Food allergy

Molecular mechanisms of IgE mediated food allergy

The purpose of this review is to collate current knowledge and recent advances in molecular mechanism behind the immediate type hypersensitivity of foods. Food allergy is a growing concern of human health in developed as well as developing countries now days. Food allergic reactions are mostly IgE mediated and also known as immediate type hypersensitivity or type I reaction. This review encompasses a wide range of molecular events during IgE mediated reactions like primary exposure of allergens, processing of allergens by antigen presenting cells, role of transcription factors like GATA-3, STAT-6, NF-AT, c-maf, c-kit and NF-κB, Treg cells, toll like receptors, cytokines and chemokines, class switch to IgE, FcεR1 receptor, priming of IgE on mast cells or basophils, signaling events followed by secondary exposure of allergens, degranulation and release of mediators like leukotrienes, histamines, prostaglandins, β-hexosaminidase and ultimately anaphylaxis. This review may be helpful to beginners as well as experts working in the field of allergy and immunology because of the stepwise explanations of molecular mechanisms involved in IgE mediated reactions.

Allergen sanitation in the food industry: a systematic industrial scale approach to reduce hazelnut cross-contamination of cookies

Recently, we investigated the impact of shared equipment on cross-contamination of cookies at a pilot plant scale. Based on those findings, this study investigated the extent and subsequent sanitation of hazelnut cross-contamination (HNCC) of cookies at the industrial scale. Similarly, a product change from cookies with hazelnut ingredient to cookies without hazelnut was performed on standard equipment. HNCC in the hazelnut-free follow-up product was quantified by enzyme-linked immunosorbent assay for each production device and the applied cleaning procedure. All experiments were repeated in duplicate. The highest HNCC was found in concordance with previous studies after mere mechanical scraping: more than 1,000 mg of hazelnut protein per kg was quantified in the follow-up product after processing by a cookie machine. Additional cleaning with hot water decreased the HNCC irrespective of the processing device to levels at or below 1 mg of hazelnut protein per kg. Furthermore, raw materials for cookie production were monitored over a period of 24 months for unwanted preloads of hazelnut and peanut: hazelnut was quantified in 16% of the investigated raw materials as being between 0.26 and 90 mg/kg. Further critical control points at the industrial scale, where cross-contamination might occur, were identified but did not display noteworthy sources of cross-contamination. In conclusion, the quantitative monitoring of the cleaning efficiency at the industrial scale confirmed the procedure of manual scraping plus wet cleaning as a qualified sanitation procedure to effectively reduce the hazelnut protein cross-contamination down to a level at which severe hazelnut-related allergic reactions are unlikely to occur.

Pilot plant investigations on cleaning efficiencies to reduce hazelnut cross-contamination in industrial manufacture of cookies

Shared equipment in industrial food manufacture has repeatedly been described as a potential source of unlabeled food allergens, i.e., hidden allergens. However, the impact of shared equipment on allergen cross-contamination is basically unknown. Therefore, we sought to investigate systematically the extent of hazelnut cross-contamination in fine bakery wares as a model. A product change from cookies with 10% hazelnut to cookies without hazelnuts was simulated on pilot plant equipment. The extent of hazelnut cross-contamination (HNCC) was analyzed by enzyme-linked immunosorbent assay (ELISA) for each production device (kneaders, rotary molder, wire cutting machine, and steel band oven) and various cleaning procedures used between products. The experiments were performed repeatedly with finely ground hazelnuts and with roughly chopped hazelnut kernels. Cross-contamination from chopped kernels was distributed statistically but not homogeneously, and sampling and analysis with the ELISA was therefore not reproducible. Further analysis concentrated on homogenously distributed HNCC from ground hazelnut. Apart from product changes without intermediate cleaning, the highest HNCC was found after mechanical scraping: Up to 100 mg/kg hazelnut protein was found in the follow-up product after processing by one machine. After additional cleaning with hot water, the HNCC decreased regardless of the processing device to levels at or below 1 mg/kg hazelnut protein. In our pilot plant study, the application of an appropriate wet cleaning procedure in combination with quantitative monitoring of the cleaning efficiency reduced the hazelnut protein cross-contamination to a level at which severe hazelnut-related allergic reactions are unlikely to occur.

Molluscan shellfish allergy

Food allergies affect approximately 3.5-4.0% of the worldwide population. Immediate-type food allergies are mediated by the production of IgE antibodies to specific proteins that occur naturally in allergenic foods. Symptoms are individually variable ranging from mild rashes and hives to life-threatening anaphylactic shock. Seafood allergies are among the most common types of food allergies on a worldwide basis. Allergies to fish and crustacean shellfish are very common. Molluscan shellfish allergies are well known but do not appear to occur as frequently. Molluscan shellfish allergies have been documented to all classes of mollusks including gastropods (e.g., limpet, abalone), bivalves (e.g., clams, oysters, mussels), and cephalopods (e.g., squid, octopus). Tropomyosin, a major muscle protein, is the only well-recognized allergen in molluscan shellfish. The allergens in oyster (Cra g 1), abalone (Hal m 1), and squid (Tod p 1) have been identified as tropomyosin. Cross-reactivity to tropomyosin from other molluscan shellfish species has been observed with sera from patients allergic to oysters, suggesting that individuals with allergies to molluscan shellfish should avoid eating all species of molluscan shellfish. Cross-reactions with the related tropomyosin allergens in crustacean shellfish may also occur but this is less clearly defined. Occupational allergies have also been described in workers exposed to molluscan shellfish products by the respiratory and/or cutaneous routes. With food allergies, one man's food may truly be another man's poison. Individuals with food allergies react adversely to the ingestion of foods and food ingredients that most consumers can safely ingest (Taylor and Hefle, 2001). The allergens that provoke adverse reactions in susceptible individuals are naturally occurring proteins in the specific foods (Bush and Hefle, 1996). Molluscan shellfish, like virtually all foods that contain protein, can provoke allergic reactions in some individuals.

Review of the development of methodology for evaluating the human allergenic potential of novel proteins

Safety assessment of novel proteins in genetic-engineered foods is a key component of the overall safety evaluation for these products. Since allergens are typically proteins, assessment of the potential allergenicity of the novel proteins in genetically engineered foods is critical. This article reviews methods available to assess the potential allergenicity of novel proteins, as well as problems and deficiencies in the existing methods. The role of bioinformatics and knowledge of allergenic epitopes in developing new approaches to this problem is discussed.

Food allergen labeling in the USA and Europe

PURPOSE OF REVIEW

The ingredient statement on the label of packaged foods is an important source of information for food-allergic consumers. New legislation in the USA and European Union will increase the amount of information available to food-allergic consumers.

RECENT FINDINGS

The USA has implemented the Food Allergen Labeling & Consumer Protection Act, which mandates use of clear labeling and source labeling of ingredients derived from commonly allergenic sources. Similarly, the European Union is implementing new regulations that mandate the source labeling of ingredients derived from commonly allergenic foods and fuller disclosure of allergenic food components, even when present in small amounts. The food industry is providing consumers with information relating to the presence of allergenic residues by adding voluntary advisory statements, such as 'may contain peanuts'.

SUMMARY

Food-allergic consumers are advised to follow specific strict avoidance diets that exclude allergenic foods and ingredients derived from these foods. Thus individuals must avoid potentially hazardous residues of the allergenic food that might occur as the result of common practices in the food industry. The ingredient statement on packaged food labels now contains more information than ever before.

Sequence analysis and resistance to pepsin hydrolysis as part of an assessment of the potential allergenicity of ice structuring protein type III HPLC 12

The recently published WHO/FAO guidelines on the assessment of allergenicity of novel food proteins provide a strategy with which to approach the determination of the potential of novel proteins in foods to be allergens. Key to this strategy are the assessment of sequence similarity to known allergens and the assessment of the resistance to pepsin hydrolysis. Ice structuring proteins (also commonly referred to as anti-freeze or thermal hysteresis proteins) are a group of naturally occurring proteins that bind to ice and structure ice crystal formation. The amino acid sequence of the ice structuring protein (ISP) type III HPLC 12 (ISP type III) was compared in silico with the sequences of known allergens. Secondly, the resistance to pepsin hydrolysis of ISP type III and its glycoconjugates (produced in recombinant baker's yeast) was assessed. The results indicate that ISP type III has no sequence similarity with known allergenic proteins. Both ISP type III and ISP type III glycoconjugates contained within the fermentation product were hydrolysed readily by pepsin (50% loss in <10 min at pH 1.5) to give peptide fragments that were too small to be allergenic or to trigger cross-linking to IgE. In an accompanying study, we demonstrated that IgE from fish-allergic individuals did not bind ISP Type III. Therefore, in accordance with the WHO/FAO strategy, the assessment of ISP type III and ISP type III glycoconjugates by sequence analysis together with lack of resistance to pepsin hydrolysis and the absence of IgE binding supports the conclusion that both are unlikely to present a potential sensitisation hazard.

Peptides obtained by tryptic hydrolysis of bovine beta-lactoglobulin induce specific oral tolerance in mice

BACKGROUND

Oral tolerance against food proteins has been achieved in different animal models with use of native or moderately hydrolyzed proteins as inducers. However, native proteins remain highly allergenic, although it has been demonstrated that protein hydrolyzates and resulting peptides can lose their allergenicity.

OBJECTIVE

This study was designed to evaluate the ability of beta-lactoglobulin hydrolyzate and peptides to induce oral tolerance to native beta-lactoglobulin and to identify tolerogenic beta-lactoglobulin peptides with low allergenicity.

METHODS

beta-Lactoglobulin was hydrolyzed by trypsin and fractionated by ion exchange chromatography. Peptide enrichment of fractions was evaluated. Balb/c mice were fed beta-lactoglobulin hydrolyzate or fractions by single gavage at day 1. Five days later animals were challenged intraperitoneally with native beta-lactoglobulin. At day 27 delayed-type hypersensitivity was performed. Twenty-four hours later mice were bled, and intestinal contents and spleens were collected. Oral tolerance was measured by titrating specific IgE in sera and intestinal samples. Specific T-cell responses were analyzed by splenocyte proliferation. Antigenicity of hydrolyzate and fractions was evaluated by specific ELISA inhibition.

RESULTS

Mice fed either beta-lactoglobulin hydrolyzate or 2 fractions of the hydrolyzate were tolerized against beta-lactoglobulin. Specific serum and intestinal IgE were suppressed. Delayed-type hypersensitivity and proliferative responses were inhibited. One tolerogenic fraction was found to be 50 times less antigenic than the total beta-lactoglobulin hydrolyzate was.

CONCLUSION

These findings support the strategy of inducing oral tolerance in "at-risk" patients by means of tolerogenic cow's milk peptides or hydrolyzate.

Impact of processing on food allergens

In general, allergenic foods are resistant to processes commonly used in food manufacturing. Nearly all the causative proteins (allergens) retain their allergenicity after treatment by heat and/or proteolysis. Notable exceptions exist; for example, the allergenicity of many fresh fruits and vegetables is decreased or removed by relatively mild processes such as gentle heating or mashing. The use of proteolytic enzymes to remove allergenicity is successfully used in the production of hypoallergenic infant formulas, but this approach with other allergenic foods has resulted in only limited success. Processing effects can result in decreased or complete removal of allergenic qualities of a food, such as the removal of proteins in oilseed processing, which renders the oils hypoallergenic and safe for consumption by allergic individuals. This discussion will address the different allergenic foods and processes which can affect or decrease their allergenicity.

Immunoglobulin E suppression and cytokine modulation in mice orally tolerized to beta-lactoglobulin

This study was designed to confirm the tolerogenic properties of beta-lactoglobulin in a mouse model and to assess specific oral tolerance induction in humoral and cellular compartments. BALB/c mice were fed beta-lactoglobulin (BLG) or whey proteins at different ages and subsequently intraperitoneally challenged 5 days later with both BLG and a non-specific antigen, ovalbumin (OVA). Three weeks later, oral tolerance induction was analysed in CMP-fed, versus saline-fed mice, by measuring specific seric and intestinal antibody responses, delayed-type hypersensitivity (DTH), specific splenocyte proliferation, and cytokine secretion patterns. Three-week-old mice fed high doses of either whey proteins or BLG (respectively 3 mg/g or 5 mg/g of body weight) were found to achieve oral tolerization. At humoral and mucosal levels, anti-BLG immunoglobulin E (IgE) were suppressed in these groups when compared with saline fed mice. With respect to cellular responses, systemic DTH and lymphocyte proliferation to BLG were also inhibited in CMP-fed mice. Weaning time was determined to be the best period for oral tolerance induction. Kinetic analyses showed however, that a minimum of 2 weeks was required for oral tolerance detection. Finally, cytokine profiles indicated a reciprocal decrease of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) versus an increase of IL-10 and transforming growth factor-beta (TGF-beta) secretions in tolerized mice. Taken together, these results clearly showed that oral administration of high doses of cows' milk proteins can induce significant hyposensitization in mice, in a specific inhibition of T helper 1 (Th1) lymphocytes with the participation of suppressor cytokines.

Murine model of IgE production with a predominant Th2-response by feeding protein antigen without adjuvants

Stimulation of systemic antigen-specific IgE production plays an important role in the mediation of food allergy; however, the mechanism of IgE production against food antigens is not fully understood. The development of relevant animal models may help to elucidate the pathogenesis of food allergy. We here show that DBA/2 mice receiving a casein diet without any adjuvant produced high levels of IgE specific for casein, accompanied by predominant Th2-like responses in liver lymphocytes, mesenteric lymph node cells and spleen cells. This model of IgE production produced by feeding protein antigen as a constituent of the diet can be applied to investigate the mechanism of IgE production and to develop reagents for controlling food allergy.

Public perception of food allergy

Although studies that use the double-blind placebo-controled food challenge (DBPCFC) suggest that the prevalence of food allergy is about 2%, public belief in food allergy appears to be considerably higher. The study was undertaken to determine the magnitude and features of the American public's belief in food allergy by surveying a large, demographically balanced population. A simple question about food allergy was incorporated into a broad, self-reported, mailed consumer questionnaire. Demographically representative American households (5000) were surveyed by means of quota sample in 1989, 1992, and 1993. The response rate was 79, 75, and 74%, respectively. Of responding households, 16.2, 16.6, and 13.9%, respectively, of responding households reported an average of 1.17 household members with food allergy. Individuals reported to be allergic to foods were more likely to be female, particularly adult women. Male individuals with reported food allergy tended to be young, whereas no such skew was noted among female subjects. Geographic differences were observed in reported food allergy, with the highest rate in the Pacific region. Milk and chocolate were the individual foods most frequently implicated in food allergy. Trends were consistent over the time period studied. Perceived food allergy is widespread and persistent. The characteristics and demographic patterns of this belief are not reflective of known food allergy epidemiology derived from studies in which the DBPCFC is used.

Public perception of food allergy

BACKGROUND

Although studies that use the double-blind placebo-controlled food challenge suggest that the prevalence of food allergy is about 2%, public belief in food allergy appears to be considerably higher.

OBJECTIVE

The study was undertaken to determine the magnitude and features of the American public's belief in food allergy by surveying a large, demographically balanced population.

METHODS

A simple question about food allergy was incorporated into a broad, self-reported, mailed consumer questionnaire. Five thousand demographically representative American households were surveyed by means of quota sample in 1989, 1992, and 1993.

RESULTS

The response rates were 79%, 75%, and 74%, respectively. Of responding households, 16.2%, 16.6%, and 13.9%, respectively, reported an average of 1.17 household members with food allergy. Individuals reported to be allergic to foods were more likely to be female, particularly adult women. Male individuals with reported food allergy tended to be young, whereas no such skew was noted among female subjects. Geographic differences were observed in reported food allergy, with the highest rate in the Pacific region. Milk and chocolate were the individual foods most frequently implicated in food allergy. Trends were consistent over the period studied.

CONCLUSIONS

Perceived food allergy is widespread and persistent. The characteristics and demographic patterns of this belief are not reflective of known food allergy epidemiology derived from studies in which the double-blind placebo-controlled food challenge is used.

Psychiatry in the allergy clinic: the nature and management of patients with non-allergic symptoms

Patients with multiple unexplained somatic symptoms attributed to allergy frequently present to physicians and often the physician fails to find evidence for allergic or immunological mechanisms underlying the presenting symptoms. This article discusses the social and cultural background to this disorder. We then consider current explanatory models for symptoms and finally, we consider appropriate management, starting with the initial consultation, the identification of psychiatric disorders when present, and concluding with suggestions for subsequent treatment and guidance on appropriate referral.

Immunologic disturbances in cow's milk allergy, 2: Evidence for defective interferon-gamma generation

We have investigated the role of interferon-gamma (IFN-gamma) in the regulation of antigen-specific T-cell function in patients with cow's milk allergy. The study population consisted of 22 patients, aged from 7.6 to 56.9 months, who had challenge-proven cow's milk allergy (CMA) manifested with either skin (n = 9) or gastrointestinal (n = 13) symptoms. In addition, 11 age-matched children and 6 adults, mean (SD) age 31 (7) years, were studied as controls. Patients with challenge-proven CMA were rechallenged to establish whether they had acquired clinical tolerance to cow's milk. The spontaneous and mitogen-induced IFN-gamma and interleukin-4 (IL-4) generation of isolated lymphocytes was evaluated in vitro with commercial ELISA Kits at diagnosis and at reassessment. At diagnosis, the IFN-gamma production was not detectable in patients with CMA as compared with control children. IL-4 production was almost undetectable in all subjects in this study. However, at reassessment the CMA patients who had acquired clinical tolerance to cow's milk (n = 16) showed enhanced IFN-gamma production, when compared with that of control children, but still lower when compared with that of healthy adults. Our results indicate that the maturation of IFN-gamma producing T-cells is delayed in CMA, which could lead to a disturbance in the regulation of T-cell function. This defect might be an important etiologic factor for CMA.

Immune defense to dietary cow milk in healthy infants

The healthy young infant is immunologically adapted to receiving vast amounts of antigens in diet. At the age of 6 months, nine infants were put on a CM elimination diet for 3 weeks and then challenged with CM. Gut immune response was evaluated indirectly with ELISPOT assay at 6 months, after CM elimination (Day 1) and challenge (Day 8), and at 11 months. CM elimination decreased the numbers of immunoglobulin secreting cells (ISC): in the IgM class from mean [95% CI] 4969 [2555, 9653] at 6 months to 1716 [1024, 2873]/10(6) cells on Day 1 (t = 3.14, p = 0.01); and in the IgG class from 5547 [3562, 8630] to 2684 [1383, 5208]/10(6) cells (t = 3.29, p = 0.01). CM challenge further reduced inter-individual variation, and at 11 months the scatter of ISC was comparable to that at 6 months. Specific antibody-secreting cells of the IgA and IgG class were seen at 6 months and again at 11 months, while specific IgM-secreting cells persisted throughout the dietary manipulation. The results indicate that diet profoundly affects the immune defense system, and further suggest that a focused immune response is vital in acquisition of tolerance to dietary antigens.