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PubMed2002

The atopic dog as a model of peanut and tree nut food allergy.

BACKGROUND: Animal models are needed that mimic human IgE-mediated peanut and tree nut allergy. Atopic dogs have been previously used in a model of food allergy to cow's milk, beef, wheat, and soy, with the demonstration of specific IgE production and positive oral challenges similar to those seen in human subjects. OBJECTIVE: We sought to sensitize dogs to peanut, walnut, and Brazil nut and to assess whether sensitization is accompanied by clinical reactions and whether there is cross-reactivity among the different preparations. METHODS: Eleven dogs were sensitized subcutaneously by using an established protocol with 1 microg each of peanut, English walnut, or Brazil nut protein extracts in alum first at birth and then after modified live virus vaccinations at 3, 7, and 11 weeks of age. The dogs were sensitized to other allergens, including soy and either wheat or barley. Intradermal skin tests, IgE immunoblotting to nut proteins, and oral challenges were performed with ground nut preparations. RESULTS: At 6 months of age, the dogs' intradermal skin test responses were positive to the nut extracts. IgE immunoblotting to peanut, walnut, and Brazil nut showed strong recognition of proteins in the aqueous preparations. Each of the 4 peanut- and the 3 Brazil nut-sensitized dogs and 3 of the 4 walnut-sensitized dogs reacted on oral challenge with the corresponding primary immunogen at age 2 years. None of the peanut-sensitized dogs reacted clinically with walnut or Brazil nut challenges. One of the walnut-sensitized dogs had delayed (overnight) vomiting to Brazil nut. CONCLUSIONS: On the basis of measurements of the mean amount of allergen eliciting a skin test response in dogs, the hierarchy of reactivity by skin testing is similar to the clinical experience in human subjects (peanut > tree nuts > wheat > soy > barley). Cross-reactivity, which was not apparent between soy and peanut or tree nuts or between peanut and tree nuts, was slight between walnut and Brazil nut. The results give further support to the dog as a model of human food allergy.

Animals↗
PubMed2001

Natural history of peanut allergy.

Peanut allergy raises major concerns and requires diligence in families because of the possibility of severe reactions, the perceived inability to outgrow peanut allergy, and the widespread availability of peanuts in the Western diet. However, studies in the past year have shown that a subset of patients with peanut allergy can become tolerant to peanut. The patients with the milder reactions on presentation have a better chance to develop tolerance to peanuts than the patients whose first reaction is anaphylaxis. This review will focus on the mechanism of allergic sensitization to peanuts and the natural history of peanut allergy as it is currently evolving. The effects of cooking and altering peanut allergens are discussed as are potential treatment modalities.

Adult↗
PubMed2006

Current developments in peanut allergy.

PURPOSE OF REVIEW: Peanut allergy is among the most serious, life-threatening food sensitivities, and recent studies indicate increasing prevalence, particularly among children. Our objective is to highlight recent advances in the immunology and treatment of peanut allergy. RECENT FINDINGS: Peanut sensitization may be both a Th1- and Th2-driven process, and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) may play a role in regulating the response intensity. Preliminary work shows that the food matrix is important in the immune response to peanut and that purified peanut allergens may have little intrinsic stimulatory capacity. Studies characterizing peanut allergens have revealed Ara h 1 and Ara h 2 as the most potent allergens, but Ara h 3 may be more allergenic than previously thought. There appears to be a relationship between the diversity of IgE-binding patterns and the severity of clinical symptoms. Multiple novel approaches to treatment are being investigated, which include traditional Chinese medicine, various forms of modified immunotherapy and the use of adjuvants in modified immunotherapy. SUMMARY: By understanding the immunologic response to peanut and the roles of the major peanut allergens, it may be possible to predict those at risk for severe reactions, prevent peanut sensitization and effectively treat those already sensitized.

Allergens↗
PubMed2005

The prevalence of peanut sensitization and the association to pollen sensitization in a cohort of unselected adolescents--The Odense Adolescence Cohort Study on Atopic Diseases and Dermatitis (TOACS).

In the last decade an increased occurrence of peanut hypersensitivity and severe anaphylactic reactions to peanut have been reported. However, few prevalence studies have been performed in unselected populations. This study evaluated the point prevalence of peanut hypersensitivity in Danish adolescents. The point prevalence of peanut allergy confirmed by oral challenge was estimated to 0.5%. The number of adolescents sensitized to peanut by specific immunoglobulin E (IgE) (CAP FEIA) and skin prick test (SPT) were higher (5.8% resp. 3.4%). In adolescents without clinically relevant peanut sensitization most cases were sensitized to grass pollen and the IgE class for grass was higher than for peanut. A correlation between peanut and pollen (grass) sensitization is therefore plausible. Before a positive SPT or specific IgE measurement to peanut is considered clinically relevant in a patient, the case history should be evaluated together with examination for pollen sensitization.

Adolescent↗
PubMed2005

Exploratory integration of peanut genetic and physical maps and possible contributions from Arabidopsis.

Arachis hypogaea is a widely cultivated crop both as an oilseed and protein source. The genomic analysis of Arachis species hitherto has been limited to the construction of genetic maps; the most comprehensive one contains 370 loci over 2,210 cM in length. However, no attempt has been made to analyze the physical structure of the peanut genome. To investigate the practicality of physical mapping in peanut, we applied a total of 117 oligonucleotide-based probes ("overgos") derived from genetically mapped RFLP probes onto peanut BAC filters containing 182,784 peanut large-insert DNA clones in a multiplex experimental design; 91.5% of the overgos identified at least one BAC clone. In order to gain insights into the potential value of Arabidopsis genome sequence for studies in divergent species with complex genomes such as peanut, we employed 576 Arabidopsis-derived overgos selected on the basis of maximum homology to orthologous sequences in other plant taxa to screen the peanut BAC library. A total of 353 (61.3%) overgos detected at least one peanut BAC clone. This experiment represents the first steps toward the creation of a physical map in peanut and illustrates the potential value of leveraging information from distantly related species such as Arabidopsis for both practical applications such as comparative map-based cloning and shedding light on evolutionary relationships. We also evaluated the possible correlation between functional categories of Arabidopsis overgos and their success rates in hybridization to the peanut BAC library.

Arabidopsis↗
PubMed2005

Identification and characterization of phospholipase D and its association with drought susceptibilities in peanut (Arachis hypogaea).

Preharvest aflatoxin contamination has been identified by the peanut industry as a serious issue in food safety and human health because of the carcinogenic toxicity. Drought stress is the most important environmental factor exacerbating Aspergillus infection and aflatoxin contamination in peanut. The development of drought-tolerant peanut cultivars could reduce aflatoxin contamination and would represent a major advance in the peanut industry. In this study, we identified a novel PLD gene in peanut (Arachis hypogaea), encoding a putative phospholipase D (PLD, EC 3.1.4.4). The completed cDNA sequence was obtained by using the consensus-degenerated hybrid oligonucleotide primer strategy. The deduced amino acid sequence shows high identity with known PLDs, and has similar conserved domains. The PLD gene expression under drought stress has been studied using four peanut lines: Tifton 8 and A13 (both drought tolerant) and Georgia Green (moderate) and PI 196754 (drought sensitive). Northern analysis showed that PLD gene expression was induced faster by drought stress in the drought-sensitive lines than the drought tolerance lines. Southern analysis showed that cultivated peanut has multiple copies (3 to 5 copies) of the PLD gene. These results suggest that peanut PLD may be involved in drought sensitivity and tolerance responses. Peanut PLD gene expression may be useful as a tool in germplasm screening for drought tolerance.

Amino Acid Sequence↗
PubMed2001

Patient-tailored cloning of allergens by phage display: peanut (Arachis hypogaea) profilin, a food allergen derived from a rare mRNA.

A peanut cDNA phage surface display library was constructed and screened for the presence of IgE-binding proteins. We used a serum from a peanut-sensitized individual with a low specific IgE level to peanut extract and suffering from mild symptoms after peanut ingestion. A total of 10(11) cDNA clones were screened by affinity selection towards serum IgE immobilized to solid-phase supports. After five rounds of selective enrichment, sequence determination of 25 inserts derived from different clones revealed presence of a single cDNA species. The cDNA-encoded gene product, formally termed Ara h 5, shows up to 80% amino acid sequence identity to the well-known plant allergen profilin, a 14 kD protein present only in low amount in peanut extracts. Immunoblot analysis of fifty sera from individuals sensitized to peanut showed that 16% had mounted a detectable IgE response to the newly identified peanut profilin. High-level expression as non-fusion protein in BL21 (DE3) was carried under control of the inducible T7 promoter. Peanut profilin was purified by affinity chromatography on poly-(L-proline)-Sepharose and yielded 30 mg l(-1) culture of highly pure recombinant allergen. In spite of the high level of up to 80% amino acid identity to other plant profilins, inhibition experiments with recombinant profilins of peanut, cherry, pear, celery and birch revealed marked differences regarding their IgE-binding capacity.

Allergens↗
PubMed2002

Dissipation of monosodium methane arsonate (MSMA) on peanuts.

Monosodium methane arsonate (MSMA), the salt of methylarsonic acid (MAA), is a herbicide commonly used to control weeds along roadsides, in cotton, in turf, and on noncrop sites. In recent years questions have arisen regarding the source and nature of arsenic residues in raw agricultural commodities relative to misuse, inadvertent exposure, or rotational crop residues. Field experiments were conducted to determine the fate of MSMA that is applied to peanut foliage. Persistence, dissipation, recovery, and detection of MAA from leaf rinsate were characterized as well as resulting total arsenic and MAA concentrations in peanut kernels. MSMA was applied to peanut foliage at 105, 210, 315, and 420 g of active ingredient (ai)/ha. Peanut leaves were sampled before and after irrigation events over the next 7 days. Peanuts were harvested at maturity and analyzed for MAA and total arsenic. A confined rotational crop experiment was conducted to determine the potential for MAA residues in soil to be taken up by peanuts in fields rotated from cotton that was treated with MSMA. MAA was not detected in any peanut samples from the rotational crop experiment, even when peanuts were planted only 30 days after MSMA application to the soil at 2.24 kg of ai/ha. Field experiments showed that MSMA recovery from leaves with an aqueous rinse declined quickly but was not greatly affected by irrigation. However, quantifiable amounts of MAA were present 1 week after application and after two irrigation events, and MAA and total arsenic were measured in mature peanut kernels from all plots that received MSMA. MAA was not detected in untreated checks. Total arsenic was below the limit of quantification in untreated controls.

Arachis↗
PubMed2004

Identification of fruity/fermented odorants in high-temperature-cured roasted peanuts.

Gas chromatography/olfactometry on a concentrate of volatiles obtained by solvent-assisted flavor evaporation (SAFE) from roasted peanuts containing a fruity/fermented off-note was used to identify the odorants responsible for the flavor defect. Freshly dug peanuts were divided into two classes, mature and immature, using pod mesocarp color, and subjected to normal (27 degrees C) and high (40 degrees C) temperature curing. Sensory evaluation of the roasted peanuts found that immature peanuts cured at high temperature contained the fruity/fermented off-note. Mature peanuts cured at high temperature and both immature and mature peanuts cured at low temperature were free of the off-note. Peanuts with the off-flavor were found to contain fruit-like esters (ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, and ethyl 3-methylbutanoate) along with increased levels of short chain organic acids (butanoic, 3-methylbutanoic, and hexanoic). These findings were confirmed by sensory evaluation of models, where the addition of these compounds produced the fruity/fermented flavor defect in a control peanut paste. This is the first time that the odorants responsible for this off-note in roasted peanuts have been identified.

Arachis↗
PubMed1999

Indirect competitive ELISA for determination of traces of peanut (Arachis hypogaea L.) protein in complex food matrices.

An indirect competitive ELISA was developed allowing the detection of hidden peanut protein residues down to 2 ppm (micorgrams per gram) in various foods. The high-titer, peanut-specific polyclonal antiserum used recognized potentially allergenic proteins in both native and roasted peanuts. In the absence of a food matrix, extractable protein from roasted peanuts was detected at 104 +/- 13%. From various food items, peanut protein at > or =13 ppm was recovered between 84 and 126%, and at 2 ppm of peanut protein recovery was 143 +/- 6%. Intra- and interassay precision was <15%. In 5 of 17 commercial food products without declaration of peanut components, between 2 and 18 ppm of peanut protein was detected. This is the first assay based on commercially available reactants that allows the reliable determination of trace amounts of hidden peanut allergens in a variety of complex food matrices.

Animals↗
PubMed1999

[Peanut anaphylaxis: the problem of hidden allergens].

HISTORY: Three patients developed recurrent anaphylactic reactions after ingestion of different kinds of food (Asian food, chocolate products, bakery products). INVESTIGATIONS: In all three patients a severe peanut allergy was confirmed either by skin prick testing or serologically (specific IgE for peanut of CAP class 3,4 and 6 respectively). Peanut allergy in all patients explained the anaphylactic reactions due to ingestion of hidden peanut in the food. TREATMENT: Patients were told to avoid the allergen. Because accidental ingestion is frequent in peanut allergy, they were equipped with a document stating the severity of the allergy and emergency medication (antihistamines, oral steroids, adrenaline injector). CONCLUSIONS: Peanuts can be concealed in different kinds of food because they are cheap, rich in protein and are often used to change the viscosity of other foods. Especially the American and Asian cuisines use peanuts in a wide variety of recipes. Furthermore accidental ingestion can occur due to false or lacking declaration of peanuts in processed food. Patients with peanut allergy should be informed about these possibilities.

Adrenergic Agonists↗
PubMedDate not supplied

Isolation, identification, and characterization of clones encoding antigens responsible for peanut hypersensitivity.

Peanut allergy is a significant health problem because of the frequency, the potential severity, and the chronicity of the allergic sensitivity. Serum IgE from patients with documented peanut hypersensitivity reactions and a peanut cDNA expression library were used to identify clones that encode peanut allergens. One of the major peanut allergens, Ara h I, was selected from these clones using Ara h I-specific oligonucleotides and polymerase chain reaction technology. The Ara h I clone identified a 2.3-kb mRNA species on a Northern blot containing peanut poly A+RNA. DNA sequence analysis of the cloned inserts revealed that the Ara h I allergen has significant homology with the vicilin seed storage protein family found in most higher plants. The isolation of the Ara h I clones allowed the synthesis of this protein in Escherichia coli cells and subsequent recognition of this recombinant protein in immunoblot analysis using serum IgE from patients with peanut hypersensitivity. With the production of the recombinant peanut protein it will now be possible to address the pathophysiologic and immunologic mechanisms regarding peanut hypersensitivity reactions specifically and food hypersensitivity in general.

Allergens↗
PubMedDate not supplied

Anaphylaxis to peanuts: clinical correlation to skin tests.

To determine the prevalence of peanut sensitivity in a group of patients referred for routine allergy evaluation, we skin tested 365 consecutive patients with a battery of extracts that included pollens, danders, mold, dust and peanuts. These patients were seen either in private practice or in the Allergy Clinic (Rhode Island Hospital). Of these 365 patients, 248 were found to be atopic. Eight patients had a positive scratch test to peanut extract, and four of these had a positive history of peanut sensitivity. One asymptomatic patient to peanut by history reacted to open challenge with 2 oz of peanut on two occasions. We, therefore, found that 3.2% (8 of 248) of our atopic patients had a positive skin test to peanuts and of these at least 62.5% (5 of 8) had clinical sensitivity to peanuts. No nonatopic patient reacted to peanut skin testing.

Adult↗
PubMed2003

Manual sorting to eliminate aflatoxin from peanuts.

A manual sorting procedure was developed to eliminate aflatoxin contamination from peanuts. The efficiency of the sorting process in eliminating aflatoxin-contaminated kernels from lots of raw peanuts was verified. The blanching of 20 kg of peanuts at 140 degrees C for 25 min in preheated roasters facilitated the manual sorting of aflatoxin-contaminated kernels after deskinning. The manual sorting of raw materials with initially high aflatoxin contents (300 ppb) resulted in aflatoxin-free peanuts (i.e., peanuts in which no aflatoxin was detected). Verification procedures showed that the sorted sound peanuts contained no aflatoxin or contained low levels (<15 ppb) of aflatoxin. The results obtained confirmed that the sorting process was effective in separating contaminated peanuts whether or nor contamination was extensive. At the commercial level, when roasters were not preheated, the dry blanching of 50 kg of peanuts for 45 to 55 min facilitated the proper deskinning and subsequent manual sorting of aflatoxin-contaminated peanut kernels from sound kernels.

Aflatoxins↗
PubMed2004

Peanut allergen (Ara h 1) detection in foods containing chocolate.

Inadvertent exposure to peanut in foods poses health risks for peanut-allergic individuals that can be reduced by improving detection systems for allergen contaminants in food products and manufacturing processes. Detection of peanut in chocolate has been especially difficult. We report the optimization of conditions for measuring a major peanut allergen, Ara h 1, in chocolate with the use of a two-site monoclonal antibody sandwich enzyme-linked immunosorbent assay. Ara h 1 was extracted from peanut in the presence or absence of chocolate with phosphate buffer, salt, and three dried milks (goat, soy, or nonfat) (0 to 25% wt/vol) for 15 min at 60 degrees C or for 2.5 h at room temperature. The best conditions for Ara h 1 extraction in the presence of chocolate were 5% nonfat dry milk for 2.5 h at room temperature. Spiking experiments of chocolate with peanut confirmed improvement of the extraction: Ara h 1 was detected in extractions of 0.16 to 0.33% peanut in chocolate. Interestingly, the best conditions for Ara h 1 extraction were different for peanut alone than with chocolate, regarding time, temperature, and percentage of nonfat dry milk in the extraction buffer. In chocolate with peanut foods, the total Ara h 1 values were 10-fold higher than when products were extracted with phosphate buffer alone and could be up to 400-fold higher for individual foods. The dramatic improvement of Ara h 1 extraction should allow specific allergen monitoring in chocolate-containing food products and assessment of Ara h 1 exposure.

Allergens↗
PubMed2001

Tissue specific and inducible expression of resveratrol synthase gene in peanut plants.

The expression of resveratrol synthase (RS) genes is induced by biotic and abiotic factors in peanut cell cultures. However, little is known about the regulation of the RS gene expression in peanut plants. The expression of RS genes was investigated in peanut plants with a peanut RS clone, pPRS3C, which encodes two polypeptides that show about a 96% amino acid sequence identity to peanut RS2 and RS3, respectively. A low level of RS mRNA was detected in the roots of peanut plants grown aseptically in vitro. In mature peanut plants that were grown in the field, however, RS mRNAs were present at relatively high levels in both the roots and pods, but at below the detection limit in leaves. RS mRNAs were abundant in young pods and decreased dramatically in mature pods. The RS mRNA expression was induced by yeast extract and UV in leaves and roots, and also by wounding in leaves. Stress hormones, such as ethylene, jasmonic acid, and salicylic acid, induced RS mRNA accumulation in leaves. These results indicate that the RS gene expression is induced by biotic and abiotic stresses through the stress hormones in peanut plants. The induction of the RS gene expression by biotic and abiotic stresses could provide peanut plants with protection from microbial infections through resveratrol synthesis. The RS gene expression in developing pods has significant implications in terms of the role of resveratrol as a phytochemical for human health.

Acyltransferases↗
PubMedDate not supplied

Chemical inactivation of aflatoxins in peanut protein ingredients.

Aflatoxin contamination of peanuts has posed a threat to the peanut industry in utilizing peanuts as a source of a low-cost protein ingredient for food and feed. Although the best approach to containing the aflatoxin problem in peanuts is prevention, it appears that chemical inactivation of aflatoxin in contaminated raw material provides the best means to salvaging the contaminated material. Several chemical reagents have been investigated for their efficacy in destroying aflatoxins present in raw peanuts and defatted peanut meal. Using certain oxidizing agents such as NaOCl, H2O2, and benzoyl peroxide; bases such as ammonia, methylamine, and calcium hydroxide; and aldehydes such as formaldehyde, contaminated raw peanuts or defatted peanut meal have been demonstrated to yield peanut meals, protein isolates, and concentrates having trace amounts or nondetectable levels of aflatoxins. Processing conditions for inactivating aflatoxins using these chemicals were investigated. The chemical treatments had little effect on the physiochemical properties of the detoxified protein product. The advantages and disadvantages of using these chemicals for inactivation of aflatoxins are discussed.

Aflatoxins↗
PubMedDate not supplied

Variation of analytical results for peanuts in energy bars and milk chocolate.

Peanuts contain proteins that can cause severe allergic reactions in some sensitized individuals. Studies were conducted to determine the percentage of recovery by an enzyme-linked immunosorbent assay (ELISA) method in the analysis for peanuts in energy bars and milk chocolate and to determine the sampling, subsampling, and analytical variances associated with testing energy bars and milk chocolate for peanuts. Food products containing chocolate were selected because their composition makes sample preparation for subsampling difficult. Peanut-contaminated energy bars, noncontaminated energy bars, incurred milk chocolate containing known levels of peanuts, and peanut-free milk chocolate were used. A commercially available ELISA kit was used for analysis. The sampling, sample preparation, and analytical variances associated with each step of the test procedure to measure peanut protein were determined for energy bars. The sample preparation and analytical variances were determined for milk chocolate. Variances were found to be functions of peanut concentration. Sampling and subsampling variability associated with energy bars accounted for 96.6% of the total testing variability. Subsampling variability associated with powdered milk chocolate accounted for >60% of the total testing variability. The variability among peanut test results can be reduced by increasing sample size, subsample size, and number of analyses. For energy bars the effect of increasing sample size from 1 to 4 bars, subsample size from 5 to 20 g, and number of aliquots quantified from 1 to 2 on reducing the sampling, sample preparation, and analytical variance was demonstrated. For powdered milk chocolate, the effects of increasing subsample size from 5 to 20 g and number of aliquots quantified from 1 to 2 on reducing sample preparation and analytical variances were demonstrated. This study serves as a template for application to other foods, and for extrapolation to different sizes of samples and subsamples as well as numbers of analyses.

Allergens↗