Search Results (3,011)

In this study, astaxanthin, which has previously been shown to have antiviral effects, was examined for its dose-dependent potency to inhibit cellular SARS-CoV-2 infections. Naturally occurring astaxanthin is obtained and orally administered as ASX-oleoresin, a composition of different astaxanthin fatty acid esters. We therefore hypothesized that the compound’s beneficial effects are not only related to astaxanthin. Thus, a “green” algae extract (i.e., poor astaxanthin content < 0.2%; ASX^p) of the microalgae Haematococcus pluvialis, as well as an astaxanthin-rich algae extract (astaxanthin content = 20%; ASX^r), were tested in in vitro cellular viral infection assays. Thereby, it was found that both extracts reduced viral infections significantly. As a potential mode of inhibitory action, the binding of ASX-oleoresin to the viral spike protein was investigated by isothermal fluorescence titration, revealing binding affinities of Kd = 1.05 µM for ASX^r and Kd = 1.42 µM for ASX^p. Based on our data, we conclude that several ASX-oleoresin fractions from H. pluvialis exhibit antiviral activity, which extends beyond the known antioxidant activity of astaxanthin. From a molecular dynamic simulation of ASX-oleoresin, fatty acid domains could be considered as activity-chaperoning factors of ASX. Therefore, microalgae biomass should be considered in the future for further antiviral activities. Full article

The apoplast is often the first point of contact between plant cells and invading pathogens, serving as an important site for defense signaling. Pokeweed antiviral protein (PAP), a ribosome-inactivating protein from Phytolacca americana (pokeweed), is localized to the apoplast and is hypothesized to accompany a pathogen to the cytosol, where it would inactivate host ribosomes to prevent pathogen spread. However, it is not known whether PAP interacts with other proteins in the apoplast. In this study, we identified Phytolacca americana cysteine protease 1 (PaCP1), an extracellular cysteine protease, as a novel PAP interactor. Sequence and structural analyses classified PaCP1 as a member of the C1A subfamily of papain-like cysteine proteases. Immunoprecipitation, mass spectrometry, and yeast two-hybrid analysis showed that PAP specifically binds the mature, active form of PaCP1. Curiously, PaCP1 cleaves PAP at its N- and C-termini, generating peptides that enhance MAPK phosphorylation in pokeweed leaves, indicating their potential role in stress signaling. PaCP1 processing of PAP to generate bioactive peptides diversifies the function of a ribosome-inactivating protein beyond its canonical inhibition of translation. Our findings present a novel extracellular role for PAP and advance our understanding of how protein interactions in the apoplast contribute to plant immune responses. Full article

Conessine is a steroidal alkaloid found in many plants. The pharmacological efficacies of conessine on various ailments, including antiviral effects against Zika, Herpes, and Coronavirus, were reported. However, the effect of conessine on the influenza virus was still unknown. In this study, conessine exhibited a strong inhibitory effect against influenza A virus (IAV) infection. We examined the effect of conessine on IAV using green fluorescent protein (GFP)-expressing Influenza A/PR8/34 and wild-type A/PR8/34. The fluorescence-activated cell sorting, fluorescence microscopy, cytopathic effect analysis, and plaque assay demonstrated that conessine significantly inhibits IAV infection. Consistently, immunofluorescence results showed that conessine strongly reduces the expression of IAV proteins. The time-of-drug-addition assay revealed that conessine could affect the viral attachment and entry into the cells upon IAV infection. Further, conessine eradicated the virus before binding to the cells in the early stage of viral infection. Our results suggest that conessine has strong anti-viral efficacy against IAV infection and could be developed as an anti-influenza viral agent. Full article

Porcine circovirus type 2 (PCV2) is a globally prevalent swine pathogen that induces immunosuppression, predisposing pigs to subclinical infections. In intensive farming systems, PCV2 persistently impairs growth performance and vaccine efficacy, leading to substantial economic losses in the swine industry. Emerging evidence suggests that certain viruses exploit Suppressor of Cytokine Signaling 3 (SOCS3), a key immune checkpoint protein, to subvert host innate immunity by suppressing cytokine signaling. While SOCS3 has been implicated in various viral infections, its regulatory role in PCV2 replication remains undefined. This study aims to elucidate the mechanisms underlying the interplay between SOCS3 and PCV2 during viral pathogenesis. Porcine SOCS3 was amplified using RT-PCR and stably overexpressed in PK-15 cells through lentiviral delivery. Bioinformatics analysis facilitated the design of three siRNA candidates targeting SOCS3. We systematically investigated the effects of SOCS3 overexpression and knockdown on PCV2 replication kinetics and host antiviral responses by quantifying the viral DNA load and the mRNA levels of cytokines. PCV2 infection upregulated SOCS3 expression at both transcriptional and translational levels in PK-15 cells. Functional studies revealed that SOCS3 overexpression markedly enhanced viral replication, whereas its knockdown suppressed viral proliferation. Intriguingly, SOCS3-mediated immune modulation exhibited a divergent regulation of antiviral cytokines: PCV2-infected SOCS3-overexpressing cells showed elevated IFN-β but suppressed TNF-α expressions, whereas SOCS3 silencing conversely downregulated IFN-β while amplifying TNF-α responses. This study unveils a dual role of SOCS3 during subclinical porcine circovirus type 2 (PCV2) infection: it functions as a host-derived pro-viral factor that facilitates viral replication while simultaneously reshaping the cytokine milieu to suppress overt inflammatory responses. These findings provide novel insights into the mechanisms underlying PCV2 immune evasion and persistence and establish a theoretical framework for the development of host-targeted control strategies. Although our results identify SOCS3 as a key host determinant of PCV2 persistence, the precise molecular pathways involved require rigorous experimental validation. Full article

Background/Objectives: Viral respiratory infections have a significant impact on global health and the economy. While vaccines are effective in preventing infection, they might not be available or sufficient when used alone and must be complemented by specific therapeutic strategies. The development of new antiviral agents is increasingly important due to the continual emergence of novel respiratory pathogens. Previously we identified bovine lactoferrin (bLf)-derived tetrapeptides and peptidomimetics that showed potent in vitro activity against the influenza A virus in the picomolar range. Methods: Inspired by these results, in this study, we evaluated the antiviral potential of these compounds against HCoV-229E, a human coronavirus that can cause severe disease in immunocompromised individuals, using a compound repositioning approach. Results: Functional studies revealed that SK(N-Me)HS (3) interferes with viral entry and replication, while compound SNKHS (5) primarily blocks infection in the early stages. Biophysical analyses confirmed the occurrence of high-affinity binding to the viral spike protein, and computational studies suggested that the compounds target a region involved in conformational changes necessary for membrane fusion. Conclusions: These findings highlight these compounds as promising candidates for coronavirus entry inhibition and underscore the value of compound repurposing in antiviral development. Full article

The midgut of Antheraea pernyi plays a critical role in antiviral defense. However, its transcriptional complexity remains poorly understood. Here, a full-length (FL) transcriptome atlas of A. pernyi midgut was developed by integrating PacBio Iso-Seq and RNA-seq techniques. The transcriptome sequences included 1850 novel protein-coding genes, 17,736 novel alternative isoforms, 1664 novel long non-coding RNAs (lncRNAs), and 858 transcription factors (TFs). In addition, 2471 alternative splicing (AS) events and 3070 alternative polyadenylation (APA) sites were identified. Moreover, 3426 and 4796 differentially expressed genes (DEGs) and isoforms were identified after ApNPV infection, respectively, besides the differentially expressed lncRNAs (164), TFs (171), and novel isoforms of ApRelish (1) and ApSOCS2 (4). Enrichment analyses showed that KEGG pathways related to metabolism were suppressed, whereas GO terms related to DNA synthesis and replication were induced. Furthermore, the autophagy and apoptosis pathways were significantly enriched among the upregulated genes. Protein–protein interaction network (PPI) analysis revealed the coordinated downregulation of genes involved in mitochondrial ribosomes, V-type and F-type ATPases, and oxidative phosphorylation, indicating the disruption of host energy metabolism and organelle acidification. Moreover, coordinated upregulation of genes associated with cytoplasmic ribosomes was observed, suggesting that the infection by ApNPV interferes with host translational machinery. These results show that ApNPV infection reprograms energy metabolism, biosynthetic processes, and immune response in A. pernyi midgut. Our study provides a foundation for elucidating the mechanisms of A. pernyi–virus interactions, particularly how the viruses affect host defense strategies. Full article

Recent outbreaks of highly pathogenic human RNA viruses from probable zoonotic origin have highlighted the relevance of epidemic preparedness as a society. However, research in vaccinology and virology, as well as epidemiologic surveillance, is often constrained by the biological risk that live virus experimentation entails. These also involve expensive costs, time-consuming procedures, and advanced personnel expertise, hampering market access for many drugs. Most of these drawbacks can be circumvented with the use of pseudotyped viruses, which are surrogate, non-pathogenic recombinant viral particles bearing the surface envelope protein of a virus of interest. Pseudotyped viruses significantly expand the research potential in virology, enabling the study of non-culturable or highly infectious pathogens in a safer environment. Most are derived from lentiviral vectors, which confer a series of advantages due to their superior efficiency. During the past decade, many studies employing pseudotyped viruses have evaluated the efficacy of vaccines or monoclonal antibodies for relevant pathogens such as HIV-1, Ebolavirus, Influenza virus, or SARS-CoV-2. In this review, we aim to provide an overview of the applications of pseudotyped viruses when evaluating the neutralization capacity of exposed individuals, or candidate vaccines and antivirals in both preclinical models and clinical trials, to further help develop effective countermeasures against emerging neutralization-escape phenotypes. Full article

The expanding distribution and geographic range of mosquitoes have potentially contributed to increased flaviviral dissemination and transmission. Despite the growing burden of flaviviral infections, there are no effective antiviral treatments or vaccines, highlighting the need for novel therapeutic targets. Tetraspanins, a superfamily of transmembrane domain glycoproteins involved in cellular organization, signaling, and protein–protein interactions have been recognized as potential mediators of flaviviral infection and transmission. While their roles in vertebrate hosts have been explored, their involvement in flaviviral replication and dissemination within medically important vectors remains poorly understood. In this study, we investigated the role of arthropod tetraspanins in mosquito cells and extracellular vesicles (EVs) derived from cells infected with Zika virus (ZIKV) and dengue virus (serotype 2; DENV2). Among several of the tetraspanins analyzed, only CD151 was significantly upregulated in both mosquito cells and in EVs derived from ZIKV/DENV2-infected cells. RNAi-mediated silencing of CD151 led to a marked reduction in viral burden, suggesting its crucial role in flavivirus replication. Inhibition of EV biogenesis using GW4869 further demonstrated that EV-mediated viral transmission contributes to flavivirus propagation. Additionally, co-immunoprecipitation and immunofluorescence analyses revealed direct interactions between CD151 and ZIKV NS2B and DENV2 capsid proteins. Overall, our findings highlight the functional importance of mosquito CD151 in the replication and transmission of ZIKV and DENV2. This study provides new insights into the molecular mechanisms of flaviviral infection in mosquitoes and suggests that targeting vector tetraspanins may offer a potential approach to controlling mosquito-borne flaviviruses. Full article

The innate immune response is an important defense against invading pathogens. Stimulator of interferon gene (STING) plays an important role in the cyclic GMP-AMP synthase (cGAS)-mediated activation of type I IFN responses. However, some viruses have evolved the ability to inhibit the function of STING and evade the host antiviral defenses. Understanding both the mechanism of action and the viruses targets of STING effector is important because of their importance to evade the host antiviral defenses. In this study, the STING (IpSTING) of Ictalurus punctatus was first identified and characterized. Subsequently, the yeast two-hybrid system (Y2HS) was used to screen for proteins from channel catfish virus (CCV, Ictalurid herpesvirus 1) that interact with IpSTING. The ORFs of the CCV were cloned into the pGBKT7 vector and expressed in the AH109 yeast strain. The bait protein expression was validated by autoactivation, and toxicity investigation compared with control (AH109 yeast strain transformed with empty pGBKT7 and pGADT7 vector). Two positive candidate proteins, ORF41 and ORF65, were identified through Y2HS screening as interacting with IpSTING. Their interactions were further validated using co-immunoprecipitation (Co-IP). This represented the first identification of interactions between IpSTING and the CCV proteins ORF41 and ORF65. The data advanced our understanding of the functions of ORF41 and ORF65 and suggested that they might contribute to the evasion of host antiviral defenses. However, the interaction mechanism between IpSTING, and CCV proteins ORF41 and ORF65 still needs to be further explored. Full article

Artificial intelligence (AI) techniques—ranging from hybrid mechanistic–machine learning (ML) ensembles to gradient-boosted decision trees, support-vector machines, and deep neural networks—are transforming the management of seasonal influenza, respiratory syncytial virus (RSV), human immunodeficiency virus (HIV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Symptom-based triage models using eXtreme Gradient Boosting (XGBoost) and Random Forests, as well as imaging classifiers built on convolutional neural networks (CNNs), have improved diagnostic accuracy across respiratory infections. Transformer-based architectures and social media surveillance pipelines have enabled real-time monitoring of COVID-19. In HIV research, support-vector machines (SVMs), logistic regression, and deep neural network (DNN) frameworks advance viral-protein classification and drug-resistance mapping, accelerating antiviral and vaccine discovery. Despite these successes, persistent challenges remain—data heterogeneity, limited model interpretability, hallucinations in large language models (LLMs), and infrastructure gaps in low-resource settings. We recommend standardized open-access data pipelines and integration of explainable-AI methodologies to ensure safe, equitable deployment of AI-driven interventions in future viral-outbreak responses. Full article

Background: Influenza A viruses (IAV) cause seasonal flu and occasional pandemics. In addition, the potential for the emergence of new strains presents unknown challenges for public health. Face masks and other personal protective equipment (PPE) can act as barriers that prevent the spread of these viruses. Metal ions embedded into PPE have been demonstrated to inactivate respiratory viruses, but the underlying mechanism of inactivation and potential for resistance is presently not well understood. Methods: In this study, we used hemagglutination assays to quantify the effect of zinc ions on IAV sialic acid receptor binding. We varied the zinc concentration, incubation time, incubation temperature, and passaged IAV in the presence of zinc ions to investigate if resistance to zinc ions could evolve. Results: We found that zinc ions impact the ability of IAV particles to hemagglutinate and observed inhibition within 1 min of exposure. Maximum inhibition was achieved within 1 h and sustained for at least 24 h in a concentration-dependent manner. Inhibition was also temperature-dependent, and optimal above room temperature. Serial passaging of IAV in the presence of zinc ions did not result in resistance. Conclusions: e conclude that zinc ions prevent IAV hemagglutination in a concentration and temperature-dependent manner for at least 24 h. Overall, these findings are in line with previous observations indicating that zinc-embedded materials can inactivate the IAV hemagglutinin and SARS-CoV-2 spike proteins, and they support work toward developing robust, passive, self-cleaning antiviral barriers in PPE. Full article

Porcine Rotavirus (PoRV), a predominant causative agent of neonatal diarrhea in piglets, shares substantial genetic homology with human rotavirus and represents a considerable threat to both public health and the global swine industry in the absence of specific antiviral interventions. The VP6 protein, an internal capsid component, is characterized by exceptional sequence conservation and robust immunogenicity, rendering it an ideal candidate for viral genotyping and vaccine development. In the present study, the recombinant plasmid pET28a(+)-VP6 was engineered to facilitate the high-yield expression and purification of the VP6 antigen. BALB/c mice were immunized to generate monoclonal antibodies (mAbs) through hybridoma technology, and the antigenic specificity of the resulting mAbs was stringently validated. Subsequently, a panel of truncated protein constructs was designed to precisely map linear B-cell epitopes, followed by comparative conservation analysis across diverse PoRV strains. Functional validation demonstrated that all three mAbs exhibited high-affinity binding to VP6, with a peak detection titer of 1:3,000,000 and exclusive specificity toward PoRVA. These antibodies effectively recognized representative genotypes such as G3 and X1, while exhibiting no cross-reactivity with unrelated viral pathogens; however, their reactivity against other PoRV serogroups (e.g., types B and C) remains to be further elucidated. Epitope mapping identified two novel linear B-cell epitopes, ¹²⁸YIKNWNLQNR¹³⁷ and ¹³⁸RQRTGFVFHK¹⁴⁷, both displaying strong sequence conservation among circulating PoRV strains. Collectively, these findings provide a rigorous experimental framework for the functional dissection of VP6 and reinforce its potential as a valuable diagnostic and immunoprophylactic target in PoRV control strategies. Full article

Background: Protein kinase R (PKR) inhibits general mRNA translation by phosphorylating the alpha subunit of eukaryotic translation initiation factor 2 (eIF2). PKR also modulates NF-κB signaling during viral infections, but comparative studies of PKR-mediated NF-κB responses across mammalian species and their regulation by viral inhibitors remain largely unexplored. This study aimed to characterize the conserved antiviral and inflammatory roles of mammalian PKR orthologs and investigate their modulation by poxviral inhibitors. Methods: Using reporter gene assays and quantitative RT-PCR, we assessed the impact of 17 mammalian PKR orthologs on general translation inhibition, stress-responsive translation, and NF-κB-dependent induction of target genes. Congenic human and rabbit cell lines infected with a myxoma virus strain lacking PKR inhibitors were used to compare the effects of human and rabbit PKR on viral replication and inflammatory responses. Site-directed mutagenesis was employed to determine key residues responsible for differential sensitivity to the viral inhibitor M156. Results: All 17 mammalian PKR orthologs significantly inhibited general translation, strongly activated stress-responsive ATF4 translation, and robustly induced NF-κB target genes. Inhibition of these responses was specifically mediated by poxviral K3 orthologs that effectively suppressed PKR activation. Comparative analyses showed human and rabbit PKRs similarly inhibited virus replication and induced cytokine transcripts. Amino acid swaps between rabbit PKRs reversed their sensitivity to viral inhibitor M156 and NF-κB activation. Conclusions: Our data show that the tested PKR orthologs exhibit conserved dual antiviral and inflammatory regulatory roles, which can be antagonized by poxviral K3 orthologs that exploit eIF2α mimicry to modulate the PKR-NF-κB axis. Full article

Nucleocytoplasmic trafficking is a highly regulated process that allows the cell to control the partitioning of proteins and nucleic acids between the cytosolic and nuclear compartments. The Ebola virus minor matrix protein VP24 (eVP24) hijacks this process by binding to a region on the NPI-1 subfamily of karyopherin alpha (KPNA) nuclear importers. This region overlaps with the activated transcription factor STAT1 binding site on KPNAs, preventing STAT1 nuclear localization and activation of antiviral gene transcription. However, the molecular interactions of eVP24-KPNA5 binding that lead to the nuclear localization of eVP24 remain poorly characterized. Here, we show that trafficking of eVP24 into the nucleus by KPNA5 requires simultaneous binding of cargo. We also describe the conformational dynamics of KPNA5 and interactions with eVP24 and cargo nuclear localization sequences (NLS) using biophysical approaches. Our results reveal that eVP24 binding to KPNA5 does not impact cargo NLS binding to KPNA5, indicating that simultaneous binding of both cellular cargo and eVP24 to KPNA5 is likely required for nuclear trafficking. Together, these results provide a biophysical basis for how Ebola virus VP24 protein gains access to the nucleus during Ebola virus infection. Full article

The vast majority of viruses causing human and animal diseases are enveloped—their virions contain an outer lipid bilayer originating from a host cell. Small molecule antivirals targeting the lipid bilayer cover the broadest spectrum of viruses. In this context, we consider the chemical nature and mechanisms of action of membrane-targeting antivirals. They can affect virions by (1) physically modulating membrane properties to inhibit fusion of the viral envelope with the cell membrane, (2) physically affecting envelope lipids and proteins leading to membrane damage, pore formation and lysis, (3) causing photochemical damage of unsaturated membrane lipids resulting in integrity loss and fusion arrest. Other membrane-active compounds can target host cell membranes involved in virion’s maturation, coating, and egress (endoplasmic reticulum, Golgi apparatus, and outer membrane) affecting these last stages of viral reproduction. Both virion- and host-targeting membrane-active molecules are promising concepts for broad-spectrum antivirals. A panel of approved antivirals would be a superior weapon to respond to and control emerging disease outbreaks caused by new viral strains and variants. Full article