Are Physicochemical Properties Shaping the Allergenic Potency of Plant Allergens?

This review searched for published evidence that could explain how different physicochemical properties impact on the allergenicity of food proteins and if their effects would follow specific patterns among distinct protein families. Owing to the amount and complexity of the collected information, this literature overview was divided in two articles, the current one dedicated to protein families of plant allergens and a second one focused on animal allergens. Our extensive analysis of the available literature revealed that physicochemical characteristics had consistent effects on protein allergenicity for allergens belonging to the same protein family. For example, protein aggregation contributes to increased allergenicity of 2S albumins, while for legumins and cereal prolamins, the same phenomenon leads to a reduction. Molecular stability, related to structural resistance to heat and proteolysis, was identified as the most common feature promoting plant protein allergenicity, although it fails to explain the potency of some unstable allergens (e.g. pollen-related food allergens). Furthermore, data on physicochemical characteristics translating into clinical effects are limited, mainly because most studies are focused on in vitro IgE binding. Clinical data assessing how these parameters affect the development and clinical manifestation of allergies is minimal, with only few reports evaluating the sensitising capacity of modified proteins (addressing different physicochemical properties) in murine allergy models. In vivo testing of modified pure proteins by SPT or DBPCFC is scarce. At this stage, a systematic approach to link the physicochemical properties with clinical plant allergenicity in real-life scenarios is still missing.

Peptide Glycodendrimers as Potential Vaccines for Olive Pollen Allergy.

Olive pollen is one of the most important causes of respiratory allergy, with Ole e 1 being the most clinically relevant sensitizing allergen. Peptide-based vaccines represent promising therapeutic approaches, but the use of adjuvants is required to strengthen the weak immunogenicity of small peptides. We propose the use of dendrimeric scaffolds conjugated to the T cell immunodominant epitope of Ole e 1 (OE109-130) for the development of novel vaccines against olive pollen allergy. Four dendrimeric scaffolds containing an ester/ether with nine mannoses, an ester succinimidyl linker with nine N-acetyl-glucosamine units or nine ethylene glycol units conjugated to OE109-130 peptide were designed, and their cytotoxicity, internalization pattern, and immunomodulatory properties were analyzed in vitro. None of the dendrimers exhibited cytotoxicity in humanized rat basophil (RBL-2H3), human bronchial epithelial Calu-3, and human mast LAD2 cell lines. Confocal images indicated that mannosylated glycodendropeptides exhibited lower colocalization with a lysosomal marker. Moreover, mannosylated glycodendropeptides showed higher transport tendency through the epithelial barrier formed by Calu-3 cells cultured at the air-liquid interface. Finally, mannosylated glycodendropeptides promoted Treg and IL10+Treg proliferation and IL-10 secretion by peripheral blood mononuclear cells from allergic patients. Mannosylated dendrimers conjugated with OE109-130 peptide from Ole e 1 have been identified as suitable candidates for the development of novel vaccines of olive pollen allergy.

New insights into the sensitization to nonspecific lipid transfer proteins from pollen and food: New role of allergen Ole e 7.

BACKGROUND: Ole e 7 is a nonspecific lipid transfer protein (nsLTP) from olive pollen, one of the main allergenic pollens worldwide. This allergenic nsLTP is responsible for severe symptoms in regions with high olive pollen exposure, where many Ole e 7-sensitized patients exhibit a co-sensitization to the peach nsLTP, Pru p 3. However, there is no evidence of cross-reactivity, which explains this observed co-sensitization. Therefore, the purpose of this study was to explore the relationship between Ole e 7 and Pru p 3. METHODS: A total of 48 patients sensitized to Ole e 7 and/or Pru p 3 were included in the study. Specific IgE serum levels were measured by ImmunoCAP 250 and ELISA. Inhibition assays were performed to determine the existence of cross-reactivity between both nsLTPs. Allergic response was analyzed ex vivo (basophil activation test) and in vitro (RBL-2H3 mast cell model). RESULTS: Common IgG and IgE epitopes were identified between both allergens. IgE-binding inhibition was detected in Ole e 7-monosensitized patients using rPru p 3 as inhibitor, reaching inhibition values of 25 and 100%. Ex vivo and in vitro assays revealed a response against rPru p 3 in four (31%) Ole e 7-monosensitized patients. CONCLUSIONS: Our results suggest that Ole e 7 could play a new role as primary sensitizer in regions with high olive pollen exposure, leading to the peach nsLTP sensitization. This co-sensitization process would occur because of the cross-reactivity between Ole e 7 and Pru p 3 observed in some allergic patients.

Delineation of the Olive Pollen Proteome and Its Allergenome Unmasks Cyclophilin as a Relevant Cross-Reactive Allergen.

Olive pollen is a major allergenic source worldwide due to its extensive cultivation. We have combined available genomics data with a comprehensive proteomics approach to get the annotated olive tree (Olea europaea L.) pollen proteome and define its complex allergenome. A total of 1907 proteins were identified by LC-MS/MS using predicted protein sequences from its genome. Most proteins (60%) were predicted to possess catalytic activity and be involved in metabolic processes. In total, 203 proteins belonging to 47 allergen families were found in olive pollen. A peptidyl-prolyl cis-trans isomerase, cyclophilin, produced in Escherichia coli, was found as a new olive pollen allergen (Ole e 15). Most Ole e 15-sensitized patients were children (63%) and showed strong IgE recognition to the allergen. Ole e 15 shared high sequence identity with other plant, animal, and fungal cyclophilins and presented high IgE cross-reactivity with pollen, plant food, and animal extracts.

Allium porrum Extract Decreases Effector Cell Degranulation and Modulates Airway Epithelial Cell Function.

Allium genus plants, such as leek (Allium porrum), are rich sources of anti-inflammatory and anti-oxidant secondary metabolites; this is of interest because it demonstrates their suitability as pharmacological alternatives for inflammatory processes, including allergy treatment. The composition of methanolic leek extract (LE) was analyzed by GC-MS and LC-IT/MS, and the total phenolic content and antioxidant capacity were quantified by colorimetric methods. Its pharmacological potential was analyzed in human bronchial epithelial Calu-3 cells, human mast cells LAD2, and humanized rat basophiles RBL-2H3. LE exhibited a cytotoxic effect on Calu-3 cells and HumRBL-2H3 cells only at high concentrations and in a dose-dependent manner. Moreover, LE decreased the degranulation of LAD2 and HumRBL-2H3 cells. LE treatment also significantly prevented alterations in transepithelial electrical resistance values and mRNA levels of glutathione-S-transferase (GST), c-Jun, and NFκB after treatment with H2O2 in ALI-cultured Calu-3 cells. Finally, ALI-cultured Calu-3 cells treated with LE showed lower permeability to Ole e 1 compared to untreated cells. A reduction in IL-6 secretion in ALI-cultured Calu-3 cells treated with LE was also observed. In summary, the results obtained in this work suggest that A. porrum extract may have potential anti-allergic effects due to its antioxidant and anti-inflammatory properties. This study provides several important insights into how LE can protect against allergy.

Profilin-mediated food-induced allergic reactions are associated with oral epithelial remodeling.

BACKGROUND: In areas of high exposure to grass pollen, allergic patients are frequently sensitized to profilin, and some experience severe profilin-mediated food-induced reactions. This specific population of patients is ideal to study the relationship between respiratory and food allergies. OBJECTIVE: We sought to determine the role of oral mucosal epithelial barrier integrity in profilin-mediated allergic reactions. METHODS: Thirty-eight patients with profilin allergy stratified into mild or severe according to their clinical history and response to a profilin challenge test and 6 nonallergic subjects were recruited. Oral mucosal biopsies were used for measurement of CD11c, CD3, CD4, tryptase, claudin-1, occludin, E-cadherin, and vascular endothelial growth factor A levels; Masson trichrome staining; and POSTN, IL33, TPSAB, TPSB, and CMA gene expression analysis by using quantitative RT-PCR. Blood samples were used for basophil activation tests. RESULTS: Distinct features of the group with severe allergy included the following: (1) impaired epithelial integrity with reduced expression of claudin-1, occludin, and E-cadherin and decreased numbers of epithelial cells, which is indicative of acanthosis, higher collagen deposition, and angiogenesis; (2) inflammatory immune response in the mucosa, with an increased number of CD11c+ and CD4+ infiltrates and increased expression of the cytokine genes POSTN and IL33; and (3) a 10-fold increased sensitivity of basophils to profilin. CONCLUSIONS: Patients with profilin allergy present with significant damage to the oral mucosal epithelial barrier, which might allow profilin penetration into the oral mucosa and induction of local inflammation. Additionally, severely allergic patients presented with increased sensitivity of effector cells.

A recombinant isoform of the Ole e 7 olive pollen allergen assembled by de novo mass spectrometry retains the allergenic ability of the natural allergen.

The allergenic non-specific lipid transfer protein Ole e 7 from olive pollen is a major allergen associated with severe symptoms in areas with high olive pollen levels. Despite its clinical importance, its cloning and recombinant production has been unable by classical approaches. This study aimed at determining by mass-spectrometry based proteomics its complete amino acid sequence for its subsequent expression and characterization. To this end, the natural protein was in-2D-gel tryptic digested, and CID and HCD fragmentation spectra obtained by nLC-MS/MS analyzed using PEAKS software. Thirteen out of the 457 de novo sequenced peptides obtained allowed assembling its full-length amino acid sequence. Then, Ole e 7-encoding cDNA was synthesized and cloned in pPICZαA vector for its expression in Pichia pastoris yeast. The analyses by Circular Dichroism, and WB, ELISA and cell-based tests using sera and blood from olive pollen-sensitized patients showed that rOle e 7 mostly retained the structural, allergenic and antigenic properties of the natural allergen. In summary, rOle e 7 allergen assembled by de novo peptide sequencing by MS behaved immunologically similar to the natural allergen scarcely isolated from pollen. SIGNIFICANCE: Olive pollen is an important cause of allergy. The non-specific lipid binding protein Ole e 7 is a major allergen with a high incidence and a phenotype associated to severe clinical symptoms. Despite its relevance, its cloning and recombinant expression has been unable by classical techniques. Here, we have inferred the primary amino acid sequence of Ole e 7 by mass-spectrometry. We separated Ole e 7 isolated from pollen by 2DE. After in-gel digestion with trypsin and a direct analysis by nLC-MS/MS in an LTQ-Orbitrap Velos, we got the complete de novo sequenced peptides repertoire that allowed the assembling of the primary sequence of Ole e 7. After its protein expression, purification to homogeneity, and structural and immunological characterization using sera from olive pollen allergic patients and cell-based assays, we observed that the recombinant allergen retained the antigenic and allergenic properties of the natural allergen. Collectively, we show that the recombinant protein assembled by proteomics would be suitable for a better in vitro diagnosis of olive pollen allergic patients.