Search Results (1,101)

The emergence of SARS-CoV-2 variants highlights the urgent need for novel therapeutic strategies, particularly entry inhibitors that could efficiently prevent viral infection. Medicinal herbs and herbal combination formulas have long been recognized for their effects in treating infectious diseases and their antiviral properties, thus providing abundant resources for the discovery of antiviral candidates. While many candidates have been suggested to have antiviral activity against SARS-CoV-2 infection, few have been validated for their mechanisms, including possible effects on viral entry. This study aimed to identify SARS-CoV-2 entry inhibitors from medicinal herbs and herbal formulas that are known for heat-clearing and detoxifying properties and/or antiviral activities. A SARS-CoV-2 pseudoparticle (SARS-CoV-2pp) system was used to assess mechanism-specific entry inhibition. Our results showed that the methanol extract of Anemarrhena asphodeloides rhizome, as well as the water extracts of Cimicifuga foetida rhizome, Xiao Chai Hu Tang (XCHT), and Sheng Ma Ge Gen Tang (SMGGT), have substantial inhibitory effects on the entry of SARS-CoV-2pps into host cells. Given the observation that Cimicifuga foetida exhibited the most potent inhibition and is a constituent of SMGGT, we further investigated the major compounds of the herb and identified caffeic acid as a bioactive component for blocking SARS-CoV-2pp entry. Entry inhibition of Cimicifuga foetida and caffeic acid was validated on both wild-type and the currently dominant JN.1 strain SARS-CoV-2pp systems. Moreover, caffeic acid was able to both inactivate the pseudoparticles and prevent their entry into pretreated host cells. The results support the traditional use of these herbal medicines and underscore their potential as valuable resources for identifying active compounds and developing therapeutic entry inhibitors for the management of COVID-19. 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

Měnglà virus (MLAV) is a member of the genus Dianlovirus in the family Filoviridae, which also includes Ebola virus (EBOV) and Marburg virus (MARV). Whether MLAV poses a threat to human health is uncertain. However, the MLAV VP35 and VP40 proteins can impair IFNα/β gene expression and block IFNα/β-induced Jak-STAT signaling, respectively, suggesting the capacity to counteract human innate immune defenses. In this study, MLAV VP40 is demonstrated to impair the Sendai virus (SeV)-induced activation of the IFNβ promoter. Inhibition is independent of the MLAV VP40 PPPY late-domain motif that interacts with host proteins possessing WW-domains to promote viral budding. Similar IFNβ promoter inhibition was not detected for EBOV or MARV VP40. MLAV VP40 exhibited lesser capacity to inhibit TNFα activation of an NF-κB reporter gene. MLAV VP40 impaired IFNβ promoter activation by an over-expressed, constitutively active form of RIG-I and by the over-expressed IRF3 kinases TBK1 and IKKε. However, MLAV VP40 did not inhibit IFNβ promoter activation by constitutively active IRF3 5D. Consistent with these findings, MLAV VP40 inhibited SeV-induced IRF3 phosphorylation. Although IRF3 phosphorylation occurs in the cytoplasm, MLAV VP40 exhibits substantial nuclear localization, accumulating in foci in HeLa cell nuclei. In contrast, the VP40 of EBOV and MARV exhibited lower degrees of nuclear localization and did not accumulate in foci. MLAV VP40 interacts with importin alpha-1 (IMPα1), suggesting entry via the IMPα/IMPβ nuclear import pathway. Cumulatively, these data identify novel features that distinguish MLAV VP40 from its homologues in EBOV and MARV. Full article

Recently, essential rose oils and rose products have gained increasing importance in both the cosmetic and food industries, as well as in the composition of medicinal products. We investigated the in vitro antiviral activity of essential oil and floral water from Rosa damascena Mill against herpes simplex virus type 1 (HSV-1) infection in rabbit retinal cells (RRCs). The composition of the main chemical components in the rose essential oil was determined by means of gas chromatographic analysis. The effect on the viral replication cycle was determined using the cytopathic effect (CPE) inhibition assay. The virucidal activity, the effect on the adsorption stage of the virus to the host cell, and the protective effect on healthy cells were evaluated using the endpoint dilution method. The effects were determined as deviation in the viral titer, Δlg, for the treated cells from the one for the untreated viral control. The identified main active components of rose oil are geraniol (28.73%), citronellol (21.50%), nonadecane (13.13%), nerol (5.51%), heneicosane (4.87%), nonadecene (3.93), heptadecane (2.29), farnesol (2.11%), tricosane (1.29%), eicosane (1.01%), and eugenol (0.85%). The results demonstrated that both rose products do not have a significant effect on the virus replication but directly affect the viral particles and reduce the viral titer by Δlg = 3.25 for floral water and by Δlg = 3.0 for essential oil. Significant inhibition of the viral adsorption stage was also observed, leading to a decrease in the viral titers by Δlg = 2.25 for floral water and by Δlg = 2.0 for essential oil. When pretreating healthy cells with rose products, both samples significantly protected them from subsequent infection with HSV-1. This protective effect was more pronounced for the oil (Δlg = 2.5) compared to the one for the floral water (Δlg = 2.0). We used the in silico molecular docking method to gain insight into the mechanism of hindrance of viral adsorption by the main rose oil compounds (geraniol, citronellol, nerol). These components targeted the HSV-1 gD interaction surface with nectin-1 and HVEM (Herpesvirus Entry Mediator) host cell receptors, at N-, C-ends, and N-end, respectively. These findings could provide a structural framework for further development of anti-HSV-1 therapeutics. Full article

The focal “hot spot” neuropathologies in COVID-19 infection are revealing footprints of a hidden underlying collapse of a novel ultrafast ultradian Piezo2 signaling system within the nervous system. Paradoxically, the same initiating pathophysiology may underpin the systemic findings in COVID-19 infection, namely the multiorgan SARS-CoV-2 infection-induced vascular pathologies and brain–body-wide systemic pro-inflammatory signaling, depending on the concentration and exposure to infecting SARS-CoV-2 viruses. This common initiating microdamage is suggested to be the primary damage or the acquired channelopathy of the Piezo2 ion channel, leading to a principal gateway to pathophysiology. This Piezo2 channelopathy-induced neural switch could not only explain the initiation of disrupted cell–cell interactions, metabolic failure, microglial dysfunction, mitochondrial injury, glutamatergic synapse loss, inflammation and neurological states with the central involvement of the hippocampus and the medulla, but also the initiating pathophysiology without SARS-CoV-2 viral intracellular entry into neurons as well. Therefore, the impairment of the proposed Piezo2-induced quantum mechanical free-energy-stimulated ultrafast proton-coupled tunneling seems to be the principal and critical underlying COVID-19 infection-induced primary damage along the brain axes, depending on the loci of SARS-CoV-2 viral infection and intracellular entry. Moreover, this initiating Piezo2 channelopathy may also explain resultant autonomic dysregulation involving the medulla, hippocampus and heart rate regulation, not to mention sleep disturbance with altered rapid eye movement sleep and cognitive deficit in the short term, and even as a consequence of long COVID. The current opinion piece aims to promote future angles of science and research in order to further elucidate the not entirely known initiating pathophysiology of SARS-CoV-2 infection. Full article

Nipah virus (NiV) is a highly pathogenic bat-borne zoonotic pathogen that poses a significant threat to human and animal health, with fatality rates exceeding 70% in some outbreaks. Despite its significant public health impact, there are currently no licensed vaccines or specific therapeutics available. Various virological tools—such as reverse genetics systems, replicon particles, VSV-based pseudoviruses, and recombinant Cedar virus chimeras—have been widely used to study the molecular mechanisms of NiV and to support vaccine development. Building upon these platforms, we developed a replication-competent recombinant vesicular stomatitis virus (rVSVΔG-eGFP-NiV_BD F/G) expressing NiV attachment (G) and fusion (F) glycoproteins. This recombinant virus serves as a valuable tool for investigating NiV entry mechanisms, cellular tropism, and immunogenicity. The virus was generated by replacing the VSV G protein with NiV F/G through reverse genetics, and protein incorporation was confirmed via immunofluorescence and electron microscopy. In vitro, the virus exhibited robust replication, characteristic cell tropism, and high viral titers in multiple cell lines. Neutralization assays showed that monoclonal antibodies HENV-26 and HENV-32 effectively neutralized the recombinant virus. Furthermore, immunization of golden hamsters with inactivated rVSVΔG-eGFP-NiV_BD F/G induced potent neutralizing antibody responses, demonstrating its robust immunogenicity. These findings highlight rVSVΔG-eGFP-NiV_BD F/G as an effective platform for NiV research and vaccine development. Full article

Multivalent lectin–glycan interactions (MLGIs) are vital for viral infection, cell-cell communication and regulation of immune responses. Their structural and biophysical data are thus important, not only for providing insights into their underlying mechanisms but also for designing potent glycoconjugate therapeutics against target MLGIs. However, such information remains to be limited for some important MLGIs, significantly restricting the research progress. We have recently demonstrated that functional nanoparticles, including ∼4 nm quantum dots and varying sized gold nanoparticles (GNPs), densely glycosylated with various natural mono- and oligo- saccharides, are powerful biophysical probes for MLGIs. Using two important viral receptors, DC-SIGN and DC-SIGNR (together denoted as DC-SIGN/R hereafter), as model multimeric lectins, we have shown that α-mannose and α-manno-α-1,2-biose (abbreviated as Man and DiMan, respectively) coated GNPs not only can provide sensitive measurement of MLGI affinities but also reveal critical structural information (e.g., binding site orientation and mode) which are important for MLGI targeting. In this study, we produced mannuronic acid (ManA) coated GNPs (GNP-ManA) of two different sizes to probe the effect of glycan modification on their MLGI affinity and antiviral property. Using our recently developed GNP fluorescence quenching assay, we find that GNP-ManA binds effectively to both DC-SIGN/R and increasing the size of GNP significantly enhances their MLGI affinity. Consistent with this, increasing the GNP size also significantly enhances their ability to block DC-SIGN/R-augmented virus entry into host cells. Particularly, ManA coated 13 nm GNP potently block Ebola virus glycoprotein-driven entry into DC-SIGN/R-expressing cells with sub-nM levels of EC₅₀. Our findings suggest that GNP-ManA probes can act as a useful tool to quantify the characteristics of MLGIs, where increasing the GNP scaffold size substantially enhances their MLGI affinity and antiviral potency. Full article

Background: Lipid nanoparticles (LNPs) represent one of the most effective non-viral vectors for nucleic acid delivery and have demonstrated clinical success in siRNA therapies and mRNA vaccines. While considerable research has focused on optimizing ionizable lipids and helper lipids, the impact of PEGylated lipid content on LNP-mediated mRNA delivery, especially in terms of in vitro transfection efficiency and in vivo performance, remains insufficiently understood. Methods: In this study, LNPs were formulated using a self-synthesized ionizable lipid and varying molar ratios of DMG-PEG2000. Nanoparticles were prepared via nanoprecipitation, and their physicochemical properties, mRNA encapsulation efficiency, cellular uptake, and transfection efficiency were evaluated in HeLa and DC2.4 cells. In vivo delivery efficiency and organ distribution were assessed in mice following intravenous administration. Results: The PEGylated lipid content exerted a significant influence on both the in vitro and in vivo performance of LNPs. A bell-shaped relationship between PEG content and transfection efficiency was observed: 1.5% DMG-PEG2000 yielded optimal mRNA transfection in vitro, while 5% DMG-PEG2000 resulted in the highest transgene expression in vivo. This discrepancy in optimal PEG content may be attributed to the trade-off between cellular uptake and systemic circulation: lower PEG levels enhance cellular internalization, whereas higher PEG levels improve stability and in vivo bioavailability at the expense of cellular entry. Furthermore, varying the PEG-lipid content enabled the partial modulation of organ distribution, offering a formulation-based strategy to influence biodistribution without altering the ionizable lipid structure. Conclusions: This study highlights the critical role of PEGylated lipid content in balancing nanoparticle stability, cellular uptake, and in vivo delivery performance. Our findings provide valuable mechanistic insights and suggest a straightforward formulation-based strategy to optimize LNP/mRNA systems for therapeutic applications. Full article

Ferritin nanocages with spherical shells carry proteins or antigens that enable their use as highly efficient nanoreactors and nanocarriers. Mimicking the surface Spike (S) receptor-binding domain (RBD) from SARS-CoV-2, ferritin nanocages induce neutralizing antibody production or block viral entry. Herein, by implementing molecular dynamics simulation, we evaluate the efficiency in the interaction pattern (active or alternative sites) of H-ferritin displaying the 24 S RBDs with host-cell-receptor or monoclonal antibodies (mAbs; B38 or VVH-72). Our constructed nanocage targeted the receptor- or antibody-binding interfaces, suggesting that mAbs demonstrate an enhanced binding affinity with the RBD, with key interactions originating from its variable heavy chain. The S RBD interactions with ACE2 and B38 involved the same binding site but led to divergent dynamic responses. In particular, both B38 chains showed that asymmetric fluctuations had a major effect on their engagement with the Spike RBD. Although the receptor increased the binding affinity of VVH-72 for the RBD, the mAb structural orientation on the nanocage remained identical to its conformation when bound to the host receptor. Overall, our findings characterize the essential pharmacophore formed by Spike RBD residues over nanocage molecules, which mediates high-affinity interactions with either binding partner. Importantly, the ferritin-displayed RBD maintained native receptor and antibody binding profiles, positioning it as a promising scaffold for pre-fusion stabilization and protective RBD vaccine design. Full article

Infectious diseases have been treated using plants and their compounds for thousands of years. This knowledge has enabled modern techniques to identify specific antiviral remedies and to understand their molecular mechanism of action. Numerous active phytochemicals, such as alkaloids, terpenoids, polyphenols (phenolic acids, flavonoids, stilbenes, and lignans), coumarins, thiophenes, saponins, furyl compounds, small proteins, and peptides, are promising options for treating and preventing viral infections. It has been shown that plant-derived products can prevent or inhibit viral entry into and replication by host cells. Biotechnological advances have made it possible to engineer plants with an increased capacity for the production and accumulation of natural antiviral compounds. Plants can also be engineered to produce various types of antivirals (cytokines, antibodies, vaccines, and lectins). This study summarizes the current understanding of the antiviral activity of specific plant-derived metabolites, emphasizing their mechanisms of action and exploring the enormous potential of plants as biological factories. Full article

Alphaviruses engage a diverse array of attachment factors and receptors during viral entry, resulting in a broad host range and disease spectrum, and thus presenting them as a major global public health concern. The development of effective antivirals against these arboviruses relies on a comprehensive understanding of the molecular interplay between these viruses and host cell factors, as well as the wide range of immune responses that ensue following viral infection. In this review, we present the current understanding of the complex landscape of alphavirus interaction with attachment factors and entry receptors, some of which are characterized structurally, while others are characterized biochemically. Additionally, we provide an overview of the molecular bases of epitope recognition by neutralizing and non-neutralizing antibodies against alphaviruses, and how icosahedral symmetry influences these interactions, such as occupancy and neutralization potency. We further discuss the structural bases of epitope recognition of a few pan-alphavirus antibodies, their potential therapeutic implications, and offer future perspectives on the development of effective therapeutics against clinically relevant alphaviruses. Full article

The 2016 Zika virus (ZIKV) epidemic has largely subsided, but a key question remains. How did ZIKV evolve to become a virulent human pathogen compared to the virus of its original discovery? What specific virologic and pathologic changes contributed to increased pathogenicity in humans? Phylogenetic studies have identified two genetically distinct ZIKV, the African and Asian lineages, which differ in their pathogenicity. Previous studies including ours suggest that the envelope (E) protein plays a key role in viral entry, immune activation, and neuropathogenesis. This study aimed to further elucidate virologic and pathogenic differences between these lineages by assessing their ability to bind and replicate in host cells, induce apoptotic cell death, trigger inflammatory responses, and influence human neural progenitor cell (hNPC)-derived neurosphere formation. We compared a historic African ZIKV strain (MR766) with an epidemic Brazilian strain (BR15) and evaluated the effects of the E protein inhibitor quercetin-3-β-O-D-glucoside (Q3G) and an E protein-neutralizing antibody (AbII). Our results revealed distinct virologic properties and that MR766 exhibited stronger inhibition of neurosphere formation due to enhanced viral binding to neuronal SH-SY5Y cells, while BR15 infection triggered a heightened pro-inflammatory cytokine response with reduced viral binding. Chimeric virus studies suggested that the E protein likely influences viral binding, replication efficiency, immune activation, and neuropathogenesis. Notably, Q3G exhibited antiviral activities against both MR766 and BR15, whereas AbII preferentially inhibited MR766. These findings highlight the virological differences between ancestral and epidemic viral strains, as well as the critical role of E protein in viral permissiveness, immune response, and neuropathogenesis, providing insights for developing targeted antiviral strategies. Full article

Sleep deprivation impairs immune function, and melatonin has emerged as a key mediator in this process. This narrative review analyzes 50 studies published between 2000 and 2025 to determine the extent to which reduced melatonin synthesis contributes to immune dysregulation. Consistent sleep loss lowers melatonin levels, which correlates with elevated proinflammatory cytokines (e.g., IL-6 and TNF-α), increased oxidative stress, and reduced immune cell activity, including that of natural killer (NK) cells and CD4+ lymphocytes. Melatonin regulates immune pathways, including NF-κB signaling. It also supports mitochondrial health and helps maintain gut barrier integrity. These effects are particularly relevant in vulnerable populations, including older adults and shift workers. Experimental findings also highlight melatonin’s therapeutic potential in infections like SARS-CoV-2, where it modulates inflammatory responses and viral entry mechanisms. Despite the heterogeneity of study methodologies, a consistent correlation emerges between circadian disruption, melatonin suppression, and immune imbalance. These findings underscore melatonin’s dual role as a chronobiotic and immunomodulator. Addressing sleep loss and considering melatonin-based interventions may help restore immune homeostasis. More clinical trials are needed to determine the best dosing, long-term efficacy, and population-specific strategies for supplementation. Promoting healthy sleep is crucial for preventing chronic inflammation and diseases associated with immune dysfunction. Full article

Rabies, a viral encephalitis caused by rabies virus (RABV), is 100% fatal upon the onset of symptoms. Effective post-exposure prophylaxis (PEP) measures are available, but they are often difficult to access in low-income countries. WHO estimates about 59,000 deaths due to rabies globally, and the majority are contributed by developing countries. Hence, developing drugs for the treatment of post-symptomatic rabies is an urgent and unmet demand. It is worth noting that previous efforts regarding antiviral strategies, such as small-interfering RNA, antibodies and small-molecule inhibitors, against the rabies virus have failed to show efficacy in pre-clinical studies, especially when the virus has reached the central nervous system (CNS). Therefore, drug repurposing seems to be an alternative tool for the development of new anti-rabies drugs. We validated and used a high-throughput, FITC-conjugated antibody-based flow cytometry assay to expedite the identification of repurposable new drug candidates against the RABV. The assay was validated using ribavirin and salinomycin as reference compounds, which showed EC50 values of 10.08 µM and 0.07 µM, respectively. We screened a SelleckChem library comprising 3035 FDA-approved compounds against RABV (CVS-11) at 10 µM concentration. Five compounds (clofazimine, tiamulin, difloxacin, harringtonine and homoharringtonine) were active against RABV, with greater than 90% inhibition. Homoharringtonine (HHT) identified in the present study is active against laboratory-adapted RABV (CVS-11) and clinical isolates of RABV, with an average EC50 of 0.3 µM in both BHK-21 and Neuro-2a cell lines and exhibits post-entry inhibition. Full article

Patients undergoing peritoneal dialysis (PD) represent a uniquely vulnerable population due to intrinsic immunological dysfunction and a high prevalence of comorbid conditions. This review examines the complex interplay between natural and vaccine-induced immune responses to SARS-CoV-2 in this group, focusing on viral entry, immune activation, and immune evasion mechanisms. Particular attention is given to the impaired cellular and humoral responses seen in PD patients, including reduced T-cell function, diminished antibody production, and abnormal cytokine signaling, all of which contribute to an elevated risk of severe COVID-19 outcomes. The immunogenicity and clinical efficacy of various vaccine platforms, including inactivated, vector-based, and mRNA formulations, are critically assessed, with an emphasis on the role of booster doses in enhancing protection amid waning immunity and evolving viral variants. Furthermore, the review highlights the advantages of PD as a home-based modality that is compatible with telemedicine and may reduce the risk of viral exposure. These insights underscore the importance of developing individualized vaccination strategies, maintaining close immunological surveillance, and implementing innovative dialysis care approaches to improve clinical outcomes during the ongoing pandemic and future public health crises. Tailored booster strategies and telemedicine-integrated care models are essential for improving outcomes in this high-risk population. Full article