Virus-induced Immune Responses Research Articles

Effects of virus-induced immunogenic cues on oncolytic virotherapy

Oncolytic virotherapy is a promising form of cancer treatment that uses viruses to infect and kill cancer cells. In addition to their direct effects on cancer cells, the viruses stimulate various immune responses partly directed against the tumour. Efforts are made to genetically engineer oncolytic viruses to enhance their immunogenic potential. However, the interplay between tumour growth, viral infection, and immune responses is complex and not fully understood, leading to variable and sometimes counterintuitive therapeutic outcomes. Here, we employ a spatio-temporal model to shed more light on this interplay. We investigate systematically how the properties of virus-induced immunogenic signals (their half-life, rate of spread, and potential to promote T-cell-mediated cytotoxicity) affect the therapeutic outcome. Our simulations reveal that strong immunogenic signals, combined with faster diffusion rates, improve the spread of immune activation, leading to better tumour eradication. However, replicate simulations suggest that the outcome of virotherapy is more stochastic than generally appreciated. Our model shows that virus-induced immune responses can interfere with virotherapy, by targeting virus-infected cancer cells and/or by impeding viral spread. In the presence of immune responses, the mode of virus introduction is important, with systemic viral delivery throughout the tumour yielding the most favourable outcomes. The timing of virus introduction also plays a critical role; depending on the efficacy of the immune response, a later start of virotherapy can be advantageous. Overall, our results emphasise that the rational design of oncolytic viruses requires optimising virus-induced immunogenic signals and strategies that balance viral spread with immune activity for improved therapeutic success.

Accumulation of Epstein-Barr virus-induced cross-reactive immune responses is associated with multiple sclerosis.

Accumulation of Epstein-Barr virus-induced cross-reactive immune responses is associated with multiple sclerosis.

Modifications of Mitochondrial Network Morphology Affect the MAVS-Dependent Immune Response in L929 Murine Fibroblasts during Ectromelia Virus Infection.

Since smallpox vaccination was discontinued in 1980, there has been a resurgence of poxvirus infections, particularly the monkeypox virus. Without a global recommendation to use the smallpox vaccine, the population is not immune, posing a severe threat to public health. Given these circumstances, it is crucial to understand the relationship between poxviruses and their hosts. Therefore, this study focuses on the ectromelia virus, the causative agent of mousepox, which serves as an excellent model for studying poxvirus pathogenesis. Additionally, we investigated the role of mitochondria in innate antiviral immunity during ECTV infection, focusing specifically on mitochondrial antiviral signaling protein. The study used a Moscow strain of ECTV and L929 mouse fibroblasts. Cells were treated with ECTV and chemical modulators of mitochondrial network: Mdivi-1 and CCCP. Our investigation revealed that an elongated mitochondrial network attenuates the suppression of MAVS-dependent immunity by ECTV and reduces ECTV replication in L929 fibroblasts compared to cells with an unaltered mitochondrial network. Conversely, a fragmented mitochondrial network reduces the number of progeny virions while increasing the inhibition of the virus-induced immune response during infection. In conclusion, our study showed that modifications of mitochondrial network morphology alter MAVS-dependent immunity in ECTV-infected mouse L929 fibroblasts.

Nervous necrosis virus capsid protein and Protein A dynamically modulate the fish cGAS-mediated IFN signal pathway to facilitate viral evasion.

Nervous necrosis virus (NNV), an aquatic RNA virus belonging to Betanodavirus, infects a variety of marine and freshwater fishes, leading to massive mortality of cultured larvae and juveniles and substantial economic losses. The enzyme cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) is widely recognized as a central component in the innate immune response to cytosolic DNA derived from different pathogens. However, little is known about the response of cGAS to aquatic RNA viruses. This study found that Epinephelus coioides cGAS (EccGAS) overexpression inhibited NNV replication, whereas EccGAS silencing promoted NNV replication. The anti-NNV activity of EccGAS was involved in interferon (IFN) signaling activation including tumor necrosis factor receptor-associated factor family member-associated NF-kappa-B activator-binding kinase 1 (TBK1) phosphorylation, interferon regulatory factor 3 (IRF3) nuclear translocation, and the subsequent induction of IFNc and ISGs. Interestingly, NNV employed its capsid protein (CP) or Protein A (ProA) to negatively or positively modulate EccGAS-mediated IFN signaling by simultaneously targeting EccGAS. CP interacted with EccGAS via the arm-P, S-P, and SD structural domains and promoted its polyubiquitination with K48 and K63 linkages in an EcUBE3C (the ubiquitin ligase)-dependent manner, ultimately leading to EccGAS degradation. Conversely, ProA bound to EccGAS and inhibited its ubiquitination and degradation. In regulating EccGAS protein content, CP's inhibitory action was more pronounced than ProA's protective effect, allowing successful NNV replication. These novel findings suggest that NNV CP and ProA dynamically modulate the EccGAS-mediated IFN signaling pathway to facilitate the immune escape of NNV. Our findings shed light on a novel mechanism of virus-host interaction and provide a theoretical basis for the prevention and control of NNV.IMPORTANCEAs a well-known DNA sensor, cGAS is a pivotal component in innate anti-viral immunity to anti-DNA viruses. Although there is growing evidence regarding the function of cGAS in the resistance to RNA viruses, the mechanisms by which cGAS participates in RNA virus-induced immune responses in fish and how aquatic viruses evade cGAS-mediated immune surveillance remain elusive. Here, we investigated the detailed mechanism by which EccGAS positively regulates the anti-NNV response. Furthermore, NNV CP and ProA interacted with EccGAS, regulating its protein levels through ubiquitin-proteasome pathways, to dynamically modulate the EccGAS-mediated IFN signaling pathway and facilitate viral evasion. Notably, NNV CP was identified to promote the ubiquitination of EccGAS via ubiquitin ligase EcUBE3C. These findings unveil a novel strategy for aquatic RNA viruses to evade cGAS-mediated innate immunity, enhancing our understanding of virus-host interactions.

Placental inflammation in a fetal demise of a SARS-CoV-2-asymptomatic, COVID-19-unvaccinated pregnant woman: a case-report

BackgroundIntrauterine fetal demise is a recognized complication of coronavirus disease 2019 in pregnant women and is associated with histopathological placental lesions. The pathological mechanism and virus-induced immune response in the placenta are not fully understood. A detailed description of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced inflammation in the placenta during fetal demise is crucial for improved clinical management.Case presentationWe report the case of a 27-week gestation SARS-CoV-2-asymptomatic unvaccinated pregnant woman without comorbidities or other risk factors for negative pregnancy outcomes with a diagnosis of intrauterine fetal demise. Histopathological findings corresponded to patterns of subacute inflammation throughout the anatomic compartments of the placenta, showing severe chorioamnionitis, chronic villitis and deciduitis, accompanied by maternal and fetal vascular malperfusion. Our immunohistochemistry results revealed infiltration of CD68+ macrophages, CD56+ Natural Killer cells and scarce CD8+ T cytotoxic lymphocytes at the site of placental inflammation, with the SARS-CoV-2 nucleocapsid located in stromal cells of the chorion and chorionic villi, and in decidual cells.ConclusionThis case describes novel histopathological lesions of inflammation with infiltration of plasma cells, neutrophils, macrophages, and natural killer cells associated with malperfusion in the placenta of a SARS-CoV-2-infected asymptomatic woman with intrauterine fetal demise. A better understanding of the inflammatory effects exerted by SARS-CoV-2 in the placenta will enable strategies for better clinical management of pregnant women unvaccinated for SARS-CoV-2 to avoid fatal fetal outcomes during future transmission waves.

O-GlcNAc of STING mediates antiviral innate immunity

BackgroundO-GlcNAcylation modification affects multiple physiological and pathophysiolocal functions of cells. Altered O-GlcNAcylation was reported to participate in antivirus response. Stimulator of interferon genes (STING) is an adaptor mediating DNA virus-induced innate immune response. Whether STING is able to be modified by O-GlcNAcylation and how O-GlcNAcylation affects STING-mediated anti-DNA virus response remain unknown.MethodsMetabolomics analysis was used for detecting metabolic alterations in HSV-1 infection cells. Succinylated wheat germ agglutinin (sWGA), co-immunoprecipitation, and pull-down assay were employed for determining O-GlcNAcylation. Mutagenesis PCR was applied for the generation of STING mutants. WT and Sting1−/− C57BL/6 mice (KOCMP-72512-Sting1-B6NVA) were infected with HSV-1 and treated with O-GlcNAcylation inhibitor for validating the role of STING O-GlcNAcylation in antiviral response.ResultsSTING was functionally activated by O-GlcNAcylation in host cells challenged with HSV-1. We demonstrated that this signaling event was initiated by virus infection-enhanced hexosamine biosynthesis pathway (HBP). HSV-1 (or viral DNA mimics) promotes glucose metabolism of host cells with a marked increase in HBP, which provides donor glucosamine for O-GlcNAcylation. STING was O-GlcNAcylated on threonine 229, which led to lysine 63-linked ubiquitination of STING and activation of antiviral immune responses. Mutation of STING T229 to alanine abrogated STING activation and reduced HSV-1 stimulated production of interferon (IFN). Application of 6-diazo-5-oxonorleucine (DON), an agent that blocks the production of UDP-GlcNAc and inhibits O-GlcNAcylation, markedly attenuated the removal of HSV-1 in wild type C57BL/6 mice, leading to an increased viral retention, elevated infiltration of inflammatory cells, and worsened tissue damages to those displayed in STING gene knockout mice. Together, our data suggest that STING is O-GlcNAcylated in HSV-1, which is crucial for an effective antiviral innate immune response.ConclusionHSV-1 infection activates the generation of UDP-Glc-NAc by upregulating the HBP metabolism. Elevated UDP-Glc-NAc promotes the O-GlcNAcylation of STING, which mediates the anti-viral function of STING. Targeting O-GlcNAcylation of STING could be a useful strategy for antiviral innate immunity.

Chitosan nanoparticles-based in vivo delivery of miR-155 modulates the Viral haemorrhagic septicaemia virus-induced antiviral immune responses in zebrafish (Danio rerio)

Viral haemorrhagic septicaemia virus (VHSV) is one of the highly pathogenic virus, which causes viral haemorrhagic septicaemia disease in both marine and freshwater fish. Micro RNA-155 (miRNA-155) is a multifunctional small non-coding RNA and it involves regulation of immune responses during viral infection. In this study, dre-miR-155 mimics were encapsulated into chitosan nanoparticles (CNPs). Resulted encapsulated product (miR-155-CNPs) was investigated for its immunomodulation role in zebrafish during experimentally challenged VHSV infection. Successful encapsulation of dre-miR-155 mimics into CNPs was confirmed through average nanoparticle (NPs) size (341.45 ± 10.00 nm), increased encapsulation efficiency percentage (98.80%), bound dre-miR-155 with chitosan, sustained release in vitro (up to 40%), and the integrity of RNA. Overexpressed miR-155 was observed in gills, muscle, and kidney tissues (5.42, 19.62, and 140.72-folds, respectively) after intraperitoneal delivery of miR-155-CNPs into zebrafish upon VHSV infection (miR-155-CNPs + VHSV). The miR-155-CNPs + VHSV infected fish had the highest cumulative survival (85%), which was associated with low viral copy numbers. The miR-155-overexpressing fish showed significantly decreased expression of ifnγ, irf2bpl, irf9, socs1a, il10, and caspase3, compared to that of the miR-155 inhibitor + VHSV infected fish group. In contrast, il1β, tnfα, il6, cd8a, and p53 expressions were upregulated in miR-155-overexpressed zebrafish compared to that of the control. The overall findings indicate the successful delivery of dre-miR-155 through miR-155-CNPs that enabled restriction of VHSV infection in zebrafish presumably by modulating immune gene expression.

Role of Coxsackievirus B3-Induced Immune Responses in the Transition from Myocarditis to Dilated Cardiomyopathy and Heart Failure.

Dilated cardiomyopathy (DCM) is a cardiac disease marked by the stretching and thinning of the heart muscle and impaired left ventricular contractile function. While most patients do not develop significant cardiac diseases from myocarditis, disparate immune responses can affect pathological outcomes, including DCM progression. These altered immune responses, which may be caused by genetic variance, can prolong cytotoxicity, induce direct cleavage of host protein, or encourage atypical wound healing responses that result in tissue scarring and impaired mechanical and electrical heart function. However, it is unclear which alterations within host immune profiles are crucial to dictating the outcomes of myocarditis. Coxsackievirus B3 (CVB3) is a well-studied virus that has been identified as a causal agent of myocarditis in various models, along with other viruses such as adenovirus, parvovirus B19, and SARS-CoV-2. This paper takes CVB3 as a pathogenic example to review the recent advances in understanding virus-induced immune responses and differential gene expression that regulates iron, lipid, and glucose metabolic remodeling, the severity of cardiac tissue damage, and the development of DCM and heart failure.

Exploring Influenza A Virus-Induced Lung Injury and Immune Response Based on Humanized Lung-on-Chip.

Influenza is an important respiratory tract pathogen that causes substantial seasonal and pandemic morbidity and mortality. The aim of this study was to systematically analyze the transcriptome characteristics of peripheral blood mononuclear cells (PBMCs) after influenza A virus infection by constructing a human lung microarray model composed of PBMCs to simulate the influenza A virus infection process. A human lung microarray model was constructed using alveolar epithelial cells, vascular endothelial cells, alveolar macrophages and PBMCs, for simulation of the process of influenza A virus infection. The transcriptome characteristics of PBMCs after influenza A virus infection were analyzed by a single-cell RNA sequencing system. The study could realistically mimic the structure and physiological functions of the alveoli in vitro using immunofluorescence staining and expression of the specific marker. After the influenza A virus infected the upper lung chip channels, the epithelial cells underwent a high inflammatory response and spread to endothelial cells. Under experimental conditions, the Influenza A virus infection did not compromise the integrity of epithelial cells, but caused damage to endothelial cells and barrier dysfunction. Single-cell RNA sequencing of PBMCs showed that B and cluster of differentiation 4 (CD4) T cells played important immunomodulatory roles in response to influenza A virus infection, including significantly activating type I interferon signaling pathway, regulating cytokine and chemokine signaling pathway. Especially genes involved in cellular communication were significantly highly expressed post-infection. All these results suggested that the interactions among immune cells played a crucial role in endothelial cell injury and immune cell recruitment after influenza virus infection. This lung-on-chip infection model combined with single-cell RNA sequencing provided a unique platform that can closely investigate the lung immune response to influenza A virus infection and new therapeutic strategies for influenza.

Ste20-Like Kinase TAOK1 Positively Regulates Antiviral Responses by Controlling the TBK1-IRF3 Signaling Axis

The cytosolic viral nucleic acid-sensing pathways converge on the protein kinase TANK-binding kinase 1 (TBK1) and the transcription factor interferon (IFN)-regulatory factor 3 (IRF3) to induce type I IFN production and antiviral immune responses. However, the mechanism that triggers the binding of TBK1 and IRF3 after virus infection remains not fully understood. Here, we identified that thousand and one kinase 1 (TAOK1), a Ste20-like kinase, positively regulated virus-induced antiviral immune responses by controlling the TBK1-IRF3 signaling axis. Virus invasion downregulated the expression of TAOK1. TAOK1 deficiency resulted in decreased nucleic acid-mediated type I IFN production and increased susceptibility to virus infection. TAOK1 was constitutively associated with TBK1 independently of the mitochondrial antiviral signaling protein MAVS. TAOK1 promoted IRF3 activation by enhancing TBK1-IRF3 complex formation. TAOK1 enhanced virus-induced type I IFN production in a kinase activity-dependent manner. Viral infection induced TAOK1 to bind with dynein instead of microtubule-associated protein 4 (MAP4), leading to the trafficking of TBK1 to the perinuclear region to bind IRF3. Thus, the depolymerization of microtubule impaired virus-mediated IRF3 activation. Our results revealed that TAOK1 functioned as a new interaction partner and regulated antiviral signaling via trafficking TBK1 along microtubules to bind IRF3. These findings provided novel insights into the function of TAOK1 in the antiviral innate immune response and its related clinical significance.

Molecular Insights of SARS-CoV-2 Infection and Molecular Treatments.

The coronavirus disease emerged in December 2019 (COVID-19) is caused by Severe Acute Respiratory Syndrome-related coronavirus 2 (SARS-CoV-2). Its rapid global spread has brought an international health emergency and urgent responses for seeking efficient prevention and therapeutic treatment. This has led to imperative needs for illustration of the molecular pathogenesis of SARS-CoV-2, identification of molecular targets or receptors, and development of antiviral drugs, antibodies, and vaccines. In this study, we investigated the current research progress in combating SARS-CoV-2 infection. Based on the published research findings, we first elucidated, at the molecular level, SARS-CoV-2 viral structures, potential viral host-cell-invasion, pathogenic mechanisms, main virus-induced immune responses, and emerging SARS-CoV-2 variants. We then focused on the main virus- and host-based potential targets and summarized and categorized effective inhibitory molecules based on drug development strategies for COVID-19 that can guide efforts for the identification of new drugs and treatment for this problematic disease. Current research and development of antibodies and vaccines were also introduced and discussed. We concluded that the main virus entry route- SARS-CoV-2 spike protein interaction with ACE2 receptors played a key role in guiding the development of therapeutic treatments against COVID-19. Four main strategies may be considered in developing molecular therapeutics, and drug repurposing is likely to be an easy, fast and low-cost approach in such a short period of time with urgent need of antiviral drugs. Additionally, the quick development of antibody and vaccine candidates has yielded promising results, but the wide-scale deployment of safe and effective COVID-19 vaccines remains paramount in solving the pandemic crisis. As new variants of the virus emerge, the efficacy of these vaccines and treatments must be closely evaluated. Finally, we discussed the possible challenges of developing molecular therapeutics for COVID-19 and suggested some potential future efforts. Despite the limited availability of literature, our attempt in this work to provide a relatively comprehensive overview of current SARS-CoV-2 studies can be helpful for quickly acquiring the key information of COVID-19 and further promoting this important research to control and diminish the pandemic.

Understanding on the possible routes for SARS CoV-2 invasion via ACE2 in the host linked with multiple organs damage.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), accountable for causing the coronavirus diseases 2019 (COVID-19), is already declared as a pandemic disease globally. Like previously reported SARS-CoV strain, the novel SARS-CoV-2 also initiates the viral pathogenesis via docking viral spike-protein with the membranal angiotensin-converting enzyme 2 (ACE2) — a receptor on variety of cells in the human body. Therefore, COVID-19 is broadly characterized as a disease that targets multiple organs, particularly causing acute complications via organ-specific pathogenesis accompanied by destruction of ACE2+ cells, including alveolus, cardiac microvasculature, endothelium, and glomerulus. Under such circumstances, the high expression of ACE2 in predisposing individuals associated with anomalous production of the renin-angiotensin system (RAS) may promote enhanced viral load in COVID-19, which comparatively triggers excessive apoptosis. Furthermore, multi-organ injuries were found linked to altered ACE2 expression and inequality between the ACE2/angiotensin-(1–7)/mitochondrial Ang system (MAS) and renin-angiotensin-system (RAS) in COVID-19 patients. However, the exact pathogenesis of multi-organ damage in COVID-19 is still obscure, but several perspectives have been postulated, involving altered ACE2 expression linked with direct/indirect damages by the virus-induced immune responses, such as cytokinin storm. Thus, insights into the invasion of a virus with respect to ACE2 expression site can be helpful to simulate or understand the possible complications in the targeted organ during viral infection. Hence, this review summarizes the multiple organs invasion by SARS CoV-2 linked with ACE2 expression and their consequences, which can be helpful in the management of the COVID-19 pathogenesis under life-threatening conditions.

Antibody Course and Memory B-Cell Response in the First Year After Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

BackgroundThe possibility of repeat infections with SARS-CoV-2 raises questions regarding quality and longevity of the virus-induced immune response.MethodsThe antibody course and memory B-cell (MBC) response against SARS-CoV-2 proteins, influenza virus nucleoprotein (NP) and tetanus toxin (Ttx) were examined in adults with mild to moderate SARS-CoV-2 infection in the first year after infection.ResultsThe concentration of SARS-CoV-2 RBD-specific antibodies was low compared with the concentration of influenza virus NP-specific antibodies. The SARS-CoV-2 RBD antibody half-life increased from 95 days in the first six months to 781 days after 9-12 months. The SARS-CoV-2 NP antibody half-life increased from 88 to 248 days. Two thirds of the subjects had SARS CoV-2-specific MBC responses 12 months after infection. SARS-CoV-2 antibody levels correlated with the MBC frequency at 12 months.ConclusionsThe low concentration of SARS-CoV-2 spike protein antibodies indicates that re-exposure to the virus or vaccination are required to use the B-cell immunity to full capacity. The existence of a robust SARS CoV-2 MBC response at 12 months in most subjects and the substantially increasing antibody half-life provide evidence that the immune response is developing into long-term immunity. The early antibody reaction and the ensuing MBC response are interdependent.

Modeling the virus-induced tumor-specific immune response with delay in tumor virotherapy

It is urgently required to design novel cancer therapies which lead to permanent cancer eradication or cancer control. Oncolytic virotherapy is a promising cancer treatment strategy using genetically engineered viruses which can selectively infect, replicate in and kill tumor cells without harming normal cells. Due to the variable interactions between tumor cells and oncolytic viruses (OVs) as well as the accordingly immune response, the impact of tumor virotherapy on tumor control is prominent. We propose a novel mathematical modeling framework based on delay differential equation to study tumor virotherapy with mediated antitumor immunity by OVs, which incorporates complex tumor–virus–immune system interactions. We initially study the existence and local stability of equilibria, and theoretically and numerically investigate the local Hopf bifurcation from the positive equilibrium by considering the time delay as a bifurcation parameter. Further, we analyze the direction of Hopf bifurcation and the stability of bifurcating periodic solution. Main results show that the time delay can induce Hopf bifurcation and result in periodic oscillations, indicating that the delayed tumor-specific CTL response induced by OVs leads to complex dynamics and may significantly influence the development process of tumor growth. Our findings also provide insight into important aspects of the virotherapy, including the dependence of the efficacy on key factors. We find that enhancing the induction of antitumor immunity by OVs can reduce the complexity of dynamics by strengthening the stability and show considerable effects on combating tumor. Further, proper choice of OVs with relative strong ability to lyse tumor cells is beneficial to ultimately control the development process of tumor growth.

Sericin and sericin-derived peptide alleviate viral pathogenesis in mice though inhibiting lactate production and facilitating antiviral response

Sericin, a bioactive protein forming the outer layer of silk, promotes cell proliferation and cell adhesion, inhibits inflammation, and provides nutrition. Here, we obtain endotoxin-free sericin and explore its potential property in antiviral activity towards infectious diseases. In vesicular stomatitis virus (VSV) infection model, pre-treatment with sericin obviously inhibits VSV replication and reduces organ injury in infected mice. Further studies reveal that pre-incubating cells with sericin results in suppressing the infections of VSV and Enterovirus 71 (EV71) in infected cells. More evidences show that upon virus infection, the levels of interferons (IFNs) are significantly elevated in the cells pre-incubated with sericin as compared to untreated cells, indicating that sericin promotes virus-induced antiviral immune responses. Mechanistically, sericin attenuates cell glycolysis rate and reduces lactate production. Low level of lactate benefitting from sericin treatment facilitates the RIG-I-MAVS signaling pathway to initiate interferon activation. Notably, like sericin, a sericin-derived peptide F5-SP shares the same functions to exert antiviral activity both in vitro and in vivo. Therefore, we report that sericin and sericin-derived peptide F5-SP enhance antiviral innate immune response through inhibiting lactate production, which discovers a promising biomedical application of sericin in the prevention and treatment of viral infectious diseases.

Host-Viral Interactions in the Pathogenesis of Ulcerative Colitis.

Ulcerative colitis is characterized by relapsing and remitting colonic mucosal inflammation. During the early stages of viral infection, innate immune defenses are activated, leading to the rapid release of cytokines and the subsequent initiation of downstream responses including inflammation. Previously, intestinal viruses were thought to be either detrimental or neutral to the host. However, persisting viruses may have a role as resident commensals and confer protective immunity during inflammation. On the other hand, the dysregulation of gut mucosal immune responses to viruses can trigger excessive, pathogenic inflammation. The purpose of this review is to discuss virus-induced innate immune responses that are at play in ulcerative colitis.

Duck Tembusu virus induces stronger cellular responses than Japanese encephalitis virus in primary duck neurons and fibroblasts.

Duck Tembusu virus (DTMUV) and Japanese encephalitis virus (JEV) are mosquito-borne flaviviruses. These two viruses infect ducks; however, they show different neurological outcomes. The mechanism of DTMUV- and JEV-induced neuronal death has not been well investigated. In the present study examined the differences in the mechanisms involved in virus-induced cell death and innate immune responses between the DTMUV KPS54A61 strain and the JEV JaGAr-01 strain using primary duck neurons (DN) and duck fibroblasts (CCL-141). DN and CCL-141 were permissive for the infection and replication of these two viruses, which up-regulated the expression of innate immunity genes. Both DTMUV and JEV induced cell death via a caspase-3-dependent manner; however, DTMUV triggered more cell death than did JEV in both CCL-141 and DN. These findings suggest that DTMUV infection causes apoptosis in duck neurons and fibroblasts more strongly than JEV. The levels of the mRNA expression of innate immunity-related genes after DTMUV infection were generally higher than the levels after JEV infection, suggesting that DTMUV-induced immune response in duck cells may exhibit toxic effects rather than protective effects.

Exploration of Analgesia with Tramadol in the Coxsackievirus B3 Myocarditis Mouse Model

Infection of mice with Coxsackievirus B3 (CVB3) triggers inflammation of the heart and this mouse model is commonly used to investigate underlying mechanisms and therapeutic aspects for viral myocarditis. Virus-triggered cytotoxicity and the activity of infiltrating immune cells contribute to cardiac tissue injury. In addition to cardiac manifestation, CVB3 causes cell death and inflammation in the pancreas. The resulting pancreatitis represents a severe burden and under such experimental conditions, analgesics may be supportive to improve the animals’ well-being. Notably, several known mechanisms exist by which analgesics can interfere with the immune system and thereby compromise the feasibility of the model. We set up a study aiming to improve animal welfare while ensuring model integrity and investigated how tramadol, an opioid, affects virus-induced pathogenicity and immune response in the heart. Tramadol was administered seven days prior to a CVB3 infection in C57BL/6 mice and treatment was continued until the day of analysis. Tramadol had no effect on the virus titer or viral pathogenicity in the heart tissue and the inflammatory response, a hallmark of myocardial injury, was maintained. Our results show that tramadol exerts no disruptive effects on the CVB3 myocarditis mouse model and, therefore, the demonstrated protocol should be considered as a general analgesic strategy for CVB3 infection.

Organic synthesis and anti-influenza A virus activity of cyclobakuchiols A, B, C, and D.

Novel antiviral agents for influenza, which poses a substantial threat to humans, are required. Cyclobakuchiols A and B have been isolated from Psoralea glandulosa, and cyclobakuchiol C has been isolated from P. corylifolia. The structural differences between cyclobakuchiol A and C arise due to the oxidation state of isopropyl group, and these compounds can be derived from (+)-(S)-bakuchiol, a phenolic isoprenoid compound present in P. corylifolia seeds. We previously reported that bakuchiol induces enantiospecific anti-influenza A virus activity involving nuclear factor erythroid 2-related factor 2 (Nrf2) activation. However, it remains unclear whether cyclobakuchiols A–C induce anti-influenza A virus activity. In this study, cyclobakuchiols A, B, and C along with cyclobakuchiol D, a new artificial compound derived from cyclobakuchiol B, were synthesized and examined for their anti-influenza A virus activities using Madin-Darby canine kidney cells. As a result, cyclobakuchiols A–D were found to inhibit influenza A viral infection, growth, and the reduction of expression of viral mRNAs and proteins in influenza A virus-infected cells. Additionally, these compounds markedly reduced the mRNA expression of the host cell influenza A virus-induced immune response genes, interferon-β and myxovirus-resistant protein 1. In addition, cyclobakuchiols A–D upregulated the mRNA levels of NAD(P)H quinone oxidoreductase 1, an Nrf2-induced gene, in influenza A virus-infected cells. Notably, cyclobakuchiols A, B, and C, but not D, induced the Nrf2 activation pathway. These findings demonstrate that cyclobakuchiols have anti-influenza viral activity involving host cell oxidative stress response. In addition, our results suggest that the suitably spatial configuration between oxidized isopropyl group and phenol moiety in the structure of cyclobakuchiols is required for their effect.

The virulence modulator PA-X protein has minor effect on the pathogenicity of the highly pathogenic H7N9 avian influenza virus in mice

PA-X is a novel discovered accessory protein encoded by the PA mRNA of the influenza A virus. Accumulated studies have demonstrated the crucial role of this protein in regulating the virulence of various subtypes of influenza virus, including H1N1, H5N1, H9N2, H1N2, H3N8 and H3N2 virus. However, the role of PA-X protein in regulating the virulence of the highly pathogenic avian H7N9 virus was unknown. In this study, we firstly generated two recombinant H7N9 viruses which have lower PA-X expression level than the parental H7N9 virus. We then systematically compared their difference in virus replication, polymerase activity, virulence and virus-induced host immune responses in mice. The results showed that the PA-X deficient viruses significantly increased viral replication in madin darby canine kidney cells and slightly increased viral replication in mouse lung. In addition, loss of PA-X expression significantly increased viral polymerase activity and alleviated the host-shutoff activity mediated by the parental PA protein. However, in contrast with the usual function of PA-X in regulating the virulence in different subtype influenza virus, no obvious effect on viral virulence in mice was observed by H7N9 PA-X protein. Furthermore, among the 12 kinds of cytokines and 2 kinds of complement derived components that we tested, the PA-X deficiency viruses only induced significantly higher expression levels of MX1 than the parental virus. Altogether, these results showed that PA-X has little effect on viral virulence and viral induced innate immune response of the H7N9 subtype virus. Our study adds further information for the growing understanding of the complexity of PA-X in regulating viral virulence and host innate immune response of different influenza virus.