Structure - activity relationships for novel engineered high-affinity T cell receptors

T cell receptors are related to antibodies, but they recognise short processed peptide antigens presented on the cell-surface by specialised proteins. They also have relatively low affinity. Recently, I have succeeded in engineering T cell receptors to have up to 1,000,000 times higher affinity by a process involving display by bacteriophage. These high-affinity T cell receptors have similar characteristics to monoclonal antibodies and have many potential biomedical applications in the treatment of viral infections, cancer and autoimmune diseases. High affinity is generated by several mutations in the T cell receptor sequence but it is currently very unclear exactly how high affinity is generated by these mutations. In this project, I will examine these mutations on an individual basis to build up 'structure - activity relationships' for two published high-affinity T cell receptors. This will provide an insight into how they work and could potentially enable computer prediction of high affinity for T cell receptors in the future.

High-affinity T cell receptors (TCRs) are novel soluble antibody-like proteins which can target peptide antigens presented by majorhistocompatibility complex molecules with very high specificity (Li et al. 2005 Nature Biotech 23, 349). They are selected by a process of phage display directed evolution and contain multiple mutations which confer high affinity. In this project, I will examine these mutations on an individual basis to establish how these mutations result in generating high affinity TCRs. I will clone TCRs wild-type TCRs containing high-affinity point mutations, as well as high-affinity TCRs with wild-type reversion point mutations. I will examine their binding by Biacore surface plasmon resonance and by isothermal titration calorimetry. I will determine the full range of kinetic and thermodynamic parameters for each mutation and then compile this array of data to generate rational structure-activity relationships for each of the two published high-affinity TCRs.