These findings establish ALOX15 as an essential component of mitochondrial antiviral immunity and a promising host-directed target for antiviral therapy, identifying ALOX15 as a host-directed target for anti-influenza therapy.
During viral infection and tissue injury, efficient immune clearance of infected or damaged cells is crucial for host defense and homeostasis. Here, we identify mitochondrial RNA (mtRNA) as a broad-spectrum damage-associated molecular pattern (DAMP) that coordinates antiviral and damage-related immune clearance. Through an integrative approach combining in vitro cellular assays and multi-strain murine models, we demonstrate that viral infection and cellular stress promote POLRMT-dependent mtRNA synthesis and its release into the cytosol through BAX/mPTP-mediated mitochondrial pores. Once released, mtRNA activates the MAVS signaling pathway, triggering a robust type I interferon response that operates independently of the cGAS-STING axis. Notably, viruses exploit a negative feedback loop for immune evasion: type I interferon upregulates the exoribonuclease PNPT1, which degrades cytosolic mtRNA and thereby dampens the mtRNA-MAVS axis. Critically, pharmacological inhibition of PNPT1 with lanthanum chloride (LanC), combined with BH3 mimetics that relieve the BCL-2-mediated blockade of BAX/BAK pores, synergistically reactivates mtRNA release and restores antiviral immunity. This dual strategy demonstrates potent antiviral and anti-fibrotic efficacy in preclinical models without significant toxicity. Our findings establish the mtRNA-MAVS axis as a central, broadly applicable immune surveillance pathway and provide a mechanistic framework for developing therapies that overcome both viral immune evasion and the limitations of current STING-targeted agonists.
Mingfu Tian, Guangli Li, Zelin Chai et al.· Cell Death & Disease· 0 citations
ABSTRACT Influenza A viruses (IAVs) pose an ongoing threat to humans and other species because of their zoonotic potential. Accumulating evidence has demonstrated that certain long non-coding RNAs (lncRNAs) exhibit differential expression during viral infection and modulate diverse facets of viral pathogenesis. As key regulatory RNAs, lncRNAs participate in fundamental physiological processes and disease progression via a wide array of functional interactions with DNA, RNA, and proteins. Here, we identified ckATP1A1-AS1 as an antiviral host lncRNA that is induced by IAV infection. Functional analyses demonstrated that ckATP1A1-AS1 overexpression restricted infection by multiple IAV subtypes, whereas ckATP1A1-AS1 knockdown enhanced viral replication. Mechanistically, during IAV infection, the transcription factor JUN transcriptionally activates ckATP1A1-AS1, which further enhances the expression of interferon-β and key interferon-stimulated genes, thereby positively regulating type I interferon immune responses. Furthermore, ckATP1A1-AS1 interacts directly with the viral nucleoprotein, competitively disrupting its binding to importin α5, impairing its oligomerization, and blocking the nuclear import of viral ribonucleoprotein complexes. Consequently, ckATP1A1-AS1 suppresses viral ribonucleoprotein assembly and reduces viral polymerase activity. These findings establish ckATP1A1-AS1 as a key antiviral lncRNA that restricts IAV replication by coordinating innate immune signaling and directly targeting several steps in the viral replication cycle. IMPORTANCE Accumulating evidence indicates that host long non-coding RNAs (lncRNAs) play important roles in regulating virus–host interactions during influenza A virus (IAV) infection. However, the functions and mechanisms of action of most IAV-associated lncRNAs remain unclear. This study identifies the novel chicken antisense lncRNA ckATP1A1-AS1 as a key antiviral factor with a unique dual mechanism: it is transcriptionally activated by transcription factor JUN and, in turn, upregulates the expression of interferon-β and key interferon-stimulated genes to positively regulate the type I interferon immune response. It directly interacts with viral nucleoprotein, competitively disrupting the binding of nucleoprotein to importin α5 and impairing nucleoprotein oligomerization, thereby suppressing viral ribonucleoprotein assembly and reducing viral polymerase activity. Accumulating evidence indicates that host long non-coding RNAs (lncRNAs) play important roles in regulating virus–host interactions during influenza A virus (IAV) infection. However, the functions and mechanisms of action of most IAV-associated lncRNAs remain unclear. This study identifies the novel chicken antisense lncRNA ckATP1A1-AS1 as a key antiviral factor with a unique dual mechanism: it is transcriptionally activated by transcription factor JUN and, in turn, upregulates the expression of interferon-β and key interferon-stimulated genes to positively regulate the type I interferon immune response. It directly interacts with viral nucleoprotein, competitively disrupting the binding of nucleoprotein to importin α5 and impairing nucleoprotein oligomerization, thereby suppressing viral ribonucleoprotein assembly and reducing viral polymerase activity.
Menglu Fan, Zhiyuan Liu, Lu-Lu Deng et al.· Journal of Virology· 0 citations
Dysregulation of innate immunity during respiratory RNA virus infections drives systemic hyperinflammation and lung injury. Here, we show that importin β4 (IPO4) has a role in inhibiting antiviral innate immunity. Transcriptomics analysis illustrated a downregulation of IPO4 in alveolar macrophages, lung ciliated epithelium, and peripheral blood mononuclear cells from severely ill patients with COVID-19 or influenza. We further identified CCAAT/enhancer-binding protein beta (CEBPB) as the transcription factor for IPO4 reduction during RNA viral infections. Loss-of-function validation demonstrated that IPO4 dampens the innate antiviral and inflammatory responses in vitro and in vivo. Mechanistically, IPO4 sequesters fatty acid synthase (FASN) to block palmitic acid production, thereby inhibiting mitochondrial antiviral signaling protein (MAVS) activation and the downstream innate immune signaling. Moreover, Adeno-associated virus (AAV)-mediated pulmonary restoration of IPO4 significantly alleviated viral pneumonia in mice. These results indicate that the CEBPB-IPO4-FASN-MAVS axis preserves innate immune homeostasis to avoid inflammatory pathology, highlighting IPO4 as a potential therapeutic target for severe viral pneumonia.
Influenza A virus (IAV) infection leads to a wide spectrum of outcomes, from asymptomatic cases to severe disease, emphasizing the pivotal role of the host immune response in determining disease severity. NRF2, a key transcription factor that governs the cellular antioxidant (AOX) response, is critical in maintaining redox balance during viral infections. Disruption of NRF2 activity can lead to accumulation of reactive oxygen species (ROS) and insufficient AOX defenses, a characteristic of influenza pathogenesis. Type I interferons (T1 IFNs) are well-established host factors implicated in antiviral immunity as well as influenza severity. We hypothesize that elevated T1 IFNs may exacerbate disease severity in response to influenza infection by altering cellular redox balance through suppression of the NRF2-driven AOX responses.
To test this hypothesis, we infected WT and Ifnar1-/- mice with influenza A virus and sorted alveolar macrophages (AMs), inflammatory monocytes (IM), and neutrophils (PMNs) at D3 post infection for assessment of the NRF2-regulated AOX response.
Influenza-infected mice showed increased transcription of NRF2-regulated AOX genes in AMs and PMNs from Ifnar-/- mice compared to WT mice, with the most dramatic effects observed within neutrophils. However, acute stimulation of purified neutrophils directly with T1 IFNs or T3 IFNs (IFN-lambda) increased rather than decreased the expression of NRF2-dependent AOXs.
These observations suggest that autocrine T1 IFNs produced in response to influenza infection profoundly alter neutrophil redox balance in vivo but this effect may be indirect or subject to differential kinetic regulation. Furthermore, manipulating the T1 IFN-NRF2-AOX axis could represent an approach for intervening in influenza-induced acute lung injury, such as acute respiratory disease syndrome.
NIH R21 HD112848-01
Viral Immunology (VIR)
Syamily Shaji, Wendy T. Watford· Journal of Immunology· 0 citations
Classically, anti-viral defenses are thought to be driven by the production of pro-inflammatory cytokines and type I interferons (IFNs) triggered by the activation of innate immune sensing pathways such as the DNA sensing pathway cGAS-STING. There are also cell autonomous defense mechanisms, such as xenophagy, that are equally important for restricting viral infections, but these are poorly understood. In this study, we examined a potential role of the E3 ubiquitin ligase RNF11 in regulating cGAS-STING signaling and anti-viral host defense in macrophages.
We utilized macrophage cell lines including THP-1 and RAW 264.7 to examine the role of RNF11 in cGAS-STING signaling and viral infections in macrophages. Lentiviral vectors expressing control scrambled or RNF11 shRNA were used to knockdown RNF11. We performed western blotting, Incucyte live-cell imaging, qRT-PCR, ELISA, flow cytometry, and confocal microscopy to examine potential roles of RNF11 in cGAS-STING signaling and innate anti-viral responses in macrophages.
Knockdown (KD) of RNF11 elicited more robust activation of the cGAS-STING pathway in response to cGAS and STING agonists and increased type I IFN production in macrophages. Unexpectedly, despite more cGAS-STING activation, there was increased replication of a DNA virus (herpes simplex virus 1 [HSV-1]). Similar results were obtained with a panel of RNA viruses including Sendai virus (SeV) and vesicular stomatitis virus (VSV) and this phenotype was specific to macrophages. Remarkably, the increased viral loads in RNF11 KD macrophages persisted with a blocking antibody specific for interferon alpha/beta receptor 1 (IFNAR1) interferon, suggesting that the anti-viral function of RNF11 is independent of type I IFN signaling.
Overall, our results suggest that RNF11 is an essential component of a novel type I interferon-independent form of cell autonomous defense that is critical for restricting viral infection in macrophages.
NIH-NIAD
Viral Immunology (VIR)
John Tawil, Morgan Steele, Jesse White et al.· Journal of Immunology· 0 citations
Melanoma differentiation-associated protein 5 (MDA5), encoded by IFIH1, is a cytosolic double-stranded RNA (dsRNA) sensor. Mutation of IFIH1 resulting in MDA5 deficiency causes immune dysfunction and predisposition to specific respiratory viral pathogens due to the inability of innate immune system to detect viral dsRNA. Additionally, gene variants in IFIH1 have been linked to autoimmunity, including type 1 diabetes. To understand structure-function, we integrate structural biology and signaling principles to explain how MDA5 architecture governs interactions with dsRNA and type 1 interferon (T1-IFN) outputs. MDA5 binds dsRNA via its helicase core and C-terminal domain, uses ATP-dependent conformational cycling to assemble filaments, and exposes N-terminal CARDs that nucleate mitochondrial antiviral signaling protein polymerization, activating TBK1/IKKε-IRF and NF-κB programs that amplify T1-IFN production and inflammatory gene expression. Risk-associated IFIH1 alleles are predicted to increase T1-IFN production/activation thresholds, whereas rare loss-of-function variants attenuate T1-IFN outputs and confer protection. Finally, we outline therapeutic entry points that preserve antiviral defense while constraining chronic T1-IFN signaling to restrain MHC class I expression, chemokine production, and autoreactive T-cell recruitment. Targeting downstream pathways with small molecule inhibitors may delay early autoimmunity and target tissue functions in genetically defined subgroups.
Opeoluwa Iwaloye, Clayton E. Mathews, Danmeng Li· Journal of Interferon and Cy...· 0 citations
