Abstract
Blo t 21 is a paralogue of the group 5 allergen, Blo t 5, a major allergen from the dust mite Blomia tropicalis. Blo t 21 has moderate sequence identity (40.7%) to Blo t 5 and low to moderate cross-reactivity to Blo t 5. In B. tropicalis, the most prevalent and allergenic allergens are in the order of Blo t 21, Blo t 5, and Blo t 7. Here, we determined the NMR solution structure of Blo t 21, which represents the first structure of the group 21 dust mite allergen. The structure of Blo t 21 closely resembles the structures of Blo t 5 and Der p 5, comprising three anti-parallel α-helices arranged in a helical bundle. Using site-directed mutagenesis and specific IgE binding ELISA, Blo t 21 was found to contain both conserved and unique charged IgE epitope residues at the L2 loop region and on helix α3. Cross-inhibition assays confirmed that Blo t 21 has a low to moderate cross-reactivity with Blo t 5 and Der p 5 and represents a novel group of major allergen in B. tropicalis. In addition to group 5 allergens, Blo t 21 has also a low to moderate cross-reactivity with group 21 allergens from Dermatophagoides mites, confirming that B. tropicalis is a major and distinct source of dust mite allergens.
Highlights
Blo t 21 is a paralogue of the group 5 allergen with comparable allergenicity
Low to Moderate Cross-reactivity between Blo t 21, Blo t 5, and Der p 5—To confirm that Blo t 21 represents a novel group of dust mite allergens in B. tropicalis that is different from the group 5 allergens, we investigated the cross-reactivity of Blo t 21 with Blo t 5 and Der p 5 by cross-inhibition IgE binding assay using sera from six allergic patients
E.g., in patients P1 and P11, Blo t 21 could inhibit IgE binding to Der f 21 to a similar degree as Der f 21 inhibiting IgE binding to itself. These results suggest that, both Blo t 21 and Der f 21 belong to the group 21 allergen, they have only a low to moderate degree of cross-reactivity because they are from different species of dust mites
Summary
Blo t 21 is a paralogue of the group 5 allergen with comparable allergenicity. Results: Blo t 21 has an additional conformational IgE epitope and only a low to moderate cross-reactivity with Blo t 5. Conclusion: Blo t 21 represents a novel group of major allergen in the dust mite Blomia tropicalis. Cross-inhibition assays confirmed that Blo t 21 has a low to moderate cross-reactivity with Blo t 5 and Der p 5 and represents a novel group of major allergen in B. tropicalis. A low cross-reactivity between Der p 21 and the group 5 allergens was observed through IgE and IgG reactivity data and cross-inhibition studies [6] These findings suggest that Blo t 21 represents a novel group of. The crossreactivity of Blo t 21 with Blo t 5, Der p 5, and Der f 21 was low; this suggests that Blo t 21 represents a novel group of major allergens in B. tropicalis and should be included in further diagnostic and therapeutic studies of B. tropicalis-based allergies
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