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Recombinant Aspergillus fumigatus allergens: from the nucleotide sequences to clinical applications
1Swiss Institute of Allergy and Asthma Research, Davos. crameri@siaf.unizh.ch
Abstract:
Members of the genus Aspergillus are opportunistic pathogens for cold- and warm-blooded animals. They are associated with an impressive spectrum of diseases in humans, ranging from benign colonization of the lung to life-threatening diseases such as invasive aspergillosis or allergic bronchopulmonary aspergillosis (ABPA). Aspergillus fumigatus is the etiological agent identified in most of the Aspergillus-related human diseases and is therefore of particular clinical relevance. A major problem in the diagnosis of A. fumigatus-related complications arises from the lack of standardized fungal extracts. The allergenicity of commercial A. fumigatus extracts depends on many factors including the strain used, growth conditions, harvesting and extraction procedures hampering the development of diagnostic reagents suitable for the discrimination between A. fumigatus-related diseases. Molecular DNA/RNA technologies and biotechnological procedures allow cloning, characterization and production of large amounts of single, highly pure allergens. The development of phage surface display technologies for cloning cDNAs has speeded up the isolation of candidate cDNAs encoding allergens. Screening of an A. fumigatus cDNA library displayed on the surface of phage M13 allowed characterization and production of a panel of allergens identified as proteins with known biological function or as allergens without sequence homology to known proteins. They belong to two functional categories: secreted and cytoplasmic proteins. Secreted allergens are recognized by serum IgE of A. fumigatus-sensitized individuals with or without ABPA, whereas nonsecreted allergens are exclusively recognized by serum IgE of ABPA patients. The dissection of IgE-mediated immune responses to single A. fumigatus allergens allows a discrimination between ABPA and A. fumigatus sensitization with high specificity and sensitivity demonstrating the power of recombinant allergens for the differential diagnosis of A. fumigatus-related pulmonary complications.
Insights
Recombinant Aspergillus fumigatus allergens aid in diagnosing lung diseases. Differentiating between allergic bronchopulmonary aspergillosis and sensitization is now possible with high accuracy.
Area of Science:
- Medical Mycology
- Immunology
- Biotechnology
Background:
- Aspergillus fumigatus causes various human diseases, from lung colonization to invasive and allergic forms.
- Accurate diagnosis of A. fumigatus-related lung diseases is challenging due to non-standardized fungal extracts and variable allergenicity.
- Developing reliable diagnostic reagents requires pure, well-characterized allergens.
Purpose of the Study:
- To develop and characterize a panel of recombinant Aspergillus fumigatus allergens.
- To assess the utility of these recombinant allergens in differentiating between allergic bronchopulmonary aspergillosis (ABPA) and A. fumigatus sensitization.
- To demonstrate the diagnostic power of single recombinant allergens in A. fumigatus-related pulmonary complications.
Main Methods:
- Utilized phage surface display technology to clone cDNAs encoding A. fumigatus allergens.
- Screened an A. fumigatus cDNA library displayed on M13 phage.
- Produced and characterized a panel of purified recombinant allergens.
- Analyzed IgE-mediated immune responses to single allergens in patients with A. fumigatus sensitization and ABPA.
Main Results:
- Identified and produced recombinant allergens, including secreted and cytoplasmic proteins.
- Secreted allergens were recognized by IgE from individuals with A. fumigatus sensitization (with or without ABPA).
- Non-secreted (cytoplasmic) allergens were exclusively recognized by IgE from ABPA patients.
- Dissecting IgE responses to single allergens enabled high-specificity and sensitivity discrimination between ABPA and sensitization.
Conclusions:
- Recombinant allergens provide a powerful tool for the differential diagnosis of A. fumigatus-related pulmonary diseases.
- Distinguishing between ABPA and simple A. fumigatus sensitization is achievable using specific recombinant allergens.
- This approach overcomes limitations of traditional fungal extracts, paving the way for improved diagnostic reagents.