Drug Delivery at the Immunological Synapse

We have given names to nearly all the different protein molecules that mediate communication between human cells. Now, the audacious goal of contemporary cell biology is to understand how the billion proteins in an average cell allow them to move, multiply, create a brain or defend us against viruses and bacteria. Imaging where and when proteins interact with each other has a major role to play at this frontier. Recent imaging of just a few types of proteins has already led to important new concepts in how immune cells communicate with each other and how they recognize signs of disease. Images of immune cells contacting other cells have revealed temporary membrane structures, often called immune synapses, similar to the synapses that nerve cells make with one another for communication. It has been postulated that one function for such an immune synapse is to assemble a 'gasket' that to some extent isolates the synaptic cleft from the bulk extracellular environment. However, the precise extent as to which the synapse acts as a gasket has not been studied. This fundamental knowledge can have a major importance for the design of novel drugs, because understanding to what extent and how the immune synapse is shielded from the bulk extracellular environment could, in the longer term, facilitate the rational design of drugs that penetrate the immune synapse to work more effectively, e.g. for blocking proteins secreted across the synapse. It may also be useful to note that to realize the proposed experiments we will exploit new imaging technologies which will be of broad interest across several biological research fields. Patents may be sought upon development of specific applications. In addition to the specific hypotheses to be studied here, the application of high-resolution microscopy to study immune cell interactions is also to some extent explorative and hypothesis-forming; this is still a very young field and more surprises are surely in store.

Directed secretion of soluble proteins, such as cytokines, across intercellular contacts plays a central role in establishing immune responses. A large structured interface is formed at such intercellular contacts where molecules required for adhesion and signalling accumulate to establish the immune synapse. It has been postulated that one function for such an immune synapse is to assemble a 'gasket' that to some extent isolates the synaptic cleft from the bulk extracellular environment. However, to the best of my knowledge, antibodies or other potential therapeutic agents have not been designed with a view to being able to readily penetrate and act within the context of such a gasket. Thus, I propose here to study fundamental properties of immune synapses that may impede drug/antibody delivery and apply this knowledge to the design of drugs/antibodies to act within immune synapses. I first aim to clarify the extent to which the immune synapse functions as 'gasket' and determine the underlying molecular and cellular mechanisms by which such a gasket is established. This will give important insights into the nature of the immune synapses and its importance for intercellular communication in the immune system. I then propose to assess different approaches in drug design to facilitate penetration into immune synapses, including lipid conjugation, varying drug size, and using bispecific antibodies. I propose to specifically compare the efficacy of different strategies for blocking synaptic cytokine secretion. Establishing the best approach for antibodies or other drugs to act within the context of an immune synapse can be an important consideration for the design of effective drugs for many diseases.

Cancer, viral infections and auto-immune diseases can all be associated with cytokine secretion for which blocking antibodies or other drugs could target. Moreover, many pathological conditions, e.g. sepsis, are a direct result of immune cell activation including high levels of cytokine secretion. Intravenous injection of antibodies against cytokines or cytokine receptors has been attempted across several clinical trials for numerous diseases. There has been some limited success with this approach so far but many antibody-based therapies have not worked well and one possible reason could be because cytokines are, in some circumstances, secreted specifically across intercellular immune synapses. To the best of my knowledge, antibody-based drugs or other drugs have not been specifically designed with a view to being able to readily penetrate the immune synapse. Chemokines can also be secreted into the synaptic cleft by antigen-presenting cells to co-activate T cells in an antigen-specific manner. Thus, drugs that block chemokine activities may also benefit from being able to specifically penetrate immune synapses. Thus although a specific disease will not be studied here, the fundamental research outlined here can establish an important new consideration for drug design that can have a wide range of specific applications. That is, the best approach for antibodies or other drugs to act within the context of an immune synapse may prove to be an important consideration for the design of effective drugs for many diseases and hence there could be considerable impact for the pharmaceutical industry. To realize the proposed experiments, we will also exploit novel imaging technologies, developed by us in collaboration with Laser Physics group at Imperial College, which will be of broad interest across several biological fields. Patents may be sought upon development of specific imaging applications and/or in the development of practical applications. For the researcher employed, the proposed research provides a useful and rare opportunity to provide training in protein and cellular biochemistry, bioimaging, and state-of-the-art fluorescence spectroscopic techniques. Such a combination of technical skills is highly desirable in interdisciplinary environments within both commercial and academic settings. In addition, I am involved a wide range of teaching activity at Imperial College, including teaching segments of first and second year undergraduate degrees. The proposed research activity does directly impact my teaching style and allows me to enthuse young undergraduates by discussing cutting edge research in my lectures. I also keenly engage in making my research accessible to non-specialist audiences. For example, I published a major article in this research area in Scientific American magazine (Oct 2006) which has a worldwide readership of over one million. In addition, I was interviewed for a feature article published in New Scientist magazine in Nov 2008, and was interviewed for The Guardian newspaper regarding the award of the Nobel Prize for GFP (Oct 10th, 2008). The BBC filmed an experiment performed in my laboratory for broadcast in 'The History of Transplantation', first shown on BBC FOUR, Sept 3rd 2008. In addition, I gave public lectures at the Royal Institution in 2000, 2005 and 2008. I also gave interviews for many other magazines including several in Europe. Together with Prof. P. French (Physics, Imperial College London), I presented my research at the Royal Society Summer Exhibition in 2003. In 2000, I won the Oxford University Press/Times Higher Education Supplement Science Writing Prize, and my article was published in The Times Higher Education Supplement. Finally, members of my laboratory have presented their research twice at the House of Commons and also across several secondary schools in London. Similar activities will continue throughout the duration of the current proposal.