In house validation of a high resolution mass spectrometry Orbitrap-based method for multiple allergen detection in a processed model food.
In recent years, mass spectrometry (MS) has been establishing its role in the development of analytical methods for multiple allergen detection, but most analyses are being carried out on low-resolution mass spectrometers such as triple quadrupole or ion traps. In this investigation, performance provided by a high resolution (HR) hybrid quadrupole-Orbitrap™ MS platform for the multiple allergens detection in processed food matrix is presented. In particular, three different acquisition modes were compared: full-MS, targeted-selected ion monitoring with data-dependent fragmentation (t-SIM/dd2), and parallel reaction monitoring. In order to challenge the HR-MS platform, the sample preparation was kept as simple as possible, limited to a 30-min ultrasound-aided protein extraction followed by clean-up with disposable size exclusion cartridges. Selected peptide markers tracing for five allergenic ingredients namely skim milk, whole egg, soy flour, ground hazelnut, and ground peanut were monitored in home-made cookies chosen as model processed matrix. Timed t-SIM/dd2 was found the best choice as a good compromise between sensitivity and accuracy, accomplishing the detection of 17 peptides originating from the five allergens in the same run. The optimized method was validated in-house through the evaluation of matrix and processing effects, recoveries, and precision. The selected quantitative markers for each allergenic ingredient provided quantification of 60-100 μgingred/g allergenic ingredient/matrix in incurred cookies.
Genome-wide association study and meta-analysis in multiple populations identifies new loci for peanut allergy and establishes C11orf30/EMSY as a genetic risk factor for food allergy.
BACKGROUND: Peanut allergy (PA) is a complex disease with both environmental and genetic risk factors. Previously, PA loci were identified in filaggrin (FLG) and HLA in candidate gene studies, and loci in HLA were identified in a genome-wide association study and meta-analysis. OBJECTIVE: We sought to investigate genetic susceptibility to PA. METHODS: Eight hundred fifty cases and 926 hyper-control subjects and more than 7.8 million genotyped and imputed single nucleotide polymorphisms (SNPs) were analyzed in a genome-wide association study to identify susceptibility variants for PA in the Canadian population. A meta-analysis of 2 phenotypes (PA and food allergy) was conducted by using 7 studies from the Canadian, American (n = 2), Australian, German, and Dutch (n = 2) populations. RESULTS: An SNP near integrin α6 (ITGA6) reached genome-wide significance with PA (P = 1.80 × 10-8), whereas SNPs associated with Src kinase-associated phosphoprotein 1 (SKAP1), matrix metallopeptidase 12 (MMP12)/MMP13, catenin α3 (CTNNA3), rho GTPase-activating protein 24 (ARHGAP24), angiopoietin 4 (ANGPT4), chromosome 11 open reading frame (C11orf30/EMSY), and exocyst complex component 4 (EXOC4) reached a threshold suggestive of association (P ≤ 1.49 × 10-6). In the meta-analysis of PA, loci in or near ITGA6, ANGPT4, MMP12/MMP13, C11orf30, and EXOC4 were significant (P ≤ 1.49 × 10-6). When a phenotype of any food allergy was used for meta-analysis, the C11orf30 locus reached genome-wide significance (P = 7.50 × 10-11), whereas SNPs associated with ITGA6, ANGPT4, MMP12/MMP13, and EXOC4 and additional C11orf30 SNPs were suggestive (P ≤ 1.49 × 10-6). Functional annotation indicated that SKAP1 regulates expression of CBX1, which colocalizes with the EMSY protein coded by C11orf30. CONCLUSION: This study identifies multiple novel loci as risk factors for PA and food allergyand establishes C11orf30 as a risk locus for both PA and food allergy. Multiple genes (C11orf30/EMSY, SKAP1, and CTNNA3) identified by this study are involved in epigenetic regulation of gene expression.
Should Younger Siblings of Peanut Allergic Children Be Screened for Peanut Allergy?
The role of screening younger siblings of peanut allergic children with allergy testing before peanut introduction is controversial. Although certain guidelines note some value in screening this population, it is not a direct indication in the recent National Institute of Allergy and Infectious Diseases guideline. Some studies suggest that siblings of peanut allergic children are at increased risk of peanut allergy, whereas others note that delayed ingestion or mislabeling of allergy in these children may be the main factors accounting for this increased risk. The low risk of severe reaction with first ingestion and risks of pre-emptive testing must be balanced against data suggesting that families are reluctant to introduce peanut in siblings without testing. The goal of this article is to critically appraise the debated issues in this topic, providing a practical approach to this common clinical dilemma.
Pine nut allergy in Korean children: Clinical characteristics and diagnostic values of specific IgE against pine nuts.
BACKGROUND: Hypersensitivity reactions to pine nuts in children have been occasionally encountered recently, although reports on pine nut allergy cases are rare worldwide. The study aimed to feature clinical and laboratory findings pertaining to pine nut allergy in Korean children. METHODS: Forty-two subjects were enrolled through a retrospective review of medical records, from September 2010 to December 2015, at the Department of Pediatrics in Ajou University Hospital. The demographic profiles, clinical characteristics, and laboratory findings were evaluated. RESULTS: Twenty-four patients showed immediate-type reactions after exposure to pine nuts (the allergic group), while the remaining 18 were atopic controls, who exhibited no allergic symptoms (the tolerant group). The median age of the subjects in the allergic group was three years. More than half of the subjects in this group experienced allergic symptoms within 5min, and seven of them experienced anaphylaxis. The median level of pine nut-specific immunoglobulin E (sIgE) in the allergic group (1.62kUA/L) was significantly higher (p=0.014) than that in the tolerant group (0.11kUA/L), with an optimal cut-off level of 0.40kUA/L (sensitivity, 66.7% and specificity, 77.8%). The positive decision point of pine nut-sIgE (specificity, 100%) to distinguish the allergic and tolerant groups was 2.84kUA/L. However, there was no difference in pine nut-sIgE levels between the anaphylaxis and non-anaphylaxis cases. CONCLUSION: About 30% of children with pine nut allergy experienced anaphylaxis. The optimal cut-off level of pine nut-sIgE to distinguish the allergic and tolerant groups was 0.40kUA/L and the positive decision point was 2.84kUA/L.
Diagnostic accuracy, risk assessment, and cost‐effectiveness of component‐resolved diagnostics for food allergy: a systematic review.
BACKGROUND: Component-resolved diagnostics (CRD) are promising tools for diagnosing food allergy, offering the potential to determine specific phenotypes and to develop patient-tailored risk profiles. Nevertheless, the diagnostic accuracy of these tests varies across studies; thus, their clinical utility remains unclear. Therefore, we synthesized the evidence from studies investigating the diagnostic accuracy, risk assessment ability, and cost-effectiveness of CRD for food allergy. METHODS: We systematically searched 10 electronic databases and four clinical trial registries for studies published January 2000-February 2017. The quality of included studies was assessed using QUADAS-2. Due to heterogeneity, we narratively synthesized the evidence. RESULTS: Eleven studies met inclusion criteria, altogether recruiting 1,098 participants. The food allergies investigated were cow's milk, hen's egg, peanut, hazelnut, and shrimp. The components with the highest diagnostic accuracy for each allergen, along with their sensitivity-specificity pairs, were: Bos d 4 for cow's milk (62.0% and 87.5%), Gal d 1 for hen's egg (84.2% and 89.8% for heated egg, and 60.6% and 97.1% for raw egg), Ara h 2 for peanut (80.3% and 95.1%), Cor a 14 for hazelnut (100% and 93.8%), and Lit v 1 for shrimp (82.8% and 56.3%) allergy. CONCLUSION: Selected components of cow's milk, hen's egg, peanut, hazelnut, and shrimp allergen showed high specificity, but lower sensitivity. However, few studies exist for each component, and studies vary widely regarding the cut-off values used, making it challenging to synthesize findings across studies. Further research is needed to determine clinically appropriate cut-off values, risk assessment abilities, and cost-effectiveness of CRD approaches.
Risk Factors and Clinical Features in Cashew Nut Oral Food Challenges.
BACKGROUND: Cashew nuts (CN) are capable of causing severe allergic reactions. However, little has been reported about the details of CN oral food challenges (OFC). METHODS: CN-specific IgE (sIgE) levels were measured for 1 year in 66 patients who underwent an OFC with >3 g CN for diagnosis or confirmation of tolerance acquisition between June 2006 and August 2014. We retrospectively analyzed the OFC and patient background. RESULTS: The median (IQR) age of the 66 patients (48 boys/men and 18 girls/women) was 7.0 years (5.7-8.8). Twelve patients (18.2%) had a positive OFC result; 6 of 8 (75%) patients with a history of an immediate reaction to CN failed the OFC. Anaphylaxis was experienced by 5 of these 12 (42%) patients. A history of an immediate reaction to CN and the CN sIgE levels were significantly different for patients with a positive or negative OFC result (p < 0.01). Among patients without a previous immediate reaction to CN, the 95% positive predictive value (PPV) for the CN sIgE level for a positive OFC result was 66.1 kUA/L. CONCLUSIONS: A history of an immediate reaction to CN and high CN sIgE were risk factors for a positive OFC result. The number of positive OFC results was relatively low, but there was a high probability of anaphylaxis. We should consider the indication of OFC carefully for patients with a history of immediate reactions to CN and avoid OFC for patients without such a history whose CN sIgE values are >66.1 kUA/L (95% PPV).
Prediction of the severity of allergic reactions to foods.
BACKGROUND: There is currently considerable uncertainty regarding what the predictors of the severity of diagnostic or accidental food allergic reactions are, and to what extent the severity of such reactions can be predicted. OBJECTIVE: To identify predictors for the severity of diagnostic and accidental food allergic reactions and to quantify their impact. METHODS: The study population consisted of children with a double-blind, placebo-controlled food challenge (DBPCFC) confirmed food allergy to milk, egg, peanut, cashew nut and/or hazelnut. The data was analyzed using multiple linear regression analysis. Missing values were imputed using multiple imputation techniques. Two scoring systems were used to determine the severity of the reactions. RESULTS: 734 children were included. Independent predictors for the severity of the DBPCFC reaction were: age (B=0.04, p=0.001), skin prick test ratio (B=0.30, p<0.001), eliciting dose (B=-0.09, p<0.001), level of specific immunoglobulin E (B=0.15, p<0.001), reaction time during the DBPCFC (B=-0.01, p=0.004), and severity of accidental reaction (B=0.08, p=0.015). The total explained variance of this model was 23.5%, and the eliciting dose only contributed 4.4% to the model. Independent predictors for more severe accidental reactions with an explained variance of 7.3% were: age (B=0.03, p=0.014), milk as causative food (B=0.77, p<0.001), cashew as causative food (B=0.54, p<0.001), history of atopic dermatitis (B=-0.47, p=0.006), and severity of DBPCFC reaction (B=0.12, p=0.003). CONCLUSIONS: The severity of DBPCFCs and accidental reactions to food remain largely unpredictable. Clinicians should not use the eliciting dose obtained from a graded food challenge for the purposes of making risk-related management decisions.
Component resolved diagnostics demonstrates that most peanut allergic individuals could potentially introduce tree nuts to their diet.
BACKGROUND: Nut allergy varies from pollen cross-allergy, to primary severe allergy with life-threatening symptoms. The screening of IgE antibodies to a wide spectrum of allergens, including species-specific and cross-reactive allergens, is made possible via microarray analysis. OBJECTIVE: We sought to study the association of variable IgE sensitization profiles to clinical response in peanut-challenged children and adolescents in a birch-endemic region. In addition, we studied the avoidance of tree nuts and species-specific sensitizations. METHODS: We studied 102 peanut-sensitized patients who underwent a double-blind placebo-controlled challenge to peanut. We analyzed ISAC ImmunoCAP microarray to 112 allergens, singleplex ImmunoCAPs for hazelnut Cor a 14 and cashew Ana o 3, and performed skin prick tests to peanut, tree nuts and sesame seed. We surveyed avoidance diets with a questionnaire. RESULTS: Sensitization to PR-10 proteins was frequent (Bet v 1 90%), but equally high in the challenge negatives and positives. IgE to Ara h 2 and Ara h 6 discriminated peanut allergic (n=69) and tolerant (n=33) the best. Avoidance of tree nuts was common (52 to 96%), but only 6 to 44% presented species-specific sensitizations to tree nuts, so a great number could potentially introduce these species into their diet. CONCLUSIONS AND CLINICAL RELEVANCE: PR-10-sensitizations were frequent and strong regardless of peanut allergy status. Component resolved diagnostics can be employed to demonstrate to patients that sensitization to seed storage proteins of tree nuts is uncommon. Several tree nuts could potentially be reintroduced to the diet.
Thermal processing effects on the IgE-reactivity of cashew and pistachio.
Thermal processing can modify the structure and function of food proteins and may alter their allergenicity. This work aimed to elucidate the influence of moist thermal treatments on the IgE-reactivity of cashew and pistachio. IgE-western blot and IgE-ELISA were complemented by Skin Prick Testing (SPT) and mediator release assay to determine the IgE cross-linking capability of treated and untreated samples. Moist thermal processing diminished the IgE-binding properties of both nuts, especially after heat/pressure treatment. The wheal size in SPT was importantly reduced after application of thermally-treated samples. For cashew, heat/pressure treated-samples still retain some capacity to cross-link IgE and degranulate basophils, however, this capacity was diminished when compared with untreated cashew. For pistachio, the degranulation of basophils after challenge with the harshest heat/pressure treatment was highly decreased. Boiling produced more variable results, however this treatment applied to both nuts for 60 min, led to an important decrease of basophil degranulation.
Prevalence and longitudinal trends of food allergy during childhood and adolescence: results of the Isle of Wight Birth Cohort study
BACKGROUND: The prevalence and time trends of food allergy change during childhood depending on the age of the child and the type of food. OBJECTIVE: To study prevalence and longitudinal trends in food allergy from birth to 18 years in an unselected birth cohort in the Isle of Wight. METHOD: Information on food allergy was collected at ages 1, 2, 4, 10 and 18 years from the Isle of Wight Birth Cohort (n = 1456). Skin prick testing (SPT) was performed at the age of 1 and 2 years in symptomatic children. At 4, 10 and 18 years of age, participants were tested to a panel of food and aero-allergens. Food allergy was diagnosed based on the criteria: symptoms suggestive of a typical IgE mediated reaction and reaction <4 hours following exposure to a known food allergen. McNemar's test was used to determine significance of changes in prevalence over time. RESULTS: The prevalence of food allergy remained relatively constant in early childhood (5.3%, 4.4% and 5.0% at 1, 2 and 4 years respectively), with significant decline at 10 years (2.3%, p<0.001 versus 4 years) followed by significant rise at 18 years (4%, p=0.02 versus 10 years). Cow's milk (1.6-3.5%) and egg (1.1-1.4%) were the most common allergens in the first 10 years with peanut (1%) and tree-nuts (0.5%) becoming more prevalent beyond 10 years. Fruit and wheat allergy were less common at 10 years, and shellfish and kiwi emerged during adolescence. The prevalence of food allergy plus positive SPT were 1.3%, 0.8%, 0.8%, 0.9% and 2.2% at 1, 2, 4, 10 and 18 years respectively. CONCLUSION: Food allergy is highly prevalent in infancy with partial resolution during late childhood. However, a number of children acquire new food allergy during adolescence resulting in a relatively higher prevalence at 18 years.