Search Results (7,254)

Bluetongue (BT) is an infectious, non-contagious, arthropod-borne viral disease of ruminants, and has a severe impact on livestock. It is caused by Bluetongue virus (BTV), a double-stranded (ds) RNA virus with a segmented genome (10 segments), belonging to the Seoreoviridae family, Orbivirus genus. Over the last 25 years, Europe has suffered multiple incursions of different BTV serotypes with serious consequences, which have mainly been controlled thanks to vaccination. In the case of Spain, from 2000 to 2023, BTV serotypes 1, 2, 4 and 8 have caused epidemics, and, sporadically, BTV-1 and -4 were detected in the same area and period. In 2024, BTV serotypes 1, 3 and 8 circulated simultaneously in the southwest of the country, causing a severe clinical impact in sheep but also in cattle and a multitude of outbreaks. Additionally, despite vaccination, serotype 4 also circulated that year, especially in areas where the other serotypes were already circulating. Whole-genome sequencing and phylogenetic analyses allowed us to confirm that serotypes 1 and 4 were homologous to viruses circulating in the country since 2000s, while serotypes 3 and 8 were homologous to BTVs recently notified in neighboring countries. In this context, many BTV co-infections of two or more different serotypes were confirmed by serotype-specific RT-PCRs, both in farms and individual animals. An epidemic caused by four serotypes coinciding in space and time had never occurred before in Spain, being a challenge for the diagnosis and control of this disease. Moreover, it could have favored the appearance of reassortant viruses with an unknown virulence, posing an additional risk. The data presented here raise the question of whether the co-circulation of different BTV strains, an exceptional situation, could become the new normal in certain areas of Europe. Full article

Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) represent fundamental cellular adaptive mechanisms that maintain protein homeostasis and metabolic balance. Many RNA viruses, particularly flaviviruses such as dengue virus (DENV), Zika virus (ZIKV), West Nile virus (WNV), yellow fever virus (YFV), and Japanese encephalitis virus (JEV), extensively remodel the ER to establish replication compartments and assemble progeny virions. This massive reorganization disrupts ER homeostasis, leading to UPR activation. Emerging evidence reveals that flaviviruses not only trigger but also manipulate the three UPR branches—PERK, IRE1, and ATF6—to optimize viral translation, replication, and egress. In parallel, flavivirus infection profoundly alters host lipid metabolism and promotes dynamic changes in lipid droplets (LDs), key organelles that mediate lipid storage and serve as scaffolds for viral replication and assembly. The UPR intimately connects to LD biogenesis through transcriptional and translational programs mediated by XBP1, ATF4, and ATF6, thereby coupling ER stress responses to lipid remodeling and energy homeostasis. This intricate crosstalk between UPR and LDs creates a metabolic and structural niche favorable for viral replication but detrimental to host cell integrity. This review provides a comprehensive analysis of the molecular mechanisms by which flaviviruses exploit ER stress and the UPR to reprogram lipid metabolism and LD dynamics. We highlight the dual role of UPR signaling in promoting adaptive lipid synthesis and initiating cell death under prolonged stress, discuss recent insights into ER–LD interactions during flavivirus infection, and explore therapeutic opportunities targeting UPR–lipid metabolic pathways as broad-spectrum antiviral strategies. Understanding this interconnected network will advance our knowledge of viral pathogenesis and identify new avenues for host-directed antiviral intervention. Full article

Viral internal ribosome entry sites (IRESs) are specialized RNA structures that facilitate cap-independent translation as a strategy to usurp the host translational machinery. The Type 6 IRESs are the most streamlined mechanism to date, as they adopt a three pseudoknot RNA structure to initiate factorless translation initiation by directly recruiting the ribosome and drive translation. The Halastavi árva virus (HalV) IRES represents the most minimalistic subclass identified to date, whereby the IRES lacks specific pseudoknot domains that bind to the 40S subunit but instead recruits pre-assembled 80S ribosomes via a mechanism that is not fully understood. Here, we examined cellular conditions that can support HalV IRES translation. We demonstrated that the HalV IRES is translationally active in insect Sf21 lysates and Drosophila S2 cells, but inactive in mammalian RRL and wheat germ extract. Cells treated with heat shock or serum starvation suppressed HalV IRES activity, whereas virus infection robustly enhanced HalV IRES-mediated translation. Finally, the HalV IRES can support viral translation and replication using a heterologous viral replicon. These findings highlight the context-specific cellular conditions that allow ribosome assembly and translation by a factorless minimalist IRES. Full article

Infectious bursal disease virus (IBDV) is an immunosuppressive pathogen posing a major threat to poultry health worldwide. Its marked phenotypic variability is driven by the rapid evolution of its double-stranded RNA genome, primarily achieved through mutation and reassortment. Although extensive evidence has been generated on molecular determinants of antigenicity and pathogenicity, interpretation is often hindered by heterogeneity and lack of systematicity. This scoping review synthesizes over 35 years of research on amino acid positions influencing IBDV phenotype. A total of 62 studies reporting 107 functionally relevant sites were identified and critically appraised based on evidence type, methodological approach, and ability to infer causality. The results confirmed the central role of VP2, particularly its hypervariable region, while also highlighting the increasingly recognized contribution of other viral proteins. Despite good agreement, comparability across studies was limited by substantial heterogeneity in experimental design and the frequent focus on partial genomic regions. Notably, some molecular markers were context-dependent or inconsistently associated with phenotypic outcomes, underscoring the need for proper interpretation of molecular determinants and for more standardized and comprehensive approaches, including full-genome analyses and reverse genetics. Overall, these findings provide a valuable framework for enhancing molecular diagnostics and supporting the rational design of next-generation vaccines. Full article

Henipaviruses (HNVs), including Nipah virus (NiV) and Hendra virus (HeV), are highly pathogenic and often lethal zoonotic viruses with broad species tropism and no approved human vaccines. The emergence of genetically divergent HNVs—including Ghana virus (GhV), Langya virus (LayV), and Mojiang virus (MojV)—emphasizes the need for broadly protective countermeasures. Here, we evaluated the antibody (Ab) responses to sequential mRNA vaccines encoding the membrane-bound attachment glycoprotein (gG) from NiV, GhV, and/or LayV in a pilot study with Indian rhesus macaques. Serum binding Ab responses were quantified by ELISA against five soluble gG antigens (NiV, HeV, GhV, LayV, MojV). Functional activity was assessed by neutralization assays using NiV, HeV, and GhV pseudoviruses, and by receptor-blocking ELISA. Sequential vaccination induced high-titer IgG binding against all five HNV gGs with increasing breadth after each dose. Pan-genus regimens elicited moderate neutralizing Ab titers against NiV, HeV, and GhV, whereas the NiV-only regimen elicited potent but narrow neutralization against NiV and HeV. Conversely, the GhV-LayV-GhV regimen elicited strong binding to GhV, LayV, and MojV gG and robust neutralization of GhV pseudovirus, but limited cross-reactivity to NiV and HeV. In this pilot study, we demonstrated that mRNA vaccination can elicit broadly reactive binding and neutralizing Ab responses across phylogenetically distant HNVs. Additionally, we show GhV pseudovirus neutralization for the first time. Collectively, these data provide a foundation for the development of next-generation pan-genus HNV vaccines capable of mitigating future HNV outbreaks. Full article

Epstein–Barr virus (EBV)-positive primary central nervous system lymphoma (PCNSL) is a rare entity typically associated with profound immunosuppression, most commonly in transplant recipients or individuals with HIV. We report a case of EBV-positive PCNSL arising in a 75-year-old male with myasthenia gravis receiving chronic mycophenolate mofetil (MMF) therapy outside the transplant setting. The patient presented with progressive neurological deficits, and brain magnetic resonance imaging demonstrated multiple enhancing lesions. Stereotactic biopsy revealed diffuse large B-cell lymphoma of non–germinal center subtype with immunoblastic features and EBV-encoded RNA (EBER) positivity, confirming EBV-positive PCNSL. MMF was discontinued, and the patient was treated with rituximab and high-dose methotrexate, resulting in stable disease. This case highlights that prolonged MMF therapy may confer sufficient immunosuppression to permit EBV-driven lymphoproliferative disease even in non-transplant patients. Early recognition, withdrawal of immunosuppression, and initiation of methotrexate-based chemotherapy can lead to favorable outcomes. Full article

Ixodid ticks are vectors for a plethora of pathogens, including the Crimean–Congo hemorrhagic fever virus (CCHFV), which causes severe disease in humans. Two autochthonous CCHF human cases were reported in 2025 in Greece. The aim of the present study was to gain a better insight into the geographic distribution and prevalence of CCHFV and the related Aigai virus (AIGV) in ticks in Greece. Therefore, 680 ticks (135 Hyalomma and 545 Rhipicephalus ticks) collected during 2024 from livestock (sheep, goats, cattle) and from the environment were tested for CCHFV and AIGV. AIGV was detected in 12 adult Rhipicephalus bursa ticks (12/511, 2.3%), while all Hyalomma ticks and R. bursa nymphs were negative for both viruses. AIGV-positive ticks were collected in May and June from goats and sheep in two distantly located regional units of Greece. AIGV sequences from partial S RNA segment differ from the prototype AIGV strain (AP-92) by 10.3% and 1.4% at the nucleotide and amino acid level, respectively. Integrated surveillance studies are needed in ticks, humans, wild and domestic animals within a One Health framework to gain a better insight into the epidemiology of CCHF in Greece, while clinical research is needed to elucidate the impact of AIGV in public health. Full article

Chikungunya virus (CHIKV) infection presents a wide spectrum of clinical outcomes, ranging from mild self-limiting disease to severe and fatal manifestations, which are influenced by both host and viral factors. Animal models are essential for elucidating CHIKV pathogenesis and for preclinical evaluation of antiviral strategies; however, a well-characterized model evaluating the effect of different viral doses in AG129 mice remains limited. In this study, we investigated the clinical, virological, and pathological outcomes of CHIKV infection in male AG129 mice inoculated intraperitoneally with different viral doses (10, 100, and 1000 PFU/mL) of a Brazilian strain belonging to the East/Central/South African (ECSA) lineage. Lower-dose inoculation (10 PFU/mL) resulted in a milder disease course, characterized by transient viremia, limited tissue viral dissemination, minimal histopathological alterations, partial survival, and viral clearance. In contrast, higher doses (≥100 PFU/mL) led to rapid systemic viral dissemination, severe histopathological damage in the spleen, liver, and kidneys, and uniform lethality. Viral RNA was detected in serum and multiple organs in a time-dependent manner, with limited differences among inoculum doses in most tissues. Notably, dose-related differences were observed in specific compartments and time points, particularly in hind-limb muscles at early time points and in serum at later stages. Full article

Human T-cell leukemia virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic inflammatory disease driven by HTLV-1-infected CD4⁺ T cells; however, the phenotypic and functional characteristics of disease-associated T-cell subsets remain incompletely understood. We analyzed samples using flow cytometry (n = 3–5 per group) and RNA-seq (n = 13), focusing on CADM1^highCD4⁺ T cells enriched for HTLV-1-infected cells to evaluate a transferrin receptor (TfR)-expressing subset. TfR⁺CADM1^highCD4⁺ T cells were detected in both asymptomatic carriers and patients with HAM, but their frequency among CD4⁺ T cells was higher in HAM patients. These cells exhibited a Treg-like phenotype with higher Foxp3 and CTLA-4 expression than TfR⁻ cells and showed increased Ki-67 positivity, consistent with proliferation. Despite this phenotype, they produced interferon-γ, indicating inflammatory potential, while Foxp3 expression was lower in HAM patients than in asymptomatic carriers, suggesting a more inflammatory phenotype. Furthermore, TfR transcript levels (RNA-seq TPM) correlated with clinical indicators of disease activity, including neopterin and CXCL10 protein levels, and the Osame motor disability score. Collectively, these findings suggest that TfR identifies a proliferative, Foxp3-low, Treg-like inflammatory CD4⁺ T-cell subset that is associated with disease activity in HAM. Full article

Pathogen manipulation of host behavior is a widespread evolutionary strategy to enhance its transmission, yet whether different pathogens elicit distinct behavioral and molecular responses in the same host remains poorly understood. We performed parallel behavioral assays and comparative transcriptomic analyses on third-instar Lymantria dispar larvae infected with Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV, virus), Staphylococcus aureus (bacterium) and Metarhizium anisopliae (fungus). Climbing height was recorded over 72 h post-infection, and gene expression pattern was profiled using RNA-seq at 72 h. Only LdMNPV infection induced significant, sustained upward climbing behavior among the three pathogen infection groups. All three pathogens activated Toll and IMD immune pathways, but LdMNPV triggered substantially broader transcriptomic reprogramming. Notably, the virus specifically upregulated multiple energy metabolism pathways (nicotinate/nicotinamide metabolism, pyruvate metabolism, TCA cycle and oxidative phosphorylation) and the neuroactive ligand-receptor interaction pathway—a pattern absent in bacterial and fungal infections. LdMNPV drove tree-top disease through a virus-specific, multi-system manipulation strategy that couples metabolic activation with neural signaling modulation. This comparative study reveals fundamental differences in behavioral manipulation across pathogen kingdoms and provides candidate pathways for functional validation. Full article

Infection of the large yellow croaker (Larimichthys crocea) embryo cell line YCE1 with megalocytivirus strain FD201807 leads to accumulation of capsid-deficient viral intermediates within intracellular vesicles at 48 h post-infection (a phenotype associated with non-lytic egress), which coincides with the initial peak of viral genomic copies. To characterize the host molecular response during this critical stage, we performed time-course RNA sequencing at 24, 48, 96, and 144 hpi. Integrated analysis identified 6661 differentially expressed genes (DEGs) and 1138 differential alternative splicing (DAS) events affecting 892 genes, with DAS event abundance peaking at 48 h. DAS genes in autophagy and Golgi vesicle transport pathways, both integral to animal innate immunity, were significantly enriched exclusively at this timepoint, featuring novel mutually exclusive exon (MXE) isoforms in gopc (Golgi-associated PDZ and coiled-coil motif containing) and rint1 (RAD50 interactor 1). Weighted gene co-expression network analysis (WGCNA) of DEGs identified mapk9 (mitogen-activated protein kinase 9) and map1lc3a (microtubule-associated protein 1 light chain 3 alpha) as hub genes within modules enriched for autophagy-related functions. Separate co-expression analysis of DAS genes revealed rnf5, rimoc1, and golga4 as hub genes, with gopc exhibiting only a single linkage to rnf5. These findings implied concurrent transcriptional and virus-induced host splicing regulation of vesicle-associated innate defense pathways and suggest that splicing-derived features may serve as potential candidates for diagnostics or prevention against megalocytivirus disease in L. crocea. Full article

Nipah virus (NiV) is a highly pathogenic zoonotic paramyxovirus responsible for sporadic outbreaks of severe disease with high case fatality rates in South and Southeast Asia. Human infection occurs through spillover from natural reservoirs, primarily fruit bats, or via human-to-human transmission, and is characterized by a broad clinical spectrum ranging from asymptomatic infection to acute respiratory disease and fatal encephalitis. Following entry via ephrin-B2 and ephrin-B3 receptors, NiV exhibits marked endothelial and neuronal tropism, leading to systemic vasculitis, disruption of the blood–brain barrier, and direct infection of the central nervous system. Disease progression is driven by a complex interplay between viral replication strategies and host immune responses. NiV effectively counteracts innate immunity through multiple viral proteins that inhibit interferon signaling, while simultaneously inducing dysregulated inflammatory responses that contribute to tissue damage and multi-organ failure. Neurological involvement represents the most severe manifestation, often resulting in acute or relapsing encephalitis with long-term sequelae among survivors. Despite the severity of the disease, no licensed antiviral therapies or human vaccines are currently available. Therapeutic development has focused on neutralizing monoclonal antibodies targeting viral glycoproteins and small-molecule antivirals that inhibit viral RNA synthesis, both of which show promising results in preclinical models, but remain limited by timing and translational challenges. In parallel, several vaccine platforms—including viral vectors, mRNA-based constructs, and recombinant protein subunits—have advanced to early-phase clinical trials, demonstrating encouraging immunogenicity. Beyond biomedical interventions, effective outbreak containment relies on integrated public health strategies. The “Kerala model” highlights the importance of rapid case identification, isolation, contact tracing, and community engagement within a One Health framework to mitigate transmission and reduce mortality. This review synthesizes the current knowledge on NiV pathogenesis, immune evasion, clinical manifestations, and emerging therapeutic and vaccine strategies, while highlighting critical gaps and future directions for improving the preparedness and response to this high-consequence emerging pathogen. Full article

This review critically examines the inhibition of viral entry as an emerging disease-modifying strategy in chronic hepatitis B (HBV) and delta (HDV) virus infection, with particular emphasis on bulevirtide, the first-in-class of the sodium taurocholate cotransporting polypeptide entry inhibitor. This paper summarizes the analysis of 7 clinical trials that either underpinned the registration of bulevirtide or are important European real-life trials. We synthesize virological, pathophysiological and clinical evidence, highlighting the impact of this novel bulevirtide-based therapy on virological control, liver inflammation, fibrosis dynamics and long-term prognosis, as well as the limitations of this therapy. The observation of these trials is a greater than 2 log decrease from baseline in hepatitis D virus ribonucleic acid (HDV RNA) in 54–92% of patients and normalization of alanine transaminase (ALT) in 48.8–74% of patients after 23–144 weeks of treatment, and a significant decrease in liver fibrosis, as quantified by Fibroscan, at 12 months of treatment. The conclusion of the study is that this therapy represents an important leap in the etiological approach to chronic HDV infection and in improving the prognosis of these patients, but future clinical studies are needed to define the criteria for discontinuation of therapy, the long-term impact, as well as studies targeting new therapies that can intervene in other stages of the HDV and HBV life cycle not only to achieve HDV RNA negativity but also HBsAg clearance. Full article

The efficacy of the host antiviral response against Influenza A virus (IAV), a leading cause of global pandemics, hinges upon the rapid recognition of the pathogen and the prompt activation of immune mechanisms. Nevertheless, the epigenetic landscape that orchestrates this antiviral response remains largely elusive. Here, we identify histone demethylase JMJD2D as a critical regulator in defense against IAV infection. A significant upregulation of JMJD2D expression was observed clinically in response to IAV infection, indicating that JMJD2D may play a role in regulating IAV infection. Indeed, JMJD2D-deficient mice exhibit increased susceptibility to IAV, characterized by elevated viral loads, severe lung tissue damage, and reduced survival rates, suggesting that JMJD2D plays an essential role in defense against IAV infection. Consistently, knockdown or pharmacological inhibition of JMJD2D in lung cells suppressed IAV replication and the IAV-triggered innate immune response. Mechanistically, JMJD2D suppressed IAV infection by removing H3K9me3 at the promoter region of retinoic acid inducible gene-I (RIG-I) and cooperating with NF-κB to enhance the expression of RIG-I, a critical sensor for IAV RNA. This study identifies JMJD2D as an epigenetic rheostat that governs RIG-I-mediated antiviral signaling, highlighting its potential as a therapeutic target for mitigating severe IAV infection. Full article

Influenza A virus (IAV) surveillance in swine relies heavily on molecular detection, yet RNA stability in diagnostic specimens such as oral fluids can be rapidly compromised when cold-chain conditions are not maintained. This pilot study evaluated the ability of four molecular-grade carbohydrates (20% trehalose, sorbitol, sucrose, and mannitol) and two commercial nucleic acid stabilizers (PrimeStore^® MTM and RNAlater^®) to preserve RT-qPCR-detectable IAV RNA in swine oral fluids exposed to field-relevant stress conditions. Oral fluid samples collected from pigs experimentally infected with H1N2 (Study 1: n = 150; DPIs 2, 3, 4) or with H1N2 and H3N2 (Study 2: n = 58; DPI 5) were subjected to storage at 25 °C for up to 144 h (Study 1) or 2, 5, 10, or 15 freeze–thaw cycles (Study 2), with DPIs (Study 1) or subtypes (Study 2) serving as biological replicates, given the limited sample size. IAV detection was quantified as efficiency standardized Cq values (ECq) and analyzed using a linear mixed-effects model. Overall, both carbohydrates (trehalose, sorbitol, sucrose) and commercial stabilizers maintained higher ECq values than untreated oral fluids under both thermal and freeze–thaw stress conditions. Due to the limited sample size, these findings should be interpreted cautiously, yet they demonstrate the potential utility of carbohydrates as a low-cost, non-inactivating alternative for stabilizing IAV RNA in field-collected oral fluids. Full article