Date of Award

2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

Abstract

Adoptive cell transfer of T cell receptor (TCR) gene-modified T cells targeting specific tumor antigens is currently in clinical trials for patients with advanced malignancies. Despite the clinical responses, there are still hurdles to be overcome in achieving an effective and safe therapy. One of the limitations in the success of this type of therapy is the potential for cross-reactivity and unanticipated off-target reactivity which could lead to autoimmunity. Adverse events encompassing these "off-target, off-tumor" cross-reactivities leading to autoimmunity have been seen in patients in different clinical trials. Here, we demonstrate a novel approach to improve antigen specific reactivity and to reduce off-target cross-reactivity by modifying the TCR using structure-guided mutations. This strategy combines mutations that alter the TCR to enhance antigen specificity with mutations that alter the TCR/MHC contact residues to reduce TCR binding with the MHC. Using the DMF5 TCR that targets the melanoma associated antigen MART-1, we examined HLA-A2 restricted cross-reactivity by measuring the polyfunctional T cell response by T cells transduced with strategically mutated DMF5 TCRs against a panel of MART-1 homologs. We further investigated how structure-guided mutations in the DMF5 TCR affected tumor lysis, processed antigen recognition, and 3D vs. 2D affinity. We demonstrate that while modified DMF5 TCRs can enhance on-target specificity, they can also lead to unexpected off-target cross-reactivity. Our data fully supports the notion that affinity is not always an accurate predictor of T cell function and cross reactivity. Moreover, we highlight the importance of rigorous pre-clinical testing to examine the potential for new specificities and reactivities of modified TCRs. By determining how various TCR mutations can alter functional T cell phenotypes and on-target responses, we can gain a better understanding of the biology of the TCR/pMHC (peptide-MHC) interface and thus how to maximize the efficacy and safety of TCRs to be used in gene-modified T cell in adoptive cell transfer.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

Share

COinS