title: Recombinant cholera toxin B subunit activates dendritic cells and enhances antitumor immunity.
abstract: Activation of dendritic cells (DC) is crucial for priming of cytotoxic T lymphocytes (CTL), which have a critical role in tumor immunity, and it is considered that adjuvants are necessary for activation of DC and for enhancement of cellular immunity. In this study, we examined an adjuvant capacity of recombinant cholera toxin B subunit (rCTB), which is non-toxic subunit of cholera toxin, on maturation of murine splenic DC. After the in vitro incubation of DC with rCTB, the expression of MHC class II and B7-2 on DC was upregulated and the secretion of IL-12 from DC was enhanced. In addition, larger DC with longer dendrites were observed. These data suggest that rCTB induced DC maturation. Subsequently, we examined the induction of tumor immunity by rCTB-treated DC by employing Meth A tumor cells in mice. Pretreatment with subcutaneous injection of rCTB-treated DC pulsed with Meth A tumor lysate inhibited the growth of the tumor cells depending on the number of DC. Moreover, intratumoral injection of rCTB-treated DC pulsed with tumor lysate had therapeutic effect against established Meth A tumor. Immunization with DC activated by rCTB and the tumor lysate increased number of CTL precursor recognizing Meth A tumor. The antitumor immune response was significantly inhibited in CD8+ T cell-depleted mice, although substantial antitumor effect was observed in CD4+ T cell-depleted mice. These results indicated that rCTB acts as an adjuvant to enhance antitumor immunity through DC maturation and that CD8+ T cells play a dominant role in the tumor immunity. Being considered to be safe, rCTB may be useful as an effective adjuvant to raise immunity for a tumor in clinical application.
authors.affiliation: Department of Geriatric and Environmental Dermatology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, Japan.
authors.forename: Iwao
authors.initials: I
authors.lastname: Isomura
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yasuda
authors.forename: Kunio
authors.initials: K
authors.lastname: Tsujimura
authors.forename: Toshitada
authors.initials: T
authors.lastname: Takahashi
authors.forename: Kunio
authors.initials: K
authors.lastname: Tochikubo
authors.forename: Akimichi
authors.initials: A
authors.lastname: Morita
mesh_terms: D000276:Adjuvants, Immunologic; D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D051940:B7-2 Antigen; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D045744:Cell Line, Tumor; D002772:Cholera Toxin / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology*; D005260:Female; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D007114:Immunization; D018664:Interleukin-12 / Q000032:analysis; D008212:Lymphocyte Depletion; D008562:Membrane Glycoproteins / Q000032:analysis; D051379:Mice; D008807:Mice, Inbred BALB C; D009374:Neoplasms, Experimental / Q000139:chemically induced / Q000276:immunology* / Q000517:prevention & control; D011994:Recombinant Proteins / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; D015703:Antigens, CD; D051940:B7-2 Antigen; C497965:Cd86 protein, mouse; D000949:Histocompatibility Antigens Class II; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D018664:Interleukin-12; D002772:Cholera Toxin