A new highly-sensitive method to quickly identify the proteins in foods that cause allergic reactions, even at very low concentrations, has been developed by researchers at technical university Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland.

The method, published in the journal Analytical Chemistry, was successfully tested on the blood of people who were allergic to cow milk.

Although food allergies are common, sufferers often don’t know exactly what in foods cause their allergic reactions. This knowledge could help develop customised therapies, like training the body’s immune system to respond to certain proteins found in foods. However, determining which protein in a food causes an allergic response to a patient requires time-consuming tests that often ignore rare or unexpected allergens.

Food allergies are becoming widespread in the Western world today, affecting around 6-8 per cent of children and about 3 per cent of adults. These types of allergies occur when the body’s immune system mistakes a harmless food protein for a threat and attacks it as it would normally do with a bacterium or a virus. This causes symptoms like swelling, rashes, pain, and even life-threatening anaphylactic shocks.

Cow milk allergy is common among children, preventing them from breast feeding and drinking milk, although some outgrow the allergy by six years of age. In the case of milk allergies, the antibodies are called “IgE”. Medical doctors can diagnose milk allergies by simply detecting an overproduction of IgE, but that does not tell them which one of the numerous proteins in milk – and other foods – is causing the allergic response.

Method

Researcher Hubert Girault and his team at EPFL developed a highly-sensitive method that used a patient’s IgE to determine specifically which protein induced allergic responses in them. The method uses a well-established technique called immunoaffinity capillary electrophoresis (IACE).

First, IgE antibodies from the patient’s blood are isolated by interaction with magnetic beads that are coated with a different type of antibody. The “bead” antibodies recognise and bind the patient’s IgE antibodies. This takes place inside a long and narrow glass tube, only 50 micrometers in diameter, called a “capillary”. The bound antibodies are then flushed out of the capillary and powerfully attached to the magnetic beads through a process called ‘crosslinking’, which keeps them from detaching. The beads with the patient’s IgE are then placed again inside the capillary.

The test begins when milk is injected through the capillary. As the milk’s proteins pass over the patient’s IgE antibodies, the ones that cause allergies are caught by them, while the others exit on the other side. The beads are then washed with a strong chemical that causes the allergy-inducing protein to dissociate from the patient’s IgE antibodies. The isolated, “culprit” protein is then identified using mass spectrometry, which is a technique that analyses compounds according to their mass and electrical charge.

The researchers said their method offered a personalised way to identify the exact proteins that can cause food allergies to a patient, which can help develop an effective treatment. They said the method was also quicker than other methods, as it did not require the detection and quantification of a patient’s specific IgE antibodies or the laborious and resource-intensive diagnostic methods used currently. The method also provided higher accuracy than conventional allergy-testing methods, as it can detect tiny amounts of allergic proteins, even if they were unexpected and rare, according to researchers. This also means that the method could be extended beyond milk to other foods like nuts and wheat products.

The allergic blood serum used in the work was purchased from Bioreclamation LLC (New York). Non-allergic blood serum used as a control was donated by the Regional Blood Transfusion Service of Vaud (Switzerland).

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