Archive

Research Area: Nut Allergy

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.