Review on Recent Advance of Vaccine Adjuvants

Vaccines are the most feasible and cost-effective strategy for protecting, controlling and reducing infectious disease in both animal species and humans. Despite, the significant use of vaccines, formulation of effective and safe vaccine is needed to afford sufficient protection through usage of appropriate adjuvants. Adjuvants are chemicals, proteins or derivatives of microbial formulated with vaccines to enhance innate and adaptive immune response to vaccine antigens by a variety of mechanisms. The term adjuvant comes from Latin word “adjuvare” which means to help and discovered in early 1920s. Many molecules have been considered as an adjuvant including aluminium salts (alum), oil emulsions, saponins, ISCOMs, liposomes, VLPs, cytokines, combined adjuvants and derivatives of bacteria are among in use and explored vaccine adjuvants. Mainly they have been classified according to their mechanism of action as: delivery system and immunostimulatory adjuvants. The mode of action of these compounds is different. Their action is not yet fully understood due to the complexity of the immune response, but general mechanism has been explained. Recent advances of vaccine adjuvants reveal their ability to activate innate immune system by targeting receptors (PRR) expressed on immune cells. Therefore, discovering new adjuvant that are essential components of vaccine formulations helps the development of more potent vaccine, which induce strong immune response. Better understanding of new adjuvant also improves the future design of effective vaccine against infectious pathogens. This review, provide an overview on current knowledge about the effect of adjuvants, general mechanisms and characteristics of recent vaccine adjuvants.