Viral hijacking of host DDX60 promotes Crimean-Congo haemorrhagic fever virus replication via G-quadruplex unwinding.

Crimean-Congo haemorrhagic fever virus (CCHFV) is the most prevalent tick-borne zoonotic bunyavirus, causing severe hemorrhagic fever and fatality in humans. Currently, the absence of approved vaccines or therapeutics for CCHFV infection necessitates the development of innovative therapeutic strategies. Here, we identify a guanine (G)-rich sequence located within the mRNA of the glycoprotein precursor in the medium (M) segment of the CCHFV genome, designated as M-PQS-1664(+). M-PQS-1664(+) can form stable G-quadruplex (G4) structure and functions as a negative regulatory element for viral replication. Host DDX60 is up-regulated in response to CCHFV infection, thereby it is hijacked to unwind M-PQS-1664(+) G4 for facilitating viral replication. The FDA-approved drug Cepharanthine (CEP), which competes with DDX60 to specifically stabilize M-PQS-1664(+) G4 without a global induction of host cellular G4s formation, exhibits remarkable antiviral activity in vitro and in vivo. More importantly, CEP possesses antiviral activity (50% inhibitory concentration ~ 0.2 μM) that having ~ 88 × the potency of ribavirin. Our findings underscore the CCHFV G4s as a promising target for drug development and highlight the significant potential of CEP in combating CCHFV.