Novel adjuvant systems.

Vaccination remains the single most valuable tool in the prevention of infectious disease. Nevertheless, there exists a need to improve the performance of existing vaccines such that fewer boosts are needed or to develop novel vaccines. For the development of effective vaccines for humans, a great need exists for safe and effective adjuvants. A number of novel adjuvants have been reported in recent years including: i) bacterial toxins such as cholera toxin, CT, and the Escherichia coli heat-labile enterotoxin, LT; ii) less toxic derivatives of CT and LT; iii) endogenous human immunomodulators, such as IL-2, IL-12, GM-CSF; iv) hormones; v) lipopeptides; vi) saponins, such as QS-21; vii) synthetic oligonucleotides containing CpG motifs (CpG ODN); viii) lipid 'A derivatives, such as monophosphoryl lipid A, MPL, and ix) muramyl dipeptide (MDP) derivatives. Herein, we will review recent findings using these novel adjuvant systems.

Optimization strategies for DNA vaccines.

DNA immunization is a relatively new vaccination strategy that involves the direct introduction into the host of plasmid DNA encoding the desired antigen. The DNA enters host cells and results in immune responses following in vivo expression of the antigen. Although DNA-based immunization works well in animal models for the induction of both humoral and cell-mediated immune responses, its success in humans has been limited. This paper discusses different approaches that have attempted to optimize DNA vaccines, and presents results evaluating some of these approaches in mice.