BRLF1 suppresses RNA Pol III-mediated RIG-I inflammasome activation in the early EBV lytic lifecycle

Latent infection with herpesviruses constitutively activates inflammasomes, while lytic replication suppresses their activation through distinct mechanisms. However, how Epstein–Barr virus (EBV) lytic replication inhibits the activation of inflammasomes remains unknown. Here, we reveal that the EBV immediate-early protein BRLF1 inhibits inflammasome activation, and BRLF1 deficiency significantly increases the activation of inflammasomes and pyroptosis during early lytic lifecycle. BRLF1 interacts with RNA polymerase III subunits to suppress immunostimulatory small RNA transcription, RIG-I inflammasome activation, and antiviral responses. Consequently, BRLF1-deficient EBV primary infection induces robust T-cell and NK cell activation and killing through IL-1β and IL-18. A BRLF1-derived peptide that inhibits inflammasome activation is sufficient to suppress T-cell and NK cell responses during BRLF1-deficient EBV primary infection in lymphocytes. These results reveal a novel mechanism involved in the evasion of inflammasome activation and antiviral responses during EBV early lytic infection and provide a promising approach for the manipulation of inflammasomes against infection of oncogenic herpesviruses. Synopsis The Epstein-Barr virus immediate-early protein BRLF1 interacts with RNA polymerase III subunits and inhibits RIG-I-inflammasome activation. Primary infection with BRLF1-deficient EBV induces T cell and NK cell activation and virus killing. BRLF1 inhibits inflammasome activation and pyroptosis during the EBV lytic lifecycle. BRLF1 interacts with RNA-POL III to suppress immunogenic small RNA transcription and 5ʹ-ppp-RNA production. BRLF1 inhibits RNA polymerase III-mediated RIG-I inflammasome activation and antiviral responses. BRLF1-deficient EBV activates T cells and NK cells through inflammasome-dependent IL-1β and IL-18 secretion. Graphical Abstract The Epstein-Barr virus immediate-early protein BRLF1 interacts with RNA polymerase III subunits and inhibits RIG-I-inflammasome activation. Primary infection with BRLF1-deficient EBV induces T cell and NK cell activation and virus killing.