mTRP-2 (180-188)

The tremendous development of peptide-based cancer vaccine has attracted incremental interest as a powerful approach in cancer management, prevention and treatment. As successful as tumor vaccine has been, major challenges associated with achieving efficient immune response against cancer are (1) drainage to and retention in lymph nodes; (2) uptake by dendritic cells (DCs); (3) activation of DCs. In order to overcome these barriers, here we construct PBE-modified TRP2 nanovaccine, which comprises TRP2 peptide tumor antigen and diblock copolymer PEG-b-PAsp grafted with phenylboronic ester (PBE). We confirmed that this TRP2 nanovaccine can be effectively trapped into lymph node, uptake by dendritic cells and induce DC maturation, relying on increased negative charge, ROS response and pH response. Consistently, this vehicle loaded with TRP2 peptide could boost the strongest T cell immune response against melanoma in vivo and potentiate antitumor efficacy both in tumor prevention and tumor treatment without any exogenous adjuvant. Furthermore, the TRP2 nanovaccine can suppress the tumor growth and prolong animal survival time, which may result from its synergistic effect of inhibiting tumor immunosuppression and increasing cytotoxic lymphocyte (CTL) response. Hence this type of PBE-modified nanovaccine would be widely used as a simple, safe and robust platform to deliver other antigen in cancer immunotherapy.

Tyrosinase-related protein-2 (TRP-2) is a non-mutated melanocyte differentiation antigen. The TRP-2-recognizing CD8(+) T cells can evoke immune responses to melanoma in both humans and mice. Developing epitopes with amino acid replacements in their sequences might improve the low immunogenicity against this 'self' tumor antigen. We designed altered peptide ligands (APLs) of TRP-2((180-188)) (SVYDFFVWL) with preferred primary and auxiliary HLA-A*0201 molecule anchor residue replacement. These APLs were screened for MHC-affinity by affinity prediction plots and molecular dynamics simulation, and analyzed in vitro for stability and binding-affinity to molecular HLA-A*0201. We also investigated the CTLs activities induced by TRP-2 wild-type epitope and the APLs both in vitro in human PBMCs and HLA-A2.1/K(b) transgenic mice. The results indicate that TRP-2 2M analog simultaneously had stronger binding-affinity and a lower dissociation rate to HLA-A*0201, than wild-type peptide. In addition, the analog 2M was superior to other APLs and wild-type epitope in terms of immunological efficacy ex vivo as measured by the ELISPOT assays of IFN-gamma and granzyme B. These results demonstrate that TRP-2 2M is an agonist epitope that can induce anti-tumor immunity superior to its wild-type epitope, and has potential application in peptide-mediated immunotherapy.

Cancer vaccines represent a prophylactic or therapeutic method of suppressing cancer by activating the adaptive immune system. The immune response is initiated by the delivery of tumor antigens to antigen presenting cells (APCs). The use of peptides as vaccine antigens is advantageous, especially in the availability and productivity of pure and defined antigens. However, their limited immunogenicity remains a major drawback, and therefore, the utilization of nanocarriers as a means of delivering antigens to target cells and/or the addition of immune stimulants have been investigated as an efficient peptide-based cancer vaccine. We have developed a solid-in-oil (S/O) nanodispersion as a transcutaneous nanocarrier for hydrophilic molecules. This system has attractive features as a peptide nanocarrier for cancer vaccines, including transcutaneous targeting of professional APCs in the skin, high encapsulation efficacy of hydrophilic molecules, and capacity for coloading with a variety of immune stimulants such as adjuvants. We therefore sought to utilize the developed S/O nanodispersion for the delivery of the tyrosine-related protein 2 peptide, TRP-2180-188, as a peptide antigen against melanoma. Transcutaneous vaccination of the S/O nanodispersion coloaded with adjuvant R-848 was associated with a significant inhibition of melanoma growth and suppression of lung metastasis in tumor-bearing mice. Our findings indicate the potential of S/O nanodispersions as an endogenous peptide carrier for cancer vaccines.