Cross-reactive epitopes and their role in food allergy.

Allergenic cross-reactivity among food allergens complicates the diagnosis and management of food allergy. This can result in many patients being sensitized (having allergen-specific IgE) to foods without exhibiting clinical reactivity. Some food groups such as shellfish, fish, tree nuts, and peanuts have very high rates of cross-reactivity. In contrast, relatively low rates are noted for grains and milk, whereas many other food families have variable rates of cross-reactivity or are not well studied. Although classical cross-reactive carbohydrate determinants are clinically not relevant, α-Gal in red meat through tick bites can lead to severe reactions. Multiple sensitizations to tree nuts complicate the diagnosis and management of patients allergic to peanut and tree nut. This review discusses cross-reactive allergens and cross-reactive carbohydrate determinants in the major food groups, and where available, describes their B-cell and T-cell epitopes. The clinical relevance of these cross-reactive B-cell and T-cell epitopes is highlighted and their possible impact on allergen-specific immunotherapy for food allergy is discussed.

[DEVELOPMENT AND VALIDATION OF QUALITY OF LIFE QUESTIONNAIRE FOR PARENT BURDEN OF CHILDREN WITH FOOD ALLERGY].

OBJECTIVE: Quality of life (QOL) questionnaires for parents of children with food allergies have been developed in the United States and Europe. However, no original Japanese QOL questionnaire has been developed till date. We aimed to develop an original questionnaire to evaluate the QOL in parents of children with food allergies in Japan. METHODS: We collected QOL-related questions from parents of children with food allergies aged 0-15 years, and created a primary questionnaire. Responses to the primary questionnaire were obtained from the parents again, and question items were reduced using factor analysis to create a secondary questionnaire comprising eight items. In addition to the secondary questionnaire, responses to the Food Allergy QOL Questionnaire-Parent Form (FAQLQ-PF) Japanese version, Parent reported Health-Related QOL in children and adolescents (KINDL) and Health-related QOL (SF-8) were obtained from parents to assess the validity of the secondary questionnaire. RESULTS: A total of 407 parents completed all questionnaires. The secondary questionnaire scores were positively correlated with those of FAQLQ-PF and weakly negatively correlated with the KINDL and SF-8 mental component summary scores. Parents of children with food allergies with ≥3 culprit foods or severe reactions to daily foods, a history of anaphylaxis, and those carrying adrenaline autoinjectors scored higher and had lower QOL. CONCLUSION: The developed original questionnaire is a valid QOL questionnaire for Parents of children with food allergies.

[ANTIGENICITY OF SOY PROTEIN IN SOY-BASED INFANT FORMULA BONLACT® i].

BACKGROUND: The purpose of this study was to compare the antigenicity of Bonlact® i (BL) with that of defatted soy protein (SP) and soy protein isolate (SPI), which is the original source of BL, using sera from patients with soybean allergy. METHODS: Proteins were extracted from SP, SPI, and BL using PBS. Proteins in each sample were analyzed for antigenicity using inhibition ELISA with SP-specific IgE (sIgE), SDS-PAGE, and immunoblotting. Sere from patients with soybean allergy confirmed by an oral food challenge (OFC) (n=6, OFC+ Pt), and from patients who were positive for soy-sIgE without symptoms ( n = 7, sIgE+ Pt) were used for these assays. The cross-antigenicity of SP and BL with cow's milk (CM) proteins was also analyzed in the sera from patients with CM allergy using inhibition ELISA. RESULTS: SDS-PAGE showed that the proteins in BL produced a smear-like band in the low-molecular-weight region compared with that in SP and SPI. Inhibition ELISA against SP-sIgE showed that BL had a significantly lower inhibition rate than that of SP in both OFC+ Pt and sIgE+ Pt. Immunoblotting analysis showed that the bands of BL were thinner than those of SP and SPI. Additionally, SP and BL showed no cross-antigenicity with CM proteins. CONCLUSION: The proteins in BL was partially digested, and its antigenicity was lower than that of SP and SPI.

Effects of regular soy formula intake between 1 and 2 months of age on food sensitization in infancy.

BACKGROUND: The effects of regular soy formula (SF) intake on the development of food sensitization in infancy remain unclear. This study aimed to assess the effects of regular SF intake between 1 and 2 months of age on food sensitization development by 6 months of age. METHODS: Using data from a randomized controlled trial of a birth cohort from four Japanese hospitals that assessed cow's milk allergy development, we performed a retrospective cohort study of 235 infants who avoided cow's milk formula and supplemented breastfeeding with SF as required between 1 and 2 months of age. Regular SF intake was defined as SF consumption of ≥14 days per month and ≥1350 ml per month. Food sensitization was defined as positive skin prick test reactions to hen's egg, cow's milk, wheat, and/or soy. Using multivariable logistic regression models that adjusted for parental, perinatal, and environmental factors, we calculated the adjusted odds ratios of regular SF intake for food, hen's egg, and cow's milk sensitization by 6 months of age. RESULTS: From the 235 participants, 114 (48.5%) had regular SF intake. The adjusted odds ratios of regular SF intake for food, hen's egg, and cow's milk sensitization were 0.32 (95% confidence interval: 0.16-0.62, p = .0007), 0.42 (0.20-0.88, p = .02), and 0.33 (0.14-0.81, p = .02), respectively. CONCLUSION: Regular SF intake between 1 and 2 months of age in infants avoiding cow's milk formula was significantly associated with a reduced risk of food sensitization in infancy.

A 60-minute dosing interval is safer than a 30- or 40-minute interval in oral food challenge.

BACKGROUND: The interval between antigen ingestion may influence the safety of oral food challenge tests (OFCs), especially in patients with severe food allergies. METHODS: This retrospective chart review of OFCs eliciting objective reactions to wheat, egg, and milk that were performed between April 2012 and January 2021 evaluated an equivalent number of low-dose OFCs performed at 30-, 40-, or 60-min intervals. To avoid the influence of the potential allergy severity of the patients, the prediction scores of all intervals were matched. We evaluated the total symptom score (TS), total ingested dose, and the proportions of severe reactions (TS ≥ 30) and adrenaline use. RESULTS: We analyzed 945 OFCs (wheat, n = 186; egg, n = 561; milk, n = 198). The 60-min OFC had significantly lower TS than the 30- and 40-min OFC methods in wheat (p < 0.001 and p = 0.003, respectively), egg (p < 0.001 for both), and milk (p < 0.001 and p = 0.018, respectively). The total dose in the 60-min method was significantly lower than in the 30-min method (p < 0.001 for all). The proportion of severe reaction (TS ≥ 30) in the 60-min method was significantly lower than that in the 30-min method for the egg and milk OFCs (p = 0.001 and p < 0.001, respectively). There was no difference in the rates of adrenaline injection. CONCLUSIONS: The 60-min interval is safer than 30- or 40-min intervals in wheat, egg, and milk OFCs in patients with a low threshold dose for food allergy.

The clinical cross-reactivity and immunological cross-antigenicity of wheat and barley.

BACKGROUND: Some patients with wheat allergy have been reported to show clinical cross-reactivity to barley. However, it is not clear whether the development of barley allergy in patients with wheat allergy is due to cross-antigenicity between wheat and barley. This study aimed to determine the clinical cross-reactivity and immunological cross-antigenicity of wheat and barley. METHODS: The results of barley oral food challenges (OFCs) were compared before and after oral immunotherapy (OIT) for wheat in nine patients with wheat allergy to estimate the clinical cross-reactivity of wheat and barley. Moreover, we performed enzyme-linked immunosorbent assay (ELISA) inhibition and immunoblotting inhibition using serum from seven patients allergic to wheat and barley. RESULTS: Nine patients who had positive barley-OFC results performed before OIT for wheat were all negative on barley-OFC performed after OIT. In ELISA inhibition, preincubation of serum from patients allergic to wheat and barley with a high barley extract concentration inhibited binding of IgE to wheat extract by less than 10%. On the other hand, wheat and barley extracts equally inhibited binding to barley sIgE at high concentrations. In the immunoblotting inhibition test, the spots of wheat were inhibited but weakly by barley extracts, and most of the spots of barley were inhibited even by low concentrations of the wheat and barley extract. CONCLUSIONS: We showed that barley allergy associated with wheat allergy is caused by cross-reactivity from wheat. The OIT for wheat is one of the promising options for barley allergy.

[COMPARISON OF WHEAL SIZE INDUCED BY BIFURCATED NEEDLE® AND SMARTPRACTICE® PRICK LANCET].

BACKGROUND: There is reportedly a difference in the diameter of the skin reaction induced by different types of skin prick test (SPT) devices. We compared the SPT diagnostic accuracy and wheal size between a Bifurcated Needle® (BN) and SmartPractice® Prick Lancet (PL), which are commercially available in Japan. METHODS: An SPT was performed on 15 adults with and 10 without subjective symptoms of cedar pollinosis who wished to be examined for Japanese cedar pollen (JCP) sensitization. The SPT was performed blindly with a BN or PL with 10mg/ml of histamine dihydrochloride, 50% glycerosaline control, and JCP extract solution (TORII PHARMACEUTICAL CO., LTD., Tokyo, Japan). The wheal sizes induced by the BN and PL were then compared. The JCP-specific IgE antibody titer was measured to compare the sensitivity and specificity of the SPT. RESULTS: Histamine wheal diameters were 6.0 (5.5-6.5) mm by BN and 6.0 (5.5-6.5) mm by PL (p=0.67), and none of the negative control solutions induced wheal. The respective sensitivity and specificity for cedar sensitization were 100% and 86% for BN, 100% and 79% for PL, and the areas under the ROC curve were 0.72 and 0.69 (p=0.32). CONCLUSION: The diagnostic accuracy of cedar pollen extract based on specific IgE-JCP sensitization and the diameter of the wheal produced by a BN and PL were considered equivalent.

Purification and molecular characterization of a truncated-type Ara h 1, a major peanut allergen: oligomer structure, antigenicity, and glycoform.

Peanut allergies are among the most severe food allergies, and several allergenic proteins referred to as Ara h 1-Ara h 17 have been identified from peanut seeds. The molecular characterization of Ara h 1 (63 kDa), a glycosylated allergen, has almost been completed, and the occurrence of two homologous genes (clone 41B and clone P17) has been identified. In this study, we found a new variant of Ara h 1 i.e. 54 kDa, in which the N-terminal amino acid sequence was EGREGEQ-, indicating that the N-terminal domain of 63 kDa Ara h 1 had been removed. This new isoform was obtained from the run-through fraction of hydrophobic interaction chromatography while 63 kDa Ara h 1 was tightly bound to the hydrophobic resins, suggesting that the removal of the N-terminal domain resulted in extreme hydrophilic properties. We found that 63 kDa Ara h 1 occurs as higher order homo-oligomeric conformations such as decamer or nonamer, while 54 kDa Ara h 1 occurs exclusively as a homotrimer, indicating that the N-terminal domain of the 63 kDa molecule may be involved in higher order oligomerization. When antisera from peanut-allergic patients were treated with both the Ara h 1 molecules, the immunoglobulin E (IgE) antibodies in these sera reacted with each Ara h 1 molecule, suggesting that the C-terminal as well as the N-terminal domains of Ara h 1 contribute significantly to the epitope formations of this peanut glycoallergen. Furthermore, the glycoform analyses of N-glycans linked to 63 kDa and 54 kDa Ara h 1 subunits revealed that both typical high-mannose type and ß-xylosylated type N-glycans are linked to the molecules. The cross-reactivity of IgE against Ara h 1 in the serum of one peanut allergy patient was completely lost by de-N-glycosylation, indicating the N-glycan of Ara h 1 was the sole epitope for the Ara h 1- specific IgE in the patient.

Exercise-induced allergic reactions after achievement of desensitization to cow's milk and wheat.

BACKGROUND: We have previously reported that more than half of the patients who achieved desensitization after wheat rush oral immunotherapy (OIT) developed exercise-induced allergic reaction on desensitization (EIARD). However, data on EIARDs after slow OIT are lacking. Therefore, this study aimed to investigate the results of exercise provocation tests (EPTs) in patients after slow OIT for cow's milk and wheat allergies. METHODS: This was a retrospective chart review of 87 EPTs in 74 patients. The EPTs were performed in patients who were desensitized to at least 6,600 mg cow's milk protein or 5,200 mg wheat protein with slow OIT and were identified to be at a high risk of EIARDs. EPTs were performed after ingestion of the maximum desensitization dose. The patients' clinical characteristics and symptoms were analyzed. RESULTS: The EPT results were positive for cow's milk in 49% (21/43) of the patients and for wheat in 48% (15/31) of the patients. There was no significant difference in the clinical characteristics between the EIARD-positive and EIARD-negative groups. The specific IgE (sIgE) levels before OIT and the reduction rates of sIgE before and after OIT did not correlate with the outcomes of the EPTs. Among the EIARD-positive patients, 13 patients (cow's milk, n = 7; wheat, n = 6) underwent a second EPT, and the EIARD disappeared in 8 patients (cow's milk, n = 4; wheat, n = 4). CONCLUSION: EIARDs were observed after slow OIT for cow's milk and wheat. Further research into the predictive factors of EIARDs in these patients is needed to understand its clinical manifestations.

Evaluation of cross-reactivity between casein components using inhibition assay and in silico analysis.

BACKGROUND: We previously reported that the specific IgE levels to αs1-casein (CN) and ß-CN in patients with cow's milk allergy decreased with similar dynamics during oral immunotherapy. Therefore, we hypothesized that αs1- and ß-CN have strong cross-reactivity among CN components, despite the low similarity in the full-length amino acid sequences. METHODS: The αs1-, ß-, and κ-CN were purified from commercial cow's milk. We recruited 39 patients with cow's milk allergy, and the serum IgE levels for each CN component were measured by enzyme-linked immunosorbent assay (ELISA). Cross-reactivity between CN components was investigated by competitive ELISA against αs1-CN. Sequence homology between CN components at the peptide level was calculated using in silico analysis and quantified by the property distance (PD) value. RESULTS: The αs1-CN-specific IgE levels exhibited a strong positive correlation with the ß-CN-specific IgE (r = 0.945, P < .001). Complete competition was observed by ß-CN against αs1-CN, suggesting the presence of common epitopes between them. In silico analysis detected 24 peptide sets with PD values lower than 10 between αs1- and ß-CN, and 14 sets between αs1- and κ-CN. The amino acid sequences of αs1-CN (E61-E70) and ß-CN (I12-E21) that showed the lowest PD value (5.30) were present in the characteristic sequence known as casein phosphopeptide (CPP). CONCLUSION: We detected strong cross-reactivity between CN components. Furthermore, we found highly homologous sequences in the CPP region, which contains a core sequence of "SSSEE" with phosphorylated serine residues.

Efficacy, safety, and parental anxiety in a randomized trial of two dietary instruction methods for children with suspected hen's egg allergy.

BACKGROUND: Little has been reported on how to introduce hen's egg into the diet of children with suspected egg allergy. We compared the efficacy, safety, and parental anxiety of two different dietary instruction methods to introduce egg. METHODS: Eligible participants were children aged 1-4 years who were positive for egg white IgE, and ovomucoid IgE <3.5 kUA/L. Participants were either naïve in egg consumption or had a history of an immediate, but non-anaphylactic, allergic reaction to egg. After a negative result of baseline 2 g boiled egg white oral food challenge (OFC), participants were randomly assigned to the step-up OFC testing (SOFT) or home incrementing group. The primary outcome was the proportion of participants who were able to ingest 20 g of boiled egg white 6 months after initiation. This study is registered with the University Hospital Medical Information Network clinical trial registry (UMIN000024192). RESULTS: Between September 2016 and August 2018, we randomly allocated 55 participants to the SOFT (n = 33 [60%]) and home incrementing (n = 22 [40%]) groups and analyzed 51 patients. Four patients were excluded because they were lost to follow-up. Thirty-one (96.9%) of 32 participants in the SOFT and 12 (63.2%) of 19 in the home incrementing group achieved the primary outcome (p = 0.003). No serious adverse reactions were observed in either group. Parental anxiety significantly improved during treatment in both groups. CONCLUSIONS: The SOFT method was more effective than home incrementing as dietary instruction to introduce egg in children with suspected egg allergy.

[A CASE OF PANCAKE SYNDROME IN WHICH MITES COULD BE DETECTED FROM COOKED TAKOYAKI].

A 12-year-old girl experienced anaphylactic shock and respiratory failure immediately after eating 4 pieces of takoyaki made at home. We suspected pancake syndrome because of the three reasons: First, the patient had a history of bronchial asthma and allergic rhinitis without any history of food allergies; Second, takoyaki flour that had been stored at room temperature for one month after opening the package had been used; and Third, both the specific IgE (ImmunoCAP® method) of Dermatophagoides farinae and Dermatophagoides pteronyssinus were found to be above the detection limit. Since the suspected flour had been discarded, a specimen of tako yaki was examined microscopically and 430 mites/g were identified. Although only 21.1ng/g of Der f 1 was detected by an ELISA, this amount was less than expected, based on the number of mites that had been observed. The decrease in the antigenicity of mite allergens due to heating and reducing agents, and the insolubilization of mite allergens due to disulfide bonds between the mite allergens and gluten were thought have made it difficult to identify mite antigens by ELISA.When pancake syndrome is suspected, and the flour that is thought to have caused the condition is difficult to obtain, microscopic identification of mites in cooked food should be considered.

Exercise-induced allergic reactions on desensitization to wheat after rush oral immunotherapy.

BACKGROUND: The effect of oral immunotherapy (OIT) on wheat allergy is promising in terms of the potential to obtain desensitization; however, the frequency of exercise-induced allergic reactions on desensitization (EIARDs) and the associated risk factors remain to be determined. METHODS: Twenty-five patients underwent rush OIT for wheat allergy, and 21 achieved the full-dose intake of wheat products (5 g of wheat protein). Exercise-provocation tests were repeatedly performed after the ingestion of a full-dose wheat product. The time-course of the levels of the specific IgEs (sIgE) to wheat extract, total gliadin, deamidated gliadin, recombinant gliadin components (α/ß-, γ- and ω-5-), and glutenin (high and low molecular weight) components was analyzed using ImmunoCAP® , ELISA, or IgE immunoblotting. RESULTS: Fourteen patients (66.7%) were diagnosed as EIARD+, which remained 5 years after rush OIT in 11 patients (52.4%). There were no differences in the clinical backgrounds of the EIARD+ and EIARD- patients. However, EIARD+ patients showed significantly higher sIgE levels to all gliadin and glutenin components than EIARD- patients before OIT. The sIgE levels to each component decreased equally after 1 and 2 years of OIT. On IgE immunoblotting, sera from all patients reacted to the multiple gluten bands, and some reacted to the water-soluble bands. The intensity of all IgE-reactive bands also became equally lighter after OIT. CONCLUSIONS: EIARDs were frequently observed and remained for a long period after successful OIT for wheat allergy. None of the specific wheat components were found to contribute to EIARDs.

Slow low-dose oral immunotherapy: Threshold and immunological change.

BACKGROUND: We examined the feasibility, efficacy and safety of slow low-dose oral immunotherapy (SLOIT) for egg, milk, wheat allergies, with accepted severity-stratified initial and maintenance doses. METHODS: Children with food allergies defined by low-dose oral food challenges (LD-OFCs) to hen's egg (cumulative protein dose up to 983 mg, n = 133), cow's milk (287 mg, n = 50), and wheat (226 mg, n = 45) were recruited. Participants were divided into two groups [SLOIT and control (complete avoidance]) based on their preferences. Participants who selected SLOIT were instructed to take the safe dose daily, with monthly increases, aiming to increase the dose by 10 times in one year. The primary outcome was the proportion of participants who passed the LD-OFCs following 1 year of therapy. RESULTS: The participants in SLOIT group ingested their antigen 92.9% of the therapy's day on average. The proportion of participants who passed LD-OFCs was 35.9% (61/170) in the SLOIT group and 8.7% (4/46) in the control group (P < .001); no large differences were observed among allergens. Among the subjects who failed LD-OFCs, the median change in the total dose in the LD-OFC was 235% (interquartile range: 100%-512%) in the SLOIT group and 100% (42%-235%) in the control group (P < .001). Provoked allergic symptoms were observed in only 0.58% (280/48,486) per programmed intake and approximately 50% of the SLOIT group did not experience any obvious allergic symptoms throughout therapy. CONCLUSIONS: SLOIT showed significant feasibility, efficacy and safety, providing a promising option to manage patients with severe food allergies.

Food allergy is linked to season of birth, sun exposure, and vitamin D deficiency.

The season of birth and ultraviolet B exposure have been related to the occurrence of food allergy. The levels of vitamin D produced from skin by ultraviolet B exposure might reflect this relationship. Vitamin D is known to induce antimicrobial peptides, protect intestinal flora, enhance the gut epithelial barrier, suppress mast cell activation and IgE synthesis from B cells, and increase the number of tolerogenic dendritic cells and IL-10-producing regulatory T cells. Vitamin D deficiency has been shown to exacerbate sensitization and allergic symptoms in a murine model of food allergy. However, in clinical situations, contradictory observations have been reported regarding the relationship between food allergy and vitamin D deficiency/supplementation. In this review, we have explored the links between food allergy and vitamin D levels. One explanation for the discrepant findings is confounding factors such as race, age, residency, skin color, and epigenetic changes that contribute to vitamin D levels. In addition, the season of birth influences the development of atopic dermatitis, which could lead to food sensitization. Finally, ultraviolet radiation could lead to regulatory T cell expansion and immunosuppression, irrespective of vitamin D status. Based on our current understanding, we believe that correction of vitamin D deficiency by supplementation, appropriate skin care, and sufficient ultraviolet radiation exposure could alter the prognosis of food allergy. To identify potential treatment strategies for food allergy, it is essential to gain a better understanding of the appropriate levels of vitamin D and ultraviolet radiation exposure.

Surveillance of the use of adrenaline auto-injectors in Japanese children.

BACKGROUND: The appropriate usage of an adrenaline auto-injector (AAI, Epipen®) is a key aspect of patient and social education in the management of anaphylaxis. However, although AAIs are being prescribed increasingly frequently, there are few reports on their actual use. METHODS: The Anaphylaxis Working Group of the Japanese Society of Pediatric Allergy and Clinical Immunology requested that society members register cases in which AAIs were used. Two hundred and sixty-six cases were collected from March 2014 to March 2016. RESULTS: The cases included 240 events of immediate-type food allergies caused by cow's milk (n = 100), hen's egg (n = 42), wheat (n = 40), and peanuts (n = 11). Exercise-related events were reported in 19 cases; however, the diagnosis of food-dependent exercise-induced anaphylaxis with a specific causative food was only made in 4 cases (wheat, n = 2; fish, n = 1; squid, n = 1). The frequent reasons for the causative intake included programmed intake (n = 48), failure to check the food labeling (n = 43), and consuming an inappropriate food (n = 26). AAIs were used at schools or nurseries in 67 cases, with school or nursery staff members administering the AAI in 39 cases (58%). On arriving at the hospital, the symptom grade was improved in 71% of the cases, while grade 4 symptoms remained in 20% of the cases. No lethal cases or sequelae were reported. CONCLUSIONS: AAIs were used effectively, even by school teachers. The need to visit a hospital after the use of an AAI should be emphasized because additional treatment might be required.

Immune suppression of food allergy by maternal IgG in murine models.

BACKGROUND: Most of the patients develop food allergy early in life. The factors related to parental immune condition might be one of the conceivable causes. METHODS: We reported murine models of food allergy and oral OVA tolerance. To investigate the influence of parental immune condition on infant food allergy, female and male mice with food allergy or oral tolerance were mated with each other. RESULTS: Food allergy was suppressed by decreased IgE production in the offspring of mice with food allergy. On the contrary, anaphylaxis for OVA was induced in the offspring of mice with oral tolerance. The suppression of food allergy being dependent on a maternal factor was revealed in the offspring after cross-mating mice with food allergy and oral tolerance. Because OVA-specific IgG, presumed to be from the allergic mother, was detected in the serum of naïve infants from mothers allergic to food, we assumed that the suppression was dependent on a specific IgG. The serum IgG purified by a G-protein column was administered before OVA sensitization in the food allergy model, and OVA-specific IgE production was found to be diminished in the administered mice. However, OVA-specific monoclonal IgG1 and IgG2a administration could not suppress food allergy. Because we detected OVA-IgG immune complex in the serum of mothers allergic to food, it might be a cause of maternal immune suppression. CONCLUSIONS: We demonstrated that maternal specific IgG conjugated food antigen is an important factor related to the development of food allergy and acquiring tolerance.