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Vaccine
jo u rn al h om ep a g e :w w w . e l s e v i e r . c o m / l o c a t e / v a c c i n e
Subcutaneous
inverse
vaccination
with
PLGA
particles
loaded
with
a
MOG
peptide
and
IL-10
decreases
the
severity
of
experimental
autoimmune
encephalomyelitis
Giuseppe
Cappellano
a,∗,
Abiy
Demeke
Woldetsadik
a,
Elisabetta
Orilieri
a,
Yogesh
Shivakumar
a,
Manuela
Rizzi
c,
Fabio
Carniato
d,
Casimiro
Luca
Gigliotti
a,
Elena
Boggio
a,
Nausicaa
Clemente
a,
Cristoforo
Comi
b,
Chiara
Dianzani
e,
Renzo
Boldorini
a,
Annalisa
Chiocchetti
a,
Filippo
Renò
c,
Umberto
Dianzani
aaIRCADandDepartmentofHealthSciences,“A.Avogadro”,UniversityofEasternPiedmont“A.Avogadro”,viaSolaroli17,Novara,28100,Italy
bIRCADandDepartmentofTranslationalMedicine,SectionofNeurology,“A.Avogadro”,UniversityofEasternPiedmont“A.Avogadro”,
viaSolaroli17,Novara,28100,Italy
cInnovativeResearchLaboratoryforWoundHealing,DepartmentofHealthSciences,UniversityofEasternPiedmont“A.Avogadro”,
viaSolaroli17,28100Novara,Italy
dDepartmentofScienceandTechnology,UniversityofEasternPiedmont“A.Avogadro”,vialeTeresaMichel11,15121Italy
eDepartmentofDrugScienceandTechnology,UniversityofTurin,viaPietroGiuria9,10125Torino,Italy
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:
Received24February2014
Receivedinrevisedform19June2014
Accepted8August2014
Availableonline20August2014
Keywords: PLGA Tolerogenicvaccine TREG Interleukin-10
a
b
s
t
r
a
c
t
“Inversevaccination”referstoantigen-specifictolerogenicimmunizationtreatmentsthatarecapable ofinhibitingautoimmuneresponses.Inexperimentalautoimmuneencephalomyelitis(EAE),ananimal modelofmultiplesclerosis(MS),initialtrialsusingpurifiedmyelinantigensrequiredrepeated injec-tionsbecauseoftherapidclearanceoftheantigens.ThisproblemhasbeenovercomebyDNA-based vaccinesencodingformyelinautoantigensaloneorincombinationwith“adjuvant”molecules,suchas interleukin(IL)-4orIL-10,thatsupportregulatoryimmuneresponses.PhaseIandIIclinicaltrialswith myelinbasicprotein(MBP)-basedDNAvaccinesshowedpositiveresultsinreducingmagneticresonance imaging(MRI)-measuredlesionsandinducingtolerancetomyelinantigensinsubsetsofMSpatients. However,DNAvaccinationhaspotentialrisksthatlimititsuseinhumans.Analternativeapproachcould betheuseofprotein-basedinversevaccinesloadedinpolymericbiodegradablelactic-glycolicacid(PLGA) nano/microparticles(NP)toobtainthesustainedreleaseofantigensandregulatoryadjuvants.Theaimof thisworkwastotesttheeffectivenessofPLGA-NPloadedwiththemyelinoligodendrocyteglycoprotein (MOG)35–55autoantigenandrecombinant(r)IL-10toinversevaccinatemicewithEAE.Invitro experi-mentsshowedthatuponencapsulationinPLGA-NP,bothMOG35-55andrIL-10werereleasedforseveral weeksintothesupernatant.PLGA-NPdidnotdisplaycytotoxicorproinflammatoryactivityandwere partiallyendocytosedbyphagocytes.Invivoexperimentsshowedthatsubcutaneousprophylacticand therapeuticinversevaccinationwithPLGA-NPloadedwithMOG35-55andrIL-10significantlyameliorated thecourseofEAEinducedwithMOG35-55inC57BL/6mice.Moreover,theydecreasedthehistopathologic lesionsinthecentralnervoustissueandthesecretionofIL-17andinterferon(IFN)-␥inducedbyMOG35-55 insplenicTcellsinvitro.ThesedatasuggestthatsubcutaneousPLGA-NP-basedinversevaccinationmay beaneffectivetooltotreatautoimmunediseases.
©2014ElsevierLtd.Allrightsreserved.
Abbreviations: BCA,bicinchoninicacid;CHOs,Chinesehamsterovarycells;CNS,centralnervoussystem;CTL,cytotoxicTlymphocytes;DCM,dichloromethane;DLS,
dynamiclightscattering;EAE,experimentalautoimmuneencephalomyelitis;FDA,foodanddrugadministration;H&E,hematoxylin&eosin;IFN,interferon;IL,interleukin;
LPS,lipopolysaccharide;MCF-7,humanbreastadenocarcinomacellline;MBP,myelinbasicprotein;MFI-R,meanfluorescenceintensityratio;MRI,magneticresonance
imag-ing;MOG,myelinoligodendrocyteglycoprotein;MS,multiplesclerosis;MTT,3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide;Ni-NTA,nickel-nitrilotriacetic
agarose;NIRF,near-infraredfluorescence;NK,naturalkiller;NP,nano/microparticles;OD,opticaldensity;PBMCs,peripheralbloodmononuclearcells;PBS,
phosphate-bufferedsaline;PDI,polydispersityindex;PLGA,polymericbiodegradablelactic–glycolicacid;PLP,proteolipidprotein;r,recombinant;PVA,poly/vinylalcohol;RR,relapsing
remittingform;RT,roomtemperature;s.c.,subcutaneousinjections;SEM,scanningelectronmicroscope;SE,standarderror;TH,Thelper;TEFF,effectorT;TGF,transforming
growthfactor;TNF,TumorNecrosisFactor;TREG,regulatoryT.
∗ Correspondingauthorat:InterdisciplinaryResearchCenterofAutoimmuneDiseases(IRCAD),andDepartmentofHealthSciences,UniversityofEasternPiedmont“A.
Avogadro”,viaSolaroli17,I-28100Novara,Italy.Tel.:+390321660658;fax:+39032162042.E-mailaddress:giuseppe.cappellano@med.unipmn.it(G.Cappellano).
http://dx.doi.org/10.1016/j.vaccine.2014.08.016
5682 G.Cappellanoetal./Vaccine32(2014)5681–5689
1. Introduction
Autoimmunediseasesmaybeascribedtoadisturbedbalance betweentheactivatedeffector T(TEFF)cells that recognize self antigensandtheregulatoryT(TREG)cellsthatsuppressTEFF acti-vationand controlboththeimmuneandautoimmunereactions
[1–5].Severalimmunoregulatorymolecules,suchasIL-10,TGF-ß, andindoleamine2,3-dioxygenase(IDO),cansupportTREGfunction
[3,4,6,7].Inparticular,IL-10playsaroleinthedevelopmentand immunosuppressivefunctionofseveralTREGcelltypes[2]andisa crucialprotectivecytokineinseveralautoimmunediseases[3].
AdoptivetransferofseveraltypesofTREGcellsresultsin pro-tectiveactivityinanimalmodelsofautoimmunediseases,butthe translationofthesestudiestohumanshasbeenhamperedby sev-eralissues[8,9].Inparticular,thelowfrequencyofthesecells,their poorgrowthinculture,andtheirhighfunctionalplasticityinvivo havemadetheiruseasignificantchallenge.Antigen-specific strate-giesmaypotentiallycircumventtheselimitationsinvivo[10,11], buteffectiveapproaches torestoretheTEFF/TREGbalanceinvivo remainlargelyundefined[9].
Multiple sclerosis (MS) is characterized by an autoimmune responseagainsttheaxonsandmyelinsheathsofthecentral ner-voussystem(CNS)thatresultsinaxonallossanddemyelinization
[12].Severalmyelinproteins,suchasmyelinbasicprotein(MBP), proteolipidprotein(PLP),andmyelinoligodendrocyteglycoprotein (MOG),havebeenimplicatedastargetsofautoreactiveTcellsinMS anditsanimalmodel,experimentalautoimmune encephalomyeli-tis(EAE)[12].Accordingtothe“epitopespreading”model, few epitopesandantigensplayaroleintheinitiationorperpetuation ofthedisease,butthisreactivitytendstospreadduringthedisease course[13].
“Inverse vaccination” refers to antigen-specific tolerogenic immunization treatments that restore the TEFF/TREG balance andinhibit autoimmuneresponses. Inversevaccinationmaybe obtained by the prolonged treatment with high doses of the autoantigens.InEAE,systemicadministrationofmyelinantigens eitherpreventedortreatedEAE,butthedeliveryofrepeated mas-sivedoses of theseproteins were required for the therapeutic effect[14–16].ThisproblemhasbeenovercomebyDNA-based vaccinesencoding themyelinantigensalone orin combination withimmunomodulatorymolecules,suchasIL-4orIL-10,thatact as“adjuvants”forTREGfunction[17,18].TheEAEresultswereso promisingthattheypromptedafirstclinicaltrialinMSpatients, thatshowedsomepositiveresultsinreducingtheMRI-measured diseaseactivityandinducingantigen-specifictolerancetomyelin antigensinpatientswithrelapse-remitting(RR)MS[19].However, DNAvaccinationisstillcontroversialinMSsinceasecondphase 2trialshowednosignificantimprovementinmagneticresonance imaginglesionparametersandreductionofnewCNSlesionsonlyin thepatientsdisplayinghighconcentrationsofanti-MBPantibodies
[20].MoreoverwhileDNA-basedvaccinesallowforthesustained expressionofboththeantigensandtheadjuvantmolecules,itis notpossibletocontroltheirdoseorexpressionkinetics,andthis maybeaprobleminthecaseofadversereactions.
An alternative method to obtain the sustained release of antigensandadjuvantsmaybetoloadtheminsolid biodegrad-ableparticles.Polymericbiodegradablelactic–glycolicacid(PLGA) particlesareattractivecarriersduetotheirbiodegradability, bio-compatibilityandapprovalbytheFoodandDrugadministration (FDA)[21].Theymaintaineffectiveconcentrationsoftheloaded proteinsfor prolongedperiods of times by trappingthem in a hydratedpolymernetworkthat enablestheirslowrelease [21]. PLGAallowsforthefine-tuningofthedegradationrateand sub-sequentantigenreleasefromseveraldaystomorethanoneyear by modulating the polymer lactide–glycolide ratio, the molec-ularweight, and thecrystal profile [22]. The controlledand/or
sustainedreleaseofantigensandimmunemodulatorsfrom poly-mericmaterialshasbeenused previouslytoinducethe proper immuneeffectorresponse[23].TheuseofPLGA-NPcanenhance toleranceinductioninsomedeliverysettings,suchasnasal vacci-nation[24].Moreover,arecentstudyshowedthattheintravenous infusionofeitherpolystyreneorPLGAparticleschemically cou-pledwithanencephalitogenicpeptidecanpreventandcureEAE
[25].Thatstrategystemmedfrompreviousobservationsshowing thatautoantigenicpeptidescoupledtoapoptoticleukocytescan induceantigen-specifictoleranceinmodelsofautoimmune dis-eases,allergy,andtransplantationbyinducingthedepletionand anergyoftheantigen-specificlymphocytes.However,akey limi-tationofthisapproachwasthatitrequiredsystemic(intravenous) injectionofthevaccineandwasnoteffectiveuponlocal(suchas subcutaneous)injection[25].Thisimpliesthattheintrinsicrisksof lifethreateningadversereactions(suchassystemicanaphylaxis) mightdiscourageuseofthesevaccinesinhumans.
Theaimofthepresentstudywastodevelopanovelapproachfor inversevaccinationbasedonthesustainedreleaseofautoantigens andadjuvantsfromPLGA-NPdeliveredsubcutaneously.
2. Materialsandmethods
2.1. PLGAproductionandcharacterization
PLGANPwerepreparedbyamodifieddoublesolvent evapora-tionmethod[26].NanoparticlescontainingMOG35-55(MOG-PLGA), IL-10(IL10-PLGA),6-coumarin(C6-PLGA)orIR783(IR783-PLGA) fluorescentdyeswereproducedbyaddingMOG35-55(200g), IL-10(200g),6-coumarin(C6)(6mg)orIR783(6mg)tothePLGA solutionduringthepreparation.ThereleaseofMOG35-55andIL-10 wereevaluatedbydialysisinPBSat37◦C,andtheproteinsreleased werequantifiedbytheBCAassay(forMOG35-55)andbyELISA(for rIL-10).DetailsaregiveninSupplementaryinformation.
2.2. Invitrobiologicalanalyses
Cell toxicity was assessed in humanbreast adenocarcinoma cellline(MCF-7)usingtheMTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide)assay.
Proinflammatoryactivitywasassessed onhumanperipheral bloodmononuclearcells(PBMCs)thatwereculturedwithPLGA particles and/or bacterial lipopolysaccharide (LPS; 1g/ml) for 48h.Then,TumorNecrosisFactor(TNF)-␣secretioninthe super-natantwasmeasuredbyELISA.
ThecellularuptakeofPLGA-NPwasinvestigatedinMCF-7cells incubatedwithC6-PLGA-NPat37◦Cfor4h.Then,thecellswere analyzedbyconfocallasermicroscopyandflowcytometry.
LymphocyteactivationwasassessedinEAEmousespleencells culturedinthepresenceandabsenceof10g/mlMOG35-55for5 d.Then,thesupernatantswerecollected,andthelevelsofIFN-␥, IL-10,andIL-17wereevaluatedbyELISA.
Histologic analysisof the EAElesions wasperformed inthe spinal cords fixed in 10% formalin. Sectionswere stained with hematoxylin&eosin(H&E)andwithLuxolfastbluedyeformyelin staining. Detailsof thesemethods are given in Supplementary information.
2.3. Invivoanalyses
FemaleC57BL/6micewerepurchasedfromHarlan(Horst,The Netherlands)andwerehousedunderspecificpathogen-free con-ditionsattheanimalfacilityattheUniversityofEasternPiedmont “A.Avogadro”(Novara).Theexperimentswereperformedin accor-dancewiththeguidelinesoftheInstitutionalEthicalCommitteefor AnimalExperimentation.
Fig.1. PhysicalandchemicalanalysisofPLGA-NP.(A)SEMmicrographsofblank-PLGAand(B)theparticlesizedistributionofblank-PLGA,IL10-PLGAandMOG-PLGA
assessedbyDLSanalysis;(C)Invitrocumulativerelease[%]ofMOG35-55andhumanIL-10fromPLGA-NPinPBS(pH7.4)at37◦C.Thedataareshownasthemean±SEfrom
2independentexperiments.
ThebiodistributionofPLGA-NPwasassessedinC57BL/6mice afterasubcutaneous(s.c.)injectionofIR783-PLGAorPBS.After7 d,themicewereeuthanized,andtheirorganswereanalyzedwith anIVIS®imagingsystem(PerkinElmer).
Prophylactic and therapeutic vaccination was performed in femaleC57BL/6micewithEAEinducedaspreviously described
[27]. Mice(4–8 weeksold) werevaccinated bys.c. injectionof PLGA-NPloadedwitheither2gMOG35-55ormouseIL-10.The NPweredissolvedin PBS,andtheinjectionsweregiveninone flank either (i) on days-30 and -15 (prophylactic vaccination) fromEAE induction (day 0)or (ii)on days8 and 22 after EAE induction (therapeutic vaccination). Each experiment involved 5–10mice/group. Details are given in Supplementary informa-tion.
2.4. Statisticalanalysis
The statistical analyses were performed using the Mann–WhitneyU-testcalculatedwithGraphPadInstatsoftware (GraphPadSoftware,SanDiego,CA).
3. Results
3.1. PhysicalandchemicalcharacterizationofPLGA-NP
We produced PLGA 65:35 lyophilized nanoparticles that were unloaded (blank-PLGA) or loaded with either
MOG35-55 (MOG-PLGA) or rIL-10 (IL10-PLGA). PLGA-NP were dispersedindistilledwaterandanalyzedforsizedistributionand zetapotential;theparticles werealsoimagedusing ascanning electronmicroscope (SEM).Similarresultswere obtainedusing blank-PLGAparticlesandMOG-PLGAorIL10-PLGAparticles.The SEMshowedasphericalshapewithasmoothsurfacelackingany evidentirregularities(Fig.1A).Thesizedistributionwasevaluated bydynamiclightscattering(DLS)andranged100–1000nmwith apeakapproximately200nmandapolydispersityindex(PDI)of approximately0.2forallformulations(Fig.1B).Thisbehaviorcan berelated to thenegative chargedensity (-potential=−19mV forPLGA;−21.1forIL-10and-−24.9mVforMOG35-55)exposed onthesurfaceoftheparticlesasaconsequenceofthepresenceof carboxylatesmoietiesinthestructure.
The loadingefficiencyof MOG35-55 and IL-10wasevaluated bycalculating theamountof proteinrecoveredafter dissolving MOG-PLGAandIL10-PLGAinNaOH(1M)andneutralizingbyHCl (1N).Theresultsshowedthattheloadingefficiencywas approxi-mately23%forrIL-10and90%forMOG35-55.Thisdifferencemaybe ascribedtothedifferentsizesofthesemolecules(19kDaforrIL-10 and2.5kDaforMOG35-55).
The invitro release of humanIL-10or MOG35-55 from their respectivePLGA preparationswasassessed byincubating these particles inPBS at 37◦C and samplingthesupernatant weekly. TheinvitroreleaseprofilesshowedthatPLGAprovidedsustained releaseofeachproteinforseveralweekswithsimilarkineticsfor eachprotein(Fig.1C).
5684 G.Cappellanoetal./Vaccine32(2014)5681–5689
3.2. BiologicalcharacterizationofthePLGA-NP
The cell toxicity of the PLGA preparations was assessed by performinganMTTassayonMCF-7cellsincubatedwithtitrated amounts(0.6,6, 60, and600g/ml)of blank-PLGA.Theresults showednosignificanttoxicityatanydose(datanotshown).
Thepro-inflammatory activityof blank-PLGAand IL10-PLGA wasevaluatedbyassessingtheabilityoftheparticlestoinducethe secretionofTNF-␣inhumanPBMCs.HumanPBMCswereincubated withtitratedamounts(0,6,60,600g/ml)ofeachPLGA prepa-rationinthepresenceandabsenceofLPS(1g/ml),and TNF-␣ secretionintotheculturesupernatantwasassessedafter48hby ELISA.Atconcentrations≥60g/ml,theblank-PLGAinduced TNF-␣secretionandincreasedtheresponsetoLPS.Bycontrast,none oftheIL10-PLGAdosesinducedTNF-␣secretion,andeachdose inhibitedthatinducedbyLPS(Fig.2).
ThecellularuptakeofthePLGAnanoparticleswasassessedby incubatingMCF-7cellsfor4hwitheithercoumarin6(C6),a fluores-centlipophilicdyethatemitsintheFL-1channel,orC6-PLGA.The cellularuptakeofthefluorescentsubstancewasthenassessedby bothconfocalmicroscopyandflowcytometry.Theresultsshowed that C6-PLGA waspartially taken up byphagocytes in a dose-dependentmanner,andnosubstantialuptakewasdetectedwith C6alone(Fig.3AandB).
The in vivo biodistribution of the PLGA preparations was assessedbyinjectingmicesubcutaneouslywithPLGA-NPloaded withtheIR783infrareddye(IR783-PLGA)orPBS(control).After 7 d, mice were euthanized, and their organs were analyzed by fluorescence imaging. As shown in Fig. 3C, strong signals were detected in the brain, heart, kidneys and, especially, the
Fig.2.TNF-␣productionwasassessedbyELISAinPBMCsculturedwith
blank-PLGAandIL-10(human)inthepresenceorabsenceoflipopolysaccharide(LPS)at
1g/ml.Statisticalanalysiswasperformedwiththenon-parametricANOVAtest;
thedataarethemean±SEfrom5experiments.*Significantlydifferent(p<0.05)
fromblank-PLGA;significantlydifferent(p<0.001)fromblank-PLGAplusLPS.
lungs.Mildsignalsweredetectedintheliver,spleenandlymph nodes.
3.3. InversevaccinationofmicewithEAE
WeevaluatedtheinvivoeffectoftreatmentswithMOG35-55 -based PLGA inverse vaccines in EAE induced in C57BL/6 mice.
Fig.3.CellularuptakeandbiodistributionofPLGA-NP.(A)and(B)MCF-7cellswereincubatedwith120g/mlofC6-PLGA-NPfor4h,andfluorescenceuptakewasassessed
byconfocallaserscanningmicroscopy(A)andflowcytometry(B);representativeresultsfromthreeindependentexperimentsareshown.(C)Micewereinjectedwith
IR783-PLGA,andtheheart(H),liver(L),spleen(S),lung(L),kidney(K),brain(B)andlymphnodes(Ly)werecollectedafter7dandanalyzedbynear-infraredfluorescence
Fig.4.ProphylacticinversevaccinationofEAEmicewithdifferentPLGApreparations.Individual(upperpanels)andcumulative(lowerpanel)resultsfromtwoindependent
experiments.DailyclinicalscoresofEAEinmicetreatedwithblank-PLGA,MOG-PLGA,IL10-PLGAorMOG-PLGAplusIL10-PLGAondays-30and-15priortoEAEinduction.
Experiment1:5–8mice/group;experiment2:8–10mice/group.Resultsareshownasmean±SE.TheMann–WhitneyU-testwasusedtocomparetheclinicalscores:
IL10-PLGA+MOG-PLGAvsPLGA(*),IL10-PLGA(§),MOG-PLGA(#);*,§,#p<0.05.
Mice(n=5–10/group)werevaccinatedvias.c.injectionofeither blank-PLGA,MOG-PLGA,IL10-PLGAorMOG-PLGAplusIL10-PLGA in one flank ondays-31 and -15 prior to EAE induction (pro-phylacticinversevaccination).Theresultsfromtwoindependent experimentsshowedthat,atseveraltimepoints,treatmentwith MOG-PLGAplus IL10-PLGAsignificantly inhibited EAE develop-ment comparedto theothertreatments (Fig.4).Moreover,the average daily disease score calculated on the cumulative data fromboth experiments wassignificantly lower in micetreated with MOG-PLGA plus IL10-PLGA (mean±SE, 1.3±0.17) than in those treated with blank-PLGA (1.8±0.23, p<0.05) or IL10-PLGA(1.8±0.22, p<0.05). Asmall effectwasdisplayed alsoby MOG-PLGAalone (1.5±0.19)which inhibited EAE comparedto blank-PLGAandIL-10-PLGAaloneatsometimepoints,butno sig-nificantdifferencesweredetectedatthelevelofaveragedisease scores(Fig.4).Bycontrast,IL10-PLGAalonehadnoeffect.No vac-cinationdelayedthediseaseonset.
TheeffectofthevaccinationontheimmuneresponseandCNS lesionswasevaluatedbycomparingtheanti-MOGspleen lympho-cyteresponseandthehistopathologiclesionsinmicetreatedwith MOG-PLGAplusIL10-PLGAandthosetreatedwithblank-PLGA.The anti-MOGresponsewasassessedbyincubating spleen lympho-cytescollectedatday21(thediseasepeak)afterEAEinductionwith MOG35-55andassessingcellproliferation(by3H-thymidine incor-poration)andthesecretionofIFN-␥,IL-17,andIL-10intheculture supernatants(byELISA)aftera 5d culture.Theresultsshowed that vaccination with MOG-PLGA plus IL10-PLGA significantly inhibitedthesecretionofIL-17andIFN-␥comparedtovaccination withblank-PLGA,whereas nosignificanteffect oncell prolifer-ationwasdetected(Fig.5A).ThesecretionofIL-10wasalways
undetectable(datanotshown);thisobservationisinaccordance withdatareportedbyotherauthors[28].
Thehistopathologicanalysiswasperformedonthespinalcords ofmicecollectedatday21afterEAEinduction.Lightmicroscopy analysis revealed that the mice treated with blank-PLGA dis-played a higher inflammatory cell infiltrate than those treated withIL10-PLGAplusMOG-PLGA,butthisdifferencewasnot sta-tisticallysignificant(Fig.5B).However,detectionofCD3+ Tcells byimmunofluorescenceshowedthattheywerestrikinglymore abundantintheformerthaninthelattergroup.Moreover,myelin stainingshowedasignificantlydramaticlossofmyelininthemice treatedwithblank-PLGA,whereasmicetreatedwithMOG-PLGA plusIL10-PLGAshowedmildmyelindamageonlyinthesubpial myelin(Fig.5B).
Finally, we assessed theeffect oftreatment withthe differ-entPLGApreparationsdeliveredafterEAEinduction(therapeutic inversevaccination).Mice(n=8–10/group)wereinjecteds.c.with either blank-PLGA, MOG-PLGA, IL10-PLGA or MOG-PLGA plus IL10-PLGA on days 8 and 22 after EAE induction. The results from two independentexperiments showedthat, at mosttime points, treatmentwith MOG-PLGAplus IL10-PLGAsignificantly inhibitedEAE developmentcompared totreatmentwith blank-PLGAorIL-10-PLGA(Fig.6).Moreover,theaveragedailydisease scorecalculated onthecumulativedatafrombothexperiments wassignificantlylowerinthemicetreatedwithMOG-PLGAplus IL10-PLGA(mean±SE,1.2±0.15)comparedtothosetreatedwith blank-PLGA(1.8±0.24,p<0.05)orIL10-PLGA(1.8±0.23,p<0.05) orMOG-PLGA(1.6±0.20,p<0.05)(Fig.6).Bycontrast,MOG-PLGA andIL-10-PLGAhadnosubstantialeffect.Novaccinationdelayed thediseaseonset.
5686 G.Cappellanoetal./Vaccine32(2014)5681–5689
Fig.5.TcellresponseandhistopathologiclesionsinEAEmicevaccinatedwithblank-PLGAorMOG-PLGAplusIL10-PLGA.(A)Spleenlymphocyteswerecollected21dafter
EAEinductionandculturedwithMOG35-55;cellproliferationandthesecretionofIFN-␥andIL-17intheculturesupernatantswereassessedaftera5dcultureperiod.(B)
Histopathologicanalysisofthespinalcordscollectedfrommice21dafterEAEinduction;dataareshownasrepresentativestainingsandquantitativeanalysisperformedin
multipleexperiments(bargraphs).H&Estaining:(a)blank-PLGA,(b)MOG-PLGAplusIL10-PLGA(arrowsmarktheinflammatoryinfiltrate).Immunofluorescencestainingof
CD3+Tcells:(c)blank-PLGA,(d)MOG-10plusIL-10PLGA;KB(myelin)staining:(e)blank-PLGA,(f)MOG-PLGAplusIL10-PLGA;arrowsindicatemyelinvacuoles.Magnification
20×.Thedataarethemean±SEoftheresultsfrom6to8mice.StatisticalanalysiswasperformedwiththeMann–WhitneyU-test(*p<0.05).
4. Discussion
Thisworkshowsthats.c.inversevaccinationwithamixture ofPLGAloadedwithMOG35-55andIL-10iseffectiveatdecreasing diseaseseverityinmouseEAE.
Polymericmaterialshavebeeninvestigatedfortheirabilityto inducetheproperimmuneeffectorresponses,andinsomecases, topromotetolerance.Becausetheinductionandmaintenanceof immune toleranceis influenced bythe persistenceof the anti-genand can besupported bytolerogenic cytokines,theuse of biodegradablemicro-nanoparticlesisidealforinversevaccination becausetheycansupportasustainedreleaseofseveralentrapped molecules[23].
Anidealnanoparticleforinversevaccinationshoulddisplaylow celltoxicity,lowproinflammatoryactivity,sustainedreleaseofthe vaccineactivecomponents,andsloweliminationbyphagocytesto allowtheirpersistenceinvivotopromoteregulatoryratherthan
effectorimmunefunctions.TheMTTassayonMCF-7cellsshowed thatourparticleswerenottoxic,whichisinaccordancewithdata reportedbyothergroups[29].
Regarding the proinflammatory activity of PLGA, the data reportedintheliteraturearecontroversial.Nicoleteetal.showed thatPLGAnano/microparticlespersecanactivatetheinflammatory response;inparticular,microparticles(usedat1mg/ml)withasize rangingfrom5to7minducedtheproductionofhigheramounts ofTNF-␣inmurinemacrophagesthanthoseinducedby nanopar-ticles [30,31]. In our experimentalsetting, blank-PLGA induced TNF-␣productionatdoses≥60g/ml,butthisproinflammatory effectwasnotdetectedwhenusingIL10-PLGA;instead,these parti-clesinhibitedtheTNF-␣secretioninducedbyLPS.However,itmust benotedthattheinvivoexperimentsshowedthattheEAEonset wasearlierintheprophylacticvaccinationthaninthetherapeutic vaccinationwhichsuggeststhatpretreatmentwiththePLGA-NP maypreconditiontheinductionofEAEbystimulatingtheinnate
Fig.6. TherapeuticinversevaccinationofEAEmicewithdifferentPLGA-NPpreparations.Individual(upperpanels)andcumulative(lowerpanel)resultsfromtwoindependent
experiments.DailyclinicalscoresofEAEinmicetreatedwithblank-PLGA,MOG-PLGA,IL10-PLGAorMOG-PLGAplusIL10-PLGAonday8and22afterEAEinduction.
Experiment1:5–8mice/group;experiment2:8–10mice/group.Resultsareshownasmean±SE.TheMann–WhitneyU-testwasusedtocomparetheclinicalscores:
IL10-PLGA+MOG-PLGAvsPLGA(*),vsMOG-PLGA(#),IL10-PLGA(§),#,*,§,p<0.05.
immunity.ThisisinlinewithworksshowingthatPLGAparticles maysupportimmunizationinclassicalvaccinationsettings[32].
ThereleaseofMOG35-55andIL-10fromthePLGA-NPwas sus-tained,andbothmoleculeswerereleasedforseveralweeksinvitro. Theparticleswerepartiallyendocytosed,aneffectthatisbeneficial forantigenpresentation,butthisdidnotsubstantiallyaffecttheir invivobiodistribution.
TheinvivoexperimentsinEAEshowedthatvaccinationwitha mixtureofMOG-PLGAandIL10-PLGAdisplayedasignificant pro-tectiveeffectanddecreasedtheseverityofthedisease.Thiseffect wasdetectednotonlywhenvaccinationwasperformedina pro-phylacticsetting,i.e.,beforeEAEinduction,butalsowhenitwas performedinatherapeuticsetting,i.e.,afterthediseaseonset.Thus, itmaybeapotentialtreatmentforpatientswithMS.
TheprotectiveeffectofIL10-PLGAandMOG-PLGAwas accom-paniedbydecreasedhistopathologiclesionsinthespinalcordand decreasedlymphocytesproductionofIFN-␥andIL-17-inresponse toMOG35-55invitro.Theseresultssuggestthatthisinverse vacci-nationinhibitstheautoantigen-specificTH1andTH17responses thatarecrucialinthepathogenesisofMSandEAE.Bycontrast, MOG-PLGAhadaminimaleffectthatwasdetectableonlyinthe prophylactictreatment.Moreover,IL10-PLGAhad noprotective effectinanyprotocol,whichisinaccordancewithpreviousdata fromCannellaetal.showingthattreatmentwithIL-10doesnot protectfromEAE[33].Theseresultsareinlinewiththoserecently reportedbyPeine etal.showingeffectivenessofEAE treatment bycodeliveryofMOGanddexamethasoneinacetalateddextran microparticles[34].Therefore,deliveryoftheautoantigentogether withimmunosuppressiveagents,suchasIL-10ordexamethasone, iscrucialtosuppresstheautoimmuneresponse.Dataobtainedwith tolerogenicDNAvaccinesindicatethattheseimmunosuppressive
agentsmayactas“inverseadjuvants”supportingtheinductionof tolerance.Lackofthese“inverseadjuvants”mayexplainthe fail-ureofclinicaltrialsusingautoantigensor“alteredpeptideligands” alonewhichwereterminatedbecauseoflackofsubstantialclinical effectsanddevelopmentofhypersensitivityreactions[35].
Itisnoteworthythatourvaccinationwaseffectivebythes.c. route.Thismarksa keydifferencefromtheinversevaccination performedbyGettsetal.withMOG35-55covalentlylinkedtothe surfaceofeitherpolystyrenebeadsorPLGAparticles[25].These authorsobtainedastrikingprotectiveeffectusingboth prophylac-ticandtherapeutictreatments,butthiseffectstrictlydependedon theintravenousdeliveryofthevaccine,whichmayrestrictitsuse inhumansbecauseofthepotentialriskofanaphylacticreactions. Theeffectofthisintravenousvaccineseemedtobemediatedby theinductionofTcellanergy,asindicatedbyastronginhibition oflymphocyteproliferation;thiswaspossiblydrivenby tolero-genicmacrophagestakinguptheantigenafterscavengerreceptors recognizedthenanoparticlescovalentlylinkedtotheselfpeptide. By contrast,ourvaccineuses particlesthat slowlyrelease both theautoantigenandIL-10.ItdoesnotinhibitTcellproliferation, butinsteadinhibitsthesecretionofIFN-␥andIL-17.Therefore,it seemstoinduceimmunedeviationinsteadofanergyandopens thewaytofurtherstudiesaimingtoamelioratethemixtureof autoantigensandimmunosuppressiveadjuvants.Ourdatadonot supportthepossibilitythattheprotectiveeffectwasmediatedby CD4+CD25+FoxP3+T
REGcellssincetheirnumbersweresimilarin thespleensof micetreatedwithblank-PLGA andthose treated withIL-10-PLGAplusMOG-PLGA(datanotshown).Thisisinline withotherreports[34],butitdoesnotruleouttheinvolvement ofotherpopulationsofregulatorycellsorCD4+CD25+FoxP3+T
REG cellscompartimentalizedinothertissues[36,37].
5688 G.Cappellanoetal./Vaccine32(2014)5681–5689
The in vivo biodistribution of the PLGA-NP was intriguing becausesubstantialamountsweredetectableinseveralorgansone weekaftertheinjection.Thisbiodistributionisinaccordancewith worksshowingthatparticles<50nmrapidlydiffusefromthe injec-tionsite,whereasthose>1–5mtendtostayattheinjectionsite
[38].Becausethesizesofourparticlesrangedfrom100nmto1m, itisconceivablethatthesmallestofthemwerereadilyableto dif-fuse.Itisnoteworthythatamongtheotherorgans,thestrongest signalwasdetectedinthelungs.Thelungshavebeenshownto playakeyrole inlicensingTcells toenterCNS[39].Thesignal inthebrain isalso intriguingbecauseit suggeststhat the vac-cinemightexertanimmunoregulatoryeffectdirectlyatthesite oftheautoimmuneaggression.Thiseffectwasnotsimply ascrib-abletoanaspecificimmunosuppressiveactivityofIL-10because noeffectwasdetectedusingIL10-PLGAalone.Becausechanging theparticlesizewouldprofoundlyaffectthebiodistribution, fur-therworkisneededtoassesstheroleofthePLGAparticlesizein theimmunosuppressiveeffect.
Akeyproblemfortranslatingthisapproachtohumansisthat, inMS,thetargetautoantigensarenotfullyknownandmayinvolve molecules differentfrom MBP, MOG and PLP knownto play a roleinEAEandMS.Moreover,theautoreactivityisheterogeneous indifferentpatientsandchanges duringthediseasecoursedue toepitope spreading[12].However,severalworks showedthat tolerogenicvaccination,too,mayinduceanepitopespreadingof thetolerance and maygradually involve also autoantigens not includedinthevaccine.Moreover,ameliorationof thevaccines mightbeobtainedusingmixturesofautoantigens[40,41].
Inconclusion,thisworkshowedthatPLGA-basedinverse vac-cinationdelivered subcutaneously may be effective in treating autoimmunediseases. Current treatments for autoimmune dis-eases(i.e.,MS)arebasedonimmunosuppressive therapies that affecttheglobalimmuneresponseanddisplaysignificanttoxicity, especiallywhenchronictherapyisneeded.Evennovel biotechno-logicaldrugsdonotsolvethisproblembutinsteadaddthefurther problemofadramaticincreaseintheeconomiccostsofthe ther-apy.Effectivetherapieswithlowcostandlowtoxicityareneeded bypatients and by thepublichealth systems.Inverse vaccina-tionwould meetthesecriteriabecauseitiscapableofinducing anautoantigen-specificimmunosuppressionwiththepotentialof beinglowcostandlonglasting.
Conflictofinterest
Theauthorsstatethatthereisnoconflictofinterest.
Acknowledgments
ThisworkwassupportedbyCompagniadiSanPaolo(Torino), FondazioneCariplo(Milano),FondazioneAmicidiJean(Torino), AssociazioneItalianaRicercasulCancro(Milano),FondazioneCassa diRisparmiodiCuneo.
AppendixA. Supplementarydata
Supplementarymaterialrelated tothis article canbefound, in the online version, at http://dx.doi.org/10.1016/j.vaccine. 2014.08.016.
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