Stimulation of Tumor-Specific Immunity by p5 HER-2/neu Generated Peptide Encapsulated in Nano-liposomes with High Phase Transition Temperature Phospholipids

Abstract The aim of this study is to evaluate the possible advantages of liposomes with high transition temperature (Tm) in the function of a vaccine for P5 HER2/neu-generated peptide and its adjuvant action to elicit CD8+ T cell response and its efficacy in TUBO in vivo tumor mice model, which over expresses the HER2/neu oncogene. P5, a hydrophobic peptide, was encapsulated in the nanoliposomes consisting of DSPC/DSPG/Chol(Tm 54°C) with a chaotropic loading system via 7M urea and described by size, zeta potential, encapsulation efficiency, and the structural stability of SDS-PAGE. We immunized the mice for three times subcutaneously based on a two-week intervals using encapsulated peptide in the nanoliposomes, empty liposome, P5 in PBS, and PBS. Enzyme-linked immunospot assay, cytotoxicity test, and flow cytometric studies followed by the size of tumor and survival time measurements, which were done in TUBO tumor mice version. Findings of ELISpot and flow cytometric analysis showed that immunization with Lip-p5 nanoliposomes has enhanced the antigen-specific IFN-γ response of CD8+ T cells and induced CTL response, which resulted in a smaller tumor and longer survival time. In addition to increase in amounts of IFN-γ-CD8+ T cells in a group, which was immunized with Lip-P5, our findings also revealed a Th1 shift in the group immunized with an empty liposome with reduced frequencies of IL-4-producing cells and increase of IFN-γ-producing cells. The results indicated that simple liposomes consisting of phospholipids with high transition temperature could be an effective vaccine vehicle for tumor-associated antigens for inducing cell mediate immunity.