Serological analysis of sensitization in allergic bronchopulmonary aspergillosis: a study on allergen components and interspecies relationships

Background: Serological testing for immunoglobulin (Ig) E or IgG is useful for diagnosing allergic bronchopulmonary aspergillosis (ABPA), as it detects type I and III allergic reactions to Aspergillus species. However, few reports have investigated the allergen component and cross-reactivity among Aspergillus species. We aimed to measure and analyze the levels of IgGs specific to each Aspergillus species and investigate the prevalence of IgEs specific to each allergen component of A. fumigatus (Af) in ABPA patients. Methods: Serum samples were collected from 12 ABPA patients who visited our hospital between February and December 2017, and 16 with Af-sensitized asthma and 41 with Af-unsensitized asthma were controls. Immuno-CAP was performed to analyze the IgEs and IgGs specific to Af, A. niger, A flavus and A. terreus, and IgEs specific to allergen components Asp f 1, 2, 3, 4 and 6. Results: The ABPA group was significantly more frequently sensitized to Asp f 1 and 2 than the control groups. Af-specific IgEs were significantly positively correlated to the IgEs specific to A. flavus, A. niger and A. terreus. Af-specific IgGs were positively correlated to the IgGs specific to all the other species. Conclusions: Tests using allergen components were useful for ABPA diagnosis. Both IgE and IgG were highly cross-reactive among the Aspergillus species. There were many patients apart from asthmatic patients with ABPA, who displayed high Aspergillus IgG values.