Enhanced activation of T cells by dendritic cells engineered to hyperexpress a triad of costimulatory molecules.
BACKGROUND
Activation and proliferation of T cells are essential for a successful cellular immune response to an antigen. Antigen-presenting cells (APCs) activate T cells through a two-signal mechanism. The first signal is antigen specific and causes T cells to enter the cell cycle. The second signal involves a costimulatory molecule that interacts with a ligand on the T-cell surface and leads to T-cell cytokine production and their proliferation. Dendritic cells express several costimulatory molecules and are believed to be the most potent APCs. Two recombinant poxvirus vectors (replication-defective avipox [fowlpox; rF] and a replication-competent vaccinia [rV]) have been engineered to express a triad of costimulatory molecules (B7-1, intercellular adhesion molecule-1, and leukocyte function-associated antigen-3; designated TRICOM). This study was designed to determine if dendritic cells infected with these vectors would have an enhanced capacity to stimulate T-cell responses.


METHODS
Murine dendritic cells (of both intermediate maturity and full maturity) were infected with rF-TRICOM or rV-TRICOM and were used in vitro to stimulate naive T cells with the use of a pharmacologic agent as signal 1, to stimulate T cells in allospecific mixed lymphocyte cultures, and to stimulate CD8(+) T cells specific for a peptide from the ovalbumin (OVA) protein. In addition, dendritic cells infected with TRICOM vectors were pulsed with OVA peptide and used to vaccinate mice to examine T-cell responses in vivo. All statistical tests were two-sided.


RESULTS
Dendritic cells infected with either rF-TRICOM or rV-TRICOM were found to greatly enhance naive T-cell activation (P<.001), allogeneic responses of T cells (P<.001), and peptide-specific T-cell stimulation in vitro (P<.001). Peptide-pulsed dendritic cells infected with rF-TRICOM or rV-TRICOM induced cytotoxic T-lymphocyte activity in vivo to a markedly greater extent than peptide-pulsed dendritic cells (P =.001 in both).


CONCLUSIONS
The ability of dendritic cells to activate both naive and effector T cells in vitro and in vivo can be enhanced with the use of poxvirus vectors that potentiate the hyperexpression of a triad of costimulatory molecules. Use of either rF-TRICOM or rV-TRICOM vectors significantly improved the efficacy of dendritic cells in priming specific immune responses. These studies have implications in vaccine strategies for both cancer and infectious diseases.
Hodge
J W
JW
Laboratory of Tumor Immunology and Biology, Division of Basic Sciences, National Cancer Institute, Bethesda, MD, USA.
Rad
A N
AN
Grosenbach
D W
DW
Sabzevari
H
H
Yafal
A G
AG
Gritz
L
L
Schlom
J
J
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000276:immunology; D018122:B7-1 Antigen / Q000276:immunology*; D019013:CD40 Antigens / Q000276:immunology; D018968:CD58 Antigens / Q000276:immunology*; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D002460:Cell Line; D016207:Cytokines / Q000276:immunology; D003713:Dendritic Cells / Q000276:immunology* / Q000821:virology; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D005822:Genetic Vectors; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D011212:Poxviridae; D013601:T-Lymphocytes / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation
D000911:Antibodies, Monoclonal; D018122:B7-1 Antigen; D019013:CD40 Antigens; D018968:CD58 Antigens; D002272:Carcinoembryonic Antigen; D016207:Cytokines; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1