Single Amino Acid Deletion at N-Terminus of the Target Antigen in DNA Vaccine Induces Altered CD8(+) T Cell Responses against Tumor Antigen

Since CD8(+) T cells have immunological memory and can eliminate tumor or infected cells, antigen-specific CD8(+) T cell inducing DNA vaccines are potential next-generation vaccines. However, the relationship between single amino acid deletion of target antigens in plasmid DNA vaccines and vaccine efficacy is not completely understood. To address this knowledge disparity and improve DNA vaccine development, two constructs cytosolic form of ovalbumin, pOVAv (346 amino acids) and pOVAy (345 amino acids) were constructed and compared. OVA proteins from both constructs were detected in an in vitro experiment. Then, the efficacy of prophylactic DNA vaccination using a gene gun against OVA-expressing mouse thymoma cells was compared. Both constructs conferred protection against tumor challenge, and there was no significant difference between the efficacies of pOVAv and pOVAy. The pOVAv vaccine induced stronger antigen-specific cytotoxicity in vivo, while bone marrow-derived dendritic cells (BMDCs) transfected with pOVAv induced higher levels of IFN-γ production from OT-I CD8(+) T cells in vitro compared to pOVAy. These results indicate that a single amino acid deletion at N-terminus of the target antigen in a DNA vaccine leads to a different immunological outcome. The small modification of the target antigen in the DNA vaccine might improve its efficacy against tumor or infectious diseases.