Codon-Optimized P1A-Encoding DNA Vaccine: Toward a Therapeutic Vaccination against P815 Mastocytoma

Abstract

DNA vaccine can be modified to increase protein production and modulate immune response. To enhance the efficiency of a P815 mastocytoma DNA vaccine, the P1A gene sequence was optimized by substituting specific codons with synonymous ones while modulating the number of CpG motifs. The P815A murine antigen production was increased with codon-optimized plasmids. The number of CpG motifs within the P1A gene sequence modulated the immunogenicity by inducing a local increase in the cytokines involved in innate immunity. After prophylactic immunization with the optimized vaccines, tumor growth was significantly delayed and mice survival was improved. Consistently, a more pronounced intratumoral recruitment of CD8+ T cells and a memory response were observed. Therapeutic vaccination was able to delay tumor growth when the codon-optimized DNA vaccine containing the highest number of CpG motifs was used. Our data demonstrate the therapeutic potential of optimized P1A vaccine against P815 mastocytoma, and they show the dual role played by codon optimization on both protein production and innate immune activation.

Combination of immune checkpoint blockade with DNA cancer vaccine induces potent antitumor immunity against P815 mastocytoma

“…The infiltration of antigen-specific CD8 T cells in the group treated with pP1A alone was not significantly different from that in the untreated group. These results suggest that the vaccine alone is not effective in inducing a sufficiently potent immune response in a therapeutic setting due to the immunosuppressive tumor microenvironment, confirming our previous findings 10 . Most likely, the vaccine alone may not be able to ensure sustained CD8 T cell infiltration into the tumor, which could explain the rare presence of antigen-specific CD8 T cells in the tumor.…”

“…However, the difference between ICBs and pP1A + ICBs was not statistically significant despite the higher survival trend observed in the group treated with the pP1A + ICB combination. The result obtained with pP1A alone confirmed our previous work on this tumor model, indicating the ability of a DNA vaccine to slowdown the tumor growth, but not to permit a complete and significant tumor rejection 10 . The combination of pP1A with ICB further decreased tumor growth even if the doses of ICBs used in this study were lower than others that employed the same therapeutic combination (100 µg compared to 200–250 µg per dose, per antibody) 3 , 11 .…”

“…The P1A DNA vaccine encoding the P1A antigen gene (here named plasmid P1A, pP1A) has been previously described 10 . The plasmid was amplified and purified using an EndoFree Plasmid Giga Kit (Qiagen, Venlo, NL) according to the manufacturer’s protocol.…”

“…P815A shares many characteristics with human MAGE-type (melanoma antigen gene) tumor antigens 9 , suggesting P815 mastocytoma as a good preclinical tumor model for future applications in human medicine. We have previously developed a codon-optimized vaccine encoding P815A 10 . We demonstrated that the optimized vaccine increased antigen expression and activated innate immunity while retarding tumor growth in both preventive and therapeutic settings 10 .…”

“…We have previously developed a codon-optimized vaccine encoding P815A 10 . We demonstrated that the optimized vaccine increased antigen expression and activated innate immunity while retarding tumor growth in both preventive and therapeutic settings 10 . However, therapeutic vaccination delayed tumor growth but only slightly increased the survival of mice.…”