Eosinophil-mediated suppression and Anti-IL-5 enhancement of plasmacytoid dendritic cell interferon responses in asthma

Dysregulation of airway and systemic interferon responses promotes asthma exacerbations in urban children

BACKGROUND

Determining why some upper respiratory illnesses provoke asthma exacerbations remains an unmet need.

OBJECTIVE

We sought to identify transcriptome-wide gene expression changes associated with colds that progress to exacerbation.

METHODS

Two hundred eight urban children (6-17 years) with exacerbation-prone asthma were prospectively monitored for up to 2 cold illnesses. Exacerbation illnesses (Ex+), defined as colds leading to asthma exacerbations requiring systemic corticosteroids within 10 days, were compared to colds that resolved without exacerbation (Ex-). Peripheral blood and nasal lavage samples were collected at baseline and during colds for RNA sequencing. Interferon gene expression was compared between Ex+ and Ex- illnesses. Generalized additive modeling revealed interferon response kinetics. Multiple linear regression models compared interferon expression to clinical variables.

RESULTS

One hundred six participants were evaluated during 154 colds. There was greater upregulation of differentially expressed interferon genes during Ex+ illnesses compared to Ex-. Ex+ illnesses had greater average and steeper rise in interferon expression. Within 3 days of illness, interferon expression was positively associated with nasal rhinovirus quantity (nasal: adjusted R2 = 0.48, P = .015; blood: adjusted R2 = 0.22, P = .013), and interferon expression was negatively associated with percentage predicted forced expiratory volume in 1 second (nasal: β = -0.010, P = .048; blood: β = -0.008, P = .023). Participants with lower baseline interferon expression had shorter time to exacerbation, higher risk for exacerbation with viral illnesses, and greater increase in interferon expression during viral colds (nasal: β = -0.80, P < .0001; blood: β = -0.75, P < .0001).

CONCLUSION

Dysregulated interferon responses are important contributors to asthma exacerbation risk in children. Low baseline interferon expression followed by greater upregulation of interferon pathways in airway and blood during respiratory illnesses increased exacerbation risk. Targeting this pathway in at-risk individuals holds promise for the personalized prevention of asthma exacerbations.

Unveiling the prevalence and impact of silent rhinovirus infection in chronic rhinosinusitis with nasal polyps

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNPs) involves persistent sinus inflammation, with emerging evidence suggesting a potential role of rhinovirus (RV) in its pathophysiology. However, whether RV exists in nasal tissues and affects the nasal mucosa after the resolution of infection symptoms remains unknown.

OBJECTIVE

To investigate the prevalence and impact of silent RV infection in nasal tissues.

METHODS

RV loads were detected in the nasal tissues of 47 controls and 101 patients with CRSwNP without respiratory infection. Participants were categorized into RV-positive (+), RV-negative (-), and the "gray zone" groups. Quantitative polymerase chain reaction, Western blotting, and immunofluorescence assays were used to analyze the impact of silent RV infection on the immune status of nasal tissues.

RESULTS

Silent RV infection was prevalent in both control (34%) and CRSwNP (30.7%) tissues, with higher viral loads observed in the nasal polyps. In controls, it was associated with high expression of types 1 and 2 interferon (IFN), type 2 inflammation, interleukin (IL)-17A, and IL-10. In patients with CRSwNP, silent RV infection was associated with lower levels of type 1 IFN, IL-17A, type 2 inflammation, and IL-10 but higher levels of type 2 IFN compared with those without RV infection. Meanwhile, RV (+) nasal polyps exhibited fewer tissue eosinophils and neutrophils than RV (-) nasal polyps.

CONCLUSION

Silent RV infection was prevalent in the nasal tissues, with a higher viral load detected in the nasal polyps. This silent RV infection is associated with distinct immune responses in healthy controls and patients with CRSwNP, involving differential modulation of IFNs, TH2 cytokines, IL-17A, IL-10, and eosinophil and neutrophil levels.

Antiviral roles of eosinophils in asthma and respiratory viral infection

Eosinophils are immune cells that are crucial for the pathogenesis of allergic diseases, such as asthma. These cells play multifunctional roles in various situations, including infection. They are activated during viral infections and exert antiviral activity. Pattern recognition receptors, toll-like receptor 7 and retinoic acid inducible gene-I, are important for the recognition and capture of RNA viruses. In addition, intracellular granule proteins (eosinophil cationic protein and eosinophil-derived neurotoxin) and intracellular nitric oxide production inactivate and/or degrade RNA viruses. Interestingly, eosinophil-synthesizing specialized pro-resolving mediators possess antiviral properties that inhibit viral replication. Thus, eosinophils may play a protective role during respiratory virus infections. Notably, antiviral activities are impaired in patients with asthma, and eosinophil activities are perturbed in proportion with the severity of asthma. The exact roles of eosinophils in RNA virus (rhinovirus, respiratory syncytial virus, and influenza virus)-induced type 2 inflammation-based asthma exacerbation remain unclear. Our research demonstrates that interferons (IFN-α and IFN-γ) stimulate human eosinophils to upregulate antiviral molecules, including guanylate-binding proteins and tripartite motifs. Furthermore, IFN-γ specifically increases the expression of IL5RA, ICAM-1, and FCGR1A, potentially enhancing cellular responsiveness to IL-5, ICAM-1-mediated adhesion to rhinoviruses, and IgG-induced inflammatory responses, respectively. In this review, we have summarized the relationship between viral infections and asthma and the mechanisms underlying the development of antiviral functions of human and mouse eosinophils in vivo and in vitro.

The new biologic drugs: Which children with asthma should get what?

Novel biologics (targeted antibody therapies) have revolutionized the management of severe childhood asthma. However, it is important that the right biologic is selected for the right patient, and understanding the evidence base for each biologic is crucial. Currently, four biologics (all monoclonal antibodies) are licensed in the UK for the treatment of children with severe asthma - omalizumab (Xolair), mepolizumab (Nucala), and dupilumab (Dupixent) in children aged 6 years and over; and tezepelumab (Tezspire), only in children aged 12 years and over. Tezepelumab is the only licensed biological that may be beneficial in severe asthma without evidence of Type 2 inflammation. All have a good safety profile but varying degrees of clinical efficacy in children, with wide variation in treatment responsiveness between individual patients. When selecting biologics for severe asthma, it is essential to remember the limitations of the current pediatric evidence. At present, there are no results from randomized, head-to-head trials of biologics in severe asthma. TREAT is an ongoing trial comparing omalizumab to mepolizumab and will be one of the first to provide such evidence. We must be especially aware of the dangers of extrapolating data from adults to children, because the pathophysiology and role of biomarkers may differ significantly from adult asthma. Given the current level of knowledge, even after treatment has been initiated, children should be regularly reviewed to determine the efficacy of treatment, side-effect profile and consideration of when treatment with the biologic should be discontinued.

Targeting the IL-5 pathway in eosinophilic asthma: A comparison of anti-IL-5 versus anti-IL-5 receptor agents

Eosinophilic asthma is characterized by frequent exacerbations, poor symptom control and accelerated lung function decline. It is now recognized that the immune response underlying eosinophilic asthma involves a complex network of interconnected pathways from both the adaptive and innate immune systems. Within this response, interleukin-5 (IL-5) plays a central role in eosinophil differentiation, activation and survival and has emerged as a key target for therapies treating severe asthma. The monoclonal antibodies mepolizumab and reslizumab target the ligand IL-5, preventing its interaction with eosinophils; in contrast, benralizumab binds to the IL-5 receptor (IL-5R), preventing IL-5 from binding and leading to substantially greater eosinophil reduction by enhanced antibody-dependent cell-mediated cytotoxicity. Although no direct head-to-head clinical trials of asthma have been published to formally evaluate the clinical significance of these different therapeutic approaches, the potential benefits of partial versus complete eosinophil depletion continue to remain an important area of study and debate. Here, we review the existing real-world and clinical study data of anti-IL-5/anti-IL-5R therapies in severe eosinophilic asthma.

Therapeutic relevance of eosinophilic inflammation and airway viral interactions in severe asthma

The role of eosinophils in airway inflammation and asthma pathogenesis is well established, with raised eosinophil counts in blood and sputum associated with increased disease severity and risk of asthma exacerbation. Conversely, there is also preliminary evidence suggesting antiviral properties of eosinophils in the airways. These dual roles for eosinophils are particularly pertinent as respiratory virus infections contribute to asthma exacerbations. Biologic therapies targeting key molecules implicated in eosinophil-associated pathologies have been approved in patients with severe asthma and, therefore, the effects of depleting eosinophils in a clinical setting are of considerable interest. This review discusses the pathological and antiviral roles of eosinophils in asthma and exacerbations. We also highlight the significant reduction in asthma exacerbations seen with biologic therapies, even at the height of the respiratory virus season. Furthermore, we discuss the implications of these findings in relation to the role of eosinophils in inflammation and antiviral responses to respiratory virus infection in asthma.

Cord blood granulocyte levels are associated with severe bronchiolitis in the first year of life

Objectives

Bronchiolitis is a leading cause of infant hospitalisation in the first year of life, and it preferentially affects infants born to mothers with asthma. Here, we evaluate cord blood granulocytes in infants born to mothers with asthma participating in the Breathing for Life Trial (BLT), to investigate early life determinants of bronchiolitis hospitalisation within the first year of life.

Methods

Cord blood from 89 participants was collected into EDTA tubes and processed within 6 h of birth. Cells were stained in whole cord blood for eosinophils (CD45+, CD193+, CD16-), and neutrophils (CD45+, CD193-, CD16+). Medical records were reviewed for bronchiolitis hospitalisation in the first 12 months of life. Statistical analyses were conducted using Stata IC16.1.

Results

Logistic regression adjusted for caesarean section, gestational age, maternal smoking during pregnancy, foetal heart deceleration during labour, and season of birth revealed an association between cord blood eosinophil levels and bronchiolitis hospitalisation in the first 12 months of life with an Area Under the Curve (AUC) of the Receiver Operating Characteristic (ROC) curve of 0.943 (aOR = 1.35, P = 0.011). Neutrophils were associated with the risk of bronchiolitis hospitalisation in a univariable logistic regression (OR = 0.93, P = 0.029); however, there was no statistical significance in the adjusted model.

Conclusions

Higher eosinophil numbers in cord blood were associated with bronchiolitis hospitalisation in the first 12 months in a cohort of infants born to asthmatic mothers. This suggests that susceptibility to bronchiolitis in later life is influenced by the immune cell profile prior to viral infection.

Ally, adversary, or arbitrator? The context-dependent role of eosinophils in vaccination for respiratory viruses and subsequent breakthrough infections

Eosinophils are a critical type of immune cell and central players in type 2 immunity. Existing literature suggests that eosinophils also can play a role in host antiviral responses, typically type 1 immune events, against multiple respiratory viruses, both directly through release of antiviral mediators and indirectly through activation of other effector cell types. One way to prime host immune responses toward effective antiviral responses is through vaccination, where typically a type 1-skewed immunity is desirable in the context of intracellular pathogens like respiratory viruses. In the realm of breakthrough respiratory viral infection in vaccinated hosts, an event in which virus can still establish productive infection despite preexisting immunity, eosinophils are most prominently known for their link to vaccine-associated enhanced respiratory disease upon natural respiratory syncytial virus infection. This was observed in a pediatric cohort during the 1960s following vaccination with formalin-inactivated respiratory syncytial virus. More recent research has unveiled additional roles of the eosinophil in respiratory viral infection and breakthrough infection. The specific contribution of eosinophils to the quality of vaccine responses, vaccine efficacy, and antiviral responses to infection in vaccinated hosts remains largely unexplored, especially regarding their potential roles in protection. On the basis of current findings, we will speculate upon the suggested function of eosinophils and consider the many potential ways by which eosinophils may exert protective and pathological effects in breakthrough infections. We will also discuss how to balance vaccine efficacy with eosinophil-related risks, as well as the use of eosinophils and their products as potential biomarkers of vaccine efficacy or adverse events.

Immunotherapeutic implications on targeting the cytokines produced in rhinovirus-induced immunoreactions

Rhinovirus is a widespread virus associated with several respiratory diseases, especially asthma exacerbation. Currently, there are no accurate therapies for rhinovirus. Encouragingly, it is found that during rhinovirus-induced immunoreactions the levels of certain cytokines in patients' serum will alter. These cytokines may have pivotal pro-inflammatory or anti-inflammatory effects via their specific mechanisms. Thus far, studies have shown that inhibitions of cytokines such as IL-1, IL-4, IL-5, IL-6, IL-13, IL-18, IL-25, and IL-33 may attenuate rhinovirus-induced immunoreactions, thereby relieving rhinovirus infection. Furthermore, such therapeutics for rhinovirus infection can be applied to viruses of other species, with certain practicability.

Dysfunctional neutrophil type 1 interferon responses in preschool children with recurrent wheezing and IL-4-mediated aeroallergen sensitization

Background

The innate mechanisms associated with viral exacerbations in preschool children with recurrent wheezing are not understood.

Objective

We sought to assess differential gene expression in blood neutrophils from preschool children with recurrent wheezing, stratified by aeroallergen sensitization, at baseline and after exposure to polyinosinic:polycytidylic acid (poly(I:C)) and also to examine whether poly(I:C)-stimulated blood neutrophils influenced airway epithelial gene expression.

Methods

Blood neutrophils were purified and cultured overnight with poly(I:C) and underwent next-generation sequencing with Reactome pathway analysis. Primary human small airway epithelial cells were treated with poly(I:C)-treated neutrophil culture supernatants and were analyzed for type 1 interferon gene expression with a targeted array. Symptoms and exacerbations were assessed in participants over 12 months.

Results

A total of 436 genes were differently expressed in neutrophils from children with versus without aeroallergen sensitization at baseline, with significant downregulation of type 1 interferons. These type 1 interferons were significantly upregulated in sensitized children after poly(I:C) stimulation. Confirmatory experiments demonstrated similar upregulation of type 1 interferons in IL-4-treated neutrophils stimulated with poly(I:C). Poly(I:C)-treated neutrophil supernatants from children with aeroallergen sensitization also induced a type 1 interferon response in epithelial cells. Children with aeroallergen sensitization also had higher symptom scores during exacerbations, and these symptom differences persisted for 3 days after prednisolone treatment.

Conclusions

Type 1 interferon responses are dysregulated in preschool children with aeroallergen sensitization, which is in turn associated with exacerbation severity. Given the importance of type 1 interferon signaling in viral resolution, additional studies of neutrophil type 1 interferon responses are needed in this population.

Altered COVID-19 immunity in children with asthma by atopic status

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causes a spectrum of clinical outcomes that may be complicated by severe asthma. Antiviral immunity is often compromised in patients with asthma; however, whether this is true for SARS-CoV-2 immunity and children is unknown.

Objective

We aimed to evaluate SARS-CoV-2 immunity in children with asthma on the basis of infection or vaccination history and compared to respiratory syncytial viral or allergen (eg, cockroach, dust mite)-specific immunity.

Methods

Fifty-three children from an urban asthma study were evaluated for medical history, lung function, and virus- or allergen-specific immunity using antibody or T-cell assays.

Results

Polyclonal antibody responses to spike were observed in most children from infection and/or vaccination history. Children with atopic asthma or high allergen-specific IgE, particularly to dust mites, exhibited reduced seroconversion, antibody magnitude, and SARS-CoV-2 virus neutralization after SARS-CoV-2 infection or vaccination. TH1 responses to SARS-CoV-2 and respiratory syncytial virus correlated with antigen-respective IgG. Cockroach-specific T-cell activation as well as IL-17A and IL-21 cytokines negatively correlated with SARS-CoV-2 antibodies and effector functions, distinct from total and dust mite IgE. Allergen-specific IgE and lack of vaccination were associated with recent health care utilization. Reduced lung function (forced expiratory volume in 1 second ≤ 80%) was independently associated with (SARS-CoV-2) peptide-induced cytokines, including IL-31, whereas poor asthma control was associated with cockroach-specific cytokine responses.

Conclusion

Mechanisms underpinning atopic and nonatopic asthma may complicate the development of memory to SARS-CoV-2 infection or vaccination and lead to a higher risk of repeated infection in these children.

Clinical features in patients with COVID-19 treated with biologics for severe asthma

Background

Few studies have reported the clinical features of patients with coronavirus disease 2019 (COVID-19) who were treated with biologics for severe asthma (SA).

Objective

We sought to elucidate the clinical features and mutual interaction between COVID-19 and SA in terms of disease severity during the Omicron epidemic.

Methods

A retrospective study among patients with SA who received any biologic therapy from January 2022 to February 2023 at Jikei University Hospital (Tokyo, Japan) was performed.

Results

Among 99 patients with SA, 22 women and 6 men suffered from COVID-19, and 1 woman was reinfected. The severity of COVID-19 was mild in 26 cases and moderate in 3 cases. The number of vaccinations among patients with mild COVID-19 was significantly higher than that among patients with moderate COVID-19 (3.0 ± 1.4 vs 1.0 ± 1.0; P = .03). Asthmatic exacerbations were mild in 9 cases and moderate in 7 cases. The severity of asthmatic exacerbations was significantly associated with the Asthma Control Test score at baseline (no/mild/moderate exacerbation = 23.0 ± 2.3/18.1 ± 5.3/15.0 ± 4.3; P = .004; Kruskal-Wallis test). By means of a multivariate logistic regression analysis, a lower number of vaccinations was a significant risk factor for COVID-19 progression (odds ratio, 0.64; 95% CI, 0.46-0.91; P = .006).

Conclusions

During the Omicron epidemic, the onset and severity of COVID-19 were related to the number of vaccinations, and the severity of asthmatic exacerbations caused by COVID-19 was associated with the Asthma Control Test score at baseline and the number of vaccinations but not with the use of biologics.

The role of dendritic cells in respiratory viral infection

Respiratory viral infections represent one of the major causes of death worldwide. The recent coronavirus disease 2019 pandemic alone claimed the lives of over 6 million people around the globe. It is therefore crucial to understand how the immune system responds to these threats and how respiratory infection can be controlled and constrained. Dendritic cells (DCs) are one of the key players in antiviral immunity because of their ability to detect pathogens. They can orchestrate an immune response that will, in most cases, lead to viral clearance. Different subsets of DCs are present in the lung and each subset can contribute to antiviral responses through various mechanisms. In this review, we discuss the role of the different lung DC subsets in response to common respiratory viruses, with a focus on respiratory syncytial virus, influenza A virus and severe acute respiratory syndrome coronavirus 2. We also review how lung DC-mediated responses to respiratory viruses can lead to the worsening of an existing chronic pulmonary disease such as asthma. Throughout the review, we discuss results obtained from animal studies as well as results generated from infected patients.

The SARS-CoV-2 pandemic and asthma: What we have learned and what is still unknown

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has brought new insights into the immunologic intricacies of asthma. In this review, we discuss the epidemiology of asthma in patients infected with SARS-CoV-2 and the risk of severe infection. Type 2 inflammation had an overall protective effect against SARS-CoV-2 infection by various mechanisms summarized in this review. Asthma, intranasal, and inhaled corticosteroids decreased the angiotensin-converting enzyme 2 receptor, an important receptor for SARS-CoV-2 entry into host cells. We summarize the nuances of the treatment of type 2 inflammation despite its underlying protective effects. Research to date has shown that patients on various allergen immunotherapies and biologics do benefit from being vaccinated.

Asthma in the era of COVID-19

Since its global invasion in 2019, COVID-19 has affected several aspects of patients' lives and posed a significant impact on the health care system. Several patient populations were identified to be at high risk of contracting SARS-CoV-2 infection and/or developing severe COVID-19-related sequelae. Conversely, anyone who has contracted SARS-CoV-2 is at risk to experience symptoms and signs consistent with post-COVID manifestations. Patients with asthma were initially thought to be at increased risk and severity for SARS-CoV-2 infection. However, accumulating evidence demonstrates that asthma endotypes/phenotypes and comorbidities influence the risk stratification in this population. Furthermore, initial concerns about the potentially increased risk of poor outcomes with asthma treatments such as inhaled corticosteroids and biologics have not been substantiated. In this review, we provide an update on COVID-19 and asthma, including risk of susceptibility, clinical manifestations and course in this population as well as discuss recommendations for management.

Eosinophils as potential biomarkers in respiratory viral infections

Eosinophils are bone marrow-derived granulocytes that, under homeostatic conditions, account for as much as 1-3% of peripheral blood leukocytes. During inflammation, eosinophils can rapidly expand and infiltrate inflamed tissues, guided by cytokines and alarmins (such as IL-33), adhesion molecules and chemokines. Eosinophils play a prominent role in allergic asthma and parasitic infections. Nonetheless, they participate in the immune response against respiratory viruses such as respiratory syncytial virus and influenza. Notably, respiratory viruses are associated with asthma exacerbation. Eosinophils release several molecules endowed with antiviral activity, including cationic proteins, RNases and reactive oxygen and nitrogen species. On the other hand, eosinophils release several cytokines involved in homeostasis maintenance and Th2-related inflammation. In the context of SARS-CoV-2 infection, emerging evidence indicates that eosinophils can represent possible blood-based biomarkers for diagnosis, prognosis, and severity prediction of disease. In particular, eosinopenia seems to be an indicator of severity among patients with COVID-19, whereas an increased eosinophil count is associated with a better prognosis, including a lower incidence of complications and mortality. In the present review, we provide an overview of the role and plasticity of eosinophils focusing on various respiratory viral infections and in the context of viral and allergic disease comorbidities. We will discuss the potential utility of eosinophils as prognostic/predictive immune biomarkers in emerging respiratory viral diseases, particularly COVID-19. Finally, we will revisit some of the relevant methods and tools that have contributed to the advances in the dissection of various eosinophil subsets in different pathological settings for future biomarker definition.

The Role of Eosinophil-Derived Neurotoxin and Vascular Endothelial Growth Factor in the Pathogenesis of Eosinophilic Asthma

Asthma is a chronic complex pulmonary disease characterized by airway inflammation, remodeling, and hyperresponsiveness. Vascular endothelial growth factor (VEGF) and eosinophil-derived neurotoxin (EDN) are two significant mediators involved in the pathophysiology of asthma. In asthma, VEGF and EDN levels are elevated and correlate with disease severity and airway hyperresponsiveness. Diversity in VEGF polymorphisms results in the variability of responses to glucocorticosteroids and leukotriene antagonist treatment. Targeting VEGF and eosinophils is a promising therapeutic approach for asthma. We identified lichochalcone A, bevacizumab, azithromycin (AZT), vitamin D, diosmetin, epigallocatechin gallate, IGFBP-3, Neovastat (AE-941), endostatin, PEDF, and melatonin as putative add-on drugs in asthma with anti-VEGF properties. Further studies and clinical trials are needed to evaluate the efficacy of those drugs. AZT reduces the exacerbation rate and may be considered in adults with persistent symptomatic asthma. However, the long-term effects of AZT on community microbial resistance require further investigation. Vitamin D supplementation may enhance corticosteroid responsiveness. Herein, anti-eosinophil drugs are reviewed. Among them are, e.g., anti-IL-5 (mepolizumab, reslizumab, and benralizumab), anti-IL-13 (lebrikizumab and tralokinumab), anti-IL-4 and anti-IL-13 (dupilumab), and anti-IgE (omalizumab) drugs. EDN over peripheral blood eosinophil count is recommended to monitor the asthma control status and to assess the efficacy of anti-IL-5 therapy in asthma.

Translating the biology of β common receptor-engaging cytokines into clinical medicine

The family of cytokines that comprises IL-3, IL-5, and GM-CSF was discovered over 30 years ago, and their biological activities and resulting impact in clinical medicine has continued to expand ever since. Originally identified as bone marrow growth factors capable of acting on hemopoietic progenitor cells to induce their proliferation and differentiation into mature blood cells, these cytokines are also recognized as key mediators of inflammation and the pathobiology of diverse immunologic diseases. This increased understanding of the functional repertoire of IL-3, IL-5, and GM-CSF has led to an explosion of interest in modulating their functions for clinical management. Key to the successful clinical translation of this knowledge is the recognition that these cytokines act by engaging distinct dimeric receptors and that they share a common signaling subunit called β-common or βc. The structural determination of how IL-3, IL-5, and GM-CSF interact with their receptors and linking this to their differential biological functions on effector cells has unveiled new paradigms of cell signaling. This knowledge has paved the way for novel mAbs and other molecules as selective or pan inhibitors for use in different clinical settings.

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.