Co-delivery of PSA and PSMA DNA vaccines with electroporation induces potent immune responses

Prostate cancer (PCa) remains a significant public health problem. Current treatment modalities for PCa can be useful, but may be accompanied by deleterious side effects and often do not confer long-term control. Accordingly, additional modalities, such as immunotherapy, may represent an important approach for PCa treatment. The identification of tissue-specific antigens engenders PCa an attractive target for immunotherapeutic approaches. Delivery of DNA vaccines with electroporation has shown promising results for prophylactic and therapeutic targets in a variety of species including humans. Application of this technology for PCa immunotherapy strategies has been limited to single antigen and epitope targets. We sought to test the hypothesis that a broader collection of antigens would improve the breadth and effectiveness of a PCa immune therapy approach. We therefore developed highly optimized DNA vaccines encoding prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) as a dual antigen approach to immune therapy of PCa. PSA- and PSMA-specific cellular immunogenicity was evaluated in a mouse model for co-delivery and single antigen vaccination. Mice received 2 immunizations spaced 2 weeks apart and immunogenicity was evaluated 1 week after the second vaccination. Both the PSA and PSMA vaccines induced robust antigen-specific IFN gamma responses by ELISpot. Further characterization of cellular immunogenicity by flow cytometry indicated strong antigen-specific TNF alpha production by CD4(+) T cells and IFN gamma and IL-2 secretion by both CD4(+) and CD8(+) T cells. There was also a strong humoral response as determined by PSA-specific seroconversion. These data support further study of this novel approach to immune therapy of PCa.