Search Results (847)

Hepatitis E virus (HEV) infection is generally self-limiting in immunocompetent individuals but may progress to chronic infection in immunocompromised patients, underscoring the need for effective antiviral therapies. Although ribavirin is currently used off-label for HEV treatment, its associated adverse effects highlight the need for safer alternatives. In this study, we screened an anti-viral compound library comprising 800 compounds using three HEV reporter systems designed to target distinct stages of the viral life cycle. Candidate compounds were further evaluated in PLC/PRF/5 cells using both acute and chronic infection models with wild-type genotype 3 HEV (HEV-3). Antiviral activity was assessed by measuring HEV RNA levels in culture supernatants. Elbasvir, a known inhibitor of hepatitis C virus (HCV) non-structural protein 5A (NS5A), was identified as the most potent candidate. Although multiple compounds showed inhibitory effects in reporter assays, only elbasvir achieved sustained suppression of HEV growth in long-term culture, reducing HEV RNA levels to below the limit of detection. In a chronic infection co-culture model, elbasvir maintained antiviral activity at non-cytotoxic concentrations. Time-of-addition analysis demonstrated that elbasvir inhibits an early step in the viral life cycle, specifically viral internalization. Furthermore, combination with ribavirin enhanced antiviral efficacy, resulting in sustained viral suppression without detectable cytotoxicity and exhibiting an additive interaction. Collectively, these findings identify elbasvir as a promising candidate for repurposing as an anti-HEV drug and support a combination strategy targeting distinct steps of the viral life cycle. Full article

The SARS-CoV-2 non-structural proteome remains the most clinically validated and strategically important landscape for direct-acting small-molecule antiviral drug discovery. The success of inhibitors targeting the main protease (M^pro, Nsp5) and RNA-dependent RNA polymerase (RdRp, Nsp12) has firmly established viral replication enzymes as tractable, druggable, and therapeutically relevant targets, while setting clear benchmarks for translational antiviral development. Building on this foundation, a second wave of non-structural protein (Nsp) targets has emerged with increasing translational promise, including the papain-like protease (PL^pro), the bifunctional Nsp14 proofreading and capping machinery, Nsp16 2′-O-methyltransferase, Nsp13 helicase, and Nsp15 endoribonuclease. In parallel, additional components such as Nsp1 and the Mac1 domain of Nsp3 continue to expand the antiviral design space, although they remain at earlier stages of chemical validation. In this review, we comprehensively assess SARS-CoV-2 non-structural proteins through a medicinal chemistry and translational lens, with an emphasis on structural tractability, mechanism of action, quality of chemical matter, cellular and in vivo antiviral evidence, evolutionary conservation, resistance liabilities, and developability. Particular attention is given to the features that distinguish tool compounds from genuinely actionable leads and to the opportunities for rational combination regimens that extend beyond first-generation protease- and polymerase-centred therapy. Collectively, the non-structural proteome offers the strongest foundation for next-generation and potentially broader-spectrum coronavirus antivirals with improved resilience to viral evolution. Full article

PPV5 NS1 is a nonstructural and multifunctional protein comprising helicase and nuclease domains. The helicase domain contains conserved motifs from superfamily 3 helicases, including Walker A, Walker B, Motif B’, Motif C, and Box VII, whereas the nuclease domain consists of glutamate, a HUH motif, lysine, and tyrosine. In Mexico, the reported prevalence of PPV5 is higher than in other countries, with notable amino acid differences compared with pathogenic PPVs. This study compares the helicase and nuclease domains from a full-length PPV5 NS1 sequence with porcine parvovirus 1 (PPV1) and canine parvovirus (CPV) to characterize the protein further and perform three-dimensional (3D) modeling using bioinformatic tools, including solvent-accessible surface area (SASA) and electrostatic potential assessments. The main findings highlight the ATP-binding pocket, showing electrostatic values in PPV5 that contrast with PPV1 and CPV. The electrostatic potential 3D models suggest those differences involve non-conserved regions. In particular, the PPV5 Box VII surface is predominantly negative due to a glutamate substitution at position 7. In the nuclease domain, the interaction with Mg²⁺ differs between PPV5 and pathogenic PPV. The electrostatic findings suggest that these differences may have functional implications for both domains, but confirmation must be completed with functional assays. Full article

Background/Objectives: Serial passage in embryonated eggs is widely used to attenuate the infectious bronchitis virus (IBV) for vaccine production; however, the evolutionary processes underlying attenuation and immunogenicity remain incompletely understood. Here, we analyzed genome-wide viral evolution during serial passages to investigate how mutations emerge, persist, are lost, or become fixed over time and how these dynamics relate to changes in pathogenicity and immunogenicity. Methods: Deep sequencing was performed on 11 representative serial passages (P2–P79) of the UY/11/CA/18 strain, including two derivative lineages: P7 VIR (virulent) and P53 VAC (attenuated and immunogenic). Results: This study identified an early adaptive phase characterized by a limited set of mutations potentially associated with genome replication, viral RNA processing, and virion assembly, including a key change in non-structural protein 14 and variants in M and 3c (E). This phase was followed by a broader expansion of the variant spectrum across replicase genes and delayed accumulation of Spike protein variants. Most Spike changes emerged during later passages and exhibited transient dynamics, and only a subset reached a high frequency after the establishment of early replicase- and structural-associated changes. Consistent with these dynamics, P7 VIR diverged before the late accumulation of Spike variants and retained a pathogenic phenotype, whereas P53 VAC diverged after the emergence of early high-frequency variants but before the extensive late-stage Spike variation observed in P79, which was associated with reduced immunogenicity. Conclusions: These findings support a multi-step model of IBV attenuation in which progressive filtering of genome-wide variation shapes distinct evolutionary outcomes during serial passages. This evolutionary framework provides insight into the relationship between attenuation and immunogenicity and may help guide the rational design of live attenuated vaccines. Full article

In this review, we examine the occurrence of two independent, single recombination events which occurred between human enteroviruses (Picornaviridae, Enterovirus, Enterovirus betacoxsackie). These recombination events contributed to the emergence of two viruses which adapted to pigs. These viruses have caused epizootics of swine vesicular disease (SVD) for many years. As was shown previously, the classical SVD virus (SVDV-1) originated from human coxsackievirus B5. The strain T75 (SVDV-2) emerged from human coxsackievirus B4 in the Tambov region of Russia, where it circulated from 1975 to 1977. A high percentage of similarity between both types of the SVD virus was found in the 3D protein coding region (88%). In our previous work, analysis of the VP1 gene dates the appearance of the SVDV-2 precursor to between 1954 and 1975. In this work, the origin of the genome region encoding non-structural proteins was analyzed and is believed to be a result of multiple recombination events between human enteroviruses (hypothetically, E1, E9, E11 and coxsackievirus A9). The recombination breakpoint between the region of structural CVB4 proteins and non-structural T75 proteins is located in region 2A. This mini-review also represents the historical research of SVDV-1 and SVDV-2 strains (O72(USS/6/72) and T75, respectively) isolated in the former Soviet Union. Full article

Bovine viral diarrhea virus (BVDV), a significant global pathogen threatening cattle industries worldwide, presents substantial challenges for disease control. Its ability to infect cattle across all age groups, coupled with incompletely understood transmission mechanisms, complicates prevention and treatment strategies. We previously reported that BVDV induced tunneling nanotubes (TNTs)—F-actin-rich cytoplasmic connections between adjacent cells—and utilizes these structures for intercellular transmission. In this study, we used lentiviral transfection to express various structural and non-structural proteins of BVDV and identified NS5A as a critical viral protein that induces the formation of TNTs. RNA-seq analysis revealed that CKAP2, a host protein, plays a key role in TNT generation, with the PI3K/AKT/mTOR signaling pathway being essential for this process. Further investigation demonstrated that CKAP2 interacts with BVDV NS5A, triggering the activation of the PI3K/AKT/mTOR pathway, thereby promoting TNT formation and enhancing viral dissemination. Our data highlight a previously unknown mechanism of BVDV spreading and replication, which could have significant implications for within-host spread and immune evasion. Full article

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has greatly impacted public health due to high rates of transmissibility and mutation during the COVID-19 pandemic. Macrodomain 1 (Mac1) of non-structural protein 3 remained well conserved across variants and is critical to suppression of host immune response to infection, making Mac1 a promising target for therapeutic development. Mac1 binds and cleaves the post-translational modification ADP-ribose and is hypothesized to have a downstream effect on the host interferon response, but the exact cellular targets of Mac1 are still unknown. Characterizing the substrates of Mac1 ADP-ribosyl hydrolase activity using a catalytically inactive mutant N40D can reveal critical virus–host interactions to identify protein targets of Mac1 and reveal mechanisms of host interferon suppression. Here, we performed affinity enrichment with WT Mac1 and Mac1 N40D in HEK293T and A549 cells and quantified changes in protein interactions by TMT-multiplexed tandem mass spectrometry. We identified interactions between Mac1 and ADP-ribosylated substrates involved in DNA damage response, cytoskeletal components, and cell cycle regulation. Additionally, several members of the TRiC complex involved in protein folding were selectively enriched with mutant Mac1 from A549 cells. These findings suggest a novel role of Mac1 in regulating host protein folding. Full article

The Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) has evolved sophisticated immune-evasion strategies to establish a productive infection in the host, primarily by counteracting the innate antiviral response. Here, we demonstrate for the first time that the PRRSV non-structural protein NSP8 suppresses NF-κB-dependent antiviral signalling by hijacking the host ubiquitin-conjugating enzyme UBE2K and inducing the degradation of IKKα, a pivotal kinase in the NF-κB pathway. PRRSV infection led to significant upregulation of host UBE2K, which in turn facilitated viral replication. Mechanistically, we found that NSP8 interacts directly with IKKα, triggering its degradation by the proteasome. Furthermore, we revealed that this process was facilitated by the host protein UBE2K, which acted as a crucial cofactor by directly interacting with NSP8 and thereby enhancing its activity against IKKα. This disruption blocked the activation of the NF-κB pathway and suppressed the expression of downstream antiviral factors, such as TNF-α, IL-6 and IFN-β, ultimately facilitating PRRSV replication. All of these findings showed that NSP8 is an important part of the process by which the host NF-κB pathway is blocked by viruses. This is a new way in which PRRSV avoids the immune system. Full article

Norovirus is the leading cause of acute infectious gastroenteritis in the world and accounts for a significant proportion of outbreaks at the food-borne and person-to-person levels. Due to their low infectious dose, persistence in the environment, and broad genetic diversity, they can quickly spread and reappear in even the most diverse populations. This review integrates current knowledge on the epidemiology of noroviruses, genomic organization, structural biology, virus–host interactions, and replication mechanisms, with a focus on factors that determine virus evolution and strain dominance. Literature has been systematically searched in the PubMed and Scopus databases to incorporate recent experimental and epidemiological findings. Analysis of global surveillance data indicates ongoing genetic diversification of circulating strains, with periodic replacement of major variants, particularly the GII.4 lineage. Variability of the capsid and recognition of histo-blood Group Antigens strongly affects the host’s susceptibility, viral attachment and immune escape. The capsid consists of most of the viral protein complexes. The structural proteins VP1 and VP2 are responsible for determining the contours of the capsid and antigenic specificity. Non-structural proteins are responsible for coordinating the genome replication and the modification of host cell pathways to favor the production of the virus. Eliminating these gaps by means of integrated genomic surveillance and functional studies will provide insight into the evolution of norovirus and help to develop broadly effective vaccines and antiviral strategies. Full article

Dengue infection remains a major global health concern, with a subset of patients progressing from self-limited dengue fever to severe disease characterised by plasma leakage, shock, and organ dysfunction. The dengue non-structural protein 1 (NS1), a multifunctional glycoprotein expressed on infected cells and secreted into circulation, has emerged as a key mediator linking viral infection to immune-driven vascular pathology. This review synthesises experimental, animal, and human clinical evidence on NS1-driven immunopathogenesis, focusing on mechanisms leading to endothelial dysfunction and increased vascular permeability. NS1 modulates the complement system in a context-dependent manner, contributing to immune evasion by inhibiting terminal complement complex formation, while also promoting antibody-dependent complement activation associated with severe disease. Additionally, NS1 directly disrupts endothelial barrier integrity through disruption of adherens and tight junction architecture, Ang-2/Tie2 imbalance, activation of RhoA/ROCK (RhoA/Rho-associated coiled-coil-containing protein kinase) signalling, and enzymatic degradation of the endothelial glycocalyx, with further amplification through inflammatory mediators. In addition, evidence shows that NS1 activates innate immune signalling, perturbs platelet biology and haemostasis, and forms pro-inflammatory complexes with lipoproteins. Moreover, anti-NS1 antibodies may be both protective and pathogenic. Collectively, these data position NS1-linked pathways as rational targets for adjunctive therapies and next-generation vaccines aimed at preventing vascular leakage and severe dengue infection. Full article

Macrosteles fascifrons, a representative aster leafhopper frequently detected in rice-growing environments, is an economically significant insect that inhabits rice fields and plays a role in the ecology of crop pests and disease transmission. To expand the understanding of viral diversity associated with the aster leafhopper, we analyzed its virome using deep transcriptome sequencing. In addition to several previously reported viruses, we identified two previously unreported RNA viruses, tentatively designated as Macrosteles fascifrons hepe-like virus 1 (MfHV1) and Macrosteles fascifrons rhabdovirus 1 (MfRV1). The complete genome sequences of both genomes were obtained using overlapping RT-PCR and rapid amplification of cDNA ends. Excluding the poly(A) tail, the genome of MfHV1 is 6688 nucleotides in length and exhibits a genomic organization characteristic of the family Hepeviridae, comprising three major open reading frames (ORFs) that encode a putative nonstructural polyprotein, a capsid protein, and a small accessory protein. The ORF encoding the capsid protein partially overlaps with the ORF encoding the small accessory protein, a genomic feature commonly observed in hepe-like viruses. The genome of MfRV1 is 14,984 nucleotides in length and displays the canonical genomic organization of the family Rhabdoviridae. An additional accessory ORF was identified between the putative M and G genes. Phylogenetic analysis based on polyprotein sequences placed MfHV1 within the Hepeviridae, most closely related to insect-associated hepe-like viruses, whereas MfRV1 clustered within the subfamily Deltarhabdovirinae. According to ICTV guidelines, virus classification is based on a combination of sequence divergence, phylogenetic relationships, and genome organization. MfHV1 and MfRV1 share low amino acid sequence identities with known viruses (maximum 36.07% for the MfHV1 polyprotein and 47.7% for the MfRV1 RNA-dependent RNA polymerase). Based on sequence divergence, genome organization, and phylogenetic placement, these viruses are classified as putative novel members of their respective families. This study expands the diversity of virus-associated sequences detected in M. fascifrons and provides additional genomic resources for understanding insect-associated RNA viruses. Full article

The detailed mechanism and sequence by which tick-borne flaviviruses (TBFVs), such as Langat virus (LGTV), infect and disseminate in arthropod hosts remain undefined. To begin characterizing these processes, we used artificial membrane feeding chambers to feed adult Ixodes scapularis ticks with blood containing LGTV. At 24, 48, 72, and 96 hours (h) after attachment, we removed and dissected the partially fed ticks to obtain the midgut and salivary glands. Histology confirmed infection in cells of the digestive epithelium lineage; infection was noted in midgut generative cells and the more differentiated functional digestive cells over the course of feeding. The viral envelope (E) protein, nonstructural protein 3 (NS3), and double-stranded RNA (dsRNA) were readily detected in these cells by 48 h after infection. Parallel analysis indicated that cells in salivary gland acini were also infected by 48 h, where virus target cells appeared to be the granular cells in acini types II and III. Thus, both salivary glands and midgut showed direct evidence of infection by 48 h. Although viral staining was not observed at 24 h, when organs were removed at 24 h and individually cultured ex vivo, the virus was detected. Taken together, our results provide evidence of LGTV infection in both the salivary glands and midgut within the first 24 h of a blood meal. The findings should prompt a reevaluation of the systemic dissemination of TBFV in infected ticks. Full article

Senecavirus A (SVA) has rapidly emerged as a globally distributed swine pathogen, with clinical signs mimicking vesicular diseases such as Foot-and-Mouth Disease, posing challenges for timely detection and control. Here, we analyzed 329 complete SVA genomes spanning multiple continents to provide a comprehensive view of its evolutionary dynamics, recombination patterns, haplotype diversity, and global dissemination. Phylogenetic analyses revealed two major lineages: Lineage 1, consisting mainly of early strains from the United States before 2007, and Lineage 2, which emerged post-2007 and subsequently spread across the Americas and East Asia. Recombination was confined to Lineage 2 and concentrated in nonstructural regions, particularly 2C, highlighting intra-lineage genetic exchange as a driver of recent diversification. Haplotype analysis of the 3AB gene identified 170 distinct haplotypes, revealing a star-like network structure consistent with rapid population expansion from a central ancestral variant, while secondary branches reflect ongoing regional diversification. Despite this high genetic variation, genome-wide dN/dS ratios remained below one, and purifying selection was strongest in the N-terminal domains of structural and nonstructural proteins, indicating functional constraints that maintain viral fitness. Time-scaled phylogenetic reconstruction and Bayesian Skyline analysis revealed rapid lineage diversification and a marked increase in effective population size in the early 2010s. Phylogeographic inference further identified repeated introductions from the Americas into East Asia, likely facilitated by swine trade and other anthropogenic factors. Collectively, SVA evolution is driven by frequent mutation and intra-lineage recombination yet constrained by pervasive purifying selection, generating extensive genetic diversity while maintaining functional integrity, with implications for genomic surveillance and targeted control. Full article

Bluetongue virus (BTV), the prototype of the genus Orbivirus, infects livestock, causing high morbidity and mortality and impacting global trade. BTV is a non-enveloped, double-capsid virus, composed of seven structural proteins and a genome of 10 double-stranded RNA segments. This manuscript highlights our group’s recent findings on the molecular and structural mechanisms underlying BTV entry and assembly during replication. Viral entry is a stepwise, pH-dependent process. The outermost protein, VP2, attaches to sialic acids and senses the acidic pH of early endosomes, triggering their dissociation. Subsequently, the second outer capsid protein, VP5, undergoes major changes in late endosomes, forming a membrane-penetrating pore that releases the transcriptionally active inner core into the host cytoplasm. Core assembly also proceeds stepwise and requires the accurate packaging of 10 positive-sense RNA segments. These segments form an RNA–RNA interaction network independent of viral proteins, beginning with the smaller segments and guiding the complete genome assortment. The small capsid protein, VP6, interacts with VP3 to facilitate RNA encapsidation. While infectious cores assemble in vitro without non-structural proteins, NS2 is essential for the in vivo formation of viral inclusion bodies via liquid–liquid phase separation, concentrating viral components and promoting genome assembly. These comprehensive characterizations of BTV provide a foundation for future control strategies against related reoviruses. Full article

Drought stress profoundly affects plant growth and survival, but comparisons of integrated adaptive strategies across multiple tree species remain unclear. In this study, seedlings of Elaeagnus angustifolia (E. angustifolia), Populus euphratica (P. euphratica) and Xanthoceras sorbifolium (X. sorbifolium) were subjected to well-watered (CK), mild (T1), moderate (T2), and severe (T3) drought treatments. Leaf microanatomical traits, non-structural carbohydrates (NSCs), stoichiometric elements, biomass allocation, and key stress indicators were measured. The results showed that P. euphratica seedlings thickened leaves and vascular tissues and accumulated soluble sugars (SSs) and starch (ST) under T1–T2, but under T3, they prioritized root investment (root biomass +26.0%); their antioxidant enzymes were activated only under mild-to-moderate stress and declined under severe stress. E. angustifolia seedlings exhibited moderate leaf structural thickening, sharply increased root biomass (+97.2% under T3) while maintaining stem biomass, continuously elevated activities of superoxide dismutase (SOD) and peroxidase (POD) as well as osmoregulatory substances (soluble protein SP, proline Pro), and showed the lowest malondialdehyde (MDA) content; their leaf carbon (C), nitrogen (N), and phosphorus (P) contents decreased the least, and their stoichiometric ratios remained stable. In contrast, X. sorbifolium seedlings progressively reduced leaf thickness and vascular area, depleted NSC reserves, exhibited unstable antioxidant responses, showed a significant decrease in Pro under severe drought, accumulated the highest MDA, and had the lowest N/P ratio, indicating the strongest nitrogen limitation. These results demonstrate that E. angustifolia combines structural plasticity, efficient nutrient use, robust osmotic adjustment, and sustained antioxidant capacity, conferring the strongest drought tolerance; P. euphratica* shows moderate tolerance through transient structural and carbon investment but suffers under extreme drought; X. sorbifolium has the weakest drought tolerance. Full article