Ginsenoside Rg3 enriches SCFA-producing commensal bacteria to confer protection against enteric viral infection via the cGAS-STING-type I IFN axis

The microbiota-associated factors that influence host susceptibility and immunity to enteric viral infections remain poorly defined. We identified that the herbal monomer ginsenoside Rg3 (Rg3) can shape the gut microbiota composition, enriching robust short-chain fatty acid (SCFA)-producing Blautia spp. Colonization by representative Blautia coccoides and Blautia obeum could protect germ-free or vancomycin (Van)-treated mice from enteric virus infection, inducing type I interferon (IFN-I) responses in macrophages via the MAVS-IRF3-IFNAR signaling pathway. Application of exogenous SCFAs (acetate/propionate) reproduced the protective effect of Rg3 and Blautia spp. in Van-treated mice, enhancing intracellular Ca(2+)- and MAVS-dependent mtDNA release and activating the cGAS-STING-IFN-I axis by stimulating GPR43 signaling in macrophages. Our findings demonstrate that macrophage sensing of metabolites from specific commensal bacteria can prime the IFN-I signaling that is required for antiviral functions.