Abstract 1474: Repurposing the yellow fever vaccine for intratumoral immunotherapy
Authors: Aznar M. Angela , Molina Carmen , Teijeira Alvaro , Azpilikueta Arantza , Garasa Saray , Sanchez-Paulete Alfonso R. , Etxeberria Iñaki , Alvarez Maite , Berraondo Pedro , Melero Ignacio 
Published: August 2019

Abstract
Introduction: Yellow Fever attenuated virus vaccine (17D) induces very potent cellular and humoral immunity. Its delivery in situ in the tumor bed may induce an immune response leading to the killing of infected cells.
Experimental procedures: 17D virus was propagated in Vero cells and infectious supernatants were harvested. To evaluate in vitro sensitivity of tumors to 17D infection, a panel of human and mouse tumor cell lines were infected with increasing MOIs and viability was quantified.
To evaluate the antitumor efficacy of intratumor (i.t.) injection of 17D, 4x106pfu/50μl were injected (4 doses) in MC38- and in B16-OVA-tumor bearing C57BL/6 mice. Systemic antitumor effects of i.t 17D were examined in bilateral MC38 models in which one of the tumors was left uninjected. Depletion experiments were performed to assess the contribution of CD4, CD8, Gr1 and NK cells. To determine the role of conventional type-I dendritic cells (cDC1), identical experiments were performed in BATF3-/- mice. Tumor and lymph node immune infiltrates were examined by multiparametric flow cytometry. Combination with intraperitoneal anti-PD1 or anti-CD137 was performed to improve antitumor efficacy.
To evaluate the effects of 17D-preexisting immunity, mice were preimmunized with 17D prior to MC38 bilateral inoculation and were subsequently treated. To assess the individual cell type contribution to the antitumor effects induced upon 17D pre-immunization, CD8, CD4, CD8+CD4 or sera from preimmunized mice were passively transferred 24h prior to first 17D i.t injection to MC38-tumor bearing mice.
Results: 17D live attenuated strain is able to induce cell death of mouse and human tumor cell lines. In MC38 or B16-OVA mice models, repeated i.t. injections of 17D clearly delayed tumor progression. Regarding the systemic effect of i.t. 17D, certain contralateral therapeutic efficacy was induced upon i.t injection in bilateral MC38 models. These local and distant effects were dependent on CD8+ and cDC1 cells. 17D i.t injection increased in CD8+ T cell infiltrates and decreased in Tregs in injected tumors, while in contralateral tumors induced an increase of CD8+ and NK cells expressing key immunomodulatory receptors. I.t. 17D with anti-CD137 monoclonal antibody (mAb) induced a strong synergistic effect, while combination with anti-PD-1 mAb showed mild local additive efficacy compared to 17D monotherapy. Both combinatorial treatments delayed contralateral tumor growth. Notably, 17D preimmunization induced an important improvement of local and distant antitumor immunity. Such beneficial effects of preimmunization were transferred along with CD8+ T cells.
Conclusions: 17D can be safely injected i.t. in preclinical models, giving rise to immune-mediate antitumor effects that can be combined with other immunotherapy agents. The repurposed use of this GMP-grade vaccine in preimmunized patients represents a promising and feasible immunotherapy approach.
Citation Format: M. Angela Aznar, Carmen Molina, Alvaro Teijeira, Arantza Azpilikueta, Saray Garasa, Alfonso R. Sanchez-Paulete, Iñaki Etxeberria, Maite Alvarez, Pedro Berraondo, Ignacio Melero. Repurposing the yellow fever vaccine for intratumoral immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1474.