Solution structure, copper binding and backbone dynamics of recombinant Ber e 1-the major allergen from Brazil nut

Food Allergens of Plant Origin

This review presents an update on the physical, chemical, and biological properties of food allergens in plant sources, focusing on the few protein families that contribute to multiple food allergens from different species and protein families recently found to contain food allergens. The structures and structural components of the food allergens in the allergen families may provide further directions for discovering new food allergens. Answers as to what makes some food proteins allergens are still elusive. Factors to be considered in mitigating food allergens include the abundance of the protein in a food, the property of short stretches of the sequence of the protein that may constitute linear IgE binding epitopes, the structural properties of the protein, its stability to heat and digestion, the food matrix the protein is in, and the antimicrobial activity to the microbial flora of the human gastrointestinal tract. Additionally, recent data suggest that widely used techniques for mapping linear IgE binding epitopes need to be improved by incorporating positive controls, and methodologies for mapping conformational IgE binding epitopes need to be developed.

Negative Thermal Expansion and Disorder-to-Order Collapse of an Intrinsically Disordered Protein under Marginally Denaturing Conditions

Recent work with intrinsically disordered proteins (IDPs) has projected a myriad of their survival instincts based mainly on the total charge content, the abundance of polar residues, and the paucity of hydrophobic amino acids. This work uses a plant IDP AtPP16-1 (Arabidopsis thaliana phloem protein class 16-1), whose solution NMR structure was determined by us recently, to show legitimate negative thermal expansion (NTE) of the native state. The thermal expansion continues to be negative even as the tertiary structure is perturbed by ultralow levels of urea up to 0.4 M. The NTE of these subdenatured states is called apparent NTE because they are prone to undergo conformational changes with temperature. Hydrodynamic shrinkage of the NTE IDP is also observed by dynamic light scattering (DLS) and NMR-measured global rotational correlation time (τ_c). The protein with denatured tertiary structure but otherwise preserved native-state secondary structure collapses to a dynamically rigid state. The data are mainly based on thermal coefficients of chemical shift and nuclear relaxation measured by heteronuclear NMR. The hydrodynamic shrinkage and collapse under marginally varying solvent compositions that may arise from unstable tertiary structure and dynamic disorder of chain segments across the backbone could be a generic property of IDPs.

Molecular Interactions Associated with Coagulation of Organic Pollutants by 2S Albumin of Plant Proteins: A Computational Approach

The removal of organic pollutants is a major challenge in wastewater treatment technologies. Coagulation by plant proteins is a promising technique for this purpose. The use of these proteins has been experimentally investigated and reported in the literature. However, the determination of the molecular interactions of these species is experimentally challenging and the computational approach offers a suitable alternative in gathering useful information for this system. The present study used a molecular dynamic simulation approach to predict the potentials of using Moringa oleifera (MO), Arachis hypogaea, Bertholletia excelsa, Brassica napus, and Helianthus annuus plant proteins for the coagulation of organic pollutants and the possible mechanisms of coagulation of these proteins. The results showed that the physicochemical and structural properties of the proteins are linked to their performance. Maximum coagulation of organic molecules to the proteins is between 50-100%. Among five proteins studied for coagulation, Brassica napus and Helianthus annuus performed better than the well-known MO protein. The amino acid residues interacting with the organic molecules play a significant role in the coagulation and this is peculiar with each plant protein. Hydrogen bond and π-interactions dominate throughout the protein-pollutants molecular interactions. The reusability of the proteins after coagulation derived from their structural quality analysis along with the complexes looks promising and most of them are better than that of the MO. The results showed that the seed proteins studied have good prediction potentials to be used for the coagulation of organic pollutants from the environment, as well as the insights into their molecular activities for bioremediation.

Characterization of Anti-Ana o 3 Monoclonal Antibodies and Their Application in Comparing Brazilian Cashew Cultivars

Ana o 3 is an immuno-dominant cashew nut allergen. Four monoclonal antibodies to Ana o 3 (2H5, 6B9C1, 19C9A2, and 5B7F8) were characterized by ELISA and in silico modeling. The 2H5 antibody was the only antibody specific for cashew nut extract. In addition to cashew nut extract, the 6B9C1 and 19C9A2 antibodies recognized pistachio extract, and the 5B7F8 recognized pecan extract. All four antibodies recognized both recombinant Ana o 3.0101 and native Ana o 3. ELISA assays following treatment of purified Ana o 3 with a reducing agent indicated that the 6B9C1 and 19C9A2 antibodies likely recognize conformational epitopes, while the 2H5 and 5B7F8 antibodies likely recognize linear epitopes. In silico modeling predicted distinct epitopes for each of the anti-Ana o 3 antibodies. Screening extracts from 11 Brazilian cashew nut cultivars using all four antibodies showed slight differences in Ana o 3 bindings, demonstrating that these antibodies could identify cultivars with varying allergen content.

Effect of O-linked glycosylation on the antigenicity, cellular uptake and trafficking in dendritic cells of recombinant Ber e 1

Ber e 1, a major Brazil nut allergen, has been successfully produced in the yeast Pichia pastoris expression system as homogenous recombinant Ber e 1 (rBer e 1) with similar physicochemical properties and identical immunoreactivity to its native counterpart, nBer e 1. However, O-linked glycans was detected on the P.pastoris-derived rBer e 1, which is not naturally present in nBer e 1, and may contribute to the allergic sensitisation. In this study, we addressed the glycosylation differences between P. pastoris-derived recombinant Ber e 1 and its native counterparts. We also determined whether this fungal glycosylation could affect the antigenicity and immunogenicity of the rBer e 1 by using dendritic cells (DC) as an immune cell model due to their role in modulating the immune response. We identified that the glycosylation occurs at Ser96, Ser101 and Ser110 on the large chain and Ser19 on the small polypeptide chain of rBer e 1 only. The glycosylation on rBer e 1 was shown to elicit varying degree of antigenicity by binding to different combination of human leukocyte antigens (HLA) at different frequencies compared to nBer e 1 when tested using human DC-T cell assay. However, both forms of Ber e 1 are weak immunogens based from their low response indexes (RI). Glycans present on rBer e 1 were shown to increase the efficiency of the protein recognition and internalization by murine bone marrow-derived dendritic cells (bmDC) via C-type lectin receptors, particularly the mannose receptor (MR), compared to the non-glycosylated nBer e 1 and SFA8, a weak allergenic 2S albumin protein from sunflower seed. Binding of glycosylated rBer e 1 to MR alone was found to not induce the production of IL-10 that modulates bmDC to polarise Th2 cell response by suppressing IL-12 production and DC maturation. Our findings suggest that the O-linked glycosylation by P. pastoris has a small but measurable effect on the in vitro antigenicity of the rBer e 1 compared to its non-glycosylated counterpart, nBer e 1, and thus may influence its applications in diagnostics and immunotherapy.

The importance of the 2S albumins for allergenicity and cross-reactivity of peanuts, tree nuts, and sesame seeds

Allergies to peanuts, tree nuts, and sesame seeds are among the most important food-related causes of anaphylaxis. Important clinical questions include: Why is there a variable occurrence of coallergy among these foods and Is this immunologically mediated? The clinical and immunologic data summarized here suggest an immunologic basis for these coallergies that is based on similarities among the 2S albumins. Data from component resolved diagnostics have highlighted the relationship between IgE binding to these allergens and the presence of IgE-mediated food allergy. Furthermore, in vitro and in vivo experiments provide strong evidence that the 2S albumins are the most important allergens in peanuts for inducing an allergic effector response. Although the 2S albumins are diverse, they have a common disulfide-linked core with similar physicochemical properties that make them prime candidates to explain much of the observed coallergy among peanuts, tree nuts, and sesame seeds. The well-established frequency of cashew and pistachio nut coallergy (64%-100%) highlights how the structural similarities among their 2S albumins may account for observed clinical cross-reactivity. A complete understanding of the physicochemical properties of the 2S albumins in peanuts, tree nuts, and sesame seeds will enhance our ability to diagnose, treat, and ultimately prevent these allergies.

IgE-Binding Epitopes of Pis v 1, Pis v 2 and Pis v 3, the Pistachio (Pistacia vera) Seed Allergens

Sequential IgE-binding epitopes were identified on the molecular surface of the Pis v 1 (2S albumin), Pis v 2 (11S globulin/legumin) and Pis v 3 (7S globulin/vicilin)—major allergens from pistachio (Pistacia vera) seeds—using the Spot technique. They essentially consist of hydrophilic and electropositively charged residues well exposed on the surface of the allergens. Most of the epitopic regions identified on Pis v 1 and Pis v 3 do not coincide with the putative N-glycosylation sites and thus are not considered as glycotopes. Surface analysis of these epitopic regions indicates a high degree of conformational similarity with the previously identified epitopic regions of the corresponding allergens Ana o 1 (vicilin), Ana o 2 (legumin) and Ana o 3 (2S albumin) from the cashew (Anacardium occidentale) nut. These results offer a molecular basis for the IgE-binding cross-reactivity often observed between pistachio and cashew nut. They support the recommendation for prescribing pistachio avoidance in cashew allergic patients. Other conformational similarities were identified with the corresponding allergens Ses i 1 (2S albumin), Ses i 3 (vicilin) and Ses i 6 (legumin) from sesame (Sesamum indicum), and Jug r 1 (2S albumin), Jug r 2 (vicilin) and Jug r 4 (legumin) from walnut (Juglans regia). Conversely, conformation of most of the epitopic regions of the pistachio allergens often differs from that of epitopes occurring on the molecular surface of the corresponding Ara h 1 (vicilin), Ara h 2 (2S albumin) and Ara h 3 (legumin) allergens from peanut (Arachis hypogaea).

Modeling to Understand Plant Protein Structure-Function Relationships-Implications for Seed Storage Proteins

Proteins are among the most important molecules on Earth. Their structure and aggregation behavior are key to their functionality in living organisms and in protein-rich products. Innovations, such as increased computer size and power, together with novel simulation tools have improved our understanding of protein structure-function relationships. This review focuses on various proteins present in plants and modeling tools that can be applied to better understand protein structures and their relationship to functionality, with particular emphasis on plant storage proteins. Modeling of plant proteins is increasing, but less than 9% of deposits in the Research Collaboratory for Structural Bioinformatics Protein Data Bank come from plant proteins. Although, similar tools are applied as in other proteins, modeling of plant proteins is lagging behind and innovative methods are rarely used. Molecular dynamics and molecular docking are commonly used to evaluate differences in forms or mutants, and the impact on functionality. Modeling tools have also been used to describe the photosynthetic machinery and its electron transfer reactions. Storage proteins, especially in large and intrinsically disordered prolamins and glutelins, have been significantly less well-described using modeling. These proteins aggregate during processing and form large polymers that correlate with functionality. The resulting structure-function relationships are important for processed storage proteins, so modeling and simulation studies, using up-to-date models, algorithms, and computer tools are essential for obtaining a better understanding of these relationships.

Towards a surrogate system to express human lipid binding TCRs

BACKGROUND

Previously we reported that natural nut lipids were necessary for sensitization and that natural killer T cells (NKTs) must play a critical role in the development of food allergic responses. A major bottleneck in further understanding the interaction of nut lipids with the cells of the human immune system is the lack of well-characterized lipid responsive human cell lines.

OBJECTIVE

In the present study, we engineered human T cell receptor (TCR) sequences TRAV10 and TRBV25 responsive to α-GalCer into a stable murine iNKT hybridoma and surrogate human T cell lines.

RESULTS

The murine hybridoma system has shown to be problematic. To overcome this limitation, the expression of human TCR α/β sequences has been achieved driven by a bidirectional promoter on a plasmids or a lentivirus system, employing stable DC cell lines as lipid presenting cells, and a stable T cell line as a surrogate system. Further, a commercial human Jurkat T cell line containing an inducible secreted luciferase reporter construct was shown to be functional and can be used for a transient expression of human TCRs in a lipid screening program. The transfection efficiencies were improved using the lentivirus polycistronic constructs containing the P2A sequence in a TCR αβ/γδ null cell line (Jurkat 76).

CONCLUSIONS

The results suggest that the mis-pairing of the endogenous α/β TCR during ER folding in the presence of the new human TCR sequences could be impairing the functionality of the TCR lipid receptors. The surrogate systems presented here are important first steps in the establishment of human cell-specific lipid responsive libraries for the study of natural lipid substances.

Tree nut allergens

Tree nuts are considered as part of a healthy diet due to their high nutritional quality. However, they are also a potent source of allergenic proteins inducing IgE mediated hypersensitivity often causing serious, life-threatening reactions. The reported prevalence of tree nut allergy is up to 4.9% worldwide. The general term "tree nuts" comprises a number of nuts, seeds, and drupes, derived from trees from different botanical families. For hazelnut and walnut several allergens have been identified which are already partly applied in component resolved diagnosis, while for other tree nuts such as macadamia, coconut, and Brazil nut only individual allergens were identified and data on additional allergenic proteins are missing. This review summarizes the current knowledge on tree nut allergens and describes their physicochemical and immunological characterization and clinical relevance.

Recombinant Allergen Production in E. coli

Recombinant protein allergens have been used in allergy studies, allergy diagnosis, and epitope mapping. Messenger RNAs (mRNAs) are isolated from tissues of interest for complementary DNA (cDNA) library construction. Subsequently, the allergen gene is amplified by polymerase chain reaction (PCR) and sequenced. The amplified gene is then cloned into an expression vector, expressed in Escherichia coli cells, and purified from the cell lysate. This chapter describes the protocols for recombinant allergen production.

Two proteins for the price of one: Structural studies of the dual-destiny protein preproalbumin with sunflower trypsin inhibitor-1

Seed storage proteins are both an important source of nutrition for humans and essential for seedling establishment. Interestingly, unusual napin-type 2S seed storage albumin precursors in sunflowers contain a sequence that is released as a macrocyclic peptide during post-translational processing. The mechanism by which such peptides emerge from linear precursor proteins has received increased attention; however, the structural characterization of intact precursor proteins has been limited. Here, we report the 3D NMR structure of the Helianthus annuus PawS1 (preproalbumin with sunflower trypsin inhibitor-1) and provide new insights into the processing of this remarkable dual-destiny protein. In seeds, PawS1 is matured by asparaginyl endopeptidases (AEPs) into the cyclic peptide SFTI-1 (sunflower trypsin inhibitor-1) and a heterodimeric 2S albumin. The structure of PawS1 revealed that SFTI-1 and the albumin are independently folded into well-defined domains separated by a flexible linker. PawS1 was cleaved in vitro with recombinant sunflower HaAEP1 and in situ using a sunflower seed extract in a way that resembled the expected in vivo cleavages. Recombinant HaAEP1 cleaved PawS1 at multiple positions, and in situ, its flexible linker was removed, yielding fully mature heterodimeric albumin. Liberation and cyclization of SFTI-1, however, was inefficient, suggesting that specific seed conditions or components may be required for in vivo biosynthesis of SFTI-1. In summary, this study has revealed the 3D structure of a macrocyclic precursor protein and provided important mechanistic insights into the maturation of sunflower proalbumins into an albumin and a macrocyclic peptide.

Efficient production of (2)H, (13)C, (15)N-enriched industrial enzyme Rhizopus chinensis lipase with native disulfide bonds

BACKGROUND

In order to use most modern methods of NMR spectroscopy to study protein structure and dynamics, isotope-enriched protein samples are essential. Especially for larger proteins (>20 kDa), perdeuterated and Ile (δ1), Leu, and Val methyl-protonated protein samples are required for suppressing nuclear relaxation to provide improved spectral quality, allowing key backbone and side chain resonance assignments needed for protein structure and dynamics studies. Escherichia coli and Pichia pastoris are two of the most popular expression systems for producing isotope-enriched, recombinant protein samples for NMR investigations. The P. pastoris system can be used to produce (13)C, (15)N-enriched and even (2)H,(13)C, (15)N-enriched protein samples, but efficient methods for producing perdeuterated proteins with Ile (δ1), Leu and Val methyl-protonated groups in P. pastoris are still unavailable. Glycosylation heterogeneity also provides challenges to NMR studies. E. coli expression systems are efficient for overexpressing perdeuterated and Ile (δ1), Leu, Val methyl-protonated protein samples, but are generally not successful for producing secreted eukaryotic proteins with native disulfide bonds.

RESULTS

The 33 kDa protein-Rhizopus chinensis lipase (RCL), an important industrial enzyme, was produced using both P. pastoris and E. coli BL21 trxB (DE3) systems. Samples produced from both systems exhibit identical native disulfide bond formation and similar 2D NMR spectra, indicating similar native protein folding. The yield of (13)C, (15)N-enriched r27RCL produced using P. pastoris was 1.7 times higher that obtained using E. coli, while the isotope-labeling efficiency was ~15 % lower. Protein samples produced in P. pastoris exhibit O-glycosylation, while the protein samples produced in E. coli were not glycosylated. The specific activity of r27RCL from P. pastoris was ~1.4 times higher than that produced in E. coli.

CONCLUSIONS

These data demonstrate efficient production of (2)H, (13)C, (15)N-enriched, Ile (δ1), Leu, Val methyl-protonated eukaryotic protein r27RCL with native disulfides using the E. coli BL21 trxB (DE3) system. For certain NMR studies, particularly efforts for resonance assignments, structural studies, and dynamic studies, E. coli provides a cost-effective system for producing isotope-enriched RCL. It should also be potential for producing other (2)H, (13)C, (15)N-enriched, Ile (δ1), Leu, Val methyl-protonated eukaryotic proteins with native disulfide bonds.

Purification and characterization of 2S albumin from Nelumbo nucifera

The 2S albumins are a group of seed storage proteins that have recently attracted considerable attention in the field of allergen science due to their allergenic potential. A new 2S albumin from seeds of Nelumbo nucifera (Nn-2S alb) was purified to electrophoretic homogeneity by the combination of ammonium sulfate fractionation, gel filtration, and ion exchange chromatography. The protein has a molecular mass of about 12 kDa estimated by SDS-PAGE, in good agreement with 12.5 ± 0.01 kDa determined by ESI-MS. Circular dichroism data showed that protein contained about 66% α-helices as estimated by K2D3, indicating that the protein was predominantly helical. The sedimentation coefficient (s°_20,w) of the predicted model was 1.72 ± 0.21 S. The predicted 3-dimensional structure of the Nn-2S alb revealed that the protein has a region of 12 amino acids which largely corresponds to the conserved immuno-dominant epitope of 2S allergens.

Molecular characterization of the puroindoline-a and b alleles in synthetic hexaploid wheats and in silico functional and structural insights into Pina-D1

Kernel hardness determined by two tightly linked Puroindoline genes, Pina-D1 and Pinb-D1, located on chromosome 5DS define commercially important characteristics, uses, major grades and export markets of wheat. This study was conducted to characterize Pina-D1 and Pinb-D1 alleles, in fifteen synthetic hexaploid wheats (SHWs) and its relation with grain hardness. Additionally, in silico functional analyses of puroindoline-a protein was conducted for better understanding of their putative importance in grain quality. Six different Pina-D1 alleles were identified in the SHWs, of which three i.e. Pina-D1a, Pina-D1c and Pina-D1d were already known whereas the other three had new sequence polymorphisms and were designated as Pina-D1w, Pina-D1x and Pina-D1y. Three different Pinb-D1 alleles were identified which have been reported earlier and no novel sequence polymorphism was detected. It was concluded that despite some primary, secondary and 3D structure variations, ligand binding sites and disulfide bonds discrepancies, the main features of PINA, i.e. the tryptophan-rich domain, the cysteine backbone, the signal peptide and basic identity of the proteins were all conserved. In silico analysis showed that puroindolines having binding capacity with small parts of prolamins causing celiac disease of human, however their potential role is not obvious. Conclusively, the new Pina-D1 alleles with modest effect on grain hardness, and insight into their functional and structural characteristics are important findings and their putative role in celiac disease require further studies to validate.

The Flocculating Cationic Polypetide from Moringa oleifera Seeds Damages Bacterial Cell Membranes by Causing Membrane Fusion

A cationic protein isolated from the seeds of the Moringa oleifera tree has been extensively studied for use in water treatment in developing countries and has been proposed for use in antimicrobial and therapeutic applications. However, the molecular basis for the antimicrobial action of this peptide, Moringa oleifera cationic protein (MOCP), has not been previously elucidated. We demonstrate here that a dominant mechanism of MOCP antimicrobial activity is membrane fusion. We used a combination of cryogenic electron microscopy (cryo-EM) and fluorescence assays to observe and study the kinetics of fusion of membranes in liposomes representing model microbial cells. We also conducted cryo-EM experiments on E. coli cells where MOCP was seen to fuse the inner and outer membranes. Coarse-grained molecular dynamics simulations of membrane vesicles with MOCP molecules were used to elucidate steps in peptide adsorption, stalk formation, and fusion between membranes.

Mo-CBP3, an antifungal chitin-binding protein from Moringa oleifera seeds, is a member of the 2S albumin family

Mo-CBP3 is a chitin-binding protein from M. oleifera seeds that inhibits the germination and mycelial growth of phytopathogenic fungi. This protein is highly thermostable and resistant to pH changes, and therefore may be useful in the development of new antifungal drugs. However, the relationship of MoCBP3 with the known families of carbohydrate-binding domains has not been established. In the present study, full-length cDNAs encoding 4 isoforms of Mo-CBP3 (Mo-CBP3-1, Mo-CBP3-2, Mo-CBP3-3 and Mo-CBP3-4) were cloned from developing seeds. The polypeptides encoded by the Mo-CBP3 cDNAs were predicted to contain 160 (Mo-CBP3-3) and 163 amino acid residues (Mo-CBP3-1, Mo-CBP3-2 and Mo-CBP3-4) with a signal peptide of 20-residues at the N-terminal region. A comparative analysis of the deduced amino acid sequences revealed that Mo-CBP3 is a typical member of the 2S albumin family, as shown by the presence of an eight-cysteine motif, which is a characteristic feature of the prolamin superfamily. Furthermore, mass spectrometry analysis demonstrated that Mo-CBP3 is a mixture of isoforms that correspond to different mRNA products. The identification of Mo-CBP3 as a genuine member of the 2S albumin family reinforces the hypothesis that these seed storage proteins are involved in plant defense. Moreover, the chitin-binding ability of Mo-CBP3 reveals a novel functionality for a typical 2S albumin.

Molecular Dynamics of Major Allergens from Alternaria, Birch Pollen and Peach

In the search for factors that make a protein allergenic (an issue that remains so far elusive) some common features of allergens such as small size, high stability and lipid binding are recognized in spite of their structural diversity. Other relevant but still poorly understood feature is their capability to form homodimers. We investigated by means of Molecular Dynamics (MD) calculations the stability in solution of several dimers of three major allergens from Alternaria mold, birch pollen, and peach fruit known to play essential roles in allergic disease. By running 20 ns MD simulations we found essential properties on solution that provide information of interest on their dimerization, stability of their epitopes and dynamical features of ligand binding cavities. Our results show that three essential allergen proteins display a distinct behavior on their trends to form homodimers in solution.

Seed storage albumins: biosynthesis, trafficking and structures

Seed storage albumins are water-soluble and highly abundant proteins that are broken-down during seed germination to provide nitrogen and sulfur for the developing seedling. During seed maturation these proteins are subject to post-translational modifications and trafficking before they are deposited in great quantity and with great stability in dedicated vacuoles. This review will cover the subcellular movement, biochemical processing and mature structures of seed storage napins.

Do lipids influence the allergic sensitization process?

Allergic sensitization is a multifactorial process that is not only influenced by the allergen and its biological function per se but also by other small molecular compounds, such as lipids, that are directly bound as ligands by the allergen or are present in the allergen source. Several members of major allergen families bind lipid ligands through hydrophobic cavities or electrostatic or hydrophobic interactions. These allergens include certain seed storage proteins, Bet v 1–like and nonspecific lipid transfer proteins from pollens and fruits, certain inhalant allergens from house dust mites and cockroaches, and lipocalins. Lipids from the pollen coat and furry animals and the so-called pollen-associated lipid mediators are codelivered with the allergens and can modulate the immune responses of predisposed subjects by interacting with the innate immune system and invariant natural killer T cells. In addition, lipids originating from bacterial members of the pollen microbiome contribute to the outcome of the sensitization process. Dietary lipids act as adjuvants and might skew the immune response toward a T_H2-dominated phenotype. In addition, the association with lipids protects food allergens from gastrointestinal degradation and facilitates their uptake by intestinal cells. These findings will have a major influence on how allergic sensitization will be viewed and studied in the future.

Structure of allergens and structure based epitope predictions

The structure determination of major allergens is a prerequisite for analyzing surface exposed areas of the allergen and for mapping conformational epitopes. These may be determined by experimental methods including crystallographic and NMR-based approaches or predicted by computational methods. In this review we summarize the existing structural information on allergens and their classification in protein fold families. The currently available allergen-antibody complexes are described and the experimentally obtained epitopes compared. Furthermore we discuss established methods for linear and conformational epitope mapping, putting special emphasis on a recently developed approach, which uses the structural similarity of proteins in combination with the experimental cross-reactivity data for epitope prediction.

Lipids are required for the development of Brazil nut allergy: the role of mouse and human iNKT cells

BACKGROUND

Lipids are required for mice sensitization to Ber e 1, Brazil nut major allergen. Here, we characterized different lipid fractions extracted from Brazil nuts and the lipid-binding ability of Ber e 1. Further, we determined their in vivo ability to induce Ber-specific anaphylactic antibodies and the role of invariant natural killer T (iNKT) cells in this process.

METHODS

Wild-type (WT) and iNKT cell-deficient mice were sensitized with Ber e 1 and specific lipid fractions, and anaphylactic antibodies were measured by enzyme-linked immunosorbent assay (ELISA) and passive cutaneous anaphylaxis (PCA). The lipid-binding characteristic of Ber e 1 (Ber) was established by using fluorescent probes and (15) N-labeled NMR. In vitro production of IL-4 was determined in Ber/lipid C-stimulated mouse iNKT cells and human T-cell lines containing NKTs primed with CD1d+C1R transfectants by flow cytometry and ELISA, respectively.

RESULTS

Only one specific lipid fraction (lipid C), containing neutral and common phospholipids, induced Ber anaphylactic antibodies in mice. Ber e 1 has a lipid-binding site, and our results indicated an interaction between Ber e 1 and lipid C. iNKT-deficient mice produced lower levels of anaphylactic antibodies than WT mice. In vitro, Ber/lipid C-stimulated murine iNKT cells produced IL-4 but not IFN-gamma. Human T-cell lines derived from nut-allergic patients produced IL-4 to Ber/lipid C in a CD1d- and dose-dependent manner.

CONCLUSION

Lipid fraction C from Brazil nut presents an essential adjuvant activity to Ber e 1 sensitization, and iNKT cells play a critical role in the development of Brazil nut-allergic response.