[Allergy to cow's milk protein hydrolysates: apropos of 8 cases]

BACKGROUND

The use of extensively hydrolyzed protein formulas is the best alternative for children with cow's milk allergy, though cases of allergies to hydrolyzed proteins have been reported. The aim of this study was to clarify from our experience the diagnostic, evolutive and therapeutic aspects of allergies to extensively hydrolyzed protein formulas.

PATIENTS AND METHODS

We report eight cases of allergy to extensively hydrolyzed protein formulas seen between 1985 and 1998. The diagnostic criteria for allergy were either the appearance of immediate anaphylactic reactions after the ingestion of protein hydrolysate or a positive challenge test with the protein hydrolysate.

RESULTS

Four children developed immediate anaphylactic symptoms after ingesting protein hydrolysate, and four children demonstrated subacute or chronic gastrointestinal symptoms. All children who developed acute anaphylactic symptoms had positive skin tests and specific IgF, antibodies (RAST) to cow's milk and/or hydrolyzed proteins. Conversely, in the four children with chronic gastrointestinal symptoms, skin tests and specific IgE antibodies were negative in three cases, but intestinal histology was abnormal in all of them when they were fed with a protein hydrolysate; this became normal after excluding the hydrolysate (data available in only two cases). Three children tolerated another protein hydrolysate form (whey vs. casein), four children had a favourable outcome when fed with human milk, and an amino-acid-based formula was successfully used in the most recent case. Nonhydrolyzed cow's milk proteins were tolerated after the age of 18 months in six children. Other atopic symptoms were observed in six children.

CONCLUSION

Allergy to cow's milk protein hydrolysate is rare. The diagnosis is usually easy in children who develop acute anaphylactic symptoms, though intestinal histology is generally necessary for the diagnosis of allergy with chronic gastrointestinal symptoms. Treatment is based on the use of either another protein hydrolysate form (whey vs. casein) or an amino-acid-based formula.

Asthma induced by alcoholic drinks: a new food allergy questionnaire

OBJECTIVE

Asthmatic reactions to foods and drinks are a significant health problem in the community, however, the true extent of this problem is unclear. In this study, a new food allergy questionnaire (FAQ) was designed to specifically investigate the prevalence and characteristics of asthmatic reactions triggered by alcoholic drinks, as well as other foods and chemicals. The questionnaire's validity and reliability were assessed by comparing respondents' answers with data from clinical interview and repeat application.

METHODS

Twenty consecutive outpatients attending a Hospital Asthma Clinic completed the FAQ and subsequently were interviewed independently by their respiratory physician. The FAQ's ability to classify the asthma severity and atopic status of respondents, and to identify those asthmatics sensitive to alcoholic drinks, sulphite-containing foods and aspirin was assessed by comparison with clinical interview. The questionnaire's reliability was assessed in a separate and diverse community group of 20 asthmatic volunteers using the test-retest method.

RESULTS

Responses to the FAQ were found to correlate highly with assessment by clinical interview for all of the parameters assessed. Specifically, the FAQ identified reactions to alcoholic drinks with a coefficient of agreement of 88.9%, a sensitivity of 100%, and a specificity of 83.3%. Responses to the FAQ were also found to be reproducible for all of the parameters assessed.

CONCLUSION AND IMPLICATIONS

The FAQ is a useful and reliable tool for assessing the sensitivity of asthmatics to alcoholic drinks and various foods and chemicals, and provides a means to collect data relating to the prevalence and characteristics of these responses in community-based populations.

Allergenicity of Maillard reaction products from peanut proteins

It is known that peanut allergy is caused by peanut proteins. However, little is known about the impact of roasting on the allergenicity of peanuts. During roasting, proteins react with sugars to form Maillard reaction products, which could affect allergenicity. To determine if the Maillard reaction could convert a nonallergenic peanut protein into a potentially allergenic product, nonallergenic lectin was reacted with glucose or fructose at 50 degrees C for 28 days. Browning products from heat-treated peanuts were also examined. The products were analyzed in immunoblot and competitive assays, using a pooled serum (i.e., IgE antibodies) from patients with peanut anaphylaxis. Results showed that the products were recognized by IgE and had an inhibitory effect on IgE binding to a peanut allergen. Thus, the findings suggest that these Maillard reaction products are potentially allergenic and indicate the need to verify whether the Maillard reaction products formed in peanuts during roasting increase their allergenicity.

Characterization of a core alpha1-->3-fucosyltransferase from the snail Lymnaea stagnalis that is involved in the synthesis of complex-type N-glycans

We have identified a core alpha1-->3-fucosyltransferase activity in the albumin and prostate glands of the snail Lymnaea stagnalis. Incubation of albumin gland extracts with GDP-[(14)C]Fuc and asialo/agalacto-glycopeptides from human fibrinogen resulted in a labeled product in 50% yield. Analysis of the product by 400 MHz (1)H-NMR spectroscopy showed the presence of a Fuc residue alpha1-->3-linked to the Asn-linked GlcNAc. Therefore, the enzyme can be identified as a GDP-Fuc:GlcNAc (Asn-linked) alpha1-->3-fucosyltransferase. The enzyme acts efficiently on asialo/agalacto-glycopeptides from both human fibrinogen and core alpha1-->6-fucosylated human IgG, whereas bisected asialo/agalacto-glycopeptide could not serve as an acceptor. We propose that the enzyme functions in the synthesis of core alpha1-->3-fucosylated complex-type glycans in L. stagnalis. Core alpha1-->3-fucosylation of the asparagine-linked GlcNAc of plant- and insect-derived glycoproteins is often associated with the allergenicity of such glycoproteins. Since allergic reactions have been reported after consumption of snails, the demonstration of core alpha1-->3-fucosylation in L. stagnalis may be clinically relevant.

Detection and clinical characterization of patients with oral allergy syndrome caused by stable allergens in Rosaceae and nuts

BACKGROUND

A minority of patients with oral allergy syndrome (OAS) induced by Rosaceae or nuts are positive on skin prick tests with commercial food extracts. This suggests reactivity against distinct stable allergens.

OBJECTIVES

(1) To define the prevalence of subjects positive on skin prick tests with commercial extracts among patients with OAS caused by Rosaceae and/or nuts and (2) To investigate whether commercial extracts-positive subjects show some peculiar clinical feature and may represent a specific subset with food allergy.

METHODS

Skin prick tests were carried out with a large panel of commercial extracts of airborne allergens (Allergopharma) and of vegetable foods (Dome/Hollister-Stier) in 298 adults with OAS caused by Rosaceae (n = 237) and or nuts (n = 161), positive on skin prick tests with fresh offending foods.

RESULTS

25/237 (11%) patients were positive on prick tests with commercial plum extract. This subgroup showed a higher incidence of systemic symptoms (64% versus 6%; P < .001) and a lower incidence of birch pollen allergy (12% versus 99%; P < .001) than commercial extract-negative patients; moreover, 36% versus 0%, respectively, did not have respiratory allergy (P < .001). Apple and peach were the main offending foods among commercial extract-negative and commercial extract-positive patients, respectively (87% versus 44% for apple, P < .001; and 52% versus 88% for peach, P < .005). Eight of one hundred sixty-one (5%) nuts-sensitive patients were positive on prick test with commercial walnut extract. This subgroup showed a higher proportion of patients who experienced systemic symptoms (63% versus 6%, P < .001), a lower prevalence of birch pollen allergy (13% versus 97%, P < .001), and a higher prevalence of grass pollen allergy (88% versus 41%, P < .05) than commercial extract-negative subjects. Further, reactivity against commercial walnut extract was associated with skin reactivity against commercial extracts of peanut (88% versus 37%, P < .005), tomato (75% versus 5%, P < .001), and plum (63% versus 8%, P < .001), and inversely related with skin reactivity against fresh apple (P < .001). In most cases, high levels of IgE specific for peach, apple, and hazelnut were associated with peanut reactivity rather than with clinical sensitivity to specific foods. In a preliminary investigation, most commercial extract-positive patients reacted against a 10-kDa protein characterized as a lipid transfer protein (LTP).

CONCLUSIONS

Skin prick tests with commercial extracts of plum and walnut may be usefully employed to detect patients with OAS reacting against stable allergens. The high prevalence of systemic symptoms in these patients suggests that allergens' stability is associated with a higher resistance to the gastrointestinal environment and strongly influences the clinical expression of vegetable food allergy. At least some stable allergens, namely lipid transfer protein might be shared by botanically unrelated fruits such as nuts, peanuts, legumes, tomato, and Prunoideae.

Different serum interleukin-12 and sCD30 levels in food- and pollen-sensitized children

It has been proposed that a down-regulation of interleukin (IL)-12 and interferon (IFN)-gamma might be related to susceptibility to allergy in early life. The aim of this study was to assess serum IL-12 levels in food-sensitized and pollen-sensitized children and to compare these with another activation marker, sCD30. Twenty children with pollen allergy and 22 food-sensitized children were included. The diagnosis of immunoglobulin (Ig)-E-mediated allergy, suggested by clinical symptoms, was based on skin-prick tests, serum IgE antibodies and total IgE levels. Samples from 24 non-allergic children were used as controls. IL-12 and sCD30 levels were measured by ELISA. It was found that pollen-sensitized patients had normal IL-12 and higher sCD30 levels than controls (114 vs. 63 U/ml, p = 0.028), but, surprisingly, food-sensitized infants showed normal sCD30 and increased serum IL-12 levels (323 vs. 118 pg/ml, p = 0.0001). No differences were found in patients suffering from asthma or allergic dermatitis. Levels of sCD30 and IL-12 determined in May showed a strong correlation with those obtained in November. Interleukin-12 and IgE levels had an inverse correlation (r = -0.494, p = 0.0001) whereas no correlation was found between sCD30 and IgE. Age had a strong negative influence on IL-12 levels in allergic (Z = 4.834, p < 0.0005) and in normal children (Z = 3.00, p < 0.002); by contrast, sCD30 levels were not significantly age-dependent. When IL-12 levels from the food-allergy group were compared with those from normal controls younger than 4 years of age, the difference remained significant (p = 0.001), ruling out an age-bias. The conclusions made in this study were that serum IL-12 and sCD30 showed different behaviors in children with food or pollen allergy. We found IL-12 and sCD30 levels in pollen-allergic patients that agree with the classical T-helper (Th) 1/Th2 paradigm of allergy. In contrast, serum IL-12 levels were increased in food-sensitized children, suggesting a different immunologic pathogenesis.

Neonatal sensitisation to latex: a hypothesis

The exposure of babies to latex gloves at birth may be behind the dramatic increase in childhood allergies in the past 40 years. Jennifer Worth explores this theory and calls for a ban on the use of pre-powdered latex gloves in maternity units.

Lupine-induced anaphylaxis

BACKGROUND

Legumes are one of the most common foods causing allergic reactions in children and adults. Cross-reacting antibodies are frequently demonstrated in this family but the real clinical cross-reactivity is uncommon.

OBJECTIVE

To report a case of lupine-induced anaphylaxis and to elucidate in vivo and in vitro cross-reactivity with some legumes.

METHODS

Skin prick test (SPT) with some legumes were performed. Cap-IgE, ELISA-IgE, and immunoblotting were carried out. Open oral challenges with some legumes were performed. Cross-reactivity was studied by ELISA and immunoblotting inhibition.

RESULTS

The results demonstrated type-I hypersensitivity reactions with lupine and some other legumes. Cap-IgE with peanut was positive but the SPT and ELISA-IgE were negative and the patient tolerated a peanut challenge. ELISA inhibition revealed a partial inhibition (62%) using lupine as the solid phase. Partial inhibition was demonstrated by immunoblotting inhibition. Open oral challenge with peanut and green bean were negative but positive with pea.

CONCLUSION

We present a lupine sensitized patient with positive SPT and in vitro cross-reactivity with other legumes. Clinical cross-reactivity progressively developed over a 5-year period. Discrepancies were found between the clinical aspect and in vitro study of peanut allergy. Factors determining the wide variability in cross-reactivity among individuals are still obscure.

IgE antibody response to vertebrate meat proteins including tropomyosin

BACKGROUND

Although meat is a main source of proteins in western diets, little information is available regarding allergy to vertebrate meats or the allergens implicated in these reactions.

OBJECTIVE

To evaluate the in vitro IgE antibody response to different vertebrate meats in suspected meat-allergic subjects, as well as the possible role of tropomyosin in meat allergy and to analyze the cross-reactivity between vertebrate meats and the effect of heating on the IgE-binding to meat proteins.

METHODS

Fifty-seven sera from suspected meat-allergic subjects were tested by grid blot to extracts of beef, lamb, pork, venison, chicken, and turkey and to four mammalian tropomyosins of different origins.

RESULTS

Meat-allergic subjects have IgE antibodies to proteins in different mammalian meats (43/57 subjects); cross-reactivity with avian meat was limited: less than 50% (19/43) of meat positive sera reacted to chicken. In contrast, most of the poultry-positive sera also reacted to different mammalian meats. In general, there was stronger IgE reactivity to raw meats in comparison to cooked meats; an exception was six cases in which IgE reactivity to cooked poultry was stronger. Weak IgE reactivity to tropomyosin was detected in only 2/57 sera tested.

CONCLUSIONS

Suspected meat-allergic subjects have serum IgE directed to meat proteins. In vitro cross-reactivity among mammalian meats appears to be important, while cross-reactivity to poultry is limited indicating mammalian-specific proteins. Although cooking in general denatures meat proteins rendering them less allergenic, in some cases the process of cooking may result in the formation of new allergenic moieties. The muscle protein tropomyosin is not an important vertebrate meat allergen.

Comparison of different immunochemical methods for the detection and quantification of hazelnut proteins in food products

Hazelnuts are widely used in the food industry owing to their nutritive value and taste. The amount of hazelnut present in a recipe is usually considered as a mark of quality. On the other hand, contamination of foods that normally do not contain hazelnuts is a threat for patients with a hazelnut allergy. For this reason, the availability of a method for the detection and quantification of hazelnuts in foods would be desirable. The objective of this study was to develop a method for the detection and quantification of minor amounts of hazelnut protein in food products that is potentially applicable for the food industry. Several immunochemical methods, e.g., immunoblotting and enzyme-linked immunosorbent assay (ELISA), were developed with antibodies from both hazelnut-sensitized patient sera and the sera of rabbits hyperimmunized with hazelnut protein. Immunoblotting appeared to be non-specific when the sera of patients were used as a source of antibodies. Using immunopurified antibodies from rabbits immunized with hazelnuts, immunoblotting became specific, but the sensitivity of this method was limited. Inhibition of IgE binding is a generally used test in clinical laboratories to establish contamination with hazelnuts. This approach is sensitive and specific, but not readily accessible for the food industry since patient serum is needed. Similar results in terms of sensitivity and specificity were obtained with a sandwich ELISA constructed with an immunopurified antibody from rabbits sensitized to hazelnuts. No substantial cross-reactivity with other nuts, legumes or other food constituents was observed, and concentrations as low as 5 ng/ml, corresponding to 1 ppm in food products, were detected. In a field test, several consumer products regarded to be free of hazelnuts were shown to contain traces of hazelnut. This sandwich ELISA constructed with immunopurified antibodies from rabbits sensitized with hazelnut protein is a sensitive and specific method to detect and quantify hazelnut and is useful in detecting trace contamination with hazelnut in various consumer products. Since this test does not require serum from patients, it is appropriate for use in the food industry.

[Peanut anaphylaxis: the problem of hidden allergens]

HISTORY

Three patients developed recurrent anaphylactic reactions after ingestion of different kinds of food (Asian food, chocolate products, bakery products).

INVESTIGATIONS

In all three patients a severe peanut allergy was confirmed either by skin prick testing or serologically (specific IgE for peanut of CAP class 3,4 and 6 respectively). Peanut allergy in all patients explained the anaphylactic reactions due to ingestion of hidden peanut in the food.

TREATMENT

Patients were told to avoid the allergen. Because accidental ingestion is frequent in peanut allergy, they were equipped with a document stating the severity of the allergy and emergency medication (antihistamines, oral steroids, adrenaline injector).

CONCLUSIONS

Peanuts can be concealed in different kinds of food because they are cheap, rich in protein and are often used to change the viscosity of other foods. Especially the American and Asian cuisines use peanuts in a wide variety of recipes. Furthermore accidental ingestion can occur due to false or lacking declaration of peanuts in processed food. Patients with peanut allergy should be informed about these possibilities.

[Allergy to squid and acari in a child]

Anaphylactic reactions after consumption of squid by patients sensitized to house dust mites have been reported several times.

CASE REPORT

A child allergic to dust mites developed an angioneurotic edema after eating squid. An immunoallergological assessment, including the prick test, labial test and IgE RAST revealed an allergy associated to both dust mites and squid.

CONCLUSIONS

In light of the potential seriousness of anaphylactic reactions, parents of children allergic to dust mites and these children should be made aware of the increased risk of allergies to squid that they may face.

Production and characterization of rabbit polyclonal antibodies to almond (Prunus dulcis L.) major storage protein

Rabbits were immunized with purified almond major protein (AMP), the primary storage protein in almonds. Rabbit anti-AMP polyclonal antibodies (PA) could detect AMP when as little as 1-10 ng/mL were used to coat microtiter plates in a noncompetitive enzyme linked-immunosorbent assay (ELISA). Competitive inhibition ELISA assays detected the AMP down to 300 ng/mL. PA recognized the AMP in protein extracts from all U.S. major marketing cultivars of almonds (Mission, Neplus, Peerless, Carmel, and Nonpareil) with specific reactivity of 52.6-75% as compared to that of the AMP alone. Immunoreactivity of protein extracts prepared from commercial samples of blanched almonds, roasted almonds, and almond paste was respectively reduced by 50.0%, 56.6%, and 68.4% (noncompetitive ELISA) when compared to the immunoreactivity of the AMP. Moist heat (121 degrees C, 15 min) pretreatment of the AMP reduced the PA reactivity by 87% (noncompetitive ELISA). Exposing AMP to pH extremes (12.5 and 1.5-2.5) caused a 53% and 57% reduction in PA reactivity, respectively (noncompetitive ELISA). PA showed some cross-reactivity with the cashew major globulin, and to a lesser extent, the Tepary and Great Northern bean major storage protein (7S or phaseolin). The presence of almonds in a commercial food was detected using PA in a competitive ELISA.

Relationships between atopy and lung function: results from a sample of one hundred medical students in Japan

BACKGROUND

The prevalence of allergic diseases has been increasing dramatically and several studies have shown that atopy is related to asthmatic symptoms and bronchial hyperresponsiveness.

OBJECTIVE

To observe the relationships between atopic status and asthmatic predisposition (obstructive change in lung function) in apparently healthy young adults in Japan.

METHODS

A sample of 100 healthy Japanese medical students were subjected to a skin prick test for 11 common aeroallergens and food allergens, and their spirometric lung function was measured.

RESULTS

Surprisingly, 90% of them showed a positive prick test result for at least one of the 11 allergens tested, and 59% of them showed allergic responses to more than three allergens. The positive rate for Dermatophagoidesfarinae (Der) was the highest (71.0%), followed by house dust (57.0%), Dactylois gloinerata (42.0%), Cryptomeria gromerata (Cry) (40.0%), and cat fur (39.0%). Furthermore, there was no statistical difference in the positive rates for Der and Cry between groups with and without either the present illness or past history of any of the three major allergic diseases: bronchial asthma (BA), atopic dermatitis (AD), or allergic rhinitis (AR). Compared with the positive rates for these aeroallergens, those for food allergens were much lower (4% to 9%). Several lung function parameters, including the levels of FEV1% and %V50 which reflect obstructive pulmonary changes, showed significant negative correlation to the number of skin prick test-positive allergens. The same correlation was observed for groups without either the present illness or past history of BA.

CONCLUSION

These data suggest that those who are multi-allergic tend to feature subclinical asthma-like changes in their lung functions. Further studies are needed to determine whether this multi-allergic status can lead to future onset of asthma or other allergic diseases.

[New food allergies]

RISING INCIDENCE OF FOOD ALLERGIES: Food allergies are becoming more and more common, concerning 3 to 4% of the general population. One out of four persons allergic to nuts, the most frequent food allergen, have severe signs and symptoms. A CLASSICAL DIAGNOSIS: Certain diagnosis of food allergy is established on the basis of labial and oral tests. The dose required to induce a reaction is established by the oral test, giving information about the severity of the allergy and its progression. OTHER ALLERGENS: "Emerging" food allergens include spices and condiments, exotic fruits (kiwi, avocado, cashew and pecan nuts, Brazil nuts), sesame seeds, psyllium, sunflower seeds. Endurance exercise following ingestion of a food allergen can lead to severe anaphylactic reactions. Allergen associations "food-pollen", "latex-food", "mitessnails" have been described. INDISPENSABLE PREVENTION: Avoiding contact is essential. Many allergens are "masked" within prepared foods. Precise labeling, with particular attention to nut content, must be reinforced. Individualized counseling on food allergies should be available for school children. Persons with severe allergies should keep at hand an emergency kit with antihistamines, injectable rapid action corticoids and adrenalin (1 mg/ml).

Peels of Rosaceae fruits have a higher allergenicity than pulps

BACKGROUND

It is not uncommon that patients allergic to fruits such as apple, pear, and peach, refer adverse reactions after the ingestion of the whole fruit, but subsequently tolerate the pulp.

OBJECTIVE

This study aimed to compare the allergenicity of peels and pulps of apple, peach, and pear in 33 patients allergic to these fruits.

METHODS

Clinical reactivity to the ingestion of whole fruit (peel + pulp) and pulp was established by medical history. Peels and pulps were tested separately in skin prick tests (SPTs), histamine release tests (HRTs) and RASTs. Cross-allergenicity between peel and pulp of apple and peach was studied by RAST inhibition.

RESULTS

Adverse reactions appeared more frequently and were more severe when the whole fruit was eaten. More than 40% of patients allergic to apple and pear tolerated the ingestion of the pulp of these fruits, and reactions were only elicited by the intake of the whole fruit. Peels induced higher SPTs, HRTs and RASTs than pulps. An important cross-allergenicity was found between the peel and pulp of apple and peach, although the amount of the shared allergenic epitopes seemed to be higher in peels.

CONCLUSION

Our results suggest that peels of Rosaceae fruits such as apple, peach, and pear, have a higher allergenicity than pulps, which is clinically relevant. This aspect should be considered in the evaluation of patients allergic to Rosaceae fruits, and in the production of diagnostic materials.

Allergy to pizza: an uncommon and multifaceted allergy

The involvement of the Italian "pizza" in the wide and variegate field of food allergy is certainly uncommon. This simple Italian dish consists of a breadlike crust covered by a spiced preparation of cheese and tomatoes and baked. Italian pizza found its origin in Napoli and only in recent years has become a very popular food in the rest of Italy and elsewhere. In the beginning, it was the food of the poor, but was made with natural foods, but nowadays has been enriched by a number of ingredients and flavourings, thus multiplying the risk of allergic reactions.

Seafood allergy: tropomyosins and beyond

Hypersensitive reactions to seafood is one of the most common food allergies. Despite years of intensive studies, the reasons why some people are allergic to seafood is still unclear. The growing demand for seafood and the subsequent increasing risk of seafood allergy in the population at large make it important to elucidate the molecular basis of seafood allergy and identify the seafood allergens at the molecular level. Here, we discuss the clinical symptoms, physiological mechanisms, current findings of the immunological and molecular basis of shellfish allergy as well as future directions for the prevention of shellfish allergy. Interestingly, identified seafood allergens belong to a group of muscle proteins, namely the parvalbumins in codfish and tropomyosin in crustaceans. In addition, there is strong immunological evidence that tropomyosin is a cross-reactive allergen among crustaceans and mollusks. The molecular cloning, expression and biochemical characterization of seafood allergens will continue to provide valuable tools in the further understanding of the mechanisms of seafood allergy as well as the future development of immunomodulation regimen.

An oral sensitization model in Brown Norway rats to screen for potential allergenicity of food proteins

We developed an oral sensitization protocol for food proteins for the rat. Young Brown Norway (BN) rats were exposed to 1 mg ovalbumin (OVA) by daily gavage dosing for 42 days without the use of an adjuvant. OVA-specific IgE and IgG responses were determined by ELISA. On an oral challenge with OVA some clinical symptoms of food allergy-like effects on the respiratory system, blood pressure, and permeability of the gastrointestinal barrier were studied. In addition, BN rats were orally exposed to a total hen egg white protein (HEW) extract and cow's milk (CM) and the specificities of induced antibody responses were compared with the specificities of antibodies in sera from egg- and milk-allergic patients using immunoblotting. Animals orally exposed to the allergens developed specific IgE and IgG antibodies which recognized the same proteins compared with antibodies from egg- or CM-allergic patients. Among the various clinical symptoms of food allergy, gut permeability was increased after an oral challenge. In addition, some animals demonstrated a temporary decrease in breathing frequency or systolic blood pressure. The results obtained show that the Brown Norway rat is a suitable animal model for inducing specific IgG and IgE responses on daily intragastric dosing of OVA without the use of an adjuvant. Moreover, local immune-mediated effects on oral challenge are observed. The observation that enterally exposed BN rats and food-allergic patients demonstrate antibody responses to a comparable selection of proteins on exposure to different protein mixtures (HEW and CM) further supports the suitability of the BN rat as an animal model for food allergy research and for the study of the allergenicity of (novel) food proteins.

Food allergy in children-the Singapore story

The study of food allergy in Singaporean children is still in its infancy. Confusion and misunderstanding is common among the public. Even so, we have found certain unique features regarding food allergy among Singaporean children. "Bird's nest" has been shown to be the most common cause of anaphylaxis requiring medical attention. This allergen has not been described before. Peanuts and tree nuts are extremely uncommon causes of anaphylaxis, unlike the West. However, the pattern of sensitization to foods in children as shown by skin prick test is similar to other Western populations. The reasons for the difference between the profile foods responsible for anaphylactic reactions in our population and those of the western population, despite the similarity in sensitization profiles, are still unclear.

Pollen-related food allergy: cloning and immunological analysis of isoforms and mutants of Mal d 1, the major apple allergen, and Bet v 1, the major birch pollen allergen

BACKGROUND

Mal d 1, the major apple allergen, cross-reacts with IgE specific for the major birch pollen allergen, Bet v 1, and is responsible for birch pollen related food allergy to apple. Isoforms of Bet v 1 showing minor sequence variations display different binding capacity for specific IgE antibodies from allergic patients. Moreover, strain-dependent variation of allergenicity has been reported for apples.

OBJECTIVE

To investigate the occurrence of strain-dependent isoforms of Mal d 1 which may differ in their allergenic potential, to obtain data on structures essential for binding of Mal d 1 to the antibody, and to gain insights into the structures responsible for its IgE cross-reactivity to Bet v 1.

METHODS

The cDNA of Mal d 1 from various apple strains was amplified by a PCR strategy based on conserved regions of known Mal d 1-sequences, and sequenced. Two major isoforms of Mal d 1 were expressed as recombinant proteins and purified, as were different variants of the major birch pollen allergen, Bet v 1. Together with already existing recombinant birch pollen and apple allergens, these were subjected to allergenicity testing by IgE-immunoblotting, enzyme allergo sorbent test and dose related mediator release. "Hot-spots" for IgE-reactivity were identified by site-directed mutagenesis.

RESULTS

Twelve Mal d 1-clones were sequenced from 7 apple varieties and compared to 3 known Mal d 1 sequences. The clones were clustered into two groups, each showing a high degree of sequence identity to one of the known sequences and specific differences to the third sequence. No strain-specific sequences were identified. In contrast, apple strains with reported differences in allergenicity showed different expression levels of the major allergen. Immunologic testing of recombinant allergens revealed high IgE binding capacity of 2 major isoforms, named GD26 and GS29, with a slightly higher IgE binding capacity of GD26. Moreover, the allergenicity was similar to another r Mal d 1 reported in the literature, representing the isoform divergent from our clones. Mutational analysis of our Mal d 1 allergens identified serine in position 111 as essential for IgE binding. Allergenicity was almost depleted by changing this residue into a proline. Moreover, the corresponding serine residue, present in position 112 of Bet v 1, was in a similar manner crucial for the allergenicity of the birch pollen allergen.

CONCLUSION

We conclude that divergent allergenicity of apple strains mainly depends on different expression levels of the major allergen. Introduction of a proline residue in position 111 of Mal d 1 and in position 112 of Bet v 1 led to a drastic reduction of allergenicity of both the pollen and the food allergen, obviously also removing the cross-reactive epitope. Mutants with reduced IgE-reactivity but maintained T-cell reactivity may represent new candidates for a safer specific immunotherapy with reduced side-effects.