title: CTL induction by cross-priming is restricted to immunodominant epitopes.
abstract: CTL are induced by two pathways, i.e. direct priming, where tumor cells present tumor antigens to naïve specific CTL, and cross-priming, where professional APC cross-present captured tumor antigens to CTL. Here, we examined direct priming versus cross-priming after immunizing (H-2(b) x H-2(d)) F1 mice with either H-2(b) or H-2(d) positive tumor cells transfected with the GP or nucleoprotein (NP) of lymphocytic choriomeningitis virus (LCMV). Cross-priming was observed for the immunodominant epitopes LCMV-gp33 and -np118, although direct induction resulted in higher CTL frequencies. In contrast, CTL specific for the subdominant epitopes LCMV-gp283 or -np396 were induced only if epitopes were presented directly on MHC class I molecules of the immunizing cell. The broader repertoire and the higher CTL frequencies induced after vaccination with haplotype-matched tumor cells resulted in more efficient anti-tumor and antiviral protection. Firstly, our results indicate that certain virus and tumor antigens may not be detected by CD8(+) T cells because of impaired cross-priming. Secondly, efficient cross-priming contributes to the immunodominant nature of a tumor-specific CTL epitope. Thirdly, vaccine strategies using autologous or syngenic antigen-expressing cells induce a broader repertoire of tumor-specific CTL and higher CTL frequencies.
authors.affiliation: Department of Clinical Research, University of Berne, Berne, Switzerland.
authors.forename: Viktor
authors.initials: V
authors.lastname: Pavelic
authors.forename: Matthias S
authors.initials: MS
authors.lastname: Matter
authors.forename: Sabine
authors.initials: S
authors.lastname: Mumprecht
authors.forename: Isabel
authors.initials: I
authors.lastname: Breyer
authors.forename: Adrian F
authors.initials: AF
authors.lastname: Ochsenbein
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000276:immunology* / Q000378:metabolism; D045744:Cell Line, Tumor; D045142:Cross-Priming / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000276:immunology* / Q000378:metabolism; D016056:Immunodominant Epitopes / Q000276:immunology* / Q000378:metabolism; D008217:Lymphocytic choriomeningitis virus / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism; D014162:Transfection
chemical_list: D000956:Antigens, Viral; D015395:Histocompatibility Antigens Class I; D016056:Immunodominant Epitopes