Molecular cloning and immunological characterisation of potential allergens from the mould Fusarium culmorum

Safety evaluation of Fy Protein™ (Nutritional Fungi Protein), a macroingredient for human consumption

Fy Protein™ (Nutritional Fungi Protein) is a macro-ingredient produced from the fermentation of the fungal microorganism Fusarium strain flavolapis, isolated from springs in Yellowstone National Park. Fy Protein contains all of the essential amino acids plus fiber, fat, carbohydrates, vitamins, and minerals and is developed as an alternative to animal-based protein foods such as meat and dairy. Fy Protein's nutritional, digestibility, genotoxicity, allergenicity, toxicity, secondary metabolites, and pathogenicity were evaluated. Fy Protein did not show mutagenic or genotoxic potential in in vitro tests. In an allergenicity review, Fy Protein was found to be of low allergenic potential. In a 90-day sub chronic dietary study in rats, administration of Fy Protein did not produce any significant toxicologic manifestations, and the no observed effect level (NOAEL) was the highest-level fed of 150,000 ppm (15% in the diet). Regulated secondary metabolites from fungi (termed mycotoxins) were non-detectable and below regulated levels using quantitative analytical techniques. A literature review was completed to identify the potential human pathogenicity of Fusarium sp., showing that Fusarium rarely infects humans, with infections seldom developing even in immunocompromised individuals. The results of these studies confirm that Fy Protein from fermented F. str. flavolapis has low toxicological, genotoxic, pathogenic, and allergenic potential under the conditions tested and anticipated use.

A new paradigm to search for allergenic proteins in novel foods by integrating proteomics analysis and in silico sequence homology prediction: Focus on spirulina and chlorella microalgae

Since novel nutrient sources with high protein content, such as yeast, fungi, bacteria, algae, and insects, are increasingly introduced in the consumer market, safety evaluation studies on their potentially allergenic proteins are required. A pipeline for in silico establishing the sequence-based homology between proteins of spirulina (Arthrospira platensis) and chlorella (Chlorella vulgaris) micro-algae and those included in the AllergenOnline (AO) database (AllergenOnline.org) is described. The extracted proteins were first identified through tryptic peptides analysis by reversed-phase liquid chromatography and high resolution/accuracy Fourier-transform tandem mass spectrometry (RPLC-ESI-FTMS/MS), followed by a quest on the UniProt database. The AO database was subsequently interrogated to assess sequence similarity between identified microalgal proteins and known allergens, based on criteria established by the World Health Organization (WHO) and Food and Agriculture Organization (FAO). A direct search for microalgal proteins already included in allergen databases was also performed using the Allergome database. Six proteins exhibiting a significant homology with food allergens were identified in spirulina extracts. Five of them, i.e., two thioredoxins (D4ZSU6, K1VP15), a superoxide dismutase (C3V3P3), a glyceraldehyde-3-phosphate dehydrogenase (K1W168), and a triosephosphate isomerase (D5A635), resulted from the search on AO. The sixth protein, C-phycocyanin beta subunit (P72508), was directly obtained after examining the Allergome database. Two proteins exhibiting significant sequence homology with food allergens were retrieved in chlorella extracts, viz. calmodulin (A0A2P6TFR8), which is related to troponin c (D7F1Q2), and fructose-bisphosphate aldolase (A0A2P6TDD0). Specific serum screenings based on immunochemical tests should be undertaken to confirm or rule out the allergenicity of the identified proteins.

Biochemical Characteristics and Allergenic Activity of Common Fungus Allergens

Fungi form a large kingdom with more than 1.5 million species. Fungal spores are universal atmospheric components and are generally recognized as important causes of allergic disorders, including allergic rhinitis, allergic rhinosinusitis, asthma, and allergic bronchopulmonary aspergillosis. The 4 genera which have the closest connection with allergic disorder are Cladosporium, Alternaria, Aspergillus and Penicillium. The cDNA sequences of many fungi allergens and the amino acids involved in their immunoglobulin E binding and T-cell activation have already been elucidated. Until now, 111 allergens from 29 fungal genera have been approved by the International Allergen Nomenclature Sub-committee. This review mainly focuses on the biochemical characteristics and allergenic activity of important allergens from common environmental fungi.

Evaluation of Unconventional Protein Secretion by Saccharomyces cerevisiae and other Fungi

Development of proteome analysis of extracellular proteins has revealed that a wide variety of proteins, including fungal allergens are present outside the cell. These secreted allergens often do not contain known secretion signal sequences. Recent research progress shows that some fungal allergens are secreted by unconventional secretion pathways, including autophagy- and extracellular-vesicle-dependent pathways. However, secretion pathways remain unknown for the majority of extracellular proteins. This review summarizes recent data on unconventional protein secretion in Saccharomyces cerevisiae and other fungi. Particularly, methods for evaluating unconventional protein secretion are proposed for fungal species, including S. cerevisiae, a popular model organism for investigating protein secretion pathways.

Fungal Contaminants in Drinking Water Regulation? A Tale of Ecology, Exposure, Purification and Clinical Relevance

Microbiological drinking water safety is traditionally monitored mainly by bacterial parameters that indicate faecal contamination. These parameters correlate with gastro-intestinal illness, despite the fact that viral agents, resulting from faecal contamination, are usually the cause. This leaves behind microbes that can cause illness other than gastro-intestinal and several emerging pathogens, disregarding non-endemic microbial contaminants and those with recent pathogenic activity reported. This white paper focuses on one group of contaminants known to cause allergies, opportunistic infections and intoxications: Fungi. It presents a review on their occurrence, ecology and physiology. Additionally, factors contributing to their presence in water distribution systems, as well as their effect on water quality are discussed. Presence of opportunistic and pathogenic fungi in drinking water can pose a health risk to consumers due to daily contact with water, via several exposure points, such as drinking and showering. The clinical relevance and influence on human health of the most common fungal contaminants in drinking water is discussed. Our goal with this paper is to place fungal contaminants on the roadmap of evidence based and emerging threats for drinking water quality safety regulations.

Isolation, expression and characterization of a minor allergen from Penicillium crustosum

A ribosomal P1 protein, Pen b 26 from Penicillium brevicompactum, was previously identified as a major allergen. A homolog protein was isolated and characterized from Penicillium crustosum which is not known to be allergenic mold. A cDNA library of P. crustosum was constructed and screened using a probe based on the DNA sequence of Pen b 26. A positive clone was isolated, expressed in Escherichia coli, purified and characterized by comparing its immunological and physical properties to Pen b 26. It was designated as Pen cr 26 and had a 321 nt ORF corresponding to 107 amino acids with a MW of 11 kDa. Pen cr 26 had strong sequence homology to Pen b 26 (92% for nucleotides and 86% for amino acids) and its physical and predicted structural properties were similar to the latter. The level of expression of Pen cr 26 was much lower than that of Pen b 26 in the same expression vector. Both proteins were recognized equally well by the IgG class specific antibodies, but Pen cr 26 was poorly recognized by Penicillium-sensitive atopic sera (IgE), suggesting striking antigenic difference in IgE epitopes, i.e., 87% were positive for Pen b 26 while only 23% were positive for Pen cr 26. The allergenicity of Pen cr 26 seems to be minor in nature and it could be a hypoallergenic variant of Pen b 26.

Structural aspects of fungal allergens

Despite the increasing number of solved crystal structures of allergens, the key question why some proteins are allergenic and the vast majority is not remains unanswered. The situation is not different for fungal allergens which cover a wide variety of proteins with different chemical properties and biological functions. They cover enzymes, cell wall, secreted, and intracellular proteins which, except cross-reactive allergens, does not show any evidence for structural similarities at least at the three-dimensional level. However, from a diagnostic point of view, pure allergens biotechnologically produced by recombinant technology can provide us, in contrast to fungal extracts which are hardly producible as standardized reagents, with highly pure perfectly standardized diagnostic reagents.

The transaldolase, a novel allergen of Fusarium proliferatum, demonstrates IgE cross-reactivity with its human analogue

Fusarium species are among airborne fungi and recognized as causative agents of human atopic disorders. However, Fusarium allergens have not been well characterized and the lack of information limits clinical diagnosis and treatment of fungal allergy. The purpose of this study is to identify and characterize important allergens of F. proliferatum. IgE-reacting F. proliferatum components were identified by immunoblot using serum samples from patients of respiratory atopic diseases. Characterization of allergens and determination of IgE cross-reactivity were performed by cDNA cloning, then homologous expression and immunoblot inhibition studies. We identified nine different F. proliferatum components that can be recognized by IgE antibodies in 17 (28%) of the 60 atopic sera tested. Components with molecular masses of about 43, 37.5 and 36.5 kDa with IgE-binding frequencies of about 88, 47 and 53%, respectively, were considered as important allergens of F. proliferatum. The 37.5 kDa IgE-binding component was putatively considered as a transaldolase protein of F. proliferatum. The full-length cDNA of F. proliferatum transaldolase was subsequently cloned. It encodes an open reading frame of 312 amino acids and has sequence identifies of 73 and 61%, respectively, with Cladosporium and human transaldolases. The purified recombinant F. proliferatum transaldolase can inhibit the IgE-binding against the 37.5 kDa component of F. proliferatum and the transaldolase allergen from Cladosporium cladosporioides. More importantly, the recombinant F. proliferatum transaldolase can inhibit IgE-binding against human transaldolase in a concentration-dependent manner. Thus, a novel and important F. proliferatum transaldolase allergen was identified. In addition to IgE cross-reactivity between the Fusarium and the Cladosporium transaldolase allergens, IgE cross-reactivity between the Fusarium and the human transaldolases also exists and might contribute to atopic manifestations in the absence of exogenous allergen exposure.

Fusarium culmorum: causal agent of foot and root rot and head blight on wheat

Fusarium culmorum is a ubiquitous soil-borne fungus able to cause foot and root rot and Fusarium head blight on different small-grain cereals, in particular wheat and barley. It causes significant yield and quality losses and results in contamination of the grain with mycotoxins. This review summarizes recent research activities related to F. culmorum, including studies into its population diversity, mycotoxin biosynthesis, mechanisms of pathogenesis and resistance, the development of diagnostic tools and preliminary genome sequence surveys. We also propose potential research areas that may expand our basic understanding of the wheat-F. culmorum interaction and assist in the management of the disease caused by this pathogen.

TAXONOMY

Fusarium culmorum (W.G. Smith) Sacc. Kingdom Fungi; Phylum Ascomycota; Subphylum Pezizomycotina; Class Sordariomycetes; Subclass Hypocreomycetidae; Order Hypocreales; Family Nectriaceae; Genus Fusarium.

DISEASE SYMPTOMS

Foot and root rot (also known as Fusarium crown rot): seedling blight with death of the plant before or after emergence; brown discoloration on roots and coleoptiles of the infected seedlings; brown discoloration on subcrown internodes and on the first two/three internodes of the main stem; tiller abortion; formation of whiteheads with shrivelled white grains; Fusarium head blight: prematurely bleached spikelets or blighting of the entire head, which remains empty or contains shrunken dark kernels. IDENTIFICATION AND DETECTION: Morphological identification is based on the shape of the macroconidia formed on sporodochia on carnation leaf agar. The conidiophores are branched monophialides, short and wide. The macroconidia are relatively short and stout with an apical cell blunt or slightly papillate; the basal cell is foot-shaped or just notched. Macroconidia are thick-walled and curved, usually 3-5 septate, and mostly measuring 30-50 × 5.0-7.5 μm. Microconidia are absent. Oval to globose chlamydospores are formed, intercalary in the hyphae, solitary, in chains or in clumps; they are also formed from macroconidia. The colony grows very rapidly (1.6-2.2 cm/day) on potato dextrose agar (PDA) at the optimum temperature of 25 °C. The mycelium on PDA is floccose, whitish, light yellow or red. The pigment on the reverse plate on PDA varies from greyish-rose, carmine red or burgundy. A wide array of polymerase chain reaction (PCR) and real-time PCR tools, as well as complementary methods, which are summarised in the first two tables, have been developed for the detection and/or quantification of F. culmorum in culture and in naturally infected plant tissue.

HOST RANGE

Fusarium culmorum has a wide range of host plants, mainly cereals, such as wheat, barley, oats, rye, corn, sorghum and various grasses. In addition, it has been isolated from sugar beet, flax, carnation, bean, pea, asparagus, red clover, hop, leeks, Norway spruce, strawberry and potato tuber. Fusarium culmorum has also been associated with dermatitis on marram grass planters in the Netherlands, although its role as a causal agent of skin lesions appears questionable. It is also isolated as a symbiont able to confer resistance to abiotic stress, and has been proposed as a potential biocontrol agent to control the aquatic weed Hydrilla spp.

USEFUL WEBSITES

http://isolate.fusariumdb.org/; http://sppadbase.ipp.cnr.it/; http://www.broad.mit.edu/annotation/genome/fusarium_group/MultiHome.html; http://www.fgsc.net/Fusarium/fushome.htm; http://plantpath.psu.edu/facilities/fusarium-research-center; http://www.phi-base.org/; http://www.uniprot.org/; http://www.cabi.org/; http://www.indexfungorum.org/

Allergens from Fusarium solani identified by immunoblotting in asthma patients In Iran

We extracted Fusarium solani antigens to evaluate specific anti-F. solani IgE in fifty-one patients with asthma (33 men and 18 women) and in 22 non-atopic healthy subjects (15 men and 7 women). F. solani strains were cultured in Sabouraud glucose agar and subjected to cell disruption using the freeze-and-thaw method. The obtained cytoplasmic extracts were analysed using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Sensitisation to F. solani antigens has been evaluated in asthmatic patients using the immunoblotting assay. The SDS-PAGE identified 29 protein bands in the cytoplasmic extracts of F. solani isolates, with molecular weights ranging from 24 kDa to 112 kDa. Immunoblotting detected specific anti-F. solani IgE antibody in all asthma patients, but not in the control group. The predominant reactive allergens in patients corresponded to the bands with molecular weights of 24 kDa, 58.5 kDa, 64.5 kDa, 69 kDa, 72 kDa, and 97 kDa. Our results suggest that various allergenic components of F. solani may produce symptoms of asthma in susceptible individuals and they call for further research.

Soybean (Glycine max) allergy in Europe: Gly m 5 (beta-conglycinin) and Gly m 6 (glycinin) are potential diagnostic markers for severe allergic reactions to soy

BACKGROUND

Soybean is considered an important allergenic food, but published data on soybean allergens are controversial.

OBJECTIVE

We sought to identify relevant soybean allergens and correlate the IgE-binding pattern to clinical characteristics in European patients with confirmed soy allergy.

METHODS

IgE-reactive proteins were identified from a soybean cDNA expression library, purified from natural soybean source, or expressed in Escherichia coli. The IgE reactivity in 30 sera from subjects with a positive double-blind, placebo-controlled soybean challenge (n = 25) or a convincing history of anaphylaxis to soy (n = 5) was analyzed by ELISA or CAP-FEIA.

RESULTS

All subunits of Gly m 5 (beta-conglycinin) and Gly m 6 (glycinin) were IgE-reactive: 53% (16/30) of the study subjects had specific IgE to at least 1 major storage protein, 43% (13/30) to Gly m 5 , and 36% (11/30) to Gly m 6. Gly m 5 was IgE-reactive in 5 of 5 and Gly m 6 in 3 of 5 children. IgE-binding to Gly m 5 or Gly m 6 was found in 86% (6/7) subjects with anaphylaxis to soy and in 55% (6/11) of subjects with moderate but only 33% (4/12) of subjects with mild soy-related symptoms. The odds ratio (P < .05) for severe versus mild allergic reactions in subjects with specific IgE to Gly m 5 or Gly m6 was 12/1.

CONCLUSION

Sensitization to the soybean allergens Gly m 5 or Gly m 6 is potentially indicative for severe allergic reactions to soy.

The spectrum of fungal allergy

Fungi can be found throughout the world. They may live as saprophytes, parasites or symbionts of animals and plants in indoor as well as outdoor environment. For decades, fungi belonging to the ascomycota as well as to the basidiomycota have been known to cause a broad panel of human disorders. In contrast to pollen, fungal spores and/or mycelial cells may not only cause type I allergy, the most prevalent disease caused by molds, but also a large number of other illnesses, including allergic bronchopulmonary mycoses, allergic sinusitis, hypersensitivity pneumonitis and atopic dermatitis; and, again in contrast to pollen-derived allergies, fungal allergies are frequently linked with allergic asthma. Sensitization to molds has been reported in up to 80% of asthmatic patients. Although research on fungal allergies dates back to the 19th century, major improvements in the diagnosis and therapy of mold allergy have been hampered by the fact that fungal extracts are highly variable in their protein composition due to strain variabilities, batch-to-batch variations, and by the fact that extracts may be prepared from spores and/or mycelial cells. Nonetheless, about 150 individual fungal allergens from approximately 80 mold genera have been identified in the last 20 years. First clinical studies with recombinant mold allergens have demonstrated their potency in clinical diagnosis. This review aims to give an overview of the biology of molds and diseases caused by molds in humans, as well as a detailed summary of the latest results on recombinant fungal allergens.

Translationally controlled tumor protein from Madurella mycetomatis, a marker for tumorous mycetoma progression

About 40 years ago Abs against the fungus Madurella mycetomatis were first demonstrated to be present in eumycetoma patients, a disease characterized by tumorous swellings. To date nothing is known about the individual immunoreactive Ags present in this fungus. In the present study, we identify its first immunogenic Ag, a protein homologous to the translationally controlled tumor protein (TCTP), a well-conserved histamine release factor in a range of eukaryotes. The gene for this Ag was demonstrated to be present in two variants in M. mycetomatis, with 13% aa difference between the two proteins encoded. In vitro, TCTP was secreted into the culture medium. In vivo, it was found to be expressed on hyphae present in developing stages of the eumycetoma-characteristic black grain. Significant IgG and IgM immune responses, against the whole protein and selected M. mycetomatis-specific peptides, were determined. The Ab levels correlated with lesion size and disease duration. Overall, the patients with the largest lesions had the highest Ab level, which lowered with decreasing size of the lesion. After 6-15 years of disease duration the Ab levels were the highest. TCTP is the first well-characterized immunogenic Ag, simultaneously the first monomolecular vaccine candidate, identified for the fungus M. mycetomatis.

Description of a novel panallergen of cross-reactivity between moulds and foods

The present investigation is undertaken to demonstrate a novel cross-reactivity between aeroallergens (moulds fungi imperfecti) and allergens from foods (spinach and mushroom Agaricus bisporus). We have performed a dual study in vivo and in vitro, in a population of atopic patients. Data from in vivo tests performed with spinach and mushroom have been statistically analysed. To the in vitro assays, mushroom and spinach extracts have been obtained, and sera from moulds allergic patients analysed by means of IgE-immunoblott assays. Inhibition experiments have been also performed to study a possible relation between proteins. Statistical analysis of data showed a relation between allergenicity to moulds (Alternaria alternata, Cladosporium herbarum and/or Aspergillus fumigatus), and positive skin prick tests with mushroom and/or spinach. The immunoblotts performed showed that seven moulds allergic patients had a strong recognition of a protein with a molecular weight of about 30 kD present both in spinach and mushroom extracts, and by means of inhibition assays we could determine that these two proteins were related. This study demonstrates the existence of a new allergen responsible for cross reactivity between moulds and two frequently consumed foods, mushroom and spinach. We conclude that a novel cross-reactive allergen between aeroallergens and foods has been identified.

Novel isoforms of Pru av 1 with diverging immunoglobulin E binding properties identified by a synergistic combination of molecular biology and proteomics

Birch pollen-related food allergies are mainly associated to Bet v 1. Little is known about isoforms of Bet v 1 homologous in fruit of the Rosaceae family. We attempted to identify novel isoforms of Pru av 1, the major cherry allergen, at the cDNA and the protein level by a combination of molecular biology and proteomic tools. A cDNA library was screened with patients immunoglobulin E (IgE) and a specific hybridization probe. Edman sequencing, mass spectrometry (MS), and MS/MS were performed after detecting Pru av 1 on 2-D maps by immunoblotting using patients IgE and a monoclonal antibody. Partial amino acid sequences were completed with a polymerase chain reaction (PCR) strategy. The IgE-binding properties of the Pru av 1 spots were analyzed by 2-D blot inhibition. cDNA library analysis revealed a novel Pru av 1 isoform. MS and N-terminal sequencing confirmed the cDNA sequences at the protein level. A series of spots were confirmed as the already known Pru av 1. One spot, exclusively detected with patients sera, was identified as the novel isoform. A partial amino acid sequence detected with MS/MS was completed by PCR-cloning. The 2-D blot inhibition revealed epitope differences between the novel isoform and the previously published Pru av 1. Our data demonstrate that a synergistic combination of molecular biology and proteomics represents a powerful tool for reliable and comprehensive identification of allergen isoforms and variants. The newly identified isoform showed diverging IgE-binding properties and may be relevant for the diagnosis or therapy of cherry allergy.

Immediate-type hypersensitivity reaction to ingestion of mycoprotein (Quorn) in a patient allergic to molds caused by acidic ribosomal protein P2

BACKGROUND

Quorn is the brand name for a line of foods made with so-called "mycoprotein," which springs from the mold Fusarium venenatum. Since the introduction on the food market, there have been complaints from consumers reporting adverse gastrointestinal reactions after ingestion of mycoprotein. To date, it is not clear whether the reported symptoms are IgE-mediated.

OBJECTIVE

The aim of the study was to describe for the first time a case history of an asthmatic patient with severe hypersensitivity reactions to ingested mycoprotein and to identify and characterize the potential allergen that might be responsible for this.

METHODS

The sensitization pattern of the asthmatic subject was characterized, and food allergy to mycoprotein was assessed by double-blinded placebo-controlled food challenge. Afterward, specific IgE antibodies of the serum of this patient were used to screen a Fusarium culmorum cDNA expression library. The coding sequence of one enriched cDNA-clone was expressed in Escherichia coli to produce a recombinant protein that was further purified and immunologically characterized.

RESULTS

The patient showed high sensitization to many known aeroallergens but apart from Quorn not to any other tested food samples. The deduced amino acid sequence of the enriched cDNA-clone (Fus c 1) showed large identity to the 60S acidic ribosomal protein P2 which is highly conserved among several species and also described as minor allergen in other mold species. The frequency of IgE reactivity of sera from F culmorum -sensitized subjects to rFus c 1 was approximately 35%. By enzyme allergosorbent test inhibition, we found 65% inhibition of mycoprotein IgE reactivity by rFus c 1. On the opposite we found reduced IgE reactivity of rFus c 1 of 68% by using mycoprotein as inhibitor.

CONCLUSIONS

Sensitization to mold allergens by the respiratory tract and subsequent oral ingestion of cross-reactive proteins may lead to severe food-allergic reactions. Thus, the 60S acidic ribosomal protein P2 of F venenatum probably is the reason for the described severe hypersensitivity reactions of the patient to Quorn-mycoprotein because of its potential cross-reactivity to the F culmorum allergen Fus c 1.