Bioactive peptides derived from amphibian skin have attracted increasing attention due to their potent biological activities and potential toxicological and pharmacological relevance. Amphibians, particularly frogs (order Anura), possess highly specialized skin glands that secrete diverse peptides functioning in chemical defense and innate immunity. Owing to their broad-spectrum antimicrobial, antiviral, anticancer, antioxidant, and immunomodulatory properties, these peptides are regarded as promising candidates for drug development, while their biological activities also raise important considerations regarding safety and toxicity. This review focuses on skin-derived peptides in Amphibia, with an emphasis on frog peptides, reflecting their dominance in species diversity and available research data. We first summarize the diversity of amphibian skin structures and peptide-secreting glands, and then present a bibliometric analysis of frog peptide-related publications over the past two decades, identifying antimicrobial and antiviral peptides as major research hotspots. Subsequently, amphibian skin peptides are systematically categorized according to their biological functions, including antimicrobial, antioxidant, wound-healing, anticancer, immunomodulatory, and antiviral activities. By integrating structural, functional, and bibliometric perspectives, this review provides a consolidated framework for understanding the biological significance and application potential of amphibian skin peptides, thereby offering a reference for future toxicological evaluation and translational research.
Porcine epidemic diarrhea virus (PEDV) is a highly contagious enteric coronavirus that causes lethal diarrhea in neonatal piglets, yet the viral pathogen-associated molecular patterns (PAMPs) that initiate mucosal antiviral immunity remain poorly defined. Here, integrating intestinal single-cell transcriptomics with in vivo and in vitro infection models, we delineate how PEDV is sensed by host innate immunity. We found that RIG-I, rather than MDA5, functions as the dominant cytosolic sensor that detects PEDV and initiates interferon-mediated antiviral defense in the intestinal mucosa. RIP-seq and RNA structural analyses identified nucleotides 375-760 within the 5' ORF1a region of the PEDV genome as a core RNA PAMP directly engaged by RIG-I. Molecular docking and mutational analyses further revealed that specific nucleotide motifs and cooperative stem-loop assemblies are required for optimal RIG-I activation, establishing higher-order RNA architecture as a key determinant of PAMP potency. Functionally, this PEDV-derived RNA PAMP robustly activated RIG-I signaling, amplified interferon and ISG responses, and restricted replication of PEDV and multiple heterologous RNA viruses, demonstrating broad-spectrum activity against several enteric and respiratory RNA viruses. Moreover, co-administration of this viral RNA with an inactivated influenza vaccine significantly enhanced antigen-specific immunity and protection. Together, these findings define the molecular basis of RIG-I-mediated recognition of PEDV, identify a structurally encoded viral PAMP with both antiviral and adjuvant properties, and provide new insights into how coronaviruses are sensed and controlled at mucosal surfaces.IMPORTANCEPorcine epidemic diarrhea virus (PEDV) causes devastating enteric disease in newborn piglets, yet how the intestinal mucosa detects this coronavirus and mounts antiviral immunity has remained unclear. Our study identifies RIG-I as the dominant epithelial sensor responsible for detecting PEDV and initiating interferon-driven antiviral defense. We further define a structurally encoded RNA element within the 5' ORF1a region of the PEDV genome that functions as a core viral PAMP directly activating RIG-I. This RNA element acts as a molecular alarm that triggers robust innate immune responses, restricts infection by PEDV and other RNA viruses, and enhances the protective efficacy of an inactivated influenza vaccine. These findings illuminate fundamental mechanisms of coronavirus sensing at mucosal surfaces and highlight viral RNA structures as promising natural immunostimulants for antiviral and vaccine strategies.
p300 is an acetyltransferase that regulates gene expression by acetylating histones and transactivating some transcription factors such as nuclear Factor Kappa B (NF-κB) and interferon regulatory factor 3 (IRF3). p53 is an interferon (IFN)-inducible tumor suppressor that enhances antiviral responses. How p300 and p53 precisely regulate innate antiviral immunity remains incompletely understood. Herein, we report that conditional p300 knockout in alveolar epithelial cells does not suppress but rather enhances antiviral responses in mice infected with vesicular stomatitis virus (VSV) and herpes simplex virus (HSV-1). In vitro investigation reveals that A-485, a p300-specific inhibitor, and p300 knockdown suppress virus replication but promote IFN-β production in a variety of cell types by enhancing (TANK-binding kinase 1) TBK1 and IRF3 phosphorylation. p300 binds TBK1 and acetylates two lysine residues at 241 and 692 to block its activation. p300 expression is downregulated by viral infection in a p53-dependent manner. Mechanistically, viral infection increases the levels of p53, which leads to the upregulation of the seven in absentia homolog 1 (SIAH1) E3 ubiquitin ligase. SIAH1 induces p300 K48-linked polyubiquitination and subsequent proteasomal degradation. Consistently, p53 knockout inhibits, whereas SIAH overexpression enhances antiviral responses. Taken together, our study identifies p300 as an acetyltransferase that suppresses innate immunity by acetylating TBK1, and demonstrates that the p53-SIAH1 axis downregulates p300 to sustain antiviral responses.
Interferon regulatory factor 9 (IRF9) is a key antiviral gene regulation during innate immune activation in groupers. In this study, we unpack how thermal stress reshapes the antiviral machinery driven by giant grouper IRF9 (ggIRF9) under nervous necrosis virus (NNV) challenge. In vivo, ggIRF9 mRNA levels surged 2- to 12-fold above baseline in a tissue-specific manner following LPS and poly(I:C) stimulation, and NNV infection drove a roughly 2-fold expression spike as early as 3 hours post-infection. The overexpression of ggIRF9 dramatically amplified the promoter activity of two frontline antiviral genes, e.g. Mx1 and PKR, reaching peak inductions of ∼25- and ∼30-fold over mock-treated controls, respectively. Additionally, the DNA-binding domain of ggIRF9 appears to physically engage the interferon-sensitive response element within the Mx1 promoter, providing a direct mechanistic link between IRF9 occupancy and Mx1 transcriptional output. Moreover, ggIRF9 expression proved highly vulnerable to thermal perturbation. Hypothermic conditions induced a consistent ∼0.6-fold suppression of ggIRF9, while hyperthermic stress triggered a more complex, context-dependent modulatory pattern. In vitro, both cold and heat stress significantly inhibited ggIRF9 promoter activity. Cold likely acting through heat shock factor 1a (HSF1a) and heat through HSF1b, converging on the same outcome that a weakened antiviral transcriptional program. In short, these findings position ggIRF9 as an essential factor of innate antiviral immunity in giant groupers, and reveal that thermally compromised IRF9 function translates directly into diminished host defense, a finding with pressing relevance given the climate-driven escalating thermal volatility of aquaculture environments.
Sudan virus (SUDV; species Orthoebolavirus sudanense) remains a major public health threat, yet research is limited by restricted access to biosafety level 4 (BSL-4) facilities. To address this, we developed a biologically contained SUDV lacking the essential VP30 gene, restricting replication to VP30-expressing cells. We demonstrate efficient virus rescue, strict functional and genetic containment, and replication kinetics comparable to wild-type SUDV in permissive cells. Using heterologous VP30-expressing cell lines, we observe strong cross-functionality among orthoebolaviruses, whereas Marburg virus VP30 shows minimal activity, highlighting genus-specific constraints. The system supports high-throughput antiviral screening and confirms robust activity of remdesivir. In addition, resistance profiling identified substitutions at residue F549 of viral polymerase L as key determinants for remdesivir resistance, with additional mutations at M675. Together, this biologically contained SUDV system enables safe study of viral replication, antiviral discovery, and resistance evolution under lower biosafety conditions.
Influenza A virus (IAV) is a global health concern, increasing the exploration of alternative therapeutics. Biosurfactants (BSs) are biodegradable, non-toxic biomolecules with favorable biological activities. Acinetobacter junii B6, known for utilizing crude oil as a carbon and energy source, produces BSs. This study evaluated the antiviral potential of the lipopeptide biosurfactant (LPB) against H1N1/A/PR8/34 infection. A. junii B6 LPB was extracted and characterized in our previous study. The 50% cytotoxic concentration and non-cytotoxic concentration (NCTC), defined as the concentration with no toxicity on cells, were determined by the MTT assay on MDCK cells. The NCTC was exposed to the cells in the presence of PR8 (100 TCID50) under simultaneous, pre- and post-exposure combination treatments for 1 h. After 48 h of incubation, the hemagglutination and MTT assays assessed viral propagation and cell protection, respectively. Amantadine and oseltamivir served as antiviral control drugs. The extracted LPB caused a 1 log2 reduction in pre- and post-exposure treatments, whereas amantadine and oseltamivir reduced viral titers by more than 1 log2. Cell protection was favorable in all combination treatments except for LPB co-treatment. LPB extract showed limited but notable anti-IAV activity, alongside cell protection. While LPB is less potent than amantadine and oseltamivir, its non-toxic and environmentally friendly nature warrants further study. As surfactants act on the lipid envelope, viral proteins, and nucleocapsid proteins, LPB could be potentially used as an adjuvant with other antiviral agents to control the prevalence of viral diseases and improve therapeutic outcomes.
Long noncoding RNAs (lncRNAs) are increasingly recognized as a source of functional peptides involved in plant development and immunity, yet little is known about whether lncRNA-encoded peptides participate in antiviral defence. By transcriptome analysis with peptide-coding potential prediction, we identify lncRNA19864, which is highly expressed in wheat yellow mosaic virus (WYMV)-resistant cultivars and encodes a 39-amino-acid peptide, TaLEP1. Genetic manipulation of TaLEP1 expression showed that TaLEP1 as a positive regulator of wheat resistance to WYMV. Mechanistically, TaLEP1 forms oligomers and interacts with both the host autophagy factor TaATG18a and the viral replicase NIb, thereby facilitating NIb recruitment to autophagosomes for degradation. Disruption of TaLEP1 oligomerization or TaATG18a function impaired NIb degradation and compromised TaLEP1-mediated antiviral resistance. Notably, TaLEP1 also confers resistance to other Potyviridae members, including Turnip mosaic virus (TuMV) and Soybean mosaic virus (SMV), by similarly targeting their NIb proteins for degradation. Accordingly, lncRNA-encoded peptide is involved in plant antiviral immunity. Our results offer a potential strategy for engineering broad-spectrum virus resistance in crops.
Type III interferons (IFN-λ) are critical components of the interferon system, serving as key antiviral cytokines in the innate immune response of epithelial cells. However, the biological role of pigeon IFN-λ (piIFN-λ) remains poorly understood. In this study, we cloned and characterized the biological effects of piIFN-λ. Our results reveal that the open reading frame (ORF) of piIFN-λ is 561 base pairs long, encoding a protein consisting of 186 amino acids. The amino acid sequence of piIFN-λ shares 76.3%, 65.1%, 64%, 60.2%, and 31.2% identity with those of shearwater, chicken, duck, goose, and human IFN-λ, respectively. Notably, recombinant piIFN-λ, expressed in a prokaryotic system, exhibited dose‑dependent antiviral activity against both vesicular stomatitis virus (VSV) and H9N2 avian influenza virus (AIV). Mechanistically, luciferase reporter assays indicated that recombinant piIFN-λ activated the Mx and ISRE promoters and enhanced Mx, OAS and PKR mRNA expression in a dose‑dependent manner in DF-1 cells. These findings suggest that piIFN-λ may hold potential as a therapeutic agent for avian viral diseases.
Influenza viruses remain a significant global health threat due to their high mutation rates and extensive subtype diversity. Genetic variability promotes the mixing of viral subpopulations and facilitates the emergence of novel, potentially virulent, strains. Seasonal influenza vaccines, typically targeting the A/H1N1pdm09 subtype, A/H3N2 subtype, B/Victoria lineage, and B/Yamagata lineage must be reformulated annually, yet their effectiveness and antiviral resistance are continually challenged by antigenic drift. Notably, the H275Y mutation confers a marked reduction in sensitivity to oseltamivir. Comparative variant analysis provides an effective approach for understanding these genetic variations, which is essential for enhancing vaccine effectiveness and predicting drug resistance. Existing tools enable pairwise comparison of variant call format (VCF) files through command-line interfaces but a major limitation is that they only merge variants, and users must manually group variants across multiple samples. Here, we present ShinyVar, a web-based application developed using the R Shiny framework for comparative variant analysis. The application automatically identifies and visualizes mutations in influenza viruses (IFVs) through interactive comparison of variant profiles across subpopulations. The analysis included the A/Wisconsin/67/2022 (H1N1)pdm09-like virus, A/District of Columbia/27/2023 (H3N2)-like virus, B/Austria/1359417/2021 (B/Victoria lineage)-like virus, and B/Phuket/3073/2013 (B/Yamagata lineage)-like virus as representative subtypes for comparison across the past four years. Variant analysis revealed 181 unique variants in B/Victoria lineage 2025, 101 unique variants in A/H1N1pdm09 2024, 37 unique variants in A/H3N2 subtype 2024, and seven unique variants in B/Yamagata lineage 2025. Structural analysis focused on HA_A/H1N pdm091, NA_A/H1N1 pdm09, and NA_B/Victoria. In HA_A/H1N1pdm09, eight non-synonymous mutations were identified. For downstream structural analysis, p.Thr137Ala or p.Thr120Ala mature numbering led to the loss of a hydrogen bond within the 5J8 antibody binding site, resulting in a slight decrease in binding affinity. In the NA_B/Victoria lineage, eleven non-synonymous mutations marginally disrupted key oseltamivir interaction residues (E276 and R292), resulting in lower binding affinity compared with NA_A/H1N1pdm09. ShinyVar is a fast and efficient tool for variant detection and visualization, making it suitable for monitoring not only IFV evolution but also the evolution of other pathogens. ShinyVar facilitates the identification of novel, shared, and unique variants linked to important traits, including drug resistance and virulence under selective pressure, contributing to improved insights into pathogen evolution and the rational design of vaccines and antiviral drugs.
Functional validation of host factors in whole-animal models is a major bottleneck in virology; it hinders the translation of data from in vitro studies into a deeper understanding of the viral life cycle and pathogenesis. To address this challenge, we developed a systematic in vivo screening platform for influenza A virus. This platform comprises a library of 84 CRISPR-Cas9-generated gene-modified mouse lines targeting host factors prioritized from the literature and in vitro small interfering RNA (siRNA) screening studies. Using this resource, we identified 17 host factors whose genetic ablation conferred resistance to influenza A virus infection. Further studies of two of these factors, Arhgef28 and Lasp1, revealed distinct protective mechanisms against influenza A virus. We offer this mouse library to the research community as a powerful platform for studying virus-host interactions in a physiologically relevant context.
Respiratory syncytial virus (RSV) induces a protective immune response shaped by regulatory pathways that control T cell function. The inhibitory receptor PD-1 is a central modulator of these processes. Here, we analyzed PD-1, LAG-3, and TIM-3 expression in CD8+ T cells during RSV infection and evaluated PD-1/PD-L1 modulation across different immunological contexts in mice. PD-1 expression progressively increased in lung CD8+ T cells at 5- and 9-day post-infection, accompanied by co-expression of LAG-3 and TIM-3, and elevated PD-L1 in epithelial and antigen-presenting cells. PD-1 modulation varied with context: passive immunization reduced its expression, whereas rBCG-N-RSV vaccination followed by infection increased PD-1 and cytokine production. PD-1 blockade enhanced memory T cell generation and the quality of the humoral response, whereas PD-1 deficiency impaired these responses. These findings support a context-dependent role for PD-1 in coordinating antiviral immunity and vaccine-induced immune responses.
Achyranthis bidentatae radix (ABR, Niu-Xi in Chinese) is a well-documented medicinal herb with a long history of use in Traditional Chinese Medicine (TCM). Traditional application records suggest that ABR may be widely used for treating conditions such as amenorrhea, dysmenorrhea, waist and knee pain, muscle and bone weakness, stranguria, edema, headache, dizziness, toothache, oral aphthae, hematemesis, and epistaxis. This paper provides a comprehensive review of ABR, encompassing its botany, processing methods, ethnopharmacology, phytochemistry, pharmacology, quality control, toxicity, and pharmacokinetics. It aims to offer an overview of current research to facilitate further exploration and utilization of ABR. This study used "Achyranthis bidentatae radix", "Achyranthes bidentata Bl." and "NiuXi" as the keywords to gather relevant information on ABR from different databases, including PubMed, CNKI, Web of Science, and Google Scholar. Literature on non-medicinal parts, including stems, leaves, fruits, and seeds, was excluded. To date, 204 compounds have been isolated and identified from ABR, including triterpenoid saponins, steroids, polysaccharides, alkaloids, flavonoids, polypeptides, volatile oils, and other chemical components. Triterpenoid saponins, steroids and polysaccharides exert the main pharmacological effects, including anti-osteoporosis, anti-inflammatory, immunomodulatory and anti-tumor activities. ABR also exhibits other pharmacological activities, including nephroprotective, antioxidant, neuroprotective, anti-diabetic, hepatoprotective, antiviral, and cardioprotective effects. Toxicological studies confirm ABR's general safety at conventionally recommended dosages, while pharmacokinetic investigations have clarified the in vivo behaviors of β-ecdysterone and triterpenoid saponins from ABR. In addition, this paper addresses the shortcomings of current research on ABR and proposes potential future research directions. ABR exhibits a diverse chemical composition and a wide range of pharmacological activities. However, studies on the single active compounds of ABR remain insufficient. Research on their in vivo mechanisms of action is limited and lacks clinical trial validation, while research on the mechanisms of multi-component synergistic effects remains incomplete. Future studies should therefore focus on the identification of bioactive constituents, along with systematic pharmacological and clinical evaluation. Quality control research on ABR and its processed products must be strengthened to ensure their safe and effective application. Furthermore, in-depth investigations into the toxicology and pharmacokinetics of ABR will provide a scientific basis for its clinical application.
Anti-infective drugs have profoundly transformed the history of medicine. Yet, with the presence of approximately 4.1-5 million interindividual genomic variants in human genome, patients are expected not to respond equally to the same anti-infective drug. This genetic variability, together with nongenetic factors, influences therapeutic outcomes and contributes to drug-induced adverse events in predisposed individuals. Historically, the identification of HLA-B∗57:01 as a predictor of abacavir hypersensitivity in patients with HIV represented the first successful clinical application of pharmacogenomics (PGx) in infectious diseases. Since then, the field has continued to evolve, as evidenced by the discovery of multiple clinically relevant gene-drug pairs, primarily related to immune responses, drug metabolism, and drug transport pathways. The evidence accumulated to date has established a number of mandatory (HLA-B∗57:01-abacavir) and actionable (MT-RNR1-aminoglycosides, CYP2B6-efavirenz, G6PD-nitrofurantoin, G6PD-nalidixic acid, and G6PD-dapsone) gene-drug pairs, whereas most other associations remain informative or exploratory without current guideline-based prescribing recommendations. Despite this progress, robust PGx evidence remains predominantly focused on antiretrovirals, anti-hepatitis C virus, and selected antimicrobial drug classes, such as β-lactams, aminoglycosides, sulfonamides, and antituberculosis drugs. For many other anti-infective agents, current evidence suggests that host genetic variation may have a limited impact on drug efficacy or safety, or that existing studies remain insufficiently powered or replicated to support clinical translation. The narrow ancestral diversity in PGx studies and clinical trials has also restricted the breadth of the knowledge gained and, consequently, the development of inclusive guidelines. This review summarizes the current PGx landscape of antibacterial and antiviral drugs and highlights key challenges and opportunities to improve clinical actionability. Greater inclusion of previously underrepresented populations, coupled with integrative multiomics approaches powered by artificial intelligence and machine learning, could accelerate PGx biomarker identification, validation, and integration into personalized patient care. SIGNIFICANCE STATEMENT: Rapid and effective deployment of anti-infective drugs requires incorporating knowledge of host genetic determinants of drug effectiveness or adverse events, the latter of which is a leading cause of death. The evolution of data science, driven by available genomic data, represents an unprecedented opportunity to accelerate pharmacogenomics discovery in infectious diseases. If acquired at a population level and integrated into medical records, pharmacogenomics data can guide the prescription and/or dosing of anti-infective drugs, shifting infectious disease management toward personalized care.
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Mitochondrial GTPase ERA G-protein-like 1 (ERAL1) is considered an antiviral host factor against RNA viruses. However, its role in driving DNA virus infection, particularly hepatitis B virus (HBV) infection, and its relevance to human liver disease are unknown. This study aimed to define the function and molecular mechanism of ERAL1 in HBV pathogenesis. Complementary models, including HBV-replicating cell lines, an rAAV8-HBV hydrodynamic mouse model, and clinical samples from patients across the natural history of chronic HBV infection were employed and analyzed via coimmunoprecipitation, confocal immunofluorescence, RNA sequencing, qPCR, immunoblotting, and immunohistochemistry. ERAL1 expression was significantly suppressed in HBV patients, including an approximately 75% reduction in the livers of patients during the immune-reactive phase compared with those in healthy controls. ERAL1 overexpression resulted in notable antiviral activity, suppressed HBV replication and achieved nearly 60% HBsAg clearance in vivo. Mechanistically, ERAL1 interacts with mitochondrial adaptor MAVS, promoting its aggregation and subsequently activating the downstream Akt and MAPK signaling pathways, which are essential for its antiviral effect. ERAL1 is identified as a crucial HBV-restricting host factor and a novel mitochondria-centered defense mechanism in which ERAL1 reinforces MAVS-dependent antiviral signaling. The notable downregulation of ERAL1 in patient livers and its considerable antiviral effectiveness suggest that ERAL1 is a candidate host factor worthy of further therapeutic exploration.
Ubiquitination is a pivotal regulatory mechanism in host-virus interactions, playing essential roles in both antiviral defense and viral immune evasion, with E3 ubiquitin ligases serving as critical regulatory nodes. In this study, we systematically evaluated 26 candidate host E3 ubiquitin ligases for their involvement in influenza A virus (IAV) infection. Among these, potassium channel modulatory factor 1 (KCMF1) was identified as a novel negative regulator of IAV replication in vitro and in vivo. Mechanistically, KCMF1 interacts with the viral polymerase subunit PB1 and mediates its ubiquitination at lysine 653 (K653), triggering proteasomal degradation and consequent impairment of polymerase activity. A recombinant PR8 (H1N1) virus carrying a K653R substitution in PB1 exhibits enhanced replication and increased pathogenicity in both cells and mice. Furthermore, the inhibitory effect of KCMF1 on PR8 virus replication is dependent on the K653 residue of PB1. Importantly, viruses harboring the PB1 K653 mutation display marked resistance to favipiravir (T-705), an inhibitor of viral RNA-dependent RNA polymerase, suggesting that mutations at this site may influence antiviral drug sensitivity in circulating strains, and have potential implications for clinical treatment and viral surveillance. In conclusion, our findings identify KCMF1 as a host restriction factor that suppresses IAV replication via ubiquitination of PB1 at K653.IMPORTANCEInfluenza A virus (IAV) continues to pose a major global health threat, and host factors that regulate viral replication are critical for understanding pathogenesis and guiding antiviral interventions. Here, we identify KCMF1 as a host E3 ubiquitin ligase that restricts IAV replication by promoting ubiquitination-dependent degradation of the viral polymerase subunit PB1. We further define lysine 653 (K653) of PB1 as a critical residue for this regulatory mechanism. Notably, mutation at this site enhances viral replication and pathogenicity while conferring resistance to favipiravir, a clinically approved inhibitor of viral RNA-dependent RNA polymerase. Collectively, these findings provide new mechanistic insights into host-virus interactions and highlight important considerations for antiviral drug use and surveillance of emerging viral variants.
Chronic hepatitis B infection affects an estimated 258 million people globally. Mother-to-child transmission (MTCT) accounts for over one-third of new cases in endemic regions and almost invariably results in lifelong infection if acquired at birth. Over the past four decades, universal vaccination, hepatitis B immunoglobulin (HBIG), and maternal antiviral prophylaxis have substantially reduced MTCT. However, limited access to antiviral therapy and HBIG in resource-constrained settings continues to hinder elimination efforts. This review focuses on HBV in pregnancy and breastfeeding, with emphasis on maternal antiviral prophylaxis. It outlines epidemiology, maternal risk factors, and the limitations of vaccination and HBIG. Evidence supporting tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF) is evaluated, alongside HBIG-free strategies and novel vaccine delivery platforms. Postpartum management, including hepatitis flares and the safety of breastfeeding during antiviral therapy, is also addressed. Maternal antiviral prophylaxis with TDF, and increasingly TAF, is central to preventing mother-to-child transmission of hepatitis B. HBIG-free strategies, earlier treatment initiation, and improved vaccines may further reduce transmission, particularly in resource-limited settings. Achieving WHO 2030 elimination goals will require policy commitment, affordable access, and integration of HBV prevention into routine maternal - child health care.
Antigenically drifted influenza A(H3N2) J.2.4.1 (subclade K) viruses predominated during the 2025-2026 Northern Hemisphere influenza season. To describe influenza activity and burden, characterize subclade K, evaluate susceptibility to influenza antivirals and postinfluenza vaccination antibodies, and estimate vaccine effectiveness. This surveillance study used multiple data sources, including (1) national surveillance of influenza-positive respiratory specimens collected by approximately 300 clinical laboratories and 100 public health laboratories from October 1, 2025, through March 14, 2026, a subset of which were further characterized; (2) serologic data of people who received 2025-2026 influenza vaccines; (3) influenza admissions data from the Influenza Hospitalization Surveillance Network (ie, 10% of US population) and the associated estimates of US burden; and (4) test-negative, case-control vaccine effectiveness estimates from the Virtual SARS-CoV-2, Influenza, and Other Respiratory Viruses Network. Influenza infection, hospitalization, and vaccination. Outcomes included influenza virus type, subtype, and clade; antiviral susceptibility; immunogenicity; influenza-associated outpatient and emergency department visits, hospitalizations, and mortality; estimated influenza illnesses, hospitalizations, and death; and estimated vaccine effectiveness. As of March 14, 2026, of the 55 318 influenza-positive respiratory specimens tested by public health laboratories, most (50 291 specimens [90.9%]) were influenza A, of which 40 779 (81.1%) were subtyped and 35 801 (87.8%) were A(H3N2). Of the 1754 characterized A(H3N2) viruses, most (1626 specimens [92.7%]) were subclade K. Postinfluenza vaccination neutralizing geometric mean antibody titers against subclade K were reduced 1.62 (95% CI, 1.29-2.02)-fold compared with the vaccine virus. All 1729 tested A(H3N2) viruses were sensitive to antivirals. Of the 27 881 recorded influenza hospitalizations, 15 426 (54.7%) were among female patients, and 15 051 (54.0%) were among patients aged 65 years or older. The estimated cumulative influenza-associated hospitalization rate was 80.0 per 100 000 which would correlate with estimates of between 28 000 000 to 49 000 000 illnesses, 360 000 to 740 000 hospitalizations, and 22 000 to 74 000 deaths in the US during the 2025-2026 season. Adjusted interim vaccine effectiveness estimates against influenza-associated emergency department or urgent care encounters and hospitalizations were 35% (95% CI, 33%-38%) and 27% (95% CI, 21%-34%), respectively. This surveillance study found that while antigenically drifted viruses predominated and caused substantial morbidity and mortality, influenza vaccines were associated with a reduced risk of influenza among those who were vaccinated, and recommended antivirals remained effective.
Nicotinamide phosphoribosyltransferase (NAMPT), a key rate-limiting enzyme in NAD+ synthesis, plays important roles in various physiological and pathological processes. However, the function and underlying mechanisms of NAMPT in influenza A virus (IAV) infection and pathogenesis remain ambiguous. Here, in vitro studies showed that NAMPT had profound effects on the replication of IAV. Treatment with the NAMPT inhibitor FK866 or disruption of NAMPT expression markedly attenuated the replication of various IAV subtypes, including H1N1, H3N2, and H9N2. Additionally, FK866-treated mice exhibited significant resistance to the IAV infection, as evidenced by a lower degree of tissue injury, slower body weight loss, and better survival than untreated animals challenged with IAV. Mechanistically, NAMPT interacted with viral polymerase basic protein 1 (PB1) and promoted the association of PB1 with polymerase acidic protein (PA) and polymerase basic protein 2 (PB2). Inhibition or depletion of NAMPT restrained the activity of viral RNA-dependent RNA polymerase (RdRp), thereby repressing IAV transcription and replication. Furthermore, we identified arginine 203 of PB1 as a critical residue for its interaction with NAMPT. The mutation (arginine 203 to proline, R203P) of PB1 hindered the association of PB1 with NAMPT, PA, and PB2, thereby impairing the RdRp activity and limiting IAV transcription and replication. Collectively, these findings uncover a critical role of NAMPT in regulating IAV replication and characterize the antiviral property of the NAMPT inhibitor FK866 against IAVs, providing insights for the development of novel anti-influenza strategies.IMPORTANCEInfluenza A virus (IAV) causes acute respiratory diseases in humans and animals and poses a great threat to public health, highlighting the urgent need for more effective antiviral treatments. Here, we found that the nicotinamide phosphoribosyltransferase (NAMPT) inhibitor FK866 significantly suppressed the replication of IAV in vitro and in vivo. Of note, FK866 markedly attenuated the replication of different IAV subtypes, including H1N1, H3N2, and H9N2, suggesting FK866 as a potential broad-spectrum antiviral against IAVs. Mechanistically, NAMPT interacted with viral polymerase basic protein 1 (PB1) and enhanced the association of PB1 with PA and PB2. FK866 could interfere with the viral polymerase activity, thereby limiting the synthesis of IAV viral RNA, complementary RNA, and messenger RNA. These findings reveal that the NAMPT inhibitor FK866 restricts IAV replication by perturbing viral polymerase activity and provide insights into the development of potential antivirals against IAV infection.
Human adenoviruses (HAdVs) are ubiquitous human pathogens that infect the respiratory, ocular, and gastrointestinal tissues. Despite the severity of these infections in immunocompromised patients, there are no clinically approved antiviral medications to treat HAdV infections. Over the past decade, many compounds have been found to interfere with different parts of the HAdV replication cycle. One critical barrier to developing a successful HAdV therapy arises if the drug concentration required for antiviral efficacy is clinically unachievable or too toxic for patient use. This problem can be diminished by using a combination of drugs that function synergistically, potentially allowing the use of lower drug concentrations that are clinically achievable and/or exhibit acceptable toxicity profiles. In this exploratory study, we examined the antiviral activity of pairwise combinations of six drugs that have been previously shown to disrupt HAdV replication: ivermectin, digitoxin, deguelin, niclosamide, rosiglitazone, and remdesivir. Combinations of these drugs showed a stronger reduction in HAdV progeny production, protein expression, and genome replication efficiency compared to their individual effects. These experiments serve to illustrate the feasibility and benefits of drug combinations that synergize against HAdV replication.