Recent Advances in the Discovery and Delivery of TLR7/8 Agonists as Vaccine Adjuvants

The need for new adjuvants is absolutely cardinal to the development of new vaccines and to further optimizing current immunization approaches. However, only a few classes of adjuvants are presently incorporated in vaccines approved for human use. Recent advances in the discovery and delivery of TLR agonists as vaccine adjuvants have begun to open up a new toolbox for vaccinologists. At the forefront of this movement is the use of synthetic small molecule TLR7/8 agonist-based adjuvants. In this review, we emphasize the importance of vaccine formulation science in driving recent developments in TLR7/8 adjuvanticity, summarize some of the most current and notable studies in this field, and discuss desirable attributes of next generation TLR7/8 adjuvants for use in enhancing vaccine responses in vulnerable populations, such as the very young. Finally, we explore advances that may further edge the development of TLR7/8 adjuvant-based vaccine formulations toward clinical human evaluation.