Abstract 2815: Induction of both OVA specific CD4+ and CD8+ T cells by using PepTivator® OVA-pulsed DCs in mouse model

Antigen specific immune response by both MHC class I-restricted CD8+ T cells and MHC class II-restricted CD4+ T cells is a key event in cancer immunotherapy. In DC vaccine therapy, the short epitope peptides (9 or 10-mer) are mainly used to load, but these short peptides are presented on MHC class I molecule and can stimulate only CD8+ T cells. Using whole protein as antigen might be better to induce both antigen specific CD8+ and CD4+ T cells. The PepTivator® is a peptide pool: consisting mainly of 15-mer sequences with 11 amino acids overlap and covering the complete sequence of target protein. In this study, we used PepTivator® derived from ovalbumin protein (PepTivator® OVA) instead of whole protein as antigen, and evaluated the inducing activity of antigen specific CD8+ and CD4+ T cell responses in mouse model. In order to examine the antigen presenting ability of PepTivator® OVA-pulsed DCs, CD8+ T cells (106 cells/mL) isolated from OT-I transgenic mouse (OT-I CD8T) or CD4+ T cells (106 cells/mL) isolated from OT-II transgenic mouse (OT-II CD4T) were cultured with PepTivator® OVA-pulsed DCs (5×104 cells/mL) for 4 days. As positive control, OT-I epitope peptide (OVA257-264aa) and OT-II epitope peptide (OVA323-339aa) were used. DCs were prepared from bone marrow cells of C57BL/6 mice after cultivation with medium containing GM-CSF, IL-4 and LPS for 10 days. In preparation of peptide-pulsed DCs, DCs were treated with each peptide at 2 µg/mL for 4 hours and washed with medium to deplete free peptide before use. During the cultivation of OT-I CD8T or OT-II CD4T cells with each peptide-pulsed DCs, the responsive T cell proliferation was measured daily by flow cytometric analysis with absolute count beads and CFSE dye dilution. In addition, cytokines (IL-2 and IFN-gamma) in culture supernatant were measured by ELISA. As a result, the proliferation of OT-I CD8T cells cocultured with PepTivator® OVA-pulsed DCs seemed to be similar to that in coculture with OT-I epitope peptide-pulsed DCs. In the case of proliferation assay using OT-II CD4T cells, PepTivator® OVA-pulsed DCs showed similar T cell expansion in comparison with OT-II epitope peptide-pulsed DCs. As for cytokines secretion, no difference was observed in concentration of IL-2 and IFN-gamma in both cases using OT-I CD8T and OT-II CD4T cells when PepTivator® OVA was compared with OT-I or OT-II epitope peptide, respectively. These results showed that PepTivator® OVA pulsed-DCs could induce both antigen specific CD8+ and CD4+ T cell responses in mouse model. It suggests that PepTivator® OVA is at least superior to short epitope peptide in inducing antigen specific T cell response. In addition, it might be big advantage that PepTivator® derived from tumor antigen could be useful in many candidate patients without their HLA restriction. It is expected that therapeutic benefit of PepTivator® pulsed-DCs will be shown in clinical. Citation Format: Kenji Miki, Koji Nagaoka, Hermann Bohnenkamp, Takayuki Yoshimoto, Takashi Kamigaki, Ryuji Maekawa. Induction of both OVA specific CD4+ and CD8+ T cells by using PepTivator® OVA-pulsed DCs in mouse model. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2815. doi:10.1158/1538-7445.AM2014-2815