Anti-IL-5 in Mild Asthma Alters Rhinovirus-induced Macrophage, B-Cell, and Neutrophil Responses (MATERIAL). A Placebo-controlled, Double-Blind Study

Mild asthma is not mild: risk factors and predictive biomarkers for severe acute exacerbations and progression in mild asthma

INTRODUCTION

Asthma is a common chronic respiratory disease characterized by chronic airway inflammation, airway hyperresponsiveness, reversible airflow limitation, and airway remodeling. Mild asthma is the most common type of asthma, but it is the most neglected. Sometimes mild asthma can lead to acute severe exacerbations or even death.

AREAS COVERED

This article reviews the epidemiology, risk factors, and possible predictors of acute severe exacerbations and disease progression in mild asthma to improve the understanding of mild asthma and its severe acute exacerbations and progression.

EXPERT OPINION

There is a necessity to improve asthma patient categorization and redefine mild asthma's concept to heighten patient and physician attention. Identifying mild asthma patients that are highly vulnerable to severe acute exacerbations and researching the mechanisms are future prioritizations.

Eosinophil recovery in hospitalized COVID-19 patients is associated with lower rates of ICU admission and in-hospital mortality: An observational cohort analysis

BACKGROUND

Admission eosinopenia (<100 cells/μL) is associated with poor clinical outcomes in hospitalized COVID-19 patients. However, the effects of eosinophil recovery (defined as reaching ≥50 eosinophils/μL) during hospitalization on COVID-19 outcomes have been inconsistent.

METHODS

The study included 1,831 patients admitted to UCLA hospitals between February 2020 and February 2021 with PCR-confirmed COVID-19. Using competing risk regression and modeling eosinophil recovery as a time-dependent covariate, we evaluated the longitudinal relationship between eosinophil recovery and in-hospital outcomes including ICU admission, need for mechanical ventilation, and in-hospital mortality. All analyses were adjusted for covariates including age, BMI, tobacco smoke exposure, comorbidities known to be risk factors for COVID-19 mortality, and treatments including dexamethasone and remdesivir.

RESULTS

Eosinophil recovery was evaluated in patients with <50 eosinophils/μL on admission (n = 1282). These patients cumulatively amassed 11,633 hospital patient-days; 3,985 of those days qualified as eosinophil recovery events, which were represented by 781 patients achieving at least one instance of eosinophil recovery during hospitalization. Despite no significant difference in the rate of mechanical ventilation, eosinophil recoverers had significantly lower rates of in-hospital mortality (aHR: 0.44 [0.29, 0.65], P = 0.001) and ICU admission (aHR: 0.25 [0.11, 0.61], P = 0.002).

CONCLUSION

Trending eosinophil counts during hospitalization is simple and can be performed in resource-limited healthcare settings to track the inflammatory status of a patient. Lack of eosinophil recovery events can identify those at risk for future progression to severe COVID.

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.

Update on virus-induced asthma exacerbations

INTRODUCTION

Viral infections are common triggers for asthma exacerbation. Subjects with asthma are more susceptible to viral infections and develop more severe or long-lasting lower respiratory tract symptoms than healthy individuals owing to impaired immune responses. Of the many viruses associated with asthma exacerbation, rhinovirus (RV) is the most frequently identified virus in both adults and children.

AREAS COVERED

We reviewed epidemiological and clinical links and mechanistic studies on virus-associated asthma exacerbations. We included sections on severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), the latest evidence of coronavirus disease 2019 (COVID-19) in asthma patients, and past and future searches for therapeutic and prevention targets.

EXPERT OPINION

Early treatment or prevention of viral infections might significantly reduce the rate of asthma exacerbation, which is one of the key points of disease management. Although it is hypothetically possible nowadays to interfere with every step of the infectious cycle of respiratory tract viruses, vaccination development has provided some of the most encouraging results. Future research should proceed toward the development of a wider spectrum of vaccines to achieve a better quality of life for patients with asthma and to reduce the economic burden on the healthcare system.

Identification of autoantigens and their potential post-translational modification in EGPA and severe eosinophilic asthma

Background

The chronic airway inflammation in severe eosinophilic asthma (SEA) suggests potential autoimmune aetiology with unidentified autoantibodies analogous to myeloperoxidase (MPO) in ANCA-positive EGPA (eosinophilic granulomatosis with polyangiitis). Previous research has shown that oxidative post-translational modification (oxPTM) of proteins is an important mechanism by which autoantibody responses may escape immune tolerance. Autoantibodies to oxPTM autoantigens in SEA have not previously been studied.

Methods

Patients with EGPA and SEA were recruited as well as healthy control participants. Autoantigen agnostic approach: Participant serum was incubated with slides of unstimulated and PMA-stimulated neutrophils and eosinophils, and autoantibodies to granulocytes were identified by immunofluorescence with anti-human IgG FITC antibody. Target autoantigen approach: Candidate proteins were identified from previous literature and FANTOM5 gene set analysis for eosinophil expressed proteins. Serum IgG autoantibodies to these proteins, in native and oxPTM form, were detected by indirect ELISA.

Results

Immunofluorescence studies showed that serum from patients with known ANCA stained for IgG against neutrophils as expected. In addition, serum from 9 of 17 tested SEA patients stained for IgG to PMA-stimulated neutrophils undergoing NETosis. Immunofluorescent staining of eosinophil slides was evident with serum from all participants (healthy and with eosinophilic disease) with diffuse cytoplasmic staining except for one SEA individual in whom subtle nuclear staining was evident. FANTOM5 gene set analysis identified TREM1 (triggering receptor expressed on myeloid cells 1) and IL-1 receptor 2 (IL1R2) as eosinophil-specific targets to test for autoantibody responses in addition to MPO, eosinophil peroxidase (EPX), and Collagen-V identified from previous literature. Indirect ELISAs found high concentrations of serum autoantibodies to Collagen-V, MPO, and TREM1 in a higher proportion of SEA patients than healthy controls. High concentrations of serum autoantibodies to EPX were evident in serum from both healthy and SEA participants. The proportion of patients with positive autoantibody ELISAs was not increased when examining oxPTM compared to native proteins.

Discussion

Although none of the target proteins studied showed high sensitivity for SEA, the high proportion of patients positive for at least one serum autoantibody shows the potential of more research on autoantibody serology to improve diagnostic testing for severe asthma.

Clinical trial registration

ClinicalTrials.gov, identifier, NCT04671446.

The clinical efficacy of type 2 monoclonal antibodies in eosinophil-associated chronic airway diseases: a meta-analysis

Background

Anti-type 2 inflammation therapy has been proposed as a treatment strategy for eosinophil-associated chronic airway disorders that could reduce exacerbations and improve lung function. We performed a meta-analysis of randomized controlled trials to assess the effectiveness of type 2 monoclonal antibodies (anti-T2s) for eosinophil-associated chronic airway disorders.

Methods

PubMed, Embase, Web of Science, and Cochrane Library were searched from their inception to 21 August 2022. Randomized clinical trials evaluating the effectiveness of anti-T2s versus placebo in the treatment of chronic airway diseases were selected. The outcomes were exacerbation rate and change in pre-bronchodilator forced expiratory volume in 1 s (FEV1) from baseline. The Cochrane Risk of Bias Assessment Tool 1.0 was used to evaluate the risk of bias, and the random-effects or fixed-effect model were used to pool the data.

Results

Thirty-eight articles concerning forty-one randomized clinical trials with 17,115 patients were included. Compared with placebo, anti-T2s therapy yielded a significant reduction in exacerbation rate in COPD and asthma (Rate Ratio (RR)=0.89, 95%CI, 0.83-0.95, I2 = 29.4%; RR= 0.59, 95%CI, 0.52-0.68, I2 = 83.9%, respectively) and improvement in FEV1 in asthma (Standard Mean Difference (SMD)=0.09, 95%CI, 0.08-0.11, I2 = 42.6%). Anti-T2s therapy had no effect on FEV1 improvement in COPD (SMD=0.05, 95%CI, -0.01-0.10, I2 = 69.8%).

Conclusion

Despite inconsistent findings across trials, anti-T2s had a positive overall impact on patients' exacerbation rate in asthma and COPD and FEV1 in asthma. Anti-T2s may be effective in treating chronic airway illnesses related to eosinophils.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022362280.

Living without eosinophils: evidence from mouse and man

The enduring view of eosinophils, as immune effector cells whose primary function is host defence against infection by helminths and other microbial pathogens, sets the stage for a fundamental question regarding the safety of therapeutic eosinophil depletion. If eosinophils are significantly reduced or altogether depleted in an effort to alleviate the negative effects of tissue eosinophilia and eosinophilic inflammation in conditions such as asthma, COPD, chronic rhinosinusitis with nasal polyps, eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndrome, would these patients become susceptible to infection or another illness? Development of mouse models in which the eosinophil lineage has been ablated, observations in patients naturally lacking eosinophils and data from studies of eosinophil-depleting medical therapies indicate that the absence of eosinophils is not detrimental to health. The evidence available to date, as presented in this review, supports the conclusion that even if certain homeostatic roles for the eosinophil may be demonstrable in controlled animal models and human in vitro settings, the evolution of the human species appears to have provided sufficient immune redundancy such that one may be hale and hearty without eosinophils.

A comparison of the effectiveness of biologic therapies for asthma: A systematic review and network meta-analysis

BACKGROUND

Trials have not directly compared biologics for the treatment of asthma.

OBJECTIVE

To compare the relative efficacy of biologics in asthma.

METHODS

We searched MEDLINE, EMBASE, CENTRAL, and clinicaltrials.gov from inception to May 31, 2022 for randomized trials addressing biologic therapies for asthma. Reviewers worked independently and in duplicate to screen references, extract data, and assess risk of bias. We performed a frequentist network meta-analysis and assessed the certainty of evidence using the Grading of Recommendations, Assessment, Development, and Evaluations approach. We present dichotomous outcomes as absolute risk differences per 1000 patients and relative risk with 95% confidence intervals (95% CI) and continuous outcomes as mean difference (MD) and 95% CI.

RESULTS

We identified 64 trials, including 26,630 patients. For patients with eosinophilic asthma, tezepelumab (329 fewer exacerbations per 1000 [95% CI, 272.6-366.6 fewer]) and dupilumab (319.6 fewer exacerbations per 1000 [95% CI, 272.6-357.2 fewer]) reduce exacerbations compared with placebo (high certainty). Tezepelumab (MD, 0.24 L [95% CI, 0.16-0.32]) and dupilumab (0.25 L [95% CI, 0.21-0.29]) improve lung function compared with placebo (high certainty). Both tezepelumab (110.97 fewer hospital admissions per 1000 [95% CI, 94.53-120.56 fewer]) and dupilumab (97.27 fewer hospitalizations [4.11-124.67 fewer]) probably reduce hospital admissions compared with placebo (moderate certainty). For patients with low eosinophils, biologics probably do not improve asthma outcomes. For these patients, tezepelumab (MD, 0.1 L [95% CI, 0-0.19]) and dupilumab (MD, 0.1 L [95% CI, 0-0.20]) may improve lung function (low certainty).

CONCLUSION

Tezepelumab and dupilumab are effective at reducing exacerbations. For patients with low eosinophils, however, clinicians should probably be more judicious in using biologics, including tezepelumab, because they probably do not confer substantial benefit.

T-helper 2 mechanisms involved in human rhinovirus infections and asthma

Human rhinovirus (HRV) is the most common causative agent for the common cold and its respiratory symptoms. For those with asthma, cystic fibrosis, or chronic obstructive pulmonary disease, HRVs can lead to severe and, at times, fatal complications. Furthermore, an array of innate and adaptive host immune responses leads to varying outcomes ranging from subclinical to severe. In this review, we discuss the viral pathogenesis and host immune responses associated with this virus. Specifically, we focus on the immune responses that might skew a T-helper type 2 response, including alarmins, in those with allergic asthma. We also discuss the role of a poor innate immune response with interferons. Finally, we consider therapeutic options for HRV-associated exacerbations of asthma, including biologics and intranasal sprays on the basis of the current literature.

The roles of eosinophils and interleukin-5 in the pathophysiology of chronic rhinosinusitis with nasal polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) is generally associated with eosinophilic tissue infiltration linked to type 2 inflammation and characterized by elevated levels of interleukin (IL)-5 and other type 2 inflammatory mediators. Although distinct and overlapping contributions of eosinophils and IL-5 to CRSwNP pathology are still being explored, they are both known to play an important role in NP inflammation. Eosinophils secrete numerous type 2 inflammatory mediators including granule proteins, enzymes, cytokines, chemokines, growth factors, lipids, and oxidative products. IL-5 is critical for the differentiation, migration, activation, and survival of eosinophils but is also implicated in the biological functions of mast cells, basophils, innate lymphoid cells, B cells, and epithelial cells. Results from clinical trials of therapeutics that target type 2 inflammatory mediators (including but not limited to anti-IL-5, anti-immunoglobulin-E, and anti-IL-4/13) may provide further evidence of how eosinophils and IL-5 contribute to CRSwNP. Finally, the association between eosinophilia/elevated IL-5 and greater rates of NP recurrence after endoscopic sinus surgery (ESS) suggests that these mediators may have utility as biomarkers of NP recurrence in diagnosing and assessing the severity of CRSwNP. This review provides an overview of eosinophil and IL-5 biology and explores the literature regarding the role of these mediators in CRSwNP pathogenesis and NP recurrence following ESS. Based on current published evidence, we suggest that although eosinophils play a key role in CRSwNP pathophysiology, IL-5, a cytokine that activates these cells, also represents a pertinent and effective treatment target in patients with CRSwNP.

Viral Infection and Airway Epithelial Immunity in Asthma

Viral respiratory tract infections are associated with asthma development and exacerbation in children and adults. In the course of immune responses to viruses, airway epithelial cells are the initial platform of innate immunity against viral invasion. Patients with severe asthma are more vulnerable than those with mild to moderate asthma to viral infections. Furthermore, in most cases, asthmatic patients tend to produce lower levels of antiviral cytokines than healthy subjects, such as interferons produced from immune effector cells and airway epithelial cells. The epithelial inflammasome appears to contribute to asthma exacerbation through overactivation, leading to self-damage, despite its naturally protective role against infectious pathogens. Given the mixed and complex immune responses in viral-infection-induced asthma exacerbation, this review examines the diverse roles of airway epithelial immunity and related potential therapeutic targets and discusses the mechanisms underlying the heterogeneous manifestations of asthma exacerbations.

A Brief History of Human Challenge Studies (1900-2021) Emphasising the Virology, Regulatory and Ethical Requirements, Raison D'etre, Ethnography, Selection of Volunteers and Unit Design

Venetian quarantine 400 years ago was an important public health measure. Since 1900 this has been refined to include "challenge" or deliberate infection with pathogens be they viruses, bacteria, or parasites. Our focus is virology and ranges from the early experiments in Cuba with Yellow Fever Virus to the most widespread pathogen of our current times, COVID-19. The latter has so far caused over four million deaths worldwide and 190 million cases of the disease. Quarantine and challenge were also used to investigate the Spanish Influenza of 1918 which caused over 100 million deaths. We consider here the merits of the approach, that is the speeding up of knowledge in a practical sense leading to the more rapid licensing of vaccines and antimicrobials. At the core of quarantine and challenge initiatives is the design of the unit to allow safe confinement of the pathogen and protection of the staff. Most important though is the safety of volunteers. We can see now, as in 1900, that members of our society are prepared and willing to engage in these experiments for the public good. Our ethnology study, where the investigator observed the experiment from within the quarantine, gave us the first indication of changing attitudes amongst volunteers whilst in quarantine. These quarantine experiments, referred to as challenge studies, human infection studies, or "controlled human infection models" involve thousands of clinical samples taken over two to three weeks and can provide a wealth of immunological and molecular data on the infection itself and could allow the discovery of new targets for vaccines and therapeutics. The Yellow Fever studies from 121 years ago gave the impetus for development of a successful vaccine still used today whilst also uncovering the nature of the Yellow Fever agent, namely that it was a virus. We outline how carefully these experiments are approached and the necessity to have high quality units with self-contained air-flow along with extensive personal protective equipment for nursing and medical staff. Most important is the employment of highly trained scientific, medical and nursing staff. We face a future of emerging pathogens driven by the increasing global population, deforestation, climate change, antibiotic resistance and increased global travel. These emerging pathogens may be pathogens we currently are not aware of or have not caused outbreaks historically but could also be mutated forms of known pathogens including viruses such as influenza (H7N9, H5N1 etc.) and coronaviruses. This calls for challenge studies to be part of future pandemic preparedness as an additional tool to assist with the rapid development of broad-spectrum antimicrobials, immunomodulators and new vaccines.

Effectiveness and Durability of mRNA Vaccine-Induced SARS-CoV-2-Specific Humoral and Cellular Immunity in Severe Asthma Patients on Biological Therapy

Coronavirus disease 2019 (COVID-19) vaccines effectively elicit humoral and cellular immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in healthy populations. This immunity decreases several months after vaccination. However, the efficacy of vaccine-induced immunity and its durability in patients with severe asthma on biological therapy are unknown. In this study, we evaluated the effectiveness and durability of mRNA vaccine-induced SARS-CoV-2-specific humoral and cellular immunity in severe asthma patients on biological therapy. The study included 34 patients with severe asthma treated with anti-IgE (omalizumab, n=17), anti-IL5 (mepolizumab, n=13; reslizumab, n=3), or anti-IL5R (benralizumab, n=1) biological therapy. All patients were vaccinated with two doses of the BNT162b2 mRNA vaccine with a 6-week interval between the doses. We found that this COVID-19 vaccination regimen elicited SARS-CoV-2-specific humoral and cellular immunity, which had significantly declined 6 months after receipt of the second dose of the vaccine. The type of biological treatment did not affect vaccine-elicited immunity. However, patient age negatively impacted the vaccine-induced humoral response. On the other hand, no such age-related impact on vaccine-elicited cellular immunity was observed. Our findings show that treatment of patients with severe asthma with biological therapy does not compromise the effectiveness or durability of COVID-19 vaccine-induced immunity.

The regulatory role of eosinophils in viral, bacterial, and fungal infections

Eosinophils are innate immune cells typically associated with allergic and parasitic diseases. However, in recent years, eosinophils have also been ascribed a role in keeping homeostasis and in fighting several infectious diseases. Indeed, these cells circulate as mature cells in the blood and can be quickly recruited to the infected tissue. Moreover, eosinophils have all the necessary cellular equipment such as pattern recognition receptors (PRRs), pro-inflammatory cytokines, anti-bacterial proteins, and DNA traps to fight pathogens and promote an efficient immune response. This review summarizes some of the updated information on the role of eosinophils' direct and indirect mediated interactions with pathogens.

Imprinting of bronchial epithelial cells upon in vivo rhinovirus infection in people with asthma

Background

Defective translocation of the translational repressor TIAR (T-cell internal antigen receptor) in bronchial epithelial cells (BECs) from asthma patients underlies epithelial hyperresponsiveness, reflected by an exaggerated production of a select panel of inflammatory cytokines such as CXCL-8, interleukin (IL)-6, granulocyte colony-stimulating factor, CXCL-10, upon exposure to tumour necrosis factor (TNF) and IL-17A. With this study we aimed to clarify whether epithelial hyperresponsiveness is a consistent finding, is changed upon in vivo exposure to rhinovirus (RV)-A16 and applies to the bronchoconstrictor endothelin-1.

Methods

BECs were obtained from asthma patients (n=18) and healthy individuals (n=11), 1 day before and 6 days post-RV-A16 exposure. BECs were cultured and stimulated with TNF and IL-17A and inflammatory mediators were analysed. The bronchoalveolar lavage fluid (BALF) was obtained in parallel with BECs to correlate differential cell counts and inflammatory mediators with epithelial hyperresponsiveness.

Results

Epithelial hyperresponsiveness was confirmed in sequential samples and even increased in BECs from asthma patients after RV-A16 exposure, but not in BECs from healthy individuals. Endothelin-1 tended to increase in BECs from asthma patients collected after RV-A16 exposure, but not in BECs from healthy individuals. In vitro CXCL-8 and endothelin-1 production correlated. In vivo relevance for in vitro CXCL-8 and endothelin-1 production was shown by correlations with forced expiratory volume in 1 s % predicted and CXCL-8 BALF levels.

Conclusion

Epithelial hyperresponsiveness is an intrinsic defect in BECs from asthma patients, which increases upon viral exposure, but not in BECs from healthy individuals. This epithelial hyperresponsiveness also applies to the bronchoconstrictor endothelin-1, which could be involved in airway obstruction.

Epithelial hyperresponsiveness is an intrinsic defect in bronchial epithelium from asthma patients, which increases upon rhinovirus exposure, but not in healthy individualshttps://bit.ly/3xLhjuj

Lower viral loads in subjects with rhinovirus-challenged allergy despite reduced innate immunity

BACKGROUND

Viral infections, especially those caused by rhinovirus, are the most common cause of asthma exacerbations. Previous studies have argued that impaired innate antiviral immunity and, as a consequence, more severe infections contribute to these exacerbations.

OBJECTIVE

These studies explored the innate immune response in the upper airway of volunteers with allergic rhinitis and asthma in comparison to healthy controls and interrogated how these differences corresponded to severity of infection.

METHODS

Volunteers with allergic rhinitis, those with asthma, and those who are healthy were inoculated with rhinovirus A16 and monitored for clinical symptoms. Tissue and nasal wash samples were evaluated for antiviral signature and viral load.

RESULTS

Both subjects with allergic rhinitis and asthma were found to have more severe cold symptoms. Subjects with asthma had worsened asthma control and increased bronchial hyperreactivity in the setting of higher fractional exhaled breath nitric oxide and blood eosinophils. These studies confirmed reduced expression of interferons and virus-specific pattern recognition receptors in both cohorts with atopy. Nevertheless, despite this defect in innate immunity, volunteers with allergic rhinitis/asthma had reduced rhinovirus concentrations in comparison to the controls.

CONCLUSION

These results confirm that the presence of an allergic inflammatory disorder of the airway is associated with reduced innate immune responsive to rhinovirus infection. Despite this, these volunteers with allergy have reduced viral loads, arguing for the presence of a compensatory mechanism to clear the infection.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02910401.

Are serum immunoglobulin concentrations a predictive biomarker of response to anti-IL5/IL5Rα therapies?

BACKGROUND

Approval of biologics has recently revolutionized T2 severe asthma management. However, predictive biomarkers remain highly needed to improve patient's selection.

OBJECTIVE

This study aims to determine whether serum immunoglobulins (Igs) levels might be predictive biomarkers of response to anti-interleukin-5 (IL5)/IL5Rα therapies.

METHODS

Severe asthma patients eligible for mepolizumab or benralizumab were included herein. Serum immunoglobulin quantification was performed at baseline before mepolizumab or benralizumab initiation. After a 6-month treatment of mepolizumab or benralizumab, patients presented a second serum immunoglobulin quantification. The treatment response was evaluated by the GETE (Global Evaluation of Treatment Effectiveness) score at 6 months.

RESULTS

A total of 50 patients were included. Median age was 56 [IQR 48.8-65.3] and 50% were females. Compared to baseline, a significant increase in IgG was observed at 6 months (9.2 [7.8-10.2] g/l vs 10.1 [8.8-11.1] g/l, p = 0.04). The area under the ROC curve was 0.58 [95%IC 0.40-0.77] for blood eosinophil count (p = 0.37), 0.75 [95%IC: 0.58-0.92] for serum IgG concentration (p = 0.009) for predicting the treatment response. According to the Youden index, serum IgG concentration ≥ 9.2 g/l predicts the response to anti-IL5 therapies with a sensitivity of 76.9% and a specificity of 75.7%.

CONCLUSION

Baseline serum IgG concentrations may be a useful tool to predict the response to anti-IL5/IL5Rα therapies but should be confirmed in larger clinical trials. Interestingly, anti-IL5/IL5Rα therapies are associated with a significant increase in serum IgG concentrations at 6 months.

Pulmonary Eosinophils at the Center of the Allergic Space-Time Continuum

Eosinophils are typically a minority population of circulating granulocytes being released from the bone-marrow as terminally differentiated cells. Besides their function in the defense against parasites and in promoting allergic airway inflammation, regulatory functions have now been attributed to eosinophils in various organs. Although eosinophils are involved in the inflammatory response to allergens, it remains unclear whether they are drivers of the asthma pathology or merely recruited effector cells. Recent findings highlight the homeostatic and pro-resolving capacity of eosinophils and raise the question at what point in time their function is regulated. Similarly, eosinophils from different physical locations display phenotypic and functional diversity. However, it remains unclear whether eosinophil plasticity remains as they develop and travel from the bone marrow to the tissue, in homeostasis or during inflammation. In the tissue, eosinophils of different ages and origin along the inflammatory trajectory may exhibit functional diversity as circumstances change. Herein, we outline the inflammatory time line of allergic airway inflammation from acute, late, adaptive to chronic processes. We summarize the function of the eosinophils in regards to their resident localization and time of recruitment to the lung, in all stages of the inflammatory response. In all, we argue that immunological differences in eosinophils are a function of time and space as the allergic inflammatory response is initiated and resolved.

Eosinophils in Health and Disease: A State-of-the-Art Review

Eosinophils play a homeostatic role in the body's immune responses. These cells are involved in combating some parasitic, bacterial, and viral infections and certain cancers and have pathologic roles in diseases including asthma, chronic rhinosinusitis with nasal polyps, eosinophilic gastrointestinal disorders, and hypereosinophilic syndromes. Treatment of eosinophilic diseases has traditionally been through nonspecific eosinophil attenuation by use of glucocorticoids. However, several novel biologic therapies targeting eosinophil maturation factors, such as interleukin (IL)-5 and the IL-5 receptor or IL-4/IL-13, have recently been approved for clinical use. Despite the success of biologic therapies, some patients with eosinophilic inflammatory disease may not achieve adequate symptom control, underlining the need to further investigate the contribution of patient characteristics, such as comorbidities and other processes, in driving ongoing disease activity. New research has shown that eosinophils are also involved in several homeostatic processes, including metabolism, tissue remodeling and development, neuronal regulation, epithelial and microbiome regulation, and immunoregulation, indicating that these cells may play a crucial role in metabolic regulation and organ function in healthy humans. Consequently, further investigation is needed into the homeostatic roles of eosinophils and eosinophil-mediated processes across different tissues and their varied microenvironments. Such work may provide important insights into the role of eosinophils not only under disease conditions but also in health. This narrative review synthesizes relevant publications retrieved from PubMed informed by author expertise to provide new insights into the diverse roles of eosinophils in health and disease, with particular emphasis on the implications for current and future development of eosinophil-targeted therapies.

Prevention and Treatment of Asthma Exacerbations in Adults

Asthma exacerbations are major contributors to disease morbidity in patients of all ages. To develop strategies that reduce the disease burden from exacerbations, it is helpful to review current concepts about the risk factors for asthma attacks and current approaches for prevention and treatment. Multiple factors contribute as risks and to the development of asthma exacerbations, including allergic and infectious processes. Viral respiratory infections, primarily from rhinoviruses, are the dominant exacerbating cause for most asthma patients. Allergic sensitization and allergen exposure contribute directly and enhance susceptibility for respiratory viral infections. Respiratory viruses infect airway epithelium to promote underlying type 2 inflammation with eosinophils, the predominant cellular component of increased inflammation. Deficiencies of antiviral interferon responses and generation have been identified that increase susceptibility to viral infections in asthma. Exacerbation treatment focuses on reducing airflow obstruction and suppressing inflammation, followed by improving long-term asthma control. Increasing concern exists regarding the side effects associated with frequent systemic corticosteroid use. A major advance has been the selective use of biologics to prevent exacerbations, primarily in patients with existing type 2 inflammation. Future research to prevent exacerbations is being directed toward antiviral activity and a more encompassing regulation of underlying airway inflammation.

Comparison of Sinonasal Histopathological Changes in Biological Treatment of Eosinophilic Chronic Rhinosinusitis

BACKGROUND

Biologic therapies such as mepolizumab and benralizumab are currently utilised in the treatment of eosinophilic asthma, and are emerging in the management of eosinophilic chronic rhinosinusitis (eCRS). These biologics inhibit the interaction of IL-5 with its receptor, thus impairing cytokine signalling and eosinophil inflammation. Mepolizumab does so by targeting IL-5, whereas benralizumab targets the α chain of the IL-5 receptor. This study compares the sinonasal tissue response to anti-IL-5 biologic therapies in patients with eCRS.

METHODS

A cross-sectional study of adult eCRS patients who had completed at least 2 cycles of biologic therapy and underwent endoscopic sinus surgery as part of their management were included. Sinonasal mucosal tissue biopsies were obtained intraoperatively and assessed with structured histopathological examination. Comparisons of tissue histopathology outcomes following treatment with mepolizumab or benralizumab were performed.

RESULTS

18 patients (age 49.6 ± 14.2 years, 47% female, 100% co-morbid asthma) were included in this study, comprising 10 patients managed with mepolizumab and 8 patients managed with benralizumab. Even after mepolizumab, the tissue had predominantly eosinophilic inflammation compared to benralizumab (90% v 0%, p < 0.01), which demonstrated a greater lymphoplasmacytic inflammation (10% v 75%, χ²(2) = 14.53, p < 0.01). Compared with benralizumab, mepolizumab had increased tissue eosinophil count (100% v 37.5% >10 eosinophils/HPF, τ^b = -8.47, p < 0.001) and more severe subepithelial oedema (80% v 37.5% severe, τ^b = -2.37, p = 0.02).

CONCLUSION

Tissue histopathologic outcomes reflect the differing mechanism of action of mepolizumab and benralizumab in eCRS. Further analysis at the tissue level will provide further information to guide application of mAbs in type 2 inflammatory diseases.

Clinical effects and immune modulation of biologics in asthma

Asthma is considered a syndrome composed of heterogeneous disorders involving complex chronic airway inflammation. Patients with severe asthma, prolonged symptoms, and frequent asthma exacerbations, despite high doses of inhaled corticosteroids, may benefit from treatment with biologics. Four types of biologics are available for severe asthma, including an anti-immunoglobulin E (IgE) antibody (omalizumab), anti-interleukin (IL)-5 antibody (mepolizumab and reslizumab), anti-IL-5 receptor α antibody (benralizumab), and anti-IL-4 receptor α antibody (dupilumab). Biologics for patients with severe asthma demonstrate high therapeutic efficacy and provide significant clinical benefits, including the prevention of asthma exacerbations, alleviation of symptoms, improvement in the quality of life and respiratory function, and reduction in frequencies of hospitalization and emergency outpatient visits. This review provides an overview of the modulation of immunological features by each of the four established biologics in patients with severe allergic asthma. Given the extensive immunomodulatory effects of biologics, further analyses of their precise effects on the human immune system are warranted.

Immunological Aspects Related to Viral Infections in Severe Asthma and the Role of Omalizumab

Viral respiratory infections are recognized risk factors for the loss of control of allergic asthma and the induction of exacerbations, both in adults and children. Severe asthma is more susceptible to virus-induced asthma exacerbations, especially in the presence of high IgE levels. In the course of immune responses to viruses, an initial activation of innate immunity typically occurs and the production of type I and III interferons is essential in the control of viral spread. However, the Th2 inflammatory environment still appears to be protective against viral infections in general and in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections as well. As for now, literature data, although extremely limited and preliminary, show that severe asthma patients treated with biologics don't have an increased risk of SARS-CoV-2 infection or progression to severe forms compared to the non-asthmatic population. Omalizumab, an anti-IgE monoclonal antibody, exerts a profound cellular effect, which can stabilize the effector cells, and is becoming much more efficient from the point of view of innate immunity in contrasting respiratory viral infections. In addition to the antiviral effect, clinical efficacy and safety of this biological allow a great improvement in the management of asthma.

Anti-IL5 Drugs in COVID-19 Patients: Role of Eosinophils in SARS-CoV-2-Induced Immunopathology

SARS-CoV-2 infection stimulates a complex activation of the immune system. Eosinophils belong to the host’s defense equipment against respiratory viruses. In the first phase of the infection, eosinophils contribution is probably appropriate and beneficial, as they facilitate the suppression of the viral replication. However, in severe COVID-19 patients, during the second and third phases of the disease, eosinophils may participate in a maladaptive immune response and directly contribute to immunopathology. In fact, in severe patients, the immune response is prevalently T helper 1 type, but T helper 2 is also present. Eosinophils’ expansion and activation are stimulated by Type 2 cytokines, especially IL-5. Moreover, bronchial asthma, in which eosinophils play a central role, seems not to be a major risk factor for severe COVID-19. Among possible explanations, asthmatic patients are often treated with corticosteroids, which have been demonstrated to reduce the progression to critical COVID-19 in hospitalized patients. In addition to steroids, severe asthmatic patients are currently treated with biological drugs that target Type 2 immune response. Because IL-5 is necessary for the growth, survival, and activation of eosinophils, IL-5 inhibitors, such as mepolizumab, decrease the peripheral blood count of eosinophils, but do not influence eosinophils activation in the airway. In severe COVID-19 patients, the blockade of eosinophils’ activation might contrast harmful immunity.

The impact of COVID-19 on patients with asthma

Background

An association between the severity of coronavirus disease 2019 (COVID-19) and the presence of certain chronic conditions has been suggested. However, unlike influenza and other viruses, the disease burden of COVID-19 in patients with asthma has been less evident.

Objective

To understand the impact of COVID-19 in patients with asthma.

Methods

Using big-data analytics and artificial intelligence through the SAVANA Manager clinical platform, we analysed clinical data from patients with asthma from January 1 to May 10, 2020.

Results

Out of 71 182 patients with asthma, 1006 (1.41%) suffered from COVID-19. Compared to asthmatic individuals without COVID-19, patients with asthma and COVID-19 were significantly older (55 versus 42 years), predominantly female (66% versus 59%), smoked more frequently and had higher prevalence of hypertension, dyslipidaemias, diabetes and obesity. Allergy-related factors such as rhinitis and eczema were less common in asthmatic patients with COVID-19 (p<0.001). In addition, higher prevalence of these comorbidities was observed in patients with COVID-19 who required hospital admission. The use of inhaled corticosteroids (ICS) was lower in patients who required hospitalisation due to COVID-19, as compared to non-hospitalised patients (48.3% versus 61.5%; OR 0.58, 95% CI 0.44–0.77). Although patients treated with biologics (n=865; 1.21%) showed increased severity and more comorbidities at the ear, nose and throat level, COVID-19-related hospitalisations in these patients were relatively low (0.23%).

Conclusion

Patients with asthma and COVID-19 were older and at increased risk due to comorbidity-related factors. ICS and biologics are generally safe and may be associated with a protective effect against severe COVID-19 infection.

The increased risk of hospitalisation due to COVID-19 in patients with asthma is largely associated with age and related comorbidities. ICS and biologics may be associated with a protective effect against the most severe manifestations of COVID-19. https://bit.ly/37yhr5b

Relationship between blood eosinophil levels and COVID-19 mortality

OBJECTIVES

A novel coronavirus, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), is causing the worldwide coronavirus disease 2019 (COVID-19) outbreak with high mortality. A unique finding among COVID-19 patients was a decline of eosinophil levels (eosinopenia). However, results from previous studies on the relationship between eosinopenia and disease severity were inconsistent. The objective of this study is to determine the relationship between eosinopenia and COVID-19 mortality as well as the clinical conditions that could potentially lead to mortality.

METHODS

One hundred ninety patients diagnosed as moderate, severe, or critical COVID-19 at hospital admission were enrolled. Data collected from patients' medical records on the second day after hospital admission included medical histories, clinical symptoms, chest images of computed tomography (CT), laboratory examinations, and outcomes.

RESULTS

Eosinophil levels were significantly lower in patients with critical disease, when compared to those with moderate and severe diseases. After controlled for confounding factors, ie, age, gender, hypertension, coronary heart disease, diabetes, and chronic lung disease, a progressive decline of eosinophil levels was independently associated with mortality. Moreover, eosinophil levels significantly and positively correlated with platelet and D-dimer levels but significantly and inversely correlated with serum levels of urea, creatinine, aspartate aminotransferase, lactate dehydrogenase, and creatine kinase.

CONCLUSIONS

Eosinopenia, if progressively worsening, indicates that COVID-19 patients may progress to critical disease and have a significantly higher chance of mortality. Additionally, eosinopenia correlates with biomarkers of coagulation disorder and those of tissue damage in kidney, liver, and other tissues.

Metabolic differences between bronchial epithelium from healthy individuals and patients with asthma and the effect of bronchial thermoplasty

BACKGROUND

Asthma is a heterogeneous disease with differences in onset, severity, and inflammation. Bronchial epithelial cells (BECs) contribute to asthma pathophysiology.

OBJECTIVE

We determined whether transcriptomes of BECs reflect heterogeneity in inflammation and severity in asthma, and whether this was affected in BECs from patients with severe asthma after their regeneration by bronchial thermoplasty.

METHODS

RNA sequencing was performed on BECs obtained by bronchoscopy from healthy controls (n = 16), patients with mild asthma (n = 17), patients with moderate asthma (n = 5), and patients with severe asthma (n = 17), as well as on BECs from treated and untreated airways of the latter (also 6 months after bronchial thermoplasty) (n = 23). Lipidome and metabolome analyses were performed on cultured BECs from healthy controls (n = 7); patients with severe asthma (n = 9); and, for comparison, patients with chronic obstructive pulmonary disease (n = 7).

RESULTS

Transcriptome analysis of BECs from patients showed a reduced expression of oxidative phosphorylation (OXPHOS) genes, most profoundly in patients with severe asthma but less profoundly and more heterogeneously in patients with mild asthma. Genes related to fatty acid metabolism were significantly upregulated in asthma. Lipidomics revealed enhanced levels of lipid species (phosphatidylcholines, lysophosphatidylcholines. and bis(monoacylglycerol)phosphate), whereas levels of OXPHOS metabolites were reduced in BECs from patients with severe asthma. BECs from patients with mild asthma characterized by hyperresponsive production of mediators implicated in neutrophilic inflammation had decreased expression of OXPHOS genes compared with that in BECs from patients with mild asthma with normoresponsive production. BECs obtained after thermoplasty had significantly increased expression of OXPHOS genes and decreased expression of fatty acid metabolism genes compared with BECs obtained from untreated airways.

CONCLUSION

BECs in patients with asthma are metabolically different from those in healthy individuals. These differences are linked with inflammation and asthma severity, and they can be reversed by bronchial thermoplasty.

Anti-alarmins in asthma: targeting the airway epithelium with next-generation biologics

Monoclonal antibody therapies have significantly improved treatment outcomes for patients with severe asthma; however, a significant disease burden remains. Available biologic treatments, including anti-immunoglobulin (Ig)E, anti-interleukin (IL)-5, anti-IL-5Rα and anti-IL-4Rα, reduce exacerbation rates in study populations by approximately 50% only. Furthermore, there are currently no effective treatments for patients with severe, type 2-low asthma. Existing biologics target immunological pathways that are downstream in the type 2 inflammatory cascade, which may explain why exacerbations are only partly abrogated. For example, type 2 airway inflammation results from several inflammatory signals in addition to IL-5. Clinically, this can be observed in how fractional exhaled nitric oxide (F_eNO), which is driven by IL-13, may remain unchanged during anti-IL-5 treatment despite reduction in eosinophils, and how eosinophils may remain unchanged during anti-IL-4Rα treatment despite reduction in F_eNO. The broad inflammatory response involving cytokines including IL-4, IL-5 and IL-13 that ultimately results in the classic features of exacerbations (eosinophilic inflammation, mucus production and bronchospasm) is initiated by release of “alarmins” thymic stromal lymphopoietin (TSLP), IL-33 and IL-25 from the airway epithelium in response to triggers. The central, upstream role of these epithelial cytokines has identified them as strong potential therapeutic targets to prevent exacerbations and improve lung function in patients with type 2-high and type 2-low asthma. This article describes the effects of alarmins and discusses the potential role of anti-alarmins in the context of existing biologics. Clinical phenotypes of patients who may benefit from these treatments are also discussed, including how biomarkers may help identify potential responders.

Blocking epithelial alarmins, upstream mediators triggered early in the asthma inflammatory response that orchestrate broad inflammatory effects, is a promising alternative approach to asthma treatment, which may be effective in a broad patient population https://bit.ly/2zqoXAw

Virus-Induced Asthma Exacerbations: SIRT1 Targeted Approach

The prevalence of asthma has increased worldwide. Asthma exacerbations triggered by upper respiratory tract viral infections remain a major clinical problem and account for hospital admissions and time lost from work. Virus-induced asthma exacerbations cause airway inflammation, resulting in worsening asthma and deterioration in the patients’ quality of life, which may require systemic corticosteroid therapy. Despite recent advances in understanding the cellular and molecular mechanisms underlying asthma exacerbations, current therapeutic modalities are inadequate for complete prevention and treatment of these episodes. The pathological role of cellular senescence, especially that involving the silent information regulator 2 homolog sirtuin (SIRT) protein family, has recently been demonstrated in stable and exacerbated chronic respiratory disease states. This review discusses the role of SIRT1 in the pathogenesis of bronchial asthma. It also discusses the role of SIRT1 in inflammatory cells that play an important role in virus-induced asthma exacerbations. Recent studies have hypothesized that SIRT1 is one of major contributors to cellular senescence. SIRT1 levels decrease in Th2 and non-Th2-related airway inflammation, indicating the role of SIRT1 in several endotypes and phenotypes of asthma. Moreover, several models have demonstrated relationships between viral infection and SIRT1. Therefore, targeting SIRT1 is a novel strategy that may be effective for treating virus-induced asthma exacerbations in the future.

Allergy clinics in times of the SARS-CoV-2 pandemic: an integrated model

BACKGROUND

Almost the entire World is experiencing the Coronavirus-Disease-2019 (COVID-19) pandemic, responsible, at the end of May 2020, of more than five million people infected worldwide and about 350,000 deaths. In this context, a deep reorganization of allergy clinics, in order to ensure proper diagnosis and care despite of social distancing measures expose, is needed.

MAIN TEXT

The reorganization of allergy clinics should include programmed checks for severe and poorly controlled patients, application of digital medicine service for mild-to-moderate disease in well-controlled ones, postponement of non urgent diagnostic work-ups and domiciliation of therapies, whenever possible. As far as therapies, allergen immunotherapy (AIT) should not be stopped and sublingual immunotherapy (SLIT) fits perfectly for this purpose, since a drug home-delivery service can be activated for the entire pandemic duration. Moreover, biologic agents for severe asthma, chronic spontaneous urticaria and atopic dermatitis should be particularly encouraged to achieve best control possible of severe disease in times of COVID-19 and, whenever possible, home-delivery and self-administration should be the preferred choice.

CONCLUSION

During COVID-19 pandemic, allergists have the responsibility of balancing individual patients' needs with public health issues, and innovative tools, such as telemedicine and digital medicine services, can be helpful to reduce the risk of viral spreading while delivering up-to-date personalized care.

Childhood asthma heterogeneity at the era of precision medicine: Modulating the immune response or the microbiota for the management of asthma attack

Exacerbations are a main characteristic of asthma. In childhood, the risk is increasing with severity. Exacerbations are a strong phenotypic marker, particularly of severe and therapy-resistant asthma. These early-life events may influence the evolution and be involved in lung function decline.

In children, asthma attacks are facilitated by exposure to allergens and pollutants, but are mainly triggered by microbial agents. Multiple studies have assessed immune responses to viruses, and to a lesser extend bacteria, during asthma exacerbation. Research has identified impairment of innate immune responses in children, related to altered pathogen recognition, interferon release, or anti-viral response. Influence of this host-microbiota dialog on the adaptive immune response may be crucial, leading to the development of biased T helper (Th)2 inflammation. These dynamic interactions may impact the presentations of asthma attacks, and have long-term consequences.

The aim of this review is to synthesize studies exploring immune mechanisms impairment against viruses and bacteria promoting asthma attacks in children. The potential influence of the nature of infectious agents and/or preexisting microbiota on the development of exacerbation is also addressed. We then discuss our understanding of how these diverse host-microbiota interactions in children may account for the heterogeneity of endotypes and clinical presentations. Finally, improving the knowledge of the pathophysiological processes induced by infections has led to offer new opportunities for the development of preventive or curative therapeutics for acute asthma. A better definition of asthma endotypes associated with precision medicine might lead to substantial progress in the management of severe childhood asthma.

Eosinophil responses during COVID-19 infections and coronavirus vaccination

Eosinophils are circulating and tissue-resident leukocytes that have potent proinflammatory effects in a number of diseases. Recently, eosinophils have been shown to have various other functions, including immunoregulation and antiviral activity. Eosinophil levels vary dramatically in a number of clinical settings, especially following eosinophil-targeted therapy, which is now available to selectively deplete these cells. There are key coronavirus disease 2019 (COVID-19)-related questions concerning eosinophils whose answers affect recommended prevention and care. First, do patients with eosinophilia-associated diseases have an altered course of COVID-19? Second, do patients with eosinopenia (now intentionally induced by biological drugs) have unique COVID-19 susceptibility and/or disease course? This is a particularly relevant question because eosinopenia is associated with acute respiratory deterioration during infection with the severe acute respiratory syndrome coronavirus 2, the causative agent of COVID-19. Third, do eosinophils contribute to the lung pathology induced during COVID-19 and will they contribute to immunopotentiation potentially associated with emerging COVID-19 vaccines? Herein, we address these timely questions and project considerations during the emerging COVID-19 pandemic.

Understanding the asthmatic response to an experimental rhinovirus infection: Exploring the effects of blocking IgE

BACKGROUND

Rhinovirus frequently causes asthma exacerbations among children and young adults who are allergic. The interaction between allergen and rhinovirus-induced symptoms and inflammation over time is unclear.

OBJECTIVE

Our aim was to compare the response to an experimental inoculation with rhinovirus-16 in allergic asthmatics with the response in healthy controls and to evaluate the effects of administrating omalizumab before and during the infection.

METHODS

Two clinical trials were run in parallel. In one of these trials, the response to an experimental inoculation with rhinovirus-16 among asthmatics with high levels of total IgE was compared to the response in healthy controls. The other trial compared the effects of administering omalizumab versus placebo to asthmatics in a randomized, double-blind placebo-controlled investigation. The primary outcome for both trials compared lower respiratory tract symptoms (LRTSs) between study groups over the first 4 days of infection.

RESULTS

Frequent comparisons of symptoms, lung function, and blood eosinophil counts revealed differences that were more pronounced among allergic asthmatics than among controls by days 2 and 3 after virus inoculation. Additionally, an augmentation of upper respiratory tract symptom scores and LRTS scores occurred among the atopic asthmatics versus the controls during the resolution of symptoms (P < .01 for upper respiratory symptom tract scores and P < .001 for LRTS scores). The beneficial effects of administering omalizumab on reducing LRTSs and improving lung function were strongest over the first 4 days.

CONCLUSIONS

LRTSs and blood eosinophil counts were augmented and lung function was reduced among allergic asthmatics early after rhinovirus inoculation but increased late in the infection during symptom resolution. The effect of administering omalizumab on the response to rhinovirus was most pronounced during the early/innate phase of the infection.

Contributions of Eosinophils to Human Health and Disease

The human eosinophil has long been thought to favorably influence innate mucosal immunity but at times has also been incriminated in disease pathophysiology. Research into eosinophil biology has uncovered a number of interesting contributions by eosinophils to health and disease. However, it appears that not all eosinophils from all species are created equal. It remains unclear, for example, exactly how having eosinophils benefits the human host when helminth infections in the developed world have become scarce. This review focuses on our current state of knowledge as it relates to human eosinophils. When information is lacking, we discuss lessons learned from mouse studies that may or may not directly apply to human biology and disease. It is an exciting time to be an "eosinophilosopher" because the use of biologic agents that selectively target eosinophils provides an unprecedented opportunity to define the contribution of this cell to eosinophil-associated human diseases.

Eosinophils capture viruses, a capacity that is defective in asthma

Background

Activated eosinophils cause major pathology in stable and exacerbating asthma; however, they can also display protective properties like an extracellular antiviral activity. Initial murine studies led us to further explore a potential intracellular antiviral activity by eosinophils.

Methods

To follow eosinophil‐virus interaction, respiratory syncytial virus (RSV) and influenza virus were labeled with a fluorescent lipophilic dye (DiD). Interactions with eosinophils were visualized by confocal microscopy, electron microscopy, and flow cytometry. Eosinophil activation was assessed by both flow cytometry and ELISA. In a separate study, eosinophils were depleted in asthma patients using anti‐IL‐5 (mepolizumab), followed by a challenge with rhinovirus‐16 (RV16).

Results

DiD‐RSV and DiD‐influenza rapidly adhered to human eosinophils and were internalized and inactivated (95% in ≤ 2 hours) as reflected by a reduced replication in epithelial cells. The capacity of eosinophils to capture virus was reduced up to 75% with increasing severity of asthma. Eosinophils were activated by virus in vitro and in vivo. In vivo this correlated with virus‐induced loss of asthma control.

Conclusions

This previously unrecognized and in asthma attenuated antiviral property provides a new perspective to eosinophils in asthma. This is indicative of an imbalance between protective and cytotoxic properties by eosinophils that may underlie asthma exacerbations.

Dual mechanism of action of T2 inhibitor therapies in virally induced exacerbations of asthma: evidence for a beneficial counter-regulation

Biological agents such as omalizumab and monoclonal antibodies (mAbs) that inhibit type 2 (T2) immunity significantly reduce exacerbations, which are mainly due to viral infections, when added to inhaled corticosteroids in patients with severe asthma. The mechanisms for the therapeutic benefit of T2 inhibitors in reducing virally induced exacerbations, however, remain to be fully elucidated. Pre-clinical and clinical evidence supports the existence of a close counter-regulation of the high-affinity IgE receptor and interferon (IFN) pathways, and a potential dual mechanism of action and therapeutic benefit for omalizumab and other T2 inhibitors that inhibit IgE activity, which may enhance the prevention and treatment of virally induced asthma exacerbations. Similar evidence regarding some novel T2 inhibitor therapies, including mAbs and small-molecule inhibitors, suggests that such a dual mechanism of action with enhancement of IFN production working through non-IgE pathways might also exist. The specific mechanisms for this dual effect could be related to the close counter-regulation between T2 and T1 immune pathways, and potential key underlying mechanisms are discussed. Further basic research and better understanding of these underlying counter-regulatory mechanisms could provide novel therapeutic targets for the prevention and treatment of virally induced asthma exacerbations, as well as T2- and non-T2-driven asthma. Future clinical research should examine the effects of T2 inhibitors on IFN responses and other T1 immune pathways, in addition to any effects on the frequency and severity of viral and other infections and related exacerbations in patients with asthma as a priority.

Eosinophils and Respiratory Viruses

Eosinophils have been mainly associated with parasitic infection and pathologies such as asthma. Some patients with asthma present a high number of eosinophils in their airways. Since respiratory viruses are associated with asthma exacerbations, several studies have evaluated the role of eosinophils against respiratory viruses. Eosinophils contain and produce molecules with antiviral activity, including RNases and reactive nitrogen species. They can also participate in adaptive immunity, serving as antigen-presenting cells. Eosinophil antiviral response has been demonstrated against some respiratory viruses in vitro and in vivo, including respiratory syncytial virus and influenza. Given the implication of respiratory viruses in asthma, the eosinophil antiviral role might be an important factor to consider in this pathology.