MRC Transition Support CSF Alexandra Santos

The symptoms of food allergy (FA) result from the release of certain substances by cells of the immune system, called mast cells and basophils, triggered by the interaction between allergy antibodies (called IgE) and food allergens. FA is often diagnosed using skin prick test or by detecting IgE (allergy antibodies) in the blood. However, more common than being food allergic is to have a positive allergy test to that food. For example, only 1 out of 5 children with a positive allergy test to peanut in the United Kingdom has peanut allergy. In the equivocal cases (more than 50% of patients), an oral food challenge (OFC) is required. OFC consists in giving the patient the suspected food in a controlled environment to see whether the patient develops an allergic reaction. OFC are quite expensive, time-consuming and place the patient at risk of a potentially severe reaction, but this is currently the gold-standard for the diagnosis of FA.

Funded by the MRC, I developed a new blood test called the basophil activation test (BAT) that works like an OFC in a test tube in the sense that allergen is added to cells in blood rather than food to the potentially allergic child, sparing patients from experiencing an allergic reaction. BAT to peanut showed 97% accuracy in the diagnosis of peanut allergy and reduced the need for OFC by two thirds. More recently, I have developed the BAT to cow's milk, egg, sesame and cashew nut and we are now assessing how useful BAT is to diagnose milk and egg allergies, which are the most common food allergies in childhood, and cashew and sesame allergies, which are two of the foods that most commonly require OFC as conventional allergy tests fail to diagnose allergy correctly. For this, we are inviting children with suspected food allergies to participate into the BAT 2 study, which is currently underway. Because BAT requires the use of fresh blood cells thus I developed a test similar to BAT using cells that are grown in the laboratory and thus are readily available - this is called the mast cell activation test (MAT). We have tested various samples of peanut allergic and non-allergic patients and showed that MAT confirms peanut allergy with a high degree of certainty. I anticipate that BAT and MAT will lead to a significant improvement of care for allergic patients and will reduce the costs and anxiety associated with OFC. Due to reasons beyond my control, there were some delays in the start and in recruiting to the BAT2 Study and the Transition Support would allow me to complete the study and obtain evidence to support advancing the development of these tests for clinical use.

To understand why some patients have a positive allergy test and are not allergic, we have been studying the antibodies of allergic and non-allergic children. We have shown that the IgE of allergic patients has different characteristics from the IgE of non-allergic subjects and that non-allergic subjects who have the allergy antibodies tend to have blocking antibodies to counteract the IgE. We would now like to understand why the immune system of allergic and non-allergic subjects responds differently to food allergens in the first place, and will be testing samples that have been collected from participants in the BAT 2 study. By comparing the responses of T cells (which are the coordinators of the immune system) between allergic and non-allergic patients and between allergens that are known to cause life-long allergies with allergens that cause allergies that typically resolve, we will improve our understanding of why some children are allergic and others not, may find ways to turn off the allergic response and identify new targets for a curative treatment for FA. The MRC Transition Support would enable be to gather experimental data to support a future Senior Fellowship Application to explore these mechanisms in the future.

The majority of children with food-specific IgE do not have food allergy (FA). In equivocal cases, oral food challenges (OFC) are required. However, these are expensive, time-consuming and can cause allergic reactions.
Aims:
1. To improve the diagnosis of food allergy using the basophil activation test (BAT) and the mast cell activation test (MAT);
2. To understand the molecular and cellular basis underpinning FA and tolerance in IgE-sensitised children.
Methodology:
Following the success of BAT to peanut in diagnosing food allergy (97% accuracy and 66% reduction in OFC), we have developed the BAT to milk, egg, cashew and sesame and are currently assessing the diagnostic utility of BAT to diagnose allergy to these foods in the BAT2 Study. Children with suspected allergies to these foods have been invited to participate and BAT has been performed in real-time. MAT has been done in parallel as it has the advantage of providing results for subjects with non-responding basophils and of using stored rather than fresh blood samples, which allows to test samples collected far from the lab or in the past. The performance of BAT and MAT will be compared with the gold-standard OFC.
In order to better understand why some children with food-specific IgE react to the food whereas others do not and also why some FA resolve whereas others tend to be persistent, we will be studying how different subsets of T cells respond to allergen in allergic versus non-allergic patients and in transient versus persistent food allergies. These experiments will provide the foundation for a future Senior Fellowship application.
Scientific and medical opportunities:
With the validation of the BAT and the MAT to diagnose common food allergies, we will improve the accuracy and the safety of food allergy diagnosis. By comparing the T cell response between patients and between allergens, we will identify potential targets for a definitive treatment of FA, which we currently do not have.

The proposed research aims to improve the diagnosis of food allergy (FA) by using a very accurate newly developed blood test, to validate novel biomarkers of food allergy and tolerance and to improve our understanding of the mechanism that mediate food allergy and tolerance. The ultimate goals of this project are to create an accurate safe noninvasive diagnostic test for food allergy eliminating the need for oral food challenge (OFC) and to identify key targets for future interventions to treat and prevent allergic disease.

FA affects 8% of children and 2% of adults in Western countries. FA has become a significant public health concern; an increased prevalence resulted in an increased incidence in anaphylaxis, which can be fatal. There is no curative treatment for FA and the mainstay of management remains allergen avoidance and the use of rescue treatment for accidental reactions. FA affects the quality of life of allergic children and their families due to dietary and social restrictions and to anxiety related to the life-threatening nature of FA.

The majority of patients with a positive allergy test are not allergic. In equivocal cases, which constitute about 50% of patients seen in an Allergy clinic, OFC are required to diagnose FA. However, OFC are laborious and expensive procedures that place the patient at risk of a potentially severe allergic reaction. In my previous research, the basophil activation test (BAT) proved to be very accurate (97%), with 98% sensitivity and 96% specificity, and was superior to other diagnostic tests in discriminating between peanut allergy and tolerance. BAT reduced the need for oral food challenges by two thirds. I now propose to expand the use of BAT to the diagnosis of other food allergies.

The key beneficiaries from this research include:

1. The immediate and wider science communities
(see Academic Beneficiaries)

2. The health care system and society
I anticipate that the validation of more accurate diagnostic tests (BAT and MAT) for various foods allergies will substantially improve the care for patients with suspected FA, not only by improving the diagnostic accuracy but mainly by reducing the number of OFC required. The reduction in the number of OFC will have direct and indirect economic implications for the health care system: the costs of BAT are lower than those of OFC, BAT is less time-consuming and does not require a multidisciplinary highly-trained clinical team and eliminates the anxiety and risk associated with OFC. This will improve the safety and comfort of FA diagnosis.

3. The food industry
Determination of thresholds is useful for the Public Health Authorities and for the Food Industry to establish regulatory measures to protect food allergic patients and to institute allergen control measures and labelling policies. However, this requires the performance of graded OFC in patients known to be allergic. In my previous work, BAT informed about threshold of allergic reactions to peanut. The same could be determined for other foods.

4. Patient organisations and patients
(see Pathways to Impact)

5. Key established and new industry partners who can develop new paradigms for drug testing based on our mechanistic findings
My work will also open new potential research areas for exploitation. The discovery of new mechanisms underlying FA and tolerance will have significant potential to build on existing collaborations with industry and develop new industry collaborations. The same applies to the standardisation of BAT as a diagnostic tool in FA and making this test commercially available to multiple foods. All these possibilities will be of interest to industry especially for testing new therapies based on the immunological discovery of new targets. Furthermore, the close collaboration between clinicians and scientists fostered by my project will benefit both parties and create stronger links for further collaboration and translational activity.