Agriculture Reference
In-Depth Information
risk.of.product.exposure.to.herbivores.and.other.nontarget.organisms..On.the.other.
hand,.however,.the.necessity.of.pollination.for.seed.formation.presents.a.new.risk.for.
potential.transgene.escape.into.the.environment.
Maize.was.one.of.the.irst.seed.crops.used.for.recombinant.protein.production. 237 .
Compared.with.other.cereal.plants,.it.has.several.advantages.including.high.biomass.
yield,.ease.of.transformation,.and.the.availability.of.large-scale.processing.technol-
ogy..Since.maize.has.been.a.model.plant.for.genetic.studies,.there.is.a.vast.genetic.
and. molecular. knowledge. base. available. for. its. genetic. manipulation.. Maize. has.
been.a.successful.seed.crop.for.producing.a.variety.of.recombinant.proteins.includ-
ing.mAbs,.biotech.reagents,.even.commercial.grade.b-glucuronidase.and.avidin. 10 .For.
example,.mAb.(2G12),.a.promising.anti-HIV.microbicide.candidate,.was.produced.
in.transgenic.maize. 64 .This.research.showed.that.maize-produced.mAb.neutralized.
HIV.as.effectively.as.the.same.antibody.produced.in.Chinese.hamster.ovary.(CHO).
cells.. Despite. these. advantages,. disastrous. transgene. outlow. incidents. happened.
in.this.crop. have. raised. serious.regulatory.and. public.concerns. on. using.maize.or.
other.food.crops.for.recombinant.protein.production.(see.“Regulatory.Concerns.and.
Public.Acceptance”.section.of.this.chapter)..A.comparative.study.was.conducted.to.
examine.the.yield.of.a.scFv.in.different.seed.and.leafy.crops.including.wheat,.rice,.
pea,.and.tobacco..Results.showed.that.the.target.protein.yield.per.unit.of.biomass.was.
in.the.order.of.rice.seeds.>.tobacco.leaf.>.wheat.seeds.=.pea.seeds. 234 .The.highest.
yield.per.unit.of.land,.however,.belongs.to.tobacco.plants.because.of.its.high.biomass.
production.. Since. different. promoters. were. used. for. seed. and. leaf. expression,. the.
results.have.to.be.evaluated.with.caution.and.need.further.validation..This.study.did.
demonstrate.that.choosing.a.optimal.production.crop.was.relying.on.multiple.factors.
such.as.target.protein.yield.per.unit.biomass.and.biomass.yield.per.acre.and.can.be.
only.determined.on.a.protein-by-protein.basis.
f ruIt and t uber c ropS
Pharmaceutical.protein.production.in.fruit.and.tuber.crops.provides.the.opportunity.for.
a.novel.approach.of.pharmaceutical.delivery.through.oral.route.by.ingesting.palatable.
crop.organs..This.unique.advantage.makes.them.ideal.hosts.for.the.production.of.oral.
vaccines.or.topical.therapeutics..For.example,.potato.plants.have.been.explored.as.one.
of.the.earliest.plant.systems.for.expression.of.a.diversity.of.vaccines. 81,238,239 .Our.group.
and.others.also.conducted.at.least.three.clinical.trials.by.administering.uncooked.trans-
genic.potato.tubers.expressing.exterotoxic. E. coli .LT-B.or.VLPs.of.NVCP.to.human.
volunteers..Fruits.such.as.tomatoes.and.strawberries.are.more.edible.than.raw.potatoes.
and.thus.are.more.feasible.for.edible.vaccine.development..Tomatoes.have.been.used.
for.both.vaccine.and.therapeutic.mAb.expression.due.to.its.high.biomass.yield.and.ease.
of.production.in.greenhouses.for.transgene.containment. 240 .Bananas.have.been.envi-
sioned.for.a.long.time.as.hosts.for.edible.vaccine.production.and.delivery.especially.in.
Africa.where.vaccination.for.infectious.diseases.is.urgently.needed..However,.dificul-
ties.in.generating.transgenic.banana.plants.and.the.long.time.frame.needed.to.grow.
fruit-bearing.crops.still.present.hurdles.for.its.practical.application..Since.fruits.and.
edible.tubers.are.food.crops,.one.of.the.biggest.obstacles.for.their.commercialization.is.
the.regulatory.and.public.concern.for.biosafety.and.transgene.containment.
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