Enhancing DNA vaccine potency by coadministration of DNA encoding antiapoptotic proteins

Intradermal vaccination by gene gun efficiently delivers DNA vaccines into DCs of the skin, resulting in the activation and priming of antigen-specific T cells in vivo. DCs, however, have a limited life span, hindering their long-term ability to prime antigen-specific T cells. We reason that a strategy that prolongs the survival of DNA-transduced DCs will enhance priming of antigen-specific T cells and DNA vaccine potency. Here we show that codelivery of DNA encoding inhibitors of apoptosis (BCL-xL, BCL-2, XIAP, dominant negative caspase-9, or dominant negative caspase-8) with DNA encoding model antigens prolongs the survival of transduced DCs. More importantly, vaccinated mice exhibited significant enhancement in antigen-specific CD8⁺ T cell immune responses, resulting in a potent antitumor effect against antigen-expressing tumors. Among these antiapoptotic factors, BCL-xL demonstrated the greatest enhancement in antigen-specific immune responses and anti-tumor effects. Thus, coadministration of DNA vaccines with DNA encoding antiapoptotic proteins represents an innovative approach to enhance DNA vaccine potency.