Testing the role of B cell receptor signalling in germinal centre responses

In our highly mobile society the risks from infectious diseases are increasing due to increased travel, altered global migration and reduced security in the food-chain. Vaccination is a cost-effective approach that can protect against infection. However, vaccination does not always guarantee complete protection against infection and this is especially true in the very young and the elderly. As longevity is increasing, by 2034 it is estimated that 1 in 4 of the UK population will be aged over 65, this issue will continue to be at the forefront of preventive medicine. One of the main reasons for reduced vaccination responses is that the immune system is impaired at the extremes of age. Although poorly understood one cause is poor functioning of B cells, the immune cells that produce the antibodies that help identify and remove pathogens and thus prevent infection.

Production of long lived pathogen-specific B cells is the basis of most vaccinations. When a new pathogen or vaccine enters the body B cells respond by producing antibody and importantly they are conditioned through an optimization process called "affinity maturation" to continually try to improve the quality of the antibody they make. The process is akin to evolution in that B cells undergo repeated rounds of antibody gene mutation followed by selection of the "fittest" B cells to produce antibody that will best deal with the pathogen. How affinity maturation works has been under intense scrutiny over recent years and we know that it involves B cells receiving help from other immune cell, namely T cells. What we do not understand is how the direct interaction of B cells with the pathogen or vaccine shapes this process and having this missing piece of information should allow us to develop radically different approaches to vaccinations to improve the quantity and quality of antibody produced for example in older adults.

The ultimate aim of this project is to understand how this B cell and antibody selection process is regulated to allow us to produce better vaccines. This will be achieved through collaboration with the company Medimmune who will help to produce genetically modified mice where affinity maturation is enhanced. In addition to helping develop better vaccines, these mice will become valuable tools for industry in the quest to produce new monoclonal antibody therapeutics, as the process of generating new monoclonal antibodies itself involves vaccination.

The link with Medimmune will ensure that their capacity in animal model generation is integrated with Dr Toellner's knowledge of B cell and vaccination biology, to produce a project that will lead to a step change in the field and generate resources useful to researchers and industry alike.

B cell activation leading to B cell differentiation is regulated by two major signals: Signals through B cell receptors (BCR) and signals from T helper cells. These signals regulate antibody responses during initial B cell activation after antigen entry, during the evolution to high affinity in germinal centres, and during the reactivation of a memory response. While signals from T cells are well studied, there is less information about the impact of differential BCR signals on B cell activation.
We will test the hypothesis that BCR signal strength is an important regulator of B cell differentiation. To test this, a range of mouse models with altered BCR signalling strength are developed. These involve hybrids of B cell receptors of naive B cells (IgM or IgD) and IgG1, leading to mice with hyperactive signalling in naïve B cells, and inducible mutations of kinases or phosphatases downstream of BCR signalling. These models will allow induction of differentiation stage dependent variation of BCR signalling strength in vivo, allowing us to comprehensively test the role of BCR signalling during differentiation stages in response to vaccination and B cell selection and differentiation. Importantly, all models proposed will lead to changes in BCR signalling activity when B cells enter the germinal centres. Therefore, we will be able to test whether and how BCR signalling strength within the germinal centre regulates B cell selection.
A spin-off from this project will be new mouse models that are more prone to produce high quality antibody responses to difficult targets, e.g. evolutionary conserved antigens or autoantigens. These may have commercial value in the production pipeline to new monoclonal antibody drugs, but will also be provided to the scientific community for non-commercial applications. The mice will also be useful to study the development of antibody mediated autoimmune diseases, and we started discussions with Rheumatologists at UoB about this.

Society
The importance of this work extends significantly beyond supporting academic research. By understanding how antibody responses develop we are helping to understand how to improve vaccine development. This is vital. In our highly mobile society the risks from infectious diseases are increasing due to increased travel and altered global migration and extend also into the food-chain. This is because many of our infections are actively acquired from food (e.g. Salmonella) or livestock rearing acts as an incubator and enables pathogen diversity (e.g. influenza virus). In parallel, we have a decreasing efficacy of anti-microbial treatments due to resistance and only a modest number of anti-virals available. Vaccination is a cost-effective approach that can protect against infection at the extremes of age in those groups that are most susceptible. Furthermore, vaccination is an acceptable intervention to society at large, and as the media response to the recent measles outbreak demonstrates, is one that is diminishing in controversy. Indeed, the measles outbreak demonstrates the importance of vaccination programmes to protecting society and the consequences when there is insufficient vaccine coverage. Theoretical background how vaccines work, what signals regulate the emergence of high affinity B cells and antibody producing cells, and how immunological memory cells are regulated, is still in its infancy.
Industry
This collaboration between industry and UoB will not only increase our theoretical understanding of immune responses to vaccines, which may lead to better intelligent design of vaccines. It also will produce valuable information and tools (mouse strains) for the production pipeline towards new monoclonal antibody therapeutics. Generation of monoclonal antibody drugs to new targets involves vaccination of mice as a first step of raising specific antibodies. Understanding the immunological principles of vaccination will help designing and choosing antigens reliably inducing immune responses. Further, we expect the new mouse strains produced to produce antibody responses to difficult targets, e.g. autoantigens or conserved antigens that are of superior quality, i.e. broadness of the response to different antigenic epitopes and affinity of antibodies developing.