DNA vaccine strategies: candidates for immune modulation and immunization regimens.

DNA vaccine strategies can differ greatly, with significant effects on the outcome of immunization. In this article, we discuss plasmid design strategies and vaccine regimens. Effectiveness against a pathogen can be affected by the choice of antigen and inclusion of multiple antigens. Gene expression and the resulting immune response can be improved by gene modification and choice of promoters. In designing vaccine regimens, one must consider further dose, timing of doses, adjuvants, and routes of vaccination. Many vaccines are enhanced by combining DNA with other vaccines in "prime-boost" regimens, in which the second vaccine is often a recombinant viral vector or purified protein subunit. Prime-boost vaccines including DNA can elicit immune responses that differ in magnitude, quality, and balance of cellular and humoral responses from those elicited by single components and thus provide further enhancement for DNA immunizations.