A bacterial fatty acid enzyme hijacks nucleic acid–sensing Toll-like receptor signaling
2026-08-06
Innate immune recognition shapes infection outcomes by linking microbial detection to host defense. Although pattern recognition receptors are classified by the ligands they detect (lipids, peptidoglycans, or nucleic acids) cross-talk between these pathways is increasingly recognized. Staphylococcus aureus , a major cause of skin and soft tissue infections, can persist intracellularly, evading immunity and antibiotics. Here, we describe a lipid-based immune evasion strategy in which the S. aureus enzyme oleate hydratase (OhyA) converts host fatty acids into hydroxylated lipids that antagonize TLR3–TRIF–IRF7 signaling, a pathway activated by double-stranded RNA. Deletion of ohyA unleashed this pathway, triggering rapid bacterial clearance, whereas loss of TLR3, TRIF, or IRF7 restored bacterial persistence, establishing a noncanonical antibacterial role for an antiviral signaling pathway. These findings identify a previously unrecognized interface between bacterial lipid metabolism and antiviral immune machinery, highlighting how pathogens manipulate cross-kingdom signaling to evade intracellular immunity.