Dendritic cell discoveries provide new insight into the cellular immunobiology of DNA vaccines

The evolution of increasingly virulent human pathogens, together with the rapid onset of antimicrobial resistance has created a need for new vaccination strategies. Nucleic acid vaccines, based on recombinant DNA technology are a promising new vaccine formulation capable of eliciting both humoral and cellular immune responses. This technology has been experimentally validated in animal models of pathogen challenge and tumor protection following administration of a DNA vaccine and has led to extensive research into the mechanisms of protective immunity. We focus here on the cellular and molecular mechanisms leading to cell-mediated immune responses to DNA vaccines and discuss these mechanisms in light of recent advances in the field of dendritic cell immunobiology. In particular, the potential involvement of: (i) the CpG pattern-recognition receptor, toll-like receptor-9; (ii) the dendritic cell-specific surface adhesion molecule, DC-SIGN; and (iii) the molecular interactions between CD40 and CD154 in the evolution of protective cell-mediated immunity to DNA vaccines are discussed. An improved understanding of the precise mechanisms leading to protective cellular immunity following DNA vaccination may help in the design of novel DNA constructs containing immunostimulatory features that target one or more of these mechanisms, with the aim of increasing the immunogenic potential and protective efficacy of DNA vaccines.