Immunological properties of gene vaccines delivered by different routes

Gene vaccines represent a new and promising approach to control infectious diseases, inducing a protective immune response in the appropriate host. Se veral routes and methods of genetic immunization have been shown to induce antibody production as well as T helper (Th) cell and cytotoxic T lymphocyt e activation. However, few studies have compared the nature of the immune r esponses generated by different gene vaccination delivery systems. Ln the p resent study we reviewed some aspects of immunity induced by gene immunizat ion and compared the immune responses produced by intramuscular (im) DNA in jection to gene gun-mediated DNA transfer into the skin of BALB/c mice. Usi ng a reporter gene coding for beta-galactosidase, we have demonstrated that im injection raised a predominantly Th1 response with mostly IgG2a anti-be ta gal produced, while gene gun immunization induced a mixed Th1/Th2 profil e with a balanced production of IgG2a and IgG1 subclasses. Distinct types o f immune responses were generated by different methods of gene delivery. Th ese findings have important implications for genetic vaccine design. Firstl y, a combination between these two systems may create optimal conditions fo r the induction of a broad-based immune response. Alternatively, a particul ar gene vaccine delivery method might be used according to the immune respo nse required for host protection. Here, we describe the characteristics of the immune response induced by gene vaccination and the properties of DNA i nvolved in this process.