Reverse Epitope Discovery of Asparaginase-Specific TCRs and Their Target Epitopes 2267584

Abstract Introduction Asparaginase (ASNase) is a crucial component of pediatric acute lymphoblastic leukemia (ALL) combination chemotherapy. However, its use is complicated by hypersensitivity reactions that necessitate switching from Escherichia coli-derived ASNase to Erwinia chrysanthemi ASNase to maintain therapy. While most hypersensitivity cases can be avoided by switching formulations, a subset of patients develop allergic responses to both. The role of ASNase-specific T cell responses in the development of ASNase hypersensitivity is poorly defined, and no bona fide ASNase-specific T cell receptors (TCR) have been identified. Methods We analyzed a large bulk TCR sequencing dataset of ALL patients with and without ASNase allergy and identified single chains significantly associated with allergy. To identify paired TCRs specific for ASNase, we deployed a novel, high-throughput, paired TCR sequencing method (TIRTL-Seq) on additional ALL patient samples with allergy and compared sequence features to the allergy-associated single chains. Results This yielded a list of candidate paired TCRs, 8 of which have been stably transduced into reporter cell lines for use in peptide library screens to validate their specificity and characterize their epitope recognition. Conclusion Understanding the T cell responses in ASNase hypersensitivity will provide insight into drug induced allergic responses and lay the foundation for optimization of ASNase formulations with reduced immunogenicity. Funding Source St. Jude Graduate School of Biomedical Sciences Topic Categories Translational and Interventional Immunology (TI)