Serum anti- Aspergillus fumigatus antibodies by immunoblot and ELISA in cystic fibrosis with allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) occurs with a prevalence of 5% to 15% in patients with cystic fibrosis (CF). Because of the frequent colonization with Aspergillus fumigatus (Af) in CF, the causative agent of ABPA, antibody reactivity to Af proteins is frequently observed, which obscures the diagnosis of ABPA. Patients with CF are also categorized according to the presence of positive skin test responses to Af and/or the presence of positive precipitins. In this study we used ELISA and immunoblot assay to detect IgE and IgG anti-Af antibodies in patients with CF and ABPA ( n = 13) compared with other groups of patients with CF: those with positive skin test and positive precipitin results ( n = 18), those with positive skin test and negative precipitin results ( n = 14), those with negative skin test and positive precipitin results ( n = 10), and those with negative skin test and negative precipitin results ( n = 35). IgE and IgG anti-Af antibodies were significantly elevated in patients with ABPA as determined by both immunoblot assay ( p < 0.01) and ELISA ( p < 0.01). However, detection of Af antibodies by ELISA was more sensitive in discriminating patients with CF and ABPA from patients with CF who had positive skin test and positive precipitin results but lacked radiographic and clinical evidence of ABPA. In patients with CF and ABPA the immunoblot assays demonstrated a multitude of IgE, IgG, and IgA antibody responses to Af proteins, which ranged in molecular weight from 14 kd to greater than 106 kd. The level of IgE anti-Af antibody to individual proteins decreased during remissions of ABPA. IgG and IgA anti-Af antibodies, however, once developed did not decrease nearly as much.