Alain Townsend

Professorial Fellow; Adviser to Clinical Medical Students and Professor of Molecular Immunology
MB BS PhD Lond, MA Oxf, FMedSci, FRCP, FRS

Most of my work has been concerned with the presentation of Influenza antigens with class I molecules of the Major Histocompatibility complex. In the past we identified the major targets for T cells as the conserved nucleoprotein and matrix protein components of the virus and demonstrated that a system of cytosolic antigen presentation exists that passes peptides derived from these proteins into the ER where they bind to class I MHC molecules. With the recent pandemic this interest continues with a practical extension into the issue of whether heterotypic immunity (between pandemic strains) can be induced in man with live attenuated strains of influenza. We have developed our own design of live attenuated virus that relies on mutations in the haemagglutinin that are permissive for infection but prevent replication of the virus. The advantage of this approach is that all of the viral proteins are expressed in their appropriate context in the lung, and thus can induce a full set of local T and B cell responses. Preliminary results show that our vaccine viruses are capable of preventing illness caused by the most virulent form of influenza in a murine infection model. We are presently investigating the mechanisms of this immunity. As part of a broader interest in human immunity to influenza we are isolating human monoclonal antibodies that neutralise the virus with a view to investigating their potential as therapeutic agents in severe influenza infections. An additional aim for this project is to build a library of neutralising antibody genes that can be used as building blocks in a molecular engineering project to form bi-specific antitibodies that can neutralise by two mechanisms at once, that may be more effective than reagents with single specificities.

In recent years our interest has extended to class I molecules that have functions other than antigen presentation. In particular the HFE gene is mutated in individuals with Hereditary Haemochromatosis, who over-absorb iron and deposit it predominantly in parenchymal tissues. Dietary iron uptake remains high in these individuals despite the iron loading. The Hfe protein is not itself an iron binding protein or an iron transporter. It is a non-classical MHC Class I protein. Hfe is expressed at a low level in the small intestinal epithelium and liver parenchyma, and strongly in liver Kupffer cells. Kupffer cells recycle iron from dying red blood cells and export iron through the action of ferroportin. Analysis of Hfe protein function has revealed two opposite activities: (1) reduction of cellular iron via blocking uptake of transferrin-bound iron by ligating the transferrin-receptor, (2) inhibition of the release of iron from cells, either directly or indirectly through the induction of Hepcidin that inhibits ferroportin. These two functions of Hfe are independent of each other. The data suggests a model in which Hfe senses the level of transferrin saturation by competition for binding to Transferrin Receptor-1. As transferrin saturation rises HFE is released and induces hepcidin. Revealing the molecular basis for this scheme is a key aim of our Lab. We have recently shown that HFE can bind to the cation-independent mannose-6 -phosphate receptor. We are presently investigating the function of this interaction in ultra-thin liver slices in vitro.