Multiple Antigenic Peptides Based on H-2Kb–Restricted CTL Epitopes from Murine Heparanase Induce a Potent Antitumor Immune Response In Vivo

Accumulating research suggests that heparanase may be a universal tumor-associated antigen (TAA). Several heparanase T cell epitopes from humans and mice have already been identified. However, because of low immunogenicity, polypeptide vaccines usually have difficulty inducing effective anti-tumor immune responses in vivo. In this study, to increase the immunogenicity of polypeptide vaccines, we designed and synthesized two four-branch multiple antigenic peptides (MAP) based on mouse heparanase (mHpa) T cell epitopes (mHpa398, mHpa519). The dendritc cells from mice bone marrow loaded with above MAP vaccines from heparanase were used to evaluate immune response against various tumor cell lines, compared with immune response to their corresponding linear peptides, ex vivo and in vivo. We further assessed IFN-γ release both in CD4+ T cells depleted and non-depleted mice. The results demonstrated that effectors generated from DCs loaded with MAP-vaccinated mice splenocytes induced a stronger immune response against target cells expressing both heparanase and H-2Kb than did effectors generated from mice vaccinated with their corresponding linear peptides. Heparanase-specific CD8+ T cell responses induced by MAP and linear peptide vaccination required synergy of CD4+ T cells. Additionally, heparanse-derived MAP vaccines significantly inhibited the growth of B16 murine melanoma in C57BL/6 mice, while also increasing the survival rate of tumor-bearing mice. Our data suggest that MAP vaccines based on T cell epitopes from heparanase are efficient immunogens for tumor immunotherapy.