Search Results (39)

Viral oncolysis is considered a promising cancer treatment method because of its good tolerability and durable anti-tumor effects. Compared with other oncolytic viruses, Newcastle disease virus (NDV) has some distinct advantages. As an RNA virus, NDV does not recombine with the host genome, making it safer compared with DNA viruses and retroviruses; NDV can induce syncytium formation, allowing the virus to spread among cells without exposure to host neutralizing antibodies; and its genome adheres to the hexamer genetic code rule (genome length as a multiple of six nucleotides), ensuring accurate replication, low recombination rates, and high genetic stability. Although wild-type NDV has a killing effect on various tumor cells, its oncolytic effect and working mechanism are diverse, increasing the complexity of generating engineered oncolytic viruses with NDV. This study aims to employ whole-genome CRISPR-Cas9 knockout screening and RNA sequencing to identify putative key regulatory factors involved in the interaction between NDV and human colon cancer HCT116 cells and map their global interaction networks. The results suggests that NDV infection disrupts cellular homeostasis, thereby exerting oncolytic effects by inhibiting cell metabolism and proliferation. Meanwhile, the antiviral immune response triggered by NDV infection, along with the activation of anti-apoptotic signaling pathways, may be responsible for the limited oncolytic efficacy of NDV against HCT116 cells. These findings not only enhance our understanding of the oncolytic mechanism of NDV against colonic carcinoma but also provide potential strategies and targets for the development of NDV-based engineered oncolytic viruses. Full article

The neurological basis of consciousness remains unknown despite innumerable theories proposed for over a century. The major obstacle is that empirical studies demonstrate that all sensory information is subdivided and parcellated as it is processed within the brain. A central region where such diverse information combines to form conscious expression has not been identified. A novel hypothesis was introduced over two decades ago that proposed astrocytes, with their ability to interconnect to form a global syncytium within the neocortex, are the locus of consciousness based on their ability to integrate synaptic signals. However, it was criticized because intercellular calcium waves, which are initiated by synaptic activity, are too slow to contribute to consciousness but ideal for memory formation. Although astrocytes are known to exhibit rapid electrical responses in active sensory pathways (e.g., vision), it was technically impossible to determine electrical activity within the astroglia syncytium because of the challenge of separating syncytial electrical responses from simultaneous neuronal electrical activity. Therefore, research on astroglia syncytial electrical activity lagged for over sixty years, until recently, when an ingenuous technique was developed to eliminate neuronal electrical interference. These technical advances have demonstrated that the astroglia syncytium, although massive and occupying the entire neocortex, is isoelectric with minimal impedance. Most importantly, the speed of electrical conductance within the syncytium is as rapid as that of neural networks. Therefore, the astroglia syncytium is theoretically capable of transmitting integrated local synaptic signaling globally throughout the entire neocortex to bind all functional areas of the brain in a timeframe required for consciousness. Full article

Members of the family Orthoherpesviridae employs two distinct transmission modes: free virion release and cell-to-cell transmission. The latter enables immune evasion through multiple mechanisms, facilitating infections in skin, mucosa, and neural tissues. This review synthesizes current knowledge on human herpesvirus cell-to-cell transmission mechanisms, including syncytium formation, tight junction exploitation, exosomal transfer, and tunneling nanotube utilization. We analyze how these strategies enhance infection efficiency, evade immune surveillance, and augment pathogenicity. Furthermore, we discuss recent intervention strategies targeting cell-to-cell transmission, including the development of monoclonal antibodies, antiviral drugs, and vaccines. These inights provide a theoretical foundation for developing novel approaches against human herpesvirus infections. Full article

Nipah virus (NiV) is known to be a highly pathogenic zoonotic virus, which is included in the World Health Organization Research & Development Blueprint list of priority diseases with up to 70% mortality rate. Due to its high pathogenicity and outbreak potency, a therapeutic countermeasure against NiV is urgently needed. As NiV needs to be handled within a Biological Safety Level (BSL) 4 facility, we had developed a safe drug screening platform utilizing a baculovirus expression vector system (BEVS) based on a NiV-induced syncytium formation that could be handled within a BSL-1 facility. To reconstruct the NiV-induced syncytium formation in BEVS, two baculoviruses were generated to express recombinant proteins that are responsible for inducing the syncytium formation, including one baculovirus exhibiting co-expressed NiV fusion protein (NiV-F) and NiV attachment glycoprotein (NiV-G) and another exhibiting human EphrinB2 protein. Interestingly, syncytium formation was observed in infected insect cells when the medium was modified to have a lower pH level and supplemented with cholesterol. Fusion inhibitory properties of several compounds, such as phytochemicals and a polysulfonated naphthylamine compound, were evaluated using this platform. Among these compounds, suramin showed the highest fusion inhibitory activity against NiV-induced syncytium in the baculovirus expression system. Moreover, our in silico results provide a molecular-level glimpse of suramin’s interaction with NiV-G’s central hole and EphrinB2’s G-H loop, which could be the possible reason for its fusion inhibitory activity. Full article

Porcine epidemic diarrhea (PED), caused by the porcine epidemic diarrhea virus (PEDV), emerges annually in several Asian countries. Its major symptoms include watery diarrhea, vomiting, anorexia, and dehydration. PED outbreaks incur significant economic losses. The efficacy of vaccines is limited by viral mutations and insufficient intestinal mucosal immunity. Therefore, new vaccines against these recent variants are urgently needed. Herein, we isolated and genetically characterized a novel Korean PEDV strain using NGS. Comparative genomic analysis demonstrated that the CKK1-1 strain belonged to genogroup 2. The isolated strain was cultured in sodium-glycochenodeoxycholic acid for 180 passages. Typically, PEDV isolation and passage require proteases, such as trypsin. However, the CKK1-1 strain adapted to this atypical culture condition, achieving a high titer of 8.83 ± 0.14 log TCID₅₀/mL. In vitro biological analysis revealed no cell syncytium formation without trypsin; however, a cell-lysis-type cytopathic effect was noted. Notably, pathogenicity evaluation showed that CKK1-1 p0 exhibited naturally weakened virulence in five-day-old piglets, while piglets administered with CKK1-1 p180 exhibited 100% survival and reduced clinical symptoms. Collectively, our data demonstrate that this Korean PEDV strain, attenuated through atypical culture conditions with Na-glycochenodeoxycholic acid, has potential as a vaccine candidate, providing valuable insights into the genetic variation in and pathogenicity of PEDV. Full article

Acanthocephalans are dioecious parasites that gain sexual maturity in the alimentary canal of their definitive hosts (gnathostome vertebrates). This initial survey by light and transmission electron microscopy was conducted on the functional organization of the ovarian balls and uterine bell in mature females and on Saefftigen’s pouch and the copulatory bursa in males. We studied these structures via the example of Centrorhynchus globocaudatus (Palaeacanthocephala) in Falco tinnunculus and Buteo buteo, from the Province of Ferrara (Northern Italy). Our study confirms that the ovarian balls have surface microvilli and consist of a multinucleate supporting syncytium and a cellular region with oogonial syncytium, single germ cells, zygotes, and shelled eggs. Germ cells are embedded in the supporting syncytium. The ultrastructural features of these components and data on fertilization, shell formation, and release from the ovarian ball, alongside insights into the likely egg sorting function of the uterine bell, are provided. We also present light and electron microscopy observations of Saefftigen’s pouch and a suggestion regarding its hydrostatic functioning in the eversion of the copulatory bursa. Full article

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the novel coronavirus responsible for the coronavirus disease 2019 (COVID-19) pandemic, represents a serious threat to public health. The spike (S) glycoprotein of SARS-CoV-2 mediates viral entry into host cells and is heavily glycosylated. In this study, we systemically analyzed the roles of 22 putative N-linked glycans in SARS-CoV-2 S protein expression, membrane fusion, viral entry, and stability. Using the α-glycosidase inhibitors castanospermine and NB-DNJ, we confirmed that disruption of N-linked glycosylation blocked the maturation of the S protein, leading to the impairment of S protein-mediated membrane fusion. Single-amino-acid substitution of each of the 22 N-linked glycosylation sites with glutamine revealed that 9 out of the 22 N-linked glycosylation sites were critical for S protein folding and maturation. Thus, substitution at these sites resulted in reduced S protein-mediated cell–cell fusion and viral entry. Notably, the N1074Q mutation markedly affected S protein stability and induced significant receptor-independent syncytium (RIS) formation in HEK293T/hACE2-KO cells. Additionally, the removal of the furin cleavage site partially compensated for the instability induced by the N1074Q mutation. Although the corresponding mutation in the SARS-CoV S protein (N1056Q) did not induce RIS in HEK293T cells, the N669Q and N1080Q mutants exhibited increased fusogenic activity and did induce syncytium formation in HEK293T cells. Therefore, N-glycans on the SARS-CoV and SARS-CoV-2 S2 subunits are highly important for maintaining the pre-fusion state of the S protein. This study revealed the critical roles of N-glycans in S protein maturation and stability, information that has implications for the design of vaccines and antiviral strategies. Full article

Syncytin-1 and -2 are glycoproteins encoded by human endogenous retrovirus (hERV) that, through their fusogenic properties, are needed for the formation of the placental syncytiotrophoblast. Previous studies suggested that these proteins, in addition to the EnvP(b) envelope protein, are also involved in other cell fusion events. Since galectin-1 is a β-galactoside-binding protein associated with cytotrophoblast fusion during placental development, we previously tested its effect on Syncytin-mediated cell fusion and showed that this protein differently modulates the fusogenic potential of Syncytin-1 and -2. Herein, we were interested in comparing the impact of galectin-1 on hERV envelope proteins in different cellular contexts. Using a syncytium assay, we first demonstrated that galectin-1 increased the fusion of Syncytin-2- and EnvP(b)-expressing cells. We then tested the infectivity of Syncytin-1 and -2 vs. VSV-G-pseudotyped viruses toward Cos-7 and various human cell lines. In the presence of galectin-1, infection of Syncytin-2-pseudotyped viruses augmented for all cell lines. In contrast, the impact of galectin-1 on the infectivity of Syncytin-1-pseudotyped viruses varied, being cell- and dose-dependent. In this study, we report the functional associations between three hERV envelope proteins and galectin-1, which should provide information on the fusogenic activity of these proteins in the placenta and other biological and pathological processes. Full article

Human herpes simplex virus (HSV), a double-stranded DNA virus belonging to the Herpesviridae family and alpha herpesvirus subfamily, is one of the most epidemic pathogens in the population. Cell-to-cell spread is a special intercellular transmission mechanism of HSV that indicates the virulence of this virus. Through numerous studies on mutant HSV strains, many viral and host proteins involved in this process have been identified; however, the mechanisms remain poorly understood. Here, we evaluated the effect of the membrane protein genes US7 and UL56 on cell-to-cell spread in vitro between two HSV-1 (HB94 and HN19) strains using a plaque assay, syncytium formation assay, and the CRISPR/Cas9 technique. US7 knockout resulted in the inhibition of viral cell-to-cell spread; additionally, glycoprotein I (US7) of the HB94 strain was found to promote cell-to-cell spread compared to that of the HN19 strain. UL56 knockout did not affect plaque size and syncytium formation; however, the gene product of UL56 from the HN19 strain inhibited plaque formation and membrane infusion. This study presents preliminary evidence of the functions of US7 and UL56 in the cell-to-cell spread of HSV-1, which will provide important clues to reveal the mechanisms of cell-to-cell spread, and contributes to the clinical drugs development. Full article

This article presents the results of virological and genetic studies of an isolate of caprine arthritis encephalitis (CAE) virus from the republic of Mordovia, Russian Federation. The isolate was found during monitoring studies of goat blood samples for the viral genome, and the presence of antibodies to lentiviruses was detected. According to the recommendation of the OIE, the positive result of PCR was confirmed with nucleotide sequencing. It was found that the obtained nucleotide sequence is identical to the genome of small ruminant lentiviruses presented in the GenBank database. Phylogenetic analysis showed that the isolate “Mordovia-2018” was included in the same cluster with an isolate from the Tver region of the Russian Federation detected in 2008. The sequence of the fragment of the env-gene of the isolate from the republic of Mordovia is available in GenBank under the number MN186380.1. To isolate the virus, a fraction of peripheral blood monocyte cells from the animal’s blood was added to a monolayer of lamb synovial membrane cell culture, and ten passages were carried out. The first manifestations of the cytopathic effect were observed after the third passage on the eighth day of cultivation in the form of single large cells of irregular shape with 5–7 nuclei. At the seventh passage, multiple syncytium with 7–12 nuclei were observed. At subsequent passage levels, the formation of syncytium containing more than 10–14 nuclei was observed. Full article

The S2 subunit serves a crucial role in infectious bronchitis virus (IBV) infection, particularly in facilitating membrane fusion. Using reverse genetic techniques, mutant strains of the S2 locus exhibited substantially different syncytium-forming abilities in chick embryonic kidney cells. To determine the precise formation mechanism of syncytium, we demonstrated the co-ordinated role of Abl2 and its mediated cytoskeletal regulatory pathway within the S2 subunit. Using a combination of fluorescence quantification, RNA silencing, and protein profiling techniques, the functional role of S2 subunits in IBV-infected cells was exhaustively determined. Our findings imply that Abl2 is not the primary cytoskeletal regulator, the viral S2 component is involved in indirect regulation, and the three different viral strains activate various cytoskeletal regulatory pathways through Abl2. CRK, CRKL, ABI1, NCKAP1, and ENAH also play a role in cytoskeleton regulation. Our research provides a point of reference for the development of an intracellular regulatory network for the S2 subunit and a foundation for the rational design of antiviral drug targets against Abl2. Full article

Viruses can induce the fusion of infected and neighboring cells, leading to the formation of syncytia. Cell–cell fusion is mediated by viral fusion proteins on the plasma membrane of infected cells that interact with cellular receptors on neighboring cells. Viruses use this mechanism to spread rapidly to adjacent cells or escape host immunity. For some viruses, syncytium formation is a hallmark of infection and a known pathogenicity factor. For others, the role of syncytium formation in viral dissemination and pathogenicity remains poorly understood. Human cytomegalovirus (HCMV) is an important cause of morbidity and mortality in transplant patients and the leading cause of congenital infections. Clinical HCMV isolates have broad cell tropism but differ in their ability to induce cell–cell fusions, and little is known about the molecular determinants. We developed a system to analyze HCMV glycoprotein B (gB) variants in a defined genetic background. HCMV strains TB40/E and TR were used as vectors to compare the fusogenicity of six gB variants from congenitally infected fetuses with those from three laboratory strains. Five of them conferred the ability to induce the fusion of MRC-5 human embryonic lung fibroblasts to one or both backbone strains, as determined by a split GFP–luciferase reporter system. The same gB variants were not sufficient to induce syncytia in infected ARPE-19 epithelial cells, suggesting that additional factors are involved. The system described here allows a systematic comparison of the fusogenicity of viral envelope glycoproteins and may help to clarify whether fusion-promoting variants are associated with increased pathogenicity. Full article

Endosperm development in barley starts with the formation of a multinucleate syncytium, followed by cellularization in the ventral part of the syncytium generating endosperm transfer cells (ETCs) as first differentiating subdomain, whereas aleurone (AL) cells will originate from the periphery of the enclosing syncytium. Positional signaling in the syncytial stage determines cell identity in the cereal endosperm. Here, we performed a morphological analysis and employed laser capture microdissection (LCM)-based RNA-seq of the ETC region and the peripheral syncytium at the onset of cellularization to dissect developmental and regulatory programs directing cell specification in the early endosperm. Transcriptome data revealed domain-specific characteristics and identified two-component signaling (TCS) and hormone activities (auxin, ABA, ethylene) with associated transcription factors (TFs) as the main regulatory links for ETC specification. On the contrary, differential hormone signaling (canonical auxin, gibberellins, cytokinin) and interacting TFs control the duration of the syncytial phase and timing of cellularization of AL initials. Domain-specific expression of candidate genes was validated by in situ hybridization and putative protein–protein interactions were confirmed by split-YFP assays. This is the first transcriptome analysis dissecting syncytial subdomains of cereal seeds and provides an essential framework for initial endosperm differentiation in barley, which is likely also valuable for comparative studies with other cereal crops. Full article

Gap junctions (GJs) formed by connexins (Cxs) play an important role in the intercellular communication within most body tissues. In this paper, we focus on GJs and Cxs present in skeletal tissues. Cx43 is the most expressed connexin, participating in the formation of both GJs for intercellular communication and hemichannels (HCs) for communication with the external environment. Through GJs in long dendritic-like cytoplasmic processes, osteocytes embedded in deep lacunae are able to form a functional syncytium not only with neighboring osteocytes but also with bone cells located at the bone surface, despite the surrounding mineralized matrix. The functional syncytium allows a coordinated cell activity through the wide propagation of calcium waves, nutrients and anabolic and/or catabolic factors. Acting as mechanosensors, osteocytes are able to transduce mechanical stimuli into biological signals that spread through the syncytium to orchestrate bone remodeling. The fundamental role of Cxs and GJs is confirmed by a plethora of investigations that have highlighted how up- and downregulation of Cxs and GJs critically influence skeletal development and cartilage functions. A better knowledge of GJ and Cx mechanisms in physiological and pathological conditions might help in developing therapeutic approaches aimed at the treatment of human skeletal system disorders. Full article

The frequent emergence of SARS-CoV-2 variants thwarts the prophylactic and therapeutic countermeasures confronting COVID-19. Among them, the Delta variant attracts widespread attention due to its high pathogenicity and fatality rate compared with other variants. However, with the emergence of new variants, studies on Delta variants have been gradually weakened and ignored. In this study, a replication-competent recombinant virus carrying the S protein of the SARS-CoV-2 Delta variant was established based on the vesicular stomatitis virus (VSV), which presented a safe alternative model for studying the Delta variant. The recombinant virus showed a replication advantage in Vero E6 cells, and the viral titers reach 10^7.3 TCID₅₀/mL at 36 h post-inoculation. In the VSV-vectored recombinant platform, the spike proteins of the Delta variant mediated higher fusion activity and syncytium formation than the wild-type strain. Notably, the recombinant virus was avirulent in BALB/c mice, Syrian hamsters, 3-day ICR suckling mice, and IFNAR/GR^−/− mice. It induced protective neutralizing antibodies in rodents, and protected the Syrian hamsters against the SARS-CoV-2 Delta variant infection. Meanwhile, the eGFP reporter of recombinant virus enabled the visual assay of neutralizing antibodies. Therefore, the recombinant virus could be a safe and convenient surrogate tool for authentic SARS-CoV-2. This efficient and reliable model has significant potential for research on viral-host interactions, epidemiological investigation of serum-neutralizing antibodies, and vaccine development. Full article