In Silico Identification and in Vitro Analysis of B and T-Cell Epitopes of the Black Turtle Bean (Phaseolus Vulgaris L.) Lectin

Abstract

Background/Aims: The incidence of lectin allergic disease is increasing in recent decades, and definitive treatment is still lacking. Identification of B and T-cell epitopes of allergen will be useful in understanding the allergen antibody responses as well as aiding in the development of new diagnostics and therapy regimens for lectin poisoning. In the current study, we mainly addressed these questions. Methods: Three-dimensional structure of the lectin from black turtle bean (Phaseolus vulgaris L.) was modeled using the structural template of Phytohemagglutinin from P. vulgaris (PHA-E, PDB ID: 3wcs.1.A) with high identity. The B and T-cell epitopes were screened and identified by immunoinformatics and subsequently validated by ELISA, lymphocyte proliferation and cytokine profile analyses. Results: Seven potential B-cell epitopes (B1 to B7) were identified by sequence and structure based methods, while three T-cell epitopes (T1 to T3) were identified by the predictions of binding score and inhibitory concentration. The epitope peptides were synthesized. Significant IgE binding capability was found in B-cell epitopes (B2, B5, B6 and B7) and T2 (a cryptic B-cell epitope). T1 and T2 induced significant lymphoproliferation, and the release of IL-4 and IL-5 cytokine confirmed the validity of T-cell epitope prediction. Abundant hydrophobic amino acids were found in B-cell epitope and T-cell epitope regions by amino acid analysis. Positively charged amino acids, such as His residue, might be more favored for B-cell epitope. Conclusion: The present approach can be applied for the identification of epitopes in novel allergen proteins and thus for designing diagnostics and therapies in lectin allergy.

Prediction and characterization of the T cell epitopes for the major soybean protein allergens using bioinformatics approaches

“…Allergen-specific T cells play an important role in allergic reactions and are obvious targets for immunotherapy intervention in diseases [17]. Recently, Candreva et al [46] developed a new strategy for preventing milk allergy on the basis of oral administration of a soybean-derived peptide that was cross-reactive with bovine caseins.…”

“…The amino acid composition of T cell epitopes and the frequency were analyzed according to the methods of He et al [17] and Zheng et al [25].…”

“…In this context, bioinformatics has been applied as an initial screening methoda and widely used in the prediction of food allergen epitopes with advantages including high throughput, fast analysis speed, and low cost, benefiting from database development [16]. In our previous studies, seven different bioinformatics tools, ProPred, SYF-PEITHI, NetMHCII, NN-align, SMM-align, NetMHCIIpan and RANKPEP, were employed to predict the T cell epitopes of a black kidney bean, from which two of three potential T cell epitopes were confirmed using cytokine and lymphocyte proliferation experiments [17], suggesting the prediction accuracy of bioinformatics analysis. Besides, thirty-six T cell epitopes of the peanut allergen Ara h 1 were obtained by NetMHCIIpan 2.0 tool, and 14 of predicted T cell epitopes binded to HLA molecules in vitro , and 35 of T cell epitopes induced T cell proliferation differentiation and the production of IL13 [14].…”

Are Dietary Lectins Relevant Allergens in Plant Food Allergy?

“…Each protomer contains a CBS that specifically recognizes complex N-glycan chains, but does not recognize simple sugars, probably due to a particular conformation of the CBS. Both types of lectins from the white kidney bean [29,[54][55][56][57][58] and the black turtle bean [59,60] have been reported as allergens, and a detailed bioinformatics study of the B-and T-cell epitopes of PHA-E from black turtle bean has been performed [59]. Up to 7 IgE-binding B-epitopes (Figure 2B) and 3 T-epitopes (Figure 3) occur at the surface of the PHA-E tetramer.…”

“…To date, however, the immunogenicity of lectins as allergenic proteins remains poorly known and difficult to foresee, because of the lack of information on the T-cell epitopes in these proteins. Except for PHA-E from black turtle bean [59], no information on the number and distribution of T epitopes is available for other potentially allergenic lectins. However, some information has been collected on the location and distribution of IgE-binding B-cell epitopic regions on the surface of a few lectins, especially legume lectins.…”