75. Development of an LMP-Specific T Cell Bank for Third Party Use as a Curative Strategy Post-Transplant Lymphoproliferative Disease After Solid Organ Transplant

Abstract

EBV-associated tumors in the immune deficient host express type II and III latency antigens including latent membrane protein 1 (LMP1) and LMP2, which can serve as potential targets for immunotherapy. Several studies have documented the safety and efficacy of LMP-specific T cells for patients with EBV-associated malignancies, but clinical applications may be limited by the time to generate LMP-specific T cell products as well as the availability of an appropriate donor source. We hypothesize that the administration of “off the shelf” third party LMP-specific cytotoxic lymphocytes (LMP-CTLs) will rapidly restore EBV-specific T-cell immunity and prevent relapse in patients with post-transplant lymphoproliferative disease PTLD post solid organ transplant (SOT). To develop the third party T cell bank, we manufactured healthy donor-derived LMP-specific T cells from eligible donors with a wide range of HLA types in our good manufacturing practices (GMP) facility. This T-cell bank is for several clinical trials including a proposed multicenter Children's Oncology Group (COG) trial (ANHL1522) for patients with PTLD after SOT. Currently, 15 LMP-specific T-cell products have been manufactured from healthy donors and released for third-party use using autologous monocytes and lymphoblastoid cell lines (LCL), transduced with an adenoviral vector expressing ΔLMP1 and LMP2. T-cell products were active against LMP2 (mean:172 SFU/1×10^5 cells; range:13-655), LMP1 (33; 1-322), and LCL (87; 0-424) as determined by IFN-γ ELISPOT assay. Epitope mapping of LMP-specific T cells using IFN-γ ELISPOT assay demonstrates that these products recognize a broad epitope repertoire within LMP1 and LMP2. At the time of cryopreservation, the T-cell products comprised a mean of 45% CD8+ T-cells, 35% CD4+ T-cells, and 9% NK cells. No B cells or monocytes were detected in the final products. Thus far, one patient with NK/T cell non-Hodgkin Lymphoma received third party LMP-specific T cells achieving a very good partial response. No infusion-related toxicities were observed, and LMP-specific T cells were detectable post-infusion. Thus, third party LMP-specific T cells appear to be a safe and promising therapeutic modality for patients with EBV-associated lymphomas, and a third party bank will make this therapeutic more readily available to patients with PTLD post-SOT.