Immune Response, Diagnosis and Treatment of Allergic Bronchopulmonary Aspergillosis in Cystic Fibrosis Lung Disease

The Fungal and Bacterial Interface in the Respiratory Mycobiome with a Focus on Aspergillus spp

The heterogeneity of the lung microbiome and its alteration are prevalently seen among chronic lung diseases patients. However, studies to date have primarily focused on the bacterial microbiome in the lung rather than fungal composition, which might play an essential role in the mechanisms of several chronic lung diseases. It is now well established that Aspergillus spp. colonies may induce various unfavorable inflammatory responses. Furthermore, bacterial microbiomes such as Pseudomonas aeruginosa provide several mechanisms that inhibit or stimulate Aspergillus spp. life cycles. In this review, we highlighted fungal and bacterial microbiome interactions in the respiratory tract, with a focus on Aspergillus spp.

Impact of Fungal Spores on Asthma Prevalence and Hospitalization

Despite making up a significant proportion of airborne allergens, the relationship between fungal spores and asthma is not fully explored. Only 80 taxa of fungi have so far been observed to exacerbate respiratory presentations, with Cladosporium spp., Aspergillus spp., Penicillium spp., and Alternaria spp. found to comprise the predominant allergenic airborne spores. Fungal spores have been found in indoor environments, such as hospitals and housing due to poor ventilation. Meanwhile, outdoor fungal spores exhibit greater diversity, and higher abundance and have been associated with hospitalizations from acute asthma presentations. In addition, fungal spores may be the underlying, and perhaps the “missing link”, factor influencing the heightened rate of asthma presentations during epidemic thunderstorm asthma events. To improve our knowledge gap on fungal spores, airborne allergen monitoring must be improved to include not only dominant allergenic fungi but also provide real-time data to accurately and quickly warn the general public. Such data will help prevent future asthma exacerbations and thus save lives. In this review, we examine the health risks of prominent allergenic fungal taxa, the factors influencing spore dispersal and distribution, and why improvements should be made to current sampling methods for public health and wellbeing.

Allergic Bronchopulmonary Aspergillosis in Children with Cystic Fibrosis: An Update on the Newest Diagnostic Tools and Therapeutic Approaches

Cystic fibrosis (CF), the most common autosomal-recessive genetic disease in the Caucasian population, is characterized by frequent respiratory infections and progressive lung disease. Fungal species are commonly found in patients with CF, and among them, Aspergillus fumigatus is the most frequently isolated. While bacteria, particularly Pseudomonas aeruginosa, have a well-established negative effect on CF lung disease, the impact of fungal infections remains unclear. In patients with CF, inhalation of Aspergillus conidia can cause allergic bronchopulmonary aspergillosis (ABPA), a Th2-mediated lung disease that can contribute to disease progression. Clinical features, diagnostic criteria and treatment of ABPA are still a matter of debate. Given the consequences of a late ABPA diagnosis or the risk of ABPA overdiagnosis, it is imperative that the diagnostic criteria guidelines are reviewed and standardized. Along with traditional criteria, radiological features are emerging as tools for further classification as well as novel immunological tests. Corticosteroids, itraconazole and voriconazole continue to be the bedrock of ABPA therapy, but other molecules, such as posaconazole, vitamin D, recombinant INF-γ and Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) modulators, have been showing positive results. However, few studies have been conducted recruiting CF patients, and more research is needed to improve the prevention and the classification of clinical manifestations as well as to personalize treatment. Early recognition and early treatment of fungal infections may be fundamental to prevent progression of CF disease. The aim of this narrative review is to give an update on ABPA in children with CF.

Clinical relevance of Aspergillus fumigatus sensitization in cystic fibrosis

RATIONALE

The clinical relevance of sensitization to Aspergillus (A) fumigatus in cystic fibrosis (CF) is unclear. Some researchers propose that specific A fumigatus IgE is an innocent bystander, whereas others describe it as the major cause of TH-2-driven asthma-like disease.

OBJECTIVES

Lung function parameters in mild CF patients may be different in patients with and without A fumigatus sensitization. We aimed to ascertain whether allergen exposure to A fumigatus by bronchial allergen provocation (BAP) induces TH-2 inflammation comparable to an asthma-like disease.

METHODS

A total of 35 patients, aged 14.8 ± 8.5 years, and 20 healthy controls were investigated prospectively. The patients were divided into two groups: group 1 (n = 18): specific (s)IgE negative, and group 2 (n = 17): sIgE positive (≥0.7 KU/L) for A fumigatus. Lung function, exhaled NO, and induced sputum were analysed. All sensitized patients with an FEV1 > 75% (n = 13) underwent BAP with A fumigatus, and cell counts, and the expression of IL-5, IL-13, INF-γ, and IL-8 as well as transcription factors T-bet, GATA-3, and FoxP3, were measured.

RESULTS

Lung function parameters decreased significantly compared to controls, but not within the CF patient group. After BAP, 8 of 13 patients (61%) had a significant asthmatic response and increased eNO 24 hours later. In addition, marked TH-2-mediated inflammation involving eosinophils, IL-5, IL-13, and FoxP3 became apparent in induced sputum cells.

CONCLUSION

Our study demonstrated the clinical relevance of A fumigatus for the majority of sensitized CF patients. A distinct IgE/TH-2-dominated inflammation was found in induced sputum after A fumigatus exposure.

Fungal Pathogens in CF Airways: Leave or Treat?

Chronic airway infection plays an essential role in the progress of cystic fibrosis (CF) lung disease. In the past decades, mainly bacterial pathogens, such as Pseudomonas aeruginosa, have been the focus of researchers and clinicians. However, fungi are frequently detected in CF airways and there is an increasing body of evidence that fungal pathogens might play a role in CF lung disease. Several studies have shown an association of fungi, particularly Aspergillus fumigatus and Candida albicans, with the course of lung disease in CF patients. Mechanistically, in vitro and in vivo studies suggest that an impaired immune response to fungal pathogens in CF airways renders them more susceptible to fungi. However, it remains elusive whether fungi are actively involved in CF lung disease pathologies or whether they rather reflect a dysregulated airway colonization and act as microbial bystanders. A key issue for dissecting the role of fungi in CF lung disease is the distinction of dynamic fungal-host interaction entities, namely colonization, sensitization or infection. This review summarizes key findings on pathophysiological mechanisms and the clinical impact of fungi in CF lung disease.

Effect of allergic bronchopulmonary aspergillosis on FEV1 in children and adolescents with cystic fibrosis: a European Cystic Fibrosis Society Patient Registry analysis

OBJECTIVE

To evaluate the effect of allergic bronchopulmonary aspergillosis (ABPA) on FEV₁ percent predicted in children and adolescents with cystic fibrosis.

DESIGN

Longitudinal data analysis (2008-2010).

SETTING

Patients participating in the European Cystic Fibrosis Society Patient Registry.

PARTICIPANTS

3350 patients aged 6-17 years.

MAIN OUTCOME MEASURE

FEV₁ percent predicted was the main outcome measure (one measurement per year per child). To describe the effect of ABPA (main explanatory variable) on FEV₁ while controlling for other prognostic factors, a linear mixed effects regression model was applied.

RESULTS

In 2008, the mean (±SD) FEV₁ percent predicted was 78.6 (±20.6) in patients with ABPA (n=346) and 88 (±19.8) in those without ABPA (n=2806). After considering other variables, FEV₁ in subjects with ABPA on entry to the study was 1.47 percentage points lower than FEV₁ in patients of similar age without ABPA (p=0.003). There was no FEV₁ decline associated with ABPA over the subsequent study years as the interaction of ABPA with age was not significant (p>0.05). For patients aged 11.82 years (population mean age), poor body mass index had the greatest impact on FEV₁ in 2008, followed by high-risk genotype (two severe mutations), female gender, diabetes mellitus, chronic Pseudomonas aeruginosa infection and ABPA in descending order of effect size.

CONCLUSIONS

In contrast to the common clinical belief of ABPA having a serious impact on lung function, the difference in FEV₁ between young patients with and without the complication was found to be modest when the effect of other prognostic factors was considered.

Aspergillus fumigatus in the cystic fibrosis lung: pros and cons of azole therapy

Aspergillus fumigatus is the main fungus cultured in the airways of patients with cystic fibrosis (CF). Allergic bronchopulmonary aspergillosis occurs in ~10% of CF patients and is clearly associated with airway damage and lung function decline. The effects of A. fumigatus colonization in the absence of allergic bronchopulmonary aspergillosis are less well established. Retrospective clinical studies found associations of A. fumigatus-positive cultures with computed tomography scan abnormalities, greater risk of CF exacerbations and hospitalizations, and/or lung function decline. These findings were somewhat variable among studies and provided only circumstantial evidence for a role of A. fumigatus colonization in CF lung disease progression. The availability of a growing number of oral antifungal triazole drugs, together with the results of nonrandomized case series suggesting positive effects of azole therapies, makes it tempting to treat CF patients with these antifungal drugs. However, the only randomized controlled trial that has used itraconazole in CF patients showed no significant benefit. Because triazoles may have significant adverse effects and drug interactions, and because their prolonged use has been associated with the emergence of azole-resistant A. fumigatus isolates, it remains unclear whether or not CF patients benefit from azole therapy.

Allergic Bronchopulmonary Aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA), a progressive fungal allergic lung disease, is a common complication of asthma or cystic fibrosis. Although ABPA has been recognized since the 1950s, recent research has underscored the importance of Th2 immune deviation and granulocyte activation in its pathogenesis. There is also strong evidence of widespread under-diagnosis due to the complexity and lack of standardization of diagnostic criteria. Treatment has long focused on downregulation of the inflammatory response with prolonged courses of oral glucocorticosteroids, but more recently concerns with steroid toxicity and availability of new treatment modalities has led to trials of oral azoles, inhaled amphotericin, pulse intravenous steroids, and subcutaneously-injected anti-IgE monoclonal antibody omalizumab, all of which show evidence of efficacy and reduced toxicity.

Aspergillus infections in cystic fibrosis

Patients with cystic fibrosis (CF) suffer from chronic lung infection and airway inflammation. Respiratory failure secondary to chronic or recurrent infection remains the commonest cause of death and accounts for over 90% of mortality. Bacteria as Staphylococcus aureus, Pseudomonas aeruginosa and Burkholderia cepacia complex have been regarded the main CF pathogens and their role in progressive lung decline has been studied extensively. Little attention has been paid to the role of Aspergillus spp. and other filamentous fungi in the pathogenesis of non-ABPA (allergic bronchopulmonary aspergillosis) respiratory disease in CF, despite their frequent recovery in respiratory samples. It has become more apparent however, that Aspergillus spp. may play an important role in chronic lung disease in CF. Research delineating the underlying mechanisms of Aspergillus persistence and infection in the CF lung and its link to lung deterioration is lacking. This review summarizes the Aspergillus disease phenotypes observed in CF, discusses the role of CFTR (cystic fibrosis transmembrane conductance regulator)-protein in innate immune responses and new treatment modalities.

Exposure and Health Effects of Fungi on Humans

Fungi are ubiquitous microorganisms that are present in outdoor and indoor environments. Previous research has found relationships between environmental fungal exposures and human health effects. We reviewed recent articles focused on fungal exposure and dampness as risk factors for respiratory disease development, symptoms, and hypersensitivity. In particular, we reviewed the evidence suggesting that early exposure to dampness or fungi is associated with the development of asthma and increased asthma morbidity. Although outdoor exposure to high concentrations of spores can cause health effects such as asthma attacks in association with thunderstorms, most people appear to be relatively unaffected unless they are sensitized to specific genera. Indoor exposure and dampness, however, appears to be associated with an increased risk of developing asthma in young children and asthma morbidity in individuals who have asthma. These are important issues because they provide a rationale for interventions that might be considered for homes and buildings in which there is increased fungal exposure. In addition to rhinitis and asthma, fungus exposure is associated with a number of other illnesses including allergic bronchopulmonary mycoses, allergic fungal sinusitis, and hypersensitivity pneumonitis. Additional research is necessary to establish causality and evaluate interventions for fungal- and dampness-related health effects.

CXCR4+ granulocytes reflect fungal cystic fibrosis lung disease

Cystic fibrosis airways are frequently colonised with fungi. However, the interaction of these fungi with immune cells and the clinical relevance in cystic fibrosis lung disease are incompletely understood.We characterised granulocytes in airway fluids and peripheral blood from cystic fibrosis patients with and without fungal colonisation, non-cystic fibrosis disease controls and healthy control subjects cross-sectionally and longitudinally and correlated these findings with lung function parameters.Cystic fibrosis patients with chronic fungal colonisation by Aspergillus fumigatus were characterised by an accumulation of a distinct granulocyte subset, expressing the HIV coreceptor CXCR4. Percentages of airway CXCR4(+) granulocytes correlated with lung disease severity in patients with cystic fibrosis.These studies demonstrate that chronic fungal colonisation with A. fumigatus in cystic fibrosis patients is associated with CXCR4(+) airway granulocytes, which may serve as a potential biomarker and therapeutic target in fungal cystic fibrosis lung disease.

The potential impact of the pulmonary microbiome on immunopathogenesis of Aspergillus-related lung disease

Aspergillosis is an infection or allergic response caused by fungi of the genus Aspergillus. The most common forms of aspergillosis are allergic bronchopulmonary aspergillosis, chronic pulmonary aspergillosis, and invasive pulmonary aspergillosis. Aspergillus also plays an important role in fungal sensitized asthma. Humans inhale Aspergillus spores every day and when the host is immunocompromised, Aspergillus spp. may cause severe pulmonary disease. There is increasing evidence that the microbiome plays a significant role in immune regulation, chronic inflammatory diseases, metabolism, and other physiological processes, including recovery from the effects of antibiotic treatment. Bacterial microbiome mediated resistance mechanisms probably play a major role in limiting fungal colonization of the lungs, and may therefore prevent humans from contracting Aspergillus-related diseases. In this perspective, we review this emerging area of research and discuss the role of the microbiome in aspergillosis, role of Aspergillus in the microbiome, and the influence of the microbiome on anti-Aspergillus host defense and its role in preventing aspergillosis.

Efficacy and safety of nebulised amphotericin B (NAB) in severe asthma with fungal sensitisation (SAFS) and allergic bronchopulmonary aspergillosis (ABPA)

BACKGROUND AND RATIONALE

Antifungal therapy for severe asthma with fungal sensitisation (SAFS) and allergic bronchopulmonary aspergillosis (ABPA) remains poorly studied. We assessed the efficacy and safety of NAB as second and third line therapy in SAFS and ABPA.

METHODS

21 adult asthmatics with SAFS (n = 11) and ABPA (n = 10) who had either failed itraconazole (n = 8), voriconazole proceeded by itraconazole (n = 5) or developed adverse events (AEs) to either agent (n = 7) were treated with 10mg of NAB (Fungizone) twice daily. We audited clinical and immunological response, using the Asthma Quality of Life Questionnaire (AQLQ-J) scores, asthma control, FEV1, healthcare utilisation and IgE. Patients were followed up for 12 months.

RESULTS

Twenty-one patients were treated (SAFS, n = 11) and (ABPA, n = 10), M: F = 8:12, median age 65 years (range, 24-78). The median duration of therapy was 30 days (0-1825). Clinical benefit was observed in three (14.3 %) in which overall mean AQLQ-J score improved by + 2.9, mean FEV1 improved by 0.5 L and there was improvement in overall asthma control. Seven (33%) failed initial dose (bronchospasm). Eleven (52.4%) discontinued within 12 months of therapy due to delayed bronchospasm (n = 3, within 4 weeks), equipment problems (n = 2, within 4 weeks) and lack of clinical benefit (n = 4, within 16 weeks).

CONCLUSION

Our data suggest that the overall efficacy of NAB in this group of patients is poor and associated with bronchospasm. However, the excellent response in 3 patients, suggest it may be considered when other alternatives have been exhausted. Overcoming the initial bronchospasm may improve tolerability.