ETIDIOH - NEW

  ABSTRACT Influenza viruses utilize host proteases to activate the viral fusion protein, hemagglutinin (HA), into its fusion-competent form. Although proteolytic activation of HA is essential for virus replication, the cell-type dependence of HA activation within the airway epithelium and the subcellular location(s) in which it occurs are not well established. To address these questions, we investigated the proteolytic activation of HA in differentiated human airway epithelial cells using contemporary and historical H1N1 and H3N2 strains . We find that activation is efficient across viral strains and subtypes but depends on cellular tropism , with ciliated cells activating HA more effectively than non-ciliated cells. Similar to prior observations in immortalized cell lines, we find that HA activation occurs intracellularly, constraining the antiviral activity of host-directed protease inhibitors . These results establish that HA activation within the airway epithelium depends on c...

  Abstract Stabilizing the pre-fusion structures of antigenic proteins can enhance the effectiveness of antiviral vaccines . The pre-fusion form of hemagglutinin (HA) from the influenza virus typically adopts a stable trimeric structure . However, the recombinant ectodomain of HA from the A/California/04/2009 (H1N1) influenza virus formed a monomer in solution rather than the expected trimer. To promote trimer formation in the pre-fusion conformation, we redesigned five amino acid residues in the stem region of HA that are involved in trimerization. The engineered HA protein formed a stable trimer at both pH 8.0 and pH 5.5. Additionally, the thermal stability of the modified protein improved, as indicated by an approximately ten-degree increase in its denaturation temperature. Cryo-EM analysis at 2.2 angstrom resolution confirmed that the mutant HA protein adopted the pre-fusion structure. Furthermore, the stabilized mutant exhibited enhanced immunogenicity in mice . We applied the...

  Abstract Influenza A virus (IAV) infection is associated with a wide variety of neurological complications , of which mild complications like impaired cognitive functioning are most prominent . Even though several studies have shown that many influenza viruses can enter the CNS, the neuropathogenesis of seasonal ( H3N2 and H1N1 ) and pandemic (pH1N1 2009) IAV infections is poorly understood. Therefore, we aimed to investigate the cellular tropism, replication efficiency and associated functional consequences using a human stem cell-derived neural co-culture model of neurons and astrocytes . All viruses were able to infect neurons in the co-culture model, although this infection did not result in efficient replication and release of progeny virus. In addition, infection did not result in visible cell death or apoptosis. However, functional analyses revealed that IAV inoculation resulted in a reduction of spontaneous neural activity and a partial reduction of neural excitability. T...

  ABSTRACT Influenza A virus (IAV) in swine in the U.S. is surveilled to monitor genetic evolution to inform intervention efforts and aid pandemic preparedness . We describe data from the U.S. Department of Agriculture National Surveillance Plan for Influenza A Virus in Pigs from 2009 to 2022. Clinical respiratory cases were subtyped, followed by sequencing of hemagglutinin (HA) and neuraminidase (NA), and a subset of viruses was whole genome sequenced . Phylogenetic analysis identified geographic and temporal IAV reassortment hotspots . Regions acting as IAV genomic diversity sources or sinks were quantified, and dissemination was qualified and modeled. The dominant IAV clades were H1N2 (1B.2.1), H3N2 (1990.4.a), and H1N1 (H1-1A.3.3.3-c3). Internal genes were classified as triple-reassortant (T) or pandemic 2009 (P), and three genome constellations represented 73.5% of detections across the last 2 years. In some years, the distribution of IAV diversity was so narrow that it presen...

  Abstract The severity of influenza is often driven by an excessive host immune response rather than the virus itself , yet the key molecular drivers within specific immune cells remain poorly understood. While recent single-cell RNA sequencing studies have successfully identified immune populations involved, they have largely not identified the upstream drivers modulating their pro-inflammatory functions . Here we employed an integrated single-cell co-expression network to address this gap. Our analysis identified myeloid dendritic cells (mDCs) as central to pro-inflammatory response during infection. Through a multi-layered key driver analysis, we pinpointed C-type lectin , CLEC4E as a top candidate modulating this pathological inflammatory response . The role of CLEC4E was confirmed in an independent single-cell dataset from influenza-infected patients and further validated in vivo. Pharmacological inhibition of CLEC4E in a murine influenza model significantly reduced disease s...

  ABSTRACT Influenza A virus (IAV) infection of the respiratory tract can cause both respiratory and non-respiratory symptoms . Gastrointestinal (GI) symptoms such as diarrhea, vomiting, and abdominal pain can occur in persons with seasonal influenza A or novel IAV infections , but the extent to which IAVs can infect and replicate in GI tissues is understudied. The ongoing outbreak of A( H5N1 ) IAV in US dairy cattle associated with sporadic human infections has highlighted the potential public health threat posed by the introduction of infectious virus into materials that may be consumed by humans , such as milk. Here, we review epidemiologic reports documenting the frequency of GI complications in humans infected with seasonal and novel IAVs and present laboratory studies supporting the capacity of IAV to replicate in mammalian GI tissues , with an emphasis on A(H5N1) viruses. Studies assessing the ability of IAV to cause mammalian infection following consumption of virus-contain...

  ABSTRACT The mammary gland is an essential organ for milk production, providing essential immune and nutritional support to offspring and supplying dairy products for human consumption. In both humans and animals , the lactating mammary gland is susceptible to bacterial and viral infections , which can lead to mastitis and, in some cases, vertical transmission to offspring , with potential adverse effects on infant health. However, until recently, the role of respiratory viruses in mammary gland infection has been relatively understudied, particularly their ability to infect mammary epithelial cells and transmit through lactation. The recent emergence of highly pathogenic avian influenza H5N1 clade 2.3.4.4b in dairy cattle has demonstrated the virus’s capacity to replicate in the mammary gland, cause mastitis, and produce high viral loads in milk . This raises significant concerns about the potential for zoonotic transmission to humans and other animals in contact with infected d...

  Abstract In an effort to avert future pandemics, surveillance studies aimed at identifying zoonotic viruses at high risk of spilling over into humans act to monitor the "viral chatter" at the animal-human interface. These studies are hampered, however, by the diversity of zoonotic viruses and the limited tools available to assess pandemic risk. Methods currently in use include the characterization of candidate viruses using in vitro laboratory assays and experimental transmission studies in animal models. However, transmission experiments yield relatively low-resolution outputs that are not immediately translatable to projections of viral dynamics at the level of a host population. To address this gap, we present an analytical framework to extend the use of measurements from experimental transmission studies to generate more quantitative risk assessments. Specifically, we use within-host viral titer data from index and contact animals to estimate parameters relevant to tran...

  Antimicrob Agents Chemother HARFOOT R, Lawley B, Hernandez LC, Kuang J, et al Synthetic host defense peptide inhibits SARS-CoV-2 replication in vitro. Antimicrob Agents Chemother. 2025;69:e0170024. PubMed           Abstract available TATE M, Illingworth CJR, MacGregor G, Cunningham L, et al Clinical effectiveness, safety, and viral mutagenicity of oral favipiravir for COVID-19: results from a community-based, open-label, randomized Phase III trial. Antimicrob Agents Chemother. 2025;69:e0005425. PubMed           Abstract available ZHOU Y, Meng X, Li J, Zeng G, et al Safety, tolerability, and pharmacokinetics of anti-SARS-CoV-2 monoclonal antibody SA55 injection in healthy participants. Antimicrob Agents Chemother. 2025;69:e0056825. PubMed           Abstract available GOMI S, Price E, Burgoyne H, Faozia S, et al Omadacycline exhibits anti-inflammatory properties a...

  Abstract Reassortment between different influenza strains occurs when they co-infect the same host cell . The emergence of a reassortant virus depends on both its intrinsic fitness and extrinsic factors , including pre-existing humoral immunity . The generation of pandemic strains , such as H2N2 and H3N2 , and zoonotic influenza A viruses, like H5N6, H5N8, and H7N9 , in birds is suggested to be the result of extensive selection by pre-existing antibodies . To further explore the role of humoral immunity in reassortment , we generated two divergent fluorescent protein-expressing viruses and used strain-specific and cross-reactive monoclonal antibodies (mAbs) to assess the impact of cross-immunity on reassortment. Our results indicate that all mAbs altered the genotypic diversity and significantly reduced the release of progeny virions in co-infected cells both in vitro and in vivo. Moreover, antibody transfer studies in mice revealed protection from challenge with divergent pathog...

  Abstract Vaccine responses vary widely in human studies. Here we pooled data measuring 66 cytokines from 4 different inactivated influenza vaccine (IIV) cohorts over 5 seasons (N=581) and identified a significant correlation between baseline/day 0 serum IL-18 and IFN-β concentrations and the antibody response on day 28. We investigated this further in human tonsil and spleen organoids , and found that several cytokines, including multiple Type I IFNs (IFN-β and others), IL-21, IL-12, IL-10, but not IL-18 or its downstream Type II IFN (IFN-β), could adjuvant the IIV vaccine to enhance the antibody response . The live attenuated influenza vaccine (LAIV) induced a stronger antibody response than the inactivated one in organoids. Adding a single cytokine, IFN-β, recapitulated most of the live vaccine-specific cytokine activation program and increased the antibody response of the inactivated vaccine to that of the live vaccine. Thus, the human vaccinees and the organoid data showed th...

  ABSTRACT Airborne transmissibility of avian influenza viruses (AIVs) in humans is considered an essential component of their pandemic risk . Although several viral factors regulating airborne transmission (AT) have been delineated, it is not known what, if any, responses at the respiratory epithelia are determinants of AIV AT. Using responses in the ferret nasal epithelium to a panel of H1N1 AIVs, we describe host responses that segregate with AT phenotypes . AIV infection upregulated interferon alpha and gamma responses and IL-6 JAK-STAT signaling and downregulated oxidative phosphorylation . Single-cell transcriptomics revealed that cellular genotoxic stress and NF-kB, interferon, and cell fate pathways differentiated host responses to AIVs with different transmissibilities. These responses culminated in greater AIV antigen-containing exudate and debris in the respiratory spaces of the nasal epithelium of ferrets inoculated with AT AIVs. More abundant CMPK2, SP100, and CXCL10 t...

  BMJ WISE J RFK Jr bans thiomersal from influenza vaccines in "safety" move. BMJ. 2025;390:r1576. PubMed          Epidemiol Infect KELLY GE, Petti S, Noah N Excess respiratory, circulatory, neoplasm, and other mortality rates during the Covid-19 pandemic in the EU and their implications. Epidemiol Infect. 2025;153:e86. PubMed           Abstract available Eur J Epidemiol ORTQVIST AK, Soderling J, Magnus MC, Urhoj SK, et al COVID-19 infection increases the risk of venous thromboembolism during pregnancy and the postpartum period. Eur J Epidemiol. 2025;40:779-788. PubMed           Abstract available BAUMKOTTER R, Yilmaz S, Chalabi J, Ten Cate V, et al Risk tools for predicting long-term sequelae based on symptom profiles after known and undetected SARS-CoV-2 infections in the population. Eur J Epidemiol. 2025;40:789-801. PubMed         ...

ABSTRACT Seasonal influenza causes 290,000–650,000 deaths annually, with vaccination efficacy ranging from 10 to 60%. The emergence of drug-resistant and highly pathogenic avian influenza viruses underscores the urgent need for novel protective strategies . Epidemiological observations have long suggested that certain vaccines, such as Bacillus Calmette-Guérin (BCG), can provide protection against diverse pathogens (S. Biering-Sørensen, P. Aaby, N. Lund, et al., Clin Infect Dis 65:1183–1190, 2017, https://doi.org/10.1093/cid/cix525 ; M.-L. Garly, C. L. Martins, C. Balé, et al., Vaccine 21:2782–2790, 2003, https://doi.org/10.1016/s0264-410x(03)00181-6 ; C. A. G. Timmermann, S. Biering‐Sørensen, P. Aaby, et al., Trop Med Int Health 20:1733–1744, 2015, https://doi.org/10.1111/tmi.12614 ). While the cellular and molecular mechanisms underlying such protection remain incompletely understood, emerging research offers critical insights into innate immune system modulation (B. Cirovic, L. C. J...

Abstract Influenza A virus (IAV) poses a significant global health risk, with highly pathogenic strains like H5N1 (CFR ~52%) causing severe disease compared to less lethal but more transmissible strains like H1N1 (CFR 0.01-0.03%). Although IAV primarily infects lung epithelial cells , causing cell death and tissue damage , the molecular basis of strain-specific pathogenesis remains poorly understood. Here we show that in cell culture , H5N1 induced more rapid and extensive cell death than H1N1. Since Interferon (IFN) signaling is key to innate immunity, we examined its role in virus-induced cell death using STAT1-knockout A549 cells and JAK/STAT pathway inhibitors like Baricitinib . Both approaches reduced cell death across various IAV strains, including H1N1, H5N1, H7N9 , and H3N2 . However, inhibition increased viral titers , raising concerns about its clinical use in isolation. To overcome this, we tested a combination of Oseltamivir (antiviral) and Baricitinib (anti-inflammatory). ...

Key Points -- Question: What were the clinical characteristics, management approaches, and outcomes among children with influenza-associated acute necrotizing encephalopathy (ANE) in the US during the 2023-2024 and 2024-2025 influenza seasons? -- Findings:   In this multicenter case series of 41 children from 23 US hospitals , influenza-associated ANE carried a 27% mortality rate despite multimodal therapy. Most patients (76%) had no significant medical history , despite 15 of 32 tested (47%) having genetic risk alleles potentially related to risk of ANE identified during diagnostic evaluation. The H1 2009 influenza A strain predominated (34% of cases), and only 16% had received seasonal influenza vaccination . Among survivors, 63% had moderate to severe disability at 90-day follow-up. -- Meaning:  Influenza-associated ANE represents a rare but devastating neurologic complication primarily affecting previously healthy children. The high morbidity and mortality emphasize t...

Highlights •  Mol shows greater antiviral effects against IAV and IBV in cell cultures. •  Mol and Ose together showed a synergistic effect against IAV. •  In mice, Mol alone or with Ose reduced lung injury and viral load. Abstract Oseltamivir, a neuraminidase inhibitor, is widely used in the clinic for treating influenza virus infections . However, suboptimal efficacy and risk of drug resistance development remain major challenges. Molnupiravir , a ribonucleoside analog, was originally developed to treat influenza, but was repurposed and first approved for treating COVID-19 in 2021. Considering their complementary mode-of-actions, this study aimed to investigate the combinatorial activities of oseltamivir and molnupiravir against influenza virus infections . In cell culture models, we found that β-d-N4-hydroxycytidine (NHC), the active form of molnupiravir, exerted more potent antiviral activities against influenza A and B viruses , when compared to oseltamivir treatment...

Abstract The emergence of highly pathogenic avian influenza (HPAI) H5N1 (clade 2.3.4.4b, genotype B3.13) in dairy cattle presents substantial challenges to the agricultural sector and public health. Mechanistic studies of infection and transmission in cattle have proven difficult due to animal handling restrictions as well as limited availability of established cell culture models. Primary Bovine Embryonic Fibroblasts (BeEFs) were collected from a Montana cow and are investigated here as a model to study influenza A virus (IAV) infection dynamics . We compared sialylation profiles, infectious virus production, viral replication, and plaque morphology in both BeEFs and chicken DF-1 cells following infection with the bovine HPAI H5N1 and an earlier 2.3.4.4b genotype (B1.1) isolated in 2022. The data presented here show increased viral fitness of the bovine origin HPAI H5N1 strains across multiple species and bovine susceptibility to human seasonal IAV. This study highlights the ability o...