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Background: Phospholipases are enzymes with the capacity to hydrolyze membrane lipids and have been characterized in several allergenic sources, such as hymenoptera species. However, cross-reactivity among phospholipases allergens are little understood. The objective of this study was to determine potential antigenic regions involved in cross-reactivity among allergens of phospholipases using an in silico approach. Methods: In total, 18 amino acids sequences belonging to phospholipase family derived from species of the order hymenoptera were retrieved from the UniProt database to perform phylogenetic analysis to determine the closest molecular relationship. Multialignment was done to identify conserved regions and matched with antigenic regions predicted by ElliPro server. 3D models were obtained from modeling by homology and were used to locate cross-reactive antigenic regions. Results: Phylogenetic analysis showed that the 18 phospholipases split into four monophyletic clades (named here as A, B, C and D). Phospholipases from A clade shared an amino acid sequences’ identity of 79%. Antigenic patches predicted by Ellipro were located in highly conserved regions, suggesting that they could be involved in cross-reactivity in this group (Ves v 1, Ves a 1 and Ves m 1). Conclusions: At this point, we advanced to the characterization of potential antigenic sites involved in cross-reactivity among phospholipases. Inhibition assays are needed to confirm our finding.

Background: Lipocalins play a role in the cellular trafficking of pheromones and are involved in allergic responses to domestic pets. However, the cross-reactivity among allergens of this group has been poorly explored, and the pheromone linking capacity is not well characterized. The aim of this study was to explore cross-reactive epitopes and pheromone linking capacity among Rat n 1 and homologues in domestic pets through an in silico approach. Methods: ElliPro and BepiPred in silico tools were used to predict B cell linear and cross-reactive epitopes. The pheromone linking capacity was explored by docking virtual screening with 2-ethylhexanol, 2,5-dimethylpyrazine, 2-sec-butyl-4,5-dihydrothiazole, and 2-heptanone ligands. Results: According to the analysis, Rat n 1 shares 52% identity with Equ c 1, Can f 6, Fel d 4, and Mus m 1 allergens. The overlapping structures assay revealed high structural homology (root mean square deviation < 1). Four lineal and three discontinuous epitopes were predicted on Ra t n 1. A lineal epitope located between amino acids residues 24 and 36 was highly conserved on all allergens explored. A cross-reactive discontinuous epitope (T142, K143, D144, L145, S146, S147, D148, K152, L170, T171, T173, D174) was also found. Docking molecular simulations revealed the active site, and we identified the properties of the binding of four pheromones and the binding potential of Rat n 1. Critical residues for interactions are reported in this study. Conclusions: We identified some possible allergens from Rattus norvegicus, and those allergens could have cross-reactivity with allergens from some animals. The results need to be confirmed with in vitro studies and could be utilized to contribute to immunotherapy and reduce allergic diseases related to lipocalins.

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Lipocalins are one of the groups of allergens derived from domestic animals with clinical importance for the development of allergic responses. They have been characterized in different animals. With allergenic capacity characterized, little is known about the epitopes involved in allergic responses. Here, potential antigenic regions involved in cross-reactivity among lipocalins were explored through bioinformatics tools. The amino acid sequences of several lipocalins from different domestic animals (mouse, dog, cat, bull, hamster, horse and pig) were used to determine the degree of kinship by phylogenetic studies. Groups with highest phylogenetic relation were obtained by using MEGA software. 3D models of lipocalins not reported in the protein data bank were modeled by homology to identify potential antigenic regions compromised in the cross-reactivity of this group of allergens. The alignment of the entire database of allergenic lipocalins and the inferred maximum likelihood tree segregate lipocalins into five monophyletic clades (referenced here as A, B, C, D and E). According to the multiple pairing analyzes, group C (Fel d 4, Rat n 1 and Equ c 1) showed the highest degree of identity among their amino acid sequences (58%). The analysis of conserved and exposed residues showed that group C shares three antigenic regions that could potentially contribute to its cross-reactivity. Potential antigenic sites were identified for the generation of cross-reactivity between the different lipocalins analyzed in this study. These studies support the need to carry out directed mutagenesis tests to confirm their relevance in the allergenic capacity of lipocalins.