Lecture 38Lecture 38PlantibodiesPlantibodies

ANTIBODIES PRODUCED FROM PLANTS

• Functional antibodies can be produced from plants

• Targeted to intercellular space, chloroplast, seeds and tubers

• Benefit for topical immunotherapy

• Can be produced from plants in large quantities

Contd...

• Plantibodies provides increased stability

e.g: Secretory Ig A

• Plants can assemble complex secretory antibodies

e.g: Construction of tobacco plants expressing 4 transgenes

• Quadruple transgenics efficiently assembled secretory immunoglobulins

(Smith & Glick, 2000)

Anti-rabies virus mAbAnti-rabies virus mAb

After exposure treated with AbAfter exposure treated with Ab

Used to be made in horsesUsed to be made in horses

First mAb made in transgenic plantsFirst mAb made in transgenic plants

4 genes – 2 H, 2 L4 genes – 2 H, 2 L

Transgenic plant for each one and Transgenic plant for each one and crossing plantscrossing plants

Later used single binary vector with two Later used single binary vector with two promoters promoters

Full-size monoclonal antibodies recently produced Full-size monoclonal antibodies recently produced in transgenic plantsin transgenic plants

Abs expressed in transgenic Abs expressed in transgenic plantsplants

Variable Light chain

Variable Heavy chain

Recombinant hinge region

Constant domains

Functional AbsFunctional Abs

Need to be properly folded and assembledNeed to be properly folded and assembledNeed disulfide bond formation and glycosylationNeed disulfide bond formation and glycosylationDown stream processing:Down stream processing:

Purification of Ab mostly with Protein A or Purification of Ab mostly with Protein A or GG

Glycosylation is different in plantsGlycosylation is different in plantsβ β 1,2 Xylose and 1,2 Xylose and α α 1,3 fucose1,3 fucose

Retain in ER, only mannose is attachedRetain in ER, only mannose is attached–Shorter half-life of Ab Shorter half-life of Ab

Glycosylation of AbGlycosylation of Ab

Full-size AbLarge single-chain Ab Camelid heavy-chain Ab

Minibodies and Fab fragments don’t get glycosylated

Glycosylation in GolgiGlycosylation in Golgi

Antibodies: a compelling success storyAntibodies: a compelling success story

high specificity: in vitro and in vivo diagnostics

low toxicity: therapeutic applications

high drug approval rates (24 approved mAbs)

major products in biotechnology (~240 in clinical

trials)

inherently stable human proteins

injectable, topical and oral applications

applicable for chronic conditions

potential long-lasting benefits

Production Costs for AntibodiesProduction Costs for AntibodiesProduction costs cost in $ / gram

hybridomas 1000

transgenic animals 100

transgenic plants 10

Source: Daniell et al. (2001) TIPS 6, 219-226

E. coli & yeast Tr. animals andanimal cells

Transgenicplants

Comparison of Mammalian and Plant-produced Comparison of Mammalian and Plant-produced AntibodiesAntibodies

peptide sequence: identicalpeptide sequence: identical

correct cleavage of Ig-derived signal peptides correct cleavage of Ig-derived signal peptides

kinetics & affinity: identical kinetics & affinity: identical

stability in seeds > 30 monthsstability in seeds > 30 months

antibody types: plant system more versatile (sIgA)antibody types: plant system more versatile (sIgA)

post-translational processing: differentpost-translational processing: different

core glycan identical, terminal sugar different plus xylose & fucosecore glycan identical, terminal sugar different plus xylose & fucose

antigenicity & clearance: apparently identical (shorter half-life)antigenicity & clearance: apparently identical (shorter half-life)