title: Combination of CTL-associated antigen-4 blockade and depletion of CD25 regulatory T cells enhance tumour immunity of dendritic cell-based vaccine in a mouse model of colon cancer.
abstract: Immune regulation has been shown to be involved in the progressive growth of some murine tumours. Interruption of immune regulatory pathways via CTL-associated antigen-4 (CTLA-4) blockade or removal of CD4(+) CD25(+) regulatory T (Treg) cells appears to be a promising strategy for cancer immunotherapy. In this study, we tested the hypothesis that the combination of CTLA-4 blockade and depletion of Treg cells would improve the potency of dendritic cell (DC)-based vaccine in a clinically relevant mouse model, which is transgenic for both carcinoembryonic antigen (CEA) and HLA-A2 for the treatment of colon carcinoma in a therapeutic setting. We found that administration of anti-CD25 antibody prior to vaccination or systemic administration of anti-CTLA-4 antibody with the vaccine improved tumour-free survival against CEA-expressing tumours compared with mice immunized with DC-based vaccine alone. However, the efficacy of the vaccine proved to be most effective when anti-CTLA-4 antibody was combined with Treg inhibition. This vaccination strategy dramatically improved the tumour-free survival and allowed the development of long-lasting immune responses. The combined vaccination strategy resulted in increased secretion of IFN-gamma and enhanced HLA-A2-restricted CEA-specific CTL responses. Furthermore, coadministration of anti-CD25 and anti-CTLA-4 antibodies along with the vaccine was effective against more advanced tumours. These results provide evidence that simultaneous blockade of T-cell regulatory pathways is a promising approach for the induction of therapeutic antitumour immunity against CEA(+) colon carcinoma.
authors.affiliation: Department of Internal Medicine, University of Cincinnati Medical Center, Cincinnati, OH, USA. asaha@umn.edu
authors.forename: Asim
authors.initials: A
authors.lastname: Saha
authors.forename: S K
authors.initials: SK
authors.lastname: Chatterjee
mesh_terms: D000818:Animals; D000974:Antibodies, Antinuclear / Q000097:blood / Q000276:immunology; D015703:Antigens, CD / Q000276:immunology; D060908:CTLA-4 Antigen; D019496:Cancer Vaccines / Q000276:immunology*; D002272:Carcinoembryonic Antigen / Q000276:immunology; D002469:Cell Separation; D003110:Colonic Neoplasms / Q000276:immunology* / Q000628:therapy; D003713:Dendritic Cells / Q000637:transplantation*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D015789:HLA-A2 Antigen / Q000276:immunology; D007167:Immunotherapy / Q000379:methods*; D053645:Interleukin-2 Receptor alpha Subunit / Q000037:antagonists & inhibitors / Q000276:immunology; D008212:Lymphocyte Depletion; D051379:Mice; D008822:Mice, Transgenic; D016176:T-Lymphocyte Subsets / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
chemical_list: D000974:Antibodies, Antinuclear; D015703:Antigens, CD; D060908:CTLA-4 Antigen; D019496:Cancer Vaccines; D002272:Carcinoembryonic Antigen; C556707:Ctla4 protein, mouse; D015789:HLA-A2 Antigen; D053645:Interleukin-2 Receptor alpha Subunit