Almond (Prunus dulcis) allergen Pru du 8, the first member of a new family of food allergens.
An almond allergen with 2 known short peptide sequences was reported as the almond 2S albumin but was later suspected to be almond vicilin. However, this allergen was designated by WHO/IUIS. This study aimed to determine the true identity of this elusive almond allergen. cDNAs were synthesized from total RNA of the Nonpareil almond. The complete sequence of the previously reported almond allergen was determined from its coding sequence. The deduced protein was produced recombinantly, and it was confirmed to be a food allergen by testing with 18 almond-allergic sera. The allergen is a potential cysteine-rich antimicrobial protein with characteristic C[X]3C-[X]10-12-C[X]3C motifs of the hairpinin antimicrobial protein. This first member of a novel family of food allergens was named Pru du 8. The signature motif of the hairpinin antimicrobial protein can be found in the N-terminal region of some vicilin allergens (e.g., Ara h 1). It can also be found in the signal peptide of other vicilin allergens (e.g., Car i 2). In many species, however, vicilins do not contain such a motif, indicating that the presence of the signature motifs of the hairpinin antimicrobial protein in vicilins might be a result of translocation during evolution.
SPT predictive values for the outcome of cashew challenges in children.
BACKGROUND: Cashew is a common cause of tree nut allergy in children. To date there have been few studies of diagnostic tests for cashew allergy, and positive predictive values (PPVs) for cashew as well as other tree nuts are largely extrapolated from studies of peanut allergy. How relevant these cut-offs are for cashew has not been formally explored. OBJECTIVE: We aimed to establish skin prick test (SPT) wheal sizes that correlated to 95% PPV for a positive food challenge for cashew. METHODS: We included all cashew oral food challenges (OFC) conducted as part of the HealthNuts (n=108, age 4-6 years) and SchoolNuts (n=37, age 10-14 years) studies, both recruited from the community (Population cohort). A second cohort of all cashew OFCs conducted at the Royal Children's Hospital (RCH) allergy centre (n=343) (2011-2016) and a private allergy clinic based at RCH (n=43) was included via electronic medical record review (Clinic cohort). 95% PPV for cashew SPT was calculated for both cohorts. RESULTS: Among the population cohort (n=145), 62% of cashew OFC were positive compared to 20% of the clinic cohort (n=386). The SPT cut-off for 95% PPV derived from the population cohort was 10mm (95%CI 7.5-12.0). For the clinic cohort the 95% PPV was 14mm (95%CI 9.5-unknown). A SPT wheal size of 8mm had a PPV of 89% (95%CI 79-95) in the population cohort and 62% (95%CI 45-78) in the clinic cohort. CONCLUSION: A higher SPT wheal size may be more appropriate than the commonly used 8mm cut-off to guide clinical decisions around when to perform OFC for cashew.
Pistachio and cashew nut allergy in childhood: Predictive factors towards development of a decision tree.
BACKGROUND: Pistachio and cashew nut, which belong to the same botanical family, are tree nuts that induce serious allergic reactions. OBJECTIVE: We aimed to determine the predictive factors for pistachio and cashew nut reactivity during oral food challenge (OFC). METHODS: A total of 112 pistachio and/or cashew nut sensitized children, aged 58.45 (IQR:40.38-88.32) months, were included. Cutoff values and probability curves for skin prick test (SPT), sIgE, sIgE/Total IgE that predict reactivity were determined for pistachio and cashew nut. Additionally, a diagram was created that can be useful while making a decision for OFC based on SPT and sIgE values. RESULTS: A total of 73 patients underwent OFC with pistachio and/or cashew nut. Twelve children with current anaphylaxis history were not challenged and accepted as allergic. SPT was the only predictive factor for positive pistachio/ cashew nut OFC. According to area under curve (AUC) analysis, SPT was more predictive than sIgE and sIgE/Total IgE both for pistachio and cashew nut. Optimal cutoff values according to "Youden index" for pistachio SPT, sIgE, and sIgE/ Total IgE were 7.25 mm, 4.14 kUA/L, and 1.32%, respectively. And those values for cashew nut SPT, sIgE, and sIgE/Total IgE were 6.25 mm, 1.125 kUA/L, and 3.30%, respectively. The diagram showed that SPT predicted the reactivity together with sIgE better than only the SPT values. CONCLUSION: SPT was the best predictor for reactivity both for pistachio and cashew nut. Combined use of SPT and sIgE may improve the prediction of reactivity at pistachio and cashew nut OFCs in children.
Peanut allergy and oral immunotherapy.
Peanut allergy is the commonest cause of food-induced anaphylaxis in the world, and it can be fatal. There have been many recent improvements to achieve safe methods of peanut desensitisation, one of which is to use a combination of anti-immunoglobulin E and oral immunotherapy. We have treated 27 patients with anti-immunoglobulin E and oral immunotherapy, and report on the outcomes and incidence of adverse reactions encountered during treatment. The dose of peanut protein tolerated increased from a median baseline of 5 to 2000 mg after desensitisation, which is substantially more than would be encountered through accidental ingestion. The incidence of adverse reactions during the escalation phase of oral immunotherapy was 1.8%, and that during the maintenance phase was 0.6%. Most adverse reactions were mild; three episodes were severe enough to warrant withdrawal from oral immunotherapy, but none required epinephrine injection. Preliminary data suggest that unresponsiveness is lost when daily ingestion of peanuts is stopped after the maintenance period.
Identification of a natural ligand of the hazel allergen Cor a 1.
Hazelnut is one of the most frequent causes of food allergy. The major hazel allergen in Northern Europe is Cor a 1, which is homologous to the major birch pollen allergen Bet v 1. Both allergens belong to the pathogenesis related class PR-10. We determined the solution structure of Cor a 1.0401 from hazelnut and identified a natural ligand of the protein. The structure reveals the protein fold characteristic for PR-10 family members, which consists of a seven-stranded antiparallel β-sheet, two short α-helices arranged in V-shape and a long C-terminal α-helix encompassing a hydrophobic pocket. However, despite the structural similarities between Cor a 1 and Bet v 1, they bind different ligands. We have shown previously that Bet v 1 binds to quercetin-3-O-sophoroside. Here, we isolated Cor a 1 from hazel pollen and identified the bound ligand, quercetin-3-O-(2"-O-β-D-glucopyranosyl)-β-D-galactopyranoside, by mass spectrometry and nuclear magnetic resonance spectroscopy (NMR). NMR experiments were performed to confirm binding. Remarkably, although it has been shown that PR-10 allergens show promiscuous binding behaviour in vitro, we can demonstrate that Cor a 1.0401 and Bet v 1.0101 exhibit highly selective binding for their specific ligand but not for the respective ligand of the other allergen.
Comparison of recovery and immunochemical detection of peanut proteins from differentially roasted peanut flour using ELISA.
The effect of heat on extractability and immunoreactivity of proteins from roasted peanut flours and whole peanuts was evaluated using two general protein assays and six commercial peanut ELISA kits, respectively. The highest amount of protein was recovered from roasted peanuts with all ELISAs, while recovery showed a decrease with increasing levels of roasting of the peanut flours. Only the Morinaga kit showed sufficient sensitivity to detect peanut at low concentrations of the dark roast peanut flours. Both the protein and immunoassays indicated a decrease in protein solubility with roasting. The underestimation by immunoassays is a combination of decreased solubility and heat induced changes in the proteins that are being targeted by the ELISA antibodies. These findings suggest that most commercial ELISA kits may not reliably quantify peanut present in dark roast peanut flours at ≤25 ppm.
Timing of Food Introduction and the Risk of Food Allergy.
Given that the prevalence of pediatric IgE-mediated food allergies (FA) has followed a substantive increase in recent decades, nowadays, a research challenge is to establish whether the weaning strategy can have a role in FA prevention. In recent decades, several studies have demonstrated that delayed exposure to allergenic foods did not reduce the risk of FA, leading to the publication of recent guidelines which recommend against delaying the introduction of solid foods after 4-6 months of age, both in high- and low-risk infants, in order to prevent food allergy. In the present review, focusing on cow's milk protein, hen's eggs, peanuts, soy, wheat and fish, we describe the current scientific evidence on the relationship between timing of these foods' introduction in infants' diet and allergy development.
Clinical Factors Associated with Peanut Allergy in a High Risk Infant Cohort.
BACKGROUND: Prognostication of peanut allergy (PNA) is relevant for early interventions. We aimed to determine baseline parameters associated with development of PNA in 3-15 month olds with likely egg and/or milk allergy, and/or moderate-severe atopic dermatitis (AD) and a positive egg/milk skin prick test (SPT), but no known PNA. METHODS: The primary endpoint was PNA [confirmed/convincing diagnosis or last classified as serologic PNA (<2 yrs, ≥5 kUA/L, otherwise ≥14 kUA/L, peanut-IgE)] among 511 participants (median follow-up, 7.3 years). Associations were explored with univariate logistic regression; factors with p<0.15 were analyzed by stepwise multiple logistic regression, using data stratified by PNA status and randomly assigned to development and validation datasets. RESULTS: 205/511 (40.1%) had PNA. Univariate factors associated with PNA (p<0.01) included: increased AD severity, larger egg and peanut SPT, greater egg, milk, peanut, Ara h1-h3 IgE, higher peanut IgG and IgG4, and increased pregnancy peanut consumption. P-values were between 0.01 and 0.05 for younger age, non-white race, lack of breastfeeding, and increased lactation peanut consumption. Using a development dataset, the multivariate model identified younger age at enrollment, greater peanut and Ara h2 IgE, and lack of breastfeeding as prognosticators. The final model predicted 79% in the development and 75% in the validation dataset (AUC=0.83 for both). Models using stricter or less strict PNA criteria both found Ara h2 as predictive. CONCLUSIONS: Key factors associated with PNA in this high risk population included lack of breastfeeding, age, and greater Ara h2 and peanut-specific IgE, which can be used to prognosticate outcomes.
Current management and use of oral immunotherapy in the United States for patients with peanut allergy.
BACKGROUND: Peanut allergy is a major health burden in the United States. Treatment is limited to avoidance and acutereaction management. No drug or medical product is approved for use as a peanut oral immunotherapy (POIT) agent. OBJECTIVE: To examine peanut allergy diagnosis and treatment, peanut challenge protocols, nonpublished POIT approaches, POIT practice requirements and logistical considerations, and barriers to providing POIT. METHODS: Qualitative in-depth telephonic interviews were conducted with 34 allergists and nurse food allergy specialistsacross the United States between April and June 2016. Interviewed clinicians managed > 100 patients with peanut allergy per year; 50% of the interviewed allergists offered POIT in clinical studies or used self-developed approaches. RESULTS: The physicians consistently reported conducting food challenges in 5-10% of patients to confirm a peanut allergydiagnosis. The allergists who offered POIT described using a variety of approaches. Areas of divergence included patientselection (ages, 4-7 years), peanut material (crushed peanuts, peanut flour, peanut protein, peanut butter, peanut extract),starting and ending doses, and updosing intervals (1 to 2 weeks). Generally, POIT administration and observation occupiedan examination room for up to 2 hours; some practices reported accommodating 2 to 5 patients who received POIT simultaneously. Among physicians who did not offer POIT, barriers included medicolegal risks and the lack of a U.S. Food and Drug Administration (FDA) approved therapy. CONCLUSION: Although POIT is currently not supported in treatment guidelines, some allergists have developed experimental POIT approaches to support patient needs. In the absence of a product that has approval by the FDA, EuropeanMedicines Agency (EMA) or other national competent authority, substantial variability in POIT approaches exists. Althoughlogistical factors are not major obstacles to adoption, POIT dose preparation can be perceived as burdensome, and observationrequires a dedicated staff. All the physicians interviewed suggested a need for effective, FDA-approved, disease-modifyingtreatments.
Food allergy endotype with high risk of severe anaphylaxis in children-Monosensitization to cashew 2S albumin Ana o 3.
BACKGROUND: Food allergy in children can be life-threatening. Component-resolved diagnostics approach to food anaphylaxis is rarely assessed in children. The aim of the study was to identify the food allergen components as the triggers responsible for severe anaphylaxis, with regard to characteristics and associated risks, among children in a large, population-based setting. METHODS: Two hundred and seventy-one children who were hospitalized due to systemic allergic reaction (SAR) and food anaphylaxis were recruited. Medical history was assessed, and culprit allergen source and anaphylaxis severity grade were established. Specific IgE to 112 allergen components using multiplex ImmunoCAP ISAC immunoassay and specific IgE to hazelnut, Cor a 14, and cashew, Ana o 3, using singleplex ImmunoCAP immunoassay were determined. RESULTS: We analyzed data from 237 SAR/anaphylaxis in 237 children. Trigger at allergen component level was defined for every episode. The most common triggers of SAR/anaphylaxis were seeds (50.6%), among them, the storage proteins. Anaphylaxis triggered by Ana o 3, 2S albumin from cashews (aOR = 15.0; 95% CI: 3.27 to 73.47); Tri a 19 from wheat (aOR = 9.93; 95% CI: 1.73 to 56.97); and Cor a 9 from hazelnut (aOR = 6.53; 95% CI: 1.16 to 36.72) had the worst clinical presentation including cardiovascular and severe respiratory symptoms (grade IV-V vs I-III in Cox scale). Thirteen out of 237 (5.5%) SAR/anaphylaxis patients were triggered by Ana o 3. Almost 82% of patients with severe Ana o 3 anaphylaxis were sensitized only to this component and had no concomitant food sensitization. CONCLUSION: Monosensitization to Ana o 3 is, irrespective of other parameters, connected with high risk of severe anaphylaxis.