In Vitro Model of Fully Differentiated Human Nasal Epithelial Cells Infected With Rhinovirus Reveals Epithelium-Initiated Immune Responses

Pathogenesis, Diagnosis, and Treatment of Infectious Rhinosinusitis

Rhinosinusitis is a common inflammatory disease of the sinonasal mucosa and paranasal sinuses. The pathogenesis of rhinosinusitis involves a variety of factors, including genetics, nasal microbiota status, infection, and environmental influences. Pathogenic microorganisms, including viruses, bacteria, and fungi, have been proven to target the cilia and/or epithelial cells of ciliated airways, which results in the impairment of mucociliary clearance, leading to epithelial cell apoptosis and the loss of epithelial barrier integrity and immune dysregulation, thereby facilitating infection. However, the mechanisms employed by pathogenic microorganisms in rhinosinusitis remain unclear. Therefore, this review describes the types of common pathogenic microorganisms that cause rhinosinusitis, including human rhinovirus, respiratory syncytial virus, Staphylococcus aureus, Pseudomonas aeruginosa, Aspergillus species, etc. The damage of mucosal cilium clearance and epithelial barrier caused by surface proteins or secreted virulence factors are summarized in detail. In addition, the specific inflammatory response, mainly Type 1 immune responses (Th1) and Type 2 immune responses (Th2), induced by the entry of pathogens into the body is discussed. The conventional treatment of infectious sinusitis and emerging treatment methods including nanotechnology are also discussed in order to improve the current understanding of the types of microorganisms that cause rhinosinusitis and to help effectively select surgical and/or therapeutic interventions for precise and personalized treatment.

The Interplay between Airway Cilia and Coronavirus Infection, Implications for Prevention and Control of Airway Viral Infections

Coronaviruses (CoVs) are a class of respiratory viruses with the potential to cause severe respiratory diseases by infecting cells of the upper respiratory tract, bronchial epithelium, and lung. The airway cilia are distributed on the surface of respiratory epithelial cells, forming the first point of contact between the host and the inhaled coronaviruses. The function of the airway cilia is to oscillate and sense, thereby defending against and removing pathogens to maintain the cleanliness and patency of the respiratory tract. Following infection of the respiratory tract, coronaviruses exploit the cilia to invade and replicate in epithelial cells while also damaging the cilia to facilitate the spread and exacerbation of respiratory diseases. It is therefore imperative to investigate the interactions between coronaviruses and respiratory cilia, as well as to elucidate the functional mechanism of respiratory cilia following coronavirus invasion, in order to develop effective strategies for the prevention and treatment of respiratory viral infections. This review commences with an overview of the fundamental characteristics of airway cilia, and then, based on the interplay between airway cilia and coronavirus infection, we propose that ciliary protection and restoration may represent potential therapeutic approaches in emerging and re-emerging coronavirus pandemics.

Interferon signaling in the nasal epithelium distinguishes among lethal and common cold coronaviruses and mediates viral clearance

All respiratory viruses establish primary infections in the nasal epithelium, where efficient innate immune induction may prevent dissemination to the lower airway and thus minimize pathogenesis. Human coronaviruses (HCoVs) cause a range of pathologies, but the host and viral determinants of disease during common cold versus lethal HCoV infections are poorly understood. We model the initial site of infection using primary nasal epithelial cells cultured at an air-liquid interface (ALI). HCoV-229E, HCoV-NL63, and human rhinovirus-16 are common cold-associated viruses that exhibit unique features in this model: early induction of antiviral interferon (IFN) signaling, IFN-mediated viral clearance, and preferential replication at nasal airway temperature (33 °C) which confers muted host IFN responses. In contrast, lethal SARS-CoV-2 and MERS-CoV encode antagonist proteins that prevent IFN-mediated clearance in nasal cultures. Our study identifies features shared among common cold-associated viruses, highlighting nasal innate immune responses as predictive of infection outcomes and nasally directed IFNs as potential therapeutics.

Interferon signaling in the nasal epithelium distinguishes among lethal and common cold respiratory viruses and is critical for viral clearance

All respiratory viruses establish primary infections in the nasal epithelium, where efficient innate immune induction may prevent dissemination to the lower airway and thus minimize pathogenesis. Human coronaviruses (HCoVs) cause a range of pathologies, but the host and viral determinants of disease during common cold versus lethal HCoV infections are poorly understood. We model the initial site of infection using primary nasal epithelial cells cultured at air-liquid interface (ALI). HCoV-229E, HCoV-NL63 and human rhinovirus-16 are common cold-associated viruses that exhibit unique features in this model: early induction of antiviral interferon (IFN) signaling, IFN-mediated viral clearance, and preferential replication at nasal airway temperature (33°C) which confers muted host IFN responses. In contrast, lethal SARS-CoV-2 and MERS-CoV encode antagonist proteins that prevent IFN-mediated clearance in nasal cultures. Our study identifies features shared among common cold-associated viruses, highlighting nasal innate immune responses as predictive of infection outcomes and nasally-directed IFNs as potential therapeutics.

Poly I:C Pre-Treatment Induced the Anti-Viral Interferon Response in Airway Epithelial Cells

Type I and III interferons are among the most important antiviral mediators. Increased susceptibility to infections has been described as being associated with impaired interferon response in asthmatic patients. In this work, we focused on the modulation of interferon dysfunction after the rhinovirus infection of airway epithelial cells. Therefore, we tested polyinosinic:polycytidylic acid (poly I:C), a TLR3 agonist, as a possible preventive pre-treatment to improve this anti-viral response. In our human study on asthma, we found a deficiency in interferon levels in the nasal epithelial cells (NEC) from asthmatics at homeostatic level and after RV infection, which might contribute to frequent airway infection seen in asthmatic patients compared to healthy controls. Finally, pre-treatment with the immunomodulatory substance poly I:C before RV infection restored IFN responses in airway epithelial cells. Altogether, we consider poly I:C pre-treatment as a promising strategy for the induction of interferon response prior to viral infections. These results might help to improve current therapeutic strategies for allergic asthma exacerbations.

Early-immune development in asthma: A review of the literature

This review presents a comprehensive examination of the various factors contributing to the immunopathogenesis of asthma from the prenatal to preschool period. We focus on the contributions of genetic and environmental components as well as the role of the nasal and gut microbiome on immune development. Predisposing genetic factors, including inherited genes associated with increased susceptibility to asthma, are discussed alongside environmental factors such as respiratory viruses and pollutant exposure, which can trigger or exacerbate asthma symptoms. Furthermore, the intricate interplay between the nasal and gut microbiome and the immune system is explored, emphasizing their influence on allergic immune development and response to environmental stimuli. This body of literature underscores the necessity of a comprehensive approach to comprehend and manage asthma, as it emphasizes the interactions of multiple factors in immune development and disease progression.

Viral infections and chronic rhinosinusitis

Viral infections are the most common cause of upper respiratory infections; they frequently infect adults once or twice and children 6 to 8 times annually. In most cases, these infections are self-limiting and resolve. However, many patients with chronic rhinosinusitis (CRS) relay that their initiating event began with an upper respiratory infection that progressed in both symptom severity and duration. Viruses bind to sinonasal epithelia through specific receptors, thereby entering cells and replicating within them. Viral infections stimulate interferon-mediated innate immune responses. Recent studies suggest that viral infections may also induce type 2 immune responses and stimulate the aberrant production of cytokines that can result in loss of barrier function, which is a hallmark in CRS. The main purpose of this review will be to highlight common viruses and their associated binding receptors and highlight pathophysiologic mechanisms associated with alterations in mucociliary clearance, epithelial barrier function, and dysfunctional immune responses that might lead to a further understanding of the pathogenesis of CRS.

High-throughput bioprinting of the nasal epithelium using patient-derived nasal epithelial cells

Progenitor human nasal epithelial cells (hNECs) are an essential cell source for the reconstruction of the respiratory pseudostratified columnar epithelium composed of multiple cell types in the context of infection studies and disease modeling. Hitherto, manual seeding has been the dominant method for creating nasal epithelial tissue models through biofabrication. However, this approach has limitations in terms of achieving the intricate three-dimensional (3D) structure of the natural nasal epithelium. 3D bioprinting has been utilized to reconstruct various epithelial tissue models, such as cutaneous, intestinal, alveolar, and bronchial epithelium, but there has been no attempt to use of 3D bioprinting technologies for reconstruction of the nasal epithelium. In this study, for the first time, we demonstrate the reconstruction of the nasal epithelium with the use of primary hNECs deposited on Transwell inserts via droplet-based bioprinting (DBB), which enabled high-throughput fabrication of the nasal epithelium in Transwell inserts of 24-well plates. DBB of progenitor hNECs ranging from one-tenth to one-half of the cell seeding density employed during the conventional cell seeding approach enabled a high degree of differentiation with the presence of cilia and tight-junctions over a 4 weeks air-liquid interface culture. Single cell RNA sequencing of these cultures identified five major epithelial cells populations, including basal, suprabasal, goblet, club, and ciliated cells. These cultures recapitulated the pseudostratified columnar epithelial architecture present in the native nasal epithelium and were permissive to respiratory virus infection. These results denote the potential of 3D bioprinting for high-throughput fabrication of nasal epithelial tissue models not only for infection studies but also for other purposes, such as disease modeling, immunological studies, and drug screening.

Prolonged Primary Rhinovirus Infection of Human Nasal Epithelial Cells Diminishes the Viral Load of Secondary Influenza H3N2 Infection via the Antiviral State Mediated by RIG-I and Interferon-Stimulated Genes

Our previous study revealed that prolonged human rhinovirus (HRV) infection rapidly induces antiviral interferons (IFNs) and chemokines during the acute stage of infection. It also showed that expression levels of RIG-I and interferon-stimulated genes (ISGs) were sustained in tandem with the persistent expression of HRV RNA and HRV proteins at the late stage of the 14-day infection period. Some studies have explored the protective effects of initial acute HRV infection on secondary influenza A virus (IAV) infection. However, the susceptibility of human nasal epithelial cells (hNECs) to re-infection by the same HRV serotype, and to secondary IAV infection following prolonged primary HRV infection, has not been studied in detail. Therefore, the aim of this study was to investigate the effects and underlying mechanisms of HRV persistence on the susceptibility of hNECs against HRV re-infection and secondary IAV infection. We analyzed the viral replication and innate immune responses of hNECs infected with the same HRV serotype A16 and IAV H3N2 at 14 days after initial HRV-A16 infection. Prolonged primary HRV infection significantly diminished the IAV load of secondary H3N2 infection, but not the HRV load of HRV-A16 re-infection. The reduced IAV load of secondary H3N2 infection may be explained by increased baseline expression levels of RIG-I and ISGs, specifically MX1 and IFITM1, which are induced by prolonged primary HRV infection. As is congruent with this finding, in those cells that received early and multi-dose pre-treatment with Rupintrivir (HRV 3C protease inhibitor) prior to secondary IAV infection, the reduction in IAV load was abolished compared to the group without pre-treatment with Rupintrivir. In conclusion, the antiviral state induced from prolonged primary HRV infection mediated by RIG-I and ISGs (including MX1 and IFITM1) can confer a protective innate immune defense mechanism against secondary influenza infection.

High-Throughput Bioprinting of the Nasal Epithelium using Patient-derived Nasal Epithelial Cells

Human nasal epithelial cells (hNECs) are an essential cell source for the reconstruction of the respiratory pseudostratified columnar epithelium composed of multiple cell types in the context of infection studies and disease modeling. Hitherto, manual seeding has been the dominant method for creating nasal epithelial tissue models. However, the manual approach is slow, low-throughput and has limitations in terms of achieving the intricate 3D structure of the natural nasal epithelium in a uniform manner. 3D Bioprinting has been utilized to reconstruct various epithelial tissue models, such as cutaneous, intestinal, alveolar, and bronchial epithelium, but there has been no attempt to use of 3D bioprinting technologies for reconstruction of the nasal epithelium. In this study, for the first time, we demonstrate the reconstruction of the nasal epithelium with the use of primary hNECs deposited on Transwell inserts via droplet-based bioprinting (DBB), which enabled high-throughput fabrication of the nasal epithelium in Transwell inserts of 24-well plates. DBB of nasal progenitor cells ranging from one-tenth to one-half of the cell seeding density employed during the conventional cell seeding approach enabled a high degree of differentiation with the presence of cilia and tight-junctions over a 4-week air-liquid interface culture. Single cell RNA sequencing of these cultures identified five major epithelial cells populations, including basal, suprabasal, goblet, club, and ciliated cells. These cultures recapitulated the pseudostratified columnar epithelial architecture present in the native nasal epithelium and were permissive to respiratory virus infection. These results denote the potential of 3D bioprinting for high-throughput fabrication of nasal epithelial tissue models not only for infection studies but also for other purposes such as disease modeling, immunological studies, and drug screening.

SARS-CoV-2 replication in airway epithelia requires motile cilia and microvillar reprogramming

How SARS-CoV-2 penetrates the airway barrier of mucus and periciliary mucins to infect nasal epithelium remains unclear. Using primary nasal epithelial organoid cultures, we found that the virus attaches to motile cilia via the ACE2 receptor. SARS-CoV-2 traverses the mucus layer, using motile cilia as tracks to access the cell body. Depleting cilia blocks infection for SARS-CoV-2 and other respiratory viruses. SARS-CoV-2 progeny attach to airway microvilli 24 h post-infection and trigger formation of apically extended and highly branched microvilli that organize viral egress from the microvilli back into the mucus layer, supporting a model of virus dispersion throughout airway tissue via mucociliary transport. Phosphoproteomics and kinase inhibition reveal that microvillar remodeling is regulated by p21-activated kinases (PAK). Importantly, Omicron variants bind with higher affinity to motile cilia and show accelerated viral entry. Our work suggests that motile cilia, microvilli, and mucociliary-dependent mucus flow are critical for efficient virus replication in nasal epithelia.

Rhinovirus Suppresses TGF-β-GARP Presentation by Peripheral NK Cells

Asthma is a chronic airway disease whose exacerbations are often triggered by rhinovirus infection. TGF-β1 induces rhinovirus replication in infected cells. Moreover, TGF-β1 is a pleiotropic mediator that is produced by many immune cells in the latent, inactive form bound to the latency-associated peptide (LAP) and to the transmembrane protein glycoprotein A repetitions predominant (GARP). In this study we wanted to investigate the effect of rhinovirus infection on the TGF-β secretion and the downstream signaling via TGF-βRI/RII in peripheral blood mononuclear cells from control and asthmatic patients after rhinovirus infection ex vivo. Here, we found a significant upregulation of TGF-βRII in untouched PBMCs of asthmatics as well as a suppression of TGF-β release in the rhinovirus-infected PBMC condition. Moreover, consistent with an effect of TGF-β on Tregs, PBMCs infected with RV induced Tregs, and TGF-βRII directly correlated with RV1b mRNA. Finally, we found via flow cytometry that NK cells expressed less GARP surface-bound TGF-β, while cytokine-producing NKbright cells were induced. In summary, we show that rhinovirus infection inhibits TGF-β release in PBMCs, which results in the activation of both Treg and NK cells.

The Role of Viruses in the Inception of Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) is a complex inflammatory disorder that affects between 2% and 16% of adults in the United States, with estimated healthcare costs between 4 and 12 million USD. Viruses are a common etiologic factor for URIs, are frequently identified in the sinuses of patients with CRS, and trigger CRS exacerbations. Therefore, investigating the role of viruses provides an opportunity to identify their role in the pathogenesis of CRS. In this review, we identified the viruses frequently isolated in patients with CRS, as well as their associated immunologic responses and contributions to inflammation. Rhinovirus, parainfluenza virus, influenza virus, and respiratory syncytial virus are the viruses commonly found in patients with CRS. This information allows us to target pathways early in the pathogenesis of CRS, thereby playing a significant role in slowing the progression of this chronic disease.

Transcriptomics of rhinovirus persistence reveals sustained expression of RIG-I and interferon-stimulated genes in nasal epithelial cells in vitro

BACKGROUND

Human rhinoviruses (HRVs) are frequently associated with asthma exacerbations, and have been found in the airways of asthmatic patients. While HRV-induced acute infection is well-documented, it is less clear whether the nasal epithelium sustains prolonged HRV infections along with the associated activation of host immune responses.

OBJECTIVE

To investigate sustainably regulated host responses of human nasal epithelial cells (hNECs) during HRV persistence.

METHODS

Using a time-course study, HRV16 persistence and viral replication dynamics were established using an in vitro infection model of hNECs. RNA sequencing was performed on hNECs in the early and late stages of infection at 3 and 14 days post-infection (dpi), respectively. The functional enrichment of differentially expressed genes (DEGs) was evaluated using gene ontology (GO) and Ingenuity pathway analysis.

RESULTS

HRV RNA and protein expression persisted throughout prolonged infections, even after decreased production of infectious virus progeny. GO analysis of unique DEGs indicated altered regulation of pathways related to ciliary function and airway remodeling at 3 dpi and serine-type endopeptidase activity at 14 dpi. The functional enrichment of shared DEGs between the two time-points was related to interferon (IFN) and cytoplasmic pattern recognition receptor (PRR) signaling pathways. Validation of the sustained regulation of candidate genes confirmed the persistent expression of RIG-I and revealed its close co-regulation with interferon-stimulated genes (ISGs) during HRV persistence.

CONCLUSIONS

The persistence of HRV RNA does not necessarily indicate an active infection during prolonged infection. The sustained expression of RIG-I and ISGs in response to viral RNA persistence highlights the importance of assessing how immune-activating host factors can change during active HRV infection and the immune regulation that persists thereafter.

Innate Immune Responses by Respiratory Viruses, Including Rhinovirus, During Asthma Exacerbation

Viral infection, especially with rhinovirus (RV), is a major cause of asthma exacerbation. The production of anti-viral cytokines such as interferon (IFN)-β and IFN-α from epithelial cells or dendritic cells is lower in patients with asthma or those with high IgE, which can contribute to viral-induced exacerbated disease in these patients. As for virus-related factors, RV species C (RV-C) induces more exacerbated disease than other RVs, including RV-B. Neutrophils activated by viral infection can induce eosinophilic airway inflammation through different mechanisms. Furthermore, virus-induced or virus-related proteins can directly activate eosinophils. For example, CXCL10, which is upregulated during viral infection, activates eosinophils in vitro. The role of innate immune responses, especially type-2 innate lymphoid cells (ILC2) and epithelial cell-related cytokines including IL-33, IL-25, and thymic stromal lymphopoietin (TSLP), in the development of viral-induced airway inflammation has recently been established. For example, RV infection induces the expression of IL-33 or IL-25, or increases the ratio of ILC2 in the asthmatic airway, which is correlated with the severity of exacerbation. A mouse model has further demonstrated that virus-induced mucous metaplasia and ILC2 expansion are suppressed by antagonizing or deleting IL-33, IL-25, or TSLP. For treatment, IFNs including IFN-β suppress not only viral replication but also ILC2 activation in vitro. Agonists of toll-like receptor (TLR) 3 or 7 can induce IFNs, which can then suppress viral replication and ILC2 activation. Therefore, if delivered in the airway, IFNs or TLR agonists could become innovative treatments for virus-induced asthma exacerbation.

H1N1 Influenza Virus-Infected Nasal Mucosal Epithelial Progenitor Cells Promote Dendritic Cell Recruitment and Maturation

The barrier function of nasal mucosal epithelial cells plays an irreplaceable role in the spread and expansion of viruses in the body. This study found that influenza A virus H1N1 could induce apoptosis of nasal mucosal epithelial progenitor cells, cause an inflammatory response, and trigger the maturation and recruitment of nasal submucosal dendritic cells (DCs), but the mechanism remained unclear. Therefore, we used RNA sequencing and high-resolution untargeted metabolomics to sequence and perform combined bioinformatic analysis of H1N1 virus-infected nasal mucosal epithelial cells from 6 different patients. The abnormal arginine metabolism signaling pathway caused by H1N1 virus infection was screened out, and arginase inhibitors were used to interfere with the abnormal arginine metabolism and the maturation and recruitment of submucosal DCs caused by the H1N1 virus in vitro and in vivo. We conclude that H1N1 influenza virus promotes the recruitment and maturation of submucosal DCs by causing abnormal arginine metabolism in nasal mucosal epithelial cells, thereby triggering respiratory mucosal immunity.

Human Nasal Epithelial Cells (hNECs ) Generated by Air-Liquid Interface (ALI) Culture as a Model System for Studying the Pathogenesis of SARS-CoV-2

The nasal epithelium lining the human upper airway is the primary portal of entry for several respiratory pathogens, including the recently emerged SARS-CoV-2 virus responsible for the ongoing COVID-19 pandemic. Here, we describe in detail methods for in vitro ALI differentiation of primary cells collected from human donors, to obtain differentiated hNECs. This can serve as a physiologically relevant model to investigate various aspects of host-pathogen responses to SARS-CoV-2 and other emerging respiratory viruses.

The Expression of ephrinA1/ephA2 Receptor Increases in Chronic Rhinosinusitis and ephrinA1/ephA2 Signaling Affects Rhinovirus-Induced Innate Immunity in Human Sinonasal Epithelial Cells

EphA2 receptor and its ephrin ligands are involved in virus infection, epithelial permeability, and chemokine secretion. We hypothesized that ephrinA1/ephA2 signaling participates in rhinovirus (RV)-induced antiviral immune response in sinonasal mucosa of patients with chronic rhinosinusitis (CRS). Therefore, we investigated the expression of ephrinA1/ephA2 in normal and inflamed sinonasal mucosa and evaluated whether they regulate chemokine secretion and the production of antiviral immune mediators including interferons (IFNs) in RV-infected human primary sinonasal epithelial cells. For this purpose, the expression and distribution of ephrinA1/ephA2 in sinonasal mucosa were evaluated with RT-qPCR, immunofluorescence, and western blot. Their roles in chemokine secretion and the production of antiviral immune mediators such as type I and III IFNs, and interferon stimulated genes were evaluated by stimulating ephA2 with ephrinA1 and inactivating ephA2 with ephA2 siRNA or inhibitor in cells exposed to RV and poly(I:C). We found that ephrinA1/ephA2 were expressed in normal mucosa and their levels increased in inflamed sinonasal mucosa of CRS patients. RV infection or poly(I:C) treatment induced chemokine secretion which were attenuated by blocking the action of ephA2 with ephA2 siRNA or inhibitor. The production of antiviral immune mediators enhanced by rhinovirus or poly (I:C) is increased by blocking ephA2 compared with that of cells stimulated by either rhinovirus or poly(I:C) alone. In addition, blocking ephA2 attenuated RV replication in cultured cells. Taken together, these results describe a novel role of ephrinA1/ephA2 signaling in antiviral innate immune response in sinonasal epithelium, suggesting their participation in RV-induced development and exacerbations of CRS.

Mechanism of Rhinovirus Immunity and Asthma

The majority of asthma exacerbations in children are caused by Rhinovirus (RV), a positive sense single stranded RNA virus of the Picornavirus family. The host has developed virus defense mechanisms that are mediated by the upregulation of interferon-activated signaling. However, the virus evades the immune system by inducing immunosuppressive cytokines and surface molecules like programmed cell death protein 1 (PD-1) and its ligand (PD-L1) on immunocompetent cells. Initially, RV infects epithelial cells, which constitute a physiologic mucosal barrier. Upon virus entrance, the host cell immediately recognizes viral components like dsRNA, ssRNA, viral glycoproteins or CpG-DNA by host pattern recognition receptors (PRRs). Activation of toll like receptors (TLR) 3, 7 and 8 within the endosome and through MDA-5 and RIG-I in the cytosol leads to the production of interferon (IFN) type I and other antiviral agents. Every cell type expresses IFNAR1/IFNAR2 receptors thus allowing a generalized antiviral activity of IFN type I resulting in the inhibition of viral replication in infected cells and preventing viral spread to non-infected cells. Among immune evasion mechanisms of the virus, there is downregulation of IFN type I and its receptor as well as induction of the immunosuppressive cytokine TGF-β. TGF-β promotes viral replication and is associated with induction of the immunosuppression signature markers LAP3, IDO and PD-L1. This article reviews the recent advances on the regulation of interferon type I expression in association with RV infection in asthmatics and the immunosuppression induced by the virus.

Induction of IL-25 Expression in Human Nasal Polyp Epithelium by Influenza Virus Infection is Abated by Interferon-Alpha Pretreatment

Background

Epithelial cytokines including IL-25, IL-33 and thymic stromal lymphopoietin (TLSP) are recently established as drivers of type 2 chronic inflammatory diseases such as chronic rhinosinusitis with nasal polyps (CRSwNP). Here, we further confirmed the increased expression of IL-25 in CRSwNP and investigated potential contributors of IL-25 in CRSwNP epithelium.

Methods

Sixty CRSwNP, 25 CRSsNP and 15 healthy control tissues were examined for IL-25 expression and for the accompanying type 2 inflammatory cytokines. We then tested different respiratory virus infections on human nasal epithelial cells (hNECs) for their ability to trigger IL-25 expression. In addition, we subjected hNECs generated from CRSwNP tissues to pretreatment with recombinant interferon-alpha (IFN-α) prior to viral infection to evaluate IFN effects on IL-25 induction.

Results

We confirmed that significantly enhanced levels of IL-25 were observed in CRSwNP tissues, and that IL-25 expression correlated with type 2 inflammatory cytokine expression. In vitro, we observed significantly elevated IL-25 in hNECs infected with influenza A virus as early as 24 hours post-infection (hpi), regardless of tissue origin, and IL-25 correlated positively with viral load. While other respiratory viruses exhibited increasing trends of IL-25, these were not significant at the time-points tested. IFN-α treatment of CRSwNP epithelium was found to exert bimodal effects, ie IFN-α treatment alone induced moderate IL-25 expression, whereas IFN-α pretreatment of hNECs before influenza infection significantly diminished IL-25 induction by active influenza virus infection.

Conclusion

We have authenticated the observation of elevated IL-25 in CRSwNP, which is correlated with type 2 inflammatory cytokines. Notably, we identified influenza virus infection as a potential contributor of IL-25 in both control and CRSwNP epithelium during active infection. This IL-25 induction can be abated by IFN-α pretreatment which ameliorated active influenza infection.

Trial Registration

Chictr.org.cn ChiCTR-BON-16010179, Registered 18 December 2016, http://www.chictr.org.cn/showproj.aspx?proj=17331. The authors agree on the sharing of deidentified participant data where it pertains to request directly related to the data in this article when contacted (Haiyu Hong; honghy@mail.sysu.edu.cn).

Remodeling of bronchial epithelium caused by asthmatic inflammation affects its response to rhinovirus infection

Human rhinoviruses (HRV) are frequent cause of asthma exacerbations, however the influence of airway inflammation on the severity of viral infection is poorly understood. Here, we investigated how cytokine-induced remodeling of airway epithelium modulates antiviral response. We analyzed gene expression response in in vitro differentiated bronchial epithelium exposed to cytokines and next infected with HRV16. IL-13-induced mucous cell metaplasia (MCM) was associated with impaired ciliogenesis and induction of antiviral genes, resulting in lower susceptibility to HRV. Epithelial-mesenchymal transition caused by TGF-β was associated with increased virus replication and boosted innate response. Moreover, HRV infection per se caused transient upregulation of MCM markers and growth factors, followed by low-level virus replication and shedding. Our data suggest that the outcome of HRV infection depends on the type of lower airway inflammation and the extent of epithelial damage. Type-2 inflammation (eosinophilic asthma) may induce antiviral state of epithelium and decrease virus sensitivity, while growth factor exposure during epithelial repair may facilitate virus replication and inflammatory response. Additionally, responses to HRV were similar in cells obtained from asthma patients and control subjects, which implicates that antiviral mechanisms are not intrinsically impaired in asthma, but may develop in the presence of uncontrolled airway inflammation.

International consensus statement on allergy and rhinology: rhinosinusitis 2021

I.

EXECUTIVE SUMMARY

BACKGROUND: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR-RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR-RS-2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence-based findings of the document.

METHODS

ICAR-RS presents over 180 topics in the forms of evidence-based reviews with recommendations (EBRRs), evidence-based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary.

RESULTS

ICAR-RS-2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence-based management algorithm is provided.

CONCLUSION

This ICAR-RS-2021 executive summary provides a compilation of the evidence-based recommendations for medical and surgical treatment of the most common forms of RS.

Glucocorticoids impair type I IFN signalling and enhance rhinovirus replication

Inhaled corticosteroids (ICS) are recommended treatments for all degrees of asthma severity and in combination with bronchodilators are indicated for COPD patients with a history of frequent exacerbations. However, the long-term side effects of glucocorticoids (GCs) may include increased risk of respiratory infections, including viral triggered exacerbations. Rhinovirus (RV) infection is the main trigger of asthma and COPD exacerbations. Thus, we sought to explore the influence of GCs on viral replication. We demonstrate the ICS fluticasone propionate (FP) and two selective non-steroidal (GRT7) and steroidal (GRT10) glucocorticoid receptor (GR) agonists significantly suppress pro-inflammatory (IL-6 and IL-8) and antiviral (IFN-λ1) cytokine production and the expression of the interferon-stimulated genes (ISGs) OAS and viperin in RV-infected bronchial epithelial cells, with a consequent increase of viral replication. We also show that FP, GRT7 and GRT10 inhibit STAT1 Y701 and/or STAT2 Y690 phosphorylation and ISG mRNA induction following cell stimulation with recombinant IFN-β. In addition, we investigated the effects of the ICS budesonide (BD) and the long-acting β2 agonist (LABA) formoterol, alone or as an ICS/LABA combination, on RV-induced ISG expression and viral replication. Combination of BD/formoterol increases the suppression of OAS and viperin mRNA observed with both BD and formoterol alone, but an increase in viral RNA was only observed with BD treatment and not with formoterol. Overall, we provide evidence of an impairment of the innate antiviral immune response by GC therapy and the potential for GCs to enhance viral replication. These findings could have important clinical implications.

Host Antiviral Response Suppresses Ciliogenesis and Motile Ciliary Functions in the Nasal Epithelium

Background

Respiratory viral infections are one of the main drivers of development and exacerbation for chronic airway inflammatory diseases. Increased viral susceptibility and impaired mucociliary clearance are often associated with chronic airway inflammatory diseases and served as risk factors of exacerbations. However, the links between viral susceptibility, viral clearance, and impaired mucociliary functions are unclear. Therefore, the objective of this study is to provide the insights into the effects of improper clearance of respiratory viruses from the epithelium following infection, and their resulting persistent activation of antiviral response, on mucociliary functions.

Methods

In order to investigate the effects of persistent antiviral responses triggered by viral components from improper clearance on cilia formation and function, we established an in vitro air–liquid interface (ALI) culture of human nasal epithelial cells (hNECs) and used Poly(I:C) as a surrogate of viral components to simulate their effects toward re-epithelization and mucociliary functions of the nasal epithelium following damages from a viral infection.

Results

Through previous and current viral infection expression data, we found that respiratory viral infection of hNECs downregulated motile cilia gene expression. We then further tested the effects of antiviral response activation on the differentiation of hNECs using Poly(I:C) stimulation on differentiating human nasal epithelial stem/progenitor cells (hNESPCs). Using this model, we observed reduced ciliated cell differentiation compared to goblet cells, reduced protein and mRNA in ciliogenesis-associated markers, and increased mis-assembly and mis-localization of ciliary protein DNAH5 following treatment with 25 μg/ml Poly(I:C) in differentiating hNECs. Additionally, the cilia length and ciliary beat frequency (CBF) were also decreased, which suggest impairment of ciliary function as well.

Conclusion

Our results suggest that the impairments of ciliogenesis and ciliary function in hNECs may be triggered by specific expression of host antiviral response genes during re-epithelization of the nasal epithelium following viral infection. This event may in turn drive the development and exacerbation of chronic airway inflammatory diseases.

Biomarkers for diagnosis and prediction of therapy responses in allergic diseases and asthma

Modern health care requires a proactive and individualized response to diseases, combining precision diagnosis and personalized treatment. Accordingly, the approach to patients with allergic diseases encompasses novel developments in the area of personalized medicine, disease phenotyping and endotyping, and the development and application of reliable biomarkers. A detailed clinical history and physical examination followed by the detection of IgE immunoreactivity against specific allergens still represents the state of the art. However, nowadays, further emphasis focuses on the optimization of diagnostic and therapeutic standards and a large number of studies have been investigating the biomarkers of allergic diseases, including asthma, atopic dermatitis, allergic rhinitis, food allergy, urticaria and anaphylaxis. Various biomarkers have been developed by omics technologies, some of which lead to a better classification of distinct phenotypes or endotypes. The introduction of biologicals to clinical practice increases the need for biomarkers for patient selection, prediction of outcomes and monitoring, to allow for an adequate choice of the duration of these costly and long‐lasting therapies. Escalating healthcare costs together with questions about the efficacy of the current management of allergic diseases require further development of a biomarker‐driven approach. Here, we review biomarkers in diagnosis and treatment of asthma, atopic dermatitis, allergic rhinitis, viral infections, chronic rhinosinusitis, food allergy, drug hypersensitivity and allergen immunotherapy with a special emphasis on specific IgE, the microbiome and the epithelial barrier. In addition, EAACI guidelines on biologicals are discussed within the perspective of biomarkers.

ACE2 localizes to the respiratory cilia and is not increased by ACE inhibitors or ARBs

The coronavirus SARS-CoV-2 is the causative agent of the ongoing severe acute respiratory disease pandemic COVID-19. Tissue and cellular tropism is one key to understanding the pathogenesis of SARS-CoV-2. We investigate the expression and subcellular localization of the SARS-CoV-2 receptor, angiotensin-converting enzyme 2 (ACE2), within the upper (nasal) and lower (pulmonary) respiratory tracts of human donors using a diverse panel of banked tissues. Here, we report our discovery that the ACE2 receptor protein robustly localizes within the motile cilia of airway epithelial cells, which likely represents the initial or early subcellular site of SARS-CoV-2 viral entry during host respiratory transmission. We further determine whether ciliary ACE2 expression in the upper airway is influenced by patient demographics, clinical characteristics, comorbidities, or medication use, and show the first mechanistic evidence that the use of angiotensin-converting enzyme inhibitors (ACEI) or angiotensin II receptor blockers (ARBs) does not increase susceptibility to SARS-CoV-2 infection through enhancing the expression of ciliary ACE2 receptor. These findings are crucial to our understanding of the transmission of SARS-CoV-2 for prevention and control of this virulent pathogen.

Interleukin-13 Alters Tight Junction Proteins Expression Thereby Compromising Barrier Function and Dampens Rhinovirus Induced Immune Responses in Nasal Epithelium

Tight junctions (TJs) are intercellular structures which are essential for epithelial barrier function and play an important role in antimicrobial defense. Epithelium dysfunction and type-2-skewed inflammation are two main pathological phenomena of chronic rhinosinusitis with nasal polyps (CRSwNP). However, the effect of pro-inflammatory type-2 cytokine IL-13 on TJs in CRSwNP is poorly understood. Nasal biopsies of CRSwNP patients and in vitro IL-13-matured human nasal epithelial cells (hNECs) were used to analyze epithelial markers and TJ proteins. Epithelium permeability, transepithelial electrical resistance (TEER), expression of TJs were quantified for IL-13-matured hNECs and that with RV infection. The expression of occludin, claudin-3, and ZO-1 were significantly decreased in CRSwNP biopsies and in hNECs after IL-13 treatment. IL-13 treatment increased epithelium permeability, decreased TEER and altered hNECs composition resulting in lesser ciliated cells and mucus over-secretion. Interestingly, claudin-3 is selectively expressed on ciliated cells. While RV infection induced minimal changes to TJs, the IL-13-matured hNECs has reduced capacity for upregulation of IFN-λ1 and CXCL10 but further increased the expression of TSLP upon RV infection. These findings suggested that IL-13-mediated dysfunction of TJs and compromised epithelial barrier. IL-13-induced cilia loss conferred lowered viral replication and impaired antiviral responses of nasal epithelium against RV infection.

Rhinovirus and Innate Immune Function of Airway Epithelium

Airway epithelial cells, which lines the respiratory mucosa is in direct contact with the environment. Airway epithelial cells are the primary target for rhinovirus and other inhaled pathogens. In response to rhinovirus infection, airway epithelial cells mount both pro-inflammatory responses and antiviral innate immune responses to clear the virus efficiently. Some of the antiviral responses include the expression of IFNs, endoplasmic reticulum stress induced unfolded protein response and autophagy. Airway epithelial cells also recruits other innate immune cells to establish antiviral state and resolve the inflammation in the lungs. In patients with chronic lung disease, these responses may be either defective or induced in excess leading to deficient clearing of virus and sustained inflammation. In this review, we will discuss the mechanisms underlying antiviral innate immunity and the dysregulation of some of these mechanisms in patients with chronic lung diseases.

Airway Epithelial Cell Immunity Is Delayed During Rhinovirus Infection in Asthma and COPD

Respiratory viral infections, particularly those caused by rhinovirus, exacerbate chronic respiratory inflammatory diseases, such as asthma and chronic obstructive pulmonary disease (COPD). Airway epithelial cells are the primary site of rhinovirus replication and responsible of initiating the host immune response to infection. Numerous studies have reported that the anti-viral innate immune response (including type I and type III interferon) in asthma is less effective or deficient leading to the conclusion that epithelial innate immunity is a key determinant of disease severity during a rhinovirus induced exacerbation. However, deficient rhinovirus-induced epithelial interferon production in asthma has not always been observed. We hypothesized that disparate in vitro airway epithelial infection models using high multiplicity of infection (MOI) and lacking genome-wide, time course analyses have obscured the role of epithelial innate anti-viral immunity in asthma and COPD. To address this, we developed a low MOI rhinovirus model of differentiated primary epithelial cells obtained from healthy, asthma and COPD donors. Using genome-wide gene expression following infection, we demonstrated that gene expression patterns are similar across patient groups, but that the kinetics of induction are delayed in cells obtained from asthma and COPD donors. Rhinovirus-induced innate immune responses were defined by interferons (type-I, II, and III), interferon response factors (IRF1, IRF3, and IRF7), TLR signaling and NF-κB and STAT1 activation. Induced gene expression was evident at 24 h and peaked at 48 h post-infection in cells from healthy subjects. In contrast, in cells from donors with asthma or COPD induction was maximal at or beyond 72–96 h post-infection. Thus, we propose that propensity for viral exacerbations of asthma and COPD relate to delayed (rather than deficient) expression of epithelial cell innate anti-viral immune genes which in turns leads to a delayed and ultimately more inflammatory host immune response.

Robust ACE2 protein expression localizes to the motile cilia of the respiratory tract epithelia and is not increased by ACE inhibitors or angiotensin receptor blockers

We investigated the expression and subcellular localization of the SARS-CoV-2 receptor, angiotensin-converting enzyme 2 (ACE2), within the upper (nasal) and lower (pulmonary) respiratory tracts of healthy human donors. We detected ACE2 protein expression within the cilia organelle of ciliated airway epithelial cells, which likely represents the initial or early subcellular site of SARS-CoV-2 viral entry during respiratory transmission. We further determined whether ACE2 expression in the cilia of upper respiratory cells was influenced by patient demographics, clinical characteristics, co-morbidities, or medication use, and found no evidence that the use of angiotensin-converting enzyme inhibitors (ACEI) or angiotensin II receptor blockers (ARBs) increases ACE2 protein expression.

Aberrant anti-viral response of natural killer cells in severe asthma

Rhinovirus infections are the main cause of asthma exacerbations. As natural killer (NK) cells are important actors of the antiviral innate response, we aimed at evaluating the functions of NK cells from severe asthma patients in response to rhinovirus-like molecules or rhinoviruses.Peripheral blood mononuclear cells from patients with severe asthma and healthy donors were stimulated with pathogen-like molecules or with the rhinoviruses (RV)-A9 and RV-2. NK cell activation, degranulation and interferon (IFN)-γ expression were analysed.NK cells from severe asthma patients were less cytotoxic than those from healthy donors in response to toll-like receptor (TLR)3, TLR7/8 or RV-A9 but not in response to RV-2 stimulation. Furthermore, when cultured with interleukin (IL)-12+IL-15, cytokines which are produced during viral infections, NK cells from patients with severe asthma were less cytotoxic and expressed less IFN-γ than NK cells from healthy donors. NK cells from severe asthmatics exhibited an exhausted phenotype, with an increased expression of the checkpoint molecule Tim-3.Together, our findings indicate that the activation of NK cells from patients with severe asthma may be insufficient during some but not all respiratory infections. The exhausted phenotype may participate in NK cell impairment and aggravation of viral-induced asthma exacerbation in these patients.

Respiratory Viral Infections in Exacerbation of Chronic Airway Inflammatory Diseases: Novel Mechanisms and Insights From the Upper Airway Epithelium

Respiratory virus infection is one of the major sources of exacerbation of chronic airway inflammatory diseases. These exacerbations are associated with high morbidity and even mortality worldwide. The current understanding on viral-induced exacerbations is that viral infection increases airway inflammation which aggravates disease symptoms. Recent advances in in vitro air-liquid interface 3D cultures, organoid cultures and the use of novel human and animal challenge models have evoked new understandings as to the mechanisms of viral exacerbations. In this review, we will focus on recent novel findings that elucidate how respiratory viral infections alter the epithelial barrier in the airways, the upper airway microbial environment, epigenetic modifications including miRNA modulation, and other changes in immune responses throughout the upper and lower airways. First, we reviewed the prevalence of different respiratory viral infections in causing exacerbations in chronic airway inflammatory diseases. Subsequently we also summarized how recent models have expanded our appreciation of the mechanisms of viral-induced exacerbations. Further we highlighted the importance of the virome within the airway microbiome environment and its impact on subsequent bacterial infection. This review consolidates the understanding of viral induced exacerbation in chronic airway inflammatory diseases and indicates pathways that may be targeted for more effective management of chronic inflammatory diseases.

CCR5 attenuates neutrophilic airway inflammation exacerbated by infection with rhinovirus

Human rhinovirus (hRV) is the most common cause of asthma exacerbation characterized by clinical and pathophysiological heterogeneity. Steroid-sensitive, Th2 type-eosinophilic asthma has been somewhat studied, but hRV-induced neutrophilic asthma exacerbation is poorly understood. Here, CCR5 was found to play a role in attenuating neutrophilic airway inflammation in hRV-induced asthma exacerbation using chicken ovalbumin (OVA)-based model. CCR5 deficiency resulted in exacerbated neutrophilic asthmatic responses in airways following hRV infection. CCR5-deficient mice showed enhanced mucus expression and altered expression of tight junction proteins in lung tissues. CCR5-deficient mice were also manifested with influx of CD45⁺CD11b⁺Siglec-F⁺Gr-1⁺ neutrophils, along with enhanced production of IL-17A, IFN-γ, IL-6, IL-1β cytokines in inflamed tissues. In contrast, CCR5-deficient mice elicited down-regulation of Th2-related cytokine proteins following hRV infection. More interestingly, the lack of CCR5 altered the equilibrium of CD4⁺FoxP3⁺ Tregs and IL-17⁺CD4⁺ Th17 in inflamed tissues. CCR5-deficient mice showed increased frequency and absolute number of IL-17-producing CD4⁺ Th17 cells in lung tissues compared to wild-type mice, whereas the reduced infiltration of CD4⁺FoxP3⁺ Treg cells was observed. CCR5 deficiency resulted in the skewed production of Th17 and Th1 cytokines in lymph nodes and lungs upon OVA stimulation. Likewise, CCR5-deficient mice showed enhanced expression of Th17-inducing cytokines (IL-1β, IL-6, and TNF-α) in lung tissues. These results imply that CCR5 deficiency facilitates Th17 airway inflammation during hRV-induced asthma exacerbation, along with suppressing Th2 responses. Furthermore, our results suggest that CCR5 attenuates hRV-induced neutrophilic airway inflammation through conserving the equilibrium of CD4⁺Foxp3⁺ Treg cells and IL-17⁺CD4⁺ Th17 cells in hRV-induced asthma exacerbation.

Future research trends in understanding the mechanisms underlying allergic diseases for improved patient care

The specialties of allergy and clinical immunology have entered the era of precision medicine with the stratification of diseases into distinct disease subsets, specific diagnoses, and targeted treatment options, including biologicals and small molecules. This article reviews recent developments in research and patient care and future trends in the discipline. The section on basic mechanisms of allergic diseases summarizes the current status and defines research needs in structural biology, type 2 inflammation, immune tolerance, neuroimmune mechanisms, role of the microbiome and diet, environmental factors, and respiratory viral infections. In the section on diagnostic challenges, clinical trials, precision medicine and immune monitoring of allergic diseases, asthma, allergic and nonallergic rhinitis, and new approaches to the diagnosis and treatment of drug hypersensitivity reactions are discussed in further detail. In the third section, unmet needs and future research areas for the treatment of allergic diseases are highlighted with topics on food allergy, biologics, small molecules, and novel therapeutic concepts in allergen‐specific immunotherapy for airway disease. Unknowns and future research needs are discussed at the end of each subsection.

Nasal epithelial cells to assess in vitro immune responses to respiratory virus infection in pregnant women with asthma

Respiratory virus-induced asthma exacerbations occur frequently during pregnancy and are associated with adverse outcomes for mother and child. Primary nasal epithelial cells (pNECs) provide a useful method to study immune responses in pregnancy. pNECs were obtained by nasal brushings from pregnant and non-pregnant women with and without asthma. pNECS were infected in vitro with major group Rhinovirus 43 (RV43) and seasonal influenza (H3N2). Following infection, pNECs showed measurable quantities of interferon (IFN)-λ, IL-1β, IL-8, IP-10 and MIP1-α. pNECs provide a safe and effective method for studying respiratory epithelial cell responses during pregnancy.

The Interplay between Host Immunity and Respiratory Viral Infection in Asthma Exacerbation

Asthma is one of the most common and chronic diseases characterized by multidimensional immune responses along with poor prognosis and severity. The heterogeneous nature of asthma may be attributed to a complex interplay between risk factors (either intrinsic or extrinsic) and specific pathogens such as respiratory viruses, and even bacteria. The intrinsic risk factors are highly correlated with asthma exacerbation in host, which may be mediated via genetic polymorphisms, enhanced airway epithelial lysis, apoptosis, and exaggerated viral replication in infected cells, resulting in reduced innate immune response and concomitant reduction of interferon (types I, II, and III) synthesis. The canonical features of allergic asthma include strong Th2-related inflammation, sensitivity to non-steroidal anti-inflammatory drugs (NSAIDs), eosinophilia, enhanced levels of Th2 cytokines, goblet cell hyperplasia, airway hyper-responsiveness, and airway remodeling. However, the NSAID-resistant non-Th2 asthma shows a characteristic neutrophilic influx, Th1/Th17 or even mixed (Th17-Th2) immune response and concurrent cytokine streams. Moreover, inhaled corticosteroid-resistant asthma may be associated with multifactorial innate and adaptive responses. In this review, we will discuss the findings of various in vivo and ex vivo models to establish the critical heterogenic asthmatic etiologies, host-pathogen relationships, humoral and cell-mediated immune responses, and subsequent mechanisms underlying asthma exacerbation triggered by respiratory viral infections.

RNA Sequencing of H3N2 Influenza Virus-Infected Human Nasal Epithelial Cells from Multiple Subjects Reveals Molecular Pathways Associated with Tissue Injury and Complications

The human nasal epithelium is the primary site of exposure to influenza virus, the initiator of host responses to influenza and the resultant pathologies. Influenza virus may cause serious respiratory infection resulting in major complications, as well as severe impairment of the airways. Here, we elucidated the global transcriptomic changes during H3N2 infection of human nasal epithelial cells from multiple individuals. Using RNA sequencing, we characterized the differentially-expressed genes and pathways associated with changes occurring at the nasal epithelium following infection. We used in vitro differentiated human nasal epithelial cell culture model derived from seven different donors who had no concurrent history of viral infections. Statistical analysis highlighted strong transcriptomic signatures significantly associated with 24 and 48 h after infection, but not at the earlier 8-h time point. In particular, we found that the influenza infection induced in the nasal epithelium early and altered responses in interferon gamma signaling, B-cell signaling, apoptosis, necrosis, smooth muscle proliferation, and metabolic alterations. These molecular events initiated at the infected nasal epithelium may potentially adversely impact the airway, and thus the genes we identified could serve as potential diagnostic biomarkers or therapeutic targets for influenza infection and associated disease management.

Respiratory epithelial cells as master communicators during viral infections

PURPOSE OF REVIEW

Communication by epithelial cells during respiratory viral infections is critical in orchestrating effective anti-viral responses but also can lead to excessive inflammation. This review will evaluate studies that investigate how respiratory epithelial cells influence the behavior of immune cells and how epithelial cell/immune cell interactions contribute to antiviral responses and immunopathology outcomes.

RECENT FINDINGS

Previous studies have characterized cytokine responses of virus-infected epithelial cells. More recent studies have carefully demonstrated the effects of these cytokines on cellular behaviors within the infected lung. Infected epithelial cells release exosomes that specifically regulate responses of monocytes and neighboring epithelial cells without promoting spread of virus. In contrast, rhinovirus-infected cells induce monocytes to upregulate expression of the viral receptor, promoting spread of the virus to alternate cell types. The precise alteration of PDL expression on infected epithelial cells has been shown to switch between inhibition and activation of antiviral responses.

SUMMARY

These studies have more precisely defined the interactions between epithelial and immune cells during viral infections. This level of understanding is critical for the development of novel therapeutic strategies that promote effective antiviral responses or epithelial repair, or inhibit damaging inflammatory responses during severe respiratory viral infections.

A Co-culture Model of PBMC and Stem Cell Derived Human Nasal Epithelium Reveals Rapid Activation of NK and Innate T Cells Upon Influenza A Virus Infection of the Nasal Epithelium

Background: We established an in vitro co-culture model involving H3N2-infection of human nasal epithelium with peripheral blood mononuclear cells (PBMC) to investigate their cross-talk during early H3N2 infection. Methods: Nasal epithelium was differentiated from human nasal epithelial stem/progenitor cells and cultured wtih fresh human PBMC. PBMC and supernatants were harvested after 24 and 48 h of co-culture with H3N2-infected nasal epithelium. We used flow cytometry and Luminex to characterize PBMC subpopulations, their activation and secretion of cytokine and chemokines. Results: H3N2 infection of the nasal epithelium associated with significant increase in interferons (IFN-α, IFN-γ, IL-29), pro-inflammatory cytokines (TNF-α, BDNF, IL-3) and viral-associated chemokines (IP-10, MCP-3, I-TAC, MIG), detectable already after 24 h. This translates into rapid activation of monocytes, NK-cells and innate T-cells (MAIT and γδ T cells), evident with CD38+ and/or CD69+ upregulation. Conclusions: This system may contribute to in vitro mechanistic immunological studies bridging systemic models and possibly enable the development of targeted immunomodulatory therapies.

Involvement and Possible Role of Eosinophils in Asthma Exacerbation

Eosinophils are involved in the development of asthma exacerbation. Recent studies have suggested that sputum and blood eosinophil counts are important factors for predicting asthma exacerbation. In severe eosinophilic asthma, anti-interleukin (IL)-5 monoclonal antibody decreases blood eosinophil count and asthma exacerbation frequency. However, even in the absence of IL-5, eosinophilic airway inflammation can be sufficiently maintained by the T helper (Th) 2 network, which comprises a cascade of vascular cell adhesion molecule-1/CC chemokines/eosinophil growth factors, including granulocyte-macrophage colony-stimulating factor (GM-CSF). Periostin, an extracellular matrix protein and a biomarker of the Th2 immune response in asthma, directly activates eosinophils in vitro. A major cause of asthma exacerbation is viral infection, especially rhinovirus (RV) infection. The expression of intercellular adhesion molecule (ICAM)-1, a cellular receptor for the majority of RVs, on epithelial cells is increased after RV infection, and adhesion of eosinophils to ICAM-1 can upregulate the functions of eosinophils. The expressions of cysteinyl leukotrienes (cysLTs) and CXCL10 are upregulated in virus-induced asthma. CysLTs can directly provoke eosinophilic infiltration in vivo and activate eosinophils in vitro. Furthermore, eosinophils express the CXC chemokine receptor 3, and CXCL10 activates eosinophils in vitro. Both eosinophils and neutrophils contribute to the development of severe asthma or asthma exacerbation. IL-8, which is an important chemoattractant for neutrophils, is upregulated in some cases of severe asthma. Lipopolysaccharide (LPS), which induces IL-8 from epithelial cells, is also increased in the lower airways of corticosteroid-resistant asthma. IL-8 or LPS-stimulated neutrophils increase the transbasement membrane migration of eosinophils, even in the absence of chemoattractants for eosinophils. Therefore, eosinophils are likely to contribute to the development of asthma exacerbation through several mechanisms, including activation by Th2 cytokines, such as IL-5 or GM-CSF or by virus infection-related proteins, such as CXCL10, and interaction with other cells, such as neutrophils.

Motile Ciliary Disorders in Chronic Airway Inflammatory Diseases: Critical Target for Interventions

PURPOSE OF REVIEW

Impaired mucociliary clearance has been implicated in chronic upper and lower airway inflammatory diseases (i.e., allergic and non-allergic rhinitis, chronic rhinosinusitis with or without nasal polyps and asthma). How motile ciliary disorders (impaired ciliogenesis, ciliary beating and ultrastructural defects) are implicated in chronic airway inflammatory diseases is not fully understood. Elaboration of the role of motile ciliary disorders may serve as therapeutic targets for improving mucociliary clearance, thereby complementing contemporary disease management.

RECENT FINDINGS

We have summarized the manifestations of motile ciliary disorders and addressed the underlying associations with chronic airway inflammatory diseases. A panel of established and novel diagnostic tests and therapeutic interventions are outlined. Physicians should be vigilant in screening for motile ciliary disorders, particularly in patients with co-existing upper and lower airway inflammatory diseases. Proper assessment and treatment of motile ciliary disorders may have added value to the management and prevention of chronic airway inflammatory diseases.