1. Detecting Allergens in Foods
Miriam Rittenberg

2. What are allergies?
-one way your body detects foreign substances is with different antibodies that bind to proteins from those materials (antigens), and then trigger an immune response
-several antibodies in the body but the one involved in allergic reactions is IgE (short for Immunoglobulin E)
-it mostly helps the body fight parasitic worms
-not much IgE is floating around by itself, it is mostly bound to mast cells
-in some people IgE will attach to harmless proteins (allergens)
-allergies are partially genetic but what causes someone to have an allergy is still poorly understood
-allergies vary from person to person

3. Allergic Reaction
-allergen attaches to IgE on mast cells
-the mast cells release a lot of chemicals including histamine
-these increase permeability of blood vessels
-this is supposed to let white blood cells travel in and out of blood vessels
-but it also lowers blood pressure which can be dangerous

4. Why is a detector useful?
-no cure for allergies so people with them need to avoid foods with allergens they are sensitive to
-usually this can be done by looking at the list of ingredients
-but sometimes foods can be mislabeled, or an ingredients list might not be available
-so it would be helpful to have a portable and easy to use way to check foods for ingredients that might contain allergens
-an iGem team decided to make one for peanuts
-peanuts are not the most common food allergy but they are the one that causes the most cases of anaphylaxis

5. What the iGem team’s detector is checking for
-not everybody with an allergy reacts to the same allergen
-but if a food has one peanut allergen it probably has the others too
-so checking for one is enough
-this detector checks for the protein Ara h1 (called this because another name for peanuts is Arachis hypogaea)
-other allergens in peanuts are called Ara h2, Ara h3, etc.

6. Parts of the detector:
-an epitope from Ara h1
-an epitope is the specific part of an antigen that the antibody will bind to
-a fluorescent protein bound to the epitope
-this is red fluorescent protein (RFP)
-an antibody that targets Ara h1
-this will be a kind of IgE but different variants of IgE bind to different proteins
-a different fluorescent protein bound to the antibody
-this is fluorescein isothiocyanate (FITC)
-an electrical system that can excite the FITC and measure the wavelength of the light emitted by the detector

7. -the FITC will transfer energy to the RFP
How the detector works
-if there is no Ara h1 for the antibody to bind to, the antibody will bind to the synthetic epitope
-this will bring the two fluorescent proteins close enough to interact with each other
-the FITC will transfer energy to the RFP
-this causes the RFP to emit a different wavelength of light
-the detector will detect this wavelength and turn on a green light indicating that there are no peanuts in the detector
No Ara h 1
 Antibody
Epitope
RFP
FITC
Higher wavelength
Energy

8. -the antibody will bind to the Ara h1
What if there is Ara h1?
-the antibody will bind to the Ara h1
-the FITC and the RFP will stay far apart
-the RFP emits the wavelength of light that it does by itself
-the detector notices the change and turns on a red light
-there are peanuts in the detector
Ara h 1 is present
Antibody
Ara h 1
Epitope
FITC
RFP
Lower wavelength

9. Conclusion
-similar devices could be created for other allergens
-one thing to worry about is that this tests for one molecule to decide whether any of many molecules are present
-if a food had no Ara h1, but did have other peanut allergens, someone could have a reaction to the food even though this detector stayed green
-unlikely to be a problem in this case because peanuts always have Ara h1, but it is something to keep in mind

10. Sources
(this is the source of the diagram in slide 3)