1. ¹Laboratory of Molecular and Cellular Therapy, Department of Physiology-Immunology, Medical School of the Vrije Universiteit Brussel, Brussels, Belgium
2. ²Department of Hematology-Immunology, Medical School of the Vrije Universiteit Brussel, Brussels, Belgium
3. ³Department of Medical Oncology, Universitair Ziekenhuis Brussel, Brussels, Belgium

Correspondence: Aude Bonehill, Laboratory of Molecular and Cellular Therapy, Department of Physiology-Immunology, Medical School of the Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels 1090, Belgium. E-mail: aude.bonehill@vub.ac.be

Received 15 January 2008; Accepted 24 March 2008; Published online 22 April 2008.

Abstract

The effectiveness of the dendritic cell (DC) vaccination protocols that are currently in use could be improved by providing the DCs with a more potent maturation signal. We therefore investigated whether the T-cell stimulatory capacity of human monocyte–derived DCs could be increased by co-electroporation with different combinations of CD40L, CD70, and constitutively active toll-like receptor 4 (caTLR4) encoding mRNA. We show that immature DCs electroporated with CD40L and/or caTLR4 mRNA, but not those electroporated with CD70 mRNA, acquire a mature phenotype along with an enhanced secretion of several cytokines/chemokines. Moreover, these DCs are very potent in inducing naive CD4⁺ T cells to differentiate into interferon- (IFN-)-secreting type 1 T helper (Th1) cells. Further, we assessed the capacity of the electroporated DCs to activate naive HLA-A2-restricted MelanA-specific CD8⁺ T cells without the addition of any exogenous cytokines. When all three molecules were combined, a >500-fold increase in MelanA-specific CD8⁺ T cells was observed when compared with immature DCs, and a >200-fold increase when compared with cytokine cocktail–matured DCs. In correlation, we found a marked increase in cytolytic and IFN-/tumor necrosis factor- (TNF-) secreting CD8⁺ T cells. Our data indicate that immature DCs genetically modified to express stimulating molecules can induce tumor antigen-specific T cells in vitro and could prove to be a significant improvement over DCs matured with the methods currently in use.