Allergen content in German cockroach extracts and sensitization profiles to a new expanded set of cockroach allergens determine in vitro extract potency for IgE reactivity

Publication date: Available online 28 August 2018

Source: Journal of Allergy and Clinical Immunology

Author(s): J. Glesner, S. Filep, L.D. Vailes, S. Wünschmann, M.D. Chapman, G. Birrueta, A. Frazier, K.Y. Jeong, C. Schal, L. Bacharier, A. Beigelman, P. Busse, V. Schulten, A. Sette, A. Pomés

Abstract

Background

Cockroach allergens are an important cause of IgE-mediated sensitization in inner-city asthmatics. However, cockroach extracts used for diagnosis and immunotherapy are not standardized.

Objective

To determine the allergen content of non-standardized German cockroach extracts and the levels of sensitization to an expanded set of cockroach allergens as determinants of in vitro extract potency for IgE reactivity.

Methods

Twelve German cockroach extracts were compared for allergen content and for potency of IgE reactivity. Bla g 1, Bla g 2 and Bla g 5 were measured by immunoassays. IgE antibody levels to eight purified recombinant allergens from groups 1, 2, 4, 5, 6, 7, 9 and 11 were measured by ImmunoCAP. IgE antibody binding inhibition assays were performed to assess extract in vitro potencies (IC30) relative to an arbitrarily selected reference extract in five cockroach allergic subjects.

Results

Allergen levels were highly variable. Three new major allergens (groups 6, 9 and 11), were identified among highly cockroach-sensitized subjects (CAP-class ≥ 3). Sensitization profiles were unique per subject, without immunodominant allergens. The sum of IgE to eight allergen components showed a good correlation with cockroach-specific IgE (r = 0.88; p < 0.001). In vitro potencies varied among different extracts per subject, and among subjects for each extract.

Conclusions

The in vitro potency of German cockroach extracts for IgE reactivity depends on allergen content and allergen-specific IgE titers of the cockroach-allergic subject. These factors are relevant for selection of potent extracts to be used for immunotherapy and for the design and interpretation of data from immunotherapy trials.

Clinical Implications

Allergen content, variable in non-standardized German cockroach extracts, and IgE sensitization profiles to a new expanded set of cockroach allergens determine in vitro extract potency for IgE reactivity.

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