Viral recognition and the antiviral interferon response

Exhausted natural killer cells in adult IgA vasculitis

INTRODUCTION

IgA vasculitis nephritis (IgAVN) manifests in up to 84% of adult patients with IgA vasculitis (IgAV) and is associated with an elevated risk of progression to chronic kidney failure. The underlying pathogenic mechanism of adult IgAVN in leukocytes remain largely uncharacterised. Although natural killer (NK) cells were investigated in paediatric IgAV, their specific role in the pathogenesis of adult IgAV has yet to be elucidated.

METHODS

RNA sequencing of leukocytes from adult IgAV patients and healthy controls (HC) was performed. NK cells' cytotoxicity was assessed using calcein-AM stained K562 cells, and exocytosis was measured by LAMP-1/CD107a expression. Intracellular perforin and granzyme B were analyzed via flow cytometry, and cytokine secretion was measured by Luminex xMAP. Interferon-induced genes were validated with qPCR.

RESULTS

Principal component analysis (PCA) of leukocyte gene expression profiles distinguished IgAV patients from HC. Pathway enrichment analysis showed differences in patients' subsets - Interferon signalling Reactome pathway was observed only in sample from patients with skin-limited IgAV (sl-IgAV) and was confirmed by increased expression of interferon-induced genes using qPCR. Only in samples from IgAVN patients enrichment of NK cell-mediated cytotoxicity KEGG pathway was found. NK cells from IgAVN patients showed significantly decreased cytotoxicity compared to samples from sl-IgAV patients (p = 2.53 × 10- 2). The % of CD107a+-NK cells significantly increased after stimulation in HC (p = 9.7 × 10- 3) and in sl-IgAV patient samples (p = 2.21 × 10- 2) while only a minor increase was observed in samples of IgAVN patients. IgAVN patients exhibited a decreased % of perforin+ NK cells compared to HC. Following phytohemagglutinin (PHA)/interleukin (IL)-2 stimulation, a significant reduction in intracellular perforin level was observed in HC (p = 2.53 × 10- 2), but not in IgAVN patients NK cells. Interferon (IFN)-ϒ and macrophage inflammatory protein (MIP)-1β were significantly decreased in NK cell culture supernatants from IgAVN patients (p = 2.64 × 10- 2 and p = 2.65 × 10- 2 respectively).

CONCLUSION

Patients with IgAVN exhibited impaired cytotoxic and immunomodulatory functions of NK cells, along with a marked absence of interferon signaling in PBMCs. Further studies are needed to confirm if discrimination of patient subsets based on leukocyte samples might be of clinical use and if deregulated NK function might contribute to the pathogenesis of nephritis in adult IgAV.

Neurotropic enteric viruses in animals: Comparative research, knowledge gaps, and the role of pathology

Enteric viruses are commonly associated with gastrointestinal diseases but have the capacity, with mostly unknown triggers, to invade the central nervous system (CNS). Neuropathogenic enteric viruses (NEV) that are able to cross or bypass the blood-brain barrier cause debilitating neurological inflammation and disease. The most notorious example of an enteric virus with potential neurotropism is poliovirus, a member of the Picornaviridae family. While poliovirus has been largely eradicated due to extensive vaccination programs, other nonpolio picornaviruses, as well as enteric viruses of other families, are increasingly recognized as causative agents in cases of encephalitis of unknown origin. In the past decade, cutting-edge high-throughput sequencing and bioinformatics strategies have revealed an increasing number of NEV associated with neurological diseases in various animal species. Information, especially pathogenesis studies, on animal enteric viruses with neurotropism is relatively scarce. This review provides an overview of known enteric viruses that invade the CNS, which should support our awareness of the potential etiologic agents and encourage a diagnostic plan that includes NEV. The many knowledge gaps in host susceptibility and viral pathogenesis along the gut-brain axis would benefit from increased discovery efforts and a deeper understanding of the pathogenesis and potential of enteric viruses affecting the nervous system of animals. Crossing of species barriers is common among enteric viruses, so a one-health approach to increase awareness of animal and human NEV would contribute to effective strategies to monitor, manage, and contain emerging zoonotic outbreaks.

Anti-SARS-CoV-2 Small Molecule Targeting of Oxysterol-Binding Protein (OSBP) Activates Cellular Antiviral Innate Immunity

Human oxysterol-binding protein (OSBP) is a potentially druggable mediator in the replication of a broad spectrum of positive-sense (+) single-stranded RNA (ssRNA) viruses, including members of the Picornaviridae, Flaviviridae, and Coronaviridae. OSBP is a cytoplasmic lipid transporting protein capable of moving cholesterol and phosphoinositides between the endoplasmic reticulum (ER) and Golgi, and the ER and lysosome. Several structurally diverse antiviral compounds have been reported to function through targeting OSBP, including the natural product compound OSW-1. Our prior work shows that transient OSW-1 treatment induces a reduction in OSBP protein levels over multiple successive cell generations (i.e., multigenerational), with no apparent cellular toxicity, and the OSW-1-induced reduction of OSBP has antiviral activity against multiple (+)ssRNA viruses. This study extends these findings and establishes that OSW-1 has in vitro antiviral activity against multiple pathogenic (+)ssRNA viruses, including human rhinovirus (HRV1B), the feline coronavirus peritonitis virus (FIPV), human coronavirus 229E (HCoV-229E), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We also demonstrate that OSW-1 treatment in human airway epithelial cells alters the expression of multiple antiviral innate immune mediators, including the interferon (IFN) related genes IFNB1, IFNL3, CXCL10, ISG15, and MX1. Furthermore, OSW-1 enhances the induction of specific components of type I and III IFN antiviral responses triggered by the RNA viral mimetic polyinosinic-polycytidylic acid (Poly IC). In summary, this study further demonstrates the importance of OSBP in (+)ssRNA virus replication and presents OSBP as a potential regulator of cellular antiviral innate immune responses.

Guardians at the gate: Unraveling Type I interferon's role and challenges posed by anti-interferon antibodies in COVID-19

The intricate interplay involving Type I interferon (IFN), anti-interferon antibodies, and COVID-19 elucidates a complex symphony within the immune system. This chapter thoroughly explores the dynamic landscape of Type I IFN, delineating its pivotal role as the guardian of the immune response. As SARS-CoV-2 engages the host, the delicate balance of IFN induction and signaling pathways is disrupted, resulting in a nuanced impact on the severity and pathogenesis of COVID-19. Clinical studies illuminate a critical link between impaired IFN response and severe outcomes, uncovering genetic factors contributing to susceptibility. Furthermore, the emergence of anti-interferon antibodies proves to be a disruptive force, compromising the immune arsenal and correlating with disease severity. Our chapter encompasses diagnostic and prognostic implications, highlighting the importance of assays in identifying levels of IFN and anti-interferon antibodies. This chapter examines the possible incorporation of interferon-related biomarkers in COVID-19 diagnostics, offering predictive insights into disease progression. On the therapeutic front, efforts to manipulate the IFN pathway undergo scrutiny, encountering complexities in light of anti-interferon antibodies. This chapter concludes by outlining prospective avenues for precision medicine, emphasizing the imperative need for a comprehensive comprehension of the IFN landscape and its intricate interaction with COVID-19.

ORMDL3 restrains type I interferon signaling and anti-tumor immunity by promoting RIG-I degradation

Mounting evidence has demonstrated the genetic association of ORMDL sphingolipid biosynthesis regulator 3 (ORMDL3) gene polymorphisms with bronchial asthma and a diverse set of inflammatory disorders. However, its role in type I interferon (type I IFN) signaling remains poorly defined. Herein, we report that ORMDL3 is a negative modulator of the type I IFN signaling by interacting with mitochondrial antiviral signaling protein (MAVS) and subsequently promoting the proteasome-mediated degradation of retinoic acid-inducible gene I (RIG-I). Immunoprecipitation coupled with mass spectrometry (IP-MS) assays uncovered that ORMDL3 binds to ubiquitin-specific protease 10 (USP10), which forms a complex with and stabilizes RIG-I through decreasing its K48-linked ubiquitination. ORMDL3 thus disrupts the interaction between USP10 and RIG-I, thereby promoting RIG-I degradation. Additionally, subcutaneous syngeneic tumor models in C57BL/6 mice revealed that inhibition of ORMDL3 enhances anti-tumor efficacy by augmenting the proportion of cytotoxic CD8 positive T cells and IFN production in the tumor microenvironment (TME). Collectively, our findings reveal the pivotal roles of ORMDL3 in maintaining antiviral innate immune responses and anti-tumor immunity.

Autophagy and Respiratory Viruses: Mechanisms, Viral Exploitation, and Therapeutic Insights

Respiratory viruses, such as influenza virus, rhinovirus, coronavirus, and respiratory syncytial virus (RSV), continue to impose a heavy global health burden. Despite existing vaccination programs, these infections remain leading causes of morbidity and mortality, especially among vulnerable populations like children, older adults, and immunocompromised individuals. However, the current therapeutic options for respiratory viral infections are often limited to supportive care, underscoring the need for novel treatment strategies. Autophagy, particularly macroautophagy, has emerged as a fundamental cellular process in the host response to respiratory viral infections. This process not only supports cellular homeostasis by degrading damaged organelles and pathogens but also enables xenophagy, which selectively targets viral particles for degradation and enhances cellular defense. However, viruses have evolved mechanisms to manipulate the autophagy pathways, using them to evade immune detection and promote viral replication. This review examines the dual role of autophagy in viral manipulation and host defense, focusing on the complex interplay between respiratory viruses and autophagy-related pathways. By elucidating these mechanisms, we aim to highlight the therapeutic potential of targeting autophagy to enhance antiviral responses, offering promising directions for the development of effective treatments against respiratory viral infections.

Proinflammatory Cytokines in Chronic Respiratory Diseases and Their Management

Pulmonary homeostasis can be agitated either by external environmental insults or endogenous factors produced during respiratory/pulmonary diseases. The lungs counter these insults by initiating mechanisms of inflammation as a localized, non-specific first-line defense response. Cytokines are small signaling glycoprotein molecules that control the immune response. They are formed by numerous categories of cell types and induce the movement, growth, differentiation, and death of cells. During respiratory diseases, multiple proinflammatory cytokines play a crucial role in orchestrating chronic inflammation and structural changes in the respiratory tract by recruiting inflammatory cells and maintaining the release of growth factors to maintain inflammation. The issue aggravates when the inflammatory response is exaggerated and/or cytokine production becomes dysregulated. In such instances, unresolving and chronic inflammatory reactions and cytokine production accelerate airway remodeling and maladaptive outcomes. Pro-inflammatory cytokines generate these deleterious consequences through interactions with receptors, which in turn initiate a signal in the cell, triggering a response. The cytokine profile and inflammatory cascade seen in different pulmonary diseases vary and have become fundamental targets for advancement in new therapeutic strategies for lung diseases. There are considerable therapeutic approaches that target cytokine-mediated inflammation in pulmonary diseases; however, blocking specific cytokines may not contribute to clinical benefit. Alternatively, broad-spectrum anti-inflammatory approaches are more likely to be clinically effective. Herein, this comprehensive review of the literature identifies various cytokines (e.g., interleukins, chemokines, and growth factors) involved in pulmonary inflammation and the pathogenesis of respiratory diseases (e.g., asthma, chronic obstructive pulmonary, lung cancer, pneumonia, and pulmonary fibrosis) and investigates targeted therapeutic treatment approaches.

Types I to IV IFNs and their receptors in white spotted bamboo shark (Chiloscyllium plagiosum)

Interferons (IFNs) are a class of proteins with significant antiviral and antibacterial functions. To date, four distinct types of IFNs have been identified in vertebrates, including types I, II, III and IV IFNs. However, all these IFNs have not been reported together from any species of cartilaginous fish. In this study, types I, II, III and IV IFNs have been identified in white spotted bamboo shark (Chiloscyllium plagiosum). Type I IFNs were distributed in a conserved locus as reported in amphibian and zebrafish with seven duplicated genes. IFN-γ and IFN-υ genes were located in conserved loci as reported in other vertebrates, but four copies of IFN-υ genes were found in the bamboo shark as compared with a single gene in other vertebrates. However, a single IFN-λ gene was found in the bamboo shark, but not in the conserved gene locus as reported in other vertebrates. It is obvious that all these IFN genes were constitutively expressed in examined organs/tissue, and were induced following poly(I:C) stimulation. The findings of four types of IFNs in bamboo shark fill up the gap in relation with the composition of IFNs in cartilaginous fish, and contributes to the understanding of IFN system from an evolutionary point of view.

ISGylation: is our genome yearning for such a modification?

ISGylation is the post-translational modification of protein substrates covalently conjugated with the ubiquitin-like protein, interferon-stimulated gene 15 (ISG15). Although initially linked to antiviral immunity, recent evidence highlights important roles for ISGylation in various biological processes, such as maintaining genomic stability, promoting tumourigenesis, and being involved in other pathological conditions. In this review, we examine the molecular mechanisms underlying ISGylation, its interplay with other post-translational modifications, and its involvement in diverse biological and pathological processes. We propose future research directions to advance the field and discuss how ISGylation might be harnessed to ensure human health, particularly genome instability-associated diseases.

Petroselinic Acid from Apiaceae Family Plants Ameliorates Autoimmune Disorders Through Suppressing Cytosolic-Nucleic-Acid-Mediated Type I Interferon Signaling

The recognition of cytosolic nucleic acids is a critical step in the host immune response against danger signals, such as molecular patterns from pathogens or tissue damage. Nonetheless, over-reactivity to self-nucleic acids leads to the sustained production of type I interferon (IFN), mediated either by cGAS or RLR, contributing to the pathogenesis of certain autoimmune diseases, such as Aicardi-Goutières syndrome (AGS). Therefore, inhibiting excessive IFN production represents a potential therapeutic strategy for such autoimmune conditions. In this study, we discovered that petroselinic acid (PA), a natural compound isolated from Apiaceae family plants, effectively suppresses type I IFN production induced by cytosolic nucleic acids. Mechanistic investigations revealed that PA inhibits the phosphorylation of TBK1 and IRF3, which are key nodal proteins within the type I interferon pathway. Notably, molecular docking suggests potential binding between PA and cytosolic nucleic acid sensors, such as cGAS and RIG-I. Moreover, we found that PA effectively attenuates the expression of type I IFN and their downstream interferon-stimulated genes (ISGs) in models of AGS autoimmune disease characterized by excessive nucleic acid accumulation. Thus, our research identifies a natural compound that offers a promising strategy for treating autoimmune diseases resulting from aberrant self-nucleic acid recognition and the hyperactivation of type I interferon.

Comparative Efficacy and Safety of Three Janus Kinase Inhibitors in Ulcerative Colitis: A Real-World Multicentre Study in Japan

BACKGROUND

Three Janus kinase (JAK) inhibitors are approved for ulcerative colitis (UC) in Japan.

AIM

To compare the real-world efficacy and safety of these three JAK inhibitors in UC.

METHODS

This was a multicentre, retrospective study of patients with UC started on JAK inhibitors. The primary outcome was clinical remission at 10, 26 and 58 weeks, and at the most recent follow-up. To compare the efficacy and safety among the JAK inhibitors, we created three matched cohorts (upadacitinib vs. filgotinib, tofacitinib vs. filgotinib and upadacitinib vs. tofacitinib) using propensity score matching.

RESULTS

We identified 228 upadacitinib-treated patients (median follow-up 49 weeks; IQR 25-72), 215 filgotinib-treated patients (follow-up 56 weeks; IQR 17-82) and 159 tofacitinib-treated patients (follow-up 112 weeks; IQR 10-258). Clinical remission rates for upadacitinib, filgotinib and tofacitinib at the most recent follow-up were 72.8%, 50.6% and 45.8%, respectively. Over 70% of the patients previously treated with other biologics or JAK inhibitors achieved clinical remission with upadacitinib. On multivariate analysis, the number of previous advanced therapies was inversely associated with the efficacy of filgotinib and tofacitinib. Comparative analysis showed that upadacitinib-treated patients had higher efficacy and lower risk of discontinuation than patients treated with other JAK inhibitors. However, upadacitinib had a significant risk of acne.

CONCLUSIONS

Considering the particularly high efficacy of upadacitinib, even in patients with refractory UC, filgotinib or tofacitinib may be considered as an upfront JAK inhibitor before using upadacitinib.

Infection-induced trained immunity: a twist in paradigm of innate host defense and generation of immunological memory

In contrast to adaptive immunity, which relies on memory T and B cells for long-term pathogen-specific responses, trained immunity involves the enhancement of innate immune responses through cellular reprogramming. Experimental evidence from animal models and human studies supports the concept of trained immunity and its potential therapeutic applications in the development of personalized medicine. However, there remains a huge gap in understanding the mechanisms, identifying specific microbial triggers responsible for the induction of trained immunity. This underscores the importance of investigating the potential role of trained immunity in redefining host defense and highlights future research directions. This minireview will provide a comprehensive summary of the new paradigm of trained immunity or innate memory pathways. It will shed light on infection-induced pathways through non-specific stimulation within macrophages and natural killer cells, which will be further elaborated in multiple disease perspectives caused by infectious agents such as bacteria, fungi, and viruses. The article further elaborates on the biochemical and cellular basis of trained immunity and its impact on disease status during recurrent exposures. The review concludes with a perspective segment discussing potential therapeutic benefits, limitations, and future challenges in this area of study. The review also sheds light upon potential risks involved in the induction of trained immunity.

Fish cells persistently infected with nervous necrosis virus produce a small-molecule substance for reducing cellular metabolism and suppressing viral multiplication

Nervous necrosis virus (NNV) of the genus Betanodavirus is one of the simplest RNA viruses pathogenic to a wide range of fish species. We established the SeGF, SeGE-22 and SeGB cell lines persistently infected with NNV (PI-SeGFNNV, PI-SeGE-22NNV and PI-SeGBNNV cells) by repeatedly subculturing the cells that survived NNV infection. The PI-SeGFNNV and PI-SeGE-22NNV cells continued to stably yield NNV in culture fluids at 106 to 107 median tissue culture infectious dose (TCID50)/ml even after 30-50 subcultures. The PI-SeGBNNV cells initially yielded NNV at 103.9 TCID50/ml but stopped yielding NNV after several passages. No significant morphological differences were observed between the naïve and PI-cells in either cell line. Antiviral activity suppressing the multiplication of NNV was detected in the culture fluids of all PI-cell lines. It significantly suppressed the growth (metabolism) of each cell line but did not directly influence NNV infectivity. However, this antiviral substance was not an interferon but a heat-stable (100 ºC for 3 min), small molecule with Mr < 1000. When the PI-SeGBNNV cells stopped yielding NNV after subculturing several times, the production of the antiviral substance also ceased, indicating that the production of antiviral substance is initiated by NNV infection.

cGAS-like receptors drive a systemic STING-dependent host response in Drosophila

cGAS-like receptor (cGLR)-stimulator of interferon genes (STING) recently emerged as an important pathway controlling viral infections in invertebrates. However, its exact contribution at the organismal level remains uncharacterized. Here, we use STING::GFP knockin reporter Drosophila flies to document activation of the pathway in vivo. Four tissues strongly respond to injection of the cyclic dinucleotide 3'2'- cyclic guanosine monophosphate-adenosine monophosphate (cGAMP): the central nervous system, midgut, Malpighian tubules, and genital ducts. The pattern of STING::GFP induction in flies injected with 3'2'-cGAMP or infected by two viruses with different tropism suggests that the reporter is induced by a systemic signal produced in virus-infected cells. Accordingly, ectopic expression of cGLR2 in the fat body induces STING signaling in remote tissues and a cGLR1/2-dependent activity is transferred to females during mating. Furthermore, viral infection can alter sleep in a cGLR1/2- and STING-dependent manner. Altogether, our results reveal a contribution of cyclic dinucleotide signaling to a systemic host response to viral infection in Drosophila.

Mouse models of type I interferonopathies

Type I interferonopathies are severe monogenic diseases caused by mutations that result in chronically upregulated production of type I interferon. They present with a broad variety of symptoms, the mechanisms of which are being extensively studied. Mouse models of type I interferonopathies are an important resource for this purpose, and in this context, we review several key molecular and phenotypic findings that are advancing our understanding of the respective diseases. We focus on genotypes related to nucleic acid metabolism, sensing by cytosolic receptors and downstream signalling.

Pathogenesis and virulence of Heartland virus

Heartland virus (HRTV), an emerging tick-borne pathogenic bunyavirus, has been a concern since 2012, with an increasing incidence, expanding geographical distribution, and high pathogenicity in the United States. Infection from HRTV results in fever, thrombocytopenia, and leucopenia in humans, and in some cases, symptoms can progress to severe outcomes, including haemorrhagic disease, multi-organ failure, and even death. Currently, no vaccines or antiviral drugs are available for treatment of the HRTV disease. Moreover, little is known about HRTV-host interactions, viral replication mechanisms, pathogenesis and virulence, further hampering the development of vaccines and antiviral interventions. Here, we aimed to provide a brief review of HRTV epidemiology, molecular biology, pathogenesis and virulence on the basis of published article data to better understand this virus and provide clues for further study.

The Importance of Including Maternal Immune Activation in Animal Models of Hypoxic-Ischemic Encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is a perinatal brain injury that is the leading cause of cerebral palsy, developmental delay, and poor cognitive outcomes in children born at term, occurring in about 1.5 out of 1000 births. The only proven therapy for HIE is therapeutic hypothermia. However, despite this treatment, many children ultimately suffer disability, brain injury, and even death. Barriers to implementation including late diagnosis and lack of resources also lead to poorer outcomes. This demonstrates a critical need for additional treatments for HIE, and to facilitate this, we need translational models that accurately reflect risk factors and interactions present in HIE. Maternal or amniotic infection is a significant risk factor and possible cause of HIE in humans. Maternal immune activation (MIA) is a well-established model of maternal infection and inflammation that has significant developmental consequences largely characterized within the context of neurodevelopmental disorders such as autism spectrum disorder and schizophrenia. MIA can also lead to long-lasting changes within the neuroimmune system, which lead to compounding negative outcomes following a second insult. This supports the importance of understanding the interaction of maternal inflammation and hypoxic-ischemic outcomes. Animal models have been invaluable to understanding the pathophysiology of this injury and to the development of therapeutic hypothermia. However, each model system has its own limitations. Large animal models such as pigs may more accurately represent the brain and organ development and complexity in humans, while rodent models are more cost-effective and offer more possible molecular techniques. Recent studies have utilized MIA or direct inflammation prior to HIE insult. Investigators should thoughtfully consider the risk factors they wish to include in their HIE animal models. In the incorporation of MIA, investigators should consider the type, timing, and dose of the inflammatory stimulus, as well as the timing, severity, and type of hypoxic insult. Using a variety of animal models that incorporate the maternal-placental-fetal system of inflammation will most likely lead to a more robust understanding of the mechanisms of this injury that can guide future clinical decisions and therapies.

Interference without interferon: interferon-independent induction of interferon-stimulated genes and its role in cellular innate immunity

Interferons (IFNs) are multifaceted proteins that play pivotal roles in orchestrating robust antiviral immune responses and modulating the intricate landscape of host immunity. The major signaling pathway activated by IFNs is the JAK/STAT (Janus kinase/signal transducer and activator of transcription) pathway, which leads to the transcription of a battery of genes, collectively known as IFN-stimulated genes (ISGs). While the well-established role of IFNs in coordinating the innate immune response against viral infections is widely acknowledged, recent years have provided a more distinct comprehension of the functional significance attributed to non-canonical, IFN-independent induction of ISGs. In this review, we summarize the non-conventional signaling pathways of ISG induction. These alternative pathways offer new avenues for developing antiviral strategies or immunomodulation in various diseases.

An evolutionary perspective to innate antiviral immunity in animals

Viruses pose a significant threat to cellular organisms. Innate antiviral immunity encompasses both RNA- and protein-based mechanisms designed to sense and respond to infections, a fundamental aspect present in all living organisms. A potent RNA-based antiviral mechanism is RNA interference, where small RNA-programmed nucleases target viral RNAs. Protein-based mechanisms often rely on the induction of transcriptional responses triggered by the recognition of viral infections through innate immune receptors. These responses involve the upregulation of antiviral genes aimed at countering viral infections. In this review, we delve into recent advances in understanding the diversification of innate antiviral immunity in animals. An evolutionary perspective on the gains and losses of mechanisms in diverse animals coupled to mechanistic studies in model organisms such as the fruit fly Drosophila melanogaster is essential to provide deep understanding of antiviral immunity that can be translated to new strategies in the treatment of viral diseases.

Liquid-liquid phase separation is essential for reovirus viroplasm formation and immune evasion

Grass carp reovirus (GCRV) is the most virulent pathogen in the genus Aquareovirus, belonging to the family Spinareoviridae. Members of the Spinareoviridae family are known to replicate and assemble in cytoplasmic inclusion bodies termed viroplasms; however, the detailed mechanism underlying GCRV viroplasm formation and its specific roles in virus infection remains largely unknown. Here, we demonstrate that GCRV viroplasms form through liquid-liquid phase separation (LLPS) of the nonstructural protein NS80 and elucidate the specific role of LLPS during reovirus infection and immune evasion. We observe that viroplasms coalesce within the cytoplasm of GCRV-infected cells. Immunofluorescence and transmission electron microscopy indicate that GCRV viroplasms are membraneless structures. Live-cell imaging and fluorescence recovery after photobleaching assay reveal that GCRV viroplasms exhibit liquid-like properties and are highly dynamic structures undergoing fusion and fission. Furthermore, by using a reagent to inhibit the LLPS process and constructing an NS80 mutant defective in LLPS, we confirm that the liquid-like properties of viroplasms are essential for recruiting viral dsRNA, viral RdRp, and viral proteins to participate in viral genome replication and virion assembly, as well as for sequestering host antiviral factors for immune evasion. Collectively, our findings provide detailed insights into reovirus viroplasm formation and reveal the specific functions of LLPS during virus infection and immune evasion, identifying potential targets for the prevention and control of this virus.

IMPORTANCE

Grass carp reovirus (GCRV) poses a significant threat to the aquaculture industry, particularly in China, where grass carp is a vital commercial fish species. However, detailed information regarding how GCRV viroplasms form and their specific roles in GCRV infection remains largely unknown. We discovered that GCRV viroplasms exhibit liquid-like properties and are formed through a physico-chemical biological phenomenon known as liquid-liquid phase separation (LLPS), primarily driven by the nonstructural protein NS80. Furthermore, we confirmed that the liquid-like properties of viroplasms are essential for virus replication, assembly, and immune evasion. Our study not only contributes to a deeper understanding of GCRV infection but also sheds light on broader aspects of viroplasm biology. Given that viroplasms are a universal feature of reovirus infection, inhibiting LLPS and then blocking viroplasms formation may serve as a potential pan-reovirus inhibition strategy.

A robust mouse model of HPIV-3 infection and efficacy of GS-441524 against virus-induced lung pathology

Human parainfluenza virus type 3 (HPIV-3) can cause severe respiratory tract infections. There are no convenient small-animal infection models. Here, we show viral replication in the upper and lower airways of AG129 mice (double IFNα/β and IFNγ receptor knockout mice) upon intranasal inoculation. By multiplex fluorescence RNAscope and immunohistochemistry followed by confocal microscopy, we demonstrate viral tropism to ciliated cells and club cells of the bronchiolar epithelium. HPIV-3 causes a marked lung pathology. No virus transmission of the virus was observed by cohousing HPIV-3-infected AG129 mice with other mice. Oral treatment with GS-441524, the parent nucleoside of remdesivir, reduced infectious virus titers in the lung, with a relatively normal histology. Intranasal treatment also affords an antiviral effect. Thus, AG129 mice serve as a robust preclinical model for developing therapeutic and prophylactic strategies against HPIV-3. We suggest further investigation of GS-441524 and its prodrug forms to treat HPIV-3 infection in humans.

Different activation of STAT1 and STAT2 phosphorylation by IFNc, IFNd, and IFNh in tilapia

Type I IFNs are a subset of cytokines exerting their antiviral effects mainly through the JAK-STAT signalling. Immunogenetic studies have shown that fish possess key components of IFN-JAK-STAT cascade, but the information about the distinct responses of STAT1 and STAT2 to different IFNs is rather limited in fish. Here, we identified and cloned STAT1 and STAT2 genes (named as On-STAT1 and On-STAT2) from tilapia, Oreochromis niloticus. On-STAT1 and On-STAT2 genes were detected in all orangs/tissues examined, and were rapidly induced in spleen, head kidney, and liver following the stimulation of poly(I:C). In addition, the stimulation of poly(I:C), poly(A:T), and different subgroups of recombinant IFNs could induce the expression of On-STAT1 and On-STAT2 in TA-02 cells with distinct induction levels. Importantly, On-STAT2 was rapidly phosphorylated by all three subgroups of IFNs, but the phosphorylation of On-STAT1 was only observed in IFNc- and IFNh-treated TA-02 cells, reflecting the distinct activation of STAT by different subgroups of fish IFNs. The present results thus contribute to better understanding of the JAK-STAT signalling mediated by different subgroups of IFNs in fish.

Molluscum contagiosum virus protein MC089 inhibits interferon regulatory factor 3 activation

Molluscum contagiosum virus (MCV) is a human-specific poxvirus that causes a highly common but mild infection characterized by distinctive and persistent papular skin lesions. These lesions can persist for long periods without an effective clearance response from the host. MCV, like all poxviruses, encodes multiple known immunosuppressive proteins which target innate immune signalling pathways involved in viral nucleic acid sensing, interferon production and inflammation which should trigger antiviral immunity leading to clearance. Two major families of transcription factors responsible for driving the immune response to viruses are the NF-κB and the interferon regulatory factor (IRF) families. While NF-κB broadly drives pro-inflammatory gene expression and IRFs chiefly drive interferon induction, both collaborate in transactivating many of the same genes in a concerted immune response to viral infection. Here, we report that the MCV protein MC089 specifically inhibits IRF activation from both DNA- and RNA-sensing pathways, making it the first characterized MCV inhibitor to selectively target IRF activation to date. MC089 interacts with proteins required for IRF activation, namely IKKε, TBKBP1 and NAP1. Additionally, MC089 targets RNA sensing by associating with the RNA-sensing adaptor protein mitochondrial antiviral-signalling protein on mitochondria. MC089 displays specificity in its inhibition of IRF3 activation by suppressing immunostimulatory nucleic acid-induced serine 396 phosphorylation without affecting the phosphorylation of serine 386. The selective interaction of MC089 with IRF-regulatory proteins and site-specific inhibition of IRF3 phosphorylation may offer a tool to provide novel insights into the biology of IRF3 regulation.

A Cyclic Peptide Based on Pheasant Cathelicidin Inhibits Influenza A H1N1 Virus Infection

Influenza viruses are the leading cause of upper respiratory tract infections, leading to several global pandemics and threats to public health. Due to the continuous mutation of influenza A viruses, there is a constant need for the development of novel antiviral therapeutics. Recently, natural antimicrobial peptides have provided an opportunity for the discovery of anti-influenza molecules. Here, we designed several peptides based on pheasant cathelicidin and tested their antiviral activities and mechanisms against the H1N1 virus. Of note, the designed peptides Pc-4 and Pc-5 were found to inhibit replication of the H1N1 virus with an IC50 = 8.14 ± 3.94 µM and 2.47 ± 1.95 µM, respectively. In addition, the cyclic peptide Pc-5 was found to induce type I interferons and the expression of interferon-induced genes. An animal study showed that the cyclic peptide Pc-5 effectively inhibited H1N1 virus infection in a mouse model. Taken together, our work reveals a strategy for designing cyclic peptides and provides novel molecules with therapeutic potential against influenza A virus infection.

PR-SET7 epigenetically restrains uterine interferon response and cell death governing proper postnatal stromal development

The differentiation of the stroma is a hallmark event during postnatal uterine development. However, the spatiotemporal changes that occur during this process and the underlying regulatory mechanisms remain elusive. Here, we comprehensively delineated the dynamic development of the neonatal uterus at single-cell resolution and characterized two distinct stromal subpopulations, inner and outer stroma. Furthermore, single-cell RNA sequencing revealed that uterine ablation of Pr-set7, the sole methyltransferase catalyzing H4K20me1, led to a reduced proportion of the inner stroma due to massive cell death, thus impeding uterine development. By combining RNA sequencing and epigenetic profiling of H4K20me1, we demonstrated that PR-SET7-H4K20me1 either directly repressed the transcription of interferon stimulated genes or indirectly restricted the interferon response via silencing endogenous retroviruses. Declined H4K20me1 level caused viral mimicry responses and ZBP1-mediated apoptosis and necroptosis in stromal cells. Collectively, our study provides insight into the epigenetic machinery governing postnatal uterine stromal development mediated by PR-SET7.

Insight into the role of IRF7 in skin and connective tissue diseases

Interferons (IFNs) are signalling proteins primarily involved in initiating innate immune responses against pathogens and promoting the maturation of immune cells. Interferon Regulatory Factor 7 (IRF7) plays a pivotal role in the IFNs signalling pathway. The activation process of IRF7 is incited by exogenous or abnormal nucleic acids, which is followed by the identification via pattern recognition receptors (PRRs) and the ensuing signalling cascades. Upon activation, IRF7 modulates the expression of both IFNs and inflammatory gene regulation. As a multifunctional transcription factor, IRF7 is mainly expressed in immune cells, yet its presence is also detected in keratinocytes, fibroblasts, and various dermal cell types. In these cells, IRF7 is critical for skin immunity, inflammation, and fibrosis. IRF7 dysregulation may lead to autoimmune and inflammatory skin conditions, including systemic scleroderma (SSc), systemic lupus erythematosus (SLE), Atopic dermatitis (AD) and Psoriasis. This comprehensive review aims to extensively elucidate the role of IRF7 and its signalling pathways in immune cells and keratinocytes, highlighting its significance in skin-related and connective tissue diseases.

Meeting the Challenge of Controlling Viral Immunopathology

The mission of this review is to identify immune-damaging participants involved in antiviral immunoinflammatory lesions. We argue these could be targeted and their activity changed selectively by maneuvers that, at the same time, may not diminish the impact of components that help resolve lesions. Ideally, we need to identify therapeutic approaches that can reverse ongoing lesions that lack unwanted side effects and are affordable to use. By understanding the delicate balance between immune responses that cause tissue damage and those that aid in resolution, novel strategies can be developed to target detrimental immune components while preserving the beneficial ones. Some strategies involve rebalancing the participation of immune components using various approaches, such as removing or blocking proinflammatory T cell products, expanding regulatory cells, restoring lost protective cell function, using monoclonal antibodies (moAb) to counteract inhibitory molecules, and exploiting metabolic differences between inflammatory and immuno-protective responses. These strategies can help reverse ongoing viral infections. We explain various approaches, from model studies and some clinical evidence, that achieve innate and adaptive immune rebalancing, offering insights into potential applications for controlling chronic viral-induced lesions.

Serpine1 mRNA confers mesenchymal characteristics to the cell and promotes CD8+ T cells exclusion from colon adenocarcinomas

Serine protease inhibitor clade E member 1 (SERPINE1) inhibits extracellular matrix proteolysis and cell detachment. However, SERPINE1 expression also promotes tumor progression and plays a crucial role in metastasis. Here, we solve this apparent paradox and report that Serpine1 mRNA per se, independent of its protein-coding function, confers mesenchymal properties to the cell, promoting migration, invasiveness, and resistance to anoikis and increasing glycolytic activity by sequestering miRNAs. Expression of Serpine1 mRNA upregulates the expression of the TRA2B splicing factor without affecting its mRNA levels. Through transcriptional profiling, we found that Serpine1 mRNA expression downregulates through TRA2B the expression of genes involved in the immune response. Analysis of human colon tumor samples showed an inverse correlation between SERPINE1 mRNA expression and CD8+ T cell infiltration, unveiling the potential value of SERPINE1 mRNA as a promising therapeutic target for colon tumors.

Investigating the Evolution of Drosophila STING-Dependent Antiviral Innate Immunity by Multispecies Comparison of 2'3'-cGAMP Responses

Viruses represent a major threat to all animals, which defend themselves through induction of a large set of virus-stimulated genes that collectively control the infection. In vertebrates, these genes include interferons that play a critical role in the amplification of the response to infection. Virus- and interferon-stimulated genes include restriction factors targeting the different steps of the viral replication cycle, in addition to molecules associated with inflammation and adaptive immunity. Predictably, antiviral genes evolve dynamically in response to viral pressure. As a result, each animal has a unique arsenal of antiviral genes. Here, we exploit the capacity to experimentally activate the evolutionarily conserved stimulator of IFN genes (STING) signaling pathway by injection of the cyclic dinucleotide 2'3'-cyclic guanosine monophosphate-adenosine monophosphate into flies to define the repertoire of STING-regulated genes in 10 Drosophila species, spanning 40 million years of evolution. Our data reveal a set of conserved STING-regulated factors, including STING itself, a cGAS-like-receptor, the restriction factor pastel, and the antiviral protein Vago, but also 2 key components of the antiviral RNA interference pathway, Dicer-2, and Argonaute2. In addition, we identify unknown species- or lineage-specific genes that have not been previously associated with resistance to viruses. Our data provide insight into the core antiviral response in Drosophila flies and pave the way for the characterization of previously unknown antiviral effectors.

Role of type-I and type-III interferons in gastrointestinal homeostasis and pathogenesis

Interferon (IFN) was discovered based on interference with virus production, and three types of IFN are now defined. Since its discovery, IFN's roles have expanded beyond viruses to diverse pathogen types, tissue homeostasis, and inflammatory disease. The gastrointestinal (GI) tract is arguably the tissue where the roles of IFN types are most distinct, with a particularly prominent role for type-III IFN in antiviral protection of the intestinal epithelium. Current studies continue to deepen our understanding of the type- and tissue-specific roles of IFN. This review highlights these advances within the GI tract, including discovery of protective roles for type-III IFNs against nonviral GI pathogens, and discovery of an antiviral homeostatic type-III IFN response within the intestinal epithelium.

Human Betacoronavirus OC43 Interferes with the Integrated Stress Response Pathway in Infected Cells

Viruses evolve many strategies to ensure the efficient synthesis of their proteins. One such strategy is the inhibition of the integrated stress response-the mechanism through which infected cells arrest translation through the phosphorylation of the alpha subunit of the eukaryotic translation initiation factor 2 (eIF2α). We have recently shown that the human common cold betacoronavirus OC43 actively inhibits eIF2α phosphorylation in response to sodium arsenite, a potent inducer of oxidative stress. In this work, we examined the modulation of integrated stress responses by OC43 and demonstrated that the negative feedback regulator of eIF2α phosphorylation GADD34 is strongly induced in infected cells. However, the upregulation of GADD34 expression induced by OC43 was independent from the activation of the integrated stress response and was not required for the inhibition of eIF2α phosphorylation in virus-infected cells. Our work reveals a complex interplay between the common cold coronavirus and the integrated stress response, in which efficient viral protein synthesis is ensured by the inhibition of eIF2α phosphorylation but the GADD34 negative feedback loop is disrupted.

Mucosal Immunity against SARS-CoV-2 in the Respiratory Tract

The respiratory tract, the first-line defense, is constantly exposed to inhaled allergens, pollutants, and pathogens such as respiratory viruses. Emerging evidence has demonstrated that the coordination of innate and adaptive immune responses in the respiratory tract plays a crucial role in the protection against invading respiratory pathogens. Therefore, a better understanding of mucosal immunity in the airways is critical for the development of novel therapeutics and next-generation vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory viruses. Since the coronavirus disease 2019 pandemic, our knowledge of mucosal immune responses in the airways has expanded. In this review, we describe the latest knowledge regarding the key components of the mucosal immune system in the respiratory tract. In addition, we summarize the host immune responses in the upper and lower airways following SARS-CoV-2 infection and vaccination, and discuss the impact of allergic airway inflammation on mucosal immune responses against SARS-CoV-2.

Antiviral Defence Mechanisms during Early Mammalian Development

The type-I interferon (IFN) response constitutes the major innate immune pathway against viruses in mammals. Despite its critical importance for antiviral defence, this pathway is inactive during early embryonic development. There seems to be an incompatibility between the IFN response and pluripotency, the ability of embryonic cells to develop into any cell type of an adult organism. Instead, pluripotent cells employ alternative ways to defend against viruses that are typically associated with safeguard mechanisms against transposable elements. The absence of an inducible IFN response in pluripotent cells and the constitutive activation of the alternative antiviral pathways have led to the hypothesis that embryonic cells are highly resistant to viruses. However, some findings challenge this interpretation. We have performed a meta-analysis that suggests that the susceptibility of pluripotent cells to viruses is directly correlated with the presence of receptors or co-receptors for viral adhesion and entry. These results challenge the current view of pluripotent cells as intrinsically resistant to infections and raise the fundamental question of why these cells have sacrificed the major antiviral defence pathway if this renders them susceptible to viruses.

Protein Quality Control Systems and ER Stress as Key Players in SARS-CoV-2-Induced Neurodegeneration

The COVID-19 pandemic has brought to the forefront the intricate relationship between SARS-CoV-2 and its impact on neurological complications, including potential links to neurodegenerative processes, characterized by a dysfunction of the protein quality control systems and ER stress. This review article explores the role of protein quality control systems, such as the Unfolded Protein Response (UPR), the Endoplasmic Reticulum-Associated Degradation (ERAD), the Ubiquitin-Proteasome System (UPS), autophagy and the molecular chaperones, in SARS-CoV-2 infection. Our hypothesis suggests that SARS-CoV-2 produces ER stress and exploits the protein quality control systems, leading to a disruption in proteostasis that cannot be solved by the host cell. This disruption culminates in cell death and may represent a link between SARS-CoV-2 and neurodegeneration.

Mesenchymal stem cells (MSCs) from the mouse bone marrow show differential expression of interferon regulatory factors IRF-1 and IRF-2

BACKGROUND

Interferon regulatory factors (IRF-1 and IRF-2) are transcription factors widely implicated in various cellular processes, including regulation of inflammatory responses to pathogens, cell proliferation, oncogenesis, differentiation, autophagy, and apoptosis.

METHODS

We have studied the expression of IRF-1, IRF-2 mRNAs by RT-PCR, cellular localization of the proteins by immunofluorescence, and expression of mRNAs of genes regulated by IRF-1, IRF-2 by RT-PCR in mouse bone marrow cells (BMCs) and mesenchymal stem cells (MSCs).

RESULTS

Higher level of IRF-1 mRNA was observed in BMCs and MSCs compared to that of IRF-2. Similarly, differential expression of IRF-1 and IRF-2 proteins was observed in BMCs and MSCs. IRF-1 was predominantly localized in the cytoplasm, whereas IRF-2 was localized in the nuclei of BMCs. MSCs showed nucleo-cytoplasmic distribution of IRF-1 and nuclear localization of IRF-2. Constitutive expression of IRF-1 and IRF-2 target genes: monocyte chemoattractant protein-1 (MCP-1), vascular cell adhesion molecule-1 (VCAM-1), cyclooxygenase-2 (COX-2), matrix metalloproteinase-9 (MMP-9), and caspase-1 was observed in both BMCs and MSCs. MSCs showed constitutive expression of the pluripotency-associated factors, Oct3/4 and Sox-2. Lipopolysaccharide (LPS)-treatment of MSCs induced prominent cellular localization of IRF-1 and IRF-2.

CONCLUSIONS

Our results suggest that IRF-1 and IRF-2 exhibit differential expression of their mRNAs and subcellular localization of the proteins in BMCs and MSCs. These cells also show differential levels of constitutive expression of IRF-1 and IRF-2 target genes. This may regulate immune-responsive properties of BMCs and MSCs through IRF-1, IRF-2-dependent gene expression and protein-protein interaction. Regulating IRF-1 and IRF-2 may be helpful for immunomodulatory functions of MSCs for cell therapy and regenerative medicine.

OPTN-TBK1 axis and a role for PLK1 in HSV-1 infection

IMPORTANCE

Herpes simplex virus type 1 (HSV-1) is globally prevalent, with latent infections observed in up to 80% of the population. The virus is known for subverting host defense mechanisms and infiltrating the nervous system to establish latency in peripheral ganglia. Multiple stressors can reactivate the virus, and recurrent herpes has been linked to vision loss and neurodegeneration. Identifying critical host factors that limit the spread of HSV-1 and the subsequent establishment of latent infection holds the potential to drive new intervention strategies for eradicating the virus. Numerous pieces of evidence underscore the significance of Tank-binding kinase 1 (TBK1) in restricting HSV-1. Reports have also suggested that phosphorylation of optineurin (OPTN) by TBK1 is required for triggering OPTN-mediated autophagy for HSV degradation. This report adds new insights into the roles of OPTN and TBK1 in HSV-1 infection and provides proof of a TBK1-independent HSV-1 restriction through OPTN. It confirms that TBK1 activation can be substituted by PLK1 to provide protection against HSV-1. In contrast, the activation of OPTN is likely an indispensable host defense mechanism for optimal defense against HSV-1.

Role of HIF in fish inflammation

The hypoxia-inducing factor (HIF) is a central transcription factor in cellular oxygen sensing and regulation. It is common that the inflammation always appears in many diseases, like infectious diseases in fishes, and the inflammation is often accompanied by hypoxia, as a hallmark of inflammation. Besides coordinating cellular responses to low oxygen, HIF-mediated hypoxia signaling pathway is also crucial for immune responses such as the regulations of innate immune cell phenotype and function, as well as metabolic reprogramming under the inflammation. However, the understanding of the molecular mechanisms by which HIFs regulate the inflammatory response in fish is still very limited. Here, we review the characteristics of HIF as well as its roles in innate immune cells and the infections caused by bacteria and viruses. The regulatory effects of HIF on the metabolic reprogramming of innate immune cells are also discussed and the future research directions are outlooked. This paper will serve as a reference for elucidating the molecular mechanism of HIF regulating inflammation and identifying treatment strategies to target HIF for fish disease.

Antiviral effects of duck type I and type III interferons against Duck Tembusu virus in vitro and in vivo

Duck Tembusu Virus (DTMUV) is a newly emerging avian flavivirus that causes substantial economic losses to the duck industry in Asia by causing severe egg drop syndrome and fatal encephalitis in domestic ducks. During viral replication, host cells recognize the RNA structures produced by DTMUV, which triggers the production of interferons (IFNs) to inhibit viral replication. However, the function of duck type I and type III IFNs in inhibiting DTMUV infection remains largely unknown. In this study, we expressed and purified recombinant duck IFN-β (duIFN-β) and IFN-λ (duIFN-λ) in Escherichia coli and evaluated their antiviral activity against vesicular stomatitis virus (VSV). Furthermore, we found that both duIFN-β and duIFN-λ activated the ISRE promoter and induced the expression of ZAP, OAS, and RNaseL in duck embryo fibroblasts (DEFs). Notably, duIFN-β showed faster and more potent induction of ISGs in vitro and in vivo compared to duIFN-λ. Moreover, both duIFN-β and duIFN-λ showed high potential to inhibit DTMUV infection in DEFs, with duIFN-β demonstrating better antiviral efficacy than duIFN-λ against DTMUV in ducks. In conclusion, our results revealed that both duIFN-β and duIFN-λ can induce ISGs production and exhibit significant antiviral activity against DTMUV in vitro and in vivo, providing new insights for the development of antiviral therapeutic strategies in ducks.