Rationally designed hypoallergenic mutant variants of the house dust mite allergen Der p 21

Allergic diseases figure among the most common immune-mediated diseases worldwide, affecting more than 25% of the world's population. Allergic reactions can be triggered by house dust mite (HDM) allergens, of which the so-called group 21 of allergens is considered as clinically relevant. Herein, we used a structural bioinformatics and immunoinformatics approach to design hypoallergenic mutant variants of the Der p 21 allergen of Dermatophagoides pteronyssinus, which were then recombinantly expressed in bacteria and tested for their IgE-reactivities. For this, we scanned the wild-type Der p 21 protein for all possible single amino acid substitutions in key IgE-binding regions that could render destabilization of the major epitope regions. Four main substitutions (D82P, K110G, E77G, and E87S) were selected to build mutant variants of the Der p 21 allergen, which were produced in their recombinant forms; two of these variants showed reduced reactivity with IgE. Molecular dynamic simulations and immune simulations demonstrated the overall effects of these mutations on the structural stability of the Der p 21 allergen and on the profile of immune response induced through immunotherapy. When produced in their recombinant forms, two of the Der p 21 mutant variants, namely proteins K110G and E87S, showed significantly reduced IgE reactivities against sera from HDM-allergic individuals (n = 20; p