METHODS: Twelve German cockroach extracts were compared for content and potency of IgE reactivity. Levels of Bla g 1, Bla g 2, Bla g 5 and flagellin were measured by immunoassays. Endotoxin was measured by Limulus-Amebocyte-Lysate-test. IgE antibody levels to 7 purified recombinant allergens from groups 1, 2, 4, 5, 7, 9 and 11 were measured by ImmunoCAP. IgE antibody binding inhibition assays were performed to assess extract potency (IC30) in five cockroach allergic patients.
RESULTS: Endotoxin and allergen levels were highly variable (endotoxin: 45,118±98,472 EU/ml, Bla g 1: 39±47 μg/ml, Bla g 2: 17±20 μg/ml, and Bla g 5: 75±93 ng/ml). In addition to Bla g 2 and Bla g 5, two new major allergens (groups 9 and 11), were identified, with 50-63% IgE prevalences (n=16). Commercial extracts (5/9) showed the best potencies (IC30: 0.4-2.9 µg/ml). Within two groups of patients identified, good correlations of the IC30s between patient-pairs were observed (r >0.9), and the allergen-specific IgE levels correlated better than between two patients from different groups.
CONCLUSIONS: The potency of German cockroach extracts for IgE reactivity depends on allergen content and allergen-specific IgE titers of the cockroach allergic patient. These factors are relevant for the selection of potent extracts to be used for immunotherapy and the design and interpretation of data from immunotherapy trials.