Identification of B Cell Epitopes of Blo t 13 Allergen and Cross-Reactivity with Human Adipocytes and Heart Fatty Acid Binding Proteins

Abstract

Cross-reactivity between allergens and human proteins could have a clinical impact in allergic diseases. Blo t 13 is an allergen from the mite Blomia tropicalis, which belongs to the fatty acid binding protein (FABP) family and has structural homology with human FABPs. This work aimed to map B cell epitopes on Blo t 13 and to identify epitopes involved in cross-reactivity with human heart FABP (FABP3) and adipocyte FABP (FABP4). Sera from 25 patients with house dust mite (HDM) allergy that were sensitized to Blo t 13 were used for testing the reactivity of immunoglobulin E (IgE) and IgG to FABP. The epitope mapping of Blo t 13 was performed using overlapping peptides, and cross-reactivity between Blo t 13 and human FABP was analyzed using human sera and anti-Blo t 13 monoclonal antibodies. IgE antibodies to all FABPs were detected in 14/25 serum samples, and IgG was detected in 25/25 serum samples. The cross-reactivity of Blo t 13 was 42% with FABP3 and 48% with FABP4. Two IgE-binding regions were identified in Blo t 13; one between residues 54 and 72 (the main cross-reacting region) and another between residues 111 to 129. Our results suggest that exposure to the Blo t 13 allergen could induce an auto-reactive response to endogenous FABP in allergic patients sensitized to Blo t 13.

Clinical significance of dust mite allergens

“…Fatty acid binding. Cross-reactivity with Human Fatty acid binding protein and could induce an auto-reactive response [32].…”

“…That is, IgE mediated self-reactivity, thus aggravating allergic reactions to a certain extent. Therefore, special attention should be paid to the possible cross-reactions between the dust mite allergens component 13 and the human body's own proteins in clinical diagnosis [32].…”

Structural and allergenic properties of the fatty acid binding protein from shrimp Litopenaeus vannamei

“…The mAb 5G3 reacted with LvFABP, indicating that this allergen and Blo t 13 share an antigenic region, which can explain part of IgE reactivity as indicated by the inhibition assay using peptide five (Figure 3F). The mAb 5G3 binds to an epitope located in a region spanning residues 54 to 72 of Blo t 13 located in strands βD and βE, 23 and our sequence alignment revealed that this sequence is highly conserved between LvFABP and the FABP from HDM. ConSurf analysis supports that this region is involved in the cross‐reactivity between shrimp and B .…”

“…Epitope mapping was performed as indicated elsewhere 23,28 with modifications. One hundred µL of seven individual sera from shrimp allergic patients sensitized to LvFABP diluted 1:2, were preadsorbed with 150 µg/100 µL of each peptide.…”

“…Fractions containing eluted protein were pooled and dialyzed against 50 mM NaH 2 PO 4 and 0.5 M NaCl (pH 8.0). Blo t 13 was produced as indicated in reference 23 . Eluted protein was analyzed by SDS‐PAGE stained with Coomassie Brilliant Blue R‐250.…”