Influenza viral matrix 1 protein aggravates viral pathogenicity by inducing TLR4-mediated reactive oxygen species production and apoptotic cell death

HPSE-mediated proinflammatory signaling contributes to neurobehavioral deficits following intranasal HSV-1 infection

Herpes simplex virus-1 (HSV-1) is a neurotropic virus that can infect the brain, and an uncontrolled infection can lead to a range of diseases, including chronic nerve pain, encephalitis, and neurobehavioral abnormalities. These outcomes are often severe and have lasting consequences, highlighting the need to identify host factors that contribute to disease severity. In this study, we report that intranasal HSV-1 infection in murine model, which promotes viral dissemination into the brain, implicates the host protein heparanase (HPSE) as a key mediator of neuroinflammation. Specifically, we observed that the HPSE activity during HSV-1 infection in naïve animals promotes the upregulation of proinflammatory cytokines, enhances microglial activity in the brain, and contributes to cognitive impairment, anxiety, and motor coordination deficits. Such effects are significantly less detectable in heparanase deficient (Hpse-/-) mice. Additionally, we found that moderate activation of toll-like receptors (TLRs), particularly in Hpse+/+ mice, may contribute to the activation of the inflammasome pathway. This, in turn, leads to the activation of caspase-1 (Casp1) and caspase-3 (Casp3), which may play a role in nerve function loss. Our findings position HPSE as a potential therapeutic target for mitigating virus-induced neuroinflammation and neurobehavioral defects.

IMPORTANCE

Herpes simplex virus-1 (HSV-1) infection in the brain can lead to severe and often permanent neurological consequences. Host factors influence disease outcomes in response to infection, and understanding these factors is crucial for developing effective therapies. This study identifies the host protein HPSE as a key mediator of neuroinflammation in response to HSV-1 infection. We demonstrate that the HPSE activity drives proinflammatory cytokine expression and microglial activation and promotes a signaling cascade involving toll-like receptors and caspase activation, potentially intensifying neuroinflammatory responses. These findings implicate HPSE as an important player in HSV-1 pathogenesis in the central nervous system and suggest that targeting HPSE could provide a novel therapeutic strategy to mitigate virus-induced neuroinflammation and neurobehavioral disturbance.

The acetyltransferase GCN5 contributes to neuroinflammation in mice by acetylating and activating the NF-κB subunit p65 in microglia

Neuroinflammation promotes the progression of various neurological and neurodegenerative diseases. Disrupted homeostasis of protein acetylation is implicated in neurodegeneration, and the lysine acetyltransferase GCN5 (also known as KAT2A) is implicated in peripheral inflammation. Here, we investigated whether GCN5 plays a role in neuroinflammation in the brain. Systemic administration of the bacterial molecule LPS in mice to induce peripheral inflammation increased the abundance of GCN5 in various organs, including in the brain and specifically in microglia. In response to LPS, GCN5 mediated the induction of the proinflammatory cytokines TNF-α and IL-6 and the inflammatory mediators COX-2 and iNOS in microglia. Further investigation in cultured microglial cells revealed that GCN5 was activated downstream of the innate immune receptor TLR4 to acetylate Lys310 in the NF-κB subunit p65, thereby enabling the nuclear translocation and transcriptional activity of NF-κB and the resulting inflammatory response. Thus, targeting GCN5 might be explored further as a strategy to reduce neuroinflammation in the treatment of associated diseases.

Plant defense metabolites influence the interaction between an insect herbivore and an entomovirus

The tri-trophic interaction of plants, insect herbivores, and entomoviruses is an important topic in ecology and pest control. The susceptibility of insect herbivores to entomoviruses (e.g., nucleopolyhedroviruses) is influenced by host plants; however, the role of plant secondary metabolites in determining such susceptibility is poorly understood. Metabolomic analyses of Brassica oleracea, Glycine max, and Ipomoea aquatica plants, which differ in how they affect the susceptibility of Spodoptera exigua to nucleopolyhedroviruses among 14 plants, suggested that the plant secondary metabolites genistein, kaempferol, quercitrin, and coumarin play a role in influencing nucleopolyhedroviruses susceptibility. Subsequently, transcriptomic analysis of caterpillars, treated with nucleopolyhedroviruses alone or with one of these four phenolics, identified four genes (CYP340K4, CXE18, GSTe, and GSTe1) that were significantly downregulated by the phenolics. Functional characterization of these genes suggested that their downregulation significantly increased larval sensitivity to nucleopolyhedroviruses and altered aspects of the immune response. Our findings provide new insight into the role of plant defense metabolites in influencing the interactions between insect herbivores and entomopathogens and identify plant secondary metabolites as potential synergists of viral agents for the control of agricultural pests.

Oxidative Stress Induced by Antivirals: Implications for Adverse Outcomes During Pregnancy and in Newborns

Oxidative stress plays a critical role in various physiological and pathological processes, particularly during pregnancy, where it can significantly affect maternal and fetal health. In the context of viral infections, such as those caused by Human Immunodeficiency Virus (HIV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), oxidative stress may exacerbate complications by disrupting cellular function and immune responses. Antiviral drugs, while essential in managing these infections, can also contribute to oxidative stress, potentially impacting both the mother and the developing fetus. Understanding the mechanisms by which antivirals can contribute to oxidative stress and examination of pharmacokinetic changes during pregnancy that influence drug metabolism is essential. Some research indicates that antiretroviral drugs can induce oxidative stress and mitochondrial dysfunction during pregnancy, while other studies suggest that their use is generally safe. Therefore, concerns about long-term health effects persist. This review delves into the complex interplay between oxidative stress, antioxidant defenses, and antiviral therapies, focusing on strategies to mitigate potential oxidative damage. By addressing gaps in our understanding, we highlight the importance of balancing antiviral efficacy with the risks of oxidative stress. Moreover, we advocate for further research to develop safer, more effective therapeutic approaches during pregnancy. Understanding these dynamics is essential for optimizing health outcomes for both mother and fetus in the context of viral infections during pregnancy.

Age-related STING suppression in macrophages contributes to increased viral load during influenza a virus infection

Ageing is a major risk factor that contributes to increased mortality and morbidity rates during influenza A virus (IAV) infections. Macrophages are crucial players in the defense against viral infections and display impaired function during ageing. However, the impact of ageing on macrophage function in response to an IAV infection remains unclear and offers potential insight for underlying mechanisms. In this study, we investigated the immune response of young and aged human monocyte-derived macrophages to two different H1N1 IAV strains. Interestingly, macrophages of aged individuals showed a lower interferon response to IAV infection, resulting in increased viral load. Transcriptomic data revealed a reduced expression of stimulator of interferon genes (STING) in aged macrophages albeit the cGAS-STING pathway was upregulated. Our data clearly indicate the importance of STING signaling for interferon production by applying a THP-1 STING knockout model. Evaluation of mitochondrial function during IAV infection revealed the release of mitochondrial DNA to be the activator of cGAS-STING pathway. The subsequent induction of apoptosis was attenuated in aged macrophages due to decreased STING signaling. Our study provides new insights into molecular mechanisms underlying age-related immune impairment. To our best knowledge, we are the first to discover an age-dependent difference in gene expression of STING on a transcriptional level in human monocyte-derived macrophages possibly leading to a diminished interferon production.

Preparation and characterization of kelp polysaccharide and its research on anti-influenza a virus activity

The beneficial effects of kelp polysaccharide (KPS) have recently attracted attention. In this study, KPS was extracted from kelp using the enzyme hydrolysis combined with freeze-drying, namely, KPS-EF. The structural characterization showed that KPS-EF was a highly sulfated macromolecule with the Mw of 764.2 kDa and the sulfate content of 23.49 %. The antiviral activity of KPS-EF in vitro was verified, and the IC50 value of KPS against the PR8 virus was 0.58 mg/mL. Intranasal administration of KPS-EF significantly inhibited death and weight loss in IAV-infected mice and alleviated virus-induced pneumonia symptoms, meanwhile, KPS-EF (10 mg/kg/day) significantly decreased the production levels of chemokines (CXCL1, RANTES) and inflammatory cytokines (IL-6, TNF-α) in lungs (p < 0.05). KPS-EF could downregulate the activity of viral neuraminidase (NA) primarily in the late stage of viral adsorption with an IC50 value of 0.29 mg/mL. This study provides a theoretical basis for the using KPS as a supplement to NA inhibitors or anti-influenza drugs.

Decoding Toll-like receptors: Recent insights and perspectives in innate immunity

Toll-like receptors (TLRs) are an evolutionarily conserved family in the innate immune system and are the first line of host defense against microbial pathogens by recognizing pathogen-associated molecular patterns (PAMPs). TLRs, categorized into cell surface and endosomal subfamilies, recognize diverse PAMPs, and structural elucidation of TLRs and PAMP complexes has revealed their intricate mechanisms. TLRs activate common and specific signaling pathways to shape immune responses. Recent studies have shown the importance of post-transcriptional regulation in TLR-mediated inflammatory responses. Despite their protective functions, aberrant responses of TLRs contribute to inflammatory and autoimmune disorders. Understanding the delicate balance between TLR activation and regulatory mechanisms is crucial for deciphering their dual role in immune defense and disease pathogenesis. This review provides an overview of recent insights into the history of TLR discovery, elucidation of TLR ligands and signaling pathways, and their relevance to various diseases.

H9N2 Avian Influenza Virus Downregulates FcRY Expression in Chicken Macrophage Cell Line HD11 by Activating the JNK MAPK Pathway

The H9N2 avian influenza virus causes reduced production performance and immunosuppression in chickens. The chicken yolk sac immunoglobulins (IgY) receptor (FcRY) transports from the yolk into the embryo, providing offspring with passive immunity to infection against common poultry pathogens. FcRY is expressed in many tissues/organs of the chicken; however, there are no reports investigating FcRY expression in chicken macrophage cells, and how H9N2-infected HD11 cells (a chicken macrophage-like cell line) regulate FcRY expression remains uninvestigated. This study used the H9N2 virus as a model pathogen to explore the regulation of FcRY expression in avian macrophages. FcRY was highly expressed in HD11 cells, as shown by reverse transcription polymerase chain reactions, and indirect immunofluorescence indicated that FcRY was widely expressed in HD11 cells. HD11 cells infected with live H9N2 virus exhibited downregulated FcRY expression. Transfection of eukaryotic expression plasmids encoding each viral protein of H9N2 into HD11 cells revealed that nonstructural protein (NS1) and matrix protein (M1) downregulated FcRY expression. In addition, the use of a c-jun N-terminal kinase (JNK) activator inhibited the expression of FcRY, while a JNK inhibitor antagonized the downregulation of FcRY expression by live H9N2 virus, NS1 and M1 proteins. Finally, a dual luciferase reporter system showed that both the M1 protein and the transcription factor c-jun inhibited FcRY expression at the transcriptional level. Taken together, the transcription factor c-jun was a negative regulator of FcRY, while the live H9N2 virus, NS1, and M1 proteins downregulated the FcRY expression through activating the JNK signaling pathway. This provides an experimental basis for a novel mechanism of immunosuppression in the H9N2 avian influenza virus.

Serum Bilirubin Levels and Risk of Venous Thromboembolism among Influenza Patients: A Cohort Study

OBJECTIVE

This study aimed to investigate the associations between total serum bilirubin levels and the incidence of venous thromboembolism (VTE) among patients with influenza infection.

METHODS

A retrospective cohort study was conducted among outpatients with laboratory-confirmed influenza using data from the Veterans Affairs Informatics and Computing Infrastructure (VINCI). Propensity score weighting was applied to balance study groups across baseline covariates. Cox proportional hazards models assessed VTE risk by total bilirubin levels, adjusting for important covariates including age, sex, race, comorbidity index, BMI, and smoking status.

RESULTS

A total of 487 patients with total bilirubin levels <0.3 mg/dL, 8608 patients with levels between 0.3-1 mg/dL, and 1148 patients with levels >1 mg/dL were included. Patients with bilirubin <0.3 mg/dL exhibited a 6-fold higher risk of VTE compared to those with levels 0.3-1 mg/dL within 30 days of infection (HR = 6.2, 95% CI = 1.46-26.42). Elevated risks were noted through 90 days post infection (HR = 4.71, 95% CI = (1.42-15.67)).

CONCLUSIONS

Serum bilirubin levels, particularly below 0.3 mg/dL, were significantly associated with an increased risk of VTE among individuals with influenza. These findings suggest that lower bilirubin levels may contribute to heightened inflammatory responses and subsequent thromboembolic events in patients with influenza. The underlying mechanisms and potential therapeutic implications for VTE prevention among patients with acute respiratory infection warrants further consideration.

Mitochondrial Reactive Oxygen Species in TRIF-Dependent Toll-like Receptor 3 Signaling in Bronchial Epithelial Cells against Viral Infection

Toll-like receptor 3 (TLR3) plays an important role in double-stranded RNA recognition and triggers the innate immune response by acting as a key receptor against viral infections. Intracellular reactive oxygen species (ROS) are involved in TLR3-induced inflammatory responses during viral infections; however, their relationship with mitochondrial ROS (mtROS) remains largely unknown. In this study, we show that polyinosinic-polycytidylic acid (poly(I:C)), a mimic of viral RNA, induced TLR3-mediated nuclear factor-kappa B (NF-κB) signaling pathway activation and enhanced mtROS generation, leading to inflammatory cytokine production. TLR3-targeted small interfering RNA (siRNA) and Mito-TEMPO inhibited inflammatory cytokine production in poly(I:C)-treated BEAS-2B cells. Poly(I:C) recruited the TLR3 adaptor molecule Toll/IL-1R domain-containing adaptor, inducing IFN (TRIF) and activated NF-κB signaling. Additionally, TLR3-induced mtROS generation suppression and siRNA-mediated TRIF downregulation attenuated mitochondrial antiviral signaling protein (MAVS) degradation. Our findings provide insights into the TLR3-TRIF signaling pathway and MAVS in viral infections, and suggest TLR3-mtROS as a therapeutic target for the treatment of airway inflammatory and viral infectious diseases.

Generation of "OP7 chimera" defective interfering influenza A particle preparations free of infectious virus that show antiviral efficacy in mice

Influenza A virus (IAV) defective interfering particles (DIPs) are considered as new promising antiviral agents. Conventional DIPs (cDIPs) contain a deletion in the genome and can only replicate upon co-infection with infectious standard virus (STV), during which they suppress STV replication. We previously discovered a new type of IAV DIP "OP7" that entails genomic point mutations and displays higher antiviral efficacy than cDIPs. To avoid safety concerns for the medical use of OP7 preparations, we developed a production system that does not depend on infectious IAV. We reconstituted a mixture of DIPs consisting of cDIPs and OP7 chimera DIPs, in which both harbor a deletion in their genome. To complement the defect, the deleted viral protein is expressed by the suspension cell line used for production in shake flasks. Here, DIP preparations harvested are not contaminated with infectious virions, and the fraction of OP7 chimera DIPs depended on the multiplicity of infection. Intranasal administration of OP7 chimera DIP material was well tolerated in mice. A rescue from an otherwise lethal IAV infection and no signs of disease upon OP7 chimera DIP co-infection demonstrated the remarkable antiviral efficacy. The clinical development of this new class of broad-spectrum antiviral may contribute to pandemic preparedness.