title: Intracellular Cleavable CpG Oligodeoxynucleotide-Antigen Conjugate Enhances Anti-tumor Immunity.
abstract: Conjugation of a vaccine adjuvant to an antigen enhances anti-tumor immune responses. Direct chemical conjugation, however, may limit their processing by the antigen-presenting cell for immune stimulation. To test this hypothesis, antigen-adjuvant conjugates were designed to be cleaved by an intracellular trigger to release antigen and adjuvant from each other. The different reductive environment inside and outside antigen-presenting cells was used as a trigger for targeted intracellular release. Two redox-responsive disulphide linkers were used to conjugate the model antigen ovalbumin to CpG. In vitro stability assays with the reductant glutathione showed that one conjugate (SS) was cleaved by glutathione concentrations of the extra- and intracellular compartments. A second conjugate (HYN-SS) was only cleaved at the higher intracellular glutathione concentration. In vitro cell culture studies showed that high T cell responses were generated by the HYN-SS and the stable conjugate HYN. The SS conjugate induced a lower T cell response similar to a mixture of CpG and ovalbumin. An in vivo therapeutic tumor trial demonstrated a superior survival rate of 9/10 for mice vaccinated with HYN-SS conjugate compared to HYN (6/10), SS (2/10), and the mixture (2/10). This intracellular cleavable conjugation strategy represents a promising approach to improve cancer immunotherapy of soluble vaccines.
authors.affiliation: School of Pharmacy, University of Otago, Dunedin 9016, New Zealand; Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin 9016, New Zealand.
authors.forename: Katrin
authors.initials: K
authors.lastname: Kramer
authors.affiliation: Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin 9016, New Zealand.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Shields
authors.affiliation: School of Pharmacy, University of Otago, Dunedin 9016, New Zealand.
authors.forename: Viola
authors.initials: V
authors.lastname: Poppe
authors.affiliation: Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin 9016, New Zealand. Electronic address: sarah.young@otago.ac.nz.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Young
authors.affiliation: School of Pharmacy, University of Otago, Dunedin 9016, New Zealand.
authors.forename: Greg F
authors.initials: GF
authors.lastname: Walker
mesh_terms: D000276:Adjuvants, Immunologic / Q000737:chemistry; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism; D000941:Antigens / Q000276:immunology*; D019496:Cancer Vaccines / Q000276:immunology*; D004195:Disease Models, Animal; D008546:Melanoma, Experimental; D051379:Mice; D009369:Neoplasms / Q000276:immunology* / Q000401:mortality / Q000473:pathology / Q000628:therapy; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D010047:Ovalbumin / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism
chemical_list: D000276:Adjuvants, Immunologic; D000941:Antigens; C408982:CPG-oligonucleotide; D019496:Cancer Vaccines; D009838:Oligodeoxyribonucleotides; D010047:Ovalbumin
keywords: CpG; antigen delivery; cancer immunotherapy; cancer vaccine; cleavable conjugates; redox; toll-like receptor ligand