Search Results (292)

Interferon-stimulated genes (ISGs) are classically recognized for their direct antiviral functions, such as viral genome degradation or replication blockade. However, emerging evidence reveals that ISGs orchestrate a broader landscape of host defense by rewiring cellular metabolism. These mechanisms are still not fully understood in the context of antiviral immunity. This review synthesizes recent advances in understanding how ISGs modulate metabolic pathways (e.g., glycolysis, lipid metabolism, amino acids, and nucleotide metabolism) to create an antiviral cellular environment. However, viruses have developed strategies to evade or counteract ISG-encoded proteins, and some even hijack certain ISGs to their advantage. Therefore, we further explore how viruses subvert these ISG-driven metabolic to evade host defenses. Overall, we summarize the current state of knowledge on the interactions between viruses and ISGs and propose that ISGs act as “protective” or “pathogenic” regulators at the dimensions of metabolism, offering new perspectives for targeting host-centered pathways to combat viral infections. Full article

Interferon-stimulated gene 15 (ISG15) is an interferon-induced ubiquitin-like protein that plays an important role in antiviral defense and inflammatory responses, primarily through the process of ISGylation, whereby ISG15 is covalently conjugated to target proteins. Beyond its intracellular functions, a portion of free unconjugated ISG15 is also released into the extracellular environment during infections and diseases such as cancer. Extracellular ISG15 is known to regulate immune cell activity and cytokine production. Despite its immune-modulatory role, how ISG15 is released from cells has remained unclear. In this study, we have identified a non-lytic mechanism by which human macrophages release ISG15. Using lipopolysaccharide (LPS) as a stimulus, we show that extracellular LPS triggers unconjugated ISG15 release by utilizing plasma membrane-localized Gasdermin D (GSDMD) pores. Mechanistically, LPS via the autocrine/paracrine action of type-I interferon (IFN) activates caspase-4 (Casp4) to cleave the N-terminal domain of GSDMD for the formation of cell surface GSDMD pores that permit the extracellular release of unconjugated ISG15 in the absence of lytic cell death. Together, our studies have identified the IFN-Casp4-GSDMD axis as a previously unrecognized non-classical pathway for unconjugated ISG15 release from cells. Full article

This study evaluated the protective effects of naringin (NG) against intestinal injury in 7-day-old piglets infected with porcine epidemic diarrhea virus (PEDV). Eighteen piglets (Duroc × Landrace × Large, body weight = 2.58 ± 0.05 kg) were divided into three treatment groups based on similar body weights and equal numbers of males and females: the blank control group (CON group), the PEDV infection group (PEDV group), and the NG intervention + PEDV infection group (NG + PEDV group) (n = 6 per group). The experiment lasted for 11 days, comprising a pre-feeding period from days 0 to 3 and a formal experimental period from days 4 to 10. On days 4–10 of the experiment, piglets in the NG + PEDV group were orally administered NG (10 mg/kg). On Day 8 of the experiment, piglets in the PEDV and NG + PEDV groups were inoculated with PEDV (3 mL, 10⁶ 50% tissue culture infective dose (TCID₅₀) per milliliter). On day 11 of the experiment, piglets were euthanized for sample collection. PEDV infection caused significant intestinal damage, including a decreased (p < 0.05) villus height in the duodenum and ileum and an increased (p < 0.05) crypt depth in all intestinal segments. This intestinal damage was accompanied by an impaired absorptive function, as indicated by reduced (p < 0.05) serum D-xylose. Further results showed that PEDV compromised the intestinal antioxidant capacity by decreasing (p < 0.05) glutathione peroxidase and catalase activities, and it stimulated the intestinal inflammatory response by upregulating (p < 0.05) the expression of key inflammatory genes, including regenerating family member 3 gamma (REG3G; duodenum, jejunum, colon), S100 calcium binding protein A9 (S100A9; ileum, colon), interleukin 1 beta (IL-1β; ileum, colon), and S100 calcium binding protein A8 (S100A8; colon). PEDV also suppressed the intestinal lipid metabolism pathway by downregulating (p < 0.05) the ileal expression of Solute Carrier Family 27 Member 4 (SLC27A4), Microsomal Triglyceride Transfer Protein (MTTP), Apolipoprotein A4 (APOA4), Apolipoprotein C3 (APOC3), Diacylglycerol O-Acyltransferase 1 (DGAT1), and Cytochrome P450 Family 2 Subfamily J Member 34 (CYP2J34). Moreover, PEDV suppressed the intestinal antiviral ability by downregulating (p < 0.05) interferon (IFN) signaling pathway genes, including MX dynamin like GTPase 1 (MX1) and ISG15 ubiquitin like modifier (ISG15) in the duodenum; weakened intestinal water and ion transport by downregulating (p < 0.05) aquaporin 10 (AQP10) and potassium inwardly rectifying channel subfamily J member 13 (KCNJ13) in the duodenum, aquaporin 7 (AQP7) and transient receptor potential cation channel subfamily V member 6 (TRPV6) in the ileum, and TRPV6 and transient receptor potential cation channel subfamily M member 6 (TRPM6) in the colon; and inhibited intestinal digestive and absorptive function by downregulating (p < 0.05) phosphoenolpyruvate carboxykinase 1 (PCK1) in the duodenum and sucrase-isomaltase (SI) in the ileum. Notably, NG effectively counteracted these detrimental effects. Moreover, NG activated the IFN signaling pathway in the jejunum and suppressed PEDV replication in the colon. In conclusion, NG alleviates PEDV-induced intestinal injury by enhancing the antioxidant capacity, suppressing inflammation, normalizing the expression of metabolic and transport genes, and improving the antiviral ability. Full article

Background/Objectives: The enhancement of antitumor immune responses by radiotherapy (RT) is partially attributed to the activation of the IFN-type-I pathway. However, the loss of HLA-class-I molecules, which occurs in a large percentage of non-small-cell lung cancers (NSCLCs), may block the cytotoxic effect of T-cells and immunotherapy (IO). Moreover, autophagy is also involved in HLA downregulation. We investigated the complex interactions between RT, HLA molecules, autophagy, and IFN-type-I responses. Methods: The A549, H1299, and ATG7-deficient NSCLC cell lines, along with the modified shLC3A H1299 cell line, were used for in vitro experiments. The effect of RT (8 and 3 × 8 Gy) on Interferon beta (IFNβ), IFN-stimulated genes (ISGs), and HLA-class-I expression in combination with IFN-type-I-response inhibitors (Ruxolitinib, Tofacitinib, Amlexanox) targeting the JAK and TBK1 was studied with Flow cytometry and RT-PCR. Results: RT significantly induced HLA-class-I expression. A parallel upregulation of IFNβ and ISGs mRNA levels was also documented. Although the IFN-type-I-response inhibitors suppressed the RT-induced IFNβ and ISGs expression, their effect on HLA-class-I expression was minimal. Blockage of LC3A autophagy (shLC3A cell line) significantly upregulated HLA-class-I basal levels, and RT further enhanced HLA expression. IFN-type-I-response inhibitors blocked the RT-inductive effect in the shLC3A H1299, but had no effect in the ATG7-deficient H1650 cell line. Conclusions: The current study supports the theory that baseline autophagy, RT-induced autophagy blockage, and IFN-type-I response enhancement define the HLA-class-I levels in NSCLC cells. This complex interplay emerges as a promising target for the development of radio-vaccination strategies to enhance the efficacy of radio-immunotherapy. Full article

Porcine circovirus type 2 (PCV2), a widely distributed immunosuppressive virus, causes substantial economic losses in the global swine industry. C1QTNF6 has emerged as a novel immunoregulatory factor attracting increasing research interest due to its dual roles in both pro-inflammatory and antiviral immune responses. However, the role of C1QTNF6 in regulating PCV2 replication remains poorly characterized. Here, we analyzed C1QTNF6 expression patterns and identified its highly specific expression in placental tissues in both humans and pigs. We then overexpressed C1QTNF6 and conducted RNA sequencing analysis. Remarkably, 68 upregulated genes were identified, and most of them were interferon-stimulated genes (ISGs), including MX2 and ISG15. Functional enrichment analysis revealed that these genes were primarily associated with defense response to viruses and antiviral innate immune response. Subsequently, experimental data show that PCV2 infection significantly suppressed inflammatory responses and markedly downregulated the expression of C1qtnf6, MX2, and IFIT2. Moreover, experimental data indicated that C1QTNF6 inhibits PCV2 replication by targeting ISGs, while restoring MX2 expression. To verify whether C1QTNF6-MX2 antiviral axis mediates this antiviral effect, we constructed an MX2 overexpression plasmid and demonstrated that MX2 overexpression indeed significantly suppressed PCV2 replication. Together, these results provide important insights into PCV2-host interactions and the development of novel antiviral strategies. Full article

Background and Objectives: Type I interferon (IFN-I) transcriptional signatures are widely utilised as readouts of innate immunity. We evaluated whether age and sex affect single interferon-stimulated genes (ISGs) and the composite IFN-I score, with implications for control selection and assay calibration. Materials and Methods: Ninety-five healthy individuals (53 males, 42 females; 18 days to 89 years) were studied. Whole-blood expressions of IFI27, IFI44L, IFIT1, ISG15, RSAD2 and SIGLEC1 was quantified by RT-qPCR, normalised to GAPDH and calibrated to a paediatric reference. Age associations used Spearman’s rho; sex differences, two-sided Mann–Whitney U tests. Results: Age effects were modest and gene-specific: IFI44L declined and IFI27 increased with age (significant overall and in females), whereas in males only IFI44L decreased; other ISGs were null (|r| ≤ 0.36). The composite IFN-I score showed no association with age or sex, indicating that aggregation mitigates small gene-level variation and that demographic influences on baseline IFN-I readouts appear minimal within this six-gene whole-blood qPCR panel in our cohort. Conclusions: Methodologically, a single primary cut-off within homogeneous pipelines is appropriate. Although best practice favours age-, sex- and matrix-matched healthy controls, our data show no significant age- or sex-related differences in the composite IFN-I score; matching therefore primarily supports comparability and clinical governance rather than correction of demographic shifts. Full article

Interferon-stimulated genes (ISGs) were initially discovered for their role in antiviral functions. However, recent studies show evidence of a diverse and context-specific regulatory function of these genes in antiviral and antibacterial protection. The molecular mechanisms of such activities vary depending on the pathogen, cell type, isoform, and species. In this review, we summarize the context-specific functions of several prominent and well-known ISG families, including OAS, IFITs, ISG15, viperin, ADAR1, and Mx proteins. We provide examples of distinct enzymatic or regulatory mechanisms that are employed by these ISGs to carry out their diverse functions, including nucleic acid sensing, RNA degradation, translation inhibition, membrane remodeling, etc. Full article

(1) Background: Hepatitis B virus (HBV) belongs to the Hepadnaviridae family of viruses that interact with hepatocytes. HBV infection is a major global health problem. Most adults clear the infection quickly after being infected with HBV, while a few people develop chronic HBV infection. It is well-known that the early innate immune response of host cells plays an important role in the fight against virus infection. However, the interactions between HBV and the intrinsic innate immune system of hepatocytes are still not fully understood. The aim of this study was to confirm the interaction between HBV and hepatocytes, and to identify the interferon-stimulated genes (ISGs) regulated by HBx and their expression in association with HBV-associated HCC (HBV-HCC), so that we can refine our understanding of the interaction between HBV and ISGs and its potential influence on HBV-HCC. (2) Methods: We analyzed data concerning the stimulation of IFN-dependent genes in primary human hepatocytes (PHHs) transfected with pathogen DNA mimetics or infected with HBV in the GSE69590 database. Bioinformatic methods, such as GSEA, GO, and KEGG, were used to analyze the differentially expressed innate immunity genes and their related pathways to identify candidate intrinsic innate immune factors. qPCR on HepG2 and Huh7 cells, which highly express HBx, was used to detect relevant intrinsic innate immune factors. qPCR, RNAi, and Elisa methods were used to identify intrinsic innate immune factors in HBV-integrated HepG2.2.15 cells, and bioinformatics analysis was conducted on the HBV-infected tissues and cells in the GEO database. (3) Results: Inhibition of the JAK-STAT pathway enhanced HBV replication in HepG2 cells transfected with HBV plasmid and HepG2-NTCP cells infected with HBV. GSEA analysis of the GSE69590 data revealed significant changes in intrinsic innate immune pathways during HBV infection with PHH for 40 h. A total of 84 differentially expressed, candidate innate immunity genes were identified in GSE69590. Validation showed that TRIM22 and TRIM56 were down-regulated when HBx was expressed. Consistently, TRIM22 and TRIM56 were up-regulated following inhibition of HBx by transfection of HBx siRNA into HepG2.2.15 cells, and HBV pgRNA was up-regulated following down-regulated expression of TRIM22 and TRIM56 in HEK293 cells. Receiver operating characteristics (ROC) and overall survival (OS) analysis of 204 HBV-HCC patients showed that expression of TRIM22 was closely associated with HBV-HCC, and high expression of TRIM22 was associated with longer survival. (4) Conclusions: Innate immunity genes TRIM22 and TRIM56 are regulated by HBx, and higher expression of TRIM22 is closely related to longer survival of HBV-HCC patients. Full article

Viral infections in humans and animals are increasing, and retrospective studies using formalin-fixed, paraffin-embedded (FFPE) samples reveal recurring outbreaks over past decades. However, the impact of pre-analytical factors like fixation and autolysis on immunohistochemistry (IHC) remains insufficiently understood. To examine how autolysis, fixation duration (6–72 h) and formalin concentration (2.5–25%) influence histology and IHC of canine distemper virus (CDV, Morbillivirus canis), interferon-β (IFN-β), and selected IFN-stimulated genes (ISGs), the study was conducted using an in vitro model based on persistently CDV-infected and non-infected DH82 cells (canine histiocytic sarcoma cell line). Autolysis led to a progressive loss of cell morphology, whereas formalin fixation had minimal impact. CDV nucleoprotein, ISG15, and myxovirus resistance protein (Mx) showed stable immunohistochemical signals across all fixation conditions and remained detectable after prolonged autolysis. CDV infection upregulated ISG15 and Mx. In contrast, IFN-β and phosphorylated protein kinase R (pPKR) exhibited variable staining and did not distinguish infected from non-infected samples. Overall, autolysis had a stronger negative impact on IHC signal quality than fixation parameters. Despite the limitations of the in vitro model, the robustness of CDV, ISG15, and Mx under suboptimal conditions highlights their potential utility as virus-sensing markers in FFPE material. Full article

Viruses, like influenza and Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remain major causes of upper respiratory tract infections worldwide, with symptoms ranging from asymptomatic to lethal outcomes. While antivirals and vaccines have helped ameliorate disease morbidity and mortality, these infections still pose significant challenges. Probiotics, including Lactococcus lactis strain plasma (LC-Plasma), have recently shown antiviral effects by activating plasmacytoid dendritic cells (pDCs), though their detailed mechanism remains unclear. In this study, we stimulated peripheral blood mononuclear cells (PBMCs) collected from healthy participants with LC-Plasma and conducted immunological analyses to investigate the immunomodulatory mechanisms of LC-Plasma. The supernatant derived from LC-Plasma-stimulated PBMCs (LCP Sup) exhibited dose-dependent inhibition of replication in Influenza A virus subtype H1N1 (H1N1) and SARS-CoV-2. LCP Sup significantly reduced the SARS-CoV-2 viral load in Huh-7 cells. However, in the H1N1 antiviral assay using A549 cells, LCP Sup was required at a higher concentration against H1N1 in A549 cells compared with SARS-CoV-2 in Huh-7 cells. Treatment with LCP Sup significantly upregulated interferon-stimulated genes (ISG) expression, particularly MxA, in A549 cells. While MxA showed the most notable increase, other ISGs also exhibited elevated expression levels compared with the negative control. Other cytokines, chemokines, and growth factors were also induced by LC-Plasma and CpG-DNA stimulation, and the effects of LC-Plasma were much higher than those of CpG-DNA. These results provide in vitro evidence of the antiviral mechanisms of LC-Plasma via upregulation of interferon-α (IFN-α) and related ISGs for host defense against respiratory viruses. Full article

Previous studies have reported that Enterovirus A71 (EV-A71) infection could activate STING-related signaling pathways in vitro, but the role of STING in EV-A71 infection in vivo and the associated immune regulatory mechanisms remain unclear. Here, we used the STING-specific agonist diABZI to activate STING and STING-knockout mice to jointly study the role and mechanism of regulating STING on EV-A71 infection in vivo. The results showed that activating STING could inhibit the in vivo replication of EV-A71, alleviate clinical symptoms in infected mice, and increase the survival rate. Conversely, STING knockout significantly promoted viral replication in vivo and increased the lethality and severity of EV-A71 infection. Mechanistic studies further revealed that STING activation exerts its antiviral effects by stimulating interferon signaling pathways, upregulating the expression of interferon-stimulated genes (ISGs). Additionally, STING activation also modulated the serum cytokine response profile. Moreover, STING activation drove the expansion of diverse immune cell populations, including T cells, natural killer (NK) cells and myeloid cells. In contrast, STING knockout not only reduced the proportion of thymic T cells and impeded T cell developmental progression from double-positive (DP) to single-positive (SP) stages, but also impaired the effector functions of CD8+ T cells and NK cells during viral infection. In summary, this study demonstrates that STING activation effectively suppresses EV-A71 replication and mitigates infection symptoms by modulating immune and inflammatory responses. These findings provide a foundational framework for understanding how STING coordinates antiviral immunity and inform future investigations into STING-targeted therapies for viral infections. Full article

BK polyomavirus (BKPyV) causes severe urinary tract diseases, including BKPyV-associated nephropathy (BKPyVN) and ureteric stenosis, in immunocompromised individuals such as renal transplant recipients. Effective antiviral therapies for BKPyV infection remain an unmet clinical need. While the interferon-stimulated gene 20 (ISG20) exhibits broad-spectrum antiviral activity against RNA viruses, its role and mechanisms against DNA viruses are poorly defined. This study demonstrates, for the first time, potent antiviral activity of ISG20 against BKPyV. This restriction was observed with both endogenous levels of ISG20 and upon overexpression, and this effect was confirmed by ISG20 knockout and immunofluorescence imaging. We observed that ISG20 expression is dynamically regulated during BKPyV infection: it is upregulated both during early infection and by expression of the viral large T antigen (LT) alone. However, endogenous ISG20 expression becomes significantly suppressed during later stages of infection, coinciding with declining LT levels. The physical interaction between LT and both wild-type and mutant ISG20 suggests a potential viral strategy to sequester this restriction factor. These findings establish ISG20 as a novel host restriction factor against BKPyV and suggest that BKPyV employs LT-mediated mechanisms to evade or counteract ISG20’s antiviral effects. Our results elucidate a complex biphasic interplay between BKPyV and host innate immunity, identifying ISG20 as a potential therapeutic target for BKPyV-associated diseases. Full article

Human immunodeficiency virus (HIV) remains a global public health challenge. Antiretroviral therapy (ART) improves outcomes by suppressing viral replication and enabling immune recovery, yet the early molecular mechanisms of immune-related transcriptional change after ART remain insufficiently characterized. We enrolled eight ART-naïve male patients with HIV aged 18–35. Peripheral blood mononuclear cells (PBMCs) were collected before and after 24 weeks of combination ART (TDF, 3TC, DTG) and underwent bulk RNA-seq (Illumina HiSeq 1500, Illumina, Inc., San Diego, CA, USA). Differential expression was assessed with DESeq2 (paired design); gene set enrichment analysis (GSEA), principal component analysis (PCA), hierarchical clustering, and protein–protein interaction (PPI) networks (STRING/NetworkX) explored functional patterns and transcriptomic shifts. We identified 87 differentially expressed genes, including 67 downregulated interferon-stimulated genes (e.g., IFI44L, ISG15, STAT1) and 20 upregulated transcripts, mostly pseudogenes related to ribosomal proteins. Functional enrichment revealed suppression of type I interferon and other antiviral signaling pathways. PCA and hierarchical clustering indicated a post-ART transcriptional shift. These findings suggest that early immune recovery following ART involves downregulation of chronic interferon-driven activation. This observation may correspond to partial restoration of T-cell functional capacity, reduced immune exhaustion, and a rebalanced antiviral immune environment. Full article

Innate immunity is the body’s first line of defense for mounting robust antiviral signaling. However, the role of cytoskeletal prestress, a hallmark of cellular mechanotransduction, in regulating innate immune pathways such as retinoic acid-inducible gene I (RIG-I) signaling remains poorly understood. Herein, we show that cells on soft vs. rigid substrates elicit cytoskeletal prestress-dependent activation of RIG-I signaling, leading to differential type-I interferon (IFN) gene expression. Cells were cultured on soft (0.6 kPa) and stiff (8.5 kPa) substrates to modulate cellular traction and prestress, followed by transfection of Poly(I:C), a synthetic viral dsRNA mimic, to measure the RIG-I-mediated innate immune response. Cells on soft substrates show minimal activation of RIG-I signaling, resulting in low expression of IFN-β1 and other IFN-stimulated genes (ISGs), compared to cells on stiff substrates. We further demonstrate that activation of TANK Binding Kinase 1 (TBK1), a downstream effector of the RIG-I pathway, is inhibited in cells on soft substrates due to the cytoplasmic sequestration of the Yes-associated protein (YAP), a HIPPO pathway effector protein. In contrast, cells on stiffer substrates experienced decreased TBK1 inhibition due to the nuclear localization of YAP and exhibited elevated TBK1 activation and heightened IFN and ISG expressions. Together, we demonstrate that cytoskeletal prestress represents a key biophysical regulator of innate immune signaling. Full article

The highly pathogenic avian influenza (HPAI) H5N1 virus poses a growing global health threat, particularly following its unprecedented spillover into dairy cattle and subsequent transmission to more than 1000 dairy farms in 18 states. This study investigates the host cell responses to distinct H5N1 strains (bovine- and mink-derived H5N1) in the presence and absence of raw milk across diverse mammalian cell lines (MDCK, MDBK, A549, Vero, MV1). Our findings reveal that the bovine-derived H5N1 strain exhibits more robust replication than the mink-derived H5N1 and demonstrates intra-host viral evolution with emerging amino acid substitutions detectable by deep sequencing. Although raw milk supplementation did not directly enhance viral replication in vitro, it significantly modulated host gene expression, often dampening key antiviral interferon-stimulated gene (ISG) responses and disrupting essential host cellular processes like intracellular trafficking and sialic acid biosynthesis. These host gene modulations are cell-type- and strain-specific, suggesting a complex interplay that may theoretically influence virus–host dynamics, though the biological significance of these in vitro observations requires validation through infectious virus assays and in vivo studies. This hypothesis-generating work provides preliminary insights into H5N1-milk interactions, highlighting the need for further mechanistic investigation to assess potential implications for viral transmission in dairy environments. Full article