ALOX15 orchestrates mitochondrial antiviral immunity and serves as a host target for anti-influenza therapy.

Viral infections trigger cellular stress responses, and host stress proteins play key roles in antiviral defense. Here we identify stress-responsive protein arachidonate lipoxygenase-15 (ALOX15) is a critical component of mitochondrial antiviral innate immunity. Loss of Alox15 impairs mitochondrial antiviral signaling (MAVS)-mediated type I interferon production, resulting in increased susceptibility to influenza virus, an effect reversed by adeno-associated virus-mediated lung delivery of Alox15. ALOX15 translocates to mitochondria in response to H1N1 and other RNA viruses (H3N2 and human coronavirus-229E), independent of its enzymatic activity. This mitochondrial localization is also strikingly observed in peripheral blood mononuclear cells from influenza-infected individuals. Mechanistically, ALOX15 is recruited to mitochondria by polymerized MAVS, displacing the deubiquitinase USP19 and sustaining MAVS K63-linked ubiquitination and aggregation. Leveraging these insights, we developed a synergistic ALOX15 regulation-based therapeutic strategy for influenza infection by combining the ALOX15 transcriptional activator songorine with its enzymatic inhibitor PD146176. Together, our findings establish ALOX15 as an essential component of mitochondrial antiviral immunity and a promising host-directed target for antiviral therapy.