title: Recombinant plant-expressed tumour-associated MUC1 peptide is immunogenic and capable of breaking tolerance in MUC1.Tg mice.
abstract: The human epithelial mucin MUC1 is a heavily glycosylated transmembrane protein that is overexpressed and aberrantly glycosylated on over 90% of human breast cancers. The altered glycosylation of MUC1 reveals an immunodominant peptide along its tandem repeat (TR) that has been used as a target for tumour immunotherapy. In this study, we used the MUC1 TR peptide as a test antigen to determine whether a plant-expressed human tumour-associated antigen can be successfully expressed in a plant system and whether it will be able to break self-antigen tolerance in a MUC1-tolerant mouse model. We report the expression of MUC1 TR peptide fused to the mucosal-targeting Escherichia coli enterotoxin B subunit (LTB-MUC1) in a plant host. Utilizing a rapid viral replicon transient expression system, we obtained high yields of LTB-MUC1. Importantly, the LTB-MUC1 fusion protein displayed post-translational modifications that affected its antigenicity. Glycan analysis revealed that LTB-MUC1 was glycosylated and a MUC1-specific monoclonal antibody detected only the glycosylated forms. A thorough saccharide analysis revealed that the glycans are tri-arabinans linked to hydroxyprolines within the MUC1 tandem repeat sequence. We immunized MUC1-tolerant mice (MUC1.Tg) with transiently expressed LTB-MUC1, and observed production of anti-MUC1 serum antibodies, indicating breach of tolerance. The results indicate that a plant-derived human tumour-associated antigen is equivalent to the human antigen in the context of immune recognition.
authors: The Biodesign Institute and School of Life Sciences, Arizona State University, Tempe, AZ, USA.
authors: Julia
authors: J
authors: Pinkhasov
authors: M Lucrecia
authors: ML
authors: Alvarez
authors: M Manuela
authors: MM
authors: Rigano
authors: Khanrat
authors: K
authors: Piensook
authors: Dalia
authors: D
authors: Larios
authors: Martin
authors: M
authors: Pabst
authors: Josephine
authors: J
authors: Grass
authors: Pinku
authors: P
authors: Mukherjee
authors: Sandra J
authors: SJ
authors: Gendler
authors: Amanda M
authors: AM
authors: Walmsley
authors: Hugh S
authors: HS
authors: Mason
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000912:Antibodies, Neoplasm / Q000097:blood / Q000276:immunology; D001427:Bacterial Toxins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D019496:Cancer Vaccines / Q000276:immunology*; D004768:Enterotoxins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D005260:Female; D005822:Genetic Vectors / Q000235:genetics / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D007108:Immune Tolerance; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D008325:Mammary Neoplasms, Experimental / Q000276:immunology; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D018396:Mucin-1 / Q000276:immunology*; D010446:Peptide Fragments / Q000276:immunology*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000276:immunology*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014170:Transformation, Genetic
chemical_list: D000912:Antibodies, Neoplasm; D001427:Bacterial Toxins; D019496:Cancer Vaccines; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D007074:Immunoglobulin G; C116055:MUC1 tandem repeat peptide; D018396:Mucin-1; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C027538:heat-labile enterotoxin, E coli