Anti-tumor immunity elicited by cross-linking vaccine heat shock protein 72 and alpha-fetoprotein epitope peptide.

Abstract

Hepatocellular carcinoma (HCC) is one of the most common malignancies over the world. Alpha-fetoprotein (AFP) is an oncofetal protein during HCC development, which could generate weaker and less reproducible antitumor protection, and may serve as atarget for immunotherapy. Therefore, it is imperative to enhance its immunogenicity and develop therapeutic vaccines to eliminate AFP-expressing tumors. In this study, by using glutaraldehyde cross-linking, we constructed apotential therapeutic peptide vaccine, heat shock protein 72 (HSP72) and AFP epitope peptide (HSP72/AFP-P). ELISPOT was applied to evaluate the quantity of AFP-specific CD8+ Tcell that secreted IFN-γ in immunized BALB/C mice. Granzyme Breleased from natural killer cells and AFP-specific antibody responses in immunized mice were detected by ELISA. The anti-tumor effects were investigated by in vitro cytotoxic T-lymphocyte assays and in vivo tumor therapeutic experiments. The results showed that reconstructed HSP72 and AFP epitope peptide vaccine synergistically exhibited significant increases in AFP-specific CD8+ Tcells, natural killer cells responses and impressive antitumor effects against AFP-expressing tumors. Immunization of BALB/C mice with HSP72/AFP-P vaccine elicited stronger T-cells responses. The numbers of IFN-γ-producing CD8+ Tcells from mice immunized with HSP72/AFP-P were 30 times more than those from mice immunized with AFP-P, HSP72 or PBS (P < 0.01). The concentration of granzyme Bin natural killer cells from mice immunized with HSP72/AFP-P were 15 times higher than that from other groups (P < 0.01). In vitro effector cells from mice immunized with HSP72/AFP-P showed much stronger cytolytic effect on H22 target cells than those from mice vaccinated with AFP-P, HSP72 or PBS (P< 0.01). Priming mice with the reconstructed vaccine exhibited robust strong protective immunity. Mice immunized with HSP72 or AFP-P alone demonstrated higher average tumor volumes than mice immunized with HSP72/AFP-P (P < 0.05). Our study suggests that constructing atumor vaccine by cross-linking AFP antigen epitope peptide and HSP72 is apromising approach for cancer therapy.