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Listen to this siteTuesday 4 November 2003
This research project will examine whether all allergenic proteins found in peanut have a potent symptom-provoking ability or if this is limited to some proteins.
Study Duration : July 2000 to February 2003
Contractor : Southampton University
Individuals with severe peanut allergy may have mild symptoms to other allergens indicating that it is the sensitivity to peanut rather than a peculiarity of the individual's own immune system that leads to the severity of their condition. Certain foods, peanut being the most commonly described, are potent allergens and in some individuals produce severe reactions at very low doses, giving rise to persistent allergy. However, not all of those individuals with peanut allergy suffer severe symptoms and in a few cases the allergy may resolve with age. This study therefore proposes to answer the question of whether all allergenic proteins of peanut have this potent symptom-provoking ability, or if this property is limited to a few proteins and molecular motifs.
At present no diagnostic test predicts severity, although certain proteins to which people are sensitive have been identified as being as associated with severe symptoms. Concentration of food specific IgE has been shown to be useful in predicting positive food challenges and, for different foods and proteins, specific IgE diagnostic cut off levels need to be set at different concentrations.
Therefore, to further our understanding of the basis for the marked severity and persistence of peanut allergy this study aims to:
The main aim of the study was to examine whether all allergic proteins found in peanut have a potent symptom-provoking ability or if this is limited to a few proteins.
In the course of this investigation the group developed a new scoring system to examine relationships between severity of reactions to peanut in the community with severity of reaction during a double blind placebo controlled food challenge. This would determine whether any particular allergenic proteins in peanut are associated with the severity of peanut allergy. During this study skin prick testing of subjects reflected the severity score of the community reaction. The severity score of community reaction was found to predict the challenge score. In double blind placebo controlled food challenge the median cumulative threshold dose was found to be 36 milligrams of peanut protein. Asthma did not affect threshold dose or challenge score. During the first six challenges the observed reaction severity was greater than anticipated. It was hypothesised that this was due to differences in the composition of the challenge vehicle. Consequently peanut allergic subjects were then challenged twice with similar challenge vehicle recipes that only differed by lower fat content. The peanut content of the two recipes was analysed using both RAST inhibition studies and ELISA tests.
Three of four subjects reacted to much smaller doses of peanut protein on re-challenge with the lower fat recipe. RAST inhibition showed that neither recipe altered epitope recognition. The higher fat recipe required twice as much peanut to cause the same 50% inhibition. ELISA detected far lower levels of peanut in the higher fat recipe than in the lower fat recipe. The fat content of a challenge vehicle has a profound effect on the reaction experienced after allergen ingestion.
The final report is available from the FSA Library and Information centre.
To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email:
library&info@foodstandards.gsi.gov.uk
)
Presentations and abstracts:
KEC Grimshaw et al. Presentation of allergen in different food preparations affects the severity of the allergic reaction. American Academy of Allergy, Asthma and Immunology, Denver USA, Mar 2003
SA Lewis et al. Promiscuity of IgE binding to peanut allergens correlates with clinical reactivity to whole peanut during double-blind placebo controlled challenge. European Academy of Allergology and Clinical Immunology, Paris, July 2003
JO�B Hourihane et al. A comparison, using a new scoring system, of the severity of allergic reactions to peanut in the community and during double blind, placebo controlled food challenge. European Academy of Allergology and Clinical Immunology, Paris, July 2003
Contact
: For any enquiries concerning this research project, please contact the relevant Programme contact or email
food.allergy@foodstandards.gsi.gov.uk
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