Molecular characterization and allergenic activity of Lyc e 2 (beta-fructofuranosidase), a glycosylated allergen of tomato

The role of glycosylation in clinical allergy and immunology

While glycans are among the most abundant macromolecules on the cell with widespread functions, their role in immunity has historically been challenging to study. This is in part due to difficulties assimilating glycan analysis into routine approaches used to interrogate immune cell function. Despite this, recent developments have illuminated fundamental roles for glycans in host immunity. The growing field of glycoimmunology continues to leverage new tools and approaches to uncover the function of glycans and glycan-binding proteins in immunity. Here we utilize clinical vignettes to examine key roles of glycosylation in allergy, inborn errors of immunity, and autoimmunity. We will discuss the diverse functions of glycans as epitopes, as modulators of antibody function, and as regulators of immune cell function. Finally, we will highlight immune modulatory therapies that harness the critical role of glycans in the immune system.

Tomato Allergy: The Characterization of the Selected Allergens and Antioxidants of Tomato (Solanum lycopersicum)-A Review

Tomatoes are one of the most broadly produced and consumed crop plants. They are the source of health-promoting nutrients such as antioxidants, including ascorbic acid, polyphenols, or carotenoids. Despite the beneficial role of tomatoes in the daily diet, they have been confirmed as one of the most prevalent allergenic vegetables. Food allergies can cause many clinical symptoms, e.g., in the gastrointestinal tract, skin, and lungs, as well as anaphylactic shock. A huge amount of clinical research has been carried out to improve the understanding of the immunological mechanisms that lead to the lack of tolerance of food antigens, which can result in either immunoglobulin E (IgE)-mediated reactions or non-IgE-mediated reactions. Lifestyle and diet play an important role in triggering food allergies. Allergy to tomatoes is also linked to other allergies, such as grass pollen and latex allergy. Numerous attempts have been made to identify and characterize tomato allergens; however, the data available on the subject are not sufficient.

Carbohydrate epitopes currently recognized as targets for IgE antibodies

Until recently, glycan epitopes have not been documented by the WHO/IUIS Allergen Nomenclature Sub-Committee. This was in part due to scarce or incomplete information on these oligosaccharides, but also due to the widely held opinion that IgE to these epitopes had little or no relevance to allergic symptoms. Most IgE-binding glycans recognized up to 2008 were considered to be "classical" cross-reactive carbohydrate determinants (CCD) that occur in insects, some helminths and throughout the plant kingdom. Since 2008, the prevailing opinion on lack of clinical relevance of IgE-binding glycans has been subject to a reevaluation. This was because IgE specific for the mammalian disaccharide galactose-alpha-1,3-galactose (alpha-gal) was identified as a cause of delayed anaphylaxis to mammalian meat in the United States, an observation that has been confirmed by allergists in many parts of the world. Several experimental studies have shown that oligosaccharides with one or more terminal alpha-gal epitopes can be attached as a hapten to many different mammalian proteins or lipids. The classical CCDs also behave like haptens since they can be expressed on proteins from multiple species. This is the explanation for extensive in vitro cross-reactivity related to CCDs. Because of these developments, the Allergen Nomenclature Sub-Committee recently decided to include glycans as potentially allergenic epitopes in an adjunct section of its website (www.allergen.org). In this article, the features of the main glycan groups known to be involved in IgE recognition are revisited, and their characteristic structural, functional, and clinical features are discussed.

IgE-Reactivity Pattern of Tomato Seed and Peel Nonspecific Lipid-Transfer Proteins after in Vitro Gastrointestinal Digestion

The influence of gastrointestinal digestion on the immunological properties of three different nonspecific lipid-transfer proteins (nsLTPs) described in tomato fruit has been assessed using an in vitro system mimicking the stomach and intestine digestion conditions. Tomato peel/pulp nsLTP, Sola l 3, was degraded after digestion, although the immunoglobulin E (IgE) recognition of intact protein and a 10 kDa band were still observed after 30 min of duodenal digestion in the presence of phosphatidylcholine. The tomato seed nsLTP, Sola l 7, showed a higher stability than the other seed allergen, Sola l 6, during digestion. Sola l 7 showed an IgE immunoreactive 6.5 kDa band in immunoblotting analysis, retaining up to 7% of its IgE-binding capacity in inhibition ELISA test after 60 min of duodenal digestion and keeping intact its ability to activate basophils after digestion. These results suggest that the tomato seed allergen Sola l 7 might be considered as an important allergen in the induction of allergic responses to tomato due to its high stability against gastrointestinal digestion.

Cross-reactive carbohydrate determinant-specific IgE obscures true atopy and exhibits ⍺-1,3-fucose epitope-specific inverse associations with asthma

Background

In high-income, temperate countries, IgE to allergen extracts is a risk factor for, and mediator of, allergy-related diseases (ARDs). In the tropics, positive IgE tests are also prevalent, but rarely associated with ARD. Instead, IgE responses to ubiquitous cross-reactive carbohydrate determinants (CCDs) on plant, insect and parasite glycoproteins, rather than to established major allergens, are dominant. Because anti-CCD IgE has limited clinical relevance, it may impact ARD phenotyping and assessment of contribution of atopy to ARD.

Methods

Using an allergen extract-based test, a glycan and an allergen (glyco)protein microarray, we mapped IgE fine specificity among Ugandan rural Schistosoma mansoni (Sm)-endemic communities, proximate urban communities, and importantly in asthmatic and nonasthmatic schoolchildren.

Results

Overall, IgE sensitization to extracts was highly prevalent (43%-73%) but allergen arrays indicated that this was not attributable to established major allergenic components of the extracts (0%-36%); instead, over 40% of all participants recognized CCD-bearing components. Using glycan arrays, we dissected IgE responses to specific glycan moieties and found that reactivity to classical CCD epitopes (core β-1,2-xylose, α-1,3-fucose) was positively associated with sensitization to extracts, rural environment and Sm infection, but not with skin reactivity to extracts or sensitization to their major allergenic components. Interestingly, we discovered that reactivity to only a subset of core α-1,3-fucose-carrying N-glycans was inversely associated with asthma.

Conclusions

CCD reactivity is not just an epiphenomenon of parasite exposure hampering specificity of allergy diagnostics; mechanistic studies should investigate whether specific CCD moieties identified here are implicated in the protective effect of certain environmental exposures against asthma.

High-Yield Production of the Major Birch Pollen Allergen Bet v 1 With Allergen Immunogenicity in Nicotiana benthamiana

Type I allergy is an immunological disorder triggered by allergens and causes significant health problems. The major allergen of birch pollen is Bet v 1, which belongs to the pathogen-related protein 10 (PR-10) family. Here, we established a rapid and robust method for the production of Bet v 1 in Nicotiana benthamiana leaves, with binding activity to allergic patients' IgE. The Bet v 1 allergen was expressed in N. benthamiana using a strong agroinfiltration-based transient protein expression system, which consists of a deconstructed geminiviral vector system with a double terminator. Five days post-infiltration, the allergen concentration in N. benthamiana leaves was 1.2 mg/g of fresh mass, being this the maximum yield of Bet v 1 in plants reported up to now. A part of plant-derived Bet v 1 was glycosylated. Bet v 1 purified from N. benthamiana or Brevibacillus brevis was used to carry out enzyme-linked immunoassays; both recombinant allergens were found to have comparable binding properties to the IgE of allergic patients. These results suggest that our plant expression system allows rapid and robust production of the allergen, which keeps the immunogenicity.

Pollen food allergy syndrome to tomato in mountain cedar pollen hypersensitivity

BACKGROUND

Mountain cedar pollen is recognized as a major cause of seasonal hypersensitivity in the US. We describe here that a subgroup of these patients also suffer from pollen food allergy syndrome (PFAS).

OBJECTIVE

We performed this study to determine the frequency of PFAS among patients with mountain cedar hypersensitivity.

METHODS

We performed mail-out/telephone surveys of 800 mountain cedar-sensitive patients in Austin, TX. The subjects for this survey were selected by telephone screening, and skin and serologic testing. We performed immunoblot inhibition assay and mass spectrometry (MS) to identify the allergens that cause PFAS.

RESULTS

Of the 28 patients with suspected food allergies, 15 had clinical manifestations of PFAS. Eleven of them had positive skin tests to tomato, six to banana, and one to apple. The subjects with PFAS have stronger cutaneous and in vitro reactivity to cedar pollen. The intensities of the tomato and banana reactivity were correlated with the cedar reactivity. The results of the ImmunoCAP inhibition experiments demonstrated a strong cross-reactivity between IgE antibodies to cedar pollen and fruits. This suggested that their primary sensitization was to cedar pollen, since absorption with cedar pollen extract strongly inhibited reactivity to each of the fruits, while the absorption with tomato extract did not significantly inhibit IgE binding to cedar extract. We determined that polygalacturonase 2 A (PG2 A) in tomato is the cause of PFAS.

CONCLUSION

This is the first report of a PFAS in patients with mountain cedar pollinosis. Sensitivity to tomato, banana, and apple should be considered in cedar-sensitive patients.

Beneficial effects and potential risks of tomato consumption for human health: An overview

Tomato and its derived products have a very interesting nutritional value in addition to prominent antioxidant, anti-inflammatory, and anticancer activities. Tomatoes are generally quite safe to eat. However, overall consumption varies from individual to individual. Indeed, either beneficial or harmful effects of plants or their derived products are closely related to quality, including the presence of biologically active compounds. On the other hand, the synthesis and accumulation of these bioactive molecules depends on many other factors, such as environmental conditions. In this sense, this review briefly highlights the relationship between the chemistry of tomato and its derived products and their beneficial or harmful effects on human health, such as gastroesophageal reflux disease or heartburn, allergies, kidney and cardiovascular disorders, prostate cancer, irritable bowel syndrome, lycopenodermia, body aches, arthritis, and urinary problems.

Multivariate Analysis of MALDI Imaging Mass Spectrometry Data of Mixtures of Single Pollen Grains

Mixtures of pollen grains of three different species (Corylus avellana, Alnus cordata, and Pinus sylvestris) were investigated by matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-TOF imaging MS). The amount of pollen grains was reduced stepwise from > 10 to single pollen grains. For sample pretreatment, we modified a previously applied approach, where any additional extraction steps were omitted. Our results show that characteristic pollen MALDI mass spectra can be obtained from a single pollen grain, which is the prerequisite for a reliable pollen classification in practical applications. MALDI imaging of laterally resolved pollen grains provides additional information by reducing the complexity of the MS spectra of mixtures, where frequently peak discrimination is observed. Combined with multivariate statistical analyses, such as principal component analysis (PCA), our approach offers the chance for a fast and reliable identification of individual pollen grains by mass spectrometry. Graphical Abstract ᅟ.

Identification of a polygalacturonase (Cup s 2) as the major CCD-bearing allergen in Cupressus sempervirens pollen

As IgE glyco-epitopes, also referred to as cross-reactive carbohydrate determinants (CCDs), can share significant structural homologies between different plants, they are prone to extensive cross-reactivity among allergen pollen extracts. Here, cypress pollen allergens, especially a polygalacturonase (PG), were further characterized using double one-dimensional electrophoresis (D1-DE). The presence of specific IgE directed against CCDs was investigated by bromelain IgE inhibition and concanavalin A binding assays using sera of cypress pollen-sensitized patients. Our results showed that IgE reactivity to CCDs in Cupressus sempervirens pollen extracts is mainly related to bromelain-type epitopes of a newly identified cypress PG. This glycoprotein has been further characterized through an immunoproteomic approach and officially indexed as Cup s 2 by the WHO/IUIS allergen nomenclature. Cup s 2 could thus be associated with the increased prevalence of IgE reactivity to cypress pollen extracts because of CCD interference.

Glycans and glycan-specific IgE in clinical and molecular allergology: Sensitization, diagnostics, and clinical symptoms

Glycan-specific IgE antibodies cross-react with highly similar or even identical carbohydrate structures on a variety of different natural allergens, the so-called cross-reactive carbohydrate determinants (CCDs). In clinical practice CCDs often interfere with the specificity of in vitro allergy diagnostics, thus impairing allergy therapy decisions for individual patients. Strikingly, these IgE antibodies directed against CCDs often do not cause clinically relevant allergy symptoms. On the other hand, the IgE-binding glycan allergen galactose-α-(1,3)-galactose (α-Gal) is associated with IgE-mediated delayed anaphylaxis in meat allergy. The reason for this discrepancy is not known. The discovery of α-Gal stimulated new discussions and investigations regarding the relevance of anti-glycan IgE for allergic diseases. In this review the effect of glycans and glycan-specific IgE on sensitization to allergens and allergy diagnosis is described. Because parasite infections elicit a similar immunologic environment as allergic diseases, the association of glycan-specific antibodies against parasite glycoproteins with glycan structures on allergens is discussed.

A plant-derived quadrivalent virus like particle influenza vaccine induces cross-reactive antibody and T cell response in healthy adults

Recent issues regarding efficacy of influenza vaccines have re-emphasized the need of new approaches to face this major public health issue. In a phase 1-2 clinical trial, healthy adults received one intramuscular dose of a seasonal influenza plant-based quadrivalent virus-like particle (QVLP) vaccine or placebo. The hemagglutination inhibition (HI) titers met all the European licensure criteria for the type A influenza strains at the 3μg/strain dose and for all four strains at the higher dosages 21days after immunization. High HI titers were maintained for most of the strains 6months after vaccination. QVLP vaccine induced a substantial and sustained increase of hemagglutinin-specific polyfunctional CD4 T cells, mainly transitional memory and TEMRA effector IFN-γ(+) CD4 T cells. A T cells cross-reactive response was also observed against A/Hong-Kong/1/1968 H3N2 and B/Massachusetts/2/2012. Plant-based QVLP offers an attractive alternative manufacturing method for producing effective and HA-strain matching seasonal influenza vaccines.

Emerging roles of protein mannosylation in inflammation and infection

Proteins are frequently modified by complex carbohydrates (glycans) that play central roles in maintaining the structural and functional integrity of cells and tissues in humans and lower organisms. Mannose forms an essential building block of protein glycosylation, and its functional involvement as components of larger and diverse α-mannosidic glycoepitopes in important intra- and intercellular glycoimmunological processes is gaining recognition. With a focus on the mannose-rich asparagine (N-linked) glycosylation type, this review summarises the increasing volume of literature covering human and non-human protein mannosylation, including their structures, biosynthesis and spatiotemporal expression. The review also covers their known interactions with specialised host and microbial mannose-recognising C-type lectin receptors (mrCLRs) and antibodies (mrAbs) during inflammation and pathogen infection. Advances in molecular mapping technologies have recently revealed novel immuno-centric mannose-terminating truncated N-glycans, termed paucimannosylation, on human proteins. The cellular presentation of α-mannosidic glycoepitopes on N-glycoproteins appears tightly regulated; α-mannose determinants are relative rare glycoepitopes in physiological extracellular environments, but may be actively secreted or leaked from cells to transmit potent signals when required. Simultaneously, our understanding of the molecular basis on the recognition of mannosidic epitopes by mrCLRs including DC-SIGN, mannose receptor, mannose binding lectin and mrAb is rapidly advancing, together with the functional implications of these interactions in facilitating an effective immune response during physiological and pathophysiological conditions. Ultimately, deciphering these complex mannose-based receptor-ligand interactions at the detailed molecular level will significantly advance our understanding of immunological disorders and infectious diseases, promoting the development of future therapeutics to improve patient clinical outcomes.

AllergenOnline: A peer-reviewed, curated allergen database to assess novel food proteins for potential cross-reactivity

SCOPE

Increasingly regulators are demanding evaluation of potential allergenicity of foods prior to marketing. Primary risks are the transfer of allergens or potentially cross-reactive proteins into new foods. AllergenOnline was developed in 2005 as a peer-reviewed bioinformatics platform to evaluate risks of new dietary proteins in genetically modified organisms (GMO) and novel foods.

METHODS AND RESULTS

The process used to identify suspected allergens and evaluate the evidence of allergenicity was refined between 2010 and 2015. Candidate proteins are identified from the NCBI database using keyword searches, the WHO/IUIS nomenclature database and peer reviewed publications. Criteria to classify proteins as allergens are described. Characteristics of the protein, the source and human subjects, test methods and results are evaluated by our expert panel and archived. Food, inhalant, salivary, venom, and contact allergens are included. Users access allergen sequences through links to the NCBI database and relevant references are listed online. Version 16 includes 1956 sequences from 778 taxonomic-protein groups that are accepted with evidence of allergic serum IgE-binding and/or biological activity.

CONCLUSION

AllergenOnline provides a useful peer-reviewed tool for identifying the primary potential risks of allergy for GMOs and novel foods based on criteria described by the Codex Alimentarius Commission (2003).

Allergenic Potential of Tomatoes Cultivated in Organic and Conventional Systems

Tomatoes (Lycopersicon esculentum Mill.) are a widely consumed vegetables and contain many health beneficial micronutrients. Unfortunately, they may also cause adverse allergic reactions in sensitized people. Many studies, conducted in recent years, indicate that organically produced vegetables have higher nutritional value, improved sensory quality and contain more health-enhancing bioactive compounds than vegetables grown under the conventional system. However, the relation between organic methods of cultivation and allergenic potential of tomatoes has received little scientific attention. This study analyzed samples of five tomato cultivars taken from organic and conventional systems over three consecutive years. The content of profilin, Bet v 1 and lipid transfer protein (LTP) analogues in tomato samples was determined using an indirect ELISA assay. Substantial quantities of these proteins were found in certain cultivars across all three years of cultivation. On the basis of these findings, organically grown tomatoes appear to offer little advantage over conventionally cultivated plants in terms of reduced allergenic potential.

Mining Novel Allergens from Coconut Pollen Employing Manual De Novo Sequencing and Homology-Driven Proteomics

Coconut pollen, one of the major palm pollen grains is an important constituent among vectors of inhalant allergens in India and a major sensitizer for respiratory allergy in susceptible patients. To gain insight into its allergenic components, pollen proteins were analyzed by two-dimensional electrophoresis, immunoblotted with coconut pollen sensitive patient sera, followed by mass spectrometry of IgE reactive proteins. Coconut being largely unsequenced, a proteomic workflow has been devised that combines the conventional database-dependent analysis of tandem mass spectral data and manual de novo sequencing followed by a homology-based search for identifying the allergenic proteins. N-terminal acetylation helped to distinguish "b" ions from others, facilitating reliable sequencing. This led to the identification of 12 allergenic proteins. Cluster analysis with individual patient sera recognized vicilin-like protein as a major allergen, which was purified to assess its in vitro allergenicity and then partially sequenced. Other IgE-sensitive spots showed significant homology with well-known allergenic proteins such as 11S globulin, enolase, and isoflavone reductase along with a few which are reported as novel allergens. The allergens identified can be used as potential candidates to develop hypoallergenic vaccines, to design specific immunotherapy trials, and to enrich the repertoire of existing IgE reactive proteins.

Clinical Safety and Immunogenicity of Tumor-Targeted, Plant-Made Id-KLH Conjugate Vaccines for Follicular Lymphoma

We report the first evaluation of plant-made conjugate vaccines for targeted treatment of B-cell follicular lymphoma (FL) in a Phase I safety and immunogenicity clinical study. Each recombinant personalized immunogen consisted of a tumor-derived, plant-produced idiotypic antibody (Ab) hybrid comprising the hypervariable regions of the tumor-associated light and heavy Ab chains, genetically grafted onto a common human IgG1 scaffold. Each immunogen was produced in Nicotiana benthamiana plants using twin magnICON vectors expressing the light and heavy chains of the idiotypic Ab. Each purified Ab was chemically linked to the carrier protein keyhole limpet hemocyanin (KLH) to form a conjugate vaccine. The vaccines were administered to FL patients over a series of ≥6 subcutaneous injections in conjunction with the adjuvant Leukine (GM-CSF). The 27 patients enrolled in the study had previously received non-anti-CD20 cytoreductive therapy followed by ≥4 months of immune recovery prior to first vaccination. Of 11 patients who became evaluable at study conclusion, 82% (9/11) displayed a vaccine-induced, idiotype-specific cellular and/or humoral immune response. No patients showed serious adverse events (SAE) related to vaccination. The fully scalable plant-based manufacturing process yields safe and immunogenic personalized FL vaccines that can be produced within weeks of obtaining patient biopsies.

Purification, identification and preliminary crystallographic studies of an allergenic protein from Solanum melongena

Solanum melongena (eggplant), a member of the Solanaceae family, is a widely cultivated vegetable crop and is commonly used as a food throughout the world. Allergic reactions caused by members of this family are well known. However, mechanistic analyses to understand their molecular basis have not been adequately explored. In order to address this issue, the 7S vicilin protein (SM80.1) of size 45 kDa was purified from seeds of S. melongena by ammonium sulfate fractionation and size-exclusion chromatography. Significant homology of SM80.1 to an allergy-related protein from S. lycopersicum was identified through a BLAST search. Crystallization attempts with purified protein using the hanging-drop vapour-diffusion method led to hexagonal-shaped crystals. The crystals diffracted to 2.21 Å resolution and belonged to space group P6322, with unit-cell parameters a = 117.9, c = 123.5 Å.

Evaluation of unintended effects in the composition of tomatoes expressing a human immunoglobulin A against rotavirus

The production of neutralizing immunoglobulin A (IgA) in edible fruits as a means of oral passive immunization is a promising strategy for the inexpensive treatment of mucosal diseases. This approach is based on the assumption that the edible status remains unaltered in the immunoglobulin-expressing fruit, and therefore extensive purification is not required for mucosal delivery. However, unintended effects associated with IgA expression such as toxic secondary metabolites and protein allergens cannot be dismissed a priori and need to be investigated. This paper describes a collection of independent transgenic tomato lines expressing a neutralizing human IgA against rotavirus, a mucosal pathogen producing severe diarrhea episodes. This collection was used to evaluate possible unintended effects associated with recombinant IgA expression. A comparative analysis of protein and secondary metabolite profiles using wild type lines and other commercial varieties failed to find unsafe features significantly associated with IgA expression. Preliminary, the data indicate that formulations derived from IgA tomatoes are as safe for consumption as equivalent formulations derived from wild type tomatoes.

Structural analysis of the endogenous glycoallergen Hev b 2 (endo-β-1,3-glucanase) from Hevea brasiliensis and its recognition by human basophils

Endogenous glycosylated Hev b 2 (endo-β-1,3-glucanase) from Hevea brasiliensis is an important latex allergen that is recognized by IgE antibodies from patients who suffer from latex allergy. The carbohydrate moieties of Hev b 2 constitute a potentially important IgE-binding epitope that could be responsible for its cross-reactivity. Here, the structure of the endogenous isoform II of Hev b 2 that exhibits three post-translational modifications, including an N-terminal pyroglutamate and two glycosylation sites at Asn27 and at Asn314, is reported from two crystal polymorphs. These modifications form a patch on the surface of the molecule that is proposed to be one of the binding sites for IgE. A structure is also proposed for the most important N-glycan present in this protein as determined by digestion with specific enzymes. To analyze the role of the carbohydrate moieties in IgE antibody binding and in human basophil activation, the glycoallergen was enzymatically deglycosylated and evaluated. Time-lapse automated video microscopy of basophils stimulated with glycosylated Hev b 2 revealed basophil activation and degranulation. Immunological studies suggested that carbohydrates on Hev b 2 represent an allergenic IgE epitope. In addition, a dimer was found in each asymmetric unit that may reflect a regulatory mechanism of this plant defence protein.

Molecular and cellular characterization of the tomato pollen profilin, LePro1

Profilin is an actin-binding protein involved in the dynamic turnover and restructuring of the actin cytoskeleton in all eukaryotic cells. We previously cloned a profilin gene, designated as LePro1 from tomato pollen. To understand its biological role, in the present study, we investigated the temporal and spatial expression of LePro1 during pollen development and found that the transcript was only detected at late stages during microsporogenesis and pollen maturation. Using antisense RNA, we successfully knocked down the expression of LePro1 in tomato plants using stable transformation, and obtained two antisense lines, A2 and A3 showing significant down-regulation of LePro1 in pollen resulting in poor pollen germination and abnormal pollen tube growth. A disorganized F-actin distribution was observed in the antisense pollen. Down-regulation of LePro1 also appeared to affect hydration of pollen deposited on the stigma and arrested pollen tube elongation in the style, thereby affecting fertilization. Our results suggest that LePro1 in conjunction with perhaps other cytoskeletal proteins, plays a regulatory role in the proper organization of F-actin in tomato pollen tubes through promoting actin assembly. Down-regulation of LePro1 leads to interruption of actin assembly and disorganization of the actin cytoskeleton thus arresting pollen tube growth. Based on the present and previous studies, it is likely that a single transcript of profilin gives rise to multiple forms displaying multifunctionality in tomato pollen.

Glyco-engineering for biopharmaceutical production in moss bioreactors

The production of recombinant biopharmaceuticals (pharmaceutical proteins) is a strongly growing area in the pharmaceutical industry. While most products to date are produced in mammalian cell cultures, namely Chinese hamster ovary cells, plant-based production systems gained increasing acceptance over the last years. Different plant systems have been established which are suitable for standardization and precise control of cultivation conditions, thus meeting the criteria for pharmaceutical production. The majority of biopharmaceuticals comprise glycoproteins. Therefore, differences in protein glycosylation between humans and plants have to be taken into account and plant-specific glycosylation has to be eliminated to avoid adverse effects on quality, safety, and efficacy of the products. The basal land plant Physcomitrella patens (moss) has been employed for the recombinant production of high-value therapeutic target proteins (e.g., Vascular Endothelial Growth Factor, Complement Factor H, monoclonal antibodies, Erythropoietin). Being genetically excellently characterized and exceptionally amenable for precise gene targeting via homologous recombination, essential steps for the optimization of moss as a bioreactor for the production of recombinant proteins have been undertaken. Here, we discuss the glyco-engineering approaches to avoid non-human N- and O-glycosylation on target proteins produced in moss bioreactors.

Functional characterization of a vacuolar invertase from Solanum lycopersicum: post-translational regulation by N-glycosylation and a proteinaceous inhibitor

Plant vacuolar invertases, which belong to family 32 of glycoside hydrolases (GH32), are key enzymes in sugar metabolism. They hydrolyse sucrose into glucose and fructose. The cDNA encoding a vacuolar invertase from Solanum lycopersicum (TIV-1) was cloned and heterologously expressed in Pichia pastoris. The functional role of four N-glycosylation sites in TIV-1 has been investigated by site-directed mutagenesis. Single mutations to Asp of residues Asn52, Asn119 and Asn184, as well as the triple mutant (Asn52, Asn119 and Asn184), lead to enzymes with reduced specific invertase activity and thermostability. Expression of the N516D mutant, as well as of the quadruple mutant (N52D, N119D, N184D and N516D) could not be detected, indicating that these mutations dramatically affected the folding of the protein. Our data indicate that N-glycosylation is important for TIV-1 activity and that glycosylation of N516 is crucial for recombinant enzyme stability. Using a functional genomics approach a new vacuolar invertase inhibitor of S. lycopersicum (SolyVIF) has been identified. SolyVIF cDNA was cloned and heterologously expressed in Escherichia coli. Specific interactions between SolyVIF and TIV-1 were investigated by an enzymatic approach and surface plasmon resonance (SPR). Finally, qRT-PCR analysis of TIV-1 and SolyVIF transcript levels showed a specific tissue and developmental expression. TIV-1 was mainly expressed in flowers and both genes were expressed in senescent leaves.

Inhibition of IgE binding to cross-reactive carbohydrate determinants enhances diagnostic selectivity

Background

Allergy diagnosis by determination of allergen-specific IgE is complicated by clinically irrelevant IgE, of which the most prominent example is IgE against cross-reactive carbohydrate determinants (CCDs) that occur on allergens from plants and insects. Therefore, CCDs cause numerous false-positive results. Inhibition of CCDs has been proposed as a remedy, but has not yet found its way into the routine diagnostic laboratory. We sought to provide a simple and affordable procedure to overcome the CCD problem.

Methods

Serum samples from allergic patients were analysed for allergen-specific IgEs by different commercial tests (from Mediwiss, Phadia and Siemens) with and without a semisynthetic CCD blocker with minimized potential for nonspecific interactions that was prepared from purified bromelain glycopeptides and human serum albumin.

Results

Twenty two per cent of about 6000 serum samples reacted with CCD reporter proteins. The incidence of anti-CCD IgE reached 35% in the teenage group. In patients with anti-CCD IgE, application of the CCD blocker led to a clear reduction in read-out values, often below the threshold level. A much better correlation between laboratory results and anamnesis and skin tests was achieved in many cases. The CCD blocker did not affect test results where CCDs were not involved.

Conclusion

Eliminating the effect of IgEs directed against CCDs by inhibition leads to a significant reduction in false-positive in vitro test results without lowering sensitivity towards relevant sensitizations. Application of the CCD blocker may be worthwhile wherever natural allergen extracts or components are used.

Matrix-assisted laser desorption/ionization imaging mass spectrometry of pollen grains and their mixtures

RATIONALE

The fast and univocal identification of different species in mixtures of pollen grains is still a challenge. Apart from microscopic evaluation and Raman spectroscopy, no other techniques are available.

METHODS

Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry was applied to the analysis of extracts of single pollen grains and pollen mixtures. Pollen grains were fixed, treated and covered with matrix directly on the MALDI target.

RESULTS

Clearly resolved MALDI ion intensity images could be obtained enabling the identification of single pollen grains in a mixture.

CONCLUSIONS

Our results demonstrate the potential and the suitability of MALDI imaging mass spectrometry as an additional method for the identification of pollen mixtures.

Clinico-Immunological Analysis of Eggplant (Solanum melongena) Allergy Indicates Preponderance of Allergens in the Peel

Background

Eggplant (Solanum melongena L.) is known to cause food allergy in some Asian countries but detailed studies on eggplant allergy are lacking.

Objective

The objective is to investigate sensitization to different parts of eggplant fruit, and detection of the allergens.

Methods

Six eggplant-allergic subjects were assessed for sensitization to eggplant (peel/pulp, and raw/cooked) by skin prick test, allergen-specific IgE, and immunoblots. Allergens were analyzed for glycoprotein nature by staining/lectinoblots, and in vitro stability in simulated gastric fluid.

Results

All the eggplant-sensitized subjects showed positive skin prick test with peel, pulp, raw, and cooked eggplant extracts; allergen-specific IgE to all these was positive. Raw eggplant contains 5 allergens in the range 36-71 kD. Most allergens are localized in the eggplant peel (9 allergens; 26-71 kD range) than the pulp (3 allergens; 52-71 kD); among these, the 26, 28, 36, and 71 kD allergens seem to be heat-stable. The 43, 45, 64, and 71 kD allergens are detected as glycoproteins; the 26, 64, and 71 kD allergens are stable displaying retention of IgE-binding ability in simulated gastric fluid digestion.

Conclusions

Eggplant is a multiallergenic vegetable in the context of presence of allergens in all edible parts of eggplant having preponderance in the peel.

Matrix-assisted laser desorption/ionization mass spectrometric investigation of pollen and their classification by multivariate statistics

RATIONALE

A fast and reliable online identification of pollen is not yet available. The identification of pollen is based mainly on the evaluation of morphological data obtained by microscopic methods.

METHODS

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) was applied to the analysis of extracts and milled pollen samples. The obtained MALDI data were explored for characteristic peak patterns which could be subjected to a multivariate statistical analysis.

RESULTS

Two sample preparation methods are presented, which require only minimal or no chemical extraction of the pollen. MALDI pollen spectra could be recorded showing various peak patterns. A multivariate statistics approach allowed the classification of pollen into clusters indicating similarities and differences between various species.

CONCLUSIONS

These results demonstrate the potential and the reliability of MALDI-TOF MS for the identification and, in combination with multivariate statistics, also for the classification of pollen.

Tomato allergy: impact of genotype and environmental factors on the biological response

BACKGROUND

Food allergies are increasing in the European population. At present the onset of symptoms can be avoided only by elimination of a particular fruit or vegetable from the diet. A new approach is to develop hypoallergenic food products. This study characterises the allergenic potential of tomatoes, considering cultivation conditions, developmental stages and genotypes, in order to identify hypoallergenic fruits.

RESULTS

Patients with a history of tomato allergy were recruited for skin allergy tests. Tomatoes carrying distinct genotypes were grown under various cultivation conditions and harvested at different maturation stages. Cultivation conditions (nitrogen fertilisation, light exposure and plant nutrition) did not affect the skin reactivity in tomato-allergic patients. However, skin reactivity was significantly lower when using green-unripe compared with red-ripe tomatoes and when using landrace cultivars compared with cultivars bred for use in organic horticulture.

CONCLUSION

Depending on their genetic background and maturity level, some tomato cultivars elicit positive reactions in tomato-allergic patients in the skin allergy test. This novel finding should pave the way for the development of tomatoes with reduced allergenicity to relieve sufferers of tomato allergy.

Silencing β1,2-xylosyltransferase in Transgenic Tomato Fruits Reveals xylose as Constitutive Component of Ige-Binding Epitopes

Complex plant N-glycans containing β1,2-xylose and core α1,3-fucose are regarded as the major class of the so-called "carbohydrate cross-reactive determinants" reactive with IgE antibodies in sera of many allergic patients, but their clinical relevance is still under debate. Plant glycosyltransferases, β1,2-xylosyltransferase (XylT), and core α1,3-fucosyltransferase (FucT) are responsible for the transfer of β1,2-linked xylose and core α1,3-linked fucose residues to N-glycans of glycoproteins, respectively. To test the clinical relevance of β1,2-xylose-containing epitopes, expression of the tomato β1,2-xylosyltransferase was down-regulated by RNA interference (RNAi) in transgenic plants. Fruits harvested from these transgenic plants were analyzed for accumulation of XylT mRNA, abundance of β1,2-xylose epitopes and their allergenic potential. Based on quantitative real-time PCR analysis XylT mRNA levels were reduced up to 10-fold in independent transgenic lines as compared to untransformed control, whereas no xylosylated N-glycans could be revealed by MS analysis. Immunoblotting using anti-xylose-specific IgG antibodies revealed a strong reduction of β1,2-xylose-containing epitopes. Incubating protein extracts from untransformed controls and XylT_RNAi plants with sera from tomato allergic patients showed a patient-specific reduction in IgE-binding, indicating a reduced allergenic potential of XylT_RNAi tomato fruits, in vitro. To elucidate the clinical relevance of β1,2-xylose-containing complex N-glycans skin prick tests were performed demonstrating a reduced responsiveness of tomato allergic patients, in vivo. This study provides strong evidence for the clinical relevance of β1,2-xylose-containing epitopes in vivo.

Impact of arbuscular mycorrhizal fungi on the allergenic potential of tomato

Arbuscular mycorrhizal (AM) fungi influence the expression of defence-related genes in roots and can cause systemic resistance in plants probably due to the induced expression of specific defence proteins. Among the different groups of defence proteins, plant food allergens were identified. We hypothesized that tomato-allergic patients differently react to tomatoes derived from plants inoculated or not by mycorrhizal fungi. To test this, two tomato genotypes, wild-type 76R and a nearly isogenic mycorrhizal mutant RMC, were inoculated with the AM fungus Glomus mosseae or not under conditions similar to horticultural practice. Under such conditions, the AM fungus showed only a very low colonisation rate, but still was able to increase shoot growth of the wild-type 76R. Nearly no colonisation was observed in the mutant RMC, and shoot development was also not affected. Root fresh weights were diminished in AM-inoculated plants of both genotypes compared to the corresponding controls. No mycorrhizal effects were observed on the biomass and the concentration of phosphate and nitrogen in fruits. Real-time quantitative polymerase chain reaction analysis revealed that six among eight genes encoding for putative allergens showed a significant induced RNA accumulation in fruits of AM-colonised plants. However, human skin reactivity tests using mixed samples of tomato fruits from the AM-inoculated and control plants showed no differences. Our data indicate that AM colonisation under conditions close to horticultural practice can induce the expression of allergen-encoding genes in fruits, but this does not lead necessarily to a higher allergenic potential.

Reduction of cross-reactive carbohydrate determinants in plant foodstuff: elucidation of clinical relevance and implications for allergy diagnosis

BACKGROUND

A longstanding debate in allergy is whether or not specific immunoglobulin-E antibodies (sIgE), recognizing cross-reactive carbohydrate determinants (CCD), are able to elicit clinical symptoms. In pollen and food allergy, ≥20% of patients display in-vitro CCD reactivity based on presence of α1,3-fucose and/or β1,2-xylose residues on N-glycans of plant (xylose/fucose) and insect (fucose) glycoproteins. Because the allergenicity of tomato glycoallergen Lyc e 2 was ascribed to N-glycan chains alone, this study aimed at evaluating clinical relevance of CCD-reduced foodstuff in patients with carbohydrate-specific IgE (CCD-sIgE).

METHODOLOGY/PRINCIPAL FINDINGS

Tomato and/or potato plants with stable reduction of Lyc e 2 (tomato) or CCD formation in general were obtained via RNA interference, and gene-silencing was confirmed by immunoblot analyses. Two different CCD-positive patient groups were compared: one with tomato and/or potato food allergy and another with hymenoptera-venom allergy (the latter to distinguish between CCD- and peptide-specific reactions in the food-allergic group). Non-allergic and CCD-negative food-allergic patients served as controls for immunoblot, basophil activation, and ImmunoCAP analyses. Basophil activation tests (BAT) revealed that Lyc e 2 is no key player among other tomato (glyco)allergens. CCD-positive patients showed decreased (re)activity with CCD-reduced foodstuff, most obvious in the hymenoptera venom-allergic but less in the food-allergic group, suggesting that in-vivo reactivity is primarily based on peptide- and not CCD-sIgE. Peptide epitopes remained unaffected in CCD-reduced plants, because CCD-negative patient sera showed reactivity similar to wild-type. In-house-made ImmunoCAPs, applied to investigate feasibility in routine diagnosis, confirmed BAT results at the sIgE level.

CONCLUSIONS/SIGNIFICANCE

CCD-positive hymenoptera venom-allergic patients (control group) showed basophil activation despite no allergic symptoms towards tomato and potato. Therefore, this proof-of-principle study demonstrates feasibility of CCD-reduced foodstuff to minimize 'false-positive results' in routine serum tests. Despite confirming low clinical relevance of CCD antibodies, we identified one patient with ambiguous in-vitro results, indicating need for further component-resolved diagnosis.

Identification and quantification of tomato allergens: in vitro characterization of six different varieties

BACKGROUND

The prevalence of sensitization to tomato has been estimated in 6.5% in a Mediterranean population.

OBJECTIVES

To characterize the allergenic profile of 6 commonly ingested varieties of tomato and to identify and quantify the most representative allergens.

METHODS

Rama, Rambo, Canario, Kumato, Pera and Raf tomato varieties were carefully peeled and extracts from peel and pulp prepared. The extracts were characterized by SDS-PAGE and immunoblot. Lyc e 3 and osmotin-like protein (OLP) were identified by LC MS/MS and PG2A by immunoblot with a specific polyclonal antibody. Protein content and allergen concentration (Lyc e 3 and PG2A) were measured by scanning densitometry after identification. One hundred and ninety-one patients were enrolled in the study. Specific IgE to all tomato extracts was evaluated by direct ELISA.

RESULTS

Eighty (41.7%) individuals reported symptoms after contact/ingestion with tomato, most of them oral symptoms. Protein profile and allergen quantification of the 6 varieties showed differences in the allergen composition. Lyc e 3 was visualized in all extracts, being the most abundant in all cases. PG2A and OLP were identified in all peel extracts and in some pulp extracts. Higher specific IgE values were obtained for the Kumato variety. Immunoblot showed the existence of several bands with IgE-binding capacity, especially at 12 and 45-50 kDa.

CONCLUSIONS

The study demonstrates differences in the antigenic and allergenic profiles of the analyzed varieties and variations in their allergenic composition, affecting the diagnostic capacity. LTP and PG2A are important tomato allergens in our population but other IgE-binding capacity proteins are also involved.

Novel IgE recognized components of Lolium perenne pollen extract: comparative proteomics evaluation of allergic patients sensitization profiles

In the last years, proteomic investigation provided a powerful tool in molecular characterization of complex allergen sources with relevant implications in both diagnosis and immunotherapic treatment of allergies. We followed a proteomic approach to characterize ryegrass (Lolium perenne) pollen, a common cause of seasonal allergic diseases affecting an increasing part of world population. Peptide shotgun experiments performed on nanoLiquid Ultra Pressure Chromatography coupled with fast Q-TOF MS-MS/MS acquisition protocols (MS(E)) and 2-DE immunoblot combined with MALDI-TOF-TOF analysis allowed the detection of all previously identified ryegrass allergens. Comparative analysis of immunoblot highlighted a class of patients characterized by a more complex 2-DE pattern associated with increased levels of IgE antibodies and by higher susceptibility to multiple sensitization toward different allergen sources. Cluster analysis revealed that all these patients recognized profilin, considered the main cross-reactive allergen in grass pollen. Furthermore, mass spectrometry analysis revealed the presence of other IgE reactive components in ryegrass pollen that might be involved in polysensitization, such as cyclophilin, fructosyltransferase and legumin-like protein.

In vitro cross-reactivity between tomato and other plant allergens

BACKGROUND

Cross-reactivity among fruits and different pollen and fruit species has been extensively reported.

OBJECTIVES

To investigate the in vitro cross-reactivity between tomato and pollen, fruit, and latex extracts and to identify the proteins involved.

METHODS

A serum pool was prepared from 18 individuals residing on the Spanish Mediterranean coast (9 men and 9 women; mean [SD] age, 27.4 [10.1] years) who had positive skin prick test reactions to tomato peel. Extracts from 10 pollens, 12 fruits, and latex were tested. Levels of specific IgE to each extract were measured. The allergenic profile was evaluated by means of immunoblot. The percentage of inhibition between extracts and tomato peel extract was analyzed by means of CAP inhibition, and the allergens implicated were elucidated by immunoblot inhibition.

RESULTS

For pollens, the highest specific IgE values were obtained for grasses. Most pollen extracts showed a capacity of inhibition similar to that of tomato peel extract; high percentages were obtained with Artemisia vulgaris and Poa pratensis. The most strongly inhibited allergens in tomato corresponded to bands of 32 and 45 kDa. For fruits, the highest value of specific IgE was detected for peach. High percentages of inhibition were obtained with peach and hazelnut. No inhibition was detected with latex. Peach, chestnut, and melon inhibited high molecular weight bands (32 and 45 kDa) and a band of approximately 10 kDa.

CONCLUSIONS

Cross-reactivity between tomato and pollen and fruit extracts has been demonstrated. Allergens with a high molecular weight range seem to be responsible in pollen extracts. A 10-kDa band seems to be responsible in Platanus acerifolia, Salsola kali, peach, chestnut, and melon.

Tomato allergy: detection of IgE-binding lipid transfer proteins in tomato derivatives and in fresh tomato peel, pulp, and seeds

There is an increasing consumption of tomatoes worldwide: fresh in salads, cooked in household sauces, or industrially processed. Although many tomato allergens have been identified, there is no information in the literature on the allergenic components found in commercial tomato products. The primary aim of the study was to evaluate the allergenic profile of commercial tomato products by skin prick tests (SPTs) and IgE/immunoblotting in tomato-allergic subjects. The secondary end point was the study of the IgE-binding profile of tomato peel, pulp, and seeds. Forty tomato-allergic patients, reporting oral allergy syndrome (OAS) at different grades of severity for fresh and, in some cases, also for cooked tomato, were selected on the basis of positive tomato allergy history or open food challenge (OFC). They were evaluated by SPTs with different experimental tomato extracts. SDS-PAGE/immunoblotting was performed to detect tomato allergens, which were then identified by Edman degradation. Twenty-three patients (57.5%) presented first-grade OAS at the OFC, whereas 17 (42.5%) reported severe symptoms. Ten of these 17 patients (25%) reported allergic reactions to cooked tomatoes; in immunoblotting tests, their sera reacted only to lipid transfer protein (LTP). In commercial products, LTP was the only detectable allergen. In contrast to other LTP-containing fruits, in tomato, an IgE-binding LTP was identified not only in the peel but also in the pulp and seeds. This study demonstrates that, in fresh tomato, different LTP isoforms are present and allergenic. Industrial tomato derivatives still contain LTP, thus presenting a problem for LTP-allergic patients.

Production of an egg yolk antibody against Parietaria judaica 2 allergen

Specific antibodies are essential tools for studying proteins as well as for diagnostic research in biomedicine. The egg yolk of immunized chicken is an inexpensive source of high-quality polyclonal antibodies. The 12-kDa Parietaria judaica 2 allergen was expressed as a fusion protein and was used to immunize Leghorn chickens. In this paper, we show, using 2-dimensional gel electrophoresis and immunoblotting, that chicken antibodies raised against a recombinant allergen can be used to recognize similar proteins from a pollen raw extract. Allergen identity was confirmed by nanoLC-nanospray-tandem mass spectrometry analysis. Our data demonstrate for the first time that a synergistic combination of molecular biology, 2-dimensional PAGE, and use of nonmammalian antibodies represents a powerful tool for reliable identification of allergens.