Serological and biochemical characterization of Aspergillus fumigatus Asp f 10 as a potential diagnostic marker in ABPA and related respiratory diseases.

BACKGROUND

Aspergillus fumigatus is a major cause of allergic bronchopulmonary aspergillosis (ABPA), yet diagnosis remains challenging due to overlap with other atopic conditions. Asp f 10, a secreted aspartic protease, is listed as an allergen but remains poorly characterized in terms of biochemical properties and diagnostic relevance.

METHODS

We profiled the A. fumigatus secretome under host-mimicking conditions to identify IgG-reactive proteins, followed by cloning and recombinant expression of full-length and mature Asp f 10. Biochemical stability, enzymatic activity, and serological reactivity (IgE and IgG) were evaluated using sera from patients with ABPA, steroid-unresponsive severe asthma with Aspergillus sensitization (SAAS), and other allergic and non-allergic controls. Diagnostic performance was assessed by ROC and linear discriminant analyses.

RESULTS

Asp f 10 was identified as an extracellular IgG-reactive protease. Recombinant mature Asp f 10 exhibited folded conformation, structural stability, and gelatinolytic activity, whereas the full-length protein lacked defined structure. Both isoforms bound patient IgE and IgG; however, only Asp f 10-specific IgG responses were significantly elevated in ABPA and SAAS. ROC analysis demonstrated excellent diagnostic capacity for IgG (AUC = 0.90), far surpassing IgE (AUC = 0.54). Despite IgE recognition, mature Asp f 10 failed to induce histamine release, suggesting limited effector activity.

CONCLUSION

Asp f 10 is a biologically active protease, and Asp f 10-specific IgG responses provide a robust biomarker for ABPA, outperforming IgE in diagnostic accuracy. Incorporating Asp f 10 into serological panels may improve differential diagnosis of Aspergillus-associated respiratory diseases.