Elevated interferon-induced transmembrane protein 3 in platelets and megakaryocytes suppresses Crimean-Congo hemorrhagic fever viral infection by interacting with glycoprotein Gc.

Crimean-Congo hemorrhagic fever (CCHF) is a hemorrhagic fever caused by infection with the CCHF virus (CCHFV) and has a mortality rate of up to 30 ​%. Thrombocytopenia is a hallmark of CCHF; however, the mechanisms underlying this manifestation remain poorly understood. In addition to hemostasis, platelets play a crucial role in recognizing pathogens and mediating immune responses. We investigated the mechanisms underlying thrombocytopenia associated with CCHFV infection by analyzing the platelet transcriptome in mice. Interferon-induced transmembrane protein 3 (IFITM3), a known antiviral factor, was significantly upregulated. The role of IFITM3 in response to CCHFV infection was characterized using the human megakaryoblast cell line MEG-01, considered a parental cell line of platelets. Although the CCHFV infection rate was limited, MEG-01 ​cells maintained the infection and replication of CCHFV, leading to increased IFITM3 protein expression. We demonstrated that IFITM3 overexpression efficiently inhibited CCHFV infection, whereas IFITM3 knockout promoted viral infection. An interaction between IFITM3 and the CCHFV glycoprotein Gc was identified, which suppressed CCHFV entry into cells. The IFITM3 CIL-TMD domain is critical for this interaction. These results suggest that IFITM3 is a restriction factor and plays an antiviral role during CCHFV infection. Elevated expression of IFITM3 in platelets indicates that this could be a common mechanism by which platelets protect against viruses, including CCHFV, which may reduce platelet consumption and destruction caused by CCHFV infection. These findings provide valuable insights into the pathogenesis of CCHF-associated thrombocytopenia and offer foundational theoretical support for future therapeutic strategies.