T-bet as a master regulator of mucosal immunity and inflammatory bowel disease.

Inflammatory bowel disease (IBD) affects 240,000 people in the UK and costs the NHS £700 million every year. It causes disabling symptoms, impaired quality of life and serious complications including cancer, bowel blockage and bowel perforation. Many patients will be hospitalised and some will need to undergo disfiguring operations. Unfortunately, it preferentially affects young, economically active patients whom live with this difficult disease for life. IBD patients lose more working days and are more likely to be unemployed than unaffected people and its incidence appears to be increasing. At present, even the best treatment strategies fail to keep the disease in check for long periods of time. It is thought that IBD is caused by inappropriate activation of the intestinal immune system, which triggers chronic inflammation of the gut. It is now appreciated that certain immune cells play an instrumental role initiating and propagating this detrimental inflammatory process in IBD. In recent years there have been considerable advances made in our understanding of which immune cell types and which immune molecules are likely to play important roles in the disease process. It is hoped that in the coming years that insights into the regulation of gut immune cells can be harnessed to inform the development of better treatments.

This proposal aims to determine whether the immune abnormalities associated with IBD can be specifically targeted to prevent the disease. It focuses on a type of molecule known as a transcription factor, which is a very important regulator of the immune responses seen in the gut of IBD patients.

One of these molecules, (T-bet) stands out as a potentially important regulator of gut immune cells. It is abnormally expressed in IBD patients and in mice developing gut inflammation that resembles IBD. It is predicted to control many different immune mechanisms, including some of those thought to be important in IBD causation. T-bet is only found in immune cells and other bone marrow derived cells. It is therefore anticipated that modulating its action in patients is unlikely to cause unanticipated side effects in other organs of the body.

By comparing normal mice with mice lacking T-bet in certain immune cell types we will determine how this particular molecule affects immune specific mechanisms in the gut and influences IBD susceptibility. We will also try to identify novel targets for therapies that are designed to selectively suppress affect the type of cells causing IBD. This will provide insight as to whether targeting T-bet is likely to reverse inflammation in IBD, a highly desirable goal for patients with this disabling disease.

This research will be conducted at King's College London by scientists and doctors with proven track records in IBD research. In addition, close collaborations have been formed with other expert researchers at Queen Mary University of London, University College London and the University of Manchester in order to maximise expertise.

Inflammatory bowel disease (IBD) is a chronic immune mediated disease of unknown cause. Inappropriate activation of mucosal immunity directed against commensal gut bacteria is likely to be instrumental. Innate immune cells, such as dendritic cells (DCs) and innate lymphoid cells (ILCs) are crucial players mediating host-microbe interactions in the gut. We are using a combination of techniques in order to address these important questions in a multidisciplinary manner.

1. The role of T-bet in vivo: we will define the functional role of the transcription factor T-bet in DCs and ILCs in homeostatic, inflammatory interactions and infections with intestinal bacteria by interrogating constitutive and lineage-conditional knock out mouse lines (e.g. NKp46-Cre x T-betfl/fl, CD11c x T-betfl/fl) Experimental models of acute and chronic intestinal inflammation will be employed to define the functional role of T-bet in different intestinal innate immune cells in these knockout lines. We will also define the transcriptional mechanisms controlled by T-bet and GATA3 by ChIP-seq and RNA-seq technology in ILCs and DCs.

2. The role of T-bet in the ontogeny and plasticity of ILC: we will utilise a newly generated T-bet-Cre x Rosa26YFPfloxstop to fate-map ILCs in vivo. This line will be interrogated under homeostatic condition and after infectious and inflammatory stimuli.

3. The role of the host microbiota in disease: using next generation sequencing and transplant of microbiota, we will determine the bacterial species responsible for colitis and how the immune system modulate the composition of the microbiome.

The proposal provides a good fit with the MRC Infections and Immunity Board priority area of understanding the function and pathophysiology of the gastrointestinal immune system. Specifically, the proposal covers mechanistic research on mucosal biology and inflammatory bowel disease (IBD) by employing an integrative systems approach to understand the role of specific transcriptional and translational pathways in the healthy functioning of the mucosal immune system. The model systems we have developed show a close phenocopy of human IBD, with impaired colonic epithelial cell homeostasis and dysregulated immune cell function. Detailed understanding of these biological systems in this context is of fundamental importance to understanding the maintenance of a healthy mucosal immune system and how this is a mechanistic link to the development of human autoimmune disease.

Beneficiaries

Academic: the new in vivo models and sequencing datasets will be made available to the academic community and will be of use to immunologists and other specialities that are investigating mucosal biology, immune homeostasis and autoimmunity (such as investigators in cardiovascular medicine, diabetes and metabolism).

Public sector: Understanding the mechanisms that underpin the maintenance of a healthy mucosal immune system has potentially huge impacts across the NHS. If it is possible to develop a greater understanding of the pathogenesis and treatment of IBD, this would be of great importance. We are well placed to translate these findings into relevant clinical impacts as this project is taking place in the context of the NIHR Biomedical Research Centre at Guy's and St Thomas' Hospital. In this environment, we are well placed to contribute to multidisciplinary programmes in the diagnosis and therapeutics of autoimmunity. This will ensure that useful discoveries are rapidly translated for maximum patient benefit.

Industry: Manipulation of immune function has been shown to hold therapeutic promise, with candidate drugs now entering Phase III clinical trials. The potential for developing a novel therapeutic intervention to maintain healthy mucosal immunity would be of significant interest to UK industry. This work has the potential for substantial economic impact.

General public: Understanding how to measure mucosal immunity at all stages of life would benefit the general public in many ways. As a specific example of this, it may be possible to enhance the efficacy of vaccinations, which would be of significant public health impact.

Societal impact: Being able to address the issues of mucosal immunity and the more general aspects of this in relation to societal functions would enhance the awareness of the general population to this aspect of normal human pathophysiology that is generally overlooked. This could have important ramifications as to how society perceives the value of disease focussed research as it relates to their health and wellbeing.

Staff training: This grant will directly lead to the training of two staff members. Staff will gain expertise in a number of cutting-edge research areas that will expand the skills base of the UK and lead to further discoveries and technological advances as this expertise is propagated through the workforce. Staff will also gain training in skills transferable to the wider economy, including time management, communication, presentation, IT skills and university teaching.