Objective To explore the effect of the knockdown of transmembrane 9 superfamily protein member 2 (TM9SF2) on the replication of vesicular stomatitis virus (VSV), and investigate its role in the mechanism of antiviral innate immunity. Methods Small interfering RNA (siRNA) was used to knock down the TM9SF2 gene in human non-small cell lung cancer A549 cells. The CCK-8 method was used to assess cell proliferation. A VSV-green fluorescent protein (VSV-GFP) infected cell model was established. The plaque assay was used to measure the viral titer in the supernatant. RT-qPCR and Western blotting were employed to quantify the mRNA and protein levels of VSV genome replication in A549 cells following VSV infection, as well as the expression of interferon β (IFN-β) mRNA and interferon regulatory factor 3 (IRF3) protein phosphorylation following polyinosinic-polycytidylic acid (poly(I:C)) stimulation. Results Compared to the negative control, the knockdown of TM9SF2 exhibited a significant effect, with no observed impact on A549 cell proliferation. The VSV-GFP infected A549 cell model was successfully established. After viral stimulation, fluorescence intensity was reduced following TM9SF2 knockdown, and the mRNA and protein levels of VSV were significantly downregulated. The viral titer of VSV was decreased. After poly(I:C) stimulation, TM9SF2 knockdown significantly upregulated the mRNA level of IFN-β and the phosphorylation level of IRF3 protein. Conclusion The knockdown of TM9SF2 inhibits the replication of vesicular stomatitis virus, and positively regulates the type I interferon signaling pathway, thus enhancing the host's antiviral innate immune response.
Humans ; Virus Replication/genetics* ; Signal Transduction ; Membrane Proteins/metabolism* ; A549 Cells ; Vesiculovirus/physiology* ; Interferon-beta/metabolism* ; Interferon Regulatory Factor-3/genetics* ; Interferon Type I/metabolism* ; Vesicular Stomatitis/immunology* ; Gene Knockdown Techniques ; Vesicular stomatitis Indiana virus/physiology* ; RNA, Small Interfering/genetics*

Virus-induced senescence (VIS) is a significant biological phenomenon, which is associated with declining immune function, accelerating aging process and causing aging-related diseases. A variety of common viruses, including RNA viruses (such as SARS-CoV-2), DNA viruses (such as herpesviruses and hepatitis B virus), and prions can cause VIS in host cells. The primary mechanisms include abnormal activation of the cGAS-STING signaling pathway, DNA damage response, and potential correlations with the integrated stress response due to intracellular phase separation. Viral infection and cellular senescence influence each other: cellular senescence serves as a defense to restrict viral replication and transmission, while some viruses exploit cellular senescence to enhance their infectivity and replication. Understanding the mechanisms of VIS is conducive to the development of therapeutic strategies for viral infections and promotion of healthy aging. However, there is lack of research on therapeutic targets and drug development in this field so far. Although senolytics may be effective for anti-senescent cells therapy, their efficacy for VIS needs evidence from further clinical trials. This article reviews the research progress on the connection between viral infection and cellular senescence, to provide insights for the prevention and treatment of aging related diseases.
Humans ; Cellular Senescence/physiology* ; Virus Diseases/physiopathology* ; Signal Transduction ; Nucleotidyltransferases/metabolism* ; DNA Damage ; Virus Replication ; COVID-19 ; Membrane Proteins/metabolism* ; SARS-CoV-2

Paramyxoviruses are important respiratory pathogens with substantial clinical relevance in pediatric infectious diseases. During infection, multiple forms of programmed cell death (PCD) may be induced, and this plays pivotal roles in viral replication, dissemination, and host immune responses, thereby profoundly influencing the viral life cycle and disease progression. On one hand, PCD facilitates the clearance of infected cells, restricts viral spread, and activates host immune defenses, thereby enhancing antiviral immunity. On the other hand, excessive or dysregulated cell death may lead to tissue damage and immune imbalance, creating a microenvironment conducive to viral replication and exacerbating disease severity. For instance, apoptosis-mediated by both extrinsic and intrinsic pathways-contributes to infection control but may also be hijacked by viruses to promote dissemination. Pyroptosis, driven by inflammasome activation, triggers lytic cell death and the release of pro-inflammatory cytokines. Necroptosis, mediated by the RIPK1-RIPK3-MLKL signaling axis, and pyroptosis both amplify innate immune responses but may concurrently induce inflammatory dysregulation. Immunogenic cell death (ICD), characterized by the release of damage-associated molecular patterns and neoantigens, activates antigen-specific immune responses and holds therapeutic potential for antiviral and antitumor interventions. Emerging evidence suggests that ferroptosis, through the modulation of iron metabolism and associated transporters, may also participate in viral replication and infected cell clearance. This review comprehensively summarizes the roles of apoptosis, pyroptosis, necroptosis, ICD, and ferroptosis in paramyxovirus infection, aiming to deepen the understanding of paramyxovirus pathogenesis and to provide insights for developing novel antiviral strategies.
Humans ; Paramyxoviridae Infections/pathology* ; Pyroptosis ; Apoptosis ; Virus Replication ; Necroptosis ; Inflammasomes ; Immunity, Innate ; Immunogenic Cell Death ; Paramyxoviridae/physiology* ; Signal Transduction

The study aims to investigate the impacts of prolyl oligopeptidase (POP) on the replication of foot-and-mouth disease virus (FMDV) in BHK-21 cells. Firstly, the effects of FMDV replication on POP expression in BHK-21 cells were analyzed by Western blotting and Real-time reverse transcription polymerase chain reaction (RT-qPCR). Secondly, a eukaryotic expression plasmid for POP was constructed, and the effects of POP overexpression on the replication of two different serotypes of FMDV were assessed by Western blotting, RT-qPCR, and virus titer assays. Thirdly, specific small interfering RNAs (siRNAs) targeting POP were synthesized, and their efficiency in interfering with endogenous POP expression was identified by RT-qPCR. The impacts of downregulating endogenous POP expression on FMDV replication were further evaluated by Western blotting, RT-qPCR, and virus titer assays. The results indicated that FMDV infection did not significantly affect POP expression in BHK-21 cells. Overexpression of POP dose-dependently enhanced the replication of both FMDV/O and FMDV/A serotypes. Conversely, siRNA-mediated downregulation of endogenous POP expression markedly suppressed FMDV/O replication. This study is the first to demonstrated that the role of the host POP protein in promoting FMDV replication in BHK-21 cells, thereby providing a critical theoretical foundation and potential molecular targets for developing efficient candidate cell strains for foot-and-mouth disease inactivated vaccines.
Foot-and-Mouth Disease Virus/genetics* ; Virus Replication/genetics* ; Prolyl Oligopeptidases ; Serine Endopeptidases/physiology* ; Animals ; Cell Line ; RNA, Small Interfering/genetics* ; Foot-and-Mouth Disease/virology* ; Cricetinae

The Ebola virus (EBOV), a member of the Filoviridae family, is a highly pathogenic agent responsible for severe hemorrhagic fever in humans. Understanding the molecular mechanisms governing its replication is critical for developing effective antiviral strategies. VP35-TurboID immunosuppression coupled with quantitative mass spectrometry identified Septin9, the host GTP-binding protein which played a role in cytoskeletal regulation, as a novel interactor of VP35. Western blotting and Far-Western blotting confirmed the direct interaction and demonstrated that the C-terminal region of VP35 was the critical binding domain. Functionally, EBOV replication as well as the formation of viral inclusion bodies (VIBs) was demonstrated to be significantly suppressed by Septin9 knockdown and depletion, as shown by the EBOV minigenome (EBOV MG) and the transcription- and replication-competent virus-like particles (trVLPs) system. This study reveals that VP35 engages in a specific interaction with the GTP-binding protein Septin9, thereby impeding EBOV replication through the disruption of inclusion bodies. The overarching objective of this study is to significantly enhance our understanding about the pathogenic mechanism of EBOV and offer a robust theoretical foundation and solid empirical support for the formulation of innovative therapeutic strategies against EBOV.
Virus Replication/physiology* ; Septins/physiology* ; Humans ; Ebolavirus/physiology* ; Inclusion Bodies, Viral/metabolism* ; Viral Regulatory and Accessory Proteins/metabolism* ; Hemorrhagic Fever, Ebola/virology*

This work aims to explore the effect of glycolysis on the replication of porcine reproductive and respiratory syndrome virus (PRRSV) in porcine alveolar macrophages (PAMs). The changes of glucose metabolism, PRRSV protein levels, PRRSV titers, and the relative expression levels of genes and proteins in PAMs were analyzed by ELISA, qPCR, virus titration, and Western blotting after PRRSV infection. The effect of hypoxia-inducible factor-1α (HIF-1α) on PRRSV replication was subsequently assessed by specific siRNAs targeting to HIF-1α. The results showed that PRRSV infection enhanced glycolysis, elevated the levels of glucose uptake and lactate in the supernatant (P<0.05 and 0.01, respectively), reduced ATP production (P<0.05), and up-regulated the expression of hexokinase 2 (HK2), 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3), and pyruvate kinase isozyme type M2 (PKM2) in PAMs (P<0.05 and 0.01, respectively). Glycolysis inhibitors down-regulated the expression of PRRSV proteins and reduced virus titers (P<0.01). The knockdown of HIF-1α by siRNAs inhibited glycolysis and lowered PRRSV titers (P<0.05). In addition, the interferon pathways inhibited by PRRSV infection were reversed by the inhibition of glycolysis. These findings may facilitate further investigation of the role of glycolysis in PRRSV replication.
Porcine respiratory and reproductive syndrome virus/physiology* ; Glycolysis ; Swine ; Animals ; Virus Replication ; Hypoxia-Inducible Factor 1, alpha Subunit/genetics* ; Macrophages, Alveolar/metabolism* ; Porcine Reproductive and Respiratory Syndrome/virology* ; Cells, Cultured ; RNA, Small Interfering/genetics*

The coronavirus disease 2019 (COVID-19) pandemic is caused by infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is spread primary via respiratory droplets and infects the lungs. Currently widely used cell lines and animals are unable to accurately mimic human physiological conditions because of the abnormal status of cell lines (transformed or cancer cells) and species differences between animals and humans. Organoids are stem cell-derived self-organized three-dimensional culture in vitro and model the physiological conditions of natural organs. Here we showed that SARS-CoV-2 infected and extensively replicated in human embryonic stem cells (hESCs)-derived lung organoids, including airway and alveolar organoids which covered the complete infection and spread route for SARS-CoV-2 within lungs. The infected cells were ciliated, club, and alveolar type 2 (AT2) cells, which were sequentially located from the proximal to the distal airway and terminal alveoli, respectively. Additionally, RNA-seq revealed early cell response to virus infection including an unexpected downregulation of the metabolic processes, especially lipid metabolism, in addition to the well-known upregulation of immune response. Further, Remdesivir and a human neutralizing antibody potently inhibited SARS-CoV-2 replication in lung organoids. Therefore, human lung organoids can serve as a pathophysiological model to investigate the underlying mechanism of SARS-CoV-2 infection and to discover and test therapeutic drugs for COVID-19.
Adenosine Monophosphate/therapeutic use* ; Alanine/therapeutic use* ; Alveolar Epithelial Cells/virology* ; Antibodies, Neutralizing/therapeutic use* ; COVID-19/virology* ; Down-Regulation ; Drug Discovery ; Human Embryonic Stem Cells/metabolism* ; Humans ; Immunity ; Lipid Metabolism ; Lung/virology* ; RNA, Viral/metabolism* ; SARS-CoV-2/physiology* ; Virus Replication/drug effects*

Adaptation, Physiological ; Adenosine Monophosphate ; administration & dosage ; analogs & derivatives ; pharmacology ; therapeutic use ; Administration, Intranasal ; Alanine ; administration & dosage ; analogs & derivatives ; pharmacology ; therapeutic use ; Animals ; Betacoronavirus ; genetics ; physiology ; Chlorocebus aethiops ; Coronavirus Infections ; drug therapy ; virology ; Disease Models, Animal ; Female ; Host Specificity ; genetics ; Lung ; pathology ; virology ; Male ; Mice ; Mice, Inbred BALB C ; Mice, Inbred C57BL ; Mutation, Missense ; Nasal Mucosa ; virology ; Pandemics ; Pneumonia, Viral ; drug therapy ; virology ; RNA, Viral ; administration & dosage ; genetics ; Turbinates ; virology ; Vero Cells ; Viral Load ; Virus Replication

The three known human highly pathogenic coronaviruses are severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus, (MERS-CoV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Human highly pathogenic coronaviruses are composed of non-structural proteins, structural proteins and accessory proteins. Viral particles recognize host receptors via spike glycoprotein (S protein), enter host cells by membrane fusion, replicate in host cells through large replication-transcription complexes, and promote proliferation by interfering with and suppressing the host's immune response. Human highly pathogenic coronaviruses are hosted by humans and vertebrates. Viral particles are transmitted through droplets, contact and aerosols or likely through digestive tract, urine, eyes and other routes. This review discusses the mechanisms of proliferation and transmission of highly pathogenic human coronaviruses based on the results of existing research, providing basis for future study on interrupting the transmission and pathogenicity of human highly pathogenic coronaviruses.
Animals ; Betacoronavirus ; physiology ; Coronavirus Infections ; immunology ; transmission ; virology ; Humans ; Middle East Respiratory Syndrome Coronavirus ; physiology ; Pandemics ; Pneumonia, Viral ; immunology ; transmission ; virology ; SARS Virus ; physiology ; Virus Replication ; physiology

Emerging and re-emerging RNA viruses occasionally cause epidemics and pandemics worldwide, such as the on-going outbreak of the novel coronavirus SARS-CoV-2. Herein, we identified two potent inhibitors of human DHODH, S312 and S416, with favorable drug-likeness and pharmacokinetic profiles, which all showed broad-spectrum antiviral effects against various RNA viruses, including influenza A virus, Zika virus, Ebola virus, and particularly against SARS-CoV-2. Notably, S416 is reported to be the most potent inhibitor so far with an EC of 17 nmol/L and an SI value of 10,505.88 in infected cells. Our results are the first to validate that DHODH is an attractive host target through high antiviral efficacy in vivo and low virus replication in DHODH knock-out cells. This work demonstrates that both S312/S416 and old drugs (Leflunomide/Teriflunomide) with dual actions of antiviral and immuno-regulation may have clinical potentials to cure SARS-CoV-2 or other RNA viruses circulating worldwide, no matter such viruses are mutated or not.
Animals ; Antiviral Agents ; pharmacology ; therapeutic use ; Betacoronavirus ; drug effects ; physiology ; Binding Sites ; drug effects ; Cell Line ; Coronavirus Infections ; drug therapy ; virology ; Crotonates ; pharmacology ; Cytokine Release Syndrome ; drug therapy ; Drug Evaluation, Preclinical ; Gene Knockout Techniques ; Humans ; Influenza A virus ; drug effects ; Leflunomide ; pharmacology ; Mice ; Mice, Inbred BALB C ; Orthomyxoviridae Infections ; drug therapy ; Oseltamivir ; therapeutic use ; Oxidoreductases ; antagonists & inhibitors ; metabolism ; Pandemics ; Pneumonia, Viral ; drug therapy ; virology ; Protein Binding ; drug effects ; Pyrimidines ; biosynthesis ; RNA Viruses ; drug effects ; physiology ; Structure-Activity Relationship ; Toluidines ; pharmacology ; Ubiquinone ; metabolism ; Virus Replication ; drug effects