IFI44 Functions as a Positive Regulator of Type I Interferon Signaling to Restrict Zika Virus Infection.

Zika virus (ZIKV) infection is known to cause microcephaly in newborns, and its outbreaks have previously emerged as a global public health crisis. The lack of a preventive vaccine or specific antiviral drugs underscores the urgency of investigating the detailed mechanisms of pathogenesis. We identified that interferon-induced protein 44 (IFI44) is significantly upregulated following ZIKV infection, but its role in ZIKV pathogenesis remains unclear. Using A549 and 2FTGH cells, we established ZIKV-infected cell models and employed quantitative real-time PCR and Western blotting to demonstrate that IFI44 overexpression suppressed ZIKV replication, whereas IFI44 knockdown via specific small interfering RNA promoted viral replication. Mechanistically, IFI44 inhibited early-stage ZIKV infection, including viral attachment and entry into host cells. Further analyses revealed that IFI44 promoted IFN-β expression, triggering activation of the Jak/STAT signaling pathway-as evidenced by increased phosphorylated STAT1 (p-STAT1), enhanced interferon-stimulated response element activity, and upregulated the downstream interferon-stimulated genes (MX1, OAS2, IFIT2, and RIG-I). Collectively, these findings demonstrate that ZIKV infection induced IFI44 expression, which acts as a positive feedback regulator of the Jak/STAT pathway to restrict viral replication. Our results establish IFI44 as a key component of the host antiviral response against ZIKV, highlighting its potential as a therapeutic target.