Donor lymphocyte infusion leads to diversity of specific T cell responses and reduces regulatory T cell frequency in clinical responders

Abstract

T cell responses against malignant cells play a major role in maintaining remission and prolonging overall survival in patients after allogeneic stem cell transplantation and donor lymphocyte infusion (DLI) due to graft-versus-leukemia effect. For better characterization of the T cell responses, we assessed frequency and diversity of leukemia-associated antigen (LAA)-specific cytotoxic T cells using ELISpot and pMHC multimer assays and analyzed the frequency of regulatory T cells (Treg) as well as cytokine profiles before/after DLI. The data were correlated to the clinical course of patients. Significantly more LAA-derived T cell epitopes (p = 0.02) were recognized in clinical responders (R) when compared to nonresponders (NR). In addition, pMHC multimer-based flow cytometry showed a significantly higher frequency of LAA-specific T cells in R versus NR. The frequency of Treg in R decreased significantly (p = 0.008) while keeping stable in NR. No differences in T cell subset analysis before/after DLI were revealed. Clinical responders were correlated to specific immune responses and all clinical responders showed an increase of specific immune responses after DLI. Cytokine assays using enzyme-linked immunosorbent assay showed a significant increase of IL-4 after DLI. Taken together, an increase of specific CTL responses against several LAA after DLI was detected. Moreover, this study suggests that enhanced LAA diversity in T cell responses as well as decreasing numbers of Treg contribute to clinical outcome of patients treated with DLI.

Donor Lymphocyte–Derived Natural Killer Cells Control MHC Class I–Negative Melanoma

“…A considerable proportion of the transferred NK cells developed after DLI, and NK cells were able to mediate efficient tumor control without inducing GVHD. The observation that these transferred NK cells established resistance to MHC-I negative melanoma (47,50), in which host NK cells poorly infiltrated into the tumors even when donor-type DCs became mature (Supplementary Fig. S7), confirms that MHC-I negative melanoma were susceptible to NK cell-mediated killing.…”

Immunological and Clinical Impact of Manipulated and Unmanipulated DLI after Allogeneic Stem Cell Transplantation of AML Patients

“…Moreover, clinical responders showed a significant decrease in the frequency of the highly immunosuppressive CD4+ Tregs. The quantity of Tregs remained stable in non-responders [13]. Tregs play a central role in the maintenance of self-tolerance and promote malignant cell progression by suppressing effective antitumor immunity [14], and thus it is truly striking that clinical responders in the analyzed patient cohort show a significant reduction of Treg.…”

“…For a better comprehension of the immunological function of DLI and for the recognition of immunogenic leukemia-associated antigens (LAAs), Hofmann et al [13] assessed the frequency and diversity of LAA-specific cytotoxic T cells in a small patient cohort, before and after DLI. Patients were screened for LAA-specific cytotoxic T lymphocyte (CTL) responses, number of Tregs and cytokine levels before and after DLI.…”

Neoantigen-Specific T-Cell Immune Responses: The Paradigm of NPM1-Mutated Acute Myeloid Leukemia

“…Moreover, clinical responders showed a significant reduction in the frequency of the highly immunosuppressive CD4+ Tregs. Of interest, one of the two NPM1-mutated AML patients developed NPM1-mutated-specific CTL response after administration of preemptive DLI and achieved molecular CR, whereas in the remaining clinically nonresponder case, NPM1-mutated-specific CTLs were already detectable before DLI and persisted, but without showing an increase, after DLI [59]. Collectively, the authors suggested that increased specific T-cell responses against several different LAA, enhancing GvL effect and potentially able to target LSC population, as well as decreased numbers of Tregs after prophylactic/therapeutic DLI, could contribute to favorable clinical outcomes [59][60][61].…”

“…Relevant to the allogeneic HSCT context, in a patient affected with NPM1-mutated AML in molecular relapse after allogeneic HSCT, described by a German group, preemptive DLI induced polyspecific CD8+ T cells responses directed to different LAA, including #1 and #3 NPM1-mutated peptides, which contributed to achievement of MRD negativity, thereby suggesting a correlation between GvL and LAA-specific CTL response [58]. Hofmann et al, subsequently assessed frequency and diversity of LAAspecific cytotoxic T cells in a cohort of 11 patients who had received allogeneic HSCT for different hematologic malignancies, including two NPM1-mutated AML cases in molecular relapse, before and after having received unmanipulated DLI [59]. For NPM1-mutated AML patients, NPM1-mutated epitopes, PRAME, RHAMM, proteinase 3, survivin 2, and WT1 were chosen as LAAs to be investigated.…”