Allergenic Lipid Transfer Proteins from Plant-Derived Foods Do Not Immunologically and Clinically Behave Homogeneously: The Kiwifruit LTP as a Model

Abstract

BackgroundFood allergy is increasingly common worldwide. Tools for allergy diagnosis measuring IgE improved much since allergenic molecules and microarrays started to be used. IgE response toward allergens belonging to the same group of molecules has not been comprehensively explored using such approach yet.ObjectiveUsing the model of lipid transfer proteins (LTPs) from plants as allergens, including two new structures, we sought to define how heterogeneous is the behavior of homologous proteins.MethodsTwo new allergenic LTPs, Act d 10 and Act c 10, have been identified in green (Actinidia deliciosa) and gold (Actinidia chinensis) kiwifruit (KF), respectively, using clinically characterized allergic patients, and their biochemical features comparatively evaluated by means of amino acid sequence alignments. Along with other five LTPs from peach, mulberry, hazelnut, peanut, mugwort, KF LTPs, preliminary tested positive for IgE, have been immobilized on a microarray, used for IgE testing 1,003 allergic subjects. Comparative analysis has been carried out.ResultsAlignment of Act d 10 primary structure with the other allergenic LTPs shows amino acid identities to be in a narrow range between 40 and 55%, with a number of substitutions making the sequences quite different from each other. Although peach LTP dominates the IgE immune response in terms of prevalence, epitope recognition driven by sequence heterogeneity has been recorded to be distributed in a wide range of behaviors. KF LTPs IgE positive results were obtained in a patient subset IgE positive for the peach LTP. Anyhow, the negative results on homologous molecules allowed us to reintroduce KF in patients' diet.ConclusionThe biochemical nature of allergenic molecule belonging to a group of homologous ones should not be taken as proof of immunological recognition as well. The availability of panels of homologous molecules to be tested using microarrays is valuable to address the therapeutic intervention.

Kiwifruit as a food allergen source

“…Possible additional isoforms, suggested by elution profiles obtained during purification, were not identified probably because of the low yield. 72 MALDI-TOF mass spectrometry of purified nAct d 10 provided two mass values, 9.464 and 9.484 kDa, which are in good agreement with the values deduced from the amino acid sequence of the two isoforms having alanine (9.458 kDa) or threonine (9.488 kDa) as N-terminal residues, respectively. 72 Analysis by SDS-PAGE and RP-HPLC of LTP samples subjected to digestion in SGF showed that nAct c 10 and nAct d 10, similarly to nPru p 3, are resistant to gastric digestion.…”

“…72 Plant LTPs are widely distributed, structurally related, small proteins involved in defense mechanisms. Although their lipid binding ability has been well reported, the biological function of LTPs is still largely unknown.…”

“…Both proteins are present in seed extract, but not in pulp extract. 72 Direct protein sequencing of the purified protein allowed the KIWIFRUIT ALLERGENS 345 identification of two different isoforms of Act d 10. Possible additional isoforms, suggested by elution profiles obtained during purification, were not identified probably because of the low yield.…”

Lipid Transfer Protein Syndrome in a Non-Mediterranean Area

“…The kiwifruit is not a plant food that is commonly associated with LTP sensitization [8,14] in other series, although kiwifruit allergies with sensitization to its LTP Act d 10 have been reported in 22% of cases from Southern Europe [27]. Although the kiwifruit LTP seems to have slightly different properties than those of the classic LTPs [28], without overlooking the new and emerging kiwifruit allergens [29], we cannot dismiss the possibility that our patients reporting symptoms with kiwifruits could be sensitized to the LTP Act d 10. However, our data cannot draw any conclusions in this sense.…”

Bioanalytical Methods for Food Allergy Diagnosis, Allergen Detection and New Allergen Discovery

“…The described weaknesses of allergenomic strategies for new allergen identification lead to the necessity in the application of DNA-based techniques [115] or in Edman degradation performance for peptide sequencing [41,58,116,117,118]. It insures unequivocal identification of amino acid order in the peptide starting from the N-terminal residue and is typically realized in parallel with de novo sequencing [82][83][84].…”