Adopting STING agonist cyclic dinucleotides as a potential adjuvant for SARS-CoV-2 vaccine

A novel STING agonist CDG ^SF unilaterally modified with phosphorothioate and fluorine was synthesized. CDG ^SF displayed better STING activity over dithio CDG. Immunization of SARS-CoV-2 Spike protein with CDG ^SF as an adjuvant elicited an exceptional high antibody titer and a robust T cell response, which were better than the group using aluminium hydroxide as a adjuvant. These results highlighted the adjuvant potential of STING agonist in SARS-CoV-2 vaccine preparation for the first time.