Simultaneous Isolation and Enrichment of Multi Specific and Multi Functional T-Cells Populations for Treatment of Patients Undergoing Allogeneic Hematopoetic Stem Cell Transplantation,

Abstract 4056

Allogeneic hematopoetic stem cell transplantation (aHSCT) is a treatment option for a variety of diseases in particular heamatological malignancies. Due to an ongoing immunosuppression to prevent graft versus host reaction (GvHD), disease relapses as well as viral infections are major causes of morbidity and mortality after aHSCT.

T cell responses against different tumor-associated and tumor-specific antigens could be detected not only in patients with malignant diseases but also in healthy donors. We investigated the selection of MART-1 (Melanoma Antigen Recognized by T-cells), Proteinase 3 and WT-1 (Wilms Tumor- Antigen) specific T cells from the blood of healthy donors as basis for a tumor-specific T cell transfer in the context of aHSCT.

With a newly established protocol, based on streptamer selection, we isolated simultaneously multi-functional and multi-specific T-cell populations. We selected tumor-antigen-specific CTL′s (Cytotoxic T- Lymphocytes) mentioned above and also antiviral T-cells namely against CMV, EBV and AdV from a single blood donation. In this simultaneous selection with up to 7 different epitopes in one step, even the tumor specific T cells, which are known to be rarely detected among healthy donors, could be enriched to an amount sufficient for a direct T cell transfer.

Purity achieved after selection was at least 82% and up to 98,87%, which minimizes the risk for GvHD after clinical application. The possibility to transfer these selected CTL`s to patients after stem cell transplantation improves the graft versus tumor effect as well as the anti infective T cell immunity without a relevant risk for GvHD.

Furthermore, the selected multi specific T cell populations could be expanded in vitro without loss of specificity and include different phenotypes such as central memory and memory effector cells, which may provide long lasting immunity.

Moreover, starting with a leukapheresis, we successfully transferred our selection protocol in a closed system according to current good manufacturing practice (cGMP) requirements, which allows clinical application in the future. With that, it opens new perspectives in cellular immunotherapy against malignancies and viral infection for patients after aHSCT.