Cystic fibrosis transmembrane conductance regulator regulates epithelial cell response to Aspergillus and resultant pulmonary inflammation

Aspergillus in Children and Young People with Cystic Fibrosis: A Narrative Review

Cystic fibrosis is a severe, inherited, life-limiting disorder, and over half of those living with CF are children. Persistent airway infection and inflammation, resulting in progressive lung function decline, is the hallmark of this disorder. Aspergillus colonization and infection is a well-known complication in people with CF and can evolve in a range of Aspergillus disease phenotypes, including Aspergillus bronchitis, fungal sensitization, and allergic bronchopulmonary aspergillosis (ABPA). Management strategies for children with CF are primarily aimed at preventing lung damage and lung function decline caused by bacterial infections. The role of Aspergillus infections is less understood, especially during childhood, and therefore evidence-based diagnostic and treatment guidelines are lacking. This narrative review summarizes our current understanding of the impact of Aspergillus on the airways of children and young people with CF.

Increased NFAT and NFκB signalling contribute to the hyperinflammatory phenotype in response to Aspergillus fumigatus in a mouse model of cystic fibrosis

Aspergillus fumigatus (Af) is a major mould pathogen found ubiquitously in the air. It commonly infects the airways of people with cystic fibrosis (CF) leading to Aspergillus bronchitis or allergic bronchopulmonary aspergillosis. Resident alveolar macrophages and recruited neutrophils are important first lines of defence for clearance of Af in the lung. However, their contribution to the inflammatory phenotype in CF during Af infection is not well understood. Here, utilising CFTR deficient mice we describe a hyperinflammatory phenotype in both acute and allergic murine models of pulmonary aspergillosis. We show that during aspergillosis, CFTR deficiency leads to increased alveolar macrophage death and persistent inflammation of the airways in CF, accompanied by impaired fungal control. Utilising CFTR deficient murine cells and primary human CF cells we show that at a cellular level there is increased activation of NFκB and NFAT in response to Af which, as in in vivo models, is associated with increased cell death and reduced fungal control. Taken together, these studies indicate that CFTR deficiency promotes increased activation of inflammatory pathways, the induction of macrophage cell death and reduced fungal control contributing to the hyper-inflammatory of pulmonary aspergillosis phenotypes in CF.

Epithelial uptake leads to fungal killing in vivo and is aberrant in COPD-derived epithelial cells

Hundreds of spores of Aspergillus fumigatus (Af) are inhaled daily by human beings, representing a constant, possibly fatal, threat to respiratory health. The small size of Af spores suggests that interactions with alveolar epithelial cells (AECs) are frequent; thus, we hypothesized that spore uptake by AECs is important for driving fungal killing and susceptibility to Aspergillus-related disease. Using single-cell approaches to measure spore uptake and its outcomes in vivo, we demonstrate that Af spores are internalized and killed by AECs during whole-animal infection. Moreover, comparative analysis of primary human AECs from healthy and chronic obstructive pulmonary disease (COPD) donors revealed significant alterations in the uptake and killing of spores in COPD-derived AECs. We conclude that AECs contribute to the killing of Af spores and that dysregulation of curative AEC responses in COPD may represent a driver of Aspergillus-related diseases.

Pulmonary Aspergillosis in People with Cystic Fibrosis

In the last decade, fungal respiratory diseases have been increasingly investigated for their impact on the clinical course of people with cystic fibrosis (CF), with a particular focus on infections caused by Aspergillus spp. The most common organisms from this genus detected from respiratory cultures are Aspergillus fumigatus and Aspergillus terreus, followed by Aspergillus flavus, Aspergillus niger, and Aspergillus nidulans. These species have been identified to be both chronic colonizers and sources of active infection and may negatively impact lung function in people with CF. This review article discusses definitions of aspergillosis, challenges in clinical practice, and current literature available for laboratory findings, clinical diagnosis, and treatment options for pulmonary diseases caused by Aspergillus spp. in people with CF.

Impact of lumacaftor/ivacaftor on the bacterial and fungal respiratory pathogens in cystic fibrosis: a prospective multicenter cohort study in Sweden

BACKGROUND

A significant decline in pulmonary exacerbation rates has been reported in CF patients homozygous for F508del treated with lumacaftor/ivacaftor. However, it is still unclear whether this reduction reflects a diminished microbiological burden.

OBJECTIVES

The aim of this study was to determine the impact of lumacaftor/ivacaftor on the bacterial and fungal burden.

DESIGN

The study is a prospective multicenter cohort study including 132 CF patients homozygous for F508del treated with lumacaftor/ivacaftor.

METHODS

Clinical parameters as well as bacterial and fungal outcomes 1 year after initiation of lumacaftor/ivacaftor were compared to data from 2 years prior to initiation of the treatment. Changes in the slope of the outcomes before and after the onset of treatment were assessed.

RESULTS

Lung function measured as ppFEV1 (p < 0.001), body mass index (BMI) in adults (p < 0.001), and BMI z-score in children (p = 0.007) were improved after initiation of lumacaftor/ivacaftor. In addition, the slope of the prevalence of Streptococcus pneumoniae (p = 0.007) and Stenotrophomonas maltophilia (p < 0.001) shifted from positive to negative, that is, became less prevalent, 1 year after treatment, while the slope for Candida albicans (p = 0.009), Penicillium spp (p = 0.026), and Scedosporium apiospermum (p < 0.001) shifted from negative to positive.

CONCLUSION

The current study showed a significant improvement in clinical parameters and a reduction of some of CF respiratory microorganisms 1 year after starting with lumacaftor/ivacaftor. However, no significant changes were observed for Pseudomonas aeruginosa, Staphylococcus aureus, or Aspergillus fumigatus, key pathogens in the CF context.

Pathogenicity and virulence of Aspergillus fumigatus

Pulmonary infections caused by the mould pathogen Aspergillus fumigatus are a major cause of morbidity and mortality globally. Compromised lung defences arising from immunosuppression, chronic respiratory conditions or more recently, concomitant viral or bacterial pulmonary infections are recognised risks factors for the development of pulmonary aspergillosis. In this review, we will summarise our current knowledge of the mechanistic basis of pulmonary aspergillosis with a focus on emerging at-risk populations.

Protective role of CFTR during fungal infection of cystic fibrosis bronchial epithelial cells with Aspergillus fumigatus

Lung infection with the fungus Aspergillus fumigatus (Af) is a common complication in cystic fibrosis (CF) and is associated with loss of pulmonary function. We established a fungal epithelial co-culture model to examine the impact of Af infection on CF bronchial epithelial barrier function using Af strains 10AF and AF293-GFP, and the CFBE41o- cell line homozygous for the F508del mutation with (CF+CFTR) and without (CF) normal CFTR expression. Following exposure of the epithelial surface to Af conidia, formation of germlings (early stages of fungal growth) was detected after 9-12 hours and hyphae (mature fungal growth) after 12-24 hours. During fungal morphogenesis, bronchial epithelial cells showed signs of damage including rounding, and partial detachment after 24 hours. Fluorescently labeled conidia were internalized after 6 hours and more internalized conidia were observed in CF compared to CF+CFTR cells. Infection of the apical surface with 10AF conidia, germlings, or hyphae was performed to determine growth stage-specific effects on tight junction protein zona occludens protein 1 (ZO-1) expression and transepithelial electrical resistance (TER). In response to infection with conidia or germlings, epithelial barrier function degraded time-dependently (based on ZO-1 immunofluorescence and TER) with a delayed onset in CF+CFTR cell monolayers and required viable fungi and apical application. Infection with hyphae caused an earlier onset and faster rate of decline in TER compared to conidia and germlings. Gliotoxin, a major Af virulence factor, caused a rapid decline in TER and induced a transient chloride secretory response in CF+CFTR but not CF cells. Our findings suggest growth and internalization of Af result in deleterious effects on bronchial epithelial barrier function that occurred more rapidly in the absence of CFTR. Bronchial epithelial barrier breakdown was time-dependent and morphotype-specific and mimicked by acute administration of gliotoxin. Our study also suggests a protective role for CFTR by turning on CFTR-dependent chloride transport in response to gliotoxin, a mechanism that will support mucociliary clearance, and could delay the loss of epithelial integrity during fungal development in vivo.

Allergic bronchopulmonary aspergillosis: A multidisciplinary review

Allergic bronchopulmonary aspergillosis (ABPA) is a rare disease characterized by a complex allergic inflammatory reaction of airways against Aspergillus affecting patients with chronic respiratory diseases (asthma, cystic fibrosis). Exacerbation is often the way to diagnose ABPA and marks its evolution by its recurrent character leading to cortico-requirement or long-term antifungal treatment. Early diagnosis allows treatment of ABPA at an initial stage, preventing recurrence of exacerbations and long-term complications, mainly represented by bronchiectasis. This review of the literature aims to present the current state of the art in terms of diagnosis and treatment of ABPA from a multidisciplinary perspective. As there is no clinical, biological nor radiological specific sign, diagnostic criteria are regularly revised. They are mainly based on the elevation of total and specific IgE against Aspergillus fumigatus and the presence of suggestive CT abnormalities such as mucoid impaction and consolidations. ABPA management includes eviction of mold and pharmacological therapy. Exacerbations are treated in first line with a moderate dose of oral corticosteroids. Azole antifungal agents represent an alternative for the treatment of exacerbations and are the preferential strategy to reduce the future risk of exacerbations and for corticosteroids sparing. Asthma biologics may be of interest; however, their place remains to be determined. Avoiding complications of ABPA while limiting the side effects of systemic drugs remains a major challenge of ABPA management. Several drugs, including new antifungals and asthma biologics, are currently being tested and may be useful in the future.

The Clinical Association between Aspergillus fumigatus and Respiratory Outcomes in Adolescents and Adults with Cystic Fibrosis

Rationale: The clinical significance of Aspergillus fumigatus (Af) detection in the absence of allergic bronchopulmonary aspergillosis in cystic fibrosis (CF) airways remains unclear. Yet, some clinicians initiate antifungal therapy for Af-positive respiratory cultures out of concern for infection in people with CF. Objectives: To determine the association between the presence of Af and respiratory outcomes in individuals with CF. Methods: We conducted a prospective longitudinal cohort study of 206 adults and adolescents (age 14 yr and older) with CF and collected sputum for selective fungus culture. We assessed clinical outcome measurements, including patient-reported outcomes (measured by the Cystic Fibrosis Questionnaire-Revised), spirometry, and number of pulmonary exacerbations (PEx) for a 1-year period. We used mixed-effects linear models to determine the association between positive Af culture results, defined as Af detection in sputum culture at the study visit, with both respiratory domain score and forced expiratory volume in 1 second (FEV1) percent predicted, adjusted for confounders. Mixed-effects Poisson regression models were employed to examine the association between positive Af culture results and PEx events. We explored the association between Af history, defined as Af detection at baseline or within 2 years of enrollment, and respiratory outcomes. Results: Af prevalence was 10.3% (95% confidence interval [CI], 6.8, 15.7) at baseline. Forty-eight (23.3%; 95% CI, 17.7, 29.7) participants had at least one Af-positive culture result during the study period. Positive Af culture result was not associated with lower respiratory domain score. However, Af history was associated with a 6.48-point lower respiratory domain score, reflective of worse respiratory quality of life (95% CI, -11.96, -0.99; P = 0.02). Positive Af culture result was associated with a 2.54% lower FEV1 percent predicted (95% CI, -4.64, -0.44; P = 0.02) and a 1.71-fold increase in severe PEx incidence (95% CI, 1.05, 2.76; P = 0.03). Conclusions: Positive Af culture result was not associated with lower patient-reported, respiratory-related quality of life. Yet, positive Af culture result was associated with both lower FEV1 percent predicted and increased frequency of severe PEx warranting intravenous antibiotics in adolescents and adults with CF. Future studies are required to better understand the direct role of Af in lung disease progression in CF.

A case-control study of the effects of Aspergillus clinical phenotypes on pulmonary functions in patients with cystic fibrosis

INTRODUCTION

There are no precise data about the effect of Aspergillus infection on lung function other than allergic bronchopulmonary aspergillosis (ABPA) in patients with cystic fibrosis (pwCF). Here, we aimed to determine clinical phenotypes caused by Aspergillus spp. using laboratory and immunologic parameters and to compare Aspergillus phenotypes in terms of pulmonary function tests (PFT) prospectively.

METHODS

Twenty-three pwCF who had Aspergillus isolation from respiratory cultures in the last year (case group) and 20 pwCF without Aspergillus isolation in sputum (control group) were included. Aspergillus immunoglobulin (Ig)-G, Aspergillus IgE, Aspergillus polymerase chain reaction (PCR), galactomannan, total IgE from blood samples, and Aspergillus PCR and galactomannan from sputum, and skin prick test reactivity to Aspergillus antigen were used to distinguish different Aspergillus phenotypes. Pulmonary functions and frequency of pulmonary exacerbations were evaluated during a 1-year follow-up.

RESULTS

Of 23 pwCF, 11 (47.8%) had Aspergillus colonization, nine (39.1%) had Aspergillus bronchitis, and three (13%) had ABPA. Aspergillus infection was not associated with worse z-scores of forced expiratory volume in the first second (FEV1) (p = 0.612), forced vital capacity  (p = 0.939), and the median FEV 1% decline (0.0%/year vs. -4.7%/year, p = 0.626). The frequency of pulmonary exacerbations in the Aspergillus infected and noninfected groups was similar.

CONCLUSION

Although Aspergillus spp. Isolation in pwCF was not associated with decreased lung function, a further decline was seen in the ABPA subgroup, and frequent pulmonary exacerbations during the 1-year follow-up.

Of Mycelium and Men: Inherent Human Susceptibility to Fungal Diseases

In medical mycology, the main context of disease is iatrogenic-based disease. However, historically, and occasionally, even today, fungal diseases affect humans with no obvious risk factors, sometimes in a spectacular fashion. The field of “inborn errors of immunity” (IEI) has deduced at least some of these previously enigmatic cases; accordingly, the discovery of single-gene disorders with penetrant clinical effects and their immunologic dissection have provided a framework with which to understand some of the key pathways mediating human susceptibility to mycoses. By extension, they have also enabled the identification of naturally occurring auto-antibodies to cytokines that phenocopy such susceptibility. This review provides a comprehensive update of IEI and autoantibodies that inherently predispose humans to various fungal diseases.

Frequencies of pathogenic CFTR variants in Greek cystic fibrosis patients with allergic bronchopulmonary aspergillosis and Aspergillus fumigatus chronic colonization: A retrospective cohort study

INTRODUCTION

The clinical spectrum of Aspergillus fumigatus diseases in cystic fibrosis (CF) patients, including allergic bronchopulmonary aspergillosis (ABPA) and Aspergillus fumigatus chronic colonization, has recently gained attention due to its association with the progression of lung disease. Our aim was to examine whether there is a difference on pathogenic variant frequencies of the CFTR gene between CF patients with ABPA and those with A. fumigatus chronic colonization.

MATERIAL AND METHODS

Greek CF patients diagnosed with ABPA and/or A. fumigatus chronic colonization were grouped according to their CFTR genotype. Patients with "minimal" CFTR function were defined as carrying a combination of class I or II pathogenic variants, while patients with "residual" function as carrying at least one class III, IV, V or VI pathogenic variant.

RESULTS

Fifty-four CF patients were included and all except one were defined as having "minimal" CFTR function. Among the 108 CFTR alleles, 69 (63.9%) of pathogenic variants belonged to class II, and 32 (29.6%) to class I. Five patients had a history of both ABPA and A. fumigatus chronic colonization. No significant difference was detected among patients diagnosed only with ABPA (n = 29) and those who had only a positive history of A. fumigatus chronic colonization (n = 20). The median age of ABPA diagnosis was significantly lower than the median age of A. fumigatus chronic colonization (P = 0.011), while no significant difference was detected on median FEV₁% predicted.

DISCUSSION

No significant differences were detected in the type of CFTR pathogenic variants among patients with ABPA and those with A. fumigatus colonization. Similar studies should be performed in larger CF populations of different ethnic origin to further confirm our results.

Upper respiratory tract mycobiome alterations in different kinds of pulmonary disease

Introduction

The human respiratory tract is considered to be a polymicrobial niche, and an imbalance in the microorganism composition is normally associated with several respiratory diseases. In addition to the well-studied bacteriome, the existence of fungal species in the respiratory tract has drawn increasing attention and has been suggested to have a significant clinical impact. However, the understanding of the respiratory fungal microbiota (mycobiome) in pulmonary diseases is still insufficient.

Methods

In this study, we investigated the fungal community composition of oropharynx swab (OS) samples from patients with five kinds of pulmonary disease, including interstitial lung disease (ILD), bacterial pneumonia (BP), fungal pneumonia (FP), asthma (AS) and lung cancer (LC), and compared them with healthy controls (HCs), based on high-throughput sequencing of the amplified fungal internal transcribed spacer (ITS) region.

Results

The results showed significant differences in fungal composition and abundance between disease groups and HCs. Malassezia was the most significant genus, which was much more abundant in pulmonary diseases than in the control. In addition, many common taxa were shared among different disease groups, but differences in taxa abundance and specific species in distinct disease groups were also observed. Based on linear discriminant analysis effect size (LefSe), each group had its characteristic species. Furthermore, some species showed a significant correlation with the patient clinical characteristics.

Discussion

Our study deepened our understanding of the respiratory tract mycobiome in some diseases that are less studied and identified the commonalities and differences among different kinds of pulmonary disease. These results would provide the solid basis for further investigation of the association between the mycobiome and pathogenicity of pulmonary diseases.

Could the Lung Be a Gateway for Amphotericin B to Attack the Army of Fungi?

Fungal diseases are a significant cause of morbidity and mortality worldwide, primarily affecting immunocompromised patients. Aspergillus, Pneumocystis, and Cryptococcus are opportunistic fungi and may cause severe lung disease. They can develop mechanisms to evade the host immune system and colonize or cause lung disease. Current fungal infection treatments constitute a few classes of antifungal drugs with significant fungi resistance development. Amphotericin B (AmB) has a broad-spectrum antifungal effect with a low incidence of resistance. However, AmB is a highly lipophilic antifungal with low solubility and permeability and is unstable in light, heat, and oxygen. Due to the difficulty of achieving adequate concentrations of AmB in the lung by intravenous administration and seeking to minimize adverse effects, nebulized AmB has been used. The pulmonary pathway has advantages such as its rapid onset of action, low metabolic activity at the site of action, ability to avoid first-pass hepatic metabolism, lower risk of adverse effects, and thin thickness of the alveolar epithelium. This paper presented different strategies for pulmonary AmB delivery, detailing the potential of nanoformulation and hoping to foster research in the field. Our finds indicate that despite an optimistic scenario for the pulmonary formulation of AmB based on the encouraging results discussed here, there is still no product registration on the FDA nor any clinical trial undergoing ClinicalTrial.gov.

Novel Insights into Aspergillus fumigatus Pathogenesis and Host Response from State-of-the-Art Imaging of Host-Pathogen Interactions during Infection

Aspergillus fumigatus spores initiate more than 3,000,000 chronic and 300,000 invasive diseases annually, worldwide. Depending on the immune status of the host, inhalation of these spores can lead to a broad spectrum of disease, including invasive aspergillosis, which carries a 50% mortality rate overall; however, this mortality rate increases substantially if the infection is caused by azole-resistant strains or diagnosis is delayed or missed. Increasing resistance to existing antifungal treatments is becoming a major concern; for example, resistance to azoles (the first-line available oral drug against Aspergillus species) has risen by 40% since 2006. Despite high morbidity and mortality, the lack of an in-depth understanding of A. fumigatus pathogenesis and host response has hampered the development of novel therapeutic strategies for the clinical management of fungal infections. Recent advances in sample preparation, infection models and imaging techniques applied in vivo have addressed important gaps in fungal research, whilst questioning existing paradigms. This review highlights the successes and further potential of these recent technologies in understanding the host-pathogen interactions that lead to aspergillosis.

Aspergillus-related lung disease in people with cystic fibrosis: can imaging help us to diagnose disease?

In people with cystic fibrosis (PwCF), viscous sputum and dysfunction of the mucociliary escalator leads to early and chronic infections. The prevalence of Aspergillus fumigatus in sputum is high in PwCF and the contribution of A. fumigatus to the progression of structural lung disease has been reported. However, overall, relatively little is known about the contribution of A. fumigatus to CF lung disease. More knowledge is needed to aid clinical decisions on whether to start antifungal treatment. In this review, we give an overview of A. fumigatus colonisation and infection in PwCF and the different types of pulmonary disease caused by it. Furthermore, we discuss the current evidence for structural lung damage associated with A. fumigatus in PwCF on chest computed tomography and magnetic resonance imaging. We conclude that radiological outcomes to identify disease caused by A. fumigatus can be important for clinical studies and management.

Fungal Infection and Inflammation in Cystic Fibrosis

Fungi are frequently recovered from lower airway samples from people with cystic fibrosis (CF), yet the role of fungi in the progression of lung disease is debated. Recent studies suggest worsening clinical outcomes associated with airway fungal detection, although most studies to date are retrospective or observational. The presence of fungi can elicit a T helper cell type 2 (Th-2) mediated inflammatory reaction known as allergic bronchopulmonary aspergillosis (ABPA), particularly in those with a genetic atopic predisposition. In this review, we discuss the epidemiology of fungal infections in people with CF, risk factors associated with development of fungal infections, and microbiologic approaches for isolation and identification of fungi. We review the spectrum of fungal disease presentations, clinical outcomes after isolation of fungi from airway samples, and the importance of considering airway co-infections. Finally, we discuss the association between fungi and airway inflammation highlighting gaps in knowledge and future research questions that may further elucidate the role of fungus in lung disease progression.

CF Fungal Disease in the Age of CFTR Modulators

Fungi are increasingly recognised to have a significant role in the progression of lung disease in Cystic fibrosis with Aspergillus fumigatus the most common fungus isolated during respiratory sampling. The emergence of novel CFTR modulators has, however, significantly changed the outlook of disease progression in CF. In this review we discuss what impact novel CFTR modulators will have on fungal lung disease and its management in CF. We discuss how CFTR modulators affect antifungal innate immunity and consider the impact of Ivacaftor on fungal disease in individuals with gating mutations. We further review the increasing complication of drug-drug interactions with concurrent use of azole antifungal medication and highlight key unknowns that require addressing to fully understand the impact of CFTR modulators on fungal disease.

Managing Fungal Infections in Cystic Fibrosis Patients: Challenges in Clinical Practice

Cystic Fibrosis (CF) is an autosomal recessive disease characterized by a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Impairment of the CFTR protein in the respiratory tract results in the formation of thick mucus, development of inflammation, destruction of bronchial tissue, and development of bacterial or fungal infections over time. CF patients are commonly colonized and/or infected with fungal organisms, Candida albicans or Aspergillus fumigatus, with prevalence rates ranging from 5% to 78% in the literature. Risk factors for acquiring fungal organisms include older age, coinfection with Pseudomonas aeruginosa, prolonged use of oral and inhaled antibiotics, and lower forced expiratory volume (FEV₁). There are limited data available to differentiate between contamination, colonization, and active infection. Furthermore, the pathogenicity of colonization is variable in the literature as some studies report a decline in lung function associated with fungal colonization whereas others showed no difference. Limited data are available for the eradication of fungal colonization and the treatment of active invasive aspergillosis in adult CF patients. In this review article, we discuss the challenges in clinical practice and current literature available for laboratory findings, clinical diagnosis, and treatment options for fungal infections in adult CF patients.

Aspergillus fumigatus Strain-Specific Conidia Lung Persistence Causes an Allergic Broncho-Pulmonary Aspergillosis-Like Disease Phenotype

Aspergillus fumigatus is a filamentous fungus which can cause multiple diseases in humans. Allergic broncho-pulmonary aspergillosis (ABPA) is a disease diagnosed primarily in cystic fibrosis patients caused by a severe allergic response often to long-term A. fumigatus colonization in the lungs. Mice develop an allergic response to repeated inhalation of A. fumigatus spores; however, no strains have been identified that can survive long-term in the mouse lung and cause ABPA-like disease. We characterized A. fumigatus strain W72310, which was isolated from the expectorated sputum of an ABPA patient, by whole-genome sequencing and in vitro and in vivo viability assays in comparison to a common reference strain, CEA10. W72310 was resistant to leukocyte-mediated killing and persisted in the mouse lung longer than CEA10, a phenotype that correlated with greater resistance to oxidative stressors, hydrogen peroxide, and menadione, in vitro In animals both sensitized and challenged with W72310, conidia, but not hyphae, were viable in the lungs for up to 21 days in association with eosinophilic airway inflammation, airway leakage, serum IgE, and mucus production. W72310-sensitized mice that were recall challenged with conidia had increased inflammation, Th1 and Th2 cytokines, and airway leakage compared to controls. Collectively, our studies demonstrate that a unique strain of A. fumigatus resistant to leukocyte killing can persist in the mouse lung in conidial form and elicit features of ABPA-like disease.IMPORTANCE Allergic broncho-pulmonary aspergillosis (ABPA) patients often present with long-term colonization of Aspergillus fumigatus Current understanding of ABPA pathogenesis has been complicated by a lack of long-term in vivo fungal persistence models. We have identified a clinical isolate of A. fumigatus, W72310, which persists in the murine lung and causes an ABPA-like disease phenotype. Surprisingly, while viable, W72310 showed little to no growth beyond the conidial stage in the lung. This indicates that it is possible that A. fumigatus can cause allergic disease in the lung without any significant hyphal growth. The identification of this strain of A. fumigatus can be used not only to better understand disease pathogenesis of ABPA and potential antifungal treatments but also to identify features of fungal strains that drive long-term fungal persistence in the lung. Consequently, these observations are a step toward helping resolve the long-standing question of when to utilize antifungal therapies in patients with ABPA and fungal allergic-type diseases.

Single-Cell Analysis of Fungal Uptake in Cultured Airway Epithelial Cells Using Differential Fluorescent Staining and Imaging Flow Cytometry

The respiratory epithelium is the initial point of host contact for inhaled particles, leading to orchestrated, but highly heterogeneous, responses. Human airway epithelial cells (AECs) play a crucial role in host defense by promoting uptake and killing of inhaled microorganisms and concomitant cytokine production in order to recruit professional phagocytes to the site of infection. However, inhaled pathogens can also reside and replicate intracellularly to evade host immune defenses or circulating antimicrobial drugs, ultimately causing apoptosis or cell death of the infected AECs. Imaging flow cytometry (IFC) combines flow cytometry, fluorescent microscopy, and advanced data-processing algorithms to dissect the heterogeneity of the interaction of AECs and inhaled microorganisms and its outcomes at the single-cell level. Here, we describe a novel single-cell approach based on differential fluorescent staining and state-of-the-art IFC to identify, quantify, and analyze individual host-pathogen complexes from cultured AECs infected with spores of the major human fungal pathogen Aspergillus fumigatus.

Coinfection with Pseudomonas aeruginosa and Aspergillus fumigatus in cystic fibrosis

OBJECTIVES

Cystic fibrosis (CF) lung disease is characterised by mucus stasis, chronic infection and inflammation, causing progressive structural lung disease and eventual respiratory failure. CF airways are inhabited by an ecologically diverse polymicrobial environment with vast potential for interspecies interactions, which may be a contributing factor to disease progression. Pseudomonas aeruginosa and Aspergillus fumigatus are the most common bacterial and fungal species present in CF airways respectively and coinfection results in a worse disease phenotype.

METHODS

In this review we examine existing expert knowledge of chronic co-infection with P. aeruginosa and A. fumigatus in CF patients. We summarise the mechanisms of interaction and evaluate the clinical and inflammatory impacts of this co-infection.

RESULTS

P. aeruginosa inhibits A. fumigatus through multiple mechanisms: phenazine secretion, iron competition, quorum sensing and through diffusible small molecules. A. fumigatus reciprocates inhibition through gliotoxin release and phenotypic adaptations enabling evasion of P. aeruginosa inhibition. Volatile organic compounds secreted by P. aeruginosa stimulate A. fumigatus growth, while A. fumigatus stimulates P. aeruginosa production of cytotoxic elastase.

CONCLUSION

A complex bi-directional relationship exists between P. aeruginosa and A. fumigatus, exhibiting both mutually antagonistic and cooperative facets. Cross-sectional data indicate a worsened disease state in coinfected patients; however, robust longitudinal studies are required to derive causality and to determine whether interspecies interaction contributes to disease progression.

Risk factors for respiratory Aspergillus fumigatus in German Cystic Fibrosis patients and impact on lung function

Airway inflammation and chronic lung infections in cystic fibrosis (CF) patients are mostly caused by bacteria, e.g. Pseudomonas aeruginosa (PA). The role of fungi in the CF lung is still not well elucidated, but evidence for a harmful and complex role is getting stronger. The most common filamentous fungus in CF is Aspergillus fumigatus (AF). Age and continuous antibiotic treatment have been discussed as risk factors for AF colonisation but did not differentiate between transient and persistent AF colonisation. Also, the impact of co-colonisation of PA and AF on lung function is still under investigation. Data from patients with CF registered in the German Cystic Fibrosis Registry database in 2016 and 2017 were retrospectively analysed, involving descriptive and multivariate analysis to assess risk factors for transient or persistent AF colonisation. Age represented an independent risk factor for persistent AF colonisation. Prevalence was low in children less than ten years, highest in the middle age and getting lower in higher age (≥ 50 years). Continuous antibiotic lung treatment was significantly associated with AF prevalence in all age groups. CF patients with chronic PA infection had a lower lung function (FEV1%predicted), which was not influenced by an additional AF colonisation. AF colonisation without chronic PA infection, however, was significantly associated with a lower function, too. Older age up to 49 years and continuous antibiotic use were found to be the main risk factors for AF permanent colonisation. AF might be associated with decrease of lung function if not disguised by chronic PA infection.

Dysregulated signalling pathways in innate immune cells with cystic fibrosis mutations

Cystic fibrosis (CF) is one of the most common life-limiting recessive genetic disorders in Caucasians, caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). CF is a multi-organ disease that involves the lungs, pancreas, sweat glands, digestive and reproductive systems and several other tissues. This debilitating condition is associated with recurrent lower respiratory tract bacterial and viral infections, as well as inflammatory complications that may eventually lead to pulmonary failure. Immune cells play a crucial role in protecting the organs against opportunistic infections and also in the regulation of tissue homeostasis. Innate immune cells are generally affected by CFTR mutations in patients with CF, leading to dysregulation of several cellular signalling pathways that are in continuous use by these cells to elicit a proper immune response. There is substantial evidence to show that airway epithelial cells, neutrophils, monocytes and macrophages all contribute to the pathogenesis of CF, underlying the importance of the CFTR in innate immune responses. The goal of this review is to put into context the important role of the CFTR in different innate immune cells and how CFTR dysfunction contributes to the pathogenesis of CF, highlighting several signalling pathways that may be dysregulated in cells with CFTR mutations.

Cystic Fibrosis Defective Response to Infection Involves Autophagy and Lipid Metabolism

Cystic fibrosis (CF) is a hereditary disease, with 70% of patients developing a proteinopathy related to the deletion of phenylalanine 508. CF is associated with multiple organ dysfunction, chronic inflammation, and recurrent lung infections. CF is characterized by defective autophagy, lipid metabolism, and immune response. Intracellular lipid accumulation favors microbial infection, and autophagy deficiency impairs internalized pathogen clearance. Myriocin, an inhibitor of sphingolipid synthesis, significantly reduces inflammation, promotes microbial clearance in the lungs, and induces autophagy and lipid oxidation. RNA-seq was performed in Aspergillusfumigatus-infected and myriocin-treated CF patients’ derived monocytes and in a CF bronchial epithelial cell line. Fungal clearance was also evaluated in CF monocytes. Myriocin enhanced CF patients’ monocytes killing of A. fumigatus. CF patients’ monocytes and cell line responded to infection with a profound transcriptional change; myriocin regulates genes that are involved in inflammation, autophagy, lipid storage, and metabolism, including histones and heat shock proteins whose activity is related to the response to infection. We conclude that the regulation of sphingolipid synthesis induces a metabolism drift by promoting autophagy and lipid consumption. This process is driven by a transcriptional program that corrects part of the differences between CF and control samples, therefore ameliorating the infection response and pathogen clearance in the CF cell line and in CF peripheral blood monocytes.

The fungal airway microbiome in cystic fibrosis and non-cystic fibrosis bronchiectasis

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The prevalence of fungal disease is increasing in CF and non-CF bronchiectasis.

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Effective management of fungal disease requires an understanding of the mycobiome.

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Culture methods alone are inadequate for the accurate diagnosis of fungal disease.

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Our study provides a framework to characterize fungal airway disease using NGS.

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NGS can improve detection and clinical management of fungal infections.

Background

The prevalence of fungal disease in cystic fibrosis (CF) and non-CF bronchiectasis is increasing and the clinical spectrum is widening. Poor sensitivity and a lack of standard diagnostic criteria renders interpretation of culture results challenging. In order to develop effective management strategies, a more accurate and comprehensive understanding of the airways fungal microbiome is required. The study aimed to use DNA sequences from sputum to assess the load and diversity of fungi in adults with CF and non-CF bronchiectasis.

Methods

Next generation sequencing of the ITS2 region was used to examine fungal community composition (n = 176) by disease and underlying clinical subgroups including allergic bronchopulmonary aspergillosis, chronic necrotizing pulmonary aspergillosis, non-tuberculous mycobacteria, and fungal bronchitis. Patients with no known active fungal disease were included as disease controls.

Results

ITS2 sequencing greatly increased the detection of fungi from sputum. In patients with CF fungal diversity was lower, while burden was higher than those with non-CF bronchiectasis. The most common operational taxonomic unit (OTU) in patients with CF was Candida parapsilosis (20.4%), whereas in non-CF bronchiectasis sputum Candida albicans (21.8%) was most common. CF patients with overt fungal bronchitis were dominated by Aspergillus spp., Exophiala spp., Candida parapsilosis or Scedosporium spp.

Conclusion

This study provides a framework to more accurately characterize the extended spectrum of fungal airways diseases in adult suppurative lung diseases.

Progress in Model Systems of Cystic Fibrosis Mucosal Inflammation to Understand Aberrant Neutrophil Activity

In response to recurrent infection in cystic fibrosis (CF), powerful innate immune signals trigger polymorphonuclear neutrophil recruitment into the airway lumen. Exaggerated neutrophil proteolytic activity results in sustained inflammation and scarring of the airways. Consequently, neutrophils and their secretions are reliable clinical biomarkers of lung disease progression. As neutrophils are required to clear infection and yet a direct cause of airway damage, modulating adverse neutrophil activity while preserving their pathogen fighting function remains a key area of CF research. The factors that drive their pathological behavior are still under investigation, especially in early disease when aberrant neutrophil behavior first becomes evident. Here we examine the latest findings of neutrophils in pediatric CF lung disease and proposed mechanisms of their pathogenicity. Highlighted in this review are current and emerging experimental methods for assessing CF mucosal immunity and human neutrophil function in the laboratory.

Aspergillus fumigatus and Aspergillosis in 2019

Aspergillus fumigatus is a saprotrophic fungus; its primary habitat is the soil. In its ecological niche, the fungus has learned how to adapt and proliferate in hostile environments. This capacity has helped the fungus to resist and survive against human host defenses and, further, to be responsible for one of the most devastating lung infections in terms of morbidity and mortality. In this review, we will provide (i) a description of the biological cycle of A. fumigatus; (ii) a historical perspective of the spectrum of aspergillus disease and the current epidemiological status of these infections; (iii) an analysis of the modes of immune response against Aspergillus in immunocompetent and immunocompromised patients; (iv) an understanding of the pathways responsible for fungal virulence and their host molecular targets, with a specific focus on the cell wall; (v) the current status of the diagnosis of different clinical syndromes; and (vi) an overview of the available antifungal armamentarium and the therapeutic strategies in the clinical context. In addition, the emergence of new concepts, such as nutritional immunity and the integration and rewiring of multiple fungal metabolic activities occurring during lung invasion, has helped us to redefine the opportunistic pathogenesis of A. fumigatus.

Interactions between Aspergillus fumigatus and Pulmonary Bacteria: Current State of the Field, New Data, and Future Perspective

Aspergillus fumigatus and Pseudomonas aeruginosa are central fungal and bacterial members of the pulmonary microbiota. The interactions between A. fumigatus and P. aeruginosa have only just begun to be explored. A balance between inhibitory and stimulatory effects on fungal growth was observed in mixed A. fumigatus-P. aeruginosa cultures. Negative interactions have been seen for homoserine-lactones, pyoverdine and pyochelin resulting from iron starvation and intracellular inhibitory reactive oxidant production. In contrast, several types of positive interactions were recognized. Dirhamnolipids resulted in the production of a thick fungal cell wall, allowing the fungus to resist stress. Phenazines and pyochelin favor iron uptake for the fungus. A. fumigatus is able to use bacterial volatiles to promote its growth. The immune response is also differentially regulated by co-infections.

Aspergillus colonization and antifungal immunity in cystic fibrosis patients

Cystic fibrosis (CF), caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, is the most common inherited life-limiting disease in North European people affecting 90,000 people worldwide. Progressive lung damage caused by recurrent infection and chronic airway inflammation is the major determinant of survival with a median age at death of 29 years. Approximately 60% of CF patients are infected with Aspergillus fumigatus, a ubiquitous environmental fungus, and its presence has been associated with accelerated lung function decline. Half of the patients infected with Aspergillus are <18 years of age. Yet time of acquisition of this fungus and determinants of CF-related Aspergillus disease severity and progression are not known. CFTR expression has been demonstrated in cells of the innate and adaptive immune system and has shown to be critical for normal function. Research delineating the role of CFTR-deficient phagocytes in Aspergillus persistence and infection in the CF lung, has only recently received attention. In this concise review we aim to present the current understanding with respect to when people with CF acquire infection with A. fumigatus and antifungal immune responses by CF immune cells.

Pathophysiological aspects of Aspergillus colonization in disease

Aspergillus colonization of the lower respiratory airways is common in normal people, and of little clinical significance. However, in some patients, colonization is associated with severe disease including poorly controlled asthma, allergic bronchopulmonary aspergillosis (ABPA) with sputum plugs, worse lung function in chronic obstructive pulmonary aspergillosis (COPD), invasive aspergillosis, and active infection in patients with chronic pulmonary aspergillosis (CPA). Therefore, understanding the pathophysiological mechanisms of fungal colonization in disease is essential to develop strategies to avert or minimise disease. Aspergillus cell components promoting fungal adherence to the host surface, extracellular matrix, or basal lamina are indispensable for pathogen persistence. However, our understanding of individual differences in clearance of A. fumigatus from the lung in susceptible patients is close to zero.

Microbial uptake by the respiratory epithelium: outcomes for host and pathogen

Intracellular occupancy of the respiratory epithelium is a useful pathogenic strategy facilitating microbial replication and evasion of professional phagocytes or circulating antimicrobial drugs. A less appreciated but growing body of evidence indicates that the airway epithelium also plays a crucial role in host defence against inhaled pathogens, by promoting ingestion and quelling of microorganisms, processes that become subverted to favour pathogen activities and promote respiratory disease. To achieve a deeper understanding of beneficial and deleterious activities of respiratory epithelia during antimicrobial defence, we have comprehensively surveyed all current knowledge on airway epithelial uptake of bacterial and fungal pathogens. We find that microbial uptake by airway epithelial cells (AECs) is a common feature of respiratory host-microbe interactions whose stepwise execution, and impacts upon the host, vary by pathogen. Amidst the diversity of underlying mechanisms and disease outcomes, we identify four key infection scenarios and use best-characterised host-pathogen interactions as prototypical examples of each. The emergent view is one in which effi-ciency of AEC-mediated pathogen clearance correlates directly with severity of disease outcome, therefore highlighting an important unmet need to broaden our understanding of the antimicrobial properties of respiratory epithelia and associated drivers of pathogen entry and intracellular fate.

The myriad challenges of respiratory fungal infection in cystic fibrosis

Fungal infection in cystic fibrosis (CF) is a recognized challenge, with many areas requiring further investigation. Consensus definitions exist for allergic bronchopulmonary aspergillus in CF, but the full scope of clinically relevant non-allergic fungal disease in CF-asymptomatic colonization, transient or chronic infection localized to endobronchial mucus plugs or airway tissue, and invasive disease-is yet to be clearly defined. Recent advances in mycological culture and non-culture identification have expanded the list of both potential pathogens and community commensals in the lower respiratory tract. Here we aim to outline the current understanding of fungal presence in the CF respiratory tract, risk factors for acquiring fungi, host-pathogen interactions that influence the role of fungi from bystander to pathogen, advances in the diagnostic approaches to isolating and identifying fungi in CF respiratory samples, challenges of classifying clinical phenotypes of CF patients with fungi, and current treatment approaches. Development and validation of biomarkers characteristic of different fungal clinical phenotypes, and controlled trials of antifungal agents in well-characterized target populations, remain central challenges to surmount and goals to be achieved.

Newborn Cystic Fibrosis Pigs Have a Blunted Early Response to an Inflammatory Stimulus

RATIONALE

Studies suggest that inappropriate responses to proinflammatory stimuli might contribute to inflammation in cystic fibrosis (CF) lungs. However, technical challenges have made it difficult to distinguish whether altered responses in CF airways are an intrinsic defect or a secondary effect of chronic disease in their tissue of origin. The CF pig model provides an opportunity to study the inflammatory responses of CF airways at birth, before the onset of infection and inflammation.

OBJECTIVES

To test the hypothesis that acute inflammatory responses are perturbed in porcine CF airways.

METHODS

We investigated the inflammatory responses of newborn CF and non-CF pig airways following a 4-hour exposure to heat-killed Staphylococcus aureus, in vivo and in vitro.

MEASUREMENTS AND MAIN RESULTS

Following an in vivo S. aureus challenge, markers of inflammation were similar between CF and littermate control animals through evaluation of bronchoalveolar lavage and tissues. However, transcriptome analysis revealed genotype-dependent differences as CF pigs showed a diminished host defense response compared with their non-CF counterparts. Furthermore, CF pig airways exhibited an increase in apoptotic pathways and a suppression of ciliary and flagellar biosynthetic pathways. Similar differences were observed in cultured airway epithelia from CF and non-CF pigs exposed to the stimulus.

CONCLUSIONS

Transcriptome profiling suggests that acute inflammatory responses are dysregulated in the airways of newborn CF pigs.

Risk factors for persistent Aspergillus respiratory isolation in cystic fibrosis

BACKGROUND

Aspergillus species are increasingly detected in the respiratory tracts of individuals with cystic fibrosis (CF), and chronic Aspergillus fumigatus is associated with more frequent hospitalizations for pulmonary exacerbations. However, patient and clinical factors that may contribute to the acquisition of persistent Aspergillus infection have yet to be identified. The objective of this study was to identify risk factors for development of Aspergillus respiratory isolation in CF.

METHODS

A retrospective cohort study of participants in the CF Foundation Patient Registry between 2006 and 2012 was conducted. Generalized estimating equation models were used to evaluate the association between the development of persistent Aspergillus respiratory isolation and individual level demographic and clinical characteristics.

RESULTS

Among 16,095 individuals with CF followed from 2006 to 2012, 1541 (9.6%) subjects developed persistent Aspergillus isolation. White race (Odds Ratio [OR] 1.74, 95% confidence interval 1.23, 2.48, p<0.001) and pancreatic insufficiency (OR 1.50, 95% CI 1.09, 2.06, p<0.001) were found to be risk factors for persistent Aspergillus isolation. Chronic therapies, including inhaled antibiotics (OR 1.33; 95% CI 1.21, 1.46), macrolides (OR 1.23, 95% CI 1.14, 1.32, p<0.001), and inhaled corticosteroids (OR 1.13, 95% CI 1.04, 1.20, p<0.001) were also independently associated with an increased risk for persistent Aspergillus isolation.

CONCLUSIONS

We identified macrolides and inhaled antibiotics, which individually have been shown to improve CF outcomes, and inhaled corticosteroids as risk factors for developing persistent Aspergillus isolation. Further work is needed to determine whether these associations are causal or due to confounding by other factors.

Anti-Aspergillus Activities of the Respiratory Epithelium in Health and Disease

Respiratory epithelia fulfil multiple roles beyond that of gaseous exchange, also acting as primary custodians of lung sterility and inflammatory homeostasis. Inhaled fungal spores pose a continual antigenic, and potentially pathogenic, challenge to lung integrity against which the human respiratory mucosa has developed various tolerance and defence strategies. However, respiratory disease and immune dysfunction frequently render the human lung susceptible to fungal diseases, the most common of which are the aspergilloses, a group of syndromes caused by inhaled spores of Aspergillus fumigatus. Inhaled Aspergillus spores enter into a multiplicity of interactions with respiratory epithelia, the mechanistic bases of which are only just becoming recognized as important drivers of disease, as well as possible therapeutic targets. In this mini-review we examine current understanding of Aspergillus-epithelial interactions and, based upon the very latest developments in the field, we explore two apparently opposing schools of thought which view epithelial uptake of Aspergillus spores as either a curative or disease-exacerbating event.

Organization of Patient Management and Fungal Epidemiology in Cystic Fibrosis

The achievement of a better life for cystic fibrosis (CF) patients is mainly caused by a better management and infection control over the last three decades. Herein, we want to summarize the cornerstones for an effective management of CF patients and to give an overview of the knowledge about the fungal epidemiology in this clinical context in Europe. Data from a retrospective analysis encompassing 66,616 samples from 3235 CF patients followed-up in 9 CF centers from different European countries are shown.

F508del CFTR gene mutation in patients with allergic bronchopulmonary aspergillosis

OBJECTIVE

The F508del mutation occurs in approximately 3.5% of Caucasian population of Northern Europe. Heterozygotes have increased risk for asthma and reduced pulmonary function. Allergic bronchopulmonary aspergillosis (ABPA) is more common in patients with cystic fibrosis (CF). We aimed to establish the frequency of F508del mutation in adult patients with ABPA.

METHODS

A retrospective matched case-control study of CF genotyped patients with ABPA seen at the National Aspergillosis Centre was undertaken. Key data were collected retrospectively from medical records, including respiratory comorbidities, total IgE, Aspergillus IgG and IgE, and immunoglobulins. Cystic fibrosis transmembrane regulator (CFTR) gene mutation analysis included multiplex PCR and sequencing.

RESULTS

From a cohort of 189 ABPA patients, 156 were screened for common mutations and variants in the CFTR gene. Eighteen were heterozygous for at least one CFTR mutation; 12 (7.7%) were heterozygous for the F508del, notably; 3 were heterozygous for the intron 8 5T variant; and 1 for an intronic variant of uncertain significance, c.3139 + 18C>T. Eight (67%) had asthma, 7 (58%) had CT-defined bronchiectasis, 4 (33%) hypergammaglobulinemia (>16 g/L), 3 (25%) sinusitis and 1 (8%) chronic pulmonary aspergillosis. Eight (67%) had elevated Aspergillus IgG antibodies (42-98 mg/L), and 8 (67%) had total IgE above 1,000 KIU/L. Two individuals heterozygous for the F508del mutation and the TG12T5 variant were diagnosed with CF, leading to a de novo CF discovery rate of 1.3%.

CONCLUSIONS

In our ABPA patient cohort, the presence of the delta F508 mutation was higher than that seen in general population. Genetic counseling for CFTR genotyping might be appropriate for these patients.

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.

Allergic and Noninvasive Infectious Pulmonary Aspergillosis Syndromes

Aspergillus spp are ubiquitous in the environment, and inhalation of Aspergillus spores is unavoidable. An intact immune system, with normal airway function, protects most people from disease. Globally, however, the toll from aspergillosis is high. The literature has largely focused on invasive aspergillosis, yet the burden in terms of chronicity and prevalence is higher for noninvasive Aspergillus conditions. This article discusses allergic aspergilloses and provides an update on the diagnosis and management of allergic bronchopulmonary aspergillosis, including in patients with cystic fibrosis, and an update on severe asthma with fungal sensitization. In addition, the presentation, investigation, and management of noninvasive infectious aspergilloses are reviewed.

Aspergillosis and the role of mucins in cystic fibrosis

The prevalence of aspergillosis in CF patients has until recently been underestimated, but increasing evidence suggests that it may play an important role in the progression of CF lung disease. In healthy airways, Aspergillus fumigatus can be efficiently removed from the lung by mechanisms such as mucociliary clearance and cough. However, these mechanisms are defective in CF, allowing pathogens such as A. fumigatus to germinate and establish chronic infections within the airways. The precise means by which A. fumigatus contributes to CF lung disease remain largely unclear. As the first point of contact within the lung, and an important component of the innate immune system, it is likely that the mucus barrier plays an important role in this process. Study of the functional interplay between this vital protective barrier, and in particular its principal structural components, the polymeric gel-forming mucins, and CF pathogens such as A. fumigatus, is at an early stage. A. fumigatus protease activity has been shown to upregulate mucus production by inducing mucin mRNA and protein expression, and A. fumigatus proteases and glycosidases are able to degrade mucins. This may allow A. fumigatus to alter mucus barrier properties to promote fungal colonization of the airways and/or utilize mucins as a nutrient source. Moreover, conidial surface lectin binding to mucin glycans is a key aspect of clearance of Aspergillus from the lung in health but may be an important aspect of colonization, where mucociliary clearance is compromised, as in the CF lung. Here we discuss the nature of the mucus barrier and its mucin components in CF, and how they may be implicated in A. fumigatus infection. Pediatr Pulmonol 2017;52:548-555. © 2016 The Authors. Pediatric Pulmonology. Published by Wiley Periodicals, Inc.

Aspergillus in chronic lung disease: Modeling what goes on in the airways

Aspergillus species cause a range of respiratory diseases in humans. While immunocompromised patients are at risk for the development of invasive infection with these opportunistic molds, patients with underlying pulmonary disease can develop chronic airway infection with Aspergillus species. These conditions span a range of inflammatory and allergic diseases including Aspergillus bronchitis, allergic bronchopulmonary aspergillosis, and severe asthma with fungal sensitization. Animal models are invaluable tools for the study of the molecular mechanism underlying the colonization of airways by Aspergillus and the host response to these non-invasive infections. In this review we summarize the state-of-the-art with respect to the available animal models of noninvasive and allergic Aspergillus airway disease; the key findings of host-pathogen interaction studies using these models; and the limitations and future directions that should guide the development and use of models for the study of these important pulmonary conditions.

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.

Current Concepts and Controversies in Innate Immunity of Cystic Fibrosis Lung Disease

Cystic fibrosis (CF) lung disease is characterized by chronic infection and inflammation. The inflammatory response in CF is dominated by the activation of the innate immune system. Bacteria and fungi represent the key pathogens chronically colonizing the CF airways. In response, innate immune pattern recognition receptors, expressed by airway epithelial and myeloid cells, sense the microbial threat and release chemoattractants to recruit large numbers of neutrophils into CF airways. However, neutrophils fail to efficiently clear the invading pathogens, but instead release harmful proteases and oxidants and finally cause tissue injury. Here, we summarize and discuss current concepts and controversies in the field of innate immunity in CF lung disease, facing the ongoing questions of whether inflammation is good or bad in CF and how innate immune mechanisms could be harnessed therapeutically.

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.