Identification of the allergenic components of kiwi fruit and evaluation of their cross-reactivity with timothy and birch pollens

Kiwifruit's Allergy in Children: What Do We Know?

Kiwifruit allergy is an emerging pathological condition in both general and pediatric populations with a wide range of symptoms linked to variable molecular patterns, justifying systemic and cross-reactions with other allergens (i.e., latex, pollen, and fruit). Skin prick test (SPT), specific serum IgE (Act d 1, Act d 2, Act d 5, Act d 8, and Act d 10) directed against five out of thirteen molecular allergens described in the literature, and oral test challenge with kiwifruit are available for defining diagnosis. The management is similar to that of other food allergies, mostly based on an elimination diet. Although kiwi allergy has been on the rise in recent years, few studies have evaluated the clinical characteristics and methods of investigating this form of allergy. Data collected so far show severe allergic reaction to be more frequent in children compared to adults. Therefore, the aim of this review is to collect the reported clinical features and the available association with specific molecular patterns of recognition to better understand how to manage these patients and improve daily clinical practice.

The Kiwifruit Allergen Act d 1 Activates NF-κB Signaling and Affects mRNA Expression of TJ Proteins and Innate Pro-Allergenic Cytokines

Impairment of the intestinal barrier is one of the key events in the initiation of the sensitization process in food allergy. The aim of this study was to explore the effects of kiwifruit allergen Act d 1 on intestinal permeability and tight junction protein (TJP) gene expression in vivo and to explore its potential to activate the NF-ĸB signaling pathway and to regulate expression of epithelial pro-allergenic cytokines. Influences of Act d 1 on TJP gene expression and pro-allergenic cytokines in the mouse intestine was analyzed by qPCR upon allergen administration by oral gavage. The effect on the in vivo intestinal permeability was assessed in ELISA by measuring the translocation of β-lactoglobulin (BLG) into circulation. The capacity of Act d 1 to activate the NF-ĸB pathway was tested in HEK293 cells by fluorescent microscopy and flow cytometry. Administration of Actinidin (Act d 1) increased intestinal permeability to the BLG. This was accompanied by changes in gene expression of TJP mRNA and pro-allergenic cytokines IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) compared to the control. Act d 1 reduced TEER of the HEK293 monolayer, was positive in an NF-ĸB-reporter HEK293 cell assay, and induced secretion of TSLP. These findings shed more light on the molecular events in the sensitization process of kiwifruit but possibly also of other protease food allergens.

Birch pollen allergy in Europe

Birch and other related trees of the families Betulaceae and Fagaceae (alder, hazel, oak, hornbeam, chestnut, and beech) constitute the birch homologous group. This grouping is primarily based on the extensive IgE cross-reactivity of allergen homologs to the major birch allergen Bet v 1. Birch pollen is the most dominant tree pollen in Northern and Central Europe and is a major cause of allergic rhinitis and, possibly, asthma symptoms. Over the last few decades, levels of birch pollen have risen and the period of exposure has increased due to climate changes. Subsequently, the prevalence of birch pollen sensitization has also increased. The cross-reactivity and sequential pollen seasons within the birch homologous group create a prolonged symptomatic allergy period beyond birch pollen alone. Furthermore, many plant food allergens contain homologs to Bet v 1, meaning that the majority of patients with birch pollen allergy suffer from secondary pollen food syndrome (PFS). As a result, the negative impact on health-related quality of life (HRQoL) in patients allergic to birch pollen is significant. The purpose of this manuscript was to narratively review topics of interest such as taxonomy, cross-reactivity, prevalence, clinical relevance, PFS, and HRQoL with regard to birch pollen allergy from a European perspective.

Proposed U.S. regulation of gene-edited food animals is not fit for purpose

Dietary DNA is generally regarded as safe to consume, and is a routine ingredient of food obtained from any living organism. Millions of naturally-occurring DNA variations are observed when comparing the genomic sequence of any two healthy individuals of a given species. Breeders routinely select desired traits resulting from this DNA variation to develop new cultivars and varieties of food plants and animals. Regulatory agencies do not evaluate these new varieties prior to commercial release. Gene editing tools now allow plant and animal breeders to precisely introduce useful genetic variation into agricultural breeding programs. The U.S. Department of Agriculture (USDA) announced that it has no plans to place additional regulations on gene-edited plants that could otherwise have been developed through traditional breeding prior to commercialization. However, the U.S. Food and Drug Administration (FDA) has proposed mandatory premarket new animal drug regulatory evaluation for all food animals whose genomes have been intentionally altered using modern molecular technologies including gene editing technologies. This runs counter to U.S. biotechnology policy that regulatory oversight should be triggered by unreasonable risk, and not by the fact that an organism has been modified by a particular process or technique. Breeder intention is not associated with product risk. Harmonizing the regulations associated with gene editing in food species is imperative to allow both plant and animal breeders access to gene editing tools to introduce useful sustainability traits like disease resistance, climate adaptability, and food quality attributes into U.S. agricultural breeding programs.

A Comprehensive Review on Kiwifruit Allergy: Pathogenesis, Diagnosis, Management, and Potential Modification of Allergens Through Processing

Kiwifruit is rich in bioactive components including dietary fibers, carbohydrates, natural sugars, vitamins, minerals, omega-3 fatty acids, and antioxidants. These components are beneficial to boost the human immune system and prevent cancer and heart diseases. However, kiwifruit is emerging as one of the most common elicitors of food allergies worldwide. Kiwifruit allergy results from an abnormal immune response to kiwifruit proteins and occur after consuming this fruit. Symptoms range from the oral allergy syndrome (OAS) to the life-threatening anaphylaxis. Thirteen different allergens have been identified in green kiwifruit and, among these allergens, Act d 1, Act d 2, Act d 8, Act d 11, and Act d 12 are defined as the "major allergens." Act d 1 and Act d 2 are ripening-related allergens and are found in abundance in fully ripe kiwifruit. Structures of several kiwifruit allergens may be altered under high temperatures or strong acidic conditions. This review discusses the pathogenesis, clinical features, and diagnosis of kiwifruit allergy and evaluates food processing methods including thermal, ultrasound, and chemical processing which may be used to reduce the allergenicity of kiwifruit. Management and medical treatments for kiwifruit allergy are also summarized.

Is kiwifruit allergy a matter in kiwifruit-cultivating regions? A population-based study

BACKGROUND

Although kiwifruit is known as a common cause of food allergy, population-based studies concerning the prevalence of kiwifruit allergy do not exist. We aimed to determine the prevalence and clinical characteristics of IgE-mediated kiwifruit allergy in 6-18-year-old urban schoolchildren in a region where kiwifruit is widely cultivated.

METHODS

This cross-sectional study recruited 20,800 of the randomly selected 6-18-year-old urban schoolchildren from the Rize city in the eastern Black Sea region of Turkey during 2013. Following a self-administered questionnaire completed by the parents and the child, consenting children were invited for skin prick tests (SPTs) and oral food challenges (OFCs). Children with suspected IgE-mediated kiwifruit were skin prick tested with kiwifruit (commercial allergen and prick-to-prick test with fresh kiwifruit) and a pre-defined panel of allergens (banana, avocado, latex, sesame seed, birch, timothy, hazel, cat, Dermatophagoides pteronyssinus, and Dermatophagoides farinae). All children with a positive SPT to kiwifruit were invited for an open OFC. The prevalence of IgE-mediated kiwifruit allergy was established using open OFCs.

RESULTS

The response rate to the questionnaire was 75.9% (15783/20800). The estimated prevalence of parental-perceived IgE-mediated kiwifruit allergy was 0.5% (72/15783) (95% CI, 0.39-0.61%). Of the 72 children, 52 (72.2%) were skin tested, and 17 (32.7%) were found to be positive to kiwifruit with both commercial extract and kiwifruit. The most frequently reported symptoms in kiwifruit SPT-positive children were cutaneous (n = 10, 58.8%) followed by gastrointestinal (n = 6, 35.3%) and bronchial (n = 4, 23.5%). Oral symptoms were reported in six (35.3%) children. All children who were kiwifruit positive by SPT were found positive during the oral challenge. The confirmed prevalence of IgE-mediated kiwifruit allergy by means of open OFC in 6-18-year-old urban schoolchildren living in Rize city was 0.10% (95% CI, 0.06-0.16).

CONCLUSION

Prevalence of parental-perceived and clinically confirmed kiwifruit allergy is not consistent. In contrast to expectations, kiwifruit allergy prevalence was low in a city where it is cultivated and highly consumed.

Kiwifruit Allergy in Children: Characterization of Main Allergens and Patterns of Recognition

Kiwifruit allergy has been described mostly in the adult population, but immunoglobulin (Ig)E-mediated allergic reactions to kiwifruit appear to be occurring more frequently in children. To date, 13 allergens from kiwifruit have been identified. Our aim was to identify kiwifruit allergens in a kiwifruit allergic-pediatric population, describing clinical manifestations and patterns of recognition. Twenty-four children were included. Diagnosis of kiwifruit allergy was based on compatible clinical manifestations and demonstration of specific IgE by skin prick test (SPT) and/or serum-specific IgE determination. SDS-PAGE and immunoblotting were performed with kiwifruit extract, and proteins of interest were further analyzed by mass spectrometry/mass spectrometry. For component-resolved in vitro diagnosis, sera of kiwifruit-allergic patients were analyzed by an allergen microarray assay. Act d 1 and Act d 2 were bound by IgE from 15 of 24 children. Two children with systemic manifestations recognized a protein of 15 kDa, homologous to Act d 5. Act d 1 was the allergen with the highest frequency of recognition on microarray chip, followed by Act d 2 and Act d 8. Kiwifruit allergic children develop systemic reactions most frequently following ingestion compared to adults. Act d 1 and Act d 2 are major allergens in the pediatric age group.

Molecular characterization of allergens in raw and processed kiwifruit

BACKGROUND

The prevalence of allergy to kiwifruit is increasing in Europe since the last two decades. Different proteins have been identified as kiwifruit allergens; even though with geographic differences, Act d 1, a cysteine protease protein of 30 kDa, and Act d 2, a thaumatin-like protein of 24 kDa, are normally considered the most important. The aim of this study was (i) to identify at molecular level the sensitization pattern in a group of well-characterized patients allergic to kiwifruit and (ii) to assess the role of technological treatments on kiwifruit allergenic potential.

METHODS

The differences in the pattern of antigenicity between fresh and processed kiwifruit were evaluated by both immunoelectrophoretic techniques and clinical tests.

RESULTS

In the group of patients included in this study, three proteins were identified as major allergens in fresh kiwifruit, as the specific sensitization was present in ≥50% of the subjects. These proteins corresponded to actinidin (Act d 1), pectin methyl aldolase (Act d 6), and thaumatin-like protein (Act d 2). Kiwellin (Act d 5) and proteins of Bet v 1 family (Act d 8/act d 11) were also recognized as minor allergens. Immunoreactivity was totally eliminated by industrial treatments used for the production of kiwifruit strained derivative.

CONCLUSIONS

In this group of allergic children, the technological treatments used in the production of kiwifruit strained product reduced drastically the allergenic potential of kiwifruit.

Detailed characterization of Act d 12 and Act d 13 from kiwi seeds: implication in IgE cross-reactivity with peanut and tree nuts

BACKGROUND

Act d 12 (11S globulin) and Act d 13 (2S albumin) are two novel relevant allergens from kiwi seeds that might be useful to improve the diagnostic sensitivity and the management of kiwifruit-allergic patients.

OBJECTIVE

To perform a comprehensive structural and immunological characterization of purified Act d 12 and Act d 13 from kiwi seeds.

METHODS

Sera from 55 well-defined kiwifruit-allergic patients were used. Act d 12 and Act d 13 were purified by chromatographic procedures. Circular dichroism, mass spectrometry, concanavalin A detection, immunoblotting, enzyme-linked immunosorbent assays, basophil activation tests, and IgE-inhibition experiments were used.

RESULTS

Act d 12 and Act d 13 were purified from kiwi seeds to homogeneity by combining size-exclusion, ion-exchange, and RP-HPLC chromatographies. Both purified allergens preserve the structural integrity and display typical features of their homologous counterparts from the 11S globulin and 2S albumin protein families, respectively. These allergens are released from kiwi seeds after oral and gastric digestion of whole kiwifruit, demonstrating their bioavailability after ingestion. The allergens retain the capacity to bind serum IgE from kiwifruit-allergic patients, induce IgE cross-linking in effector-circulating basophils, and display in vitro IgE cross-reactivity with homologous counterparts from peanut and tree nuts.

CONCLUSION

Purified Act d 12 and Act d 13 from kiwi seeds are well-defined molecules involved in in vitro IgE cross-reactivity with peanut and tree nuts. Their inclusion in component-resolved diagnosis of kiwifruit allergy might well contribute to improve the diagnostic sensitivity and the management of kiwifruit-allergic patients.

The effect of kiwifruit (Actinidia deliciosa) cysteine protease actinidin on the occludin tight junction network in T84 intestinal epithelial cells

Actinidin, a kiwifruit cysteine protease, is a marker allergen for genuine sensitization to this food allergen source. Inhalatory cysteine proteases have the capacity for disruption of tight junctions (TJs) enhancing the permeability of the bronchial epithelium. No such properties have been reported for allergenic food proteases so far. The aim was to determine the effect of actinidin on the integrity of T84 monolayers by evaluating its action on the TJ protein occludin. Immunoblot and immunofluorescence were employed for the detection of occludin protein alterations. Gene expression was evaluated by RT-PCR. Breach of occludin network was assessed by measuring transepithelial resistance, blue dextran leakage and passage of allergens from the apical to basolateral compartment. Actinidin exerted direct proteolytic cleavage of occludin; no alteration of occludin gene expression was detected. There was a reduction of occludin staining upon actinidin treatment as a consequence of its degradation and dispersion within the membrane. There was an increase in permeability of the T84 monolayer resulting in reduced transepithelial resistance, blue dextran leakage and passage of allergens actinidin and thaumatin-like protein from the apical to basolateral compartment. Opening of TJs by actinidin may increase intestinal permeability and contribute to the process of sensitization in kiwifruit allergy.

Diversity and relative levels of actinidin, kiwellin, and thaumatin-like allergens in 15 varieties of kiwifruit (Actinidia)

In the last 30 years the incidence of kiwifruit allergy has increased with the three major allergenic proteins being identified as actinidin, kiwellin, and thaumatin-like protein (TLP). We report wide variation in the levels of actinidin and TLP in 15 kiwifruit varieties from the four most widely cultivated Actinidia species. Acidic and basic isoforms of actinidin were identified in Actinidia deliciosa 'Hayward' and Actinidia arguta 'Hortgem Tahi', while only a basic isoform of actinidin was identified in Actinidia chinensis 'Hort16A'. One isoform each of kiwellin and TLP were identified in ripe fruit. The cysteine protease activity of actinidin correlated with protein levels in all species except A. arguta. Protein modeling suggested that modifications to the S2 binding pocket influenced substrate specificity of the A. arguta enzyme. Our results indicate that care is necessary when extrapolating allergenicity results from single varieties to others within the same and between different Actinidia species.

Kiwifruit allergies

While kiwifruit has a high nutritive and health value, a small proportion of the world's population appears to be allergic to the fruit. IgE-mediated kiwifruit allergy is often associated with birch and grass pollinosis as well as with latex allergy. Isolated allergy to kiwifruit is also relatively common and often severe. Eleven green kiwifruit (Actinidia deliciosa cv. Hayward) allergens recognized to date are termed as Act d 1 through Act d 11. Bet v 1 homologue (Act d 8) and profilin (Act d 9) are important allergens in polysensitized subjects, whereas actinidin (Act d 1) is important in kiwifruit monosensitized subjects. Differences in allergenicity have been found among kiwifruit cultivars. Allergy sufferers might benefit from the selection and breeding of low-allergenic kiwifruit cultivars.

Kiwifruit allergy across Europe: clinical manifestation and IgE recognition patterns to kiwifruit allergens

BACKGROUND

Kiwifruit is a common cause of food allergy. Symptoms range from mild to anaphylactic reactions.

OBJECTIVE

We sought to elucidate geographic differences across Europe regarding clinical patterns and sensitization to kiwifruit allergens. Factors associated with the severity of kiwifruit allergy were identified, and the diagnostic performance of specific kiwifruit allergens was investigated.

METHODS

This study was part of EuroPrevall, a multicenter European study investigating several aspects of food allergy. Three hundred eleven patients with kiwifruit allergy from 12 countries representing 4 climatic regions were included. Specific IgE to 6 allergens (Act d 1, Act d 2, Act d 5, Act d 8, Act d 9, and Act d 10) and kiwifruit extract were tested by using ImmunoCAP.

RESULTS

Patients from Iceland were mainly sensitized to Act d 1 (32%), those from western/central and eastern Europe were mainly sensitized to Act d 8 (pathogenesis-related class 10 protein, 58% and 44%, respectively), and those from southern Europe were mainly sensitized to Act d 9 (profilin, 31%) and Act d 10 (nonspecific lipid transfer protein, 22%). Sensitization to Act d 1 and living in Iceland were independently and significantly associated with severe kiwifruit allergy (odds ratio, 3.98 [P = .003] and 5.60 [P < .001], respectively). Using a panel of 6 kiwifruit allergens in ImmunoCAP increased the diagnostic sensitivity to 65% compared with 20% for skin prick tests and 46% ImmunoCAP using kiwi extract.

CONCLUSION

Kiwifruit allergen sensitization patterns differ across Europe. The use of specific kiwifruit allergens improved the diagnostic performance compared with kiwifruit extract. Sensitization to Act d 1 and living in Iceland are strong risk factors for severe kiwifruit allergy.

Component-resolved diagnosis of kiwifruit allergy with purified natural and recombinant kiwifruit allergens

BACKGROUND

Kiwifruit is one of the most common causes of food allergic reactions. Component-resolved diagnostics may enable significantly improved detection of sensitization to kiwifruit.

OBJECTIVE

To evaluate the use of individual allergens for component-resolved in vitro diagnosis of kiwifruit allergy.

METHODS

Thirty patients with a positive double-blind placebo-controlled food challenge to kiwifruit, 10 atopic subjects with negative open provocation to kiwifruit, and 5 nonatopic subjects were enrolled in the study. Specific IgE to 7 individual allergens (nAct d 1-5 and rAct d 8-9) and allergen extracts was measured by ImmunoCAP.

RESULTS

The diagnostic sensitivities of the commercial extract and of the sum of single allergens were 17% and 77%, respectively, whereas diagnostic specificities were 100% and 30%. A combination of the kiwi allergens Act d 1, Act d 2, Act d 4, and Act d 5 gave a diagnostic sensitivity of 40%, whereas diagnostic specificity remained high (90%). Exclusion of the Bet v 1 homolog recombinant (r) Act d 8 and profilin rAct d 9 from this allergen panel reduced sensitivity to 50% but increased specificity to 40%. Kiwifruit-monosensitized patients reacted more frequently (P < .001) with Act d 1 than polysensitized patients, whereas the latter group reacted more frequently with rAct d 8 (P = .004).

CONCLUSION

Use of single kiwifruit allergen ImmunoCAP increases the quantitative test performance and diagnostic sensitivity compared with the commercial extract. Bet v 1 homolog and profilin are important allergens in pollen-related kiwifruit allergy, whereas actinidin is important in monoallergy to kiwifruit, in which symptoms are often more severe.

Characterization of Bet v 1-related allergens from kiwifruit relevant for patients with combined kiwifruit and birch pollen allergy

Allergy to kiwifruit appears to have become more common in Europe and elsewhere during the past several years. Seven allergens have been identified from kiwifruit so far, with actinidin, kiwellin and the thaumatin-like protein as the most relevant ones. In contrast to other fruits, no Bet v 1 homologues were characterized from kiwifruit so far. We cloned, purified, and characterized recombinant Bet v 1-homologous allergens from green (Actinidia deliciosa, Act d 8) and gold (Actinidia chinensis, Act c 8) kiwifruit, and confirmed the presence of its natural counterpart by inhibition assays. Well-characterized recombinant Act d 8 and Act c 8 were recognized by birch pollen/kiwifruit (confirmed by double-blind placebo-controlled food challenge) allergic patients in IgE immunoblots and ELISA experiments. The present data point out that Bet v 1 homologues are allergens in kiwifruit and of relevance for patients sensitized to tree pollen and kiwifruit, and might have been neglected so far due to low abundance in the conventional extracts used for diagnosis.

Kiwellin, a modular protein from green and gold kiwi fruits: evidence of in vivo and in vitro processing and IgE binding

Kiwellin, an allergenic protein formerly isolated from green kiwi fruit, has been identified as the most abundant component of the gold kiwi species. A protein named KiTH, showing a 20 kDa band on reducing SDS-PAGE and 100% identity with the C-terminal region of kiwellin, has been identified in the extract of the ripe green species. In vitro treatment of purified kiwellin with the protease actinidin from green kiwi fruit originated KiTH and kissper, a recently described pore-forming peptide. Primary structure analysis and experimental evidence suggest that kiwellin is a modular protein with two domains. It may undergo in vivo proteolytic processing by actinidin, thus producing KiTH and kissper. When probed with sera recognizing kiwellin from green kiwi fruit, KiTH showed IgE binding, with reactivity levels sometimes different from those of kiwellin. The IgE-binding capacity of kiwellin from gold kiwi fruit appears to be similar to that of the green species.

Immunology

The concept of forbidden foods that should not be eaten goes back to the Garden of Eden and apart from its religious meanings it may also have foreshadowed the concept of foods that can provoke adverse reactions. Thus we could say that allergic diseases have plagued mankind since the beginning of life on earth. The prophet Job was affected by a condition that following the rare symptoms described by the Holy Bible might be identified as a severe form of atopic dermatitis (AD). The earliest record of an apparently allergic reaction is 2621 B.C., when death from stinging insects was first described by hieroglyphics carved into the walls of the tomb of Pharaoh Menes depicting his death following the sting of a wasp. In 79 A.D., the death of the Roman admiral Pliny the Elder was ascribed to the SO₂-rich gases emanating from the eruption of Mount Vesuvius. Hippocrates (460–377 B.C.) was probably the first to describe how cow’s milk (CM) could cause gastric upset and hives, proposing dietetic measures including both treatment and prevention for CM allergy.

Quantification of Art v 1 and Act c 1 being major allergens of mugwort pollen and kiwi fruit extracts in mass-units by ion-exchange HPLC-UV method

A simple ion-exchange HPLC-UV method was developed for determination of major allergens from mugwort pollen and kiwi fruit extracts in mass-units. The separation of Art v 1 and Act c 1 from other components in the extracts was achieved in one step. The extinction coefficients used in the study were theoretically determined and compared to the extinction coefficients determined by gravimetry. We also reported a close correlation of the major allergen contents with the overall allergenic potency of the extracts determined by inhibition ELISA. This method could be a useful tool for standardization of allergenic extracts for clinical use.

A matrix effect in pectin-rich fruits hampers digestion of allergen by pepsin in vivo and in vitro

BACKGROUND

It is a general belief that a food allergen should be stable to gastric digestion. Various acidic plant polysaccharides, including pectin, are ubiquitous in fruit matrixes and can form hydrogels under low-pH conditions.

OBJECTIVE

The purpose of this study was to investigate the effect of hydrogel forming polysaccharide-rich fruit matrixes on in vivo gastric and in vitro pepsic digestion of fruit allergens.

METHODS

Fruit extract proteins (kiwi, banana, apple and cherry) and a purified major kiwi allergen Act c 2 were digested with simulated gastric fluid in accordance with the US Pharmacopeia. In vivo experiments on kiwi fruit digestion were performed on four healthy non-atopic volunteers by examining the gastric content 1 h after ingestion of kiwi fruit. The Act c 2 and kiwi proteins were detected in immunoblots using monoclonal anti-Act c 2 antibodies and rabbit polyclonal antisera.

RESULTS

Crude fruit extracts were resistant to digestion by pepsin when compared with commonly prepared extracts. In the gastric content of all volunteers, following kiwi fruit ingestion and immunoblotting, intact Act c 2 was detected with anti-Act c 2 monoclonal antibodies, while kiwi proteins of higher molecular weights were detected using rabbit polyclonal antisera. Addition of apple fruit pectin (1.5% and 3%) to the purified kiwi allergen was able to protect it from pepsin digestion in vitro.

CONCLUSION

The matrix effect in pectin-rich fruits can influence the digestibility of food proteins and thereby the process of allergic sensitization in atopic individuals.

Kiwifruit allergy: actinidin is not a major allergen in the United Kingdom

BACKGROUND

Actinidin has previously been reported as the major allergen in kiwifruit. Objectives To investigate the relevance of actinidin in a well-characterized population of UK patients with kiwifruit allergy.

METHODS

To identify the allergens in kiwifruit, using Western blots, we examined the IgE-binding patterns of 76 patients with a history of kiwifruit allergy, 23 of who had had a positive double-blind, placebo-controlled food challenge. In addition, IgE binding to purified native actinidin was studied in 30 patients, and to acidic and basic isoforms of recombinant actinidin in five patients. Inhibition of IgE binding to kiwifruit protein extract by purified native actinidin was investigated by both inhibition immunoblots and inhibition ELISAs using pooled sera.

RESULTS

Twelve protein bands in kiwifruit protein extract were bound by IgE. A protein band with a molecular weight of 38 kDa was the major allergen recognized by 59% of the population. IgE did not bind to actinidin in the kiwifruit protein extract, or to purified native or recombinant forms of actinidin during Western blotting. Pooled sera bound to kiwifruit protein extract but not purified actinidin on ELISA, and pre-incubating sera with actinidin did not inhibit IgE binding to kiwifruit protein extract on immunoblot or ELISA.

CONCLUSION

A novel 38 kDa protein, not actinidin, is the major allergen in this large study population. Identification of major allergens in one patient group is therefore not necessarily reproducible in another; therefore, major allergens should not be defined until there is a sufficient body of data from diverse geographical and cultural populations.

Evaluation of IgE binding to proteins of hardy (Actinidia arguta), gold (Actinidia chinensis) and green (Actinidia deliciosa) kiwifruits and processed hardy kiwifruit concentrate, using sera of individuals with food allergies to green kiwifruit

BACKGROUND

Allergy to green kiwifruit has become common since the fruit was introduced in North America and Europe 30 years ago. Gold kiwifruit, more recently introduced commercially, has been shown to bind IgE from some individuals allergic to green kiwifruit. Hardy kiwifruit is a third species that is now cultivated in North America with potential application as a fresh fruit and in processed foods.

OBJECTIVE

To compare the IgE binding properties of proteins in hardy kiwifruit extract and processed hardy kiwifruit concentrate to each other and to extracts of green and gold kiwifruits to evaluate the potential for allergic cross-reactions.

METHODS

Sera from kiwifruit-allergic subjects and individuals without allergies to kiwifruit were assayed for IgE binding to soluble proteins in green, gold and hardy kiwifruits and heat-processed concentrate from hardy kiwifruit using immunoblots and direct enzyme-linked immunosorbent assay (ELISA).

RESULTS

Marked IgE binding to specific hardy kiwifruit proteins was identified. However, IgE binding to heat-processed hardy kiwifruit concentrate was remarkably lower than to the raw fruit extract.

CONCLUSIONS

These results suggest that some kiwifruit-allergic individuals may suffer allergic cross-reactions if they consume raw hardy kiwifruit. However, heat processing of the hardy kiwifruit alters allergenic protein structure, dramatically reducing in vitro IgE binding. Processing likely reduces the risk of eliciting an allergic response in those with allergies to raw kiwifruit.

Kiwellin, a novel protein from kiwi fruit. Purification, biochemical characterization and identification as an allergen*

Kiwellin is a novel protein of 28 kDa isolated from kiwi (Actinidia chinensis) fruit. It is one of the three most abundant proteins present in the edible part of this fruit. Kiwellin has been purified by ion exchange chromatography. Its N-terminal amino acid sequence revealed high identity with that previously reported for a 28 kDa protein described as one of the most important kiwi allergens. This observation prompted us to fully characterize this protein. The complete primary structure, elucidated by direct sequencing, indicated that kiwellin is a cysteine-rich protein. Serological tests and Western Blotting analysis showed that kiwellin is specifically recognized by IgE of patients allergic to kiwi fruit.

Comparison of the allergenicity of Actinidia deliciosa (kiwi fruit) and Actinidia chinensis (gold kiwi)

Actinidia chinensis (gold kiwi) is a newly available fruit which has been shown to have in vitro immunoglobulin E (IgE) cross-reactivity with green kiwi. This is the first study to investigate clinical reactivity of gold kiwi. Five patients clinically allergic to green kiwi were investigated by skin test and double-blind placebo controlled food challenge (DBPCFC) with gold kiwi fruit. IgE-binding patterns of individual sera from the five challenged patients and a pool of sera from a further nine patients with kiwi allergy were compared in the two fruits by Western blotting. Cross reactivity of proteins in the two fruits was assessed by inhibition of immunoblots and by IgE enzyme-linked immunosorbent assay (ELISA) inhibition. Four of the five patients had a positive DBPCFC to gold kiwi. Western blotting showed marked differences in the allergen patterns of green and gold kiwi. However, inhibition of the immunoblots and ELISA assay reveals extensive inhibition of IgE binding to proteins in each fruit by the alternative species. Gold kiwi fruit is allergenic and patients allergic to green kiwi are at risk of reacting to the gold kiwi fruit. Despite having different protein profiles and IgE-binding patterns, the two species have proteins that extensively cross-inhibit the binding to IgE.

Kiwellin, a Novel Protein from Kiwi Fruit. Purification, Biochemical Characterization and Identification as an Allergen*

Kiwellin is a novel protein of 28 kDa isolated from kiwi (Actinidia chinensis) fruit. It is one of the three most abundant proteins present in the edible part of this fruit. Kiwellin has been purified by ion exchange chromatography. Its N-terminal amino acid sequence revealed high identity with that previously reported for a 28 kDa protein described as one of the most important kiwi allergens. This observation prompted us to fully characterize this protein. The complete primary structure, elucidated by direct sequencing, indicated that kiwellin is a cysteine-rich protein. Serological tests and Western Blotting analysis showed that kiwellin is specifically recognized by IgE of patients allergic to kiwi fruit.

Food allergy to apple and specific immunotherapy with birch pollen

Conflicting results concerning the effect of specific pollen immunotherapy (SIT) on allergy to plant foods have been reported. The aim of this study was to investigate the effect of SIT using a birch pollen extract on food allergy with focus on allergy to apple. Seventy-four birch pollen-allergic patients were included in a double-blind, double-dummy, and placebo-controlled comparison of sublingual-swallow (SLIT) and subcutaneous (SCIT) administration of a birch pollen extract. Sixty-nine percent of these patients reported allergy to apple. The clinical reactivity to apple was evaluated by open oral challenges with fresh apple and a questionnaire. The immunoglobulin E (IgE)-reactivity was assessed by skin prick test (SPT), specific IgE, and leukocyte histamine release (HR). Forty patients were included in the final evaluation of the effect of SIT. The challenges were positive in 9 (SCIT), 6 (SLIT), and 8 (placebo) patients after treatment compared to 10, 4, and 10 patients, respectively, before SIT. The symptom scores to apple during challenges decreased in all groups, but only significantly in the placebo group (p = 0.03). As evaluated by the questionnaire, the severity of food allergy in general did not change and there were no differences between the groups. In spite of a significant effect on seasonal hay fever symptoms and use of medication and decrease in IgE-reactivity, SIT was not accompanied by a significant decrease in the severity of allergy to apple compared to placebo. Therefore, oral allergy syndrome (OAS) to apple should not be considered as a main criterion for selecting patients for birch pollen immunotherapy at present.

Structural, biological, and evolutionary relationships of plant food allergens sensitizing via the gastrointestinal tract

The recently completed genome sequence of the model plant species Arabidopsis has been estimated to encode over 25,000 proteins, which, on the basis of their function, can be classified into structural and metabolic (the vast majority of plant proteins), protective proteins, which defend a plant against invasion by pathogens or feeding by pests, and storage proteins, which proved a nutrient store to support germination in seeds. It is now clear that almost all plant food allergens are either protective or storage proteins. It is also becoming evident that those proteins that trigger the development of an allergic response through the gastrointestinal tract belong primarily to two large protein superfamilies: (1) The cereal prolamin superfamily, comprising three major groups of plant food allergens, the 2S albumins, lipid transfer proteins, and cereal alpha-amylase/trypsin inhibitors, which have related structures, and are stable to thermal processing and proteolysis. They include major allergens from Brazil nut, peanuts, fruits, such as peaches, and cereals, such as rice and wheat; (2) The cupin superfamily, comprising the major globulin storage proteins from a number of plant species. The globulins have been found to be allergens in plant foods, such as peanuts, soya bean, and walnut; (3) The cyteine protease C1 family, comprising the papain-like proteases from microbes, plants, and animals. This family contains two notable allergens that sensitize via the GI tract, namely actinidin from kiwi fruit and the soybean allergen, Gly m Bd 30k/P34. This study describes the properties, structures, and evolutionary relationships of these protein families, the allergens that belong to them, and discusses them in relation to the role protein structure may play in determining protein allergenicity.

The clinical relevance of sensitization to pollen-related fruits and vegetables in unselected pollen-sensitized adults

BACKGROUND

Previous studies have described cross-reactivity between fresh fruits, vegetables and pollen. However, no data demonstrates the clinical relevance of sensitization to pollen-related fruits and vegetables in unselected pollen-sensitized adults with and without symptoms in the pollen season.

OBJECTIVE

The aim of this study was to estimate the clinical relevance of sensitization to pollen-related fruits and vegetables in unselected pollen-sensitized adults and to examine the diagnostic value of skin-prick test (SPT), histamine release and specific IgE compared with the outcome of oral challenge.

METHODS

In total, 936 unselected adults (female : male 479 : 457, median age 33.7 years) were examined for pollen sensitization and clinical cross-reactivity with pollen-related fruits and vegetables by questionnaire, SPT, histamine release, specific IgE and oral challenge.

RESULTS

The prevalence of pollen sensitization was 23.8% (n = 223). The probability of a clinical reaction to pollen-related foods in the respective pollen-sensitized groups was: 24% (birch), 4% (grass), 10% (mugwort), 35% (birch + grass), 8% (grass + mugwort) and 52% (birch + grass + mugwort). The odds ratio of a clinical reaction to pollen-related fruits and vegetables in symptomatic pollen-sensitized adults was as high as four times (birch + grass) the odds ratio of a clinical reaction in asymptomatic pollen-sensitized adults.

CONCLUSION

This study not only demonstrates a high prevalence of clinical reactions to fruits and vegetables in pollen-sensitized adults, but also a discrepancy between the prevalence of sensitization to fruits and vegetables and the clinical relevance in different pollen-sensitized groups with symptoms in the pollen season as a significant factor.

Clinical tolerance of processed foods

OBJECTIVE

To review the effects of technological processing on selected foods of relevance to childhood allergy from the viewpoints of reduced allergenicity, contamination of processed foods by allergens introduced during processing, and ad hoc technologies to produce reduced hypoallergenic products.

DATA SOURCES

We searched the literature (PubMed/MEDLINE) for articles published between January 1994 and April 2004 using the following keywords: food allergy AND process* OR heat* OR cooking OR toleran*.

STUDY SELECTION

We drew on our collective clinical and biological experience to restrict retrieved studies to those of more frequent relevance to a hospital allergy practice.

RESULTS

Comparatively few clinical studies address the modification of allergenicity of food through cooking or processing. Dairy foods are largely unaffected by processing and may be contaminated by, or themselves become, hidden allergens. Hypoallergenic formulas based on milk, soy, or rice and homogenized beef are successful applications of allergenicity reduction via technological processing. Egg, fish, condiments, and vegetables all carry heat-resistant allergens and should also be considered contaminants. Cereals and bakery products are generally well tolerated, but their allergenicity may be enhanced by processing; the case of rice is still open. Peanut allergens are stable, and the evidence is scant that thermal processing affects the allergenicity of soybean and soy hydrolysates. The debate is ongoing about the tolerance of vegetable oils.

CONCLUSIONS

It is too early to systematize clinical studies based on single procedures. Processing affects antigenicity, but this does not always translate into safety recommendations. Industrial processing is liable to contamination, and monitoring and labeling are industry priorities. Clinicians should evaluate foods by as complete a workup as possible before recommending processed foods.

Tolerance of heat-treated kiwi by children with kiwifruit allergy

Kiwifruit allergy is increasing among children but whether heating affects clinical tolerance to kiwifruit is unknown. To assess tolerance to heated kiwifruit in children allergic to fresh kiwifruit. In this prospective trial, 20 children (median age 9.4 yr) with a history of immediate allergic reactions to fresh kiwifruit underwent double-blind placebo-controlled food challenges with steam-cooked (100 degrees C for 5') and industrially homogenised kiwifruit. Skin prick tests with a commercial kiwifruit allergen, raw kiwifruit and double-blind placebo-controlled food challenge with 25 g of fresh kiwifruit were used to confirm the history. Specific kiwifruit IgE to native and homogenized fruit were identified by immunoblotting. Fresh kiwifruit induced positive skin prick wheals in all children (confirmed during challenge in 19 patients). Commercial skin prick test elicited a positive response in five children, steam-cooked kiwifruit in five, and the homogenised kiwifruit preparation in none. UniCAP determinations were positive for kiwifruit in three patients. All children's sera showed specific IgE at immunoblotting with raw kiwifruit and one with the homogenised preparation (major allergens identified: Act c 1 and Act c 2). There was no clinical reactivity following challenge with homogenised kiwifruit but one child reacted to cooked kiwifruit challenge. Industrial heat treatment and homogenisation can make kiwifruit safe for children who are allergic to this increasingly popular fruit. This has dietary implications for children who are allergic to several fruit and vegetable proteins.

Kiwi fruit is a significant allergen and is associated with differing patterns of reactivity in children and adults

BACKGROUND

Allergy to kiwi fruit appears increasingly common, but few studies have evaluated its clinical characteristics, or evaluated methods of investigating the allergy.

OBJECTIVE

To characterize the clinical characteristics of kiwi fruit allergy and to study the role of double-blind placebo-controlled food challenge (DBPCFC), skin tests and specific IgE in the diagnosis of this food allergy.

METHODS

Two-hundred and seventy-three subjects with a history suggestive of allergy to kiwi completed a questionnaire. Forty-five were investigated by DBPCFC, prick-to-prick skin testing with fresh kiwi pulp, and specific IgE measurement. Nineteen subjects were also skin tested using a commercially available solution.

RESULTS

The most frequently reported symptoms were localized to the oral mucosa (65%), but severe symptoms (wheeze, cyanosis or collapse) were reported by 18% of subjects. Young children were significantly more likely than adults to react on their first known exposure (P<0.001), and to report severe symptoms (P=0.008). Twenty-four of 45 subjects (53%) had allergy confirmed by DBPCFC. Prick-to-prick skin test with fresh kiwi was positive in 93% of subjects who had allergy confirmed by DBPCFC, and also in 55% of subjects with a negative food challenge. The commercial extract was significantly less sensitive, but with fewer false-positive reactions. CAP sIgE was only positive in 54% of subjects who had a positive challenge.

CONCLUSIONS

Kiwi fruit should be considered a significant food allergen, capable of causing severe reactions, particularly in young children. DBPCFC confirmed allergy to kiwi fruit in 53% of the subjects tested, who had a previous history suggestive of kiwi allergy. Skin testing with fresh fruit has good sensitivity (93%), but poor specificity (45%) in this population. CAP sIgE and a commercially available skin test solution were both much less sensitive (54%; 75%) but had better specificity (90%; 67%).

Allergy to kiwi

BACKGROUND

Allergy to kiwi fruit is being increasingly reported, but it has never been evaluated by means of a double-blind, placebo-controlled food challenge (DBPCFC) study.

OBJECTIVE

We sought to assess kiwi allergy on the basis of a DBPCFC and identify the patterns of allergen recognition in sensitized patients from a birch-free area.

METHODS

Forty-three patients with allergy symptoms who were sensitized to kiwi were evaluated by means of clinical history, skin tests, IgE determinations, and DBPCFCs. The pattern of allergen recognition was assessed by means of IgE immunoblotting. Sequence analysis of IgE-binding bands was performed by using Edman degradation.

RESULTS

DBPCFCs were performed in 33 patients; 4 patients had experienced severe anaphylaxis, and 6 patients declined informed consent. DBPCFC results were positive in 23 patients and negative in 10 patients. The most frequent clinical manifestation was oral allergy syndrome. Twenty-one percent of the patients were not allergic to pollen. Forty-six percent of patients experienced systemic symptoms, and this happened with higher frequency in patients not allergic to pollen (100%). Twenty-eight percent of the patients were sensitized to latex. The IgE-binding bands in kiwi extract more frequently recognized by patient sera were those of 30, 24, 66, and 12 kd, and they could not be associated with any pattern of kiwi-induced allergic reactions.

CONCLUSION

The results provide evidence that kiwi allergy is not a homogeneous disorder because several clinical subgroups can be established. No definite allergen-recognition pattern was associated with the type of allergic reactions to kiwi. One of 5 patients with kiwi allergy was not allergic to pollen, and these patients had the highest risk of systemic reactions to kiwi.

Kiwi fruit allergy: a review

Allergy to kiwi fruit was first described in 1981, and there have since been reports of the allergy presenting with a wide range of symptoms from localized oral allergy syndrome (OAS) to life-threatening anaphylaxis. The article reviews the available information concerning the clinical features of kiwi fruit allergy and the role of clinical investigations for diagnosis. Work identifying the major allergens in kiwi fruit has resulted in conflicting results, the possible reasons for which are discussed. The clinical associations of kiwi fruit allergy with allergies to pollens or latex are reviewed.

Epicutaneous exposure to protein antigen and food allergy

BACKGROUND

The aetiology of food allergy remains unclear. Although failure to develop or breakdown in oral tolerance has been proposed, the existence of physiologic sensitization routes other than the gastrointestinal tract cannot be excluded.

OBJECTIVE

The purpose of this study is to clarify whether or not exposure to allergen through the skin can promote food allergy.

METHODS

BALB/c mice were shaved on the back, and a patch impregnated with 100 micro g of ovalbumin (OVA) was applied to the dorsal skin for a 1-week period and then removed. After three courses of sensitization, OVA-specific antibodies in sera were measured, and then mice were orally challenged with 50 mg of OVA. Anaphylactic symptoms, plasma histamine levels, and histology of intestines and lungs after oral challenge were examined.

RESULTS

Epicutaneous (EC) sensitization of mice to OVA induced a high level of OVA-specific IgE. Subsequent oral challenge with OVA resulted in symptoms of systemic anaphylaxis with elevated levels of plasma histamine as well as histological changes in both intestines and lungs. In the presence of anti-IL-4 antibodies, EC sensitization failed to provoke an IgE response, but still induced a Th2-predominant cellular immune response in lungs after oral challenge.

CONCLUSION

We demonstrated for the first time that food allergy can be induced by allergen exposure through the skin. Our results identify a novel role of EC sensitization in the pathogenesis of food allergy.

Identification of Cucumisin (Cuc m 1), a subtilisin-like endopeptidase, as the major allergen of melon fruit

BACKGROUND

Allergenic components in melon extracts have not been described in spite of the fact that melon (Cucumis melo) is a frequent allergy-eliciting fruit. The aim of this study was to evaluate allergenic components in melon extract and to report the identification of cucumisin as a major melon allergen.

MATERIALS AND METHODS

Sera from 35 patients allergic to melon were selected on the basis of clinical symptoms, skin prick tests and oral challenge test. Allergenic components were detected by sodium dodecyl sulphate polyacrylamide gel electrophoresis and immunoblotting. Molecular characterization of IgE-binding bands was performed by N-terminal amino acid sequencing.

RESULTS

More than 10 IgE-binding bands, between 10 and 80 kDa, were identified in melon extract. Out of them, four IgE-binding bands were major allergens: 14 kDa, 36 kDa, 54 kDa and 67 kDa. These major allergens, except 14 kDa band, showed the same N-terminal sequence: T-T-R-S-W-D-F-L. Research conducted with protein databases identified this N-terminal sequence as cucumisin, an alkaline serine protease, which shares structural homology with microbial subtilisin. The molecular mass of the identified bands corresponds with different molecular forms of cucumisin produced during the processing or degradation of the enzyme: 67 kDa native cucumisin, 54 kDa mature cucumisin and 36 kDa NH2-terminal cucumisin fragment.

CONCLUSION

Cucumisin (Cuc m 1) and several N-terminal cucumisin fragments are the major allergens of melon. The ubiquitous distribution of this protein family (cucumisin-like proteases) in many plant species and its high structural similarity suggest its potential role as a new panallergen in plant foods.

Detection of cross-reactivity for atopic immunoglobulin E against multiple allergens

The existence of specific immunoglobulin E (IgE) allows us to determine the allergens that cause the allergic disease. For the purposes of allergen avoidance and immunotherapy, the measurement of specific IgE is widely applied in clinical laboratories. However, if IgE from the serum of an allergic patient exhibits reactivity to multiple allergens, it would cause a problem. The present study analyzes whether the serum IgE with multiple reactivity is due to the presence of unique IgE against the common epitope shared by different allergens or the presence of multiple IgEs against different epitopes on different allergens. The quantitative-competitive inhibition tests and the immunoblotting were applied to analyze the immunosimilarity among examined allergens. The result shows that the competitive inhibition of IgE binding between shrimp and crab allergens is higher than those between either shrimp and cockroach or between crab and cockroach. Furthermore, the results of immunoblotting are consistent with those of quantitative-competitive inhibition tests. These results allow us to detect the cross-reactivity for atopic IgE against multiple allergens.

An allergen from Olea europaea pollen (Ole e 7) is associated with plant-derived food anaphylaxis

BACKGROUND

Several cross-reacting proteins have been identified as responsible of the co-occurrence of pollinosis and plant-derived food allergy. This association has been mainly described in the birch-apple syndrome but other pollens such as Olea europaea and other fruits may also contain homologous proteins.

OBJECTIVE

To evaluate the associations between sensitization to allergens of Olea europaea pollen and confirmed plant-derived food allergy, in addition to investigate if any pattern of clinical hypersensitivity of food allergy reaction (oral allergy syndrome (OAS) or anaphylaxis) and/or any fresh fruit or nut allergy, are associated to one or several Olea pollen allergen(s).

METHODS

One-hundred and thirty-four consecutive patients diagnosed with pollinosis by Olea were studied. Of these patients only 40, reported adverse reaction to plant-derived food. Twenty-one (group A) were classified as OAS and 19 (group B) as anaphylaxis. Skin-tests with six Olea pollen allergens and several groups of fruits, were performed. Double-blind placebo-controlled food challenge (DBPCFC), confirmed the diagnostics of food allergy with the exception of patients who suffered previous anaphylactic reaction.

RESULTS

All patients, showed a positive skin prick test (SPT), against one or more of Olea europaea allergens. Sensitization to Ole e 7, was more frequent (P = 0.02) in patients from group B. A total of 84 DBPCFC were performed with 44% positive results. Challenge confirmed at least the 50% of positive SPT in any case (peach: 68.42%; pear: 50%; melon: 71.42% and kiwi: 53.84%). In patients from group B, significant association with O. europaea pollen allergens were found between positive SPT to Rosaceae fruits and Ole e 3 (P = 0.045) and Ole e 7 (P = 0.03); Cucurbitaceae and Ole e 7 (P = 0.03) and Actinidiaceae with Ole e 3 (P = 0.04).

CONCLUSIONS

The results of this study, establish a new spectrum of associations between pollens and plant-derived foods: sensitization to olive profilin (Ole e 2) is not more frequent in OAS patients. Patients with anaphylactic reaction after eating fruit are also sensitized to Ole e 7, a LTP present in Olea pollen, and suffer pollinic symptoms. Finally a polcalcin (Ole e 3) could be also associated to Olea pollen respiratory and food allergy.