– Cyclic diadenylate (c-di-AMP) sodium functions as a STING agonist by binding to the STING transmembrane protein, thus activating the TBK3-IRF3 signaling pathway. This activation prompts the production of type I IFN and TNF. Additionally, c-di-AMP sodium serves as a bacterial second messenger in Gram-positive bacteria, where it plays crucial roles in regulating cell growth, survival, and virulence, as well as the host immune response. It also acts as a potent mucosal adjuvant by stimulating both humoral and cellular responses [1] [2] [3] [4].