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Allergy & Asthma Advocate: Fall 2003
The studies summarized below appeared in the April Journal of Allergy and Clinical Immunology (JACI), the peer-reviewed scientific journal of the American Academy of Allergy, Asthma and Immunology. Major advances in peanut allergy
Major breakthroughs in the prevention and treatment of severe peanut allergies may bring hope to the 1.5 million Americans suffering from the condition. The advances in research are featured in seven new studies in the July 2003 Journal of Allergy and Clinical Immunology (JACI). The JACI is the peer reviewed journal of the American Academy of Allergy, Asthma and Immunology (AAAAI). “The future looks bright as new models of treatment are emerging,” said Donald Y.M. Leung, MD, PhD, from National Jewish Medical and Research Center and Editor of the JACI. “The studies featured in the July JACI offer the latest research into the understanding of the history and underlying cause of severe peanut allergy, offering continued hope to those who suffer from the disease.” Calming common fears about peanut butter Exposure to peanut through casual contact or by breathing peanut fumes is a common fear of parents, leading to significant changes in the lifestyle of children with severe peanut allergy, particularly in school settings. A study by Steven J. Simonte, MD, and colleagues from Mt. Sinai School of Medicine shows that exposure to peanut, when it is in peanut butter, vastly reduces the potential for a severe reaction. Allergic reactions to peanut have been reported on airplanes when many packets of roasted peanuts are opened simultaneously, releasing peanut dust into the air. Measurable amounts of peanut protein have been found in the air filters of airplanes. Simonte’s study may help families distinguish between the potential dangers of peanut butter versus peanut proteins that can be released into the air from packaged peanut products. Creating a "vaccine" to treat peanut allergy The July JACI reports on an important milestone in the development of a peanut vaccine for long-lasting protection against peanut induced anaphylaxis. Xiu-Min Li, MD and colleagues from Mt. Sinai developed “genetically engineered” major allergenic peanut proteins that no longer bind Immunoglobulin E (IgE), but retain T cell proliferation. It is the binding of the protein to IgE that can trigger severe reactions in sensitized individuals. Researchers found that injecting heat killed E coli containing the engineered proteins into mice was very effective in preventing a severe reaction to peanut. The engineered proteins may be used as a "peanut vaccine" which would safely elicit a protective immune response to peanut, without the fear of an allergic response. Li’s study follows the recent findings published in March 2003 by Leung and Hugh A. Sampson, MD, FAAAAI, Mt. Sinai, that treatment with Anti-IgE therapy may represent an effective long-term approach for management of food-induced anaphylaxis. Their study showed that treatment with an anti-IgE antibody raised the average level at which patients began reacting to peanuts from about a half a peanut, to almost nine peanuts. Roasting enhances allergic properties Another new study found that roasting may play an important role in enhancing the allergenic properties of peanuts. Soheila J. Maleki, PhD, from the United States Department of Agriculture discovered that roasting causes the major peanut allergen, Ara h2 to become a stronger digestive enzyme inhibitor and more resistant to digestion. The study is the first to show that roasting alters the functional characteristics that directly influence the allergen’s allergic potential. These findings have important implications for studies of other allergens, where research has previously focused primarily on structural characteristics. This may explain why peanuts are such a potent allergen. Identifying patients with peanut allergy The gold standard for diagnosing food allergy is an oral food challenge, where the suspected food, or a neutral food, called a placebo, is fed to the patient in the hopes of establishing a cause and effect relationship between a food and an allergy symptom. However, the procedure is not only costly and time consuming, but can also put the patient at risk for a severe reaction. Kirsten Beyer, MD, and colleagues from Mt. Sinai developed a test that may prevent the need to perform blinded peanut challenges, decreasing the risk for severe reactions to the challenge itself. The quantification of peanut-IgE in the blood has been shown to be useful in the diagnosis of the disease. Patients with a high level of peanut-IgE are very likely to have a positive reaction following peanut ingestion, whereas patients with low levels may or may not react. Beyer’s study compared children allergic to peanuts with those who had low levels of peanut-IgE and didn’t react to peanuts. The study found that determining the presence of peanut-IgE in small pieces of the protein to which the IgE binds was helpful in distinguishing between these two groups. Outgrowing peanut allergy David M. Fleischer, MD, and colleagues from Johns Hopkins University School of Medicine show that patients with low peanut-IgE levels have a 50% chance of outgrowing their peanut allergy. It was previously thought that only 20% of people outgrow their peanut allergy, especially when diagnosed at an early age. Oral food challenges currently are the best way to prove that a patient has outgrown a food allergy. Fleischer performed peanut challenges on children with low-peanut IgE levels and found that 55% of the patients passed a peanut challenge. Of the children who passed the challenge, three had a history of severe, life-threatening reactions and four of the children passed the challenge after previously failing. Fleischer’s study suggests that challenging patients with low levels of peanut-IgE in their blood may be the most appropriate way to ensure a higher chance of passing an oral food challenge, avoiding the possible stress and side effects of a failed challenge. Fleischer’s study also surveyed patients who had outgrown their peanut allergy over the last 5 years to study the possibility of redeveloping of the allergy. The researchers sought to understand whether the patients had eaten peanut products since passing the oral food challenge, what types of peanut-containing foods they ate, how frequently they ate them and whether they had experienced any allergic reaction to peanuts. The results showed that the risk of recurrence of peanut allergy may be higher among those who have outgrown their allergy, but do not consume enough peanuts to maintain their tolerance level. Peanut allergy is the leading cause of fatal and near-fatal food-induced anaphylaxis in the United States. Each year, thousands of people rush to hospital emergency rooms, and approximately 50 to 100 people die after accidentally eating peanuts. Currently, the only form of treatment is to educate patients on how to avoid eating foods containing peanut and how to self-administer the rescue medication epinephrine following an accidental ingestion. However, only a small number of people carry epinephrine and even timely injection may not prevent death. The studies published in the July Journal of Allergy and Clinical Immunology (JACI) provide a continued hope to the 1.5 million Americans suffering from peanut allergy. Michael E. Ruff, MD, an Academy member, is active in AAAAI outreach efforts as a member and former Chair of the Public Education Committee. He practices allergy/immunology in Dallas, TX. |
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