Archive

Research Area: Nut Allergy

Almond allergens: molecular characterization, detection, and clinical relevance.

Costa, J., I. Mafra, I. Carrapatoso, M.B.P.P. Oliveira, 2012. Almond allergens: molecular characterization, detection, and clinical relevance. J Agr Food Chem. 60:1337−1349.

Almond (Prunus dulcis) has been widely used in all sorts of food products (bakery, pastry, snacks), mostly due to its pleasant flavor and health benefits. However, it is also classified as a potential allergenic seed known to be responsible for triggering several mild to life-threatening immune reactions in sensitized and allergic individuals. Presently, eight groups of allergenic proteins have been identified and characterized in almond, namely, PR-10 (Pru du 1), TLP (Pru du 2), prolamins (Pru du 2S albumin, Pru du 3), profilins (Pru du 4), 60sRP (Pru du 5), and cupin (Pru du 6, Pru du γ-conglutin), although only a few of them have been tested for reactivity with almond-allergic sera. To protect sensitized individuals, labeling regulations have been implemented for foods containing potential allergenic ingredients, impelling the development of adequate analytical methods. This work aims to present an updated and critical overview of the molecular characterization and clinical relevance of almond allergens, as well as review the main methodologies used to detect and quantitate food allergens with special emphasis on almond.

Peanut and tree nut consumption during pregnancy and allergic disease in children—should mothers decrease their intake? Longitudinal evidence from the Danish National Birth Cohort.

Maslova, E., C. Granstrőm, S. Hansen, S.B. Petersen, M. Strøm, W.C. Willett, S.F. Olsen, 2012.  Peanut and tree nut consumption during pregnancy and allergic disease in children—should mothers decrease their intake? Longitudinal evidence from the Danish National Birth Cohort. J Allergy Clin Immunol. 130:724-32.

Background: The relation between maternal peanut intake during pregnancy and allergic disease development in children has been controversial. Objective: We used data from the Danish National Birth Cohort to examine associations between maternal peanut and tree nut intake during pregnancy and allergic outcomes in children at 18 months and 7 years of age. Methods: We estimated maternal peanut and tree nut intake (n 5 61,908) using a validated midpregnancy food frequency questionnaire. At 18 months, we used parental report of childhood asthma diagnosis, wheeze symptoms, and recurrent wheeze (>3 episodes). We defined current asthma at 7 years as doctor-diagnosed asthma plus wheeze in the past 12 months and allergic rhinitis as a self-reported doctor’s diagnosis. We also used alternative classifications based on registry-based International Classification of Diseases, Tenth Revision, codes and drug dispensary data. We report here odds ratios (ORs) comparing intake of 1 or more times per week versus no intake. Results: We found that maternal intake of peanuts (OR, 0.79; 95% CI, 0.65-0.97) and tree nuts (OR, 0.75; 95% CI, 0.67-0.84) was inversely associated with asthma in children at 18 months of age. Compared with mothers consuming no peanuts, children whose mothers reported eating peanuts 1 or more times per week were 0.66 (95% CI, 0.44-0.98) and 0.83 (95% CI, 0.70-1.00) times as likely to have a registry-based and medication related asthma diagnosis, respectively. Higher tree nut intake was inversely associated with a medication-related asthma diagnosis (OR, 0.81; 95% CI, 0.73-0.90) and self-reported allergic rhinitis (OR, 0.80; 95% CI, 0.64-1.01). Conclusions: Our results do not suggest that women should decrease peanut and tree nut intake during pregnancy; instead, consumption of peanuts and tree nuts during pregnancy might even decrease the risk of allergic disease development in children.

Clinical thresholds to egg, hazelnut, milk and peanut: results from a single-center study using standardized challenges.

Eller, E., T.K. Hansen, C. Bindslev-Jensen, 2012. Clinical thresholds to egg, hazelnut, milk and peanut: results from a single-center study using standardized challenges. Ann Allergy Asthma Immunol 108:332–336.

Background: Large studies of individual thresholds and risk profiles for foods are sparse. Previous reports indicate that thresholds adjusted for the protein content in foods would be comparable. Objective: To establish and compare clinical threshold values for egg, hazelnut, milk and peanut, and correlating them to severity of symptoms. Methods: Seven hundred eighty-one challenges were performed in 487 patients (age range, 0.5–73.5 years). Using interval censoring survival analysis, the dose distribution of thresholds was fitted to a log-normal function. Symptom score was correlated to thresholds. Results: Based on the 405 challenges resulting in objective signs, similar distribution of thresholds for hazelnut, milk, and peanut challenges were found, whereas individuals with egg allergy were bimodally distributed with a high or a low threshold. Eliciting dose in 10% (95% confidence interval) was 42.9 (24-76.8) mg whole eggs, 133.8 (95.9–186.6) mg whole hazelnut, 106.5 (59.7–190.6) mg roasted peanut, and 2.9 (1.5–5.4) mL milk. Adults showed more severe symptoms and signs than children, and peanut caused more severe reactions than the 3 other foods. Conclusion: Thresholds for the different foods were not comparable, and eliciting dose for the 4 foods differed, even if adjusted for protein content. Increasing age but not a low threshold dose is associated with severe symptoms on challenge. Peanuts elicit more severe reactions than the other foods.

Cloning, expression and patient IgE reactivity of Recombinant Pru du 6, an 11S Globulin from almond.

Willison, L.N., P. Tripathi, G. Sharma, S.S. Teuber, S.K. Sathe, K.H. Roux, 2011. Cloning, expression and patient IgE reactivity of Recombinant Pru du 6, an 11S Globulin from almond. Int Arch Allergy Immunol. 323887 DOI: 10.1159/000323887

Background: IgE-reactive proteins have been identified in almond; however, few have been cloned and tested for specific patient IgE reactivity. Here, we clone and express prunin 1 and prunin 2, isoforms of the major almond protein prunin, an 11S globulin, and assay each for IgE reactivity. Methods: Prunin isoforms were PCR-amplified from an almond cDNA library, sequenced, cloned and expressed in Escherichia coli. Reactivity to the recombinant (r) allergens, Pru du 6.01 and Pru du 6.02, was screened by dot blot and immunoblot assays using sera from almond-allergic patients and murine monoclonal antibodies (mAbs). Sequential IgE-binding epitopes were identified by solid-phase overlapping peptide analysis. Epitope stability was assessed by assaying denatured recombinant proteins by immunoblot. Results: IgE reactivity to rPru du 6.01 and rPru du 6.02 was found in 9 of 18 (50%) and 5 of 18 patients (28%), respectively. Four patients (22%) demonstrated reactivity to both isoforms. Murine anti-almond IgG mAbs also showed greater reactivity to rPru du 6.01 than to rPru du 6.02. Both stable and labile epitopes were detected. Six IgE-binding sequential epitope-bearing peptide segments on Pru du 6.01 and 8 on Pru du 6.02 were detected using pooled almond-allergic sera. Conclusions: rPru du 6.01 is more widely recognized than rPru du 6.02 in our patient population. The identification of multiple sequential epitopes and the observation that treatment with denaturing agents had little effect on IgE-binding intensity in some patients suggests an important role for sequential epitopes on prunins.  

Effect of food matrix on amandin, almond (Prunus dulcis L.) major protein, immunorecognition and recovery.

Tiwari, R.S., M. Venkatachalam, G.M. Sharma, M. Su, K.H. Roux, S.K. Sathe, 2010. Effect of food matrix on amandin, almond (Prunus dulcis L.) major protein, immunorecognition and recovery. LWT – Food Science And Technology. 43:675-83.

Amandin, the primary storage protein in almonds, contains key polypeptides recognized by  almondallergic patients. A variety of food matrices representing diverse categories of foods were analyzed to assess the effect of food matrix on amandin recognition and recovery using rabbit polyclonal antibody based immunoassays. Food matrices from dairy, nuts, and vegetables typically resulted in over-estimation of amandin. Some foods representing legumes and cereals resulted in over-estimation while others in under-estimation of amandin. The amandin recovery range was 116–198 µg/100µg (dairy) 110–292 µg/100µg (tree nuts), 43–304 µg/100µg (legumes), 106–183 µg/100µg (most cereals- with the exception of barley, whole-wheat flour, wild rice and raisin bran whole mix). Amandin recovery from spices was typically low (2–85 µg/100µg) with a few exceptions where higher recoveries were observed (121–334 µg/100µg). Salt (black and white), tea, confectionery (sugar, cocoa, dark chocolate), and fruits (1–83µg/100µg) generally resulted in lower recoveries. Tested food matrices did not adversely affect amandin immunorecognition in Western blots. The pH and the extraction buffer type affected amandin recovery. The results suggest that food matrix effects as well as extraction conditions need to be carefully evaluated when developing immunoassays for amandin detection and quantification.

Diagnosing and managing common food allergies: A systematic review.

Schneider Chafen, J.J., S.J. Newberry, M.A. Riedl, D.M. Bravata, M. Maglione, M.J. Suttorp, V. Sundaram, N.M. Paige, A. Towfigh, B.J. Hulley, P.G. Shekelle, 2010. Diagnosing and managing common food allergies: A systematic review. JAMA. 303(18):1848-1856.

Context: There is heightened interest in food allergies but no clear consensus exists regarding the prevalence or most effective diagnostic and management approaches to food allergies. Objective: To perform a systematic review of the available evidence on the prevalence, diagnosis, management, and prevention of food allergies. Data Sources Electronic searches of PubMed, Cochrane Database of Systematic Reviews, Cochrane Database of Abstracts of Reviews of Effects, and Cochrane Central Register of Controlled Trials. Searches were limited to English-language articles indexed between January 1988 and September 2009. Study Selection: Diagnostic tests were included if they had a prospective, defined study population, used food challenge as a criterion standard, and reported sufficient data to calculate sensitivity and specificity. Systematic reviews and randomized controlled trials (RCTs) for management and prevention outcomes were also used. For foods where anaphylaxis is common, cohort studies with a sample size of more than 100 participants were included. Data Extraction: Two investigators independently reviewed all titles and abstracts to identify potentially relevant articles and resolved discrepancies by repeated review and discussion. Quality of systematic reviews and meta-analyses was assessed using the AMSTAR criteria, the quality of diagnostic studies using the QUADAS criteria most relevant to food allergy, and the quality of RCTs using the Jadad criteria. Data Synthesis: A total of 12 378 citations were identified and 72 citations were included. Food allergy affects more than 1% to 2% but less than 10% of the population. It is unclear if the prevalence of food allergies is increasing. Summary receiver operating characteristic curves comparing skin prick tests (area under the curve [AUC], 0.87; 95% confidence interval [CI], 0.81-0.93) and serum food-specific IgE (AUC, 0.84; 95% CI, 0.78-0.91) to food challenge showed no statistical superiority for either test. Elimination diets are the mainstay of therapy but have been rarely studied. Immunotherapy is promising but data are insufficient to recommend use. In high-risk infants, hydrolyzed formulas may prevent cow’s milk allergy but standardized definitions of high risk and hydrolyzed formula do not exist. Conclusion: The evidence for the prevalence and management of food allergy is greatly limited by a lack of uniformity for criteria for making a diagnosis.

 

Component-resolved in vitro diagnosis of hazelnut allergy in Europe.

Hansen, K.S., B.K. Ballmer-Weber, J. Sastre, J. Lidholm, K. Andersson, H. Oberhofer, M. Lluch-Bernal, J. Östling, L. Mattsson, F. Schocker, S. Vieths, L.K. Poulsen, 2009. Component-resolved in vitro diagnosis of hazelnut allergy in Europe. J Allergy Clin Immunol. 123:1134-41.

Background: Food allergy to hazelnut occurs both with and without concomitant pollen allergy. Objective: We sought to evaluate a panel of hazelnut allergens for diagnosis of hazelnut allergy in Spain, Switzerland, and Denmark. Methods: Fifty-two patients with a positive double-blind, placebo-controlled food challenge result with hazelnuts; 5 patients with a history of anaphylaxis; 62 patients with pollen allergy but hazelnut tolerance; and 63 nonatopic control subjects were included. Serum IgE levels to hazelnut extract, recombinant hazelnut allergens (rCor a 1.04, rCor a 2, rCor a 8, rCor a 11), and native allergens (nCor a 9, nCor a Bd8K, nCor a Bd11K) were analyzed by means of ImmunoCAP. Results: Among patients with hazelnut allergy, 91% (Switzerland/Spain, 100%; Denmark, 75%) had IgE to hazelnut extract, 75% to rCor a 1.04, 42% to rCor a 2, 28% to rCor a 8, and 2% to rCor a 11. The highest rate of sensitization to Cor a 1.04 was found in the northern regions (Switzerland/Denmark, 100%; Spain, 18%), whereas IgE to the lipid transfer protein rCor a 8 prevailed in Spain (Spain, 71%; Switzerland, 15%; Denmark, 5%). IgE to profilin rCor a 2 was equally distributed (40% to 45%). Among control subjects with pollen allergy, 61% had IgE to hazelnut extract, 69% to rCor a 1.04, 34% to rCor a 2, 10% to rCor a 8, and 6% to rCor a 11. Conclusion: Component-resolved in vitro analyses revealed substantial differences in IgE profiles of hazelnut allergic and hazelnut tolerant patients across Europe.

Structural stability of amandin, a major allergen from almond (Prunus dulcis), and its acidic and basic polypeptides.

Albillos, S.M., N. Menhart, T.-J. FU, 2009. Structural stability of amandin, a major allergen from almond (Prunus dulcis), and its acidic and basic polypeptides. J Agric Food Chem. 57:4698–4705.

Information relating to the resistance of food allergens to thermal and/or chemical denaturation is critical if a reduction in protein allergenicity is to be achieved through food-processing means. This study examined the changes in the secondary structure of an almond allergen, amandin, and its acidic and basic polypeptides as a result of thermal and chemical denaturation. Amandin (~370 kDa) was purified by cryoprecipitation followed by gel filtration chromatography and subjected to thermal (13-96 °C) and chemical (urea and dithiothreitol) treatments. Changes in the secondary structure of the protein were followed using circular dichroism spectroscopy. The secondary structure of the hexameric amandin did not undergo remarkable changes at temperatures up to 90 °C, although protein aggregation was observed. In the presence of a reducing agent, irreversible denaturation occurred with the following experimental values: Tm = 72.53 °C (transition temperature), ΔH = 87.40 kcal/mol (unfolding enthalpy), and Cp = 2.48 kcal/(mol °C) (heat capacity). The concentration of urea needed to achieve 50% denaturation was 2.59 M, and the Gibbs free energy of chemical denaturation was calculated to be ΔG = 3.82 kcal/mol. The basic and acidic polypeptides of amandin had lower thermal stabilities than the multimeric protein.

Crystal structure of Prunin-1, a major component of the almond (Prunus dulcis) allergen amandin.

Jin,T., S.M. Albillos, F. Guo, A. Howard, T.-J. Fu, M.H. Kothary, Y.-Z. Zhang, 2009. Crystal structure of Prunin-1, a major component of the almond (Prunus dulcis) allergen amandin. J Agric Food Chem.  57:8643–8651.

Seed storage proteins are accumulated during seed development and act as a reserve of nutrition for seed germination and young sprout growth. Plant seeds play an important role in human nutrition by providing a relatively inexpensive source of protein. However, many plant foods contain allergenic proteins, and the number of people suffering from food allergies has increased rapidly in recent years. The 11S globulins are the most widespread seed storage proteins, present in monocotyledonous and dicotyledonous seeds as well as in gymnosperms (conifers) and other spermatophytes. This family of proteins accounts for a number of known major food allergens. They are of interest to both the public and industry due to food safety concerns. Because of the interests in the structural basis of the allergenicity of food allergens, we sought to determine the crystal structure of Pru1, the major component of the 11S storage protein from almonds. The structure was refined to 2.4 Å, and the R/Rfree for the final refined structure is 17.2/22.9. Pru1 is a hexamer made of two trimers. Most of the back-to-back trimer-trimer association was contributed by monomer-monomer interactions. An α helix (helix 6) at the C-terminal end of the acidic domain of one of the interacting monomers lies at the cleft of the two protomers. The residues in this helix correspond to a flexible region in the peanut allergen Ara h 3 that encompasses a previously defined linear IgE epitope.

Threshold dose for peanut: Risk characterization based upon published results from challenges of peanut-allergic individuals.

Taylor, S.L., R.W.R. Crevel, D. Sheffield, J. Kabourek, J. Baumert, 2009. Threshold dose for peanut: Risk characterization based upon published results from challenges of peanut-allergic individuals. Food Chem Toxicol. 47:1198–1204.

Population thresholds for peanut are unknown. However, lowest- and no-observed adverse effect levels (LOAELs and NOAELs) are published for an unknown number of peanut-allergic individuals. Publications were screened for LOAELs and NOAELs from blinded, low-dose oral challenges. Data were obtained from 185 peanut-allergic individuals (12 publications). Data were analyzed by interval-censoring survival analysis and three probability distribution models fitted to it (Log-Normal, Log-Logistic, and Weibull) to estimate the ED10. All three models described the data well and provided ED10’s in close agreement: 17.6, 17.0, and 14.6 mg of whole peanut for the Log-Normal, Log-Logistic, and Weibull models, respectively. The 95% lower confidence intervals for the ED10’s were 9.2, 8.1, and 6.0 mg of whole peanut for the Log-Normal, Log-Logistic, and Weibull models, respectively. The modeling of individual NOAELs and LOAELs identified from three different types of published studies – diagnostic series, threshold studies, and immunotherapy trials – yielded significantly different whole peanut ED10’s of 11.9 mg for threshold studies, 18.0 mg for diagnostic series and 65.5 mg for immunotherapy trials; patient selection and other biases may have influenced the estimates. These data and risk assessment models provide the type of information that is necessary to establish regulatory thresholds for peanut.