title: Antigen targeting to endosomal pathway in dendritic cell vaccination activates regulatory T cells and attenuates tumor immunity.
abstract: Lymphoma cells are malignant cells of the T- or B-cell lineage that often express many surface markers inappropriately, yet are not recognized as abnormal by the immune system. We modeled this situation by inoculating ovalbumin-expressing E.G7-OVA lymphoma cells into mice that expressed ovalbumin as a self antigen in pancreatic islets, and investigated the efficacy of dendritic cell (DC) vaccination in these mice. Although vaccination with DC-expressing ovalbumin induced strong cytotoxic T-cell immunity, which led to clearance of E.G7-OVA lymphoma cells in naive C57BL/6 mice, DC vaccination was ineffective in mice expressing ovalbumin as a self antigen. Antigen modification to increase its processing via the endosomal processing pathway dramatically increased CD4 T-cell activation but paradoxically, impaired the protective effect of DC vaccination even in naive mice. Depletion of CD25(+) T cells (regulatory T cells [Tregs]) prior to vaccination restored the efficacy of DC vaccination and allowed eradication of lymphoma also in mice expressing ovalbumin as a self antigen. We conclude that lymphoma cells may be eradicated using DC vaccination if activation of CD25(+) Tregs is simultaneously inhibited, and that intentionally enhanced endosomal antigen processing in DC vaccines may shift the balance from CD4 T-cell help toward stimulation of Tregs.
authors.affiliation: MediCity Research Laboratory, University of Turku, Tykistökatu 6A, 20520 Turku, Finland.
authors.forename: Mikael
authors.initials: M
authors.lastname: Maksimow
authors.forename: Mari
authors.initials: M
authors.lastname: Miiluniemi
authors.forename: Fumiko
authors.initials: F
authors.lastname: Marttila-Ichihara
authors.forename: Sirpa
authors.initials: S
authors.lastname: Jalkanen
authors.forename: Arno
authors.initials: A
authors.lastname: Hänninen
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology*; D019496:Cancer Vaccines / Q000276:immunology; D003713:Dendritic Cells / Q000276:immunology* / Q000637:transplantation; D011992:Endosomes / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D008223:Lymphoma / Q000276:immunology* / Q000628:therapy; D051379:Mice; D018345:Mice, Knockout; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D014611:Vaccination
chemical_list: D001324:Autoantigens; D019496:Cancer Vaccines