A test that uses lab-grown mast cells is showing potential as a new and non-invasive method to diagnose food allergies. The blood test has the ability to mimic an allergic reaction in a test tube, which means the patient doesn’t need to be exposed to their suspected allergen.
A new study shows the method, an advanced version of what is known as a mast cell activation (MAT) test, is highly accurate in predicting peanut allergy. Researchers developing the test say they also have proof-of-concept studies showing mast cell activation does well in predicting who will react to other foods, too.
This MAT test, developed by Swiss-based Atanis Biotech, uses mouse mast cells genetically modified to have human IgE receptors. (Mast cells are an important player in allergic reactions.)
When someone with an allergy consumes their allergen, IgE antibodies in the blood bind to the allergenic proteins. This activates mast cells, which release histamines and other inflammatory chemicals, causing symptoms such as hives, wheezing and potentially anaphylaxis.
These special mouse mast cells are “immortalized,” which means they continue to proliferate in the lab. That provides researchers with an unending supply.
The mast cell activation test analyzes the percentage of mast cells that are activated after being exposed to a sample of blood serum containing IgE antibodies and an allergenic protein.
“We can tell if someone is allergic or not,” says Dr. Alexander Eggel, PhD, a co-founder and scientific advisor of Atanis Biotech. “We’ve shown we can use the exact same cell line to test for any kind of IgE-mediated allergy. We have proof-of-concept studies that confirm that.”
First Up: Testing for Peanut Allergy
In a soon-to-be-published study in the journal Allergy, Eggel and colleagues used blood serum from 69 children and adolescents with confirmed peanut allergy, and 27 control participants without peanut allergy.
They then combined the blood serum with their lab-grown mast cells, and applied peanut allergen extract in gradually increasing amounts. Using a technique called flow cytometry, researchers analyzed mast cell activation.
The test accurately predicted which of the children and teens had peanut allergy 93 percent of the time. The test also predicted which patients did not have peanut allergy with 96 percent accuracy. (This is known as 93 percent sensitivity and 96 percent specificity).
“We have a very high accuracy in discriminating the allergics from the non-allergics,” says Eggel, an associate professor of immunology at the University of Bern in Switzerland.
For all but five of the peanut-allergic participants, mast cell activation was “dose dependent”. That means the more peanut extract was added, the more the mast cells activated. One child in the non-allergic group showed mast cell activation, indicating one false positive result.
MAT Test Vs. Current Allergy Tests
Atanis research shows their MAT test is more accurate in diagnosing peanut allergy than skin prick tests. Similarly, it’s more accurate than allergen-specific IgE blood tests for proteins, such as the Ara h 1 and Ara h 2 of peanut.
The test also doesn’t come with the risk of allergic reactions, as do oral food challenges, says Dr. Jean-Pierre Kinet, Atanis’s CEO and co-founder. During food challenges, patients eat their allergen in increasing doses over several hours. The idea is to see how much they can tolerate before starting to react.
“If we can replace the oral food challenge, it would be much safer for the patient, and much less cumbersome, and we could test multiple allergens at the same time,” Kinet says. Kinet is the former head of Molecular Allergy and Immunology at the National Institute of Allergy and Infectious Diseases (NIAID).
Kinet says the Atanis team hopes their MAT test will also be able to tell patients whether they are highly allergic or likely to have less severe symptoms.
Their research shows that some patients have more potent IgE antibodies than others. Potent IgE triggers mast cells at lower doses of allergen exposure. Potent IgE may also bind to more than one location on mast cells.
Their analysis can also detect IgG antibodies. IgG is protective against allergic reactions because IgG competes with IgE to bind with allergenic proteins and mast cells. Eventually, they hope to be able to provide this information for patients and physicians to use when deciding on treatment and allergy management.
Comparing MAT to BAT
Researchers also compared their results to another newer test, the basophil activation test (BAT). With BAT, a sample of a patient’s blood is exposed to an allergen, and then basophil response is analyzed with flow cytometry. Basophils are another type of immune system cell involved in allergic reactions.
The BAT test is currently being used to diagnose peanut, milk and egg allergies, and it’s considered highly accurate for peanut and tree nut. However, BAT has limitations.
One is that BAT uses whole blood, which needs to be analyzed within 24 hours of being drawn, in a lab that can conduct flow cytometry. This isn’t available everywhere. MAT relies on blood serum, which can be frozen and analyzed at any point.
Another BAT drawback is that in about 10 percent of tests, basophils simply don’t respond. In these patients, that can result in either false positives or negatives. Basophil response can also fluctuate in the same individuals, Kinet says. So their basophils respond at certain times and not at others.
The researchers collected BAT data on the 96 children in the study, including seven non-responders. Among them, four had confirmed peanut allergy and three were allergy free. The MAT study could distinguish the allergic from the non-allergic.
“With peanut, we have shown our test is superior to skin prick test, and superior to specific IgE,” Kinet says. “Our test is equal to BAT, but we are beating BAT because we have no non-responders and they do. And when we test the non-responders, they respond to our test.”
Making ‘Immortal’ Mast Cells
To develop their MAT, the researchers needed to grow a lot of mast cells, quickly. Prior attempts to grow human mast cells for use in diagnostic tests took two months, and generated only a limited number. “There had not been a cell line that was good enough to be used for diagnostics,” Kinet says.
To overcome this, Eggel and colleagues turned to a genetically engineered mouse model developed by Kinet, which expresses the primary human IgE receptor on its mast cells. The research team extracted mast cell progenitors from a single mouse’s bone marrow. (Progenitor cells give rise to mature mast cells.)
The researchers genetically engineered the cells both to continue to multiply indefinitely and to postpone differentiation into mature mast cells. “Because they are immortalized, you can grow them in absolutely unlimited number,” Kinet says. In the lab, the progenitors doubled in number in one day, and transformed into mature mast cells in only five days.
These breakthroughs gave Atanis a mast cell line that could support large-scale MAT testing and offer consistent results. The consistency relates to the fact that all the mast cells are from the same originator cells.
Bringing MAT Test to Market
To make the test available in U.S., Atanis needs U.S. Food and Drug Administration approval, which it’s seeking through the laboratory-developed tests (LDT) regulatory pathway. Atanis hopes to have approval for their peanut allergy test by the end of 2025.
However, the FDA is phasing in changes that may mean a lengthier review process for lab tests. This may impact approval timing for tests for additional allergens.
Atanis is also working on validating tests for cashew, alpha-gal, grass and tree pollens. Milk and egg are also in the works.
Alpha-gal, an allergy to red meat related to a Lone Star tick’s bite, feels especially urgent, Kinet says. The incidence is on the rise. Yet skin tests are unreliable, and food challenges are difficult, since alpha-gal reactions tend to occur several hours after consumption.
Eggel sees mast cell activation one day replacing skin and specific IgE blood tests for any food allergies patients want answers on.
Atanis’s test is already in use by numerous biotech companies, including IgGenix, in their clinical trials, and pharma companies studying drug desensitization. He sees MAT being used to monitor how well oral immunotherapy (OIT) desensitizes patients over time.
“With our test, we can longitudinally follow and see whether the treatment works, based on whether the activation of the mast cells gradually comes down,” he says.
Related Reading:
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