Abstract A020: A novel synthetic CD40L plasmid adjuvant generates unique anti-HPV DNA vaccine induced responses that impact tumor growth

Abstract

The use of plasmid adjuvants encoding cytokine, chemokine or immune modulators to tailor vaccine-induced response is a strength of the DNA vaccine platform. Due to its role in both innate and adaptive immunity, we hypothesis that the co-delivery of plasmid encoded CD40 ligand (CD40L) could increase DNA vaccine responses. In its natural form, CD40L can occur as either a surface bound form or a cleaved/solubilized form. Thus, we sought to determine if different forms of pCD40L can influence cellular and humoral responses when co-delivered with a HPV16 DNA vaccine expressing the oncogenic proteins E6 and E7. Mice were immunized with HPV DNA with or without synthetic optimized plasmids expressing various forms of CD40L followed by electroporation (EP). Mice that received the soluble form of CD40L (sCD40L) exhibited significantly higher antigen specific CD8+ T cell responses including IFN-γ, IL-2 and TNF-α expression as well as slight increases in CD4+T cells and antibody responses. These responses were also maintained into memory. Conversely, the surface bound as well as the wild-type form of CD40L blunted vaccine-induced responses compared to vaccine alone. Time course analysis revealed that 11 days after primary immunization, CD8+ tetramer specific (H-2Db HPV16 E7 (RAHYNIVTF)) T cells in mice immunized with sCD40L averaged around 18% compared to vaccine alone at 4%. These responses were partially dependent on CD4+ T cell help and were functionally similar to responses observed post final immunization. We have also observed similar vaccine-induced immune responses when sCD40L was combined with other cancer vaccines including mouse telomerase reverse transcriptase (mTERT). Upon therapeutic tumor challenge, mice immunized with HPV + sCD40L displayed significant tumor regression compared to vaccine alone or naïve animals. Additionally, when sCD40L was included the ratio of tetramer specific CD8+ T cells to CD4+ Tregs infiltrating the tumor was significantly higher compared to vaccine alone or naïve group. These results demonstrate the power of using a plasmid adjuvant encoding a synthetic optimized sCD40L in a DNA vaccine. Additional studies in other animal cancer models are important for determining the possible broad importance of this approach for cancer immune therapy. Citation Format: Megan C. Wise, Elizabeth K. Duperret, Daniel O. Villarreal, Lumena Louis, Jian Yan, Matthew P. Morrow, Laurent M. Humeau, Niranjan Y. Sardesai, David B. Weiner. A novel synthetic CD40L plasmid adjuvant generates unique anti-HPV DNA vaccine induced responses that impact tumor growth [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A020.