The development and clinical applications of 111-Indium-labelled eosinophil scanning

Eosinophils are white blood cells (or corpuscles) found in large numbers in the lung airway (breathing tube) tissues of asthmatic patients. Chemicals released by activated eosinophils damage the delicate airway structures and lead to the airways becoming 'twitchy' and narrowed, causing wheezing and breathlessness. Eventually, this can lead to permanent structural damage, and the condition becomes very difficult to treat. Many of the established treatments for asthma, such as steroids, are thought to work by reducing the numbers of eosinophils getting into the airways, and by preventing their activation once they get there. However, it is difficult to study this problem and monitor the effects of these treatments directly, as taking tissue samples (biopsies) from the lung airways is unpleasant, can only look at a very small part of the lung which may not be representative of the overall disease process, and can cause major side effects. The goal of this project is to develop an eosinophil scanning technique that can be used to study the involvement of eosinophils in asthma, and other diseases that eosinophils may contribute to (for example, some forms of skin disease such as allergic dermatitis, some types of cancer such as Hodgkin's lymphoma, and some types of inflammatory bowel disease). We aim to purify eosinophils from blood samples, tag them with tiny amounts of harmless radioactivity (111indium), re-inject them back into the bloodstream, and use sensitive detectors to follow how they circulate in the body. We have already shown that this can be done safely and successfully in healthy volunteers. We wish to progress our studies by performing these same scans in patients with asthma. This will allow us to see how eosinophils behave in asthmatics, for example it will show us how long they stay in the bloodstream, whether they are more likely to become lodged in the lung and move into the airways, and how they are finally disposed of. This has never been done before in humans, and will provide new information on how these cells behave in the bloodstream and in the lung tissues in both health and disease. Once we have established these important properties of how eosinophils behave, we will study whether we can detect accumulation of eosinophils that we have deliberately caused by placing a purified extract of house dust mite (used widely and safely in clinical practise for skin allergy testing and also for placing in the airways as we intend) directly into a segment of the lung. Finally, we will test whether we can detect an effect of drugs such as steroids that are used to treat asthma on how eosinophils accumulate and behave in the lungs of asthmatic patients. If we can detect such effects, this will be very useful to monitor treatments and to monitor whether new drugs being developed to treat asthma are working.
Our group has over 20 years of experience in developing these techniques in another type of white blood cell, the neutrophil, to the point that neutrophil scanning is now used routinely in clinical practice to detect infections and to assess inflammation. Applying this expertise to the eosinophil will not only supply new data on the function and fate of these cells in healthy people and those with asthma but may also provide a simple way to quantify and view eosinophilic inflammation in humans.

Eosinophils are pathogenic in asthma, but the precise intra-pulmonary compartment relevant to eosinophilic damage is unclear, and reliable methods to quantitate and track eosinophilic inflammation and the effects of treatment thereon are lacking. We have previously developed methods involving the injection of autologous radiolabelled neutrophils to quantify the trafficking of human neutrophils in vivo in health and disease. We wish to apply these techniques to eosinophils, with the aim of delineating for the first time eosinophil kinetics, distribution and fate in human health and disease. We have already established 'gold standard' recovery and intravascular residence times for eosinophils using minimally manipulated 111In-labelled and re-injected buffy coat cells. These values will be compared to those obtained for 111In-labelled purified eosinophils to ensure that the latter behave in a physiological manner on re-injection. Using purified autologous re-injected 111In-labelled eosinophils we will determine the physiological distribution and fate of these cells by blood sampling and gamma-camera imaging. Eosinophil migration into the airways will be analysed in greater depth using double-headed gamma camera SPECT. Applying low administered activities of 111In-labelled eosinophils and whole body counting plus sequential blood and sputum analysis will allow us to quantify eosinophil loss from the airways. All of these parameters will be studied in healthy volunteers and compared with values obtained for asthmatic subjects; eosinophil recruitement in response to segmental allergen challenge will also be assessed. In 'proof of priniciple' studies, we will determine the ability of corticosteroids to modulate the recruitment of eosinophils to the lung. Ultimately, this methodology should allow clinical imaging and quantification of eosinophilic inflammation in vivo, and permit the non-invasive assessment of new and existing eosinophil-targeted therpeutic interventions.

Who Will Benefit from this Research?
We aim to develop a non-invasive method to detect, quantify and monitor fundamental aspects of eosinophil biology in health, and in particular to study the pathological aspects of eosinophilic inflammation in disease, and the potential for therapeutic interventions to modify this process. Given the burden of eosinophil-mediated disease both within the UK and globally, this research has the potential to have a substantial and wide-ranging impact with multiple potential beneficiaries.
1. Patients suffering from diseases characterised by eosinophilic inflammation such as asthma, atopic dermatitis, fungal hypersensitivity, Churg-Strauss vasculitis, Crohns disease, and radiation colitis.
2. Clinicians managing these patient groups.
3. Companies developing novel therapeutic agents to treat eosinophil-mediated disease.
4. Investigators studying the effects of therapeutic intervention in clinical trials.
5. Academics studying eosinophil function and fate.
6. Healthcare organisations and funding bodies.

How Will They Benefit from this Research?
According to WHO, asthma affects some 30 million people in Europe, with annual asthma-related costs of approximately 30 billion Euros. Whilst other eosinophil-based diseases are less prevalent, they are difficult to diagnose and the extent of disease and range of organ involvement may not be apparent; in addition, there are no good markers that accurately reflect disease activity. Hence these conditions are challenging for clinicians manage, consume disproportionate healthcare resources, and cause significant morbidity and mortality.
In asthma, we foresee a major use of 111Indium labelled eosinophils and SPECT to assess the efficacy of therapeutic interventions to reduce eosinophilic inflammation. Current methodologies including sputum and bronchial biopsies are unsatisfactory, invasive, and give a limited 'snap-shot' view that may not relate to global activity. Eosinophil scanning will enable a well-tolerated, non-invasive and dynamic assessment of eosinophilic inflammation throughout the lungs and other organs. This application will enable a sensitive and reliable endpoint in both pilot studies and in larger clinical trials. Facilitating clinical trials will lead to wider benefits to asthma sufferers and their clinicians in terms of expediting drug development and optimising management strategies. This would likewise be anticipated to improve quality of life and to reduce utilisation of health care resources.
In a subset of severe corticosteroid-dependent asthmatics who suffer recurrent exacerbations with frequent hospital admissions, clinical eosinophil scanning will offer a means to monitor disease activity and target therapies more effectively. The 10% or so of severe asthmatics have been estimated to consume 41% of health care resources required to treat asthma, so strategies that intervene successfully in this group will lead to significant economic benefit both within the UK and more widely.
In other eosinophilic conditions such as Churg-Strauss syndrome we anticipate that eosinophilic scanning may benefit individuals more directly in terms of offering a more rapid diagnosis (and hence treatment), and more accurate assessment of disease extent and activity. Again, this technique may offer significant advantages in the setting of clinical trials for these conditions.
Thus our proposed research offers future benefits to a wide range of patient groups, clinicians and those devising and assessing therapies, with the potential to reduce healthcare utilisation and hence NHS costs. We believe we can assess the potential clinical and research uses of this methodology within the 3 year time frame of the research project. The techniques should be readily adoptable by Nuclear Medicine Departments with the facility to perform 111In-granulocyte scanning across the UK and elsewhere, hence the wider benefits could be achievable with 10-15 years.