The Essenality and Mystery of Pyrazinamide€¦ · Medium and specimen preparation: “cultures of...
Transcript of The Essenality and Mystery of Pyrazinamide€¦ · Medium and specimen preparation: “cultures of...
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TheEssen(alityandMysteryofPyrazinamide
OrenZimhonyMDInfec(ousDiseasesDepartmentKaplanMedicalCenter,affiliatedtotheSchoolof
MedicineHebrewUniversity
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Content • Historicnotes• ThePZAparadox,thedifficul(es
• Simula(onsinvivobyinvitrocondi(ons? • PZAresistanceandsuscep(bility• Theuniquesuscep(bilityofTBtoPZA• PZAanalogs,whatdidwelearn?• Insearchoftheactualsiteofac(on• Summary
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PZAhistory,thebeginning
• 1936 Dalmer O& Synthesis of PZA Walter E
• 1945 Chorine V Nicotinamide efficacy TB in mice
• 1952 Kushner S Testing PZA in mice
• 1952 Yeager et al. First Clinical Use
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TheCornellgroupcontribu(on
• 1954 McDermott W& Activation of PZA in acidic Tompsett R environment
• 1956 Mackaness GB Activity of PZA in macrophages
• 1956 McCune RM The model of TB latency and sterilization.
• 1967 Konno K et al. Resistance to PZA loss of PZAse NAMase activity
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Introduction of PZA into clinical studies and practice
• 1970s-1980s British PZA allows short Medical Research course chemotherapy Council Mitchison D
Formal guidelines (ATS) for TB therapy include PZA for first two month with INH and RIF
• 1988-1991 Salfinger M Standardized broth Heifets LB test for PZA
•
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PZAresistance,uniqueac(vityandprospect
• 1991‐1995WelchJ,Synthesisandtes(ngofCynamonMHseveralPZAanalogs
• 1996ScorpioA,Iden(fica(onofpncAgeneZhangY encodingpyrazinamidase
• 1999ZhangYRoleofacidicpHPZAScorpioA uniqueac(vityinMTB
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ThemysteryofPZA?
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WhyPZAissoMysteriousorwhatmakesitsstudysodifficult?
• Discrepancybetweenthesterilizingac(vityinanimalmodelsandhumanandin–vitroac(vity.“ThePZAparadox“
• Poorac(vity:Inoculumeffect,lackofbactericidalac(vity
• Acidmediumdependentac(vity
• Difficulttoassesssuscep(bility/resistance
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TheImplica(onofpoorac(vityforPZAStudies.
DoesPZAisgivenandisreachingsufficientc%foranexpectedeffect?
Indrugsuscep(bilitytests
Inphysiologic/biochemicaltests
Animalandclinicalstudies
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Sterilizing Effect of PZA in Murine Model (McCune R M, et al. JEM 1956)
“The fate of Mycobacterium tuberculosis in mouse tissues as determined …“ H isoniazid S streptomycin , P Para amino salicylic acid, Z pyrazinamide
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TheCornellModelStudies(McCuneRM,McDermo`W1956‐1965).
• PZAisindispensablefor(ssuesteriliza(on
• Sterilized/curedmicerelapsed
• Theremainingbacilli“Persisters”remainedfullysuscep(bletothedrugs.
• Extensionofdrugtherapyfrom12wto26wresultedinlas(ngcure.
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Interpreta(onoftheCornellModelResults
• “ThiscompletedisappearanceofTBbacillimeetsthedefini(onofatrulylatentinfec(on…ishiddenbeyondthelimitsofdiagnos(creach”
• Doesthestateoflatencyimplies“dormancy““semidormancy”?
• Whatismeantbydormancyinvitro?
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Howrelevantarein‐vitroCondi(onsandSimula(ontoExplainthePZAParadox? • WheredowefindacidicpHinthecontextofTB,thephagosome?casea(nggranuloma?
• DoescausinglatencythroughPZAimplyac(vityagainst“dormant”orsemidormant“bacilli
• Doestrea(nglatentTB(clinicalseeng)implyac(vityagainstsemi/dormantbacilli?
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Ac(vityofPZAAgainstReplica(ng vs.NonReplica(ngBacilli“Semi‐Dormant”?.
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InfavorofPZAEffectagainstReplicatingBacilli
• PZAiseffectivetherapeuticallywhengivenearly.
• InEx-vivomodel:AwindowofdrugsusceptibilitythatcoincideswiththeonsetoftheT-cell-mediatedimmuneresponse
• ALLSusceptibilitytestsforPZArecommendusageoffreshlydilutedreplicatingbacilli.
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Medium and specimen preparation: “cultures of M. tuberculosis should be freshly grown in …..should be used for this test when they are in an active growth phase. Do not use old, refrigerated cultures or cultures which have shown peak GI readings for more than one day.”
“Scrape with a sterile loop as many colonies as possible from growth no more than fourteen days old”
Suscep(bilityTests,replica(ngBacilliattherightInoculum
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Suscep(bilityandResistancetoPZA.
• PrinciplemechanismofresistancelackofPZAaseac(vityduetopncAlossoffunc(onmuta(ons
• Reliable/reproducibletestforR/SischallengingFalseresistance,amajorproblem
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• TestsforPZAsuscep(bility/resistance:1.Culturemethodsplatesandbrothtests
2.Nico(namidesuscep(bilitytoNAMat5000µg/mlpH7!!!TanThiamHok’stest(1962)
3.Enzyma(ctestsforPZAseac(vity,Waynetest(1974)
Suscep(bilityandResistancetoPZA(2)
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Suscep(bilityandResistancetoPZA(3)
4.SequenceofpncA
• DiscrepancyinpncAmuta(onsratebetweenstudies
• PZAse‐,nopncAmuta(ons
• Alterna(vemechanism? PZAase+ Notexcludedrare
• LackofdataonRrateevenfromdeveloped
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PZA Conversion and Accumulation.
Studiesusing14CPZA
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TheRoleofPncAinPOAAccumula(on
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WhatUnderliestheUniqueSuscep(bilityofTBtoPZA?
• MycobacteriaspeciesthatareproficientinPZAseyetPZAresistant.
• MSMGpossesstwoPZAsesPncAandPzaAandisPZAR,MIC>2000µg.
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Differences in POA accumulation between M. tuberculosis (M. tb and M. smegmatis (M. smeg.
TheUniqueSuscep(bilityofTB,morethanPZAse
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Effect of reserpine and valinomycin on accumulation of POA in M. smegmatis (A) and M. tuberculosis (B).
TheUniqueSuscep(bilityofTBamongstMycobacteriatoPZA
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Otherfactors?EffectofAera(ononPZAAc(vityagainstM.tuberculosis
H37Ra cells were treated with 100 g PZA ml1 (filled bars) or not (open bars), under aerobic, microaerobic or anaerobic conditions for 5 days prior to c.f.u. determination.
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CanIncreasedPZAseAc(vityAffecttheSuscep(bilitytoPZA?
• PZAdeamida(oncanbecatalyzedbyPncAandbyPzaA
• IncreasedPZAseac(vityleadstoMSMGsuscep(bilitytoPZA
• IncreasesMTBsuscep(bility
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PZAAnalogs
• Thera(onale?CircumventPZAseIncreasepotencyExpandac(vitytootherspecies
• Pyrazinoates(POE),5‐Cl‐PZAanalogs,5‐Cl‐POE,5‐fluoropyrazinoates(5‐F‐POE).
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SummaryandConclusionfromPZAAnalogsAc(vity
• Insolubleinwater.
• Broaderspectrumac(vitythatincludeM.avium,M.kansasii,M.smegama7s
• Higherpotency(upto100folds)forMTB.
• EsterhydrolysisofPAEsispossiblebutisnotrequired.
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SummaryandconclusionfromPZAAnalogsAc(vity(2)
• 5‐Cl‐PZAdoesnotrequireconversionto5‐Cl‐POA(ac(veinM.bovislackingit).
• 5‐Cl‐POA,astrongeracidthanPOA,ismuchlessac(vethaneither5‐Cl‐PZAorPOA.
• Neither5‐ClPZAorn’PPArequireacidicpH,yetsufferfrominoculumeffect.
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MutuallyExclusiveGenotypesfor Pyrazinamideand5‐Chloro‐pyrazinamideResistance
BaughnA,DengJetal.AAC2010
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MutuallyExclusiveGenotypesforPZAand5‐Cl‐PZAresistance
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PZAseac(vityin5‐Cl‐PZAresistantstrainsMSMEG
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IncreasedconversionofPZAdiminishtheRequirementforAcidicpH
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AcidicpH
ConversiontoPOA Deficient
effluxofPOA
PZA/POAAc(vity
POAAccumula(on
?
Hypoxia“stress”
Accumula(onforac(va(on
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HowPZAworks?InherentDifficul(esinIden(fyingtheActualMechanism
• NoBona‐fidePOAresistantmutantAbsenceofPOAR??Morethanonemechanismorintolerablemuta(on.
• Needtocorrelatean(mycobacterialac(vitywithbiochemicaleffect
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Iden(fica(onoftheTargetof5‐Cl‐PZA
• Selec(onof5‐Cl‐PZAresistantmutantsinMSMEG
• Therangeofresistanceofthemutants(5‐Cl‐PZAR)isnarrow
• Fa`yacidsynthase1(fas1)isthegenethatconfersthisphenotype(a9.3kbORF)
• MTBdoesnottoleratemul(copyfas1orevenasinglecopyfromMSMEG.
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Fa#yacidsynthesisinmycobacteriaandrelatedspecies
• FASIsystemAllnon‐planteukaryotesandcertainprokaryotes
Mul(‐func(onalmul(‐domainproteincatalyzesthesynthesisoflongchainfa`yacidsfromC2units
• FASIIMostprokaryotes,individualenzymes
• Mycobacteria:BothFASIandFASII,FASIIgeneratesmycolicacidprecursors
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PZA/POA Activity Correlates with Inhibition of FA Biosynthesis
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APyrazinoateEster,n’PPAInhibitsFa`yAcidSynthesisinM.tuberculosis
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POAInhibi(onofFa`yAcidBiosynthesisinTBComplexBacilliCorrelatestoAn(mycobacterial
Ac(vity
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M. tuberculosis FAS I Inhibition in Cell Free System using NADPH Oxidation
Effect of increasing inhibitor concentration on NADPH oxidation. Blank runs with no enzyme are included for reference.
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MinimalStructureofPyrazineRingwithanAcylGroup.
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HPLC analysis of C16:0 to C26:0 fatty acids from PZA-treated MSMEG mc2155 and mc27031, treated with 2.5 mg/ml PZA for 2 h, and then pulsed with [1-14C]acetate for an additional 2 h.
Susceptibility to PZA Translates to Inhibition of FA Synthesis in MSMEG
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Similari(esbetweenPOAand5‐Cl‐PZA,n’PPA
• Rela(velypoorsimilarbacteriosta(cac(vity,andkillingcurvein‐vitro
• NoresistantmutantsinMTB
• Correla(onofan(‐mycobacterialac(vitytopalmitatebiosynthesisinhibi(on
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Similari(esbetweenPOAand5‐Cl‐PZAn’PPA(2)
• Invitroinhibi(onalbeitmarkeddifferenceinpotency
• BindingtoFASINMRstudies
Dissimilari(esbetween5‐Cl‐PZAandPOANeedforacidicpH
EffectofFASIoverexpressiononPZAresistanceinMSMEG
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Conclusions • SufficiencyofPZA/POAisessen(alforcorrectinterpreta(onandreproducibility
• PZAstudiesshouldbeconductedonreplica(ngbacilli(variouscondi(ons,exvivomodelsetc)
• AcidicpHisacondi(onforPOAaccumula(oncanbepar(allysubs(tuted,no“mechanis(c”role
• Anaccumulateddependentagentaffectsanintracellularsite
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H+ + POA-
ATP dependent defective efflux
Passive diffusion
Deamidation
Passive diffusion
PZA POA
POA entrapment and “huge” accumulation
? Intracellular target, FAS I
Kill of replicating bacilli
PZA activity against MTB bacilli in media anoxic/acidic
POA
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FurtherStudies?
• Howdoesthepoorac(vityinvitro translateintosterilizingeffectin‐vivo?
Tissuelevels?
Synergismwithinflammatoryresponse?Promo(ngaccumula(onintothe bacilli
andorimprovedkilling?
Be`erinduc(onofcellularimmunity