Ara h2 and Peanut Allergy
Having an allergy to peanuts is characterized by serious anaphylactic reactions, which usually has a lifelong persistence. In the United States of America, tree nuts and peanuts are among some of the most common food allergens that produce an anaphylactic reaction in humans. This fact is concerning, because seemingly harmless substances like dust, gluten, milk and shellfish should not be of concern to people. If one were to also look at the difference between rates in the United States versus the rest of the world, they will notice a drastic difference in the prevalence of allergies between the two. This begs the question, why is there an alarming rate of food allergies in the United States of America? Along with that, what can everyone do to relieve the symptoms of this hypersensitivity reaction or even prevent it for the next generations to come? In order to get to the root of the problem, scientists have begun to look into these questions a bit deeper. Interestingly enough, even though the fat content is higher in peanuts, it is not the cause of the allergic responses. Most allergens from foods come from the protein component, like gluten. Specifically, food allergists and other researchers have found specific proteins within peanuts that can trigger these immune responses in peanut allergic persons.
Researchers have found that five of the thirty proteins related to clinical reactions of differing severity; Ara h 1, Ara h 2, Ara h 3, Ara h 8, and Ara h 9. Ara h is associated with the botanical name, Arachis hypogaea and the number next to the h tells you each component. As for peanut allergic individuals, they may be allergic to one or more of these proteins. Three of the peanut proteins, Ara h1, Ara h2, and Ara h3 have been most closely linked to serious peanut allergy responses. Ara h 1, 2, and 3 are storage proteins that are heat-resistant and are present in individuals with potentially severe peanut hypersensitive reactions. Out of all of the five proteins that can cause potential hypersensitivity responses, the peanut component Ara h 2 has proven to be the most important predictor of clinical allergies. This specific peanut protein was remarkably more specific than whole peanut extract, used in skin testing or in laboratory blood testing for specific peanut IgE, in the process of distinguishing a clinical peanut allergy.
Another method that can be used is molecular allergy component testing. Molecular allergy component testing has shown to undergo cross-reactivity amid allergens and detects elevation of sIgE to a certain allergen. In general, IgE binding to a specific protein component suggests there is a genuine allergy. These studies have also found that the Ara h 2 measurements are remarkably more precise in determining a true peanut allergy. Ara h 2 shares common IgE-binding epitopes with a several types of nuts, which can contribute to the high number of occurrences.
In most people, the immune system learns to accept that the food is foreign and is no real threat to the person. However, in some individuals the immune system produces a defense against the allergy called an antibody IgE (Immunoglobulin type E). This result is most likely due to the individuals genetic background. Immunoglobulin E will target one or more of the protein components in peanuts. The antibodies will circulate in the blood stream, then attach themselves to cells called PML’s or PMN’s that are responsible for allergic responses. One type of polymorphonuclear leukocyte are called mast cells which live in the skin, respiratory tract, and gastrointestinal tract. Another example of an allergy cell is called basophils, which live in the blood. Once the antibodies are attached to the surface of the immune cells, the proteins bind to them, causing a chain reaction which triggers the release of histamine (from basophils and mast cells) and other substances from the polymorphonuclear leukocytes. The released materials may cause any conjunction of itch, urticaria, wheezing, swelling, vomiting, red eyes, uterine cramps, runny nose, abdominal pain, low blood pressure, diarrhea, even death. This combination of symptoms is directly correlated to what is known as a type I hypersensitivity reaction or an immediate hypersensitivity reaction.
A researcher named Klemans, went a step further and analyzed the diagnostic value of sIgE to Ara h 2 in order to predict peanut allergy without an oral food challenge. His findings indicated that Ara h 2 testing could differentiate peanut allergy almost equally as well as a combining testing for speciﬁc IgE to peanut, skin prick testing, and patient characteristics. Along with this, it could reduce the need for food challenges by up to fifty percent. His partner, Dang, designed a study to validate the ability of Ara h 2 to predict an allergy to peanuts and to avoid the need for an oral food challenge in a population-based setting. They had also confirmed that Ara h 2 measurements were more accurate in distinguishing true peanut allergy. “Co-sensitization to Ara h 2 and Ara h 6 was associated with grievous reactions distinguishing severe allergy from mild symptoms,” the team wrote in the European Journal of Allergy and Clinical Immunology. “The sensitivity of Ara h 2 sIgE is 60% (95% CI, 50% to 70%), correctly identifying 60% of subjects with true peanut allergy compared with only 26% correctly identified by using whole peanut specific IgE,” the authors explained. “We report that when using a combined approach of plasma specific IgE testing for whole peanut followed by Ara h 2 for the diagnosis of peanut allergy, the number of OFCs required is reduced by almost two thirds.” Therefore, specific binding of the Ara h2 protein is a clear indicator of an allergy. A year later, a third study was published in the Journal of Allergy and Clinical Immunology, reached a similar conclusion. In this study they found that specific IgE to Ara h 2 alone could predict fifty percent of all peanut allergies and that incorporating this observation into allergy diagnosis could reduce the need for peanut challenges by at least fifty percent.
Allergy skin testing detects an allergen antibody on mast cells. ImmunoCAP allergy blood tests detect an antibody that is floating in the blood. Both of these allergy test types are valid, because they provide two different ways of assessing the same problem. In some instances, your allergist may need to do both types of tests to better comprehend your peanut allergy issue. In some people, the ability of these antibodies to cause symptoms becomes weakened as a protective factor; This is known as tolerance. In peanut allergic persons, the allergy tests will present a positive result, yet that person can eat peanuts without any complications. For this individual, the positive peanut allergy test reflects a “peanut sensitivity,” not a clinically relevant “peanut allergy.” On the other hand, someone with a positive skin test who has had symptoms presents both “peanut sensitivity” and clinically relevant “peanut allergy.” When we begin to investigate nurture, we can see a link to how an allergy like this may develop.
After extensive research, scientists have found that this risk was the highest in mothers who consumed peanuts two or more times per week throughout their pregnancy. The number of peanuts eaten as the mother breastfeed showed the same trend, yet it was not statistically significant to this study. As a result of this study, the group of highly allergic families and their infants having a child with high (potentially serious) peanut allergy blood test score by 15 months of age was greatest in mothers who ate peanuts more than 2 times per week throughout their pregnancy. This leads to the question of genetics and how it may have an impact.
Genetic factors most likely play a role since siblings of a peanut allergic child have a four-fold increased chance of developing an allergy to peanuts. However, genetics cannot be the sole problem. For instance, in rural areas of China peanut allergies are rare. Alternatively, in westernized regions of China, such as Hong Kong, the rate of peanut allergies is almost as high as they are in the United States. It has been suspected that this is due to the “hygiene hypothesis”. The hygiene hypothesis is a theory that suggests that westernized children’s reduced exposure to both serious infections and the environment allows their immune system to more readily develop allergic responses to foods and environmental substances. According to this theory, priming the immune system at an early age will help to fight off serious infections that may suppress the immune system’s ability to develop an allergy later in life. This theory has not yet been proven, though there are several examples of how this is believed to be true.
At this time, there are no cures for peanut allergies. Among the several available autoinjector products are the EpiPen, the Adrenaclick and Auvi-Q. The unequivocal treatment for a child experiencing a type I hypersensitivity reaction to peanut is injectable epinephrine. All deliver epinephrine intramuscularly, which takes full effect in approximately 8 minutes and reverses more than 90% of systemic reactions. Each product is available loaded with a smaller epinephrine dose for children weighing less than 30 kg. Auvi-Q has the unique ability to voice-activate and instruct the user to deliver the medicine. Delivery of epinephrine via a sublingual tablet is now being studied for the treatment of type I hypersensitivity reaction. In order to use an EpiPen one does not need a prescription in order to use it. Specifically, while one has to obtain an EpiPen from a primary care provider they do not need to have proof from someone who is experiencing an anaphylactic reaction to administer the medicine to them, unless they are an infant.
Today, researchers are also testing to see the effectiveness of immunotherapy which is theorized to lead to the desensitization of the allergen to the person over time. Recent trials have shown the benefit of oral immunotherapy and sublingual immunotherapy. In producing significant tolerance to peanuts in peanut-allergic individuals. It is not unrealistic to hope that in the near future, children with peanut allergy and their parents no longer will have to fear accidental contact or ingestion of peanuts. While molecular allergy testing may not completely eliminate the need for office oral food challenges for patients with unclear peanut allergy, for now being able to diagnose and predict peanut allergy can be as simple as Ara h 1, 2, and 3.
Education by a health care professional is vital for all parents of children with peanut allergy, so that they can learn to avoid accidental peanut exposure. Having a care giver who is trained in label reading and avoiding foods from places outside of the home, where ingredients are ambiguous, is a high priority in preventing a serious response to peanuts. There is a potential danger of hidden peanut proteins in foods commonly seen in social situations, like birthday parties, Halloween candy, and sauces. Thus, parents have to be diligent in notifying other adults of the food allergies their children are susceptible to and the degree of danger it could cause.
In conclusion, peanut allergies are an increasing problem in the United States of America. When one compares the rates of food allergens to other non-westernized countries, like Israel who feed young children Bamba, allergists can create a solution for future generations. With the use of proper education of nutrition throughout gestation and infancy, other preventative measures, and treatment plans for those at risk for an adverse reaction, the rate of serious immunologic responses can be decreased. Now that scientists have identified the specific proteins causing such cascades, hopefully solutions can be created for future generations. Further investigation of the hygiene hypothesis is necessary in figuring out what parents can do to prevent or prolong immunologic responses to all sorts of antigens. Should Americans go back to their ancestor’s way of life, in some respects, in order to create a safer environment for future generations? Or is it too late to revert back to the old ways of living?
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.Careri, M., et al. “Use of Specific Peptide Biomarkers for Quantitative Confirmation of Hidden Allergenic Peanut Proteins Ara h 2 and Ara h 3/4 for Food Control by Liquid Chromatography–Tandem Mass Spectrometry.” SpringerLink, Springer-Verlag, 27 Sept. 2007.
Keet, Corinne A, et al. “Evaluation of Ara h2 IgE Thresholds in the Diagnosis of Peanut Allergy in a Clinical Population.” The Journal of Allergy and Clinical Immunology. In Practice, U.S. National Library of Medicine, Jan. 2013, www.ncbi.nlm.nih.gov/pmc/articles/PMC4023471/.
“Peanut Allergy Diagnosis: As Simple as Ara h 1, 2, and 3.” consultant360.Com, www.consultant360.com/articles/peanut-allergy-diagnosis-simple-ara-h-1-2-and-3-0.
“So, Someone in Your Family Has Peanut Allergy!” Carolina Asthma & Allergy, 13 Aug. 2012.