IMMU-33. Profiling the peripheral immune response following neurosurgical resection of glioblastoma

Abstract This project addresses the potential release of tumor antigens into the periphery during neurosurgical resection of glioblastoma by examining if there is an increase in the number of antigen-specific T cells following surgery. Patients are consented and enrolled in the study before surgery and peripheral blood mononuclear cells (PBMC) are isolated before surgery and again 2, 4, and 12 weeks following surgery. An autologous tissue lysate is created from bulk tumor tissue as the source of antigens for later T cell stimulation. A pre-stimulation co-incubation of tumor lysate and autologous PBMC is carried out for 10 days, with a survival dose of IL-2 given every 48 hours. After pre-stimulation, PBMC are re-stimulated for 12 hours using tumor lysate as well as positive and negative controls. The activation expression profiles of PBMC are examined via flow cytometry using a 30-marker-panel. Preliminary data using longitudinal blood sampling in 12 patients shows that autologous tumor lysate elicits activation of CD3+ cells based on a panel of classical T cell activation markers, especially 2-4 weeks after surgery. Activated T cells are FACS-sorted and their T cell receptor repertoire and gene expression is assessed on the single-cell level. In addition, tumor-reactivity is shown using autologous patient-derived organoids in T cell killing assays. This study provides evidence for an increase in activated T cells following neurosurgical resection of glioblastoma, potentially via antigen release during surgery. It not only helps to improve our understanding of the dynamics of T cell activation after glioblastoma surgery for informed timing of blood draws for cellular therapies but also suggests a strategy for selecting and expanding antigen-specific T cells from the periphery for later adoptive transfer.