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Disease-specific recombinant allergens for the diagnosis of allergic bronchopulmonary aspergillosis
R Crameri1, S Hemmann, C Ismail
1Swiss Institute of Allergy and Asthma Research (SIAF), Davos, Switzerland.
Abstract:
Allergic bronchopulmonary aspergillosis (ABPA), a severe pulmonary complication caused by Aspergillus fumigatus, is considered a complex clinical syndrome with defined serological, pathological radiological and clinical features. The diagnosis of ABPA is often difficult because of several overlapping clinical and laboratory findings shared between asthma with sensitization to A. fumigatus and ABPA, but essential for treatment to prevent severe deterioration of pulmonary function. We have cloned A. fumigatus allergens from a cDNA library displayed on phage surface, sequenced the inserts and produced recombinant proteins in Escherichia coli. The single recombinant allergens were used to assess the immunological response in representative groups of A. fumigatus-sensitized asthmatics with or without ABPA and healthy controls. The allergens rAsp f 1, a 16.9 kDa ribotoxin, rAsp f 3, a 18.5 kDa peroxisomal protein, and rAsp f 6, a 23 kDa manganese superoxide dismutase, were identified as proteins with known biological function and rAsp f 4, a 30 kDa allergen, lacks sequence homology to known proteins. The secreted ribotoxin rAsp f 1 and rAsp f 3 are recognized by serum IgE of A. fumigatus-sensitized asthmatics with or without ABPA, whereas the non-secreted manganese superoxide dismutase rAsp f 6 and the rAsp f 4 allergen are exclusively recognized by serum IgE of ABPA patients. The dissection of IgE-mediated immune responses to single recombinant A. fumigatus allergens in asthmatic patients allow a discrimination between ABPA and A. fumigatus sensitization with high specificity (100%) and sensitivity (90%).
Insights
Diagnosing allergic bronchopulmonary aspergillosis (ABPA) is challenging. Recombinant Aspergillus fumigatus allergens accurately differentiate ABPA from asthma with A. fumigatus sensitization, aiding treatment decisions.
Area of Science:
- Medical Mycology
- Immunology
- Pulmonology
Background:
- Allergic bronchopulmonary aspergillosis (ABPA) is a severe pulmonary complication of Aspergillus fumigatus infection.
- Distinguishing ABPA from asthma with A. fumigatus sensitization is clinically challenging due to overlapping symptoms and lab findings.
- Accurate diagnosis is crucial to prevent severe lung function decline.
Purpose of the Study:
- To develop a diagnostic method for differentiating ABPA from A. fumigatus sensitization in asthmatics.
- To identify specific Aspergillus fumigatus allergens that can distinguish between these conditions.
- To assess the diagnostic accuracy of recombinant allergens in clinical samples.
Main Methods:
- Cloning of A. fumigatus allergens from a cDNA library.
- Production of recombinant allergens (rAsp f 1, rAsp f 3, rAsp f 6, rAsp f 4) in E. coli.
- Assessment of serum IgE responses to recombinant allergens in patients with ABPA, sensitized asthmatics, and healthy controls.
Main Results:
- Secreted allergens rAsp f 1 and rAsp f 3 were recognized by IgE from both ABPA and sensitized asthmatic patients.
- Non-secreted allergens rAsp f 6 and rAsp f 4 were exclusively recognized by IgE from ABPA patients.
- Dissection of IgE responses to single recombinant allergens achieved 100% specificity and 90% sensitivity in discriminating ABPA.
Conclusions:
- Recombinant Aspergillus fumigatus allergens can reliably differentiate ABPA from A. fumigatus sensitization in asthmatic patients.
- Specific allergens, particularly rAsp f 6 and rAsp f 4, are key diagnostic markers for ABPA.
- This approach offers a highly specific and sensitive tool for diagnosing ABPA, guiding appropriate patient management.
