Search Results (480)

The tomato zonate spot virus (TZSV) poses a significant threat to agriculture. Therefore, the elucidation of the functional roles and interactions of its encoded proteins is crucial for the development of effective control strategies. The aim of this study was to investigate the interaction network between the TZSV nucleocapsid (N), the non-structural M-segment (NSm) and the non-structural S-segment (NSs) proteins, with a focus on the functional characterization of the NSm protein. Yeast two-hybrid (Y2H) analysis indicated that both the N protein (N-N) and the NSm protein (NSm-NSm) exhibit self-interaction in vitro, with successful expression of all fusion proteins confirmed by Western blotting. Subsequently, we used bimolecular fluorescence complementation (BiFC) and luciferase complementation imaging (LCI) assays in epidermal cells of Nicotiana benthamiana to confirm that N and NSm proteins self-interact. In addition, heterologous interactions between NSs-N, N-NSm and NSs-NSm were also detected. BiFC and co-localization experiments with fusion proteins elucidated the interaction place of the cell: N-N and NSm-N interactions occurred in both the cytoplasm and nucleus, with NSm-NSm interaction occurring in the nucleus, whereas NSs-N and NSs-NSm interactions only occurred in the cytoplasm. Subcellular localization studies showed that the N protein is distributed in both the cytoplasm and the nucleus, whereas the NSm and NSs proteins are predominantly localized in the cytoplasm. In particular, NSm was found to specifically target plasmodesmata (PD) and co-localize with the known PD marker protein PDLP8. Interestingly, TZSV NSm was demonstrated to mediate the cell-to-cell movement of a cucumber mosaic virus mutant (ΔCMV-GFP) lacking its native movement protein (3a). This was evidenced by the spread of approximately 50 fluorescent foci to neighboring cells observed at 6 dpi. This study comprehensively describes the intricate interaction network between the N, NSm and NSs proteins of TZSV and clarifies their subcellular localizations within plant cells. Crucially, we provide conclusive evidence that the NSm protein of TZSV is a functional movement protein essential for facilitating viral intercellular transport which promotes viral spread within the host during systemic infection. These findings offer important insights into the infection mechanism of TZSV and provide potential targets for the control of TZSV. Full article

Background: Human adenovirus type 4 (HAdV-4), the sole member of species Human mastadenovirus E (HAdV-E), is of zoonotic origin and has established stable human transmission through recombination, conferring distinctive host adaptation and pathogenicity. It causes respiratory and ocular diseases, with a significant risk of severe pneumonia in children. No targeted antivirals are approved for routine use, leaving supportive care as the primary management. China bears a relatively high HAdV-4 disease burden in Asia. Methods: To generate neutralizing nanobodies (Nbs) against HAdV-4, we employed an alpaca immunization strategy using hexon protein from Ad4-RI67 strain, followed by the isolation of hexon-specific nanobodies. The epitope competition and molecular docking was employed to analysis the binding site of the Nbs’. We engineered VHH-Fc fusions by conjugating VHH domains to human IgG1 Fc. The lead candidate, NVA17, showed efficacy in both in vitro and in vivo (Stat1^+/− mouse model). Flow cytometric analysis was employed to assess the downstream immune effects of NVA17 in vivo. Its intracellular neutralization mechanism was further investigated through confocal microscopy by examining co-localization in TRIM21-overexpressing and knockdown cells. Results: The isolated nanobodies revealed epitopes distinct from those targeted by known antibodies. The lead candidate NVA17 demonstrated potent neutralizing activity in vitro (IC₅₀ < 10 ng/mL). In the Stat1^+/− mouse model, NVA17 provided complete protection against lethal challenge, significantly reduced viral load in the lungs, and ameliorated pathological damage. NVA17 treatment dose-dependently reversed the virus-induced reduction in immune cell counts and enhanced cytotoxicity, suggesting a systemic immunomodulatory effect. Mechanistic studies indicated that the antiviral activity of NVA17 partly depends on the TRIM21-mediated antibody-dependent intracellular neutralization (ADIN) pathway, whereby TRIM21 terminates the viral life cycle by promoting viral degradation via K48-linked ubiquitination. Conclusions: We have identified multiple antibody candidates, particularly NVA17, with significant therapeutic potential for developing antibody-based treatments against HAdV-4. This offers a targeted intervention strategy to counter the current lack of specific antiviral therapies. Full article

Background/Objectives: Flaviviruses, including West Nile virus (WNV), pose global health challenges due to their worldwide distribution, pathogenicity, and lack of effective treatments or vaccines. Today, WNV is considered the most important causative agent of viral encephalitis worldwide. This study investigated the different forms of the main WNV antigen—the preM/E protein—in the context of its immunogenic and protective properties. Methods: The recombinant adenovirus type 2 (rAd2) vectors expressing different forms of the WNV preM/E genes were obtained using standard molecular biology techniques. Immunogenicity in mice was assessed by enzyme-linked immunosorbent assay (ELISA) and virus neutralization assay. Immunological efficacy was evaluated in a mouse viral challenge model. Results: The rAd2 vector expressing the West Nile virus preM/E gene with mutations in the fusion loop exhibited robust immunogenicity when administered intramuscularly either once or in a homologous prime-boost regimen. This antigen form, as part of an adenoviral vector, protected mice from death in viral challenge experiments, providing 100% survival following WNV challenge. Conclusions: We believe that a vaccination strategy involving a recombinant adenoviral vector based on human adenovirus type 2 and the WNV antigen represented by the preM/E gene with mutations in the fusion loop may be a promising approach for combating West Nile virus infection. Full article

Bovine parainfluenza virus type 3 (BPIV3) is a significant pathogen implicated in bovine respiratory disease complex (BRDC), leading to lung tissue destruction, immunosuppression, and subsequent bacterial infections in cattle, hence incurring considerable economic losses globally. Notwithstanding its importance, a limited number of commercial vaccinations are presently accessible. The fusion (F) protein and hemagglutinin-neuraminidase (HN) protein, as protective antigens of the Paramyxoviridae family, can elicit neutralizing antibodies and are regarded as optimal candidates for the creation of genetically modified vaccines. A multi-epitope-based peptide vaccine (MEBPV) was developed by immunoinformatics methodologies by choosing epitopes from the F and HN proteins characterized by high antigenicity, moderate toxicity, and limited allergenic potential. The epitopes were combined with suitable linkers and adjuvants to produce the vaccine, whose physicochemical qualities, immunological attributes, solubility, and structural stability were improved and evaluated using computational methods. Molecular docking and molecular dynamics simulations demonstrated the strong potential binding affinity and stability of the vaccination with TLR2, TLR3, and especially TLR4 receptors. Immune simulations forecasted strong humoral and cellular responses, accompanied by a significant elevation in interferon-γ (IFN-γ) production. The vaccine sequence was later cloned into the pET-28a (+) vector for possible expression in Escherichia coli. Despite in silico predictions suggesting a favorable immunogenic potential, additional in vitro and in vivo studies are necessary to confirm its protective efficacy and safety. This research establishes a solid foundation for the creation of safe and efficacious subunit vaccines targeting BPIV3 and presents novel perspectives for the formulation of vaccinations against additional viral infections. Full article

Zika virus (ZIKV) caused Zika outbreaks and continues to post threats to public health. ZIKV infection may cause congenital abnormalities during pregnancy and neurological manifestations in adults. The recurrent public health threat of Zika in various geographical areas demonstrates a need for the development of effective therapeutics. Currently, there are no approved therapies for Zika. ZIKV is a single-stranded, positive-sense RNA virus, whose genome encodes three structural proteins and seven non-structural proteins. The surface envelope (E) protein is essential for host–cell recognition and viral entry; therefore, inhibition of E-mediated viral entry is a key strategy underlying antiviral treatments. Here, molecular docking-based virtual screening was used to screen small-molecule compound libraries to identify potential ZIKV entry inhibitors. Among the compounds identified, Pyrimidine-Der1 exhibited efficient inhibition of reporter ZIKV infection. The microscale thermophoresis assay confirmed its binding with the ZIKV E protein. This compound has effective inhibition of authentic ZIKV infection in a plaque inhibition assay against R103451, PAN2016, and FLR human strains (IC₅₀: ~3–5 μM). Additionally, it efficiently inhibited ZIKV infection at viral entry and fusion steps of the virus life cycle in a time-of-addition assay. Overall, Pyrimidine-Der1 is a promising ZIKV entry inhibitor, warranting further optimization and evaluation. Full article

Background: The extracellular domain of the M2 protein (M2e) and the conserved region of the second subunit of the hemagglutinin (HA2, 76–130 а.а.) of the influenza A virus, could be used to develop broad-spectrum influenza vaccines. However, these antigens have low immunogenicity and require the use of special carriers to enhance it. Virus-like particles (VLPs) formed from viral capsid proteins are among the most effective carriers. Methods: In this work, we obtained and characterized VLPs based on capsid proteins (CPs) of single-stranded RNA bacteriophages Beihai32 and PQ465, simultaneously displaying M2e and HA2 peptides. Results: Fusion proteins expressed in Escherichia coli formed spherical VLPs of about 30 nm in size. Subcutaneous immunization of mice with chimeric VLPs elicited a robust humoral immune response against M2e and the whole influenza A virus, and promoted the formation of cytokine-secreting antigen-specific CD4⁺ and CD8⁺ effector memory T cells. Conclusions: VLPs based on CPs of phages Beihai32 and PQ465 carrying conserved peptides M2e and HA2 of the influenza A virus can be used for the development of universal influenza vaccines. Full article

Furin, a calcium-dependent serine endoprotease of the proprotein convertase family, plays a pivotal role in both physiological homeostasis and viral pathogenesis. By cleaving polybasic motifs within viral glycoproteins, furin enables the maturation of structural proteins essential for viral entry, fusion, and replication. This mechanism has been documented across a broad spectrum of human pathogens, including SARS-CoV-2, influenza virus, human immunodeficiency virus, human papilloma virus, hepatitis B virus, flaviviruses, herpesviruses, and paramyxoviruses, highlighting furin as a conserved molecular hub in host–virus interactions. Genetic variability within the FURIN gene further modulates infection outcomes. Several single-nucleotide polymorphisms (SNPs), such as rs6226 and rs1981458, are associated with altered COVID-19 severity, whereas variants like rs17514846 confer protection against human papilloma virus infection. Conversely, mutations predicted to reduce enzymatic activity have been linked to attenuated SARS-CoV-2 pathogenesis in certain populations. These findings underscore the importance of considering population genetics when evaluating viral susceptibility and disease progression. Despite advances, unresolved questions remain regarding furin’s non-canonical roles in viral life cycles, tissue-specific regulation, and interactions with other host proteases and immune modulators. Targeted inhibition of furin and related convertases represents a promising avenue for broad-spectrum antiviral interventions. Collectively, current evidence positions furin as a central node at the intersection of viral pathogenesis, host genetic variability, and translational therapeutic potential. Full article

Oropouche virus (OROV), an emerging orthobunyavirus of increasing public health concern in the Americas, currently lacks approved antiviral therapies. In this study, we employed a structure-based in silico approach to identify natural antiviral scaffolds capable of targeting the Gc glycoprotein, a class II fusion protein essential for host membrane fusion and viral entry. A library of 537 plant-derived compounds was screened against the Gc head domain (PDB ID: 6H3X) through molecular docking and redocking, followed by 100-nanosecond molecular dynamics simulations, MM-PBSA free energy calculations, and ADMET profiling. Curcumin and Berberine emerged as standout candidates. Curcumin demonstrated a balanced profile, with stable binding (−38.14 kcal/mol), low backbone RMSD (1.82 Å), and consistent radius of gyration (Rg ~ 18.8 Å), suggesting strong conformational stability and compactness of the protein–ligand complex. Berberine exhibited the most favorable binding energy (−13.10 kcal/mol) and retained dynamic stability (RMSD 1.86 Å; Rg ~ 19.0 Å), though accompanied by predicted cytotoxicity that may require structural refinement. Both compounds induced reduced residue-level fluctuations (RMSF < 2.5 Å) in functionally critical regions of the Gc protein, consistent with a mechanism of action that involves stabilization of the prefusion conformation and interference with the structural transitions required for viral entry. These findings identify curcumin and berberine as promising scaffolds for anti-OROV drug development and offer a rational foundation for future experimental validation targeting viral fusion mechanisms. Full article

The focus of this study was to explore phage display systems employing bacteriophage lambda (λ) gene fusions to its capsid decoration protein gpD as reagent tools for tackling disease. The biological activity of gpD-fusions was examined by testing for the retained antimicrobial toxicity of cathelicidins or defensins fused to gpD. Our previous finding that only COOH fusions of either cathelicidins or defensins to gpD were toxigenic was expanded to show that only the reduced form of fused defensin antimicrobial polypeptides was found to be toxigenic. Compared in review are gene-fusion lytic display systems (where the fusion-display gene is integrated within the viral genome) with a surrogate system, employed herein, that exogenously provides the fusion-display protein for addition to phage capsid. It is easily possible to produce fully coated lambda display particles (LDP) serving as single epitope vaccines (SEV), or antimicrobials, or to produce partially coated LDP without any complex bacteriophage genetic engineering, making the system available to all. The potential to build vaccine vector phage particles (LDNAP) comprising essentially sheathed DNA vaccines encapsulated within an environmentally protective capsid is described. LDNAP are produced by introducing a cassette into the phage genome either by phage–plasmid recombination or cloning. The cassette carries a high-level eukaryotic expression promoter driving transcription of the vaccine candidate gene and is devoid of plasmid resistance elements. Full article

Chikungunya virus (CHIKV) is an arthritogenic alphavirus transmitted primarily via Aedes aegypti and Aedes albopictus mosquitoes. Since its identification, CHIKV remained confined to parts of Africa and Asia until the early 2000s, when it expanded to other continents, causing epidemics. Structurally, it is an enveloped virus with a positive-single-stranded RNA genome, which encodes four non-structural proteins (nsP1-nsP4), responsible for viral replication, and five structural proteins (C, E3, E2, 6K, and E1), which form the capsid and envelope. Of these proteins, glycoproteins E1 and E2 are essential for cell recognition and membrane fusion, determining infectivity and viral tropism. CHIKV replication occurs in the cytosol of different cell types, triggering an intense inflammatory and immune response, which manifests clinically as Chikungunya fever (CHIKF). Despite its epidemiological impact, current treatment is limited to symptomatic approaches, including the use of analgesics and anti-inflammatories, as no specific antiviral therapies are available. In response, promising advances are being made, including the development of vaccines, targeted antivirals, and immunotherapies. This article aims to review the main aspects of viral biology, epidemiology, and immunopathogenesis of CHIKV infection, in addition to discussing the main advances in the development of new therapeutic approaches for its control. Full article

Piscine orthoreovirus (PRV) is a globally distributed viral pathogen that causes heart and skeletal muscle inflammation (HSMI) in Atlantic salmon (Salmo salar) and affects other salmonids, yet no commercial vaccines are currently available. Major barriers to vaccine development include the inability to propagate PRV in cell lines and the low, variable immunogenicity of its proteins, particularly the outer capsid protein σ1, which mediates viral attachment. This protein is hypothesized to be immunologically relevant due to its homology with Mammalian orthoreoviruses. Recombinant σ1 expressed in conventional systems exhibits poor antibody recognition, whereas structural modifications such as lipidation or fusion with molecular chaperones improve epitope exposure. Formalin-inactivated vaccines have shown inconsistent protection, often failing to elicit robust innate or adaptive responses, especially under cohabitation challenge. In contrast, DNA vaccines encoding σ1 and the non-structural protein μNS have demonstrated partial efficacy, likely due to enhanced intracellular expression and antigen presentation. Nonetheless, the considerable variability observed in immune responses among individual fish and viral genotypes, together with suggestions that PRV may interfere with antiviral pathways, represent additional barriers to achieving consistent vaccine efficacy. This review summarizes the current status of PRV vaccine development and discusses future directions for rational design based on optimized antigens and intracellular delivery platforms. Full article

Virus-like particles (VLPs) formed as a result of self-assembly of viral capsid proteins are widely used as a platform for antigen presentation in vaccine development. However, since the inclusion of a foreign peptide into the capsid protein can alter its spatial structure and interfere with VLP assembly, such insertions are usually limited to short peptides. In this study, we have demonstrated the potential of capsid protein (CP) of single-stranded RNA phage PQ465 to present long peptides using green fluorescent protein (GFP) as a model. GFP was genetically linked to either the N- or C-terminus of PQ465 CP. Hybrid proteins were expressed in Escherichia coli and Nicotiana benthamiana plants. Spherical virus-like particles (~35 nm according to transmission electron microscopy) were successfully formed by both N- and C-terminal fusions expressed in E. coli, and by plant-produced CP with GFP fused to the C-terminus. ELISA revealed that GFP in VLPs was accessible for specific antibodies suggesting that it is exposed on the surface of PQ465-GFP particles. VLPs carrying GFP were recognized by anti-CP antibodies with less efficiency than VLPs formed by empty CP, which indicates shielding of the CP core in PQ465-GFP particles. Therefore, PQ465 CP can be used as a chimeric VLP platform for the display of relatively large protein antigens, which can operate in bacterial and plant expression systems. Full article

Introduction/Background: Rift Valley fever virus (RVFV) and peste des petits ruminants virus (PPRV) are significant pathogens affecting small ruminants, causing substantial economic losses in the affected regions. The development of effective vaccines against both viruses is crucial for disease control. Recombinant viruses expressing heterologous antigens have shown promise as multivalent vaccine candidates. Unlike conventional PPRV vaccines, our recombinant RVFV-vectored vaccines offer a novel dual-protection strategy against RVF and PPR, combining safety, immunogenicity, and a DIVA strategy. Methods: Recombinant RVFVs (ZH548 strain) were generated to express either the hemagglutinin (H) or fusion (F) proteins from the PPRV strain Nigeria 75/1. The stability of these recombinant viruses was assessed through consecutive passages in cell culture. Immunogenicity studies were carried out in both mice and sheep to assess the induction of cellular and humoral immune responses capable of providing protection against RVFV and PPRV. These studies included intracellular cytokine staining (ICS), IFN-γ ELISAs, standard ELISAs for antibody detection, and virus neutralization assays. Results: The recombinant RVFVs expressing PPRV H or F proteins demonstrated stability in cell culture, maintaining high viral titers and consistent transgene expression over four passages. Immunization of mice resulted in the production of serum antibodies capable of neutralizing both RVFV and PPRV in vitro as well as cell-mediated immune responses specific to PPRV and RVFV antigens. In mice vaccinated with a high dose (10⁵ pfu), RVFV neutralizing titers reached ≥1:160 and PPRV neutralizing titers ranged from 1:40 to 1:80 by day 30 post-immunization. In sheep, neutralizing antibody titers against RVFV exceeded 1:160 as early as 2 days post-inoculation, while PPRV-specific neutralization titers reached up to 1:80 by day 21 in responsive individuals. In mice, administration of rZH548ΔNSs:F_PPRV elicited a detectable CD8+ IFNγ+ T-cell response against PPRV, with levels ranging from 1.29% to 1.56% for the low and high doses, respectively. In sheep, rZH548ΔNSs:F_PPRV also induced a robust IFNγ production against PPRV at 14 and 21 days post-infection (dpi). Conclusions: The successful generation and characterization of recombinant RVFVs expressing PPRV antigens demonstrate the potential of using rationally attenuated RVFV as a vector for multivalent vaccine development. Notably, the strategy proved more effective for the recombinant virus expressing the F protein, as it consistently induced more robust cellular and humoral immune responses. These results suggest that this approach could be a viable strategy for simultaneous immunization against Rift Valley fever and other prevalent ruminant diseases, such as peste des petits ruminants. Even though challenge studies were not performed in target species, the strong immune response observed supports including them in future studies. Full article

The negative strand of the human immunodeficiency virus-1 (HIV-1) proviral genome contains an antisense open reading frame encoding a protein (ASP) with no known homologs. The presence of immune responses to ASP in people living with HIV-1 (PLWH) demonstrates its expression in vivo. Further, the predicted hydrophobicity of ASP is consistent with its association with the plasma membrane and viral envelope. Despite this body of evidence, the role of ASP in HIV-1 replication remains unknown. In this report, we investigated the hypothesis that the presence of ASP on the viral surface enhances HIV-1 entry into target cells. We generated an ASP-knockout replication-competent HIV-1 molecular clone in the NL4-3 background, which we used to perform cell–cell fusion, viral entry, and viral replication assays. Our results suggest that the presence of ASP on the plasma membrane of infected cells and the envelope of HIV-1 virions enhances viral transmission. Overall, our studies provide first evidence that ASP plays a role in the HIV-1 replication cycle. Further investigation into these observations may lead to the identification of new HIV-1 vulnerabilities that may be the target of novel interventions. Full article

The cellular membrane is a dynamic structure composed of lipids and proteins organized into specialized domains that facilitate interactions between extracellular molecules and the intracellular environment. Tetraspanins are a family of transmembrane proteins involved in diverse cellular processes, including membrane stabilization and fusion, endocytosis, extracellular vesicle formation, and the organization of proteins and lipids at specific membrane sites known as Tetraspanin-Enriched Microdomains (TEMs). These lipid–protein interactions play a critical role in the replicative cycle of Orthoflavivirus, including dengue, Zika, and West Nile, by facilitating viral entry, replication, assembly, and egress. In addition, tetraspanins also regulate the biogenesis and function of extracellular vesicles, contributing to viral dissemination, persistent infection, and immune evasion. This review summarizes the current knowledge on the structural and functional aspects of tetraspanins, their interplay with lipids, and their emerging roles in the Orthoflavivirus replicative cycle. We also discuss how these insights may inform the development of antiviral strategies targeting membrane organization and virus–host interactions. Full article