Specific antibodies to recombinant allergens of Aspergillus fumigatus in cystic fibrosis patients with ABPA

Abstract

Background: Aspergillus fumigatus, a widely distributed fungus, has been implicated in causing life threatening infections as well as severe asthma and allergic diseases in man. Allergic affliction like allergic bronchopulmonary aspergillosis (ABPA) is a disabling lung disease frequently seen in patients with asthma and cystic fibrosis. Immunodiagnosis of the former is comparatively easier due to the availability of purified antigens and sensitive methods. However, this is not true with cystic fibrosis patients where the prevalence of ABPA is fairly high and the morbidity and mortality are significant.

Methods: In the present study, we have evaluated purified recombinant allergens from A. fumigatus, namely Asp f 1, f 2, f 3, f 4, and f 6 using ELISA and a semi-automated method (ImmunoCAP). We studied 17 patients each from cystic fibrosis with ABPA, and cystic fibrosis with asthma, 22 cystic fibrosis with no ABPA or asthma, and 11 age matched controls.

Results: The results indicate that no antigen, antibody or method is capable of differentiating cystic fibrosis (CF) with ABPA from other CF patients, although some allergens showed strong reaction or showed more prevalence among the patients studied.

Conclusion: When results of several allergens such as Asp f 1, f 2, f 3, f 4, and f 6 in their binding to IgA, IgG, and IgE antibodies were analyzed, a more strong discrimination of CF patients with ABPA was possible from the other groups studied.

Figure 1

IgE antibodies against various recombinant allergens and crude Aspergillus extract. A. IgE measured by ImmunoCAP. B. IgE measured by ELISA.

Figure 2

IgA, IgA₁, IgA₂, IgG₁, IgG₂, IgG₃, and IgG₄ antibodies against crude Aspergillus fumigatus antigens and various recombinant allergens. A – A. fumigatus extract, B – Asp f 1, C – Asp f 2, D – Asp f 3, E – Asp f 4, and F – Asp f 16.

Figure 3

Scatter plot showing discriminant function analysis using IgE, IgA, and IgG antibody responses against Asp f 1, f 2, f 3, f 4, and f 6. Two different functions were analyzed and the results indicate good discrimination of the different groups. ■ normals, CF, X CF with atopy, ▲CF-ABPA patients, and □ the centroids of each group.