Cytotoxic T-Cell Responses (CTL) Against Several Leukemia-Associated-Antigens (LAA) Related to the Detected Cytokine Profile in the Course of Allogeneic Hematopoietic Stem Cell Transplantation (allo-HSCT) and Donor Lymphocyte Infusion (DLI) in Patients with Different Hematological Diseases

T-cell responses play a central role in maintaining remission and prolonging overall-survival in patients with hematologic malignancies after allo-HSCT and delayed DLI. The role of LAA and mHag has to be elucidated although there is evidence that the graft-versus-leukemia-effect observed after DLI is based on CTL-mediated immunity which is reactive against mHag and LAA.

In this study, we analysed peripheral blood and serum samples of 10 patients with AML, T-NHL, CML and Multiple Myeloma in the course of allo-HSCT and before and after DLI for specific CTL responses against several LAA and established a cytokine profile. Epitopes derived from PRAME, NPM1mut, RHAMM, WT-1 and other LAA were tested. Immune reactions of CTL were measured in ELISpot assays (INF-gamma and granzyme B). In addition tetramer assays were performed. The corresponding cytokine profile of several cytokines was analysed for further interpretation of the clinical data.

In all patients we could detect a CTL response against at least one of the tested LAA in the course of DLI. Two patients were AML patients with NPM1-mutation (NPM1mut) who received preemptive DLI in molecular relapse and showed a polyspecific CTL-response against several epitopes including those derived from the mutated region of NPM1. The frequency of CTL-responses changed during the course. All of the analysed cytokines IL18, CD40L, IL1ra, IL6, IL7, IL10, IL15, IL17, IL18, IL2, IFNg and TGFß were detected in at least one of the samples of the patients, but the pattern differed dependent on the time point after allo-HSCT and DLI, immune-suppression, immune-reconstitution, GvHD and disease status. Some patients showed an increase in cytokine levels in the course of therapy, e.g. in one patient with AML with NPM1mut who received preemptive DLI in molecular relapse we detected significant higher levels of several cytokines after DLI. The patient was in molecular remission again and had developed GvHD.

Taken together, we detected CTL responses against several LAA after allo-HSCT with an increase of polyspecific T cell responses after DLI in some tested patients. These might support the role of CTL against LAA in the control of disease. Especially patients with AML with NPM1mut seem to be a very interesting population with T-cell activation after DLI. Moreover, cytokine profiles might be important and need to be correlated to the cellular responses as well as the clinical data, to further characterize the mechanisms of DLI.