Search Results (5,432)

Over the decades, cattle have not been considered primary hosts for influenza A viruses (IAV), and their role in influenza epidemiology has been largely unrecognized. While bovines are known reservoirs for influenza D virus, the recent emergence of highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b in U.S. dairy cattle marks an alarming shift in influenza ecology. Since March 2024, this virus has affected thousands of dairy cows, causing clinical signs such as fever, reduced feed intake, drastic declines in milk production, and abnormal milk appearance. Evidence suggests that the virus may be replicated within mammary tissue, raising urgent concerns about milk safety, foodborne transmission, and occupational exposure. This review highlights the unprecedented expansion of viruses into bovine populations, exploring the potential for host adaptation, and interconnected roles of pets, peridomestic animals, and human exposure within shared environments. The potential impacts on dairy production, food safety, and zoonotic spillover highlight the urgent need for integrated One Health surveillance to stay ahead of this evolving threat. Full article

Plant viruses have been traditionally considered pathogens restricted to plant hosts. However, recent studies have shown that some plant viruses can infect and replicate in filamentous fungi and oomycetes, suggesting that their host range is broader than previously thought, and that their ecological interactions are more complex. In this study, we investigated the ability of the well-characterized positive-sense RNA plant virus Tobacco mosaic virus (TMV) to replicate in four major phytopathogenic fungi from different taxonomic groups: Botrytis cinerea, Fusarium oxysporum f. sp. lycopersici, Verticillium dahliae, and Monilinia fructicola. Using a recombinant TMV-based vector expressing a green fluorescent protein (TMV-GFP-1056) as reporter, we demonstrated that TMV can enter, replicate, and persist within the mycelia of B. cinerea and V. dahliae—at least through the first subculture. However, it cannot replicate in F. oxysporum f. sp. lycopersici and M. fructicola. RNA interference (RNAi) is a conserved eukaryotic epigenetic mechanism that provides an efficient defence against viruses. We explored the role of RNAi in the interaction between TMV and the mycelia of V. dahliae and B. cinerea. Our results revealed a strong induction of the Dicer-like 1 and Argonaute 1 genes, which are key compounds of the RNA silencing pathway. This RNAi-based response impaired TMV-GFP replication in both fungi. Notably, despite viral replication and RNAi activation, the virulence of V. dahliae and B. cinerea on their respective host plants remained unaffected. These findings reinforce the emerging recognition of cross-kingdom virus transmission and interactions, which likely play a crucial role in pathogen ecology and viral evolution. Understanding these virus–fungus interactions not only sheds light on RNAi interference silencing mechanisms but also suggests that plant viruses like TMV could serve as simple and effective tools for functional genomic studies in fungi, such as in V. dahliae and B. cinerea. Full article

We aimed to explore SARS-CoV-2 evolution during in vitro neutralisation using next generation sequencing, and to determine whether sera from individuals immunised with two doses of the Pfizer-BioNTech vaccine (BNT162b2) were as effective at neutralising the variant of concern (VOC) Delta (B.1.617.2) compared to the earlier lineages Beta (B.1.351) and wild-type (A.2.2) virus. Using a live-virus SARS-CoV-2 neutralisation assay in Vero E6 cells, we determined neutralising antibody titres (nAbT) against three SARS-CoV-2 strains (wild type, Beta, and Delta) in 14 participants (vaccine-naïve (n = 2) and post-second dose of BNT162b2 vaccination (n = 12)), median age 45 years [IQR 29–65]; the median time after the second dose was 21 days [IQR 19–28]. The determination of nAbT was based on cytopathic effect (CPE) and in-house quantitative reverse transcriptase real-time quantitative polymerase chain reaction (RT-qPCR) to confirm SARS-CoV-2 replication. A total of 110 representative samples including inoculum, neutralisation breakpoints at 72 h, and negative and positive controls underwent genome sequencing. By integrating live-virus neutralisation assays with deep sequencing, we characterised both functional antibody responses and accompanying viral genetic changes. There was a reduction in nAbT observed against the Delta and Beta VOC compared with wild type, 4.4-fold (p ≤ 0.0006) and 2.3-fold (p = 0.0140), respectively. Neutralising antibodies were not detected in one vaccinated immunosuppressed participant and the vaccine-naïve participants (n = 2). The highest nAbT against the SARS-CoV-2 variants investigated was obtained from a participant who was vaccinated following SARS-CoV-2 infection 12 months prior. Limited consensus level mutations occurred in the various SARS-CoV-2 lineage genomes during in vitro neutralisation; however, consistent minority allele frequency variants (MFV) were detected in the SARS-CoV-2 polypeptide, spike (S), and membrane protein. Findings from countries with high COVID-19 incidence may not be applicable to low-incidence settings such as Australia; as seen in our cohort, nAbT may be significantly higher in vaccine recipients previously infected with SARS-CoV-2. Monitoring viral evolution is critical to evaluate the impact of novel SARS-CoV-2 variants on vaccine effectiveness, as mutational profiles in the sub-consensus genome could indicate increases in transmissibility and virulence or suggest the development of antiviral resistance. Full article

Hepatitis B virus (HBV) remains a major global health challenge, with over 296 million people chronically infected worldwide. Despite the availability of antiviral therapies, a functional cure is rarely achieved, highlighting the need for novel therapeutic strategies. RNA 5-methylcytosine (m⁵C) is a pivotal epitranscriptomic mark implicated in RNA stability, transport, and translation. Emerging evidence shows that m⁵C is conserved within HBV RNA and plays critical roles in the viral life cycle. This review provides a comprehensive overview of the molecular mechanisms governing m⁵C deposition and recognition, summarizes recent advances in m⁵C biology, and highlights the emerging role of epitranscriptomic m⁵C regulation in HBV infection. We discuss the identification of HBV-specific m⁵C sites, the functions of key regulatory enzymes, and their interplay in viral RNA stabilization and evasion of innate immune responses. Interplay between m⁵C and other RNA modifications—particularly N6-methyladenosine (m⁶A)—is examined alongside virus-specific m⁵C regulation in EV71, HIV, HCV, EBV, and SARS-CoV-2. Potential links between m⁵C dysregulation and HBV-induced hepatocarcinogenesis are outlined, and emerging therapeutic strategies targeting the m⁵C machinery are highlighted. Together, these insights position the epitranscriptomic landscape as a promising avenue for innovative antiviral strategies. Full article

Influenza A virus pandemics pose a persistent global health threat, and emerging antiviral resistance underscores the critical importance of developing novel broad-spectrum therapeutic agents. Building on licorice’s (Glycyrrhiza spp.) historical use in traditional Chinese medicine for respiratory infections—as documented in the Chinese Guidelines for Diagnosis and Treatment of Influenza—and its demonstrated anti-SARS-CoV-2 activity, we identified licoflavone B as a potent anti-influenza agent, bridging ethnopharmacological knowledge with mechanistic validation. In this study, we identified licoflavone B, a natural flavonoid derived from licorice (Glycyrrhiza spp.), as a potent inhibitor of diverse influenza viruses, including multiple influenza A subtypes and type B virus. Mechanistic studies revealed that licoflavone B selectively targets the viral RNA-dependent RNA polymerase (RdRp), effectively suppressing viral replication. The compound exhibits a favorable selectivity index (SI = 14.9–29.9), indicating a promising therapeutic window. Molecular docking simulations identified potential binding interactions between licoflavone B and regions of the RdRp complex, which were further validated by dose-dependent inhibition of viral nucleoprotein (NP) and polymerase subunit PB2 expression in Western blot and immunofluorescence assays. In addition, licoflavone B maintained broad-spectrum antiviral activity against multiple influenza strains, including H1N1 (A/Puerto Rico/8/34), H3N2 (A/Darwin/9/2021), and a clinical influenza B isolate (B/Beijing/ZYY-B18/2018). These findings position licoflavone B as a promising lead compound for developing next-generation, broad-spectrum antiviral therapies against influenza and potentially other viruses. Full article

Rice planthoppers are the most destructive pests of rice production and the vectors of rice viruses. Fenmezoditiaz as a novel mesoionic insecticide is used for rice planthopper management by targeting the insect’s neural nicotinic acetylcholine receptor. This study aimed to evaluate the effects of fenmezoditiaz on the acquisition, propagation, and transmission of southern rice black-streaked dwarf virus (SRBSDV) by the white-backed planthopper, Sogatella furcifera (Hemiptera: Delphacida). The results revealed that sublethal concentrations of fenmezoditiaz significantly impaired SRBSDV acquisition and viral replication in S. furcifera. Fenmezoditiaz-treated viruliferous S. furcifera exhibited a lower transmission efficiency of SRBSDV to un-infected rice seedlings. Electrical penetration graph (EPG) recordings revealed prolonged non-probing (NP), salivary secretion (N2/N3), and xylem feeding (N5) durations, alongside shortened phloem contact behavior (N4a/N4b), of fenmezoditiaz-treated individuals, indicating disrupted feeding behaviors, which are critical for reducing viral infection. By reducing viral titers and interfering with phloem ingestion, fenmezoditiaz significantly suppresses SRBSDV transmission. These findings revealed fenmezoditiaz’s dual role in pest control and viral transmission blockage, providing a foundation for incorporation into integrated management of vector-borne plant viruses. Full article

Pseudorabies virus (PRV), a highly pathogenic alphaherpesvirus, poses a potential threat to public health and safety due to its broad host range and risk of cross-species transmission. Viruses have evolved multiple strategies to exploit host factors for entry into and survival in host cells. Drebrin is an actin-binding protein that restricts rotavirus entry by inhibiting dynamin-mediated endocytosis. However, its role and mechanism in DNA virus infection, particularly in herpesviruses, remain unexplored. In this study, we investigated the role of Drebrin in PRV infection using pharmacological inhibition (BTP−2) and CRISPR-Cas9-mediated gene knockout. Both the Drebrin inhibitor BTP−2 and gene knockout significantly suppressed PRV replication. Intriguingly, Drebrin exhibited stage-specific effects on the viral life cycle: its inhibition enhanced viral internalization during early infection but impaired viral replication at later stages, suggesting that Drebrin plays a complex role in the regulation of PRV infection. PRV infection partially disrupted actin stress fibers and caused an increase in cell size. Drebrin knockout also altered the host-cell morphology, reduced the cell surface area, and induced actin cytoskeleton rearrangement, which was further modulated in PRV-infected cells. In summary, our data demonstrate that Drebrin functions as a critical host factor governing the entire PRV life cycle by regulating actin cytoskeleton reorganization. Full article

Norovirus–bacterial interactions influence viral replication and immune responses, yet the molecular details that mediate binding of these viruses to commensal bacteria are unknown. Studies with other enteric viruses have revealed that LPS and other lipid/carbohydrate structures facilitate virus–bacterial interactions, and it has also been shown that human noroviruses (HuNoVs) can interact with histo-blood group antigen (HBGA)-like compounds on the surface of bacterial cells. Based on these findings, this study hypothesized that carbohydrate-based compounds were the ligands that facilitated binding of both human and murine noroviruses (MNV) to bacteria. Using glycan microarrays, competitive inhibition assays, and a panel of bacterial mutants, the project assessed the influence of specific glycans on viral attachment to bacteria. Protein-based interactions were also examined. The results supported previous work which demonstrated that HuNoVs strongly bind HBGA-like glycans, while MNV displayed distinct binding to other glycans including aminoglycosides and fucosylated structures. Ultimately, this work demonstrates that HuNoVs have more limited binding requirements for bacterial attachment compared to MNV, and the MNV binding to bacteria may involve both specific structures as well as electrostatic interactions. Given the importance of commensal bacteria during viral infection, defining the molecular mechanisms that mediate virus–bacteria interactions is critical for understanding infection dynamics and may be useful in the development of disease therapeutics and novel technologies for viral detection from food and environmental sources. Full article

Acute human alpha-herpesvirus 1 (HSV-1) infection culminates in a latent infection of neurons in trigeminal ganglia (TG) and the central nervous system. Following infection of mucosal epithelial cells, certain neurons survive infection and life-long latency is established. Periodically, stressful stimuli trigger reactivation from latency, which result in virus shedding, transmission to other people, and, occasionally, recurrent disease. The glucocorticoid receptor (GR) and Krüppel-like factor 15 (KLF15) comprise a feed-forward transcriptional loop that cooperatively transactivate key HSV-1 promoters that drive expression of infected cell protein 0 (ICP0), ICP4, and ICP27. Silencing KLF15 significantly reduces HSV-1 replication in cultured mouse neuroblastoma cells. Consequently, we hypothesized that KLF15 mediates certain aspects of reactivation from latency. To test this hypothesis, we compared HSV-1 replication in KLF15^−/− mice versus wild-type (wt) parental C57BL/6 mice. Virus shedding during acute infection was reduced in KLF15^−/− mice. Male KLF15^−/− mice shed higher titers of virus during late stages of reactivation from latency compared to KLF15^−/− females and wt mice regardless of sex. At 15 d after explant-induced reactivation, virus shedding was higher in male KLF15^−/− mice relative to wt mice and female KLF15^−/− mice. These studies confirm KLF15 expression enhances viral replication during acute infection and reactivation from latency. Full article

Epstein-Barr Virus (EBV) is a causative agent of infectious mononucleosis and is strongly associated with Burkitt lymphoma, Hodgkin lymphoma, and nasopharyngeal carcinoma. EBV encodes a deubiquitinating enzyme, BPLF1, which is important for infectious virus production, B-cell immortalization, and tumorigenesis. To elucidate BPLF1’s role, an affinity-based mass spectrometry screen was performed, which suggested that BPLF1 and mTOR interact. mTOR, a critical mediator within cellular signaling cascades and oncogenesis, exists in two distinct complexes: mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2). Here, we show that BPLF1 has direct deubiquitinating (DUB) activity on mTOR, removing both K48- and K63-ubiquitin linkages. Additionally, WT BPLF1 decreased mTORC1 localization to the lysosome and decreased the phosphorylation of mTORC1 downstream effectors, 4E-BP1 and S6K1. BPLF1 also had DUB activity on Raptor and Rictor, which have both been shown to preferentially cause the formation of mTORC2 over mTORC1 when not ubiquitinated. Immunoprecipitation of mTOR shows decreased mTORC1 formation in the presence of WT BPLF1. Importantly, treatment with rapamycin, an mTORC1 inhibitor, increased infectious virus production, while JR-AB2-011, an mTORC2 inhibitor, reduced infectious virus production. Taken together, these data demonstrate that BPLF1’s effect on the mTOR signaling cascade regulates cellular and viral processes during EBV infectivity and replication. Full article

There is a need for safe and effective vaccines against the Venezuelan equine encephalitis virus that infects both humans and equines. However, development of a live-attenuated vaccine using the TC-83 strain has been hampered by substantial reactogenicity and the potential for neuroinvasion. In this study, we demonstrate that V4020, a new TC-83-based investigational VEEV vaccine with redundant safety features preventing neuroinvasion and reversion, exhibited no neuroinvasion potential in a murine model. Following subcutaneous or intramuscular administration, a subset of mice that received the TC-83 vaccine succumbed to central nervous system infection, with replicating virus detected in the CNS, demonstrating a low, yet detectable neuroinvasion potential of the TC-83 vaccine in vivo. Sequencing analysis of the TC-83 virus recovered from the brains identified a pseudoreversion of E2 R120I, as E2 R120 is known to confer attenuation for TC-83. In contrast, V4020 showed no evidence of virus in the CNS, highlighting one of the V4020 features, a new synonymous codon to minimize reversion to the wild-type residue. Overall, our study establishes V4020 as a rationally designed, safe vaccine candidate for VEEV with significantly reduced neuroinvasion risk. Full article

Oncolytic herpes simplex virus (oHSV) is a promising cancer immunotherapy that induces tumor cell lysis and stimulates anti-tumor immunity. Our previous single-cell RNA sequencing analysis of oHSV-treated medulloblastoma tumors revealed expansion and activation of tumor-infiltrating dendritic cells (DCs), and direct oHSV infection of DCs within the brain. While the therapeutic effects of oHSVs have been primarily attributed to tumor cell infection, we hypothesize that direct infection of DCs also contributes to therapeutic efficacy by promoting DC maturation and immune activation. Although the oHSV infection in DCs was abortive, it led to increased expression of major histocompatibility complex (MHC) class I/II and co-stimulatory molecules. oHSV-infected DCs activated naïve CD4⁺ and CD8⁺ T cells, inducing expression of CD69 and CD25. These primed T cells exhibited enhanced cytotoxicity against CT-2A glioma cells. Adoptive transfer of oHSV-infected DCs via subcutaneous injection near inguinal lymph nodes delayed tumor growth in a syngeneic CT-2A glioma model, independent of tumor viral replication and lysis. Mechanistically, our in vitro studies demonstrate that oHSV can directly infect and functionally activate DCs, enabling them to prime effective anti-tumor T cell responses. This study highlights the anti-tumor potential of leveraging oHSV-infected DCs to augment viroimmunotherapy as a cancer therapeutic. Full article

Obesity affects millions of individuals globally, and a deeper understanding of its associated physiological disturbances is essential for addressing key public health concerns. It has been demonstrated that the influenza virus possesses substantial global epidemic potential, with higher incidence rates observed in obese individuals and prolonged recovery times. Obese individuals exhibit impaired immune organ function, decreased immune cell activity, disrupted metabolism characterized by mitochondrial dysfunction, and an imbalance in gut microbiota associated with intestinal mucosal barrier damage. The gut microbiota and their metabolic composition in obese patients differ from those in non-obese individuals, potentially promoting viral replication and exacerbating disease severity. These factors collectively contribute to more severe tissue damage and heightened immune responses in obese patients during influenza infection. Therefore, understanding the impact of obesity on influenza virus infection dynamics enables the development of strategies promoting healthy lifestyles to manage body weight and enhance immunity against viral infections. Additionally, given that this special population may not respond optimally to antimicrobial drugs and vaccination, it is necessary to consider how treatment strategies for this group are managed. This review illustrates findings concerning the impact of obesity on the immune response to influenza virus infection, including potential underlying mechanisms. Full article

The molecular basis for the distinct intestinal tropism of infectious bronchitis virus (IBV) strains remains poorly understood. This study identifies the S2 subunit of the spike glycoprotein as the critical determinant conferring duodenal tropism to the IBV CSL strain. Comparative pathogenesis in specific-pathogen-free (SPF) chicks revealed that the CSL strain achieved significantly higher viral titers in the duodenum compared to strains D90, PYG QX1, and XXX QX5. This duodenal replication was associated with severe epithelial inflammation, characterized by upregulation of pro-inflammatory cytokines (IL-6, IL-17A, IL-22, TNF-α, IFN-β, IFN-γ) and disruption of barrier integrity via downregulation of tight junction proteins (Occludin, Claudin-1, ZO-1). Crucially, reverse genetics using the non-enterotropic D90 backbone demonstrated that recombinant viruses carrying the CSL-S2 gene (rD90-ΔS/CSL and rD90-ΔS2/CSL), but not those carrying CSL-S1 (rD90-ΔS1/CSL), replicated efficiently and induced inflammation in the duodenum, phenocopying wild-type CSL. In contrast, renal tropism was independent of the S2 subunit. These findings establish the S2 subunit as both necessary and sufficient for IBV duodenal tropism, uncoupling it from renal pathogenicity. This identifies S2 as a prime molecular target for developing next-generation vaccines against intestinal IBV pathotypes. Full article

Human DEAD-box helicase 3 (DDX3) is a multifunctional RNA helicase implicated in mRNA unwinding and the regulation of gene expression. While DDX3 has been extensively studied in the context of RNA virus replication, its role in DNA virus replication remains less understood. In this study, we explore the involvement of DDX3 in the life cycle of Herpes Simplex Virus type 2 (HSV-2), a double-stranded DNA virus. Silencing of DDX3 expression with siRNA significantly impaired HSV-2 replication, indicating that DDX3 supports viral propagation. Unexpectedly, HSV-2 infection led to a marked reduction in cellular DDX3 protein levels during in vitro replication in human cells, particularly at 24 h post-infection, corresponding to the peak of viral production. Notably, this decrease was not accompanied by a reduction in DDX3 mRNA levels, nor was it prevented by proteasome inhibition, suggesting an alternative mechanism of DDX3 depletion. Further analysis revealed substantial amounts of DDX3 protein within HSV-2 virions, supporting the hypothesis that DDX3 is packaged into viral particles during replication. We propose that HSV-2 exploits host DDX3 by incorporating it into progeny virions to facilitate early stages of infection in newly infected cells. However, no evidence linking DDX3 to the assembly process of HSV-2 particles was found. These findings expand the known functional repertoire of DDX3 and highlight its potential as a host factor co-opted by DNA viruses, suggesting a broader relevance in antiviral strategies. Full article