Robert K. Bush

Identification of a Brazil-nut allergen in transgenic soybeans

BACKGROUND The nutritional quality of soybeans (Glycine max) is compromised by a relative deficiency of methionine in the protein fraction of the seeds. To improve the nutritional quality, methionine-rich 2S albumin from the Brazil nut (Betholletia excelsa) has been introduced into transgenic soybeans. Since the Brazil nut is a known allergenic food, we assessed the allergenicity of the 2S albumin. METHODS The ability of proteins in transgenic and non-transgenic soybeans, Brazil nuts, and purified 2S albumin to bind to IgE in serum from subjects allergic to Brazil nuts was determined by radioallergosorbent tests (4 subjects) and sodium dodecyl sulfate-polyacrylamide-gel electrophoresis (9 subjects) with immunoblotting and autoradiography. Three subjects also underwent skin-prick testing with extracts of soybean, transgenic soybean, and Brazil nut. RESULTS On radioallergosorbent testing of pooled serum from four subjects allergic to Brazil nuts, protein extracts of transgenic soybean inhibited binding of IgE to Brazil-nut proteins. On immunoblotting, serum IgE from eight of nine subjects bound to purified 2S albumin from the Brazil nut and the transgenic soybean. On skin-prick testing, three subjects had positive reactions to extracts of Brazil nut and transgenic soybean and negative reactions to soybean extract. CONCLUSIONS The 2S albumin is probably a major Brazil-nut allergen, and the transgenic soybeans analyzed in this study contain this protein. Our study show that an allergen from a food known to be allergenic can be transferred into another food by genetic engineering.

Sulfites in Foods: Uses, Analytical Methods, Residues, Fate, Exposure Assessment, Metabolism, Toxicity, and Hypersensitivity

Publisher Summary Sulfiting agents have a long history of use as food ingredients. Sulfur dioxide and several forms of inorganic sulfites, which liberate sulfur dioxide under the conditions of use, are food additives, collectively known as sulfiting agents. In addition to their use as food additives, the sulfites can also occur naturally in foods. Foods contain a variety of sulfur-containing compounds, including the sulfur amino acids, sulfates, sulfites, and sulfides. The key to the understanding of sulfite toxicity may lie in elucidation of sulfite metabolism. Several researchers have proposed that defects in sulfite metabolism among certain segments of the human population may put them at greater risk to the possible toxic effects of sulfite ingestion. If the current generally recognized as safe (GRAS) review leads to some limitation on the continued use of sulfites, it will be necessary to consider alternatives. Enzymatic browning will be inhibited by any process that destroys or inactivates the enzyme. Blanching would obviously work but is impractical for using on fresh fruits and vegetables. Despite their long history of use as food additives, much remains to be learned about sulfites, which would be helpful to the present concerns about their safety.

Fungi and allergic lower respiratory tract diseases

Asthma is a common disorder that in 2009 afflicted 8.2% of adults and children, 24.6 million persons, in the United States. In patients with moderate and severe persistent asthma, there is significantly increased morbidity, use of health care support, and health care costs. Epidemiologic studies in the United States and Europe have associated mold sensitivity, particularly to Alternaria alternata and Cladosporium herbarum, with the development, persistence, and severity of asthma. In addition, sensitivity to Aspergillus fumigatus has been associated with severe persistent asthma in adults. Allergic bronchopulmonary aspergillosis (ABPA) is caused by A fumigatus and is characterized by exacerbations of asthma, recurrent transient chest radiographic infiltrates, coughing up thick mucus plugs, peripheral and pulmonary eosinophilia, and increased total serum IgE and fungus-specific IgE levels, especially during exacerbation. The airways appear to be chronically or intermittently colonized by A fumigatus in patients with ABPA. ABPA is the most common form of allergic bronchopulmonary mycosis (ABPM); other fungi, including Candida, Penicillium, and Curvularia species, are implicated. The characteristics of ABPM include severe asthma, eosinophilia, markedly increased total IgE and specific IgE levels, bronchiectasis, and mold colonization of the airways. The term severe asthma associated with fungal sensitization (SAFS) has been coined to illustrate the high rate of fungal sensitivity in patients with persistent severe asthma and improvement with antifungal treatment. The immunopathology of ABPA, ABPM, and SAFS is incompletely understood. Genetic risks identified in patients with ABPA include HLA association and certain T(H)2-prominent and cystic fibrosis variants, but these have not been studied in patients with ABPM and SAFS. Oral corticosteroid and antifungal therapies appear to be partially successful in patients with ABPA. However, the role of antifungal and immunomodulating therapies in patients with ABPA, ABPM, and SAFS requires additional larger studies.

Ragweed Immunotherapy in Adult Asthma

BACKGROUND Although allergen immunotherapy is effective for allergic rhinitis, its role in treating asthma is unclear. METHODS We examined the efficacy of immunotherapy for asthma exacerbated by seasonal ragweed exposure. During an observation phase, adults with asthma who were sensitive to ragweed kept daily diaries and recorded peak expiratory flow rates between July and October. Those who reported seasonal asthma symptoms and medication use as well as decreased peak expiratory flow were randomly assigned to receive placebo or ragweed-extract immunotherapy in doses that increased weekly for an additional two years. RESULTS During the observation phase, the mean (+/- SE) peak expiratory flow rate measured in the morning during the three weeks representing the height of the pollination season was 454 +/- 20 liters per minute in the immunotherapy group and 444 +/- 16 liters per minute in the placebo group. Of the 77 patients who began the treatment phase, 64 completed one year of the study treatment and 53 completed two years. During the two treatment years, the mean peak expiratory flow rate was higher in the immunotherapy group (489 +/- 16 liters per minute, vs. 453 +/- 17 in the placebo group [P = 0.06] during the first year, and 480 +/- 12 liters per minute, vs. 461 +/- 13 in the placebo group [P = 0.03] during the second). Medication use was higher in the immunotherapy group than in the placebo group during observation and lower during the first treatment year (P = 0.01) but did not differ in the two groups during the second year (P = 0.7). Asthma-symptom scores were similar in the two groups (P = 0.08 in year 1 and P = 0.3 in year 2). The immunotherapy group had reduced hay-fever symptoms, skin-test sensitivity to ragweed, and sensitivity to bronchial challenges and increased IgG antibodies to ragweed as compared with the placebo group; there was no longer a seasonal increase in IgE antibodies to ragweed allergen in the immunotherapy group after two years of treatment. Reduced medication costs were counterbalanced by the costs of immunotherapy. CONCLUSIONS Although immunotherapy for adults with asthma exacerbated by seasonal ragweed exposure had positive effects on objective measures of asthma and allergy, the clinical effects were limited and many were not sustained for two years.

Laboratory animal allergy

Approximately one third of laboratory animal workers have occupational allergy to animal danders, and a third of these have symptomatic asthma. Sensitization generally occurs with the first 3 years of employment, and risk factors include atopic background, as well as job description as it relates to the intensity of exposure. A symptomatic worker can reduce allergen exposure with personal protective devices. A laboratory can further reduce exposure with generally available equipment, such as laminar flow caging, and procedures, such as frequent wet washing of vivaria and careful maintenance of ventilation systems. It is advisable to institute periodic medical screening of all laboratory animal workers with questionnaires and allergy skin testing in addition to providing them with training programs to reduce personal exposure.

Identification of Soybean Allergens by Immunoblotting with Sera from Soy-Allergic Adults

Immunoblots were used to compare the IgE-binding proteins of various soybean products using sera from 7 soybean-allergic patients. Blotting results indicate at least two distinct individualistic patterns of IgE binding to soy proteins. Serum IgE from individuals allergic to both peanuts and soybeans binds to several proteins with molecular weights ranging from 50,000 to 60,000 daltons, while IgE from individuals allergic to soybeans, but not peanuts, binds strongly to a protein(s) with a molecular weight of 20,000 daltons. The soy products tested displayed varying amounts of IgE binding with sera from sensitive patients.

Soybean oil is not allergenic to soybean-sensitive individuals

We have previously demonstrated that peanut oil is not allergenic to peanut-sensitive individuals. Seven soybean-sensitive patients were enrolled in a double-blind crossover study to determine whether ingestion of soybean oil can induce adverse reactions in such patients. All subjects had histories of systemic allergic reactions (urticaria, angioedema, wheezing, dyspnea, and/or vomiting) after soybean ingestion and had positive puncture skin tests with a 1:20 w/v glycerinated-saline whole soybean extract. Sera from six of the seven subjects were tested by RAST assay for the presence of specific IgE antibodies to soybean allergens. All patients had elevated levels of serum IgE antibodies to the crude soybean extract; binding values ranged from 2.3 to 28.1 times that of a negative control serum. Before the oral challenges, all patients demonstrated negative puncture skin tests to three commercially available soybean oils and to olive oil (control). On four separate days, patients were challenged with the individual soybean oils and olive oil in random sequence. At 30-minute intervals, under constant observation, patients ingested 2, 5, and 8 ml of one of the soybean oils or olive oil contained in 1 ml capsules. No untoward reactions were observed with either the commercially available soybean oils or olive oil. Soybean oil ingestion does not appear to pose a risk to soybean-sensitive individuals.

Prevalence of sensitivity to sulfiting agents in asthmatic patients

Ingestion of sulfiting agents can induce wheezing in some asthmatic patients. However, neither the prevalence of sulfite sensitivity nor the clinical characteristics of the affected asthmatic population are known. In a prospective single-blind screening study, 120 non-steroid-dependent and 83 steroid-dependent asthmatic patients underwent challenge with oral capsules of potassium metabisulfite. Five non-steroid-dependent and 16 steroid-dependent asthmatic patients experienced a greater than 20 percent reduction in their one-second forced expiratory volume within 30 minutes following the oral challenge. Twelve of these sulfite reactors were rechallenged with metabisulfite capsules in a double-blind protocol. Under these conditions, only three of seven steroid-dependent patients had a positive response. Moreover, only one of five non-steroid-dependent patients had a response to double-blind challenge. On the basis of this challenge study, the best estimate of the prevalence of sulfite sensitivity in the asthmatic patients studied is 3.9 percent. This population, however, contained a larger number of steroid-dependent asthmatic patients than would be found in the general asthmatic population. It is concluded, therefore, that the prevalence of sulfite sensitivity in the asthmatic population as a whole would be less than 3.9 percent and that steroid-dependent asthmatic patients are most at risk.

A critical evaluation of clinical trials in reactions to sulfites

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Sublingual immunotherapy in patients with allergic rhinoconjunctivitis caused by ragweed pollen

BACKGROUND Specific allergen immunotherapy is most often delivered subcutaneously, but sublingual immunotherapy may confer greater benefit in terms of tolerability and safety, accessibility, and improved antigen delivery. OBJECTIVE This randomized, double-blind, placebo-controlled trial was conducted to identify a safe and effective maintenance dose range of sublingual standardized glycerinated short ragweed pollen extract in adults with ragweed-induced rhinoconjunctivitis. METHODS In May 2006, a total of 115 patients with ragweed-induced rhinoconjunctivitis were randomly allocated to placebo (n = 40), medium-dose extract (4.8 microg Amb a 1/d; n = 39), or high-dose extract (48 microg Amb a 1/d; n = 36). In a 1-day (rush) dose-escalation regimen, ragweed pollen extract was administered sublingually in incremental doses until maximum tolerable or scheduled dose was reached and then maintained during the ragweed pollen season. Patient diaries were used to monitor nasal and ocular symptoms and medication. The primary endpoint was symptom score. RESULTS Both active treatment groups achieved a 15% reduction in total rhinoconjunctivitis symptom scores compared with placebo during the entire ragweed pollen season, but the difference was not statistically significant (P > .10) However, in an analysis of covariance correcting for preseasonal symptoms, both mean daily symptom scores (0.19 +/- 1.16 vs 1.00 +/- 2.30) and medication scores (0.0003 +/- 1.64 vs 0.63 +/- 1.06) for the entire pollen season were significantly reduced in the high-dose versus placebo groups, respectively (P <or= .05). Ragweed-specific IgG, IgG(4), and IgA antibodies were increased after treatment in the medium- and high-dose groups and not the placebo group. Frequency of adverse events was similar between the placebo and treatment groups, but oral-mucosal adverse events occurred more often with treatment. CONCLUSION Standardized glycerinated short ragweed pollen extract administered sublingually at maintenance doses of 4.8 to 48 microg Amb a 1/d was safe and can induce favorable clinical and immunologic changes in ragweed-sensitive subjects. However, additional trials are needed to establish efficacy.