title: Improved immunogenicity of a self tumor antigen by covalent linkage to CD40 ligand.
abstract: The interaction between the CD40 ligand (CD40L) and CD40 on antigen-presenting cells (APCs) is critical in promoting humoral and cellular immune responses. Agonistic anti-CD40 monoclonal antibody and soluble CD40L can act as powerful adjuvants to promote vaccination, but usually require repeated high-dose treatment. In this study, we demonstrate that the adjuvant effect of CD40L can be greatly improved by directly linking the antigen to CD40L. We constructed a fusion protein (Id-CD40L) consisting of the extracellular domain of CD40L and the idiotype (Id) protein, a weakly immunogenic tumor-specific antigen derived from the murine 38C13 B-cell lymphoma. The soluble Id-CD40L fusion protein retained CD40 binding activity and stimulated CD80 and CD86 upregulation and interleukin (IL)-12 production by macrophages. Immunization of mice with Id-CD40L without adjuvants resulted in high titers of anti-Id Abs dominated by the IgG1 isotype and protected the mice from subsequent lethal tumor challenge. In a dose-response study, we demonstrated that Id-CD40L elicited anti-Id antibody (Ab) responses in all immunized animals, even at a dose as low as 0.5 microg. Immunization with free Id and an IgG-CD40L fusion protein, which was identical in structure to Id-CD40L but lost the Id determinant, resulted in significant lower anti-Id responses, indicating that physical linkage between the tumor antigen and CD40L was required for the optimal immune response. These results demonstrate that fusing CD40L to a candidate antigen can greatly improve the adjuvant activity of CD40L. This approach may be useful in developing vaccines for a variety of malignant and infectious diseases.
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: Hsing-I
authors.initials: HI
authors.lastname: Huang
authors.forename: Ping-Yi
authors.initials: PY
authors.lastname: Wu
authors.forename: Chin-Yee
authors.initials: CY
authors.lastname: Teo
authors.forename: Min-Nan
authors.initials: MN
authors.lastname: Chen
authors.forename: Yi-Chau
authors.initials: YC
authors.lastname: Chen
authors.forename: Dmytro
authors.initials: D
authors.lastname: Silin
authors.forename: Mi-Hua
authors.initials: MH
authors.lastname: Tao
mesh_terms: D000276:Adjuvants, Immunologic; D000818:Animals; D000951:Antigens, Neoplasm / Q000276:immunology; D001324:Autoantigens / Q000276:immunology*; D019013:CD40 Antigens / Q000276:immunology*; D023201:CD40 Ligand / Q000276:immunology*; D019496:Cancer Vaccines; D007111:Immunity, Cellular; D007130:Immunoglobulin Idiotypes; D016393:Lymphoma, B-Cell / Q000276:immunology* / Q000517:prevention & control; D051379:Mice; D008807:Mice, Inbred BALB C; D014407:Tumor Cells, Cultured
chemical_list: D000276:Adjuvants, Immunologic; D000951:Antigens, Neoplasm; D001324:Autoantigens; D019013:CD40 Antigens; D019496:Cancer Vaccines; D007130:Immunoglobulin Idiotypes; D023201:CD40 Ligand