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Research

The Molecular Immunology Unit has established research programmes in the areas of:

Molecular basis of primary immunodeficiency disorders

The primary immunodeficiency disorders arise as a result of molecular defects in genes which are essential to immune cell function. Children affected by these disorders are susceptible to frequent and unusual infections and failure to thrive. Children with the most severe of these conditions usually die by the age of two years unless they are treated by bone marrow transplantation.

The diseases which we are particularly interested in include: X-linked agammaglobulinaemia (XLA), common variable immunodeficiency (CVID), severe combined immunodeficiency (SCID), Wiskott-Aldrich syndrome (WAS) and chronic granulomatous disease (CGD). There has been rapid progress in the identification of genes responsible for many of the primary immunodeficiencies. The objective of our research is to develop a clearer understanding of roles played by the protein products of these genes in both normal and diseased immune states.

An area of active interest is in the pathogenesis of Wiskott-Aldrich syndrome. WAS is a complex disorder with a variable phenotype which can result not only in immunodeficiency and but also in many cases eczema and thrombocytopenia. The protein which is affected in this disorder, WASP, is involved in regulating the actin cytoskeleton. Despite significant recent progress, our understanding of natural WASP function and pathophysiological consequences of mutation remains limited.

We have recently demonstrated that WAS haematopoietic cells have profound defects of chemokinesis, and believe that processes related to the regulated organisation of cellular cytoarchitecture are fundamental to our understanding of the disease. The aim of our current research is to investigate the physiological functions of WASP in cells of the immune system, including macrophages and dendritic cells (DCs). Intrinsic dysfunction of the DC population may also have an important role in the pathogenesis of other primary immunodeficiency syndromes, while induced changes in DC cytoskeletal signalling pathways may contribute to the initiation of acquired immunological and inflammatory disorders.

Somatic gene therapy for primary immunodeficiencies and other bone marrow related disorders

An important benefit that has arisen from our research is the development of improved diagnostic methods for primary immunodeficiencies. This can allow for the determination of molecular defects at early stages of development, at which time clinical intervention may be optimal. Similarly, molecular techniques can be applied in a therapeutic setting to introduce functional copies of defective genes into cells that reconstitute the immune system. These are the first steps towards somatic gene therapy for primary immunodeficiencies and other bone marrow related disorders.

Our aim has been to develop the technology which will allow us to introduce a normal copy of the relevant gene into the patient's own bone marrow before transplantation into the patient. This should eliminate many of the problems associated with transplantation, including rejection and graft versus host disease. If the gene is introduced stably into the self-renewing pluripotential haematopoietic stem cells (HSCs) then theoretically this treatment need only be performed once to effect a 'cure' of the disease. Clinical trials using this novel therapy are underway. We have initiated phase I clinical trials of gene therapy for X-linked SCID, ADA-SCID and X-CGD.  

Our research continues on several fronts:

1.       Retroviral vectors are the most widely used vehicles for somatic gene therapy to date. However problems, including inefficient transduction of HSC, requires the development of improved retroviral vectors, including pseudotyped vectors. Novel vectors, containing tissue specific promoters to direct expression, and modified packaging cell lines are being developed.

2.       The use of alternate virus vectors, including lentiviral vectors, are being investigated. These vectors have the advantage of being able to integrate their genetic material into quiescent cell types, including HSCs.

Characterisation of embryonic haematopoietic stem cells

The definitive long-term repopulating haematopoietic stem cell (HSC), which seeds the adult blood system, is thought to derive from a distinct region within the embryo, the aorta-gonad-mesonephros (AGM) region which contains the dorsal aorta. In the early embryo, this region has been found to contain a cluster of cells closely associated with the ventral endothelium of the dorsal aorta. These cells express markers for early HSC and are thought to represent the primary site of definitive hematopoiesis within the embryo. The appearance of these clusters is restricted both spatially and temporally, but little is known about their origin or the developmental signals involved. We are investigating these cells, and also foetal blood and liver cells at later stages of development, and assessing their usefulness as sources of HSCs.

Modulation of the immune response using DNA vaccines and immunotherapy

Building on our work in developing efficient vectors for the stable and efficient transduction of haematopoietic cells, we have developed a number of projects which aim to modulate the immune response in a variety of conditions. For example, although bone marrow transplantation can provide an effective treatment for many diseases in some cases T cells introduced with the graft, and crucial for the protection against infection and prevention of rejection of donor marrow, can also cause significant harm to the recipient. One strategy has been developed whereby donor T cells are modified by the introduction of a "suicide gene" which allows these T cells to be selectively killed if harmful side-effects arise. Thus, beneficial effects of donor T cells are preserved but the detrimental effects are controlled. This success of this strategy will provide significant benefit for children with many different conditions undergoing bone marrow transplantation, including leukaemia and SCID. A related area of research is in investigating the quality of immune reconstitution in SCID patients who have undergone bone marrow transplantation and gene therapy protocols.

Development of integrin-mediated non-viral gene delivery system

Genetic transduction using viral vectors is limited by a number of constraints, including limits to packaging capacity and their relative inefficiency at infecting some cell types. Synthetic vectors, such as cationic liposomes, have the advantages of simplicity and safety but are largely inefficient at gene transfer. We have developed a novel synthetic vector system consisting of an electrostatic complex of an integrin-targeting peptide and plasmid DNA. Transfection efficiency can be enhanced in many cell types by incorporation of Lipofectin into the peptide/DNA transfection complexes. Transfection with integrin-targeting vectors is being optimised in a number of cell types, including cells of the respiratory and cardiovascular systems, with the aim of developing such vectors for use in clinical trials of gene therapy.

Somatic gene therapy for eye disorders

The eye is one of the most suitable target organs for gene therapy because, compared to other tissues, the eye is easily accessible and may allow localised exposure of the target tissue to therapeutic agents with reduced risk of systemic effects. Furthermore, the effects of treatment may be monitored by a variety of non-invasive examinations. Retinitis pigmentosa is the primary focus for much of our work, since many of the gene defects which can cause it are identified, and there is a lack of effective treatments. A variety of viral and non-viral vectors have been evaluated for efficiency of gene transfer to the target tissue, the photoreceptor cells, and the most promising vector system to date is based on adeno-associated virus (AAV). Our work continues in developing an effective strategy using AAV for the treatment and prevention of retinal degeneration in retinitis pigmentosa. This project is performed in collaboration with the Institute of Ophthalmology.

Self-non-self recognition by the immune system and its consequences in human health and disease

One of the projects involves experimental studies of the functions of antigen presenting cells. In particular, we are studying how different antigen presenting cells serve different roles in an immune response as well as in the induction of tolerance. One important aim of this work is to find future gene therapy strategies in autoimmune disease and bone marrow transplantation. Some aspects of this project span several disciplines and involve close collaborations between this grouping and others, including Professor Marco Londei, ICH, as well as Professors Rikard Holmdahl and Ragnar Mattsson at Lund University in Sweden.

Interactions between natural antibodies and virus

We have shown that ABO histo-blood group antigens can be transferred to virus from the host cell, and then affect the ability of natural antibodies in the next host to assist in an early and potentially more efficient immune response. We have previously worked mainly with measles, but are now working with an influenza model. The main aim of this project is to assess how such interactions between virus and natural antibodies could be utilized in improvements of viral vaccines.

Page last modified on 25 aug 10 14:09