Host-directed antiviral strategy targeting prohibitins: Mel56 suppresses influenza A virus and severe acute respiratory syndrome coronavirus 2 via modulation of antioxidant pathways and mitochondrial function

ABSTRACT Respiratory viruses, such as influenza A virus (IAV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remain major global health threats, and the emergence of drug-resistant variants underscores the urgent need for host-targeted antiviral strategies. Prohibitins (PHBs), mitochondrial scaffold proteins involved in diverse cellular processes, are host factors exploited by multiple viruses. Here, we investigated the antiviral potential of two PHB-binding triazine melanogenin derivatives, Mel56 and Mel6, against IAV and SARS-CoV-2. Mel56, but not Mel6, exhibited potent anti-IAV activity. In particular, Mel56 increased cell survival, suppressed viral nucleoprotein expression, and reduced viral gene transcription in IAV-infected Madin-Darby canine kidney (MDCK) cells and A549 human lung carcinoma cells. PHB2 knockdown enhanced the inhibitory effect of Mel56, supporting the involvement of PHBs in its antiviral mechanism. Transcriptomic profiling revealed that Mel56 downregulates virus-induced immune response genes while upregulating antioxidant response-related genes, including nuclear factor erythroid 2-related factor 2 (NRF2) target genes. NRF2 activation by Mel56 was confirmed using a reporter assay. Consistent with these findings, Mel56 impaired mitochondrial ATP synthesis and electron transport in isolated rat liver mitochondria and attenuated mitochondrial membrane potential and promoted mitochondrial reactive oxygen species production in live MDCK cells. Importantly, Mel56 exhibited potent anti-SARS-CoV-2 activity in human induced pluripotent stem cell-derived lung organoids. Mel56 did not upregulate NRF2 target genes in SARS-CoV-2-infected organoids. These findings identify Mel56 as a PHB-binding compound with broad-spectrum antiviral activity and support the development of PHB-targeting ligands as a novel host-directed therapeutic strategy against respiratory viral infections. IMPORTANCE This study identifies Mel56 as a novel host-directed antiviral compound that targets prohibitins and suppresses both influenza A virus and severe acute respiratory syndrome coronavirus 2. Mel56 exhibits broad-spectrum antiviral activity in conventional cell culture models as well as in physiologically relevant human lung organoids. Mechanistically, Mel56 upregulates antioxidant response-related genes, activates nuclear factor erythroid 2-related factor 2, impairs mitochondrial function, and enhances mitochondrial reactive oxygen species production. Notably, its effects differ depending on the cellular context, underscoring the complexity of host signaling pathways during viral infection. These findings highlight prohibitins as promising therapeutic targets and provide proof of concept for the development of host-directed strategies to combat respiratory viruses and mitigate the emergence of drug resistance.