UNDERSTANDING THE T-CELL AND B-CELL RECEPTOR REPERTOIRE IN CHILDREN AND YOUNG ADULTS WITH ANTI-DRUG ANTIBODIES AGAINST PEG ASPARAGINASE

The aim of this sub study is to identify biomarkers in children and young adults with Acute Lymphoblastic Leukemia with hypersensitivity to PEG-asparaginase. Evidence strongly implicates humoral immunity in Asparaginase immunogenicity with neutralizing antibodies18. Asparaginase is a bacterial enzyme not naturally present in the human body, and therefore highly immunogenic. Upon administration, antigen-presenting cells internalize and present fragments of the enzyme to naïve T cells, driving their differentiation into T-helper cells signaling differentiation of B-cells. A subset of activated B-cells matures into long-lived plasma cells that home to the bone marrow, where they continuously secrete anti-asparaginase antibodies. Others differentiate into Memory-B-cells that enable rapid antibody responses. This immunological memory means that once sensitization occurs, re-exposure to asparaginase triggers strong hypersensitivity reactions that make further treatment unsafe. Yet, despite the clinical importance, only one study exists on TCR repertoire in response to anti-asparaginase antibodies, but no studies to date have directly profiled the B-cell receptor (BCR) repertoire in children with anti-asparaginase antibodies. The BCR sequencing has recently been developed. By integrating BCR-seq from blood and BM with serum proteomics (Ig-Seq), we can directly link specific plasma cell clones to circulating anti-asparaginase antibodies. This approach will provide mechanistic insight into drug immunogenicity and enable the identification of molecular biomarkers of hypersensitivity risk in children and young adults with ALL. Methods: The investigators will perform a longitudinal Danish cohort study in pediatric and young adult ALL patients receiving PEG-asparaginase as part of induction and post-consolidation therapy treated on the A2G-1. The investigators will include 20 patients with hypersensitivity and 20 without. Biological samples will be collected at baseline, duri