The eukaryotic green algae, Chlamydomonas reinhardtii has been shown to be capable of producing a variety of
recombinant proteins, but the true potential of this platform remains largely unexplored. To assess the potential of algae for the production of novel
recombinant proteins, we generated a series of chimeric
proteins containing a single chain antibody (scFv) targeting the B-
cell surface antigen CD22, genetically fused to the eukaryotic
ribosome inactivating protein,
gelonin, from Gelonium multiflorm. These unique molecules, termed
immunotoxins, are encoded as a single gene that produces an antibody--
toxin chimeric protein capable of delivering a cytotoxic molecule to targeted B-cells. We show that the addition of an Fc domain of a human
IgG1 to these fusion
proteins results in the production of assembled dimeric
immunotoxins, containing two cell binding scFvs and two
gelonin molecules. Additionally, we demonstrate that these algal expressed
proteins are capable of binding and reducing the viability of
B-cell lymphomas, while treatment of T-cells, that lack the
CD22 antigen, had no impact on cell viability. Since other
protein expression platforms are incapable of folding and accumulating these complex
immunotoxins as soluble and enzymatically active
proteins, our studies document a novel and efficient method for
immunotoxin production.