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Background-Sensitization to house dust mite allergens is strongly correlated with asthma. Der p 7 elicits strong IgE antibody and T-cell responses in mite allergic patients. However, the structure and biological function of this important allergen are unknown. Allergen function may contribute to allergenicity as shown for the protease activity of Group 1 mite allergens and the interaction with the innate immune system by Group 2 mite allergens.

Background Der p 23 was recently identified in a European population as a major allergen and potentially a chitin binding protein. Objective This study sought to assess the importance of Der p 23 among other Dermatophagoides allergens in a North American population, and to determine the structure for functional characterization. Methods IgE binding to Der p 23, Der p 1, Der p 2, Der p 5, Der p 7, and Der p 8 was measured by ELISA. RNA-seq data from D. pteronyssinus were compared as estimates of allergen expression levels. The structure was analyzed by X-ray crystallography and NMR. Results Despite a high prevalence of Der p 23, (75% versus 87% and 79% for Der p 1 and Der p 2, respectively), the anti-Der p 23 IgE levels were relatively low. The patient response to the 6 allergens tested was variable (n=47), but on average anti-Der p 1 and anti-Der p 2 together accounted for 85% of the specific IgE. In terms of abundance, the RNA expression level of Der p 23 is the lowest of the major allergens, 30-fold less than and 7-fold less than Der p 2. The structure of Der p 23 is a small, globular protein stabilized by two disulfide bonds, which is structurally related to allergens such as Blo t 12 that contain carbohydrate binding domains that bind chitin. Functional assays failed to confirm chitin binding by Der p 23. Conclusions and Clinical Relevance Der p 23 accounts for a small percentage of the IgE response to mite allergens, which is dominated by Der p 1 and Der p 2. The prevalence and amount of specific IgE to Der p 23 and Der p 2 are disproportionately high compared to the expressions of other Dermatophagoides allergens.

Background Sensitization to cockroach allergens is a major risk factor for asthma. The cockroach allergen Bla g 1 has multiple repeats of ~100 amino acids, but the fold of the protein and the biological function are unknown. Objective To determine the structure of Bla g 1, investigate the implications for allergic disease, and standardize cockroach exposure assays. Methods Natural Bla g 1 and recombinant constructs were compared by ELISA using specific murine IgG and human IgE. The structure of Bla g 1 was determined by X-ray crystallography. Mass spectrometry and NMR were utilized to examine ligand-binding properties of the allergen. Results The structure of a recombinant Bla g 1 construct with comparable IgE and IgG reactivity to the natural allergen was solved by X-ray crystallography. The Bla g 1 repeat forms a novel fold with 6 helices. Two repeats encapsulate a large and nearly spherical hydrophobic cavity, defining the basic structural unit. Lipids in the cavity varied depending on the allergen origin. Palmitic, oleic and stearic acids were associated with nBla g 1 from cockroach frass. One Unit of Bla g 1 was equivalent to 104 ng of allergen. Conclusions Bla g 1 has a novel fold with a capacity to bind various lipids, which suggests a digestive function associated with non-specific transport of lipid molecules in cockroaches. Defining the basic structural unit of Bla g 1 facilitates the standardization of assays in absolute units for the assessment of environmental allergen exposure.

The in vitro potency of German cockroach extracts for IgE reactivity depends on allergen content and allergen-specific IgE titers of patients with cockroach allergy. 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.