MICA Investigating CD1c lipid-antigen presentation and its role in tuberculosis

Background
I aim to research the interaction between human immune cells (T-cells) and a specific protein (CD1c) which may play a key role when fighting tuberculosis (TB) infection. The knowledge created by this research project will help to direct future, more successful treatments for TB. TB is a lung infection that spreads by people coughing. It continues to cause disease worldwide, killing over 4,000 people every day, and is becoming progressively more resistant to the antibiotics used to treat it. New approaches to control the disease are urgently needed as standard vaccination, diagnosis and treatment have remained largely unchanged for over 40 years. A human protein called CD1c binds fatty substances on the cell surface in order for human immune cells (called T-cells) to recognise them, these T cells can then protect us from infection. CD1c can also bind substances from the bacteria that causes TB and then show them to T-cells to activate them. However, many T-cells that recognise CD1c bound to bacterial components (such as TB) also seem to recognise CD1c bound to fatty substances derived from our own cells. Currently, it is not understood how these T-cells that exhibit dual recognition of our own cells and bacteria, work within the context of human tuberculosis infection.
I propose that CD1c and its T-cells regulate the interface between the TB causing bacteria and its human host and will investigate this using a range of cutting edge scientific approaches.

Aims
To fully understand CD1c and the role of responsive T-cells in human TB infection, I will proceed from understanding the fundamental process of how cells communicate through the binding of CD1c to its receptor and then move to studies in patients and infected cells. I will perform detailed studies at the molecular level to understand how CD1c binds and presents fatty lipid components to T-cell receptors through a combination of techniques including structural, mutational, computational, and cellular methods that will help to dissect the fundamental basis for binding of T-cells to CD1c. I will then investigate how CD1c responsive T-cells recognise fatty lipid components that are shared by human and bacterial cell walls. For this I will isolate T-cells from human blood and tissues, and investigate their reactivity to fatty components that are shared by human and bacterial cells. Finally, I will investigate the role of CD1c and its T-cells in human TB infection through employing a newly developed TB infection cell culture model using tiny 3 dimensional spheres within which human cells are infected with TB bacteria. This model is a closer representation of what happens in TB infected human lung. I will investigate the role of CD1c by modulating its expression and through manipulating the pathways that control the levels of fatty components that are produced in cells. I will also augment the infected spheres with CD1c-responsive T-cells in order to fully understand their functional impact in human TB infection.

Application benefits
This study will perform the first in depth investigation of the role of CD1c and its T-cells in human TB. My findings will result in new discoveries that could deliver new treatment opportunities to help tackle the TB pandemic and the basic scientific findings will also be relevant to treating cancer and inflammatory disease. This will help to keep the UK at the forefront of the research area and more importantly will help the many people affected by TB worldwide.

CD1c presents lipid antigens to the T-cell receptors (TCR) of T-cells. Although CD1c presents mycobacterial-lipids to T-cells, the majority of CD1c-restricted T-cells recognise CD1c in the absence of microbial antigens, suggesting dual recognition of self and non-self-antigens. I have shown that ligand binding induces major CD1c protein reorganisation forming new T-cell binding surfaces, whereby remodelled CD1c appears to promote T-cell recognition. My findings suggest that CD1c bound-lipids serve primarily to remodel TCR binding surfaces on CD1c, but this recognition mechanism is not well understood. My preliminary data shows that several host glycerophopholipids, which are lipids also highly expressed by Mycobacterium tuberculosis (Mtb), are CD1c ligands for T-cells. However, CD1c-restricted T-cell recognition of Mtb-derived glycerophospholipids is unknown. Importantly, neither the molecular basis of how lipidCD1c regulates TCR recognition nor the functional role of T-cells that exhibit dual recognition of self- non-self-antigen is understood in human human tuberculosis (TB). My overarching hypothesis is that T-cells which exhibit dual self- non-self-antigen recognition regulate the host-pathogen interaction in TB. The first aim of the study is to define the molecular mechanisms underpinning T-cell recognition of CD1c. I will achieve this via a cross-disciplinary approach combining molecular dynamics with structural, mutational, and functional T-cell response to understand basic recognition mechanisms. In the second aim, using my unique CD1c tetramers I will clone T-cells and their TCRs to better understand these innate T-cell subsets. CD1c-restricted T-cells are subsequently used to understand T-cell recognition of CD1c bound lipids that are shared by host and pathogen. In the final aim, I will investigate the functional impact of CD1c and its restricted T-cells in human TB using a novel bioengineered 3 dimensional TB infection model.

Impacts will be related both to the immunology and infectious disease fields and also more widely to the knowledge economy. The results will be relevant to tuberculosis (TB) patients as well as those affected by disease whereby CD1c responses are involved including cancer and autoimmune disease.
Health and social impacts
This project has the potential to save lives and decrease the long-term suffering from TB infection by providing new conceptual advances on the role of CD1c and innate T-cells. This is an area that has been relatively unexplored and this may provide new strategies to help tackle the TB pandemic (e.g. lipid vaccine, T-cell based therapy) and could provide potential new prognostic tools, or protection correlates which are in urgent need. For example, I have found that CD1c loaded lipids could either act as agonists or as antagonists (inhibitory) for T-cells (unpublished data). Therefore better understanding functional impact in human TB (beneficial or detrimental) would allow specific targeting of these T-cell responses by lipids. Consequently, this project may have a far-reaching effect, improving TB care for patients both in the UK and worldwide. TB remains an ongoing public health challenge in the UK, with the government investing £10 million in a national TB strategy in 2015. Furthermore, improved TB treatment has health and social benefits which would be most dramatically felt in Sub-Saharan Africa, which has one of the highest incidence rates of TB, and China and India that have the greatest numerical burden of disease. Ultimately, this will also benefit the UK, as the incidence of imported TB cases will fall. The realistic time scale for new therapeutics provided from this work and these benefits be realised would be more than ten years.
Economic impacts
Apart from BCG, which is only beneficial in infants, there is currently no effective TB vaccine. Furthermore, current vaccination strategies have relied heavily on eliciting conventional T-cell responses towards classical MHC-peptide antigens. However, recent outcomes for major vaccine initiatives were disappointing. Therefore, there is urgent need for new paradigms in TB research including a better understanding of the innate "unconventional" T-cell response and its functional impact in TB. The project will provide novel knowledge on the basic molecular mechanisms underpinning CD1c recognition by T-cells. Through better understanding functional impact of CD1c restricted T-cells in human TB, researchers can apply the basic knowledge to tailor these responses in future TB therapeutics. Therefore, my findings will be of interest to pharmaceutical companies, such as Immunocore who are developing T-cell based therapeutics for TB. I will work with the Southampton technology transfer office and with the enterprise team to help realise the potential outcomes of this study. More broadly, TB has a major economic impact in developing world countries, affecting the most economically productive section of the community, and better prevention or treatment would benefit all official development assistance (ODA) countries.
Training benefits
The award will develop my skill set (PI) and the staff employed. The NIRG will be a stepping-stone to develop the skills required for me to become a future leader as I transition to full independence. It will enable the me to further develop my personal and leadership skills, and I will undertake a bespoke training programme co-ordinated by the University's Leadership Development programme. New staff will be trained on a wide range of laboratory techniques, and they will be trained in approaches to understand group 1 CD1 biology, a rapidly expanding field with a relative shortage of skilled researchers. In addition, they will undertake formal training in additional skills, such as paper and grant writing techniques to equip them for an ongoing career in science - be that in academia, industry or other.