Brian Ballard, Brigham Young University
Life Sciences
Antigen presenting cells digest and display proteins from foreign and infected cells on the major histocompatibility complex (MHC) which can then be recognized by T-cells through their T cell receptor (TCR). LLO56 and LLO118 are CD4+ T cells specific for the same Listeria monocytogenes epitope but show dramatically different primary and secondary responses to infection. Because TCRs have very low affinity for MHC we would like to create a high affinity T cell. We reasoned that the single chain LLO118 TCR (Vβ2-linker-Vα2) could be subjected to directed evolution to generate mutants that are more stable and then used as a template for engineering high affinity T cell receptors. Single chain LLO118 was fused to the yeast surface protein Aga-2 and error prone PCR was used to generate mutagenic libraries. The first generation stabilized LLO118 single chain TCR (scTCR) was selected using biotinylated Vβ2 and Vα2 antibodies and anti-biotin beads and it expressed LLO118 at higher levels than wild type by flow cytometry. To produce mutants with additional stability, a second mutagenic library using the first generation mutants as templates has been produced and the most stable clones will be selected after temperature denaturation, permitting isolation of clones with increased stability for generating high affinity pathogen specific scTCRs. After engineering a high affinity T cell our research will further understanding on TCRs and the MHC and could also serve as a resource for creating a therapeutic drug.