Analysis of Antitumor Immunity Using Dendritic Cells Treated with Various Protein-transduction Domain (PTD)-containing Protein Antigen

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Protein transduction domains (PTDs) have been used increasingly to deliver reagents, such as proteins, oligonucleotides to a variety of cell types in vitro and in vivo. We have previously shown that HIV TAT-PTD-containing whole protein antigens (Ags)-transduced dendritic cells (DC) stimulated Ag-specific CD8+ and CD4+ T cells by processing and presenting Ag-epitopes onto MHC class I and class II. Although the CTL activity generated was sufficient to prevent engraftment of mice with Ag-expressing tumors, treatment of tumor-bearing mice with TAT-PTD Ag-transduced DC resulted in tumor regression in some, but not all animals. Recently, several other PTDs were reported their higher transduction efficiencies than TAT-PTD. To evaluate the PTD for induction of more efficient immune responses in tumor vaccination study, we engineered several recombinant fusion OVA proteins which contain PTDs including polyarginine (R9), known as the most efficacious PTD. Our results demonstrated that R9-PTD showed higher transduction efficiency to DC among PTDs studied, and that efficacy was closely correlated with the potency of Ag-specific CD4+, CD8+ T cell activations in vitro and in vivo. Twice vaccination with R9-PTD-OVA-transduced DC in (OVA-expressing) tumor-bearing mice induced higher antitumor immunity by strong boosting effects, and elicited complete rejection of tumor mass when co-injection with LPS or OK432. This approach should be clinically applicable, and offers theoretical and practical advantages to those that are in current use, such as peptide therapy.