title: Production of unique immunotoxin cancer therapeutics in algal chloroplasts.
abstract: The idea of targeted therapy, whereby drug or protein molecules are delivered to specific cells, is a compelling approach to treating disease. Immunotoxins are one such targeted therapeutic, consisting of an antibody domain for binding target cells and molecules of a toxin that inhibits the proliferation of the targeted cell. One major hurdle preventing these therapies from reaching the market has been the lack of a suitable production platform that allows the cost-effective production of these highly complex molecules. The chloroplast of the green alga Chlamydomonas reinhardtii has been shown to contain the machinery necessary to fold and assemble complex eukaryotic proteins. However, the translational apparatus of chloroplasts resembles that of a prokaryote, allowing them to accumulate eukaryotic toxins that otherwise would kill a eukaryotic host. Here we show expression and accumulation of monomeric and dimeric immunotoxin proteins in algal chloroplasts. These fusion proteins contain an antibody domain targeting CD22, a B-cell surface epitope, and the enzymatic domain of exotoxin A from Pseudomonas aeruginosa. We demonstrated that algal-produced immunotoxins accumulate as soluble and enzymatically active proteins that bind target B cells and efficiently kill them in vitro. We also show that treatment with either the mono- or dimeric immunotoxins significantly prolongs the survival of mice with implanted human B-cell tumors.
authors.affiliation: The San Diego Center for Algae Biotechnology and Department of Biology, University of California at San Diego, La Jolla, CA, USA.
authors.forename: Miller
authors.initials: M
authors.lastname: Tran
authors.forename: Christina
authors.initials: C
authors.lastname: Van
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Barrera
authors.forename: Pär L
authors.initials: PL
authors.lastname: Pettersson
authors.forename: Carlos D
authors.initials: CD
authors.lastname: Peinado
authors.forename: Jack
authors.initials: J
authors.lastname: Bui
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Mayfield
mesh_terms: D000818:Animals; D015153:Blotting, Western; D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D002850:Chromatography, Gel; D004268:DNA-Binding Proteins / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005434:Flow Cytometry; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D000922:Immunotoxins / Q000302:isolation & purification* / Q000494:pharmacology*; D008223:Lymphoma / Q000188:drug therapy*; D051379:Mice; D018345:Mice, Knockout; D030781:Organisms, Genetically Modified; D015202:Protein Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000378:metabolism; D014170:Transformation, Genetic; D014183:Transplantation, Heterologous
chemical_list: D004268:DNA-Binding Proteins; D000922:Immunotoxins; C499308:Rag2 protein, mouse; D011994:Recombinant Proteins