Group 10 allergens (tropomyosins) from house-dust mites may cause covariation of sensitization to allergens from other invertebrates

Abstract

Group 10 allergens (tropomyosins) have been assumed to be a major cause of cross-reactivity between house-dust mites (HDMs) and other invertebrates. Despite all of the published data regarding the epidemiology, percent IgE binding and level of sensitization in the population, the role of tropomyosin as a cross-reactive allergen in patients with multiple allergy syndrome still remains to be elucidated. Homology between amino acid sequences reported in allergen databases of selected invertebrate tropomyosins was determined with Der f 10 as the reference allergen. The 66.9 and 54.4% identities were found with selected crustacean and insect species, respectively, whereas only 20.4% identity was seen with mollusks. A similar analysis was performed using reported B-cell IgE-binding epitopes from Met e1 (shrimp allergen) and Bla g7 (cockroach allergen) with other invertebrate tropomyosins. The percent identity in linear sequences was higher than 35% in mites, crustaceans, and cockroaches. The polar and hydrophobic regions in these groups were highly conserved. These findings suggest that tropomyosin may be a major cause of covariation of sensitization between HDMs, crustaceans, and some species of insects and mollusks.

Keywords: Cross-reactivity of tropomyosins; HDM allergens; IgE-binding epitopes; group 10 allergens; homology; multiple allergy syndrome; tropomyosins.

Figure 1.

Amino acid sequence alignment: comparison of Der f 10 allergen with major group 10 allergens from mite species using the clustalo algorithm. With 240 identical (*), 26 conserved (:) and 6 semiconserved (.) positions the identity is 84.2% (UniProt FASTA). For abbreviations refer to Appendix A.

Figure 2.

Phylogenetic tree based on aligned tropomyosin proteins from invertebrates. For abbreviations, see Appendix A.

Figure 3.

Amino acid sequence alignment: comparison of Der f 10 and Der p 10 allergens with major tropomyosin allergens from crustacean species using the clustalo algorithm. With 190 identical (*), 37 conserved (:), and 7 semiconserved (.) positions the identity is 66.9% (UniProt FASTA). For abbreviations, see Appendix A.

Figure 4.

Amino acid sequence alignment: comparison of Der f 10 and Der p 10 allergens with major tropomyosin allergens from insect species using the clustalo algorithm. With 155 identical (*), 60 conserved (:), and 16 semiconserved (.) positions the identity is 54.4% (UniProt FASTA). For abbreviations, see Appendix A.

Figure 5.

Amino acid sequence alignment: comparison of Der f 10 and Der p 10 allergens with major tropomyosin allergens from mollusk species using the clustalo algorithm. With 58 identical (*), 36 conserved (:), and 7 semiconserved (.) positions the identity is 20.4% (UniProt FASTA). For abbreviations, see Appendix A.

Figure 6.

IgE-binding epitope (peptide 1, 47–63, and peptide 2, 150–158) from Met e 1 aligned with species of invertebrates (a, mites; b, crustacea; c, mollusks; and d, insects). Conserved polar regions have been highlighted (UniProt FASTA). For abbreviations, see Appendix A.

Figure 7.

Analysis of IgE-binding epitopes of Bla g 7 (Blatella germanica tropomyosin) with selected invertebrate species. Conserved polar regions have been highlighted (UniProt FASTA). For abbreviations, see Appendix A.