title: Control of established colon cancer xenografts using a novel humanized single chain antibody-streptococcal superantigen fusion protein targeting the 5T4 oncofetal antigen.
abstract: Superantigens (SAgs) are microbial toxins that cross-link T cell receptors with major histocompatibility class II (MHC-II) molecules leading to the activation of large numbers of T cells. Herein, we describe the development and preclinical testing of a novel tumor-targeted SAg (TTS) therapeutic built using the streptococcal pyrogenic exotoxin C (SpeC) SAg and targeting cancer cells expressing the 5T4 tumor-associated antigen (TAA). To inhibit potentially harmful widespread immune cell activation, a SpeC mutation within the high-affinity MHC-II binding interface was generated (SpeCD203A) that demonstrated a pronounced reduction in mitogenic activity, yet this mutant could still induce immune cell-mediated cancer cell death in vitro. To target 5T4+ cancer cells, we engineered a humanized single chain variable fragment (scFv) antibody to recognize 5T4 (scFv5T4). Specific targeting of scFv5T4 was verified. SpeCD203A fused to scFv5T4 maintained the ability to activate and induce immune cell-mediated cytotoxicity of colorectal cancer cells. Using a xenograft model of established human colon cancer, we demonstrated that the SpeC-based TTS was able to control the growth and spread of large tumors in vivo. This required both TAA targeting by scFv5T4 and functional SAg activity. These studies lay the foundation for the development of streptococcal SAgs as 'next-generation' TTSs for cancer immunotherapy.
authors.affiliation: Department of Microbiology and Immunology, Western University, London, Ontario, Canada.
authors.forename: Kelcey G
authors.initials: KG
authors.lastname: Patterson
authors.affiliation: Department of Microbiology and Immunology, Western University, London, Ontario, Canada.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Dixon Pittaro
authors.affiliation: Department of Microbiology and Immunology, Western University, London, Ontario, Canada.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Bastedo
authors.affiliation: Department of Physiology and Pharmacology, Western University, London Ontario, Canada; Vascular Biology Research Group, Robarts Research Institute, London, Ontario, Canada.
authors.forename: David A
authors.initials: DA
authors.lastname: Hess
authors.affiliation: Department of Microbiology and Immunology, Western University, London, Ontario, Canada; Centre for Human Immunology, Western University, London, Ontario, Canada; Lawson Health Research Institute, London, Ontario, Canada.
authors.forename: S M Mansour
authors.initials: SM
authors.lastname: Haeryfar
authors.affiliation: Department of Microbiology and Immunology, Western University, London, Ontario, Canada; Centre for Human Immunology, Western University, London, Ontario, Canada; Lawson Health Research Institute, London, Ontario, Canada.
authors.forename: John K
authors.initials: JK
authors.lastname: McCormick
mesh_terms: D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000235:genetics / Q000276:immunology*; D000951:Antigens, Neoplasm / Q000276:immunology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D003110:Colonic Neoplasms / Q000276:immunology / Q000473:pathology* / Q000628:therapy; D006801:Humans; D007167:Immunotherapy / Q000379:methods*; D051379:Mice; D008958:Models, Molecular; D011487:Protein Conformation; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology*; D057127:Single-Chain Antibodies / Q000235:genetics / Q000276:immunology; D013291:Streptococcus / Q000276:immunology*; D018089:Superantigens / Q000235:genetics / Q000276:immunology*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D000951:Antigens, Neoplasm; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins; D057127:Single-Chain Antibodies; D018089:Superantigens; C031192:oncofetal antigens
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