Toll-like receptor expression and induction of type I and type III interferons in primary airway epithelial cells

Revisiting the Immunometabolic Basis for the Metabolic Syndrome from an Immunonutritional View

Metabolic syndrome (MetS) implies different conditions where insulin resistance constitutes a major hallmark of the disease. The disease incurs a high risk for the development of cardiovascular complications, and takes its toll in regard to the gut-liver axis (pancreas, primary liver and colorectal)-associated immunity. The modulation of immunometabolic responses by immunonutritional factors (IFs) has emerged as a key determinant of the gut-liver axis' metabolic and immune health. IFs from plant seeds have shown in vitro and pre-clinical effectiveness primarily in dealing with various immunometabolic and inflammatory diseases. Only recently have immunonutritional studies established the engagement of innate intestinal immunity to effectively control immune alterations in inflamed livers preceding the major features of the MetS. However, integrative analyses and the demonstration of causality between IFs and specific gut-liver axis-associated immunometabolic imbalances for the MetS remain ill-defined in the field. Herein, a better understanding of the IFs with a significant role in the MetS, as well as within the dynamic interplay in the functional differentiation of innate immune key effectors (i.e., monocytes/macrophages), worsening or improving the disease, could be of crucial relevance. The development of an adequate intermediary phenotype of these cells can significantly contribute to maintaining the function of Tregs and innate lymphoid cells for the prevention and treatment of MetS and associated comorbidities.

The RNA helicase DHX35 functions as a co-sensor for RIG-I-mediated innate immunity

RNA helicases are involved in the innate immune response against pathogens, including bacteria and viruses; however, their mechanism in the human airway epithelial cells is still not fully understood. Here, we demonstrated that DEAH (Asp-Glu-Ala-His) box polypeptide 35 (DHX35), a member of the DExD/H (Asp-Glu-x-Asp/His)-box helicase family, boosts antiviral innate immunity in human airway epithelial cells. DHX35 knockdown attenuated the production of interferon-β (IFN-β), IL6, and CXCL10, whereas DHX35 overexpression increased their production. Upon stimulation, DHX35 was constitutively expressed, but it translocated from the nucleus into the cytosol, where it recognized cytosolic poly(I:C) and poly(dA:dT) via its HELICc domain. Mitochondrial antiviral signaling protein (MAVS) acted as an adaptor for DHX35 and interacted with the HELICc domain of DHX35 using amino acids 360-510. Interestingly, DHX35 interacted with retinoic acid-inducible gene 1 (RIG-I), enhanced the binding affinity of RIG-I with poly(I:C) and poly(dA:dT), and formed a signalsome with MAVS to activate interferon regulatory factor 3 (IRF3), NF-κB-p65, and MAPK signaling pathways. These results indicate that DHX35 not only acted as a cytosolic nucleic acid sensor but also synergized with RIG-I to enhance antiviral immunity in human airway epithelial cells. Our results demonstrate a novel molecular mechanism for DHX35 in RIG-I-mediated innate immunity and provide a novel candidate for drug and vaccine design to control viral infections in the human airway.

IFN-λ drives distinct lung immune landscape changes and antiviral responses in human metapneumovirus infection

Human metapneumovirus (HMPV) is a primary cause of acute respiratory infection, yet there are no approved vaccines or antiviral therapies for HMPV. Early host responses to HMPV are poorly characterized, and further understanding could identify important antiviral pathways. Type III interferon (IFN-λ) displays potent antiviral activity against respiratory viruses and is being investigated for therapeutic use. However, its role in HMPV infection remains largely unknown. Here, we show that IFN-λ is highly upregulated during HMPV infection in vitro in human and mouse airway epithelial cells and in vivo in mice. We found through several immunological and molecular assays that type II alveolar cells are the primary producers of IFN-λ. Using mouse models, we show that IFN-λ limits lung HMPV replication and restricts virus spread from upper to lower airways but does not contribute to clinical disease. Moreover, we show that IFN-λ signaling is predominantly mediated by CD45- non-immune cells. Mice lacking IFN-λ signaling showed diminished loss of ciliated epithelial cells and decreased recruitment of lung macrophages in early HMPV infection along with higher inflammatory cytokine and interferon-stimulated gene expression, suggesting that IFN-λ may maintain immunomodulatory responses. Administration of IFN-λ for prophylaxis or post-infection treatment in mice reduced viral load without inflammation-driven weight loss or clinical disease. These data offer clinical promise for IFN-λ in HMPV treatment.

IMPORTANCE

Human metapneumovirus (HMPV) is a common respiratory pathogen and often contributes to severe disease, particularly in children, immunocompromised people, and the elderly. There are currently no licensed HMPV antiviral treatments or vaccines. Here, we report novel roles of host factor IFN-λ in HMPV disease that highlight therapeutic potential. We show that IFN-λ promotes lung antiviral responses by restricting lung HMPV replication and spread from upper to lower airways but does so without inducing lung immunopathology. Our data uncover recruitment of lung macrophages, regulation of ciliated epithelial cells, and modulation of inflammatory cytokines and interferon-stimulated genes as likely contributors. Moreover, we found these roles to be distinct and non-redundant, as they are not observed with knockout of, or treatment with, type I IFN. These data elucidate unique antiviral functions of IFN-λ and suggest IFN-λ augmentation as a promising therapeutic for treating HMPV disease and promoting effective vaccine responses.

Development of innate and adaptive immunity to RSV in young children

Infection of the respiratory tract with respiratory syncytial virus (RSV) is common and occurs repeatedly throughout life with most severe disease occurring at the extremes of age: in young infants and the elderly. Effective anti-viral therapeutics are not available and therefore prevention has been the primary strategy for reducing the disease burden. Our current understanding of respiratory mucosal cell biology and the immune response within the respiratory tract is inadequate to prevent infection caused by a pathogen like RSV that does not disseminate outside of this environment. Gaps in our understanding of the activation of innate and adaptive immunity in response to RSV and the role of age upon infection also limit improvements in the design of therapeutics and vaccines for young infants. However, advancements in structural biology have improved our ability to characterize antibodies against viral proteins and in 2023 the first vaccines for those over 60 years and pregnant women became available, potentially reducing the burden of disease. This review will examine our current understanding of the critical facets of anti-RSV immune responses in infants and young children as well as highlight areas where more research is needed.

Human long noncoding RNA, VILMIR, is induced by major respiratory viral infections and modulates the host interferon response

Long noncoding RNAs (lncRNAs) are a newer class of noncoding transcripts identified as key regulators of biological processes. Here we aimed to identify novel lncRNA targets that play critical roles in major human respiratory viral infections by systematically mining large-scale transcriptomic datasets. Using bulk RNA-sequencing (RNA-seq) analysis, we identified a previously uncharacterized lncRNA, named virus inducible lncRNA modulator of interferon response (VILMIR), that was consistently upregulated after in vitro influenza infection across multiple human epithelial cell lines and influenza A virus subtypes. VILMIR was also upregulated after SARS-CoV-2 and RSV infections in vitro. We experimentally confirmed the response of VILMIR to influenza infection and interferon-beta (IFN-β) treatment in the A549 human epithelial cell line and found the expression of VILMIR was robustly induced by IFN-β treatment in a dose and time-specific manner. Single cell RNA-seq analysis of bronchoalveolar lavage fluid (BALF) samples from COVID-19 patients uncovered that VILMIR was upregulated across various cell types including at least five immune cells. The upregulation of VILMIR in immune cells was further confirmed in the human T cell and monocyte cell lines, SUP-T1 and THP-1, after IFN-β treatment. Finally, we found that knockdown of VILMIR expression reduced the magnitude of host transcriptional responses to IFN-β treatment in A549 cells. Together, our results show that VILMIR is a novel interferon-stimulated gene (ISG) that regulates the host interferon response and may be a potential therapeutic target for human respiratory viral infections upon further mechanistic investigation.

Liquid application dosing alters the physiology of air-liquid interface (ALI) primary human bronchial epithelial cell/lung fibroblast co-cultures and in vitro testing relevant endpoints

Differentiated primary human bronchial epithelial cell (dpHBEC) cultures grown under air-liquid interface (ALI) conditions exhibit key features of the human respiratory tract and are thus critical for respiratory research as well as efficacy and toxicity testing of inhaled substances (e.g., consumer products, industrial chemicals, and pharmaceuticals). Many inhalable substances (e.g., particles, aerosols, hydrophobic substances, reactive substances) have physiochemical properties that challenge their evaluation under ALI conditions in vitro. Evaluation of the effects of these methodologically challenging chemicals (MCCs) in vitro is typically conducted by "liquid application," involving the direct application of a solution containing the test substance to the apical, air-exposed surface of dpHBEC-ALI cultures. We report that the application of liquid to the apical surface of a dpHBEC-ALI co-culture model results in significant reprogramming of the dpHBEC transcriptome and biological pathway activity, alternative regulation of cellular signaling pathways, increased secretion of pro-inflammatory cytokines and growth factors, and decreased epithelial barrier integrity. Given the prevalence of liquid application in the delivery of test substances to ALI systems, understanding its effects provides critical infrastructure for the use of in vitro systems in respiratory research as well as in the safety and efficacy testing of inhalable substances.

Toll-like receptor signalling via IRAK4 affects epithelial integrity and tightness through regulation of junctional tension

Toll-like receptors (TLRs) in mammalian systems are well known for their role in innate immunity. In addition, TLRs also fulfil crucial functions outside immunity, including the dorsoventral patterning function of the original Toll receptor in Drosophila and neurogenesis in mice. Recent discoveries in flies suggested key roles for TLRs in epithelial cells in patterning of junctional cytoskeletal activity. Here, we address the function of TLRs and the downstream key signal transduction component IRAK4 in human epithelial cells. Using differentiated human Caco-2 cells as a model for the intestinal epithelium, we show that these cells exhibit baseline TLR signalling, as revealed by p-IRAK4, and that blocking IRAK4 function leads to a loss of epithelial tightness involving key changes at tight and adherens junctions, such as a loss of epithelial tension and changes in junctional actomyosin. Changes upon IRAK-4 inhibition are conserved in human bronchial epithelial cells. Knockdown of IRAK4 and certain TLRs phenocopies the inhibitor treatment. These data suggest a model whereby TLR receptors near epithelial junctions might be involved in a continuous sensing of the epithelial state to promote epithelial tightness and integrity.

The role and application of three IFN-related reactions in psoriasis

The pathophysiology of psoriasis is a highly complicated one. Due to the disease's specificity, it not only affects the patient's skin negatively but also manifests systemic pathological changes. These clinical symptoms seriously harm the patient's physical and mental health. IFN, a common immunomodulatory factor, has been increasingly demonstrated to have a significant role in the development of psoriatic skin disease. Psoriasis is connected with a variety of immunological responses. New targets for the therapy of autoimmune skin diseases may emerge from further research on the mechanics of the associated IFN upstream and downstream pathways. Different forms of IFNs do not behave in the same manner in psoriasis, and understanding how different types of IFNs are involved in psoriasis may provide a better notion for future research. This review focuses on the involvement of three types of IFNs in psoriasis and related therapeutic investigations, briefly describing the three IFNs' production and signaling, as well as the dual effects of IFNs on the skin. It is intended that it would serve as a model for future research.

A mammalian lung's immune system minimizes tissue damage by initiating five major sequential phases of defense

The mammalian lungs encounter several pathogens, but have a sophisticated multi-phase immune defense. Furthermore, several immune responses to suppress pulmonary pathogens can damage the airway epithelial cells, particularly the vital alveolar epithelial cells (pneumocytes). The lungs have a sequentially activated, but overlapping, five phase immune response to suppress most pathogens, while causing minimal damage to the airway epithelial cells. Each phase of the immune response may suppress the pathogens, but if the previous phase proves inadequate, a stronger phase of immune response is activated, but with an increased risk of airway epithelial cell damage. The first phase immune response involves the pulmonary surfactants, which have proteins and phospholipids with potentially sufficient antibacterial, antifungal and antiviral properties to suppress many pathogens. The second phase immune response involves the type III interferons, having pathogen responses with comparatively minimal risk of damage to airway epithelial cells. The third phase immune response involves type I interferons, which implement stronger immune responses against pathogens with an increased risk of damage to airway epithelial cells. The fourth phase immune response involves the type II interferon, interferon-γ, which activates stronger immune responses, but with considerable risk of airway epithelial cell damage. The fifth phase immune response involves antibodies, potentially activating the complement system. In summary, five major phases of immune responses for the lungs are sequentially initiated to create an overlapping immune response which can suppress most pathogens, while usually causing minimal damage to the airway epithelial cells, including the pneumocytes.

Interferon-independent processes constrain measles virus cell-to-cell spread in primary human airway epithelial cells

Amplification of measles virus (MeV) in human airway epithelia may contribute to its extremely high contagious nature. We use well-differentiated primary cultures of human airway epithelial cells (HAE) to model ex vivo how MeV spreads in human airways. In HAE, MeV spreads cell-to-cell for 3-5 days, but then, infectious center growth is arrested. What stops MeV spread in HAE is not understood, but interferon (IFN) is known to slow MeV spread in other in vitro and in vivo models. Here, we assessed the role of type I and type III IFN in arresting MeV spread in HAE. The addition of IFN-β or IFN-λ1 to the medium of infected HAE slowed MeV infectious center growth, but when IFN receptor signaling was blocked, infectious center size was not affected. In contrast, blocking type-I IFN receptor signaling enhanced respiratory syncytial virus spread. HAE were also infected with MeV mutants defective for the V protein. The V protein has been demonstrated to interact with both MDA5 and STAT2 to inhibit activation of innate immunity; however, innate immune reactions were unexpectedly muted against the V-defective MeV in HAE. Minimal innate immunity activation was confirmed by deep sequencing, quantitative RT-PCR, and single-cell RNA-seq analyses of the transcription of IFN and IFN-stimulated genes. We conclude that in HAE, IFN-signaling can contribute to slowing infectious center growth; however, IFN-independent processes are most important for limiting cell-to-cell spread. IMPORTANCE Fundamental biological questions remain about the highly contagious measles virus (MeV). MeV amplifies within airway epithelial cells before spreading to the next host. This final step likely contributes to the ability of MeV to spread host-to-host. Over the course of 3-5 days post-infection of airway epithelial cells, MeV spreads directly cell-to-cell and forms infectious centers. Infectious center formation is unique to MeV. In this study, we show that interferon (IFN) signaling does not explain why MeV cell-to-cell spread is ultimately impeded within the cell layer. The ability of MeV to spread cell-to-cell in airway cells without appreciable IFN induction may contribute to its highly contagious nature. This study contributes to the understanding of a significant global health concern by demonstrating that infectious center formation occurs independent of the simplest explanation for limiting viral transmission within a host.

IFNλ: balancing the light and dark side in pulmonary infection

Interferon (IFN) represents a well-known component of antiviral immunity that has been studied extensively for its mechanisms of action and therapeutic potential when antiviral treatment options are limited. Specifically in the respiratory tract, IFNs are induced directly on viral recognition to limit the spread and transmission of the virus. Recent focus has been on the IFNλ family, which has become an exciting focus in recent years for its potent antiviral and anti-inflammatory activities against viruses infecting barrier sites, including the respiratory tract. However, insights into the interplay between IFNλs and other pulmonary infections are more limited and suggest a more complex role, potentially detrimental, than what was seen during viral infections. Here, we review the role of IFNλs in pulmonary infections, including viral, bacterial, fungal, and multi-pathogen super-infections, and how this may impact future work in the field.

The β6 Integrin Negatively Regulates TLR7-Mediated Epithelial Immunity via Autophagy During Influenza A Virus Infection

Integrins are essential surface receptors that sense extracellular changes to initiate various intracellular signaling cascades. The rapid activation of the epithelial-intrinsic β6 integrin during influenza A virus (IAV) infection has been linked to innate immune impairments. Yet, how β6 regulates epithelial immunity remains undefined. Here, we identify the role of β6 in mediating the Toll-like receptor 7 (TLR7) through the regulation of intracellular trafficking. We demonstrate that deletion of the β6 integrin in lung epithelial cells significantly enhances the TLR7-mediated activation of the type I interferon (IFN) response during homeostasis and respiratory infection. IAV-induced β6 facilitates TLR7 trafficking to lysosome-associated membrane protein (LAMP2a) components, leading to a reduction in endosomal compartments and associated TLR7 signaling. Our findings reveal an unappreciated role of β6-induced autophagy in influencing epithelial immune responses during influenza virus infection.

Viral recognition and the antiviral interferon response

Interferons (IFNs) are antiviral cytokines that play a key role in the innate immune response to viral infections. In response to viral stimuli, cells produce and release interferons, which then act on neighboring cells to induce the transcription of hundreds of genes. Many of these gene products either combat the viral infection directly, e.g., by interfering with viral replication, or help shape the following immune response. Here, we review how viral recognition leads to the production of different types of IFNs and how this production differs in spatial and temporal manners. We then continue to describe how these IFNs play different roles in the ensuing immune response depending on when and where they are produced or act during an infection.

When the allergy alarm bells toll: The role of Toll-like receptors in allergic diseases and treatment

Toll-like receptors of the human immune system are specialized pathogen detectors able to link innate and adaptive immune responses. TLR ligands include among others bacteria-, mycoplasma- or virus-derived compounds such as lipids, lipo- and glycoproteins and nucleic acids. Not only are genetic variations in TLR-related genes associated with the pathogenesis of allergic diseases, including asthma and allergic rhinitis, their expression also differs between allergic and non-allergic individuals. Due to a complex interplay of genes, environmental factors, and allergen sources the interpretation of TLRs involved in immunoglobulin E-mediated diseases remains challenging. Therefore, it is imperative to dissect the role of TLRs in allergies. In this review, we discuss i) the expression of TLRs in organs and cell types involved in the allergic immune response, ii) their involvement in modulating allergy-associated or -protective immune responses, and iii) how differential activation of TLRs by environmental factors, such as microbial, viral or air pollutant exposure, results in allergy development. However, we focus on iv) allergen sources interacting with TLRs, and v) how targeting TLRs could be employed in novel therapeutic strategies. Understanding the contributions of TLRs to allergy development allow the identification of knowledge gaps, provide guidance for ongoing research efforts, and built the foundation for future exploitation of TLRs in vaccine design.

Toll-like Receptor Response to Human Immunodeficiency Virus Type 1 or Co-Infection with Hepatitis B or C Virus: An Overview

Toll-like receptors (TLRs) are evolutionarily conserved pattern recognition receptors that play important roles in the early detection of pathogen-associated molecular patterns and shaping innate and adaptive immune responses, which may influence the consequences of infection. Similarly to other viral infections, human immunodeficiency virus type 1 (HIV-1) also modulates the host TLR response; therefore, a proper understanding of the response induced by human HIV-1 or co-infection with hepatitis B virus (HBV) or hepatitis C virus (HCV), due to the common mode of transmission of these viruses, is essential for understanding HIV-1 pathogenesis during mono- or co-infection with HBV or HCV, as well as for HIV-1 cure strategies. In this review, we discuss the host TLR response during HIV-1 infection and the innate immune evasion mechanisms adopted by HIV-1 for infection establishment. We also examine changes in the host TLR response during HIV-1 co-infection with HBV or HCV; however, this type of study is extremely scarce. Moreover, we discuss studies investigating TLR agonists as latency-reverting agents and immune stimulators towards new strategies for curing HIV. This understanding will help develop a new strategy for curing HIV-1 mono-infection or co-infection with HBV or HCV.

Liquid Application Dosing Alters the Physiology of Air-Liquid Interface Primary Bronchial Epithelial Cultures and In vitro Testing Relevant Endpoints

Differentiated Primary human bronchial epithelial cell (dpHBEC) cultures grown under air-liquid interface (ALI) conditions exhibit key features of the human respiratory tract and are thus critical for respiratory research as well as efficacy and toxicity testing of inhaled substances (e.g., consumer products, industrial chemicals, and pharmaceuticals). Many inhalable substances (e.g., particles, aerosols, hydrophobic substances, reactive substances) have physiochemical properties that challenge their evaluation under ALI conditions in vitro. Evaluation of the effects of these methodologically challenging chemicals (MCCs) in vitro is typically conducted by "liquid application," involving the direct application of a solution containing the test substance to the apical, air-exposed surface of dpHBEC-ALI cultures. We report that the application of liquid to the apical surface of a dpHBEC-ALI co-culture model results in significant reprogramming of the dpHBEC transcriptome and biological pathway activity, alternative regulation of cellular signaling pathways, increased secretion of pro-inflammatory cytokines and growth factors, and decreased epithelial barrier integrity. Given the prevalence of liquid application in the delivery of test substances to ALI systems, understanding its effects provides critical infrastructure for the use of in vitro systems in respiratory research as well as in the safety and efficacy testing of inhalable substances.

Exploring the Core Prescription and Underlying Mechanism of Traditional Chinese Medicine in Treating Allergic Rhinitis in Children: A Real- World Study Based on an Illustrious Senior Traditional Chinese Medicine Practitioner

BACKGROUND

Traditional Chinese medicine (TCM) is widely used to treat allergic rhinitis (AR) in China, especially in children. However, due to the complicated composition rules and unclear underlying mechanisms, effective herbal prescriptions' popularization and application are limited.

PURPOSE

This study tried to detect the core prescription of herbs in treating AR in children, reveal its mechanism based on the ingredients' network, and explore the main signaling pathways.

METHODS

We screened medical records of children patients with AR who were treated by TCM in DongZhiMen Hospital from Aug 2009 to Jan 2020 and adopted a descriptive analysis method on herbal characteristics. We used association rules to mine core prescriptions and used network pharmacology to establish the ingredient-target-pathway network through online databases and TCMSP, Genecards, KEGG pathway, Excel, R-Studio, and Cytoscape software.

RESULTS

The analysis of 1,092 clinical visits highlighted that the principle of formulating prescription was as follows: 'pungent and warm herbs were used more frequently while cold-natured herbs were paid equal attention as warm-natured herbs.' The core prescription was formed by FangFeng, BaiZhi, CangErzi, and ChanTui. These herbs covered 130 underlying targets and 141 signaling pathways of AR, which mainly had an effect on signal transduction and immunoregulation.

CONCLUSION

The core prescription based on these real-world clinical records includes FangFeng, BaiZhi, CangErzi, and ChanTui. It principally acts on targets of signal transduction pathways and immune pathways.

The subversion of toll-like receptor signaling by bacterial and viral proteases during the development of infectious diseases

Toll-like receptors (TLRs) are pattern recognition receptors (PRRs) that respond to pathogen-associated molecular patterns (PAMPs). The recognition of specific microbial ligands by TLRs triggers an innate immune response and also promotes adaptive immunity, which is necessary for the efficient elimination of invading pathogens. Successful pathogens have therefore evolved strategies to subvert and/or manipulate TLR signaling. Both the impairment and uncontrolled activation of TLR signaling can harm the host, causing tissue destruction and allowing pathogens to proliferate, thus favoring disease progression. In this context, microbial proteases are key virulence factors that modify components of the TLR signaling pathway. In this review, we discuss the role of bacterial and viral proteases in the manipulation of TLR signaling, highlighting the importance of these enzymes during the development of infectious diseases.

The gamble between oncolytic virus therapy and IFN

Various studies are being conducted on oncolytic virotherapy which one of the mechanisms is mediating interferon (IFN) production by it exerts antitumor effects. The antiviral effect of IFN itself has a negative impact on the inhibition of oncolytic virus or tumor eradication. Therefore, it is very critical to understand the mechanism of IFN regulation by oncolytic viruses, and to define its mechanism is of great significance for improving the antitumor effect of oncolytic viruses. This review focuses on the regulatory mechanisms of IFNs by various oncolytic viruses and their combination therapies. In addition, the exerting and the producing pathways of IFNs are briefly summarized, and some current issues are put forward.

In Vivo and In Vitro Studies of Cigarette Smoke Effects on Innate Responses to Influenza Virus: A Matter of Models?

Cigarette smoke (CS) is a significant public health problem and a leading risk factor for the development of chronic obstructive pulmonary disease (COPD) in the developed world. Respiratory viral infections, such as the influenza A virus (IAV), are associated with acute exacerbations of COPD and are more severe in cigarette smokers. To fight against viral infection, the host has developed an innate immune system, which has complicated mechanisms regulating the expression and activation of cytokines and chemokines to maximize the innate and adaptive antiviral response, as well as limiting the immunopathology that leads to exaggerated lung damage. In the case of IAV, responders include airway and alveolar epithelia, lung macrophages and dendritic cells. To achieve a successful infection, IAV must overcome these defenses. In this review, we summarize the detrimental role of CS in influenza infections. This includes both immunosuppressive and proinflammatory effects on innate immune responses during IAV infection. Some of the results, with respect to CS effects in mouse models, appear to have discordant results, which could be at least partially addressed by standardization of animal viral infection models to evaluate the effect of CS exposure in this context.

Exosomal microRNA expression profiles derived from A549 human lung cells in response to influenza A/H1N1pdm09 infection

Exosomes participate in intercellular communication by shuttling various small molecules from donor to recipient cells. We aimed to examine the role of exosomes and exosomal miRNAs in influenza virus infection. The results showed that influenza A/H1N1pdm09 infection could promote A549 cells to secrete exosomes, while blocking the generation of exosomes reduced viral RNA production. A total of 97 exosomal miRNAs with significantly altered expression were identified during influenza infection. Of 12 candidate miRNAs chosen for further validation, ten were confirmed by qRT-PCR. Among 5978 predicted target genes，we found 37 interferon pathway-related genes to be the potential targets of 29 differentially expressed miRNAs. Many target genes were annotated to various KEGG signaling pathways, some of which played important roles in influenza infection. These data will help to further understand the mechanism of influenza virus-host interactions, which is important for the development of preventative and therapeutic strategies against influenza virus.

MAVS Expression in Alveolar Macrophages Is Essential for Host Resistance against Aspergillus fumigatus

Our recent data demonstrate a critical role of the RIG-I-like receptor family in regulating antifungal immunity against Aspergillus fumigatus in a murine model. However, the importance of this pathway in humans and the cell types that use this innate immune receptor family to detect A. fumigatus remain unresolved. In this study, using patients who underwent hematopoietic stem cell transplantation, we demonstrate that a polymorphism in human MAVS present in the donor genome was associated with the incidence of invasive pulmonary aspergillosis. Moreover, in a separate cohort of confirmed invasive pulmonary aspergillosis patients, polymorphisms in the IFIH1 gene alter the inflammatory response, including IFN-responsive chemokines. Returning to our murine model, we now demonstrate that CD11c+ Siglec F+ alveolar macrophages require Mavs expression to maintain host resistance against A. fumigatus. Our data support the role of MAVS signaling in mediating antifungal immunity in both mice and humans at least in part through the role of MAVS-dependent signaling in alveolar macrophages.

Prospects on Repurposing a Live Attenuated Vaccine for the Control of Unrelated Infections

Live vaccines use attenuated microbes to acquire immunity against pathogens in a safe way. As live attenuated vaccines (LAVs) still maintain infectivity, the vaccination stimulates diverse immune responses by mimicking natural infection. Induction of pathogen-specific antibodies or cell-mediated cytotoxicity provides means of specific protection, but LAV can also elicit unintended off-target effects, termed non-specific effects. Such mechanisms as short-lived genetic interference and non-specific innate immune response or long-lasting trained immunity and heterologous immunity allow LAVs to develop resistance to subsequent microbial infections. Based on their safety and potential for interference, LAVs may be considered as an alternative for immediate mitigation and control of unexpected pandemic outbreaks before pathogen-specific therapeutic and prophylactic measures are deployed.

Extracellular Nucleotides and Histamine Suppress TLR3- and RIG-I-Mediated Release of Antiviral IFNs from Human Airway Epithelial Cells

Respiratory viruses stimulate the release of antiviral IFNs from the airway epithelium. Previous studies have shown that asthmatic patients show diminished release of type I and type III IFNs from bronchial epithelia. However, the mechanism of this suppression is not understood. In this study, we report that extracellular nucleotides and histamine, which are elevated in asthmatic airways, strongly inhibit release of type I and type III IFNs from human bronchial airway epithelial cells (AECs). Specifically, ATP, UTP, and histamine all inhibited the release of type I and type III IFNs from AECs induced by activation of TLR3, retinoic acid-inducible gene I (RIG-I), or cyclic GMP-AMP synthase-STING. This inhibition was at least partly mediated by Gq signaling through purinergic P2Y2 and H1 receptors, but it did not involve store-operated calcium entry. Pharmacological blockade of protein kinase C partially reversed inhibition of IFN production. Conversely, direct activation of protein kinase C with phorbol esters strongly inhibited TLR3- and RIG-I-mediated IFN production. Inhibition of type I and type III IFNs by ATP, UTP, histamine, and the proteinase-activated receptor 2 (PAR2) receptor agonist SLIGKV also occurred in differentiated AECs grown at an air-liquid interface, indicating that the suppression is conserved following mucociliary differentiation. Importantly, histamine and, more strikingly, ATP inhibited type I IFN release from human airway cells infected with live influenza A virus or rhinovirus 1B. These results reveal an important role for extracellular nucleotides and histamine in attenuating the induction of type I and III IFNs from AECs and help explain the molecular basis of the suppression of IFN responses in asthmatic patients.

Modeling Innate Antiviral Immunity in Physiological Context

An effective innate antiviral response is critical for the mitigation of severe disease and host survival following infection. In vivo, the innate antiviral response is triggered by cells that detect the invading pathogen and then communicate through autocrine and paracrine signaling to stimulate the expression of genes that inhibit viral replication, curtail cell proliferation, or modulate the immune response. In other words, the innate antiviral response is complex and dynamic. Notably, in the laboratory, culturing viruses and assaying viral life cycles frequently utilizes cells that are derived from tissues other than those that support viral replication during natural infection, while the study of viral pathogenesis often employs animal models. In recapitulating the human antiviral response, it is important to consider that variation in the expression and function of innate immune sensors and antiviral effectors exists across species, cell types, and cell differentiation states, as well as when cells are placed in different contexts. Thus, to gain novel insight into the dynamics of the host response and how specific sensors and effectors impact infection kinetics by a particular virus, the model system must be selected carefully. In this review, we briefly introduce key signaling pathways involved in the innate antiviral response and highlight how these differ between systems. We then review the application of tissue-engineered or 3D models for studying the antiviral response, and suggest how these in vitro culture systems could be further utilized to assay physiologically-relevant host responses and reveal novel insight into virus-host interactions.

Reprogramming cholesterol metabolism in macrophages and its role in host defense against cholesterol-dependent cytolysins

Cholesterol is a critical lipid for all mammalian cells, ensuring proper membrane integrity, fluidity, and biochemical function. Accumulating evidence indicates that macrophages rapidly and profoundly reprogram their cholesterol metabolism in response to activation signals to support host defense processes. However, our understanding of the molecular details underlying how and why cholesterol homeostasis is specifically reshaped during immune responses remains less well understood. This review discusses our current knowledge of cellular cholesterol homeostatic machinery and introduces emerging concepts regarding how plasma membrane cholesterol is partitioned into distinct pools. We then discuss how proinflammatory signals can markedly reshape the cholesterol metabolism of macrophages, with a focus on the differences between MyD88-dependent pattern recognition receptors and the interferon signaling pathway. We also discuss recent work investigating the capacity of these proinflammatory signals to selectively reshape plasma membrane cholesterol homeostasis. We examine how these changes in plasma membrane cholesterol metabolism influence sensitivity to a set of microbial pore-forming toxins known as cholesterol-dependent cytolysins that specifically target cholesterol for their effector functions. We also discuss whether lipid metabolic reprogramming can be leveraged for therapy to mitigate tissue damage mediated by cholesterol-dependent cytolysins in necrotizing fasciitis and other related infections. We expect that advancing our understanding of the crosstalk between metabolism and innate immunity will help explain how inflammation underlies metabolic diseases and highlight pathways that could be targeted to normalize metabolic homeostasis in disease states.

Ingestion, Immunity, and Infection: Nutrition and Viral Respiratory Tract Infections

Respiratory infections place a heavy burden on the health care system, particularly in the winter months. Individuals with a vulnerable immune system, such as very young children and the elderly, and those with an immune deficiency, are at increased risk of contracting a respiratory infection. Most respiratory infections are relatively mild and affect the upper respiratory tract only, but other infections can be more serious. These can lead to pneumonia and be life-threatening in vulnerable groups. Rather than focus entirely on treating the symptoms of infectious disease, optimizing immune responsiveness to the pathogens causing these infections may help steer towards a more favorable outcome. Nutrition may have a role in such prevention through different immune supporting mechanisms. Nutrition contributes to the normal functioning of the immune system, with various nutrients acting as energy sources and building blocks during the immune response. Many micronutrients (vitamins and minerals) act as regulators of molecular responses of immune cells to infection. It is well described that chronic undernutrition as well as specific micronutrient deficiencies impair many aspects of the immune response and make individuals more susceptible to infectious diseases, especially in the respiratory and gastrointestinal tracts. In addition, other dietary components such as proteins, pre-, pro- and synbiotics, and also animal- and plant-derived bioactive components can further support the immune system. Both the innate and adaptive defense systems contribute to active antiviral respiratory tract immunity. The initial response to viral airway infections is through recognition by the innate immune system of viral components leading to activation of adaptive immune cells in the form of cytotoxic T cells, the production of neutralizing antibodies and the induction of memory T and B cell responses. The aim of this review is to describe the effects of a range different dietary components on anti-infective innate as well as adaptive immune responses and to propose mechanisms by which they may interact with the immune system in the respiratory tract.

TLR7 agonist loaded airway epithelial targeting nanoparticles stimulate innate immunity and suppress viral replication in human bronchial epithelial cells

Nanoparticle-based delivery is a strategy for increasing the therapeutic window of inhaled immunomodulatory drugs that have inflammatory activity. TLR7 agonists are a class of immunomodulators that have been considered for the treatment of virus-induced respiratory diseases. However, due to high immune-stimulatory activity, TLR7 agonists, delivered via direct exposure, generally have a narrow therapeutic window. To address this, we have developed lipid/polymer hybrid nanoparticles (NPs) conjugated with anti-EpCAM monoclonal antibody for targeted delivery of TLR7 agonist (CL264) to airway epithelial cells (AECs)² - the primary site of respiratory virus infection. These airway epithelial targeting nanoparticles (AEC-NPs)³ showed safety and biocompatibility, and approximately two-fold increased cellular uptake compared to non-targeting NPs. Upon cell entry, AEC-NPs were able to deliver CL264 to cytoplasm and endosomes where TLR7 is located. CL264 delivered by AEC-NPs significantly increased innate immune response through expression of IFN-β, IFN-λ 2/3 and IFN-stimulated genes and suppressed more than 92% of viral load at 48 hours post-infection compared to the drug alone and non-targeting NPs. In conclusion, AEC-NPs exhibited increased cellular uptake leading to enhanced innate immune activation and suppression of viral replication. These findings support the use of AEC-targeting approach for delivering drugs with a narrow therapeutic window.

Deciphering Respiratory-Virus-Associated Interferon Signaling in COPD Airway Epithelium

COPD is a chronic lung disorder characterized by a progressive and irreversible airflow obstruction, and persistent pulmonary inflammation. It has become a global epidemic affecting 10% of the population, and is the third leading cause of death worldwide. Respiratory viruses are a primary cause of COPD exacerbations, often leading to secondary bacterial infections in the lower respiratory tract. COPD patients are more susceptible to viral infections and associated severe disease, leading to accelerated lung function deterioration, hospitalization, and an increased risk of mortality. The airway epithelium plays an essential role in maintaining immune homeostasis, and orchestrates the innate and adaptive responses of the lung against inhaled and pathogen insults. A healthy airway epithelium acts as the first line of host defense by maintaining barrier integrity and the mucociliary escalator, secreting an array of inflammatory mediators, and initiating an antiviral state through the interferon (IFN) response. The airway epithelium is a major site of viral infection, and the interaction between respiratory viruses and airway epithelial cells activates host defense mechanisms, resulting in rapid virus clearance. As such, the production of IFNs and the activation of IFN signaling cascades directly contributes to host defense against viral infections and subsequent innate and adaptive immunity. However, the COPD airway epithelium exhibits an altered antiviral response, leading to enhanced susceptibility to severe disease and impaired IFN signaling. Despite decades of research, there is no effective antiviral therapy for COPD patients. Herein, we review current insights into understanding the mechanisms of viral evasion and host IFN antiviral defense signaling impairment in COPD airway epithelium. Understanding how antiviral mechanisms operate in COPD exacerbations will facilitate the discovery of potential therapeutic interventions to reduce COPD hospitalization and disease severity.

Human rhinovirus serotypes induces different immune responses

Background

Different species of human rhinovirus (HRV) can induce varied antiviral and inflammatory responses in human blood macrophages and lower airway epithelium. Although human nasal epithelial cells (HNECs) are a primary infection route of HRV, differences between major and minor groups of HRV in the upper airway epithelium have not been studied in detail. In this study, we investigated viral replications and immune responses of major and minor groups of HRV in the HNECs.

Methods

Viral replication, immune responses of IFN-β, IFN-λ, proinflammatory cytokines, and viral receptors, and mRNA expression of transcription factors of HRV16 (major group) and HRV1B (minor group) in the HNECs were assessed.

Results

Compared with HRV16, HRV1B replicated more actively without excessive cell death and produced higher IFN-β, IFN-λ1/3, CXCL10, IL-6, IL-8, and IL-18 levels. Furthermore, low-density lipoprotein receptor (LDLR), TLR3, MDA5, NF-κB, STAT1, and STAT2 mRNA levels increased in HRV1B-infected HNECs.

Conclusion

HRV1B induces a stronger antiviral and inflammatory response from cell entry to downstream signaling compared with HRV16.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-021-01701-1.

Interferon Lambda Signaling in Macrophages Is Necessary for the Antiviral Response to Influenza

Interferon lambda (IFNλ) signaling is a promising therapeutic target against viral infection in murine models, yet little is known about its molecular regulation and its cognate receptor, interferon lambda receptor 1 (IFNLR1) in human lung. We hypothesized that the IFNλ signaling axis was active in human lung macrophages. In human alveolar macrophages (HAMs), we observed increased IFNLR1 expression and robust increase in interferon-stimulated gene (ISG) expression in response to IFNλ ligand. While human monocytes express minimal IFNLR1, differentiation of monocytes into macrophages with macrophage colony-stimulating factor (M-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF) increased IFNLR1 mRNA, IFNLR1 protein expression, and cellular response to IFNλ ligation. Conversely, in mice, M-CSF or GM-CSF stimulated macrophages failed to produce ISGs in response to related ligands, IFNL2 or IFNL3, suggesting that IFNLR1 signaling in macrophages is species-specific. We next hypothesized that IFNλ signaling was critical in influenza antiviral responses. In primary human airway epithelial cells and precision-cut human lung slices, influenza infection substantially increased IFNλ levels. Pretreatment of both HAMs and differentiated human monocytes with IFNL1 significantly inhibited influenza infection. IFNLR1 knockout in the myeloid cell line, THP-1, exhibited reduced interferon responses to either direct or indirect exposure to influenza infection suggesting the indispensability of IFNLR1 for antiviral responses. These data demonstrate the presence of IFNλ - IFNLR1 signaling axis in human lung macrophages and a critical role of IFNλ signaling in combating influenza infection.

Antiviral Gene Expression in Young and Aged Murine Lung during H1N1 and H3N2

Influenza is a respiratory virus that alone or in combination with secondary bacterial pathogens can contribute to the development of acute pneumonia in persons >65 years of age. Host innate immune antiviral signaling early in response to influenza is essential to inhibit early viral replication and guide the initiation of adaptive immune responses. Using young adult (3 months) and aged adult mice infected with mouse adapted H1N1 or H3N2, the results of our study illustrate dysregulated and/or diminished activation of key signaling pathways in aged lung contribute to increased lung inflammation and morbidity. Specifically, within the first seven days of infection, there were significant changes in genes associated with TLR and RIG-I signaling detected in aged murine lung in response to H1N1 or H3N2. Taken together, the results of our study expand our current understanding of age-associated changes in antiviral signaling in the lung.

A TLR7 antagonist restricts interferon-dependent and -independent immunopathology in a mouse model of severe influenza

Cytokine-mediated immune-cell recruitment and inflammation contribute to protection in respiratory virus infection. However, uncontrolled inflammation and the "cytokine storm" are hallmarks of immunopathology in severe infection. Cytokine storm is a broad term for a phenomenon with diverse characteristics and drivers, depending on host genetics, age, and other factors. Taking advantage of the differential use of virus-sensing systems by different cell types, we test the hypothesis that specifically blocking TLR7-dependent, immune cell-produced cytokines reduces influenza-related immunopathology. In a mouse model of severe influenza characterized by a type I interferon (IFN-I)-driven cytokine storm, TLR7 antagonist treatment leaves epithelial antiviral responses unaltered but acts through pDCs and monocytes to reduce IFN-I and other cytokines in the lung, thus ameliorating inflammation and severity. Moreover, even in the absence of IFN-I signaling, TLR7 antagonism reduces inflammation and mortality driven by monocyte-produced chemoattractants and neutrophil recruitment into the infected lung. Hence, TLR7 antagonism reduces diverse types of cytokine storm in severe influenza.

The effect of recombinant human interferon α1b treatment of infants hospitalized with lower respiratory tract infection on subsequent wheezing

OBJECTIVE

To investigate the impact of recombinant human interferon α1b (rhIFNα1b) treatment in infants hospitalized with lower respiratory tract infections on subsequent wheezing.

METHODS

The clinical data of infants (n=540) with viral pneumonia, wheezy bronchitis, or bronchiolitis hospitalized in 19 Chinese hospitals from June 2009 to June 2015 were retrospectively analyzed. The parameters relevant to wheezing episodes within the last year were collected by telephone and questionnaires. The rhIFNα1b treatment group (n=253) and control group (n=287) were compared in terms of wheezing episodes within the last year. Moreover, the wheezing group (95 cases) and non-wheezing group (445 cases) were compared.

RESULTS

Out of 540 cases, 95 (17.6%) experienced wheezing episodes, 13.8% (35/253) cases treated with rhIFNα1b, and 20.9% (60/287) cases without rhIFNα1b experienced wheezing episodes within the last year. The rhIFNα1b treatment significantly improved wheezing episodes within the last year, compared with the control peers (p=0.031). Single-factor regression showed statistically significant differences between the wheezing and non-wheezing groups in terms of age, rhIFNα1b use, childhood and family history of allergy, housing situation, and feeding history (p<0.05). Binary logistic regression showed a childhood history of allergy (OR=2.14, p=0.004), no rhIFNα1b use (OR=1.70, p=0.028), and living in a crowded house (OR=1.92, p=0.012) might be risk factors of subsequent wheezing. Accordingly, breastfeeding (OR=0.44, p=0.008) and hospitalization age of ≤1-year-old (OR=0.58, p=0.024) were protective factors.

CONCLUSIONS

Early use of rhIFNα1b in infants hospitalized with lower respiratory tract infections and breastfeeding could prevent subsequent wheezing. Living in a crowded house could promote subsequent wheezing.

Current Understanding of the Innate Control of Toll-like Receptors in Response to SARS-CoV-2 Infection

The global coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection, threatens the entire world. It has affected every aspect of life and increased the burden on both healthcare and socioeconomic systems. Current studies have revealed that excessive inflammatory immune responses are responsible for the severity of COVID-19, which suggests that anti-inflammatory drugs may be promising therapeutic treatments. However, there are currently a limited number of approved therapeutics for COVID-19. Toll-like receptors (TLRs), which recognize microbial components derived from invading pathogens, are involved in both the initiation of innate responses against SARS-CoV-2 infection and the hyperinflammatory phenotype of COVID-19. In this review, we provide current knowledge on the pivotal role of TLRs in immune responses against SARS-CoV-2 infection and demonstrate the potential effectiveness of TLR-targeting drugs on the control of hyperinflammation in patients with COVID-19.

Innate Immune Responses to Influenza Virus Infections in the Upper Respiratory Tract

The innate immune system is the host's first line of immune defence against any invading pathogen. To establish an infection in a human host the influenza virus must replicate in epithelial cells of the upper respiratory tract. However, there are several innate immune mechanisms in place to stop the virus from reaching epithelial cells. In addition to limiting viral replication and dissemination, the innate immune system also activates the adaptive immune system leading to viral clearance, enabling the respiratory system to return to normal homeostasis. However, an overzealous innate immune system or adaptive immune response can be associated with immunopathology and aid secondary bacterial infections of the lower respiratory tract leading to pneumonia. In this review, we discuss the mechanisms utilised by the innate immune system to limit influenza virus replication and the damage caused by influenza viruses on the respiratory tissues and how these very same protective immune responses can cause immunopathology.

Sex Hormones and Aging Modulate Interferon Lambda 1 Production and Signaling by Human Uterine Epithelial Cells and Fibroblasts

Estradiol (E2) and progesterone (P) have potent effects on immune function in the human uterine endometrium which is essential for creating an environment conducive for successful reproduction. Type III/lambda (λ) interferons (IFN) are implicated in immune defense of the placenta against viral pathogens, which occurs against the backdrop of high E2 and P levels. However, the effect of E2 and P in modulating the expression and function of IFNλ1 in the non-pregnant human uterine endometrium is unknown. We generated purified in vitro cultures of human uterine epithelial cells and stromal fibroblast cells recovered from hysterectomy specimens. Poly (I:C), a viral dsRNA mimic, potently increased secretion of IFNλ1 by both epithelial cells and fibroblasts. The secretion of IFNλ1 by epithelial cells significantly increased with increasing age following poly (I:C) stimulation. Stimulation of either cell type with E2 (5x10-8M) or P (1x10-7M) had no effect on expression or secretion of IFNλ1 either alone or in the presence of poly (I:C). E2 suppressed the IFNλ1-induced upregulation of the antiviral IFN-stimulated genes (ISGs) MxA, OAS2 and ISG15 in epithelial cells, but not fibroblasts. Estrogen receptor alpha (ERα) blockade using Raloxifene indicated that E2 mediated its inhibitory effects on ISG expression via ERα. In contrast to E2, P potentiated the upregulation of ISG15 in response to IFNλ1 but had no effect on MxA and OAS2 in epithelial cells. Our results demonstrate that the effects of E2 and P on IFNλ1-induced ISGs are cell-type specific. E2-mediated suppression, and selective P-mediated stimulation, of IFNλ1-induced ISG expression in uterine epithelial cells suggest that the effects of IFNλ1 varies with menstrual cycle stage, pregnancy, and menopausal status. The suppressive effect of E2 could be a potential mechanism by which ascending pathogens from the lower reproductive tract can infect the pregnant and non-pregnant endometrium.

Clean and folded: Production of active, high quality recombinant human interferon-λ1

Type III interferons exhibit antiviral activity against influenza viruses, coronaviruses, rotaviruses, and others. In addition, this type of interferon theoretically has therapeutic advantages, in comparison with type I interferons, due to its ability to activate a narrower group of genes in a relatively small group of target cells. Hence, it can elicit more targeted antiviral or immunomodulatory responses. Obtaining biologically-active interferon lambda (hIFN-λ₁) is fraught with difficulties at the stage of expression in soluble form or, in the case of expression in the form of inclusion bodies, at the stage of refolding. In this work, hIFN-λ₁ was expressed in the form of inclusion bodies, and a simple, effective refolding method was developed. Efficient and scalable methods for chromatographic purification of recombinant hIFN-λ₁ were also developed. High-yield, high-purity product was obtained through optimization of several processes including: recombinant protein expression; metal affinity chromatography; cation exchange chromatography; and an intermediate protein refolding stage. The obtained protein was shown to feature expected specific biological activity in line with published effects: induction of MxA gene expression in A549 cells and antiviral activity against influenza A virus.

The role of exosomes from BALF in lung disease

Exosomes are released from a variety of immune cells and nonimmune cells, the phospholipid vesicle bilayer membrane structure actively secreted into tissues. Recently, exosomes were demonstrated to be effectively delivered proteins, cholesterol, lipids, and amounts of DNA, mRNA, and noncoding RNAs to a target cell or tissue from a host cell. These can be detected in blood, urine, exhaled breath condensates, bronchoalveolar lavage fluid (BALF), ascites, and cerebrospinal fluid. BALF is a clinical examination method for obtaining alveolar cells and biochemical components, reflecting changes in the lungs, so it is also called liquid biopsy. Exosomes from BALF become a new method for intercellular communication and well‐documented in various pulmonary diseases. In chronic obstructive pulmonary disease (COPD), BALF exosomes can predict the degree of COPD damage and serve as an effective monitoring indicator for airflow limitation and airway remodeling. It also mediates antigen presentation in the airways to the adaptive immune system as well as costimulatory effects. Furthermore, BALF exosomes from acute lung injury and infective diseases are closely related to various infections and lack of oxygen status. BALF exosomes play an important role in the diagnosis and prognosis of lung cancer. The effect of immunomodulatory role for BALF exosomes in adaptive and innate immune responses has been studied in sarcoidosis. The intercellular communication in the microenvironment of BALF exosomes in pulmonary fibrosis and lung remodeling have been studied. In this review, we summarize the novel findings of exosomes in BALF, executed function by protein, miRNA, DNA cytokine, and so on in several pulmonary diseases.

Depleting plasmacytoid dendritic cells reduces local type I interferon responses and disease activity in patients with cutaneous lupus

Plasmacytoid dendritic cells (pDCs) not only are specialized in their capacity to secrete large amounts of type I interferon (IFN) but also serve to enable both innate and adaptive immune responses through expression of additional proinflammatory cytokines, chemokines, and costimulatory molecules. Persistent activation of pDCs has been demonstrated in a number of autoimmune diseases. To evaluate the potential benefit of depleting pDCs in autoimmunity, a monoclonal antibody targeting the pDC-specific marker immunoglobulin-like transcript 7 was generated. This antibody, known as VIB7734, which was engineered for enhanced effector function, mediated rapid and potent depletion of pDCs through antibody-dependent cellular cytotoxicity. In cynomolgus monkeys, treatment with VIB7734 reduced pDCs in blood below the lower limit of normal by day 1 after the first dose. In two phase 1 studies in patients with autoimmune diseases, VIB7734 demonstrated an acceptable safety profile, comparable to that of placebo. In individuals with cutaneous lupus, VIB7734 profoundly reduced both circulating and tissue-resident pDCs, with a 97.6% median reduction in skin pDCs at study day 85 in VIB7734-treated participants. Reductions in pDCs in the skin correlated with a decrease in local type I IFN activity as well as improvements in clinical disease activity. Biomarker analysis suggests that responsiveness to pDC depletion therapy may be greater among individuals with high baseline type I IFN activity, supporting a central role for pDCs in type I IFN production in autoimmunity and further development of VIB7734 in IFN-associated diseases.

COVID-19 virtual patient cohort suggests immune mechanisms driving disease outcomes

To understand the diversity of immune responses to SARS-CoV-2 and distinguish features that predispose individuals to severe COVID-19, we developed a mechanistic, within-host mathematical model and virtual patient cohort. Our results suggest that virtual patients with low production rates of infected cell derived IFN subsequently experienced highly inflammatory disease phenotypes, compared to those with early and robust IFN responses. In these in silico patients, the maximum concentration of IL-6 was also a major predictor of CD8+ T cell depletion. Our analyses predicted that individuals with severe COVID-19 also have accelerated monocyte-to-macrophage differentiation mediated by increased IL-6 and reduced type I IFN signalling. Together, these findings suggest biomarkers driving the development of severe COVID-19 and support early interventions aimed at reducing inflammation.

Local memory CD4 T cell niches in respiratory viral infection

Respiratory viral infections present a major threat to global health and prosperity. Over the past century, several have developed into crippling pandemics, including the SARS-CoV-2 virus. Although the generation of neutralizing serum antibodies in response to natural immunity and vaccination are considered to be hallmarks of viral immune protection, antibodies from long-lived plasma cells are subject to immune escape from heterologous clades of zoonotic, recombined, or mutated viruses. Local immunity in the lung can be generated through resident memory immune subsets that rapidly respond to secondary infection and protect from heterologous infection. Although many immune cells are required to achieve the phenomenon of resident memory, herein we highlight the pleiotropic functions of CD4 tissue resident memory T cells in the lung and discuss the implications of resident memory for vaccine design.

Immunomodulatory Responses Of Toll Like Receptors Against 2019nCoV

The present review discusses the immune signals via toll like receptors (TLRs) against 2019nCoV. We researched using different database, up to June 18th, 2020. All the included articles were published in English language. The outcome of this review, that some TLRs agonists or antagonists are progressed as drugs to combat and down regulating TLRs immune signals respectively. TLRs 3 and 4 recognized 2019nCoV spike protein through immune and molecular signals that leading to immune stimulation of pro-inflammatory cytokines and even the immune fever. While the TLRs7 and 8 recognized single-stranded ribonucleic acids (ssRNAs) leading to elevation of the tumour necrosis factor α (TNF-α), interleukin (IL)-6 and -12 levels. TLRs agonists or antagonists utilized as immunotherapeutic targets against 2019nCoV via TLRs signals. Chloroquine and hydroxychloroquine; the approval compounds for 2019nCoV therapy can be inhibiting the class II major histocompatibility complex molecules expression and antigen presentation and even immune suppressions of the pro-inflammatory cytokines profile.

Comparative Analysis of Public RNA-Sequencing Data from Human Intestinal Enteroid (HIEs) Infected with Enteric RNA Viruses Identifies Universal and Virus-Specific Epithelial Responses

Acute gastroenteritis (AGE) has a significant disease burden on society. Noroviruses, rotaviruses, and astroviruses are important viral causes of AGE but are relatively understudied enteric pathogens. Recent developments in novel biomimetic human models of enteric disease are opening new possibilities for studying human-specific host-microbe interactions. Human intestinal enteroids (HIE), which are epithelium-only intestinal organoids derived from stem cells isolated from human intestinal biopsy tissues, have been successfully used to culture representative norovirus, rotavirus, and astrovirus strains. Previous studies investigated host-virus interactions at the intestinal epithelial interface by individually profiling the epithelial transcriptional response to a member of each virus family by RNA sequencing (RNA-seq). Despite differences in the tissue origin, enteric virus used, and hours post infection at which RNA was collected in each data set, the uniform analysis of publicly available datasets identified a conserved epithelial response to virus infection focused around "type I interferon production" and interferon-stimulated genes. Additionally, transcriptional changes specific to only one or two of the enteric viruses were also identified. This study can guide future explorations into common and unique aspects of the host response to virus infections in the human intestinal epithelium and demonstrates the promise of comparative RNA-seq analysis, even if performed under different experimental conditions, to discover universal and virus-specific genes and pathways responsible for antiviral host defense.

The airway epithelium during infancy and childhood: A complex multicellular immune barrier. Basic review for clinicians

The airway epithelium is a complex multicellular layer that extends from the nasopharynx to the small airways. It functions as an immune respiratory barrier during early life that develops, matures, and regenerates to adapt to the changes in the environment. While airway epithelial abnormalities have been identified in several clinical disorders, there is increasing interest in understanding its basic regulation and structure in humans. Indeed, recent advances in technology (e.g. single-cell analysis and new human airway epithelial cell models) have allowed us to identify additional cellular subtypes and functions that overall have greatly improved our understanding of the airway epithelium during health and disease. In this review we summarize key features of the airway epithelium including: 1) multilayer structure and cell heterogeneity; 2) adaptability to different environmental and developmental stimuli; 3) innate recognition; and 4) orchestration of immune responses. We discuss these features with a translational and clinical prospective focusing on the development of human respiratory immunity, particularly during early life.

Influenza Virus RNA Synthesis and the Innate Immune Response

Infection with influenza A and B viruses results in a mild to severe respiratory tract infection. It is widely accepted that many factors affect the severity of influenza disease, including viral replication, host adaptation, innate immune signalling, pre-existing immunity, and secondary infections. In this review, we will focus on the interplay between influenza virus RNA synthesis and the detection of influenza virus RNA by our innate immune system. Specifically, we will discuss the generation of various RNA species, host pathogen receptors, and host shut-off. In addition, we will also address outstanding questions that currently limit our knowledge of influenza virus replication and host adaption. Understanding the molecular mechanisms underlying these factors is essential for assessing the pandemic potential of future influenza virus outbreaks.

A truncated intracellular Dicer-like molecule involves in antiviral immune recognition of oyster Crassostrea gigas

The enzyme Dicer is best known for its role as an endoribonuclease in the small RNA pathway, playing a crucial role in recognizing viral double-stranded RNA (dsRNA) and inducing down-stream cascades to mediate anti-virus immunity. In the present study, a truncated Dicer-like gene was identified from oyster Crassostrea gigas, and its open reading frame (ORF) encoded a polypeptide (designed as CgDCL) of 530 amino acids. The CgDCL contained one N-terminal DEAD domain and a C-terminal helicase domain, but lack the conserved PAZ domain, ribonuclease domain (RIBOc) and dsRNA binding domain. The mRNA transcripts of CgDCL were detected in all the examined tissues with high expression levels in lip, gills and haemocytes, which were 62.06-fold, 48.91-fold and 47.13-fold (p < 0.05) of that in mantle, respectively. In the primarily cultured oyster haemocytes, the mRNA transcripts of CgDCL were significantly induced at 12 h after poly(I:C) stimulation, which were 4.04-fold (p < 0.05) of that in control group. The expression level of CgDCL mRNA in haemocytes was up-regulated significantly after dsRNA and recombinant interferon-like protein (rCgIFNLP) injection, which was 12.87-fold (p < 0.01) and 3.22-fold (p < 0.05) of that in control group, respectively. CgDCL proteins were mainly distributed in the cytoplasm of haemocytes. The recombinant CgDCL protein displayed binding activity to dsRNA and poly(I:C), but no obvious dsRNA cleavage activity. These results collectively suggest that truncated CgDCL from C. gigas was able to be activated by poly(I:C), dsRNA and CgIFNLP, and functioned as an intracellular recognition molecule to bind nucleic acid of virus, indicating a potential mutual cooperation between RNAi and IFN-like system in anti-virus immunity of oysters.

Inhibition of innate immune response ameliorates Zika virus-induced neurogenesis deficit in human neural stem cells

Global Zika virus (ZIKV) outbreaks and their strong link to microcephaly have raised major public health concerns. ZIKV has been reported to affect the innate immune responses in neural stem/progenitor cells (NS/PCs). However, it is unclear how these immune factors affect neurogenesis. In this study, we used Asian-American lineage ZIKV strain PRVABC59 to infect primary human NS/PCs originally derived from fetal brains. We found that ZIKV overactivated key molecules in the innate immune pathways to impair neurogenesis in a cell stage-dependent manner. Inhibiting the overactivated innate immune responses ameliorated ZIKV-induced neurogenesis reduction. This study thus suggests that orchestrating the host innate immune responses in NS/PCs after ZIKV infection could be promising therapeutic approach to attenuate ZIKV-associated neuropathology.

Cell Surface Expression of Endosomal Toll-Like Receptors-A Necessity or a Superfluous Duplication?

Timely and precise delivery of the endosomal Toll-like receptors (TLRs) to the ligand recognition site is a critical event in mounting an effective antimicrobial immune response, however, the same TLRs should maintain the delicate balance of avoiding recognition of self-nucleic acids. Such sensing is widely known to start from endosomal compartments, but recently enough evidence has accumulated supporting the idea that TLR-mediated signaling pathways originating in the cell membrane may be engaged in various cells due to differential expression and distribution of the endosomal TLRs. Therefore, the presence of endosomal TLRs on the cell surface could benefit the host responses in certain cell types and/or organs. Although not fully understood why, TLR3, TLR7, and TLR9 may occur both in the cell membrane and intracellularly, and it seems that activation of the immune response can be initiated concurrently from these two sites in the cell. Furthermore, various forms of endosomal TLRs may be transported to the cell membrane, indicating that this may be a normal process orchestrated by cysteine proteases-cathepsins. Among the endosomal TLRs, TLR3 belongs to the evolutionary distinct group and engages a different protein adapter in the signaling cascade. The differently glycosylated forms of TLR3 are transported by UNC93B1 to the cell membrane, unlike TLR7, TLR8, and TLR9. The aim of this review is to reconcile various views on the cell surface positioning of endosomal TLRs and add perspective to the implication of such receptor localization on their function, with special attention to TLR3. Cell membrane-localized TLR3, TLR7, and TLR9 may contribute to endosomal TLR-mediated inflammatory signaling pathways. Dissecting this signaling axis may serve to better understand mechanisms influencing endosomal TLR-mediated inflammation, thus determine whether it is a necessity for immune response or simply a circumstantial superfluous duplication, with other consequences on immune response.

Extracellular vesicles promote transkingdom nutrient transfer during viral-bacterial co-infection

Extracellular vesicles (EVs) are increasingly appreciated as a mechanism of communication among cells that contribute to many physiological processes. Although EVs can promote either antiviral or proviral effects during viral infections, the role of EVs in virus-associated polymicrobial infections remains poorly defined. We report that EVs secreted from airway epithelial cells during respiratory viral infection promote secondary bacterial growth, including biofilm biogenesis, by Pseudomonas aeruginosa. Respiratory syncytial virus (RSV) increases the release of the host iron-binding protein transferrin on the extravesicular face of EVs, which interact with P. aeruginosa biofilms to transfer the nutrient iron and promote bacterial biofilm growth. Vesicular delivery of iron by transferrin more efficiently promotes P. aeruginosa biofilm growth than soluble holo-transferrin delivered alone. Our findings indicate that EVs are a nutrient source for secondary bacterial infections in the airways during viral infection and offer evidence of transkingdom communication in the setting of polymicrobial infections.