Targeting of peptide coupled dendrimers to human dendritic cells leads to autologous T cell activation (53.15)

Abstract

Abstract Targeted delivery of vaccines to dendritic cells (DC) has been shown to be an effective approach to induce antigen-specific T cell immunity in vitro and in vivo. Peptides are used for ex vivo pulsing of DC, but not suitable to target dendritic cells in vivo. To overcome this limitation we have covalently attached 15 mers peptides covering the whole CMV pp65 amino acid sequence onto polyamidoamine (PAMAM) dendrimers and coupled them to an anti biotin antibody. Using this construct we were able to specifically target large amounts of peptides via CD36 biotin antibody to blood DC for effective stimulation of autologous CMV specific T cells analyzed by intracellular interferon gamma production. Appropriate activation of targeted DC with Toll like receptor ligands proved to be essential for effective T cell stimulation. Peptide pulsed DC were not sensitive to the antigen processing inhibitor chloroquine, whereas PAMAM-peptide targeted DC were and failed to stimulate T cells. Moreover T cell stimulation with PAMAM-peptide showed a substantial CD4 T cell response, but only weak CD8 response. Taken together this demonstrates that targeted PAMAM-peptides are internalized and processed before presentation via MHC class II molecules. In vivo targeting of PAMAM-peptides may represent a promising perspective for effective induction of DC derived immune responses against defined antigen epitopes.