3',3'-cGAMP (3',3'-cyclic GMP-AMP, Cyclic GMP-AMP, cGAMP) activates the endoplasmic reticulum (ER)-resident receptor stimulator of interferon genes (STING), thereby inducing an antiviral state and the secretion of type I IFNs.
Sublingual immunization of mice with Bacillus anthracis protective antigen (PA) and the STING ligand 3′3′-cGAMP promotes PA-specific serum IgG Ab responses of the same magnitude as those induced after immunization with PA and the experimental adjuvants cholera toxin (CT). 3′3′-cGAMP also promotes serum anti-PA IgA and IgA-producing cells in the bone marrow. Furthermore, the saliva of mice immunized with 3′3′-cGAMP exhibits similar levels of PA-specific IgA Abs as groups immunized with CT as adjuvant. The adjuvant activity of 3′3′-cGAMP is associated with mixed Th1, Th2, and Th17 responses. 3′3′-cGAMP also induces rapid IFN-β and IL-10 responses in sublingual tissues and cervical lymph nodes, and TGF-β responses in the cervical lymph nodes, which can contribute to promoting IgA responses after sublingual immunization.[1]
[1] Tara L Martin, et al. Vaccine. 2017 Apr 25;35(18):2511-2519.