Oral delivery of bioencapsulated proteins across blood-brain and blood-retinal barriers

Mol Ther. 2014 Mar;22(3):535-546. doi: 10.1038/mt.2013.273. Epub 2013 Dec 6.


Delivering neurotherapeutics to target brain-associated diseases is a major challenge. Therefore, we investigated oral delivery of green fluorescence protein (GFP) or myelin basic protein (MBP) fused with the transmucosal carrier cholera toxin B subunit (CTB), expressed in chloroplasts (bioencapsulated within plant cells) to the brain and retinae of triple transgenic Alzheimer's disease (3×TgAD) mice, across the blood-brain barriers (BBB) and blood-retinal barriers (BRB). Human neuroblastoma cells internalized GFP when incubated with CTB-GFP but not with GFP alone. Oral delivery of CTB-MBP in healthy and 3×TgAD mice shows increased MBP levels in different regions of the brain, crossing intact BBB. Thioflavin S-stained amyloid plaque intensity was reduced up to 60% by CTB-MBP incubation with human AD and 3×TgAD mice brain sections ex vivo. Amyloid loads were reduced in vivo by 70% in hippocampus and cortex brain regions of 3×TgAD mice fed with bioencapsulated CTB-MBP, along with reduction in the ratio of insoluble amyloid β 42 (Aβ42) to soluble fractions. CTB-MBP oral delivery reduced Aβ42 accumulation in retinae and prevented loss of retinal ganglion cells in 3×TgAD mice. Lyophilization of leaves increased CTB-MBP concentration by 17-fold and stabilized it during long-term storage in capsules, facilitating low-cost oral delivery of therapeutic proteins across the BBB and BRB.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Administration, Oral
  • Alzheimer Disease / drug therapy*
  • Alzheimer Disease / pathology
  • Animals
  • Blood-Brain Barrier / metabolism*
  • Blood-Retinal Barrier / metabolism*
  • Capsules
  • Cell Line, Tumor
  • Chloroplasts / metabolism*
  • Cholera Toxin / genetics
  • Cholera Toxin / metabolism*
  • Disease Models, Animal
  • Female
  • Humans
  • In Vitro Techniques
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Myelin Basic Protein / genetics
  • Myelin Basic Protein / metabolism*
  • Plant Leaves / cytology
  • Plaque, Amyloid / drug therapy*
  • Plaque, Amyloid / pathology
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism


  • Capsules
  • Myelin Basic Protein
  • Recombinant Fusion Proteins
  • Cholera Toxin