Analysis of Protein Sequence Identity, Binding Sites, and 3D Structures Identifies Eight Pollen Species and Ten Fruit Species with High Risk of Cross-Reactive Allergies

Abstract

Fruit allergens are proteins from fruits or pollen that cause allergy in humans, an increasing food safety concern worldwide. With the globalization of food trade and changing lifestyles and dietary habits, characterization and identification of these allergens are urgently needed to inform public awareness, diagnosis and treatment of allergies, drug design, as well as food standards and regulations. This study conducted a phylogenetic reconstruction and protein clustering among 60 fruit and pollen allergens from 19 species, and analyzed the clusters, in silico, for cross-reactivity (IgE), 3D protein structure prediction, transmembrane and signal peptides, and conserved domains and motifs. Herein, we wanted to predict the likelihood of their interaction with antibodies, as well as cross-reactivity between the many allergens derived from the same protein families, as the potential for cross-reactivity complicates the management of fruit allergies. Phylogenetic analysis classified the allergens into four clusters. The first cluster (n = 9) comprising pollen allergens showed a high risk of cross-reactivity between eight allergens, with Bet v1 conserved domain, but lacked a transmembrane helix and signal peptide. The second (n = 10) cluster similarly suggested a high risk of cross-reactivity among allergens, with Prolifin conserved domain. However, the group lacked a transmembrane helix and signal peptide. The third (n = 13) and fourth (n = 29) clusters comprised allergens with significant sequence diversity, predicted low risk of cross-reactivity, and showed both a transmembrane helix and signal peptide. These results are critical for treatment and drug design that mostly use transmembrane proteins as targets. The prediction of high risk of cross-reactivity indicates that it may be possible to design a generic drug that will be effective against the wide range of allergens. Therefore, in the past, we may have avoided the array of fruit species if one was allergic to any one member of the cluster.