Antitumor Effect of a DNA Vaccine Harboring Prostate Cancer-Specific Antigen with IL-12 as an Intramolecular Adjuvant

To improve the lower immune intensity of DNA vaccines, we developed a DNA vaccine based on prostate cancer-specific antigen (PSA), which has been suggested as a potential target for prostate cancer therapy, and enhanced the DNA vaccine potency using interleukin-12 (IL-12) as an intramolecular adjuvant. A series of DNA plasmids encoding human PSA, IL-12, and their conjugates was constructed and injected into female mice intramuscularly, followed by an electric pulse. The humoral and cellular immune responses after immunization were detected by ELISA and ELISPOT, respectively. To evaluate the therapeutic efficacy of these plasmids, a mouse model with a PSA-expressing tumor was constructed. Mice vaccinated with PSA-IL-12 plasmids elicited the strongest PSA-specific humoral and cellular immune responses. Furthermore, these vaccinations inhibited the growth of PSA-expressing tumors and prolonged mouse survival. These observations emphasize the potential of the IL-12 gene as an intramolecular adjuvant for DNA vaccines. Moreover, the vaccine based on PSA and IL-12 may be a promising treatment for prostate cancer.