Abstract 5642: Electroporation as a feasible method for antigen delivering into vectors loaded with NKT cell ligand
Authors: Arimoto Akira , Nishi Masayasu , Yamashita Kimihiro , Sugita Yutaka , Fukuoka Eiji , Tanaka Tomoko , Kamigaki Takashi , Takimoto Rishu , Kakeji Yoshihiro 
Published: August 2018

Background: Invariant natural killer T (iNKT) cells have been shown as an ideal immunetherapeutic target of which the activation via α-Galactosylceramide (α-GalCer) conjugated with the MHC class I-like CD1d molecule induces both the innate and adaptive immune system. With transfection of antigen-coding mRNA, α-GalCer loaded CD1d-expressing cells can act as a vector to enhance the antigen-specific immune responses. However, the method using the transfection of antigen-coding mRNA is sometimes too complicated. Electroporation (EP) has been reported as a way to induce substances easily into cells. We applied EP as a simple method to deliver the antigen into the vector for iNKT activation. In this study, we aimed to show the feasibility of EP as a method to deliver the antigen into α-GalCer loaded DCs, a naturally CD1d-expressing vector, in terms of inducing antigen-specific antitumor responses.

Methods: DCs were generated from bone marrow of C57BL/6 mice. Ovalbumin (OVA) was electroporated to DCs as a tumor model antigen. To load α-GalCer, DCs were cultured with α-GalCer for 48 hours. We compared the antitumor responses of α-GalCer loaded DCs with or without electroporated OVA in C57BL/6 mice. Mice were prophylactically administered each type of DCs intravenously followed by subcutaneous injection of EG7, which is OVA induced EL4, thymoma (n = 5, respectively). We evaluated the tumor size and the survival rate.

Results: With electroporated OVA, tumors did not grow in mice administered α-GalCer loaded DCs whereas tumors in mice administered α-GalCer loaded DCs without electroporated OVA aggressively progressed (tumor size on day 28 after tumor inoculation; 3 ± 3 vs 4176 ± 1571 mm3, P &lt; 0.05). In mice administered α-GalCer loaded DCs with electroporated OVA, no death was observed during the whole observation period. Survival rate was significantly better for mice administered α-GalCer loaded DCs with electroporated OVA than those administered α-GalCer loaded DCs without electroporated OVA (P &lt; 0.05).

Conclusion: α-GalCer loaded DCs with electroporated OVA showed significantly higher rate of tumor rejection and longer survival in the mice model inoculated OVA-induced tumor compared to α-GalCer loaded DCs without electroporated OVA. EP was feasible as a way to deliver the antigen into the vector, which induced antigen-specific antitumor responses. We are trying to show the activity of antigen-specific cytotoxic T lymphocytes following the administration of α-GalCer loaded DCs with electroporated antigen.

Citation Format: Akira Arimoto, Masayasu Nishi, Kimihiro Yamashita, Yutaka Sugita, Eiji Fukuoka, Tomoko Tanaka, Takashi Kamigaki, Rishu Takimoto, Yoshihiro Kakeji. Electroporation as a feasible method for antigen delivering into vectors loaded with NKT cell ligand [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5642.