The relationship between biomarkers of fungal allergy and lung damage in asthma

Aspergillus fumigatus in cystic fibrosis: An update on immune interactions and molecular diagnostics in allergic bronchopulmonary aspergillosis

A wide spectrum of pathological conditions may result from the interaction of Aspergillus fumigatus and the immune system of its human host. Allergic bronchopulmonary aspergillosis is one of the most severe A. fumigatus-related diseases due to possible evolution toward pleuropulmonary fibrosis and respiratory failure. Allergic bronchopulmonary aspergillosis occurs almost exclusively in cystic fibrosis or asthmatic patients. An estimated 8%-10% of patients with cystic fibrosis experience this condition. The diagnosis of allergic bronchopulmonary aspergillosis relies on criteria first established in 1977. Progress in the understanding of host-pathogen interactions in A. fumigatus and patients with cystic fibrosis and the ongoing validation of novel laboratory tools concur to update and improve the diagnosis of allergic bronchopulmonary aspergillosis.

Sensitization to Aspergillus fumigatus as a risk factor for bronchiectasis in COPD

BACKGROUND

Bronchiectasis-chronic obstructive pulmonary disease (COPD) overlap presents a possible clinical phenotype of COPD, but it is unclear why it develops in a subset of patients. We hypothesized that sensitization to Aspergillus fumigatus (A fum) is associated with bronchiectasis in COPD and occurs more frequently in vitamin D-deficient patients.

METHODS

This observational study investigated sensitization to A fum in an outpatient clinical cohort of 300 COPD patients and 50 (ex-) smoking controls. Total IgE, A fum-specific IgE against the crude extract and against the recombinant antigens and A fum IgG were measured using ImmunoCAP fluoroenzyme immunoassay. Vitamin D was measured by radioimmunoassay, and computed tomography images of the lungs were scored using the modified Reiff score.

RESULTS

Sensitization to A fum occurred in 18% of COPD patients compared to 4% of controls (P=0.0110). In all, 31 COPD patients (10%) were sensitized to the crude extract and 24 patients (8%) had only IgE against recombinant antigens. A fum IgG levels were significantly higher in the COPD group (P=0.0473). Within COPD, A fum-sensitized patients were more often male (P=0.0293) and more often had bronchiectasis (P=0.0297). Pseudomonas aeruginosa and Serratia marcescens were more prevalent in historical sputum samples of A fum-sensitized COPD patients compared to A fum-non-sensitized COPD patients (P=0.0436). Vitamin D levels were comparable (P=0.2057). Multivariate analysis demonstrated that sensitization to recombinant f1 or f3 had a 2.8-fold increased risk for bronchiectasis (P=0.0030).

CONCLUSION

These results highlight a potential role for sensitization to A fum in COPD-related bronchiectasis.

In Vivo Biomarker Analysis of the Effects of Intranasally Dosed PC945, a Novel Antifungal Triazole, on Aspergillus fumigatus Infection in Immunocompromised Mice

PC945 is a novel triazole optimized for lung delivery, and the objective of this study is to determine the effects of intranasally dosed PC945 on Aspergillus fumigatus infection and associated biomarkers in immunocompromised mice. PC945, posaconazole, or voriconazole was administered intranasally once daily on days 0 to 3 (early intervention) or days 1 to 3 (late intervention) postinfection in temporarily neutropenic A/J mice infected intranasally with A. fumigatus, and bronchoalveolar lavage fluid (BALF) and serum were collected on day 3. The effects of extended prophylaxis treatment (daily from days −7 to +3 or days −7 to 0) were also compared with those of the shorter treatment regimens (days −1 to +3 or days −1 and 0). Early and late interventions with PC945 (2.8 to 350 μg/mouse; approximately 0.11 to ∼14 mg/kg of body weight) were found to inhibit lung fungal loads and to decrease the concentrations of galactomannan (GM) in both BALF and serum as well as several biomarkers in BALF (interferon gamma [IFN-γ], interleukin-17 [IL-17], and malondialdehyde) and serum (tumor necrosis factor alpha [TNF-α] and IL-6) in a dose-dependent manner and were >3- and >47-fold more potent than intranasally dosed posaconazole and voriconazole, respectively. Furthermore, extended prophylaxis with low-dose PC945 (0.56 μg/mouse; 0.022 mg/kg) was found to inhibit fungal loads and to decrease the concentrations biomarkers more potently than did the shorter treatment regimens. Thus, PC945 dosed intranasally once daily showed potent antifungal effects, and the effects of PC945 accumulated upon repeat dosing and were persistent. Therefore, PC945 has the potential to be a novel inhaled therapy for the treatment of A. fumigatus infection in humans.

Multivariate Analysis As a Support for Diagnostic Flowcharts in Allergic Bronchopulmonary Aspergillosis: A Proof-of-Concept Study

Molecular-based allergy diagnosis yields multiple biomarker datasets. The classical diagnostic score for allergic bronchopulmonary aspergillosis (ABPA), a severe disease usually occurring in asthmatic patients and people with cystic fibrosis, comprises succinct immunological criteria formulated in 1977: total IgE, anti-Aspergillus fumigatus (Af) IgE, anti-Af “precipitins,” and anti-Af IgG. Progress achieved over the last four decades led to multiple IgE and IgG(4) Af biomarkers available with quantitative, standardized, molecular-level reports. These newly available biomarkers have not been included in the current diagnostic criteria, either individually or in algorithms, despite persistent underdiagnosis of ABPA. Large numbers of individual biomarkers may hinder their use in clinical practice. Conversely, multivariate analysis using new tools may bring about a better chance of less diagnostic mistakes. We report here a proof-of-concept work consisting of a three-step multivariate analysis of Af IgE, IgG, and IgG4 biomarkers through a combination of principal component analysis, hierarchical ascendant classification, and classification and regression tree multivariate analysis. The resulting diagnostic algorithms might show the way for novel criteria and improved diagnostic efficiency in Af-sensitized patients at risk for ABPA.

Sensitization to Aspergillus species is associated with frequent exacerbations in severe asthma

Background

Severe asthma is a largely heterogeneous disease with varying phenotypic profiles. The relationship between specific allergen sensitization and asthma severity, particularly in Asia, remains unclear. We aim to study the prevalence of specific allergen sensitization patterns and investigate their association with outcomes in a severe asthma cohort in an Asian setting.

Methods

We conducted a cross-sectional study of patients receiving step 4 or 5 Global Initiative for Asthma treatment. Univariate and multivariate analyses were performed to assess the association between sensitization to a specific identifiable allergen by skin prick test (SPT) and uncontrolled asthma (defined in our study as the use of ≥2 steroid bursts or hospitalization in the past year, a history of near-fatal asthma or evidence of airflow obstruction on spirometry).

Results

Two hundred and six severe asthma patients (mean age 45±17 years, 99 [48.1%] male) were evaluated. Of them, 78.2% had a positive SPT to one or more allergens. The most common allergen to which patients were sensitized was house dust mites (Blomia tropicalis, Dermatophagoides pteronyssinus and Dermatophagoides farinae). Also, 11.7% were sensitized to Aspergillus species. On multivariate analysis, Aspergillus sensitization was associated with uncontrolled asthma (odds ratio 6.07, 95% confidence interval 1.80–20.51). In particular, Aspergillus sensitization was independently associated with the use of ≥2 steroid bursts in the past year (odds ratio 3.05, 95% confidence interval 1.04–8.95). No similar associations of uncontrolled asthma with sensitization to any other allergens were found.

Conclusion

High allergen, specifically Aspergillus sensitization was observed in the Asian population with severe asthma by SPT. Aspergillus sensitization was specifically associated with frequent exacerbations and a greater corticosteroid requirement. An improved understanding of the severe asthma with Aspergillus sensitization phenotype is warranted, which is likely a subgroup of severe asthma with fungal sensitization.