Expression and Manufacture of Pharmaceutical Proteins in Genetically Engineered Horticultural Plants - Transgenic Horticultural Crops: Challenges and Opportunities - page 99

acid.protein.A.fragment,.has.also.been.developed.recently..These.nanoparticles.can.
be.produced.at.high.levels.in.plants,.and.the.density.of.the.Protein.A.fragment.on.the.
nanoparticle.is.high,.satisfying.the.matrices.of.high.mAb-binding.capacity.and.low-
cost.economics.required.for.a.successful.processing.technology..A.simple.mAb.puri-
ication.process.can.be.performed.with.these.plant-derived.nanoparticles.to.achieve.
>90%.product.purity. 145
In. addition. to. protein. A,. many. conventional. chromatographic. resins. have. been.
investigated.for.mAb.puriication..These.resins.are.less.expensive,.easier.to.scale.up,.
and.more.resistant.to.chemical.and.biological.degradations.and,.therefore,.are.more.
suitable.for.industrial.manufacturing..It.was.showed.that.a.simple.S-Sepharose.
FF.cation.exchange.chromatography.followed.by.immobilized.metal.afinity.chro-
matography.(IMAC).on.Zn-iminodiacetic.acid.(IDA)-agarose.can.eficiently.purify.
an.anti-HIV.mAB.(2G12).from.corn.seeds.with.90%.purity. 64 .Histamine.Sepharose.
was.also.used.as.an.afinity.resin.in.purifying.mAbs.from.plant.extracts. 143 .A.>95%.
purity.of.a.mAb.can.be.achieved.by.this.resin.in.a.single.puriication.step.when.used.
with.a.maize.seed.extract..When.the.same.resin.was.used.to.purity.the.mAb.from.
tobacco.leaf.extracts,.however,.the.binding.capacity.and.the.puriication.eficiency.
were. slightly. reduced. due. to. the. interference. of. tobacco-speciic. phenolics,. alka-
loids,.and.host.proteins. 143
“Pseudobiospeciic. ligands”. represent. another. class. of. non-Protein. A. resins.
for. mAb. puriication.. They. include. biologically. engineered. peptides. and. protein.
domains.as.well.as.synthetic.mimetics.exhibiting.different.degree.afinity.to.anti-
bodies..Comparative.studies.showed.that.the.mAb.afinity.of.these.ligands.(includ-
ing.hydrophobic,.thiophilic,.hydroxyapatite,.chelating.metal.ions,.and.mixed.mode.
afinity.ligands).is.generally.lower.than.that.of.Protein.A,.but.high.enough.for.mAb.
selectivity. 164 .Overall,.under.optimized.conditions,.the.mAb-binding.speciicity.and.
capacity.of.these.resins.are.comparable.to.those.of.the.Protein.A,.but.vary.depend-
ing.on.the.source.and.the.isotype.of.mAbs. 165-167 .Advantages.of.pseudobiospeciic.
ligands.include.reduced.cost.of.production,.mild.elution.condition,.facile.steriliza-
tion. and. validation,. resistance. to. chemical. and. biological. degradation,. and. lower.
toxicity,.all.of.which.makes.them.favorable.as.large-scale.mAb.puriication.alterna-
tives.. Furthermore,. chemical.modiications.allow.these.afinity. ligands. to. acquire.
new.afinities.to.mAb-derivatives.that.traditional.Protein.A.lacks,.therefore.broad-
ening.the.range.of.application..For.example,.artiicial. PpL.is.able.to.purify.a.Fab.
to. >90%. purity. with. 77%. recovery. 168 . MEP. Hypercel,. IDA-Ni,. epitope. peptides,.
Mabsorbent,. afibodies,. and. artiicial.Protein.A.are.some. examples. of.pseudobio-
specifc.ligands. 146 .Not.all.artiicial.afinity.ligands.have.been.tested.for.plant-derived.
mAb.puriication..However,.there.is.no.doubt.that.they.will.contribute.substantially.
to.the.development.of.economical.Protein.A.alternatives.for.large-scale.manufactur-
ing.of.plant-derived.mAbs.
For. puriication. of. non-mAb-based. vaccines. and. therapeutics,. there. are. no.
platforms. based. on. a. universal. afinity. resin. equivalent. to. Protein. A.. Usually,.
the.puriication.is.carried.out.by.multiple.steps.of.conventional.chromatographic.
methods.and.has.to.be.developed.individually.based.on.the.properties.such.as.the.
pI,. size,. hydrophobicity,. and. stability. of. the. target. protein. and. the. contaminat-
ing.host.molecules. 142 .This.time-consuming.and.challenging.process.calls.for.the.