Fungal sensitization and positive fungal culture from sputum in children with asthma are associated with reduced lung function and acute asthma attacks respectively

Adjuvant-independent airway sensitization and infection mouse models leading to allergic asthma

Asthma is a chronic respiratory disease of global importance. Mouse models of allergic asthma have been instrumental in advancing research and novel therapeutic strategies for patients. The application of relevant allergens and physiological routes of exposure in such models has led to valuable insights into the complexities of asthma onset and development as well as key disease mechanisms. Furthermore, environmental microbial exposures and infections have been shown to play a fundamental part in asthma pathogenesis and alter disease outcome. In this review, we delve into physiological mouse models of allergic asthma and explore literature reports on most significant interplays between microbial infections and asthma development with relevance to human disease.

Aspergillus-sensitized asthma in children

BACKGROUND

Asthma is the most common chronic respiratory disease in childhood. Aspergillus fumigatus sensitivity may be involved in the pathogenesis of asthma by leading to different clinical presentations.

OBJECTIVE

To investigate the demographic, clinical, laboratory, and radiological characteristics of A. fumigatus sensitivity in childhood asthma and identify associated risk factors and diagnostic parameters.

METHODS

A total of 259 children with asthma were included in the study, 7 (2.7%) with allergic bronchopulmonary aspergillosis (ABPA), 84 (32.4%) with A. fumigatus-sensitized asthma (Af-SA), and 168 (64.9%) with A. fumigatus-unsensitized asthma (Af-UA).

RESULTS

Aspergillus sensitivity was associated with early asthma onset and longer asthma duration. Total IgE level and asthma severity are highest in ABPA and higher in Af-SA. Absolute eosinophil count was higher, and FEV1 was lower in Af-SA and ABPA. Aspergillus fumigatus was associated with greater odds of being male (odds ratio [OR], 2.45), having atopic dermatitis (OR, 3.159), Alternaria sensitivity (OR, 10.37), and longer asthma duration (OR, 1.266). The best cut-off values for detecting A. fumigatus positivity were 363.5 IU/mL for total IgE and 455 cells/μL for absolute eosinophil count. In Af-SA compared to Af-UA, centrilobular nodules and peribronchial thickening were more common, and the bronchoarterial ratio was higher.

CONCLUSIONS

Aspergillus sensitivity is a strong allergic stimulus in asthma, leading to laboratory, structural, clinical, and functional consequences. Af-SA is a distinct asthma endotype independent of ABPA that is characterized by increased risk of severe clinical presentations and impaired lung function.

Identification of allergens from Aspergillus fumigatus-Potential association with lung damage in asthma

BACKGROUND

Component-resolved diagnosis allows detection of IgE sensitization having the advantage of reproducibility and standardization compared to crude extracts. The main disadvantage of the traditional allergen identification methods, 1- or 2-dimensional western blotting and screening of expression cDNA libraries with patients' IgEs, is that the native structure of the protein is not necessarily maintained.

METHODS

We used a novel immunoprecipitation technique in combination with mass spectrometry to identify new allergens of Aspergillus fumigatus. Magnetic Dynabeads coupled with anti-human IgE antibodies were used to purify human serum IgE and subsequently allergens from A. fumigatus protein extract.

RESULTS

Of the 184 proteins detected by subsequent mass peptide fingerprinting, a subset of 13 were recombinantly expressed and purified. In a panel of 52 A. fumigatus-sensitized people with asthma, 23 non-fungal-sensitized asthmatics and 18 healthy individuals, only the former showed an IgE reaction by immunoblotting and/or ELISA. We discovered 11 proteins not yet described as A. fumigatus allergens, with fructose-bisphosphate aldolase class II (FBA2) (33%), NAD-dependent malate dehydrogenase (31%) and Cu/Zn superoxide dismutase (27%) being the most prevalent. With respect to these three allergens, native versus denatured protein assays indicated a better recognition of the native proteins. Seven of 11 allergens fulfilled the WHO/IUIS criteria and were accepted as new A. fumigatus allergens.

CONCLUSION

In conclusion, we introduce a straightforward method of allergen identification from complex allergenic sources such as A. fumigatus by immunoprecipitation combined with mass spectrometry, which has the advantage over traditional methods of identifying allergens by maintaining the structure of the proteins.

Revised ISHAM-ABPA working group clinical practice guidelines for diagnosing, classifying and treating allergic bronchopulmonary aspergillosis/mycoses

BACKGROUND

The International Society for Human and Animal Mycology (ISHAM) working group proposed recommendations for managing allergic bronchopulmonary aspergillosis (ABPA) a decade ago. There is a need to update these recommendations due to advances in diagnostics and therapeutics.

METHODS

An international expert group was convened to develop guidelines for managing ABPA (caused by Aspergillus spp.) and allergic bronchopulmonary mycosis (ABPM; caused by fungi other than Aspergillus spp.) in adults and children using a modified Delphi method (two online rounds and one in-person meeting). We defined consensus as ≥70% agreement or disagreement. The terms "recommend" and "suggest" are used when the consensus was ≥70% and <70%, respectively.

RESULTS

We recommend screening for A. fumigatus sensitisation using fungus-specific IgE in all newly diagnosed asthmatic adults at tertiary care but only difficult-to-treat asthmatic children. We recommend diagnosing ABPA in those with predisposing conditions or compatible clinico-radiological presentation, with a mandatory demonstration of fungal sensitisation and serum total IgE ≥500 IU·mL-1 and two of the following: fungal-specific IgG, peripheral blood eosinophilia or suggestive imaging. ABPM is considered in those with an ABPA-like presentation but normal A. fumigatus-IgE. Additionally, diagnosing ABPM requires repeated growth of the causative fungus from sputum. We do not routinely recommend treating asymptomatic ABPA patients. We recommend oral prednisolone or itraconazole monotherapy for treating acute ABPA (newly diagnosed or exacerbation), with prednisolone and itraconazole combination only for treating recurrent ABPA exacerbations. We have devised an objective multidimensional criterion to assess treatment response.

CONCLUSION

We have framed consensus guidelines for diagnosing, classifying and treating ABPA/M for patient care and research.

Allergic bronchopulmonary aspergillosis with atopic, nonatopic, and sans asthma-Factor analysis

BACKGROUND

Allergic bronchopulmonary aspergillosis (ABPA) develops in the presence or absence of asthma, either atopic or nonatopic. We have tried to explore the essential components in the pathogenesis of the disease, which are either consistent and variable according to the presence and type of asthma.

METHODS

Non-cystic fibrosis ABPA cases satisfying Asano's criteria were extracted from a prospective registry of ABPA and related diseases in Japan between 2013 and 2023. According to the type of preceding asthma, ABPA was classified into three groups: ABPA sans asthma (no preceding asthma), ABPA with atopic asthma, and ABPA with nonatopic asthma. Exploratory and confirmatory factor analyses were performed to identify the components that determined the clinical characteristics of ABPA.

RESULTS

Among 106 cases of ABPA, 25 patients (24%) had ABPA sans asthma, whereas 57 (54%) and 24 (23%) had ABPA with atopic and nonatopic asthma, respectively. Factor analysis identified three components: allergic, eosinophilic, and fungal. Patients with atopic asthma showed the highest scores for the allergic component (p < .001), defined by total and allergen-specific IgE titers and lung opacities, and the lowest scores for the fungal component defined by the presence of specific precipitin/IgG or positive culture for A. fumigatus. Eosinophilic components, including peripheral blood eosinophil counts and presence of mucus plugs/high attenuation mucus in the bronchi, were consistent among the three groups.

CONCLUSION

The eosinophilic component of ABPA is considered as the cardinal feature of ABPA regardless of the presence of preceding asthma or atopic predisposition.

Poorly controlled asthma - Easy wins and future prospects for addressing fungal allergy

Poorly controlled asthma is especially common in low resource countries. Aside from lack of access to, or poor technique with, inhaled beta-2 agonists and corticosteroids, the most problematic forms of asthma are frequently associated with both fungal allergy and exposure, especially in adults leading to more asthma exacerbations and worse asthma. The umbrella term 'fungal asthma' describes many disorders linked to fungal exposure and/or allergy to fungi. One fungal asthma endotype, ABPA, is usually marked by a very high IgE and its differential diagnosis is reviewed. Both ABPA and fungal bronchitis in bronchiectasis are marked by thick excess airway mucus production. Dermatophyte skin infection can worsen asthma and eradication of the skin infection improves asthma. Exposure to fungi in the workplace, home and schools, often in damp or water-damaged buildings worsens asthma, and remediation improves symptom control and reduces exacerbations. Antifungal therapy is beneficial for fungal asthma as demonstrated in nine of 13 randomised controlled studies, reducing symptoms, corticosteroid need and exacerbations while improving lung function. Other useful therapies include azithromycin and some biologics approved for the treatment of severe asthma. If all individuals with poorly controlled and severe asthma could be 'relieved' of their fungal allergy and infection through antifungal therapy without systemic corticosteroids, the health benefits would be enormous and relatively inexpensive, improving the long term health of over 20 million adults and many children. Antifungal therapy carries some toxicity, drug interactions and triazole resistance risks, and data are incomplete. Here we summarise what is known and what remains uncertain about this complex topic.

Aspergillus Sensitization and Allergic Bronchopulmonary Aspergillosis in Asthmatic Children: A Systematic Review and Meta-Analysis

Background: The prevalence of aspergillus sensitization (AS) and allergic bronchopulmonary aspergillosis (ABPA) in asthmatic children remains unclear. Objective: To systematically review the literature to estimate the prevalence of AS and ABPA in children with bronchial asthma. Methods: We searched the PubMed and Embase databases for studies reporting the prevalence of AS or ABPA in pediatric asthma. The primary outcome was to assess the prevalence of AS, while the secondary outcome was to evaluate the prevalence of ABPA. We pooled the prevalence estimates using a random effects model. We also calculated the heterogeneity and publication bias. Results: Of the 11,695 records retrieved, 16 studies with 2468 asthmatic children met the inclusion criteria. Most studies were published from tertiary centers. The pooled prevalence of AS in asthma (15 studies; 2361 subjects) was 16.1% (95% confidence intervals [CI], 9.3-24.3). The prevalence of AS was significantly higher in prospective studies, studies from India, and those from developing countries. The pooled prevalence of ABPA in asthma (5 studies; 505 children) was 9.9% (95% CI, 0.81-27.6). There was significant heterogeneity and publication bias for both outcomes. Conclusions: We found a high prevalence of AS and ABPA in asthmatic children. There is a need for community-based studies from different ethnicities using a standard methodology to ascertain the true prevalence of AS and ABPA in pediatric asthma.

Severe Fungal Asthma: A Role for Biologics and Inhaled Antifungals

Allergic asthma has traditionally been treated with inhaled and systemic glucocorticosteroids. A continuum of allergic fungal airways disease associated with Aspergillus fumigatus colonization and/or atopic immune responses that encompasses fungal asthma, severe asthma with fungal sensitization and allergic bronchopulmonary aspergillosis is now recognized along a phenotypic severity spectrum of T2-high immune deviation lung disease. Oral triazoles have shown clinical, anti-inflammatory and microbiologic efficacy in this setting; in the future inhaled antifungals may improve the therapeutic index. Humanized monoclonal antibody biologic agents targeting T2-high disease also show efficacy and promise of improved control in difficult cases. Developments in these areas are highlighted in this overview.

Fungal exposome, human health, and unmet needs: A 2022 update with special focus on allergy

Humans inhale, ingest, and touch thousands of fungi each day. The ubiquity and diversity of the fungal kingdom, reflected by its complex taxonomy, are in sharp contrast with our scarce knowledge about its distribution, pathogenic effects, and effective interventions at the environmental and individual levels. Here, we present an overview of salient features of fungi as permanent players of the human exposome and key determinants of human health, through the lens of fungal allergy and other fungal hypersensitivity reactions. Improved understanding of the fungal exposome sheds new light on the epidemiology of fungal-related hypersensitivity diseases, their immunological substratum, the currently available methods, and biomarkers for environmental and medical fungi. Unmet needs are described and potential approaches are highlighted as perspectives.

Aerosolization of fungal spores in indoor environments

Fungi in indoor environments can cause adverse health effects through inhalation and epidermal exposure. The risk of fungal exposure originates from the aerosolization of fungal spores. However, spore aerosolization is still not well understood. This paper provides a review of indoor fungal contamination, especially the aerosolization of fungal spores. We attempted to summarize what is known today and to identify what more information is needed to predict the aerosolization of fungal spores. This paper first reviews fungal contamination in indoor environments and HVAC systems. The detachment of fungal spores from colonies and the spore aerosolization principle are then summarized. Based on the above discussion, prediction methods for spore aerosolization are discussed. This review further clarifies the current situation and future efforts required to accurately predict spore aerosolization. This information is useful for forecasting and controlling the aerosolization of fungal spores.

Sputum biomarkers during acute severe asthma attacks in children-a case-control study

AIM

To study sputum mediator profiles pattern in children with acute severe asthma, compared with stable asthma and healthy controls. The mechanisms of acute severe asthma attacks, such as biomarkers cascades and immunological responses, are poorly understood.

METHODS

We conducted a prospective observational case-control study of children aged 5 to 17 years, who presented to hospital with an asthma attack. Children with stable asthma were recruited during outpatient asthma clinic visits. Control children without an asthma diagnosis were recruited from surgical wards. Sputum mediator profiles were measured, and sputum leukocyte differential cell counts were generated.

RESULTS

Sputum data were available in 48 children (acute asthma; n = 18, stable asthma; n = 17, healthy controls; n = 13). Acute-phase biomarkers and neutrophil attractants such as IL-6 and its receptor, IL-8 and cytokines linked with bacterial signals, including TNF-R1 and TNF-R2, were elevated in asthma attacks versus stable asthma and healthy controls. T-cell attractant cytokines, associated with viral infections, such as CCL-5, CXCL-10 and CXCL-11, and CXCL-9 (secreted from eosinophils after a viral trigger) were also raised.

CONCLUSION

Mediator profiles consistent with bacterial and viral respiratory infections, and T2 inflammation markers co-exist in the sputum of children with acute severe asthma attacks.

Do not forget asthma comorbidities in pediatric severe asthma!

Asthma is the most common chronic respiratory disease in childhood. The long-term goals in managing asthma aim to control symptoms and prevent exacerbations, as well as to reduce side effects of therapy and mortality disease-related. Most of patients have mild to moderate asthma and respond well to standard therapies. However, a minor proportion of children with asthma has severe disease that remains uncontrolled despite optimal adherence to prescribed therapy and treatment of contributory factors, including trigger exposures and comorbidities, which can mimic or worsen asthma and contribute to exacerbations and poor quality of life. Evaluation of comorbidities is fundamental to optimize the management of the disease in a subgroup of patients with poor responder asthma. The overall aim of this article is to describe characteristics of main pediatric severe asthma comorbidities reported in literature, giving clinicians tools to recognize and manage properly these conditions.

The Clinical Implications of Aspergillus Fumigatus Sensitization in Difficult-To-Treat Asthma Patients

BACKGROUND

Fungal sensitivity has been associated with severe asthma outcomes. However, the clinical implication of Aspergillus fumigatus sensitization in difficult-to-treat (or difficult) asthma is unclear.

OBJECTIVES

To characterize the clinical implications of A fumigatus sensitization in a large difficult asthma cohort.

METHODS

Participants who underwent both skin prick and specific IgE testing to A fumigatus (n = 318) from the longitudinal real-life Wessex AsThma CoHort of difficult asthma, United Kingdom, were characterized by A fumigatus sensitization (either positive skin prick test result or specific IgE) and allergic bronchopulmonary aspergillosis status using clinical/pathophysiological disease measures.

RESULTS

A fumigatus sensitization was found in 23.9% (76 of 318) of patients with difficult asthma. Compared with A fumigatus nonsensitized subjects, those with sensitization were significantly more often male (50% vs 31%), older (58 years) with longer asthma duration (33 years), higher maintenance oral corticosteroid (39.7%) and asthma biologic use (27.6%), raised current/maximum log₁₀ total IgE+1 (2.43/2.72 IU/L), worse prebronchodilator airflow obstruction (FEV₁ 62.2% predicted, FEV₁/forced vital capacity 61.2%, forced expiratory flow between 25% and 75% exhalation 30.9% predicted), and frequent radiological bronchiectasis (40%), but had less psychophysiologic comorbidities. Allergic bronchopulmonary aspergillosis diagnosis was associated with higher treatment needs and stronger eosinophilic signals. Factors independently associated with A fumigatus sensitization in difficult asthma included maintenance oral corticosteroid use (odds ratio [OR], 3.34) and maximum log₁₀ total IgE+1 (OR, 4.30), whereas for allergic bronchopulmonary aspergillosis included maintenance oral corticosteroid use (OR, 6.98), maximum log₁₀ total IgE+1 (OR, 4.65), and radiological bronchiectasis (OR, 4.08).

CONCLUSIONS

A fumigatus sensitization in difficult asthma identifies a more severe form of airways disease associated with greater morbidity, treatment need, and airways dysfunction/damage, but fewer psychophysiologic comorbidities. Screening of A fumigatus status should be an early element in the comprehensive assessment of patients with difficult asthma.

Allergic fungal airways disease (AFAD): an under-recognised asthma endotype

The term allergic fungal airways disease has a liberal definition based on IgE sensitisation to thermotolerant fungi and evidence of fungal-related lung damage. It arose from a body of work looking into the role of fungi in asthma. Historically fungi were considered a rare complication of asthma, exemplified by allergic bronchopulmonary aspergillosis; however, there is a significant proportion of individuals with Aspergillus fumigatus sensitisation who do not meet these criteria, who are at high risk for the development of lung damage. The fungi that play a role in asthma can be divided into two groups; those that can grow at body temperature referred to as thermotolerant, which are capable of both infection and allergy, and those that cannot but can still act as allergens in IgE sensitised individuals. Sensitisation to thermotolerant filamentous fungi (Aspergillus and Penicillium), and not non-thermotolerant fungi (Alternaria and Cladosporium) is associated with lower lung function and radiological abnormalities (bronchiectasis, tree-in-bud, fleeting shadows, collapse/consolidation and fibrosis). For antifungals to play a role in treatment, the focus should be on fungi capable of growing in the airways thereby causing a persistent chronic allergenic stimulus and releasing tissue damaging proteases and other enzymes which may disrupt the airway epithelial barrier and cause mucosal damage and airway remodelling. All patients with IgE sensitisation to thermotolerant fungi in the context of asthma and other airway disease are at risk of progressive lung damage, and as such should be monitored closely.

New Perspectives in the Diagnosis and Management of Allergic Fungal Airway Disease

Allergy to airway-colonising, thermotolerant, filamentous fungi represents a distinct eosinophilic endotype of often severe lung disease. This endotype, which particularly affects adult asthma, but also complicates other airway diseases and sometimes occurs de novo, has a heterogeneous presentation ranging from severe eosinophilic asthma to lobar collapse. Its hallmark is lung damage, characterised by fixed airflow obstruction (FAO), bronchiectasis and lung fibrosis. It has a number of monikers including severe asthma with fungal sensitisation (SAFS) and allergic bronchopulmonary aspergillosis/mycosis (ABPA/M), but these exclusive terms constitute only sub-sets of the condition. In order to capture the full extent of the syndrome we prefer the inclusive term allergic fungal airway disease (AFAD), the criteria for which are IgE sensitisation to relevant fungi in association with airway disease. The primary fungus involved is Aspergillus fumigatus, but a number of other thermotolerant species from several genera have been implicated. The unifying mechanism involves germination of inhaled fungal spores in the lung in the context of IgE sensitisation, leading to a persistent and vigorous eosinophilic inflammatory response in association with release of fungal proteases. Most allergenic fungi, including Alternaria and Cladosporium species, are not thermotolerant and cannot germinate in the airways so only act as aeroallergens and do not cause AFAD. Studies of the airway mycobiome have shown that A. fumigatus colonises the normal as much as the asthmatic airway, suggesting it is the tendency to become IgE-sensitised that is the critical triggering factor for AFAD rather than colonisation per se. Treatment is aimed at preventing exacerbations with glucocorticoids and increasingly by the use of anti-T2 biological therapies. Anti-fungal therapy has a limited place in management, but is an effective treatment for fungal bronchitis which complicates AFAD in about 10% of cases.

Precision Medicine for Paediatric Severe Asthma: Current Status and Future Direction

Asthma is a heterogeneous disease, characterised by different phenotypes and endotypes. Precision medicine in asthma refers to the implementation of a targeted therapy for each individual child, based on the identification of treatable traits, including environmental, immunological and genetic factors. Severe asthma in children is associated with increased hospitalisation rates, a lower quality of life, increased healthcare costs and an increased mortality. In the era of new molecular biologics treatments, it is essential to improve deep phenotyping of children with severe asthma in order to deliver the most effective treatment to each individual child. In this review, we discuss the personalised approach to the assessment and management of severe asthma. We explore the indications and use of the currently licensed biologics, as well as the potential of other emerging treatments.