lect 1 viral vaccines general principles kousoulas 030107

8/8/2019 Lect 1 Viral Vaccines General Principles Kousoulas 030107

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Three major sites for viral replication

Mucosal surfaces of respiratory tract and GI tract.Rhino; myxo; corona; parainfluenza; respiratorysyncytial; rota

Infection at mucosal surfaces followed by spread

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systemically via blood and/or neurones to target organs:picorna; measles; mumps; HSV; varicella; hepatitis Aand B

Direct infection of blood stream via needle or bites andthen spread to target organs: hepatitis B; alpha; flavi;bunya; rhabdo

Local immunity via IgA very important in 1 and 2.

Virus infection

Type of virusNature of virus

Routes of infection

OralNasal

Host

AgeRace

Immune mechanisms against viral infection

IntradermalParenteralSexual

.Immune statusHealth conditionNutritional cond.

Nature of responses

Type of responses Level of responses


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Figure 12-7

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Anthrax Killed bacteria

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Current licensed vaccines

Virus Serotypes Live Inactivated Doses Injection Attenuation

Adenovirus 2,4,7 + 1 OralJapanese enc. 1 + 2 P BHKMeasles 1 + 1+R P CEMumps 1 + 1 P CEPolio 1,2,3 + 1 O MKC

Rotavirus 1,2,3,4 + 3 O Reassortant RRVSmallpox 1 + 1 ID Natural JennerVarizella 1 + 1 P MKCYellow fever 1 + 1 P CE

Hepatitis A 1 + 2 PHepatitis B 1 VLP 3 PInfluenza A,B + 1 PJapanese enc. 1 + 3+R PPolio 1,2,3 + 2 PRabies 1 + x PTick-borne enc. 1 + 2+R P


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VIRAL VACCINESVIRAL VACCINES

TheThe developmentdevelopment ofof antiviralantiviral vaccinesvaccines isis highlyhighly dependentdependent uponupon thethe infectioninfection cyclecycle ofof thethe viralviralpathogenpathogen itselfitself..

VirusesViruses thatthat havehave anan extracellular,extracellular, viremicviremic stagestage inin thethe infectioninfection cyclecycle areare accessibleaccessible toto solublesolublehumoralhumoral componentscomponents areare susceptiblesusceptible toto antibodiesantibodies..

VirusesViruses thatthat areare highlyhighly cellcell associated,associated, eithereither throughthrough theirtheir abilityability toto transporttransport directlydirectly fromfrom oneoneinfectedinfected cellcell toto anan adjacentadjacent susceptiblesusceptible hosthost cell,cell, oror havehave aa cellcell--associatedassociated viremicviremic stage,stage, areare notnotaccessibleaccessible toto humoralhumoral componentscomponents requirerequire directdirect recognitionrecognition ofof infectedinfected cellscells implicatesimplicates TT cellcellresponsesresponses..

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TheThe basisbasis forfor successfulsuccessful vaccinationvaccination isis thethe generationgeneration ofof aa longlong--termterm protectiveprotective acquiredacquired immuneimmuneresponseresponse requiresrequires aa knowledgeknowledge ofof howhow immunologicalimmunological memorymemory developsdevelops andand howhow thisthis cancan bebebestbest implementedimplemented..

ThereThere areare manymany differentdifferent methodsmethods thatthat cancan bebe usedused toto vaccinatevaccinate susceptiblesusceptible individualsindividuals liveliveattenuatedattenuated viruses,viruses, inactivatedinactivated oror killedkilled viruses,viruses, virusvirus--likelike particles,particles, plasmidplasmid DNA,DNA, individualindividual viralviralcomponents,components, recombinantrecombinant virus,virus, pseudovirus,pseudovirus, repliconreplicon eacheach approachapproach hashas itsits advantagesadvantages andanddisadvantagesdisadvantages..

TheThe useuse ofof nonnon--replicatingreplicating immunogensimmunogens asas vaccinesvaccines oftenoften requiresrequires thethe useuse ofof adjuvantsadjuvants totooptimizeoptimize thethe subsequentsubsequent immuneimmune responseresponse..

ImmunizationImmunization cancan stillstill resultresult inin immuneimmune escapeescape variantsvariants..

VACCINE DESIGNSVACCINE DESIGNSApproachApproach PurposePurpose

Vectored vaccinesVe ct or ed va cc ine s To e mp loy a n a tt enu ate d v ir us or b ac te ri um w it hTo employ an attenuated virus or bacterium withlimited replication potential to carry a gene orlimited replication potential to carry a gene orgenes for antigens from a pathogen into thegenes for antigens from a pathogen into thebodybody

Nucleic acid vaccinesN uc le ic ac id va cc ine s To us e a pl as mi d c on ta in in g ge ne s c od ing fo rTo use a plasmid containing genes coding forone or more antigens from a pathogen so thatone or more antigens from a pathogen so thatthe body itself becomes a factory for thethe body itself becomes a factory for theantigen(s) in question; there are variations onantigen(s) in question; there are variations onthis themethis theme

Pe tide vaccinesPe tide vaccines To construct a ol m er out of anumber ofToconst ruct a ol meroutof anumber of

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peptides, frequently T cell epitopes, therebypeptides, frequently T cell epitopes, therebycreating an immunogencreating an immunogen

Mucosal vaccinesMucosal vaccines To administer an antigen not by injection butTo administer an antigen not by injection butthrough a mucosal surface (e.g., orally orthrough a mucosal surface (e.g., orally orintranasally), so as to engage the mucosalintranasally), so as to engage the mucosalimmune system in protectionimmune system in protection

Transdermal vaccinesTr ans de rm al va cc in es To ad mi ni st er the an ti ge n t hr ou gh th e s ki nTo administer the antigen through the skin

Edible vaccinesEdible vacc ines To ge netically engineer a plant so that it come sTo genetically engineer a plant so that it comesto contain antigens in a form that isto contain antigens in a form that isimmunogenic when eatenimmunogenic when eaten

PrimePrime--boost strategiesb oo st s tr at eg ies To adm in is te r t wo sep ar at e ver si on s o f a vacci neTo administer two separate versions of a vaccinesequentially, typically a DNA vaccine followed bysequentially, typically a DNA vaccine followed bya vectored vaccine, or either of these followed bya vectored vaccine, or either of these followed bya protein vaccinea protein vaccine


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Optimization of Vaccines ~Optimization of Vaccines ~AdjuvantsAdjuvants

TheThe naturenature ofof vaccinevaccine designdesign maymay resultresult inin suboptimalsuboptimal generationgeneration ofof immuneimmune responsesresponses duedue totolowlow immunogenicity,immunogenicity, oror suboptimalsuboptimal presentationpresentation toto APCsAPCs thisthis cancan bebe amelioratedameliorated byby thethe useuse ofofadjuvantsadjuvants oror byby designingdesigning vaccinesvaccines thatthat specificallyspecifically targettarget APCsAPCs..

UptakeUptake ofof antigensantigens byby APCsAPCs isis vitalvital;; hence,hence, renderingrendering antigensantigens polymericpolymeric oror particulateparticulate helpshelps.. ActivationActivation ofofAPCsAPCs isis essentialessential;; hence,hence, agentsagents thatthat engageengage TLRTLR workwork wellwell.. ii i ii i ii

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epotepot e ectse ects andand de ayeddeayed absorpt onabsorpt on cancan enhanceenhance mmuntymmunty;; hence,hence, emus onsemusons andandbiodegradablebiodegradable microparticlesmicroparticles underlieunderlie manymany adjuvantadjuvant approachesapproaches..

ManyMany cytokinescytokines increaseincrease immuneimmune responsesresponses.. MolecularMolecular targetingtargeting ofof antigensantigens toto APCsAPCs throughthrough conjugationconjugation ofof ligandsligands cancan enhanceenhance immuneimmune

responsesresponses..

TargetingTargeting toto dendriticdendritic cellscells (DC)(DC) specificallyspecifically isis likelylikely toto bebe importantimportant forfor antiviralantiviral vaccinevaccinedevelopmentdevelopment..

Priming entityPriming entity Boosting entityBoosting entity

Some Examples of PrimeSome Examples of Prime--boostboostStrategiesStrategies

OptimizationOptimization ofof vaccinationvaccinationcancanbebe achievedachieved byby differentdifferent combinationscombinationsofof primingprimingandand boostingboosting thethe tabletablebelowbelowgivesgivesanan overviewoverview ofofsomesome ofofthetheapproachesapproachesthatthatcancanbebeusedused..

TheTheuseuse ofof differentdifferent primeprime--boostboost strategiesstrategies cancan bebe usedused toto overcomeovercome thethe possiblepossible reductionreduction ofof thetheefficacyefficacyofofthetheboostboostphasephasedueduetoto aaprepre--existingexisting neutralizingneutralizingantibodyantibodyresponseresponse generatedgeneratedduringduringprimingpriming thisthis existingexisting antibodyantibody responseresponse maymayremoveremove thethe boostingboosting phasephasebeforebeforefurtherfurther activationactivation takestakesplaceplace ififthethesamesameentityentityisisusedused ininbothbothphasesphases..

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Viral vectorViral vector Recombinant proteinRecombinant protein

Naked DNANaked DNA Recombinant proteinRecombinant protein

Naked DNANaked DNA Viral vectorViral vector

Viral vectorViral vector Naked DNA*Naked DNA*

Viral vectorViral vector Different viral vectorDifferent viral vector

** Not very effectiveNot very effective

The Ultimate Goal of a Vaccine is to Have Long-lasting Immunity

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Efficacyantibody attenuated> killed> subunit> DNAcytotoxic T cells attenuated> DNA> killed> subunit

Tradeoffs in vaccine design

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Safety subunit> killed> DNA> attenuated(biological)

Toxicity attenuated> killed> DNA> subunit(inflammation)

Vaccines Problems(why vaccines may not work)

Different viruses may cause similar disease--e.g. common

cold

Antigenic drift and shift -- especially true of RNA viruses

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and those with segmented genomesShift: reassortment of segmented genomes (flu

A but not rota or flu B)

Drift: rapid mutation - retroviruses

Large animal reservoirs - Reinfection may occur

Vaccines - Problems

Integration of viral DNA. Vaccines will not work onlatent virions unless they express antigens on cell

surface. In addition if vaccine virus inte rates it ma

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cause problems (herpes, parvovirus, etc).

Transmission from cell to cell via syncytia

Recombination of the virulent strain or of the vaccine

virus


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DNA Vaccines

Muscle cell

Gene forantigen

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Muscle cell expressesprotein - antibody made

CTL response

DNA Vaccines Plasmids are easily manufactured in large amounts

DNA is very stable

DNA resists temperature extremes so storage and transport are straightforward

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DNA sequence can be changed easily in the laboratory. This means thatwe can respond to changes in the infectious agent

By using the plasmid to code for antigen synthesis, the antigenicprotein(s) that are produced are processed (post-translationally modified)in the same way as the proteins of the virus against which protection is tobe produced. This makes a far better antigen than purifying that proteinand using it as an immunogen.

DNA Vaccines

Mixtures of plasmids could be used that encode many proteinfragments from a virus/viruses so that a broad spectrum vaccine couldbe produced

The plasmid does not replicate and encodes only the proteins of

interest

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No protein component so there will be no immune response againstthe vector itself

Because of the way the antigen is presented, there is a CTL responsethat may be directed against any antigen in the pathogen. A CTLresponse also offers protection against diseases caused by certainobligate intracellular pathogens (e.g. Mycobacterium tuberculosis)


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DNA Vaccines

Possible Problems

Potential integration of plasmid into host genomeleading to insertional mutagenesis

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Induction of autoimmune responses (e.g. pathogenicanti-DNA antibodies)

Induction of immunologic tolerance (e.g. where theexpression of the antigen in the host may lead to specificnon-responsiveness to that antigen)

DNA Vaccines

DNA vaccines produce a situation that reproduces a virally-

infected cell

Gives:

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Broad based immune response

Long lasting CTL response

Advantage of new DNA vaccine for flu:

CTL response can be against internal protein

In mice a nucleoprotein DNA vaccine is effective against a range of viruses

with different hemagglutinins

Virus-Host Interactions:Evasion of Cellular Defense Mechanisms

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Evasion of Host Immune Responses

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lect 1 viral vaccines general principles kousoulas 030107

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