Lipid-based cancer vaccines

Each aim of this project ranges from vaccine formulation to whole-body response; starting from the structure-function relationship of the cationic lipid DOTAP (1,2-dioleoyl-3-trimethylammonium-propane) to the immunological action in vivo. The three aims of this work examine DOTAP; the structural specificity, development of a melanoma-specific formulation and development of a joint siRNA/peptide delivery vehicle. The first aim in these studies investigates the impact of DOTAP's chiral center on a peptide based therapeutic vaccine in a murine cervical cancer model. The lipid, (R) or (S)-DOTAP was combined with an MHC Class I restricted peptide (E7), from the E7 oncogene in human cervical cancer. In this work, (R)-DOTAP/E7 was shown to act equally well as the racemic mixture in causing tumor regression, while (S)-DOTAP/E7 had a lesser effect. This data was supported by other studies evaluating the cell-mediated anti-tumor response, and in each, (R)-DOTAP/E7 showed greater efficacy. The second aim investigates the development of a peptide/lipid melanoma vaccine with a different antigenic peptide that poses unique formulation challenges. The amphipathic Trp2 peptide antigen was formulated to address poor aqueous solubility, and yielded stable vaccine particles when mixed with (R)-DOTAP. (R)-DOTAP/Trp2 delivered in high Trp2 doses to tumor-bearing mice showed enhanced tumor growth delay compared to lower Trp2 doses, which was supported by additional immunological assays. The third aim seeks to enhance the versatility of the delivery vector with added siRNA therapy. Formulation of tri-modal particle, including (R)-DOTAP adjuvant, melanoma antigen (Trp2 peptide) and siRNA against PD-L1 (RTP particles) expanded the versatility of the previously developed (R)-DOTAP/Trp2 vaccine. PD-L1 siRNA was incorporated to dampen the inhibitory signal that DCs express when activated, that can inhibit T cell function. The examination of the structure and activity of these particles in vitro and in vivo, led to further understandings of the vaccine. In a solid melanoma model, delivery of RTP showed a tumor growth delay statistically significant compared to particles with control siRNA. In closing, (R)-DOTAP is the immunologically active enantiomer, showing efficacy in cervical cancer and melanoma models, with the potential to deliver a variety of peptide antigens and siRNA, showing tumor growth delay