsofresearchintotheunderlyingmechanismsofprionandotherneurodegenerativediseases.Fivebroadaspectsstoodout:firstly,theimportanceofthe

synapseindisease,secondly,theselectiveinvolvementofneurons,thewaydiseasespreadsinthebrainandthemisfoldingofproteins.Interestingandimportantprogressisbeingmadeinalltheseareas.

• Neuronscommunicatewitheachotherviaspecialconnectionscalledsynapses.Itseemsthattheearliestphaseofneurodegenerativediseaseslikepriondiseaseprincipallyaffectthesynapsesandthereisevidencethat,atthisearlystage,thediseaseprocesscouldbereversible.

• Onefeatureofneurodegenerativediseaseisthatcertaintypesofneuronesappeartobeselectivelyvulnerableinanygivendisease(atthemostgenerallevel:motorneuronsinMotorNeuroneDisease,memoryneuronsinearlyAlzheimer’sDiseaseetc).Withindifferentpriondiseases,oneseesselectivevulnerabilityofneuronswithdifferentdistributionsofpathology.

• Itisknownthattheneurodegenerativeprocessspreadsinthebrainoverthediseasecourseand,asthisoccurs,differentsymptomsariseandthediseaseworsens.Thereisalotofworklookingatwhetherthisspreadingprocessin,say,Alzheimer’sdiseaseisbythesamemechanismasoccursindiseaseslikeCJD.

• Proteinsareverydynamiccreatures,constantlybeingmade,used,destroyedandreplaced.Weallmakenormalprionproteinthroughoutourlives.Weknowthat,inpriondisease,abnormallyfoldedprionproteincansomehowconvertnormalprionproteinintoanabnormalformleadingtoaccumulationofabnormalfoldedprotein.Theoriginalabnormalitycouldbeintroducedfromoutside(asintransmitted,infectious,formsofdisease).However,inapparentlyspontaneousdiseases,suchassporadicCJD,theoriginalabnormalitycouldbeasimple,random,mistakeinproteinmanufacture.Thesemistakesdooccur,butthereare‘qualitycontrol’mechanismsincellsthatshoulddealwiththeseerrors.Whysuch‘qualitycontrol’systemssometimesfailorwhetherthese‘qualitycontrol’processesthemselvescouldhavebadeffects,areinterestingresearchareas.

• Althoughneuronsarethecellsthataremostrelevantinthecauseofsymptoms,thereareothercellsinthebrainthatcouldwellbeimportantindiseaseprocesses.Therehasbeenalotofdevelopinginterestinthepotentialroleofthesenon-neuronalcells.

CHRONICWASTINGDISEASE(CWD)ThisisanimportantareaofanimalresearchinNorthAmericabutnowwithdirectimportanceforScandinavia,withthereportsofcasesinNorway,andpotentialimportanceforotherareasofEurope.ThedetailsoftheNorwegiancaseswerepresentedwithtwoapparentlyseparategeographicalareasbeingaffected.Thereisaplantoattempteliminationofthediseaseinoneoftheseaffectedareas.ExperimentaldetailswerepresentedillustratinghoweasilyCWDspreadsfromanimaltoanimalincludingbycontactwithordinarybodysecretions,environmentalcontaminationandwithevidenceofmaternaltransmission(frommothertounbornoffspring).ExperimentalevidenceofsuccessfultransmissionofCWDtoprimates(macaques)waspresented.Naturally,thereiscontinuingconcernastowhetherCWDcouldtransmittohumans.Thereiscurrently,noevidencethatthishasoccurred.Humandiseasesurveillancesystemsarelookingactivelytoseeifanysuchcaseseveroccur.OTHERNEURODEGERATIVEDISEASETherewereanumberofpresentationsondiseasesotherthanpriondiseaseandthepotentialrelationshipwithpriondisease.

Asselectiveexamples:• Howalpha-synuclein(akeyproteininthediseaseprocessofParkinson’sDisease)

interactswithprionproteinandmightaffectthepriondiseaseprocess.• Understandingtheroleofa-beta(akeyproteininAlzheimer’sDisease,AD)inAD.• HownormalprionproteinmightberelevantinAD.• HowstudiesofiatrogenicCJD(humangrowthhormoneandduramaterrelated)

haveproducedevidenceoftransmissionofa-betaproteinabnormalityalongsidethetransmissionofpriondisease.However,itmustbestressed,thereis,asofyet,noevidencethatADitselfhasbeentransmitted.

CURRENTCONCERNSINVARIANTCJDWeknowthatexposuretoBSEinfectioninfoodcanresultinsubclinicalinfectioninpeople(infectedbutwithnoevidenceofclinicaldisease).Thereareseveralquestionssurroundingthisespecially:howmanypeoplearesubclinicallyinfected?,aretheycapableoftransmittingdiseasetoothers?AndwilltheybecomeclinicallyillwithvariantCJD(vCJD)atsomepoint?TwopresentationsaddressedthesequestionsonthebasisofarecentUKstudy.InsubclinicalBSE/vCJD,tissuesliketheappendixmayshowabnormalprionproteindeposition.PreviousUKappendixtissuestudieshavesuggestedthat1:2000-1:4000ofthepopulationareinfected.However,despitethis,clinicalcasesofvCJDhavevirtuallydisappearedandtherehavebeenveryfewinstancesofhuman-to-humantransmissionandnonerecently.Therecentappendixstudycomparedresultsfromatimepresumedtopre-datesignificantBSEcases,atimeduringtheknownBSEexposureandatimepost-datingthepresumedBSEexposure.Theunexpectedresultswerethatpositivesampleswerefoundinall3periods.EithertheBSEexposureperiodwasnotaspresumedortheremaybesomeexplanationforthepositiveresultsotherthandietaryBSEexposure.GENETICSTherearealwaysgeneticaspectstoanydisease-varyingfromminorsusceptibilityeffects,throughmajorsusceptibilityeffectstodirectcausation(asininherited,geneticdisease).Thedirectroleofprionproteingenemutationingeneticpriondiseaseisclear.TheCodon-129variationintheprionproteingeneisalsowellunderstoodashavinganotableeffectinsusceptibilityandclinicaloutcomeinpriondiseases.However,itislikelythatthereareothergeneticinfluencesatworkinpriondiseases-evenifrelativelyweak.SomeothergeneticfactorshavebeenidentifiedinthepastforbothsporadicandvariantCJD.Inrecenttimes,therehavebeenmajoradvancesingenetictechnologythatallowsearchingthroughhugenumbersofgenestotrytoidentifythosethatmighthavesomecontributoryeffects,evenifsmall.Onepresentationdescribedtheresultsfromaverybiganddetailedstudythathadidentifiedsomepossiblenewgeneinfluences.Onepointofsuchworkisthat,ifrelevantgenescanbeidentified,itispossibletoexplorewhatthesegenesdoandtherebygainfurtherinsightsintothemechanismsofdisease.DIAGNOSTICSThereisnodoubtthatmajorimprovementsindiagnosisofpriondiseasehavetakenplaceovertheyears.However,thereiscontinuedresearchintoeasier,morereliableandsimplerdiagnostictests.Threepresentationsareworthyofnote:

• AnewbloodtesthasbeendevelopedthatisverysensitiveandspecificforvCJD(variantCJD).Importantly,inthisstudy,thetestdetectedabnormalityinsomebloodsamplestakeninapre-clinical(subclinicallyinfected)phaseoftheillness.Thisisthefirsttimethishasbeenshown.

• WorkondiagnosingCJDonskinbiopsywaspresented.Itwasalsoshownthatpotentialinfectivitycouldbefoundinsuchskinsamples,butonlyusingspecificexperimentaltechniques.Itshouldbeemphasisedthatthereisnoevidencethatthesediseasescanbenaturallytransmittedbyordinary,evenintimate,humancontact.

• Aninterestingpresentationdescribedatechniquefordetectingpriondiseaseusingfruitflies.Thismaywellbeofpotentialutilityanddoesnothavetheethical,timeorexpenseproblemsassociatedwiththeuseoflargeranimals.

TREATMENTManyoftheabovetopicscouldhaveimplicationsforpossibletherapies.However,thereweretwospecificpresentationsofpossibletherapies.

• Theuseoftypesofabnormal,butharmless,prionproteinthatmight‘block’theeffectofdisease-relatedabnormalprionprotein.

• Theuseofantibodiestonormalprionproteininordertostoptheprionproteinconversiondiseaseprocess.

CLOSINGTALKSThemeetingclosedwithtwotalks.Thefirstreviewedabnormalitiesoftheneuronalsynapsesinneurodegenerativedisease,especiallyinAD.Thesecondreviewedthemethodsusedtomodelneurodegenerativediseaseinexperimentalwork,highlightingtheutilityofusingculturedcellsinthelaboratory.Othersessionsofinterest:Cross-species transmissionofCWDprions.Dr.ChristinaSigurdsonpresentedanupdateonhergroup’sworkcharacterisinginteractionsbetweenprionparticlesfromdifferentspecies.Theabilityofprionsfromanimalsraisedforfoodtoinfectotherlivestockandevenhumans,asoccurredduringtheBSEepidemictowardstheendof the lastcentury, remainsacauseforconcern.Recentlyanewtypeofprion–causingChronicWastingDisease–hasappearedinpopulationsofEurasiandeerandDr.Sigurdson’sgrouphavebeeninvestigatinghowthisprionmight infectotherspecies.They foundthatprions indiseaseddeer relyonprions inthe recipient species being structurally similar for infection to takeplace, andwent on toidentify parts of the prion protein structure that might enhance infectivity or provideresistancetoinfection.Bycomparingstructures,theseresultswillproveusefulinprioritisingthemanagementof at-risk livestockandothernative species, and considering the furtherriskofhumansbecominginfectedbyeatingcontaminatedmeatsuchasvenisonorbeef.DetectionofprionsintheplasmaofpresymptomaticandsymptomaticpatientswithvariantCreutzfeldt-Jakob disease. Dr Chantal Fournier-Wirth presented results recently published(December2016).Herteam,workinginMontpellieratthe“EtablissementFrancaisduSang”(French institution forblood)establishedarobustmethodtodetect theagentresponsibleforBSE inbloodsamples. This isvery importantbecause,although thespreadofBSEhasbeen controlled by surveillance and feeding restrictions, it is estimated that millions ofpeople were exposed to BSE prions. A major concern is that some individuals might beinfectedbuthavenosymptoms.Iftheydonateblood,theymaytransmitinfectiontoothers.To date, prion diseases can only be diagnosed after death, by detection of altered prionproteins in thebrain. Thispaper is thereforevery important. Itnotonlyusesa very smallamountofbloodasstartingmaterial (0.5mL)butalsoallows todetectprions in thebloodbefore the appearance of the neurological symptoms (up to 31 months before). Thesefindingsmayhelp clinicians and researchers in their endeavour tobetter diagnose and/oridentifydrugsforpriondiseases.

Detection of Prion Seeds in Skins of Sporadic CJD Patients. Disease-causing prions arebelieved tobeconcentrated in the centralnervous system inmost formsofpriondiseaseotherthanvariantCJD.Indeed,spinalfluidandbraintissueexaminationsformthebedrockof diagnosis in prion disease. However, it is known that skin of infected animals such asmice,sheepandthemoreexotickuduareknowntoharbourprions,detectedbytraditionalmethods;prionswereonlydetectedintheskinofonesinglehumancaseofvariantCJD,butneverinsporadicCJD.WiththeadventofhighlysensitiveandspecifictechnologyknownasReal-Time Quaking-induce Conversion assay (RT-QuIC), scientists from Case WesternUniversity inCleveland,Ohiosetout tosee ifprionseedscanbedetected insporadicCJDpatients.NotonlydidtheymanagetofindprionseedsintheskinofsporadicCJDpatients,butexperimentalmiceinjectedwithskinpreparationsfromthesepatientscausedthemiceto come down with CJD; the traditional methods of detecting prions returned negativeresults.TheseobservationsraisethepossibilityusingskinbiopsyasawayofdiagnosingCJD,andalsotheneedtore-examinethedistributionofprionsinhumantissuesotherthanthecentralnervoussystem.Detection of mammalian prions by PrP transgenic Drosophila. Dr Raymond Bujdoso,CambridgeUniversity.AlthoughvariantCJD(vCJD)affectedfewerthan200peopleintheUK,itremainsamajorpublichealthconcern;studieshavesuggestedthatupto1in2000peoplemaybesilentcarriersofinfection.It’sthereforecrucialtohavearapidmethodtodetectandmeasure infectious prions in tissue specimens or bodily fluids, known as a bioassay.Currently,thegoldstandardmethodinvolvesinfectingmicewiththematerialtobetested,andmeasuringthetime it takesthemtobecomeinfected.Whilstthis isaveryrobustandeffective approach, it can take months or even years. A group led by Dr Bujdoso isattemptingtoestablishasimilarbioassayinfruitflies,astheyreproduceandgrowquickerthanmice.Byreplacingthefly’sprionproteingenewiththatofacow,theyreportedforthefirst time that they could infect flies with prions that cause Bovine SpongiformEncephalopathy (BSE) – the type of prion disease that was transmitted to humans andcausedvCJD.Although thiswork isatanearly stage, theyhope to try similarexperimentswithvariantCJD.Ifsuccessful,thismaybeanalternative,morerapidapproachtoidentifyinginfection with variant CJD in days or weeks; however, whether this is quick and efficientenoughtousetowidelyscreenbloodsamplesremainstobeseen.Muskelinproteininpriondisease.Dr.Krasemann’steaminvestigatedtheroleoftheproteinmuskelininpriondisease.Muskeliniswhatiscalledan“intracellulartraffickingfactor”thismeansthatisworkstomovethingsaroundincells.Thismightincludemovementofprionsandnormalprionprotein.Thegroupshowedthatnervecellsmicethatdon’thavemuskelin“knock out (KO) mice” display impaired transport of prion protein. Prion infection inmuskelin knockout mice had a shorter incubation time. These findings highlight theimportanceofmovementofprionproteinsinpriondiseaseandtheroleofproteinmuskelin.AspecialthankstoRichardKnightandSimonMeadfortheirsummaryofthisevent.