What is in this article?:
- Researchers cracking peanut allergy mechanisms
- Database provided
• A combination treatment of heat and high pressure (autoclaving) applied to peanuts significantly reduced allergic reaction.
“The database provides other sequences that are likely to be allergenic based on the known sequence,” says Maleki.
The computer-generated binding sequences were then made into synthetic epitopes for testing purposes. “We needed to know if the computer predicted the novel binding sites correctly,” says Maleki. “So we tested those synthesized sequences using serum from people allergic to peanut and tree nuts.”
Food-allergen studies commonly involve use of blood serum from allergic individuals because their serum’s IgE recognizes allergenic epitopes. The serum, which was provided by cooperators at the University of California Davis, allowed the team to match previously unknown epitopes within the major allergenic proteins known to be common to a variety of nut and peanut allergies.
The authors found that similar immunoglobulin epitopes on allergenic proteins, as defined by SDAP, could account for some of the cross-reactivity between peanuts and tree nuts. The finding indicates that SDAP can be useful for predicting previously unidentified cross-reactive epitopes, based on their similarity to known IgE epitopes.
“The novel sequences we found and validated using the database are similar, but not identical, to the sequences we fed into the software,” says Maleki. “We were able to confirm sites that the immune system sees and binds but that we could not have predicted otherwise.”
The study was funded by the U.S. Environmental Protection Agency and the National Institutes of Health and was published in Allergy in 2011.
Previously, Maleki had assessed the diagnostic reliability of standard peanut-allergy tests. She found that while people generally eat peanuts that have been heat treated (via roasting or boiling), the extracts that are commonly used to diagnose peanut allergies are from raw peanuts.
She and colleagues hypothesized that raw peanut proteins undergo specific changes during roasting that may contribute to increases in allergenic properties.
Since then, Maleki and colleagues have published a series of studies that shed light on the molecular differences between raw and heat-treated nuts in terms of their inherent peptides that trigger human allergic reactions.
The major allergenic proteins (or allergens) of peanut are known as “Ara h 1,” “Ara h 2,” and “Ara h 3.” For one study, Maleki looked into how the peanut-roasting process alters how well an allergic individual’s immunoglobulins bind to peanut allergens.
The team compared the reaction by human IgE antibody to the heated and unheated forms of Ara h 1. The study showed that roasting-induced side reactions, such as browning, increased the amount of IgE that recognizes and binds to Ara h 1—when compared to the amount that binds to Ara h 1 from raw peanuts.
“This result partly accounts for the increased allergenic properties observed in processed, roasted peanuts,” says Maleki. The study was published in 2012 in Molecular Nutrition and Food Research.
In another study, Maleki and colleagues in Spain showed that a combination treatment of heat and high pressure (autoclaving) applied to peanuts significantly reduced allergic reaction.
Autoclaving involves a higher moisture environment, similar to steaming or boiling, than roasting. As a result, autoclaving does not initiate the browning effect that comes with roasting.
The less allergenic reaction to the combination-treated peanuts was confirmed by skin-prick tests applied to volunteers known to have peanut allergies.
“Proteins become unfolded with autoclaving,” says Maleki. “If you unfold the protein, you may reduce allergenicity.” The study was published in 2012 in Food Chemistry.