Host-Derived Cytokines and Chemokines as Vaccine Adjuvants

The increased knowledge about immunological concepts and systems nowadays helps to rationally enhance the performance of, and to overcome some of the problems, that are associated with inactivated vaccines. Because the antigenic component of an inactivated vaccine by itself only gives a limited or no activation of the immune system, the addition of an adjuvant is required to induce a strong and an adequate type of immune response. However, this may be associated with unacceptable local reactions. To overcome this safety issue and to further enhance the performance of "first-generation" adjuvants, research is currently addressing new types of adjuvants that are both safe and strong. A solution for the generation of safe and strong adjuvants without unwanted, or minimal, local reactions can be found within the use of the so-called host-derived immunostimulating or modulating molecules, e.g., intercellular signaling molecules like cytokines and cell traffic-directing chemokines. As these molecules are host derived, and therefore often species specific, they have been shown to induce highly acceptable local reactions (if any) in contrast to many "first-generation" adjuvants. Proper efficacy of these molecular adjuvants requires optimal dosing and timing.