Taurolithocholic acid protects against viral haemorrhagic fever via inhibition of ferroptosis.

Bile acids are microbial metabolites that can impact infection of enteric and hepatitis viruses, but their functions during systemic viral infection remain unclear. Here we show that elevated levels of the secondary bile acid taurolithocholic acid (TLCA) are associated with reduced fatality rates and suppressed viraemia in patients infected with severe fever with thrombocytopenia syndrome virus (SFTSV), an emerging tick-borne haemorrhagic fever virus. TLCA inhibits viral replication and mitigates host inflammation during SFTSV infection in vitro, and indirectly suppresses SFTSV-mediated induction of ferroptosis by upregulating fatty acid desaturase 2 via the TGR5-PI3K/AKT-SREBP2 axis. High iron and ferritin serum levels during early infection were correlated with decreased TLCA levels and fatal outcomes in SFTSV-infected patients, indicating potential biomarkers. Furthermore, treatment with either ferroptosis inhibitors or TLCA protected mice from lethal SFTSV infection. Our findings highlight the therapeutic potential of bile acids to treat haemorrhagic fever viral infection.