Adjuvants

A prominent feature that underscores the current era of vaccinology is the ability to generate a huge variety of antigens (Ag) by various synthetic chemistry and genetic engineering techniques. As a result, Ags now can be produced rapidly and in large quantities with well-defined structures and in highly purified forms-desirable attributes for their use in vaccines intended to generate Ag-specific immune responses in a diverse population. Unfortunately, the routine use of these Ags as integral components of vaccines is encumbered by their inherent lack of immunogenicity. Such vaccines, therefore, require the use of adjuvants in order to potentiate and focus the immune response to the Ag so that optimal immune outcome can be achieved. Thus, the discovery and development of new adjuvants is of growing importance to the design of vaccines capable of meeting the modern threats posed to human and animal populations by new or resurgent infectious and non-infectious diseases. This chapter will highlight recent trends in the development of novel adjuvants and, to the extent to which it is known, their immunologic mechanisms. A particular emphasis will be place on those adjuvants composed of single molecular entities, the so called molecular adjuvants.