Allergenicity of peanut component Ara h 2: Contribution of conformational versus linear hydroxyproline-containing epitopes

Use of humanized rat basophilic leukemia reporter cell lines as a diagnostic tool for detection of allergen-specific IgE in allergic patients: time for a reappraisal?

The interaction between allergens and specific IgE is at the heart of the allergic response and as such lies at the center of techniques used for diagnosis of allergic sensitization. Although serological tests are available, in vivo tests such as double-blind placebo-controlled food challenges (DBPCFC) and skin prick test (SPT) associated to the patients' clinical history are still the main guides to clinicians in many practices around the world. More recently, complex protein arrays and basophil activation tests, requiring only small amounts of whole blood, have been developed and refined, but are yet to enter clinical practice. Similarly, the use of rat basophilic leukemia (RBL) cell lines for detection of allergen-specific IgE has been made possible by stable transfection of the human FcεRI α chain into this cell line more than 20 years ago, but has not found widespread acceptance among clinicians. Here, we review the perceived limitations of diagnostic applications of humanized RBL systems. Furthermore, we illustrate how the introduction of reporter genes into humanized RBL cells is able to overcome most of these limitations, and has the potential to become a new powerful tool to complement the armamentarium of allergists. A demonstration of the usefulness of humanized RBL reporter systems for elucidation of complex IgE sensitization patterns against wheat proteins and a section on the use of fluorescence-based reporter systems in combination with allergen arrays close the review.

Peanut protein structure, polyphenol content and immune response to peanut proteins in vivo are modulated by laccase

Laccase cross-linking of peanut protein causes changes in the protein structure, phenolic composition and immunological properties of the treated peanut protein.

Ethnic differences in peanut allergy patterns in South African children with atopic dermatitis

BACKGROUND

The prevalence of peanut allergy in South Africa is unknown, but previously thought to be low, particularly in black South Africans. This study aimed to determine the prevalence of component patterns and predictive values of screening tests in peanut allergy in South African children with atopic dermatitis (AD).

METHODOLOGY

This was a prospective, observational study in a pediatric university hospital in Cape Town. Children with AD, aged 6 months to 10 years, were recruited randomly. They were assessed for sensitization and allergy to peanut by questionnaire, skin prick tests (SPT), Immuno Solid Phase Allergen Chip test, ImmunoCAP component tests to Ara h 1, 2, 3, 8, and 9, and incremental food challenges.

RESULTS

A total of 100 participants (59 black Africans and 41 of mixed race) were enrolled, median age 42 months. There was a high and comparable rate of peanut sensitization in both black African (41%) and mixed race patients (50%), but a significantly lower prevalence of peanut allergy in the black African group (15% vs. 38%, p = 0.01). The component Ara h 2 was the most useful in differentiating allergy from tolerance in both ethnic groups, but had a significantly lower predictive value for peanut allergy in blacks (53%) vs. mixed race (93%). Overall, SPT and Ara h 2 produced the highest area under the receiver operating characteristic curve. A total of 95% positive predictive values (PPV) for SPT, peanut-specific IgE, and Ara h 2 levels varied significantly between the two ethnic groups.

CONCLUSION

The prevalence of peanut allergy is high in South African children with AD, but significantly lower in blacks compared to mixed race patients. The component Ara h 2 is useful for differentiating allergy from tolerance in both ethnic groups. Ninety-five% PPV for peanut allergy tests may need to be revised by ethnic group.

Common food allergens and their IgE-binding epitopes

Food allergy is an adverse immune response to certain kinds of food. Although any food can cause allergic reactions, chicken egg, cow's milk, wheat, shellfish, fruit, and buckwheat account for 75% of food allergies in Japan. Allergen-specific immunoglobulin E (IgE) antibodies play a pivotal role in the development of food allergy. Recent advances in molecular biological techniques have enabled the efficient analysis of food allergens. As a result, many food allergens have been identified, and their molecular structure and IgE-binding epitopes have also been identified. Studies of allergens have demonstrated that IgE antibodies specific to allergen components and/or the peptide epitopes are good indicators for the identification of patients with food allergy, prediction of clinical severity and development of tolerance. In this review, we summarize our current knowledge regarding the allergens and IgE epitopes in the well-researched allergies to chicken egg, cow's milk, wheat, shrimp, and peanut.

Patterns of IgE responses to multiple allergen components and clinical symptoms at age 11 years

BACKGROUND

The relationship between sensitization to allergens and disease is complex.

OBJECTIVE

We sought to identify patterns of response to a broad range of allergen components and investigate associations with asthma, eczema, and hay fever.

METHODS

Serum specific IgE levels to 112 allergen components were measured by using a multiplex array (Immuno Solid-phase Allergen Chip) in a population-based birth cohort. Latent variable modeling was used to identify underlying patterns of component-specific IgE responses; these patterns were then related to asthma, eczema, and hay fever.

RESULTS

Two hundred twenty-one of 461 children had IgE to 1 or more components. Seventy-one of the 112 components were recognized by 3 or more children. By using latent variable modeling, 61 allergen components clustered into 3 component groups (CG1, CG2, and CG3); protein families within each CG were exclusive to that group. CG1 comprised 27 components from 8 plant protein families. CG2 comprised 7 components of mite allergens from 3 protein families. CG3 included 27 components of plant, animal, and fungal origin from 12 protein families. Each CG included components from different biological sources with structural homology and also nonhomologous proteins arising from the same biological source. Sensitization to CG3 was most strongly associated with asthma (odds ratio [OR], 8.20; 95% CI, 3.49-19.24; P < .001) and lower FEV1 (P < .001). Sensitization to CG1 was associated with hay fever (OR, 12.79; 95% CI, 6.84-23.90; P < .001). Sensitization to CG2 was associated with both asthma (OR, 3.60; 95% CI, 2.05-6.29) and hay fever (OR, 2.52; 95% CI, 1.38-4.61).

CONCLUSIONS

Latent variable modeling with a large number of allergen components identified 3 patterns of IgE responses, each including different protein families. In 11-year-old children the pattern of response to components of multiple allergens appeared to be associated with current asthma and hay fever but not eczema.