VEGF165b mutant can be used as a protein carrier to form a chimeric tumor vaccine with Mucin1 peptide to elicit an anti-tumor response

Peptide-based anticancer vaccines have shown some efficacy in generating cancer-specific immune responses in various cancer studies, but clinical success is limited, one of the reasons is due to its prone degradation and weak immunogenicity. So some tumor epitope peptide vaccines often require coupling or forming fusion proteins with corresponding protein carriers to enhance their stability and immunogenicity. Given the scarcity of validated carriers for clinical trials, there is an urgent requirement for the development of novel protein carrier. Our previous work has demonstrated that VEGF165b mutant could be used as an effective immunization adjunct to enhance anti-tumor immune response. By analyzing and evaluating the gene structure of VEGF, we speculated that mVEGF165b has the potential to be utilized as a tumor peptide vaccine carrier. An mVEGF165b-MUC1 chimeric tumor vaccine was produced by fusing the MUC1 peptide （(MUC1, a T-cell epitope dominant peptide from Mucin1） to the C-terminus of mVEGF165b, expressing the fusing protein in pichia yeast, followed by purification with a HiTrap heparin affinity chromatography column. We found that immunizing mice with mVEGF165b-MUC1 fusion protein induced high-titer antibodies against VEGF in a preventive context, which in turn reduced the proportion of Tregs and further stimulated mice to produce T-cell responses specific to mucin1. The high-titer VEGF antibody stimulated by mVEGF165b also promoted tumor blood vessel maturation and facilitated T-cell infiltration. In conclusion，immunized with mVEGF165b-MUC1 protein are beneficial for eliciting immune responses targeting Mucin1, mVEGF165b have the potential to be utilized as a peptide tumor vaccine carrier. •mVEGF165b can be used as a protein carrier for the MUC1 peptide.•High anti-VEGF antibody titers induced by mVEGF165b-MUC1 decreased immunosuppression by reducing the proportion of Tregs.•The decreased immunosuppression augmented the immune response induced by the peptide vaccine from Mucin-1.