Structural, Serological, and Genomic Analyses of the Major Mite Allergen Der p 23

Rationale: Der p 23 was recently identified in a European population as a major allergen and potentially a chitin binding protein.  This study sought to determine the structure of Der p 23, and assess the importance of Der p 23 among other Dermatophagoides allergens in a North American population.

Methods: The structure was analyzed by X-ray crystallography and NMR. 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. Allergen expression levels were estimated using RNA-seq data from D. farinae.

Results: Der p 23 is a small, globular protein, stabilized by two disulfide bonds, that is structurally related to allergens that contain carbohydrate binding domains such as Blo t 12.   Functional assays failed to confirm chitin binding by Der p 23. Despite a high prevalence of Der p 23, (83% versus 87% and 85% for Der p 1 and Der p 2, respectively), the anti-Der p 23 IgE levels were relatively low. The RNA expression level of Der f 23 is the lowest of the major allergens.  Expression levels of Dermatophagoides allergens do not correlate with their reported prevalence of IgE sensitization. 

Conclusions: 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 other more abundant Dermatophagoides allergens.