Natural vaccine adjuvants from traditional Chinese medicines: Mechanisms to applications

With the rapid advancement of vaccines, the research and application of vaccine adjuvants have garnered significant attention. Despite the development of numerous vaccine adjuvants, their applications in human vaccines remain limited due to either insufficient efficacy or severe side effects. Consequently, there is growing interest in developing bioactive compounds derived from traditional Chinese medicines (TCMs) as vaccine adjuvants, owing to their natural biocompatibility, diversity, and safety. Here, we systematically review the current application status and potential value of TCM-based bioactive compounds in vaccine adjuvants. Firstly, we elaborate on the types and characteristics of active ingredients, such as polysaccharides, saponins, flavonoids, acids, and alkaloids. The mechanisms by which these compounds function as vaccine adjuvants are then discussed, including their roles in enhancing humoral immunity, cellular immunity, and relieving the immune suppression in the microenvironment. Additionally, we summarize the current strategies for structural modification and platform optimization to adapt to different application scenarios. Finally, we offer insights into the future development directions for these potential adjuvants, highlighting research priorities, technical approaches, and application prospects. In conclusion, natural vaccine adjuvants derived from TCMs present broad application prospects and hold promise for future vaccine development.