Competitive repopulation and allo-immunologic pressure determine chimerism kinetics after T Cell-depleted allogeneic stem cell transplantation and donor lymphocyte infusion

After allogeneic stem cell transplantation (alloSCT), patient-derived stem cells that survived the pretransplantation conditioning compete with engrafting donor stem cells for bone marrow (BM) repopulation. In addition, donor-derived alloreactive T cells present in the stem cell product may favor establishment of complete donor-derived hematopoiesis by eliminating patient-derived lymphohematopoietic cells. T cell-depleted alloSCT with sequential transfer of potentially alloreactive T cells by donor lymphocyte infusion (DLI) provides a unique opportunity to selectively study how competitive repopulation and allo-immunologic pressure influence lymphohematopoietic recovery. This study aimed to determine the relative contribution of competitive repopulation and donor-derived anti-recipient alloimmunologic pressure on the establishment of lymphohematopoietic chimerism after alloSCT. In this retrospective cohort study of 281 acute leukemia patients treated according to a protocol combining alemtuzumab-based T cell-depleted alloSCT with prophy-lactic DLI, we investigated engraftment and quantitative donor chimerism in the BM and immune cell subsets. DLI-induced increase of chimerism and development of graft-versus-host disease (GVHD) were analyzed as complementary indicators for donor-derived anti-recipient alloimmunologic pressure. Profound suppression of patient immune cells by conditioning sufficed for sustained engraftment without necessity for myeloablative conditioning or development of clinically significant GVHD. Although 61% of the patients without any DLI or GVHD showed full donor chimerism (FDC) in the BM at 6 months after alloSCT, only 24% showed FDC in the CD4+ T cell compartment. In contrast, 75% of the patients who had received DLI and 83% of the patients with clinically significant GVHD had FDC in this compartment. In addition, 72% of the patients with mixed hematopoiesis receiving DLI converted to complete donor-derived hematopoiesis, of whom only 34% developed clinically significant GVHD. Our data show that competitive repopulation can be sufficient to reach complete donor-derived hematopoiesis, but that some alloimmunologic pressure is needed for the establishment of a completely donor-derived T cell compartment, either by the development of GVHD or by administration of DLI. We illustrate that it is possible to separate the graft-versus-leukemia effect from GVHD, as conversion to durable complete donor-derived hematopoiesis following DLI did not require induction of clinically significant GVHD. (c) 2023 The American Society for Transplantation and Cellular Therapy. Immunobiology of allogeneic stem cell transplantation and immunotherapy of hematological disease

Rapid Re-expression of Retrovirally Introduced Versus Endogenous TCRs in Engineered T cells After Antigen-specific Stimulation

To broaden the applicability of cellular immunotherapy, adoptive transfer of T-cell receptor (TCR) transferred T cells may be an attractive strategy. Using this approach, high numbers of defined antigen-specific T cells can be engineered. As the introduced TCR has to compete for cell surface expression with the endogenous TCR, the introduced TCR chains are under control of a strong viral promotor, which, in contrast to the endogenous promotor, is constitutively active. We examined whether this difference in regulation would result in differences in TCR internalization and re-expression of the introduced and endogenous TCR on dual TCR engineered T cells and the antigen-responsiveness of both the TCRs. We showed comparable TCR downregulation of TCRs expressed under regulation of a retroviral promotor or the endogenous promotor. However, the introduced TCRs were rapidly re-expressed on the cell surface after TCR stimulation. Despite rapid re-expression of the introduced TCR, T cells exerted similar antigen-sensitivity compared with control T cells, showing that cell mechanisms other than TCR cell surface expression are involved in antigen-sensitivity directly after antigen-specific stimulation. These results showed that TCR transduced T cells are functionally not different from nontransduced T cells and can potentially be used as an effective treatment strategy.Immunobiology of allogeneic stem cell transplantation and immunotherapy of hematological disease

Eradication of Recipient CMV Specific T Cells by Donor Lymphocyte Infusion Does Not Impair Protective Immunity In Patients Transplanted with a CMV Negative Donor Due to An Early Donor Derived Primary CMV Specific T Cell Response

Immunobiology of allogeneic stem cell transplantation and immunotherapy of hematological disease

Eradication of Recipient CMV Specific T Cells by Donor Lymphocyte Infusion Does Not Impair Protective Immunity In Patients Transplanted with a CMV Negative Donor Due to An Early Donor Derived Primary CMV Specific T Cell Response

Immunobiology of allogeneic stem cell transplantation and immunotherapy of hematological disease

Digestibility and absorption of deoxynivalenol-3-ß-glucoside in in vitro models

Certain mycotoxins may be present in plant materials as their glucosides. The question is whether these glucosides may be hydrolysed into their parent compounds in the gastro-intestinal tract (GI-tract), thus increasing the exposure. Therefore, the potential hydrolysis of deoxynivalenol-3-ß-glucoside (DON-3G) to deoxynivalenol (DON) was assessed in two in vitro models representing the human upper GI-tract (mouth, stomach and small intestine). In a fed digestion model, there was no evidence of release of DON from DON-3G, spiked at a level of 2,778 µg DON- 3G/kg food. This shows that the conditions in the GI-tract do not result in hydrolysis of this glucoside into the original mycotoxin. The absorption and transformation of DON-3G in the small intestine was assessed in an in vitro model with human Caco-2 cells in a Transwell system. No evidence was found for the transformation of DON-3G to DON by the Caco-2 cells in both the apical or basolateral side in 24 hours (cells were exposed to 2.4 nmol DON- 3G/ml medium). However, when DON itself was added to the apical side an amount of 23% of the spiked DON was detected in the basolateral side after 24 hours (cells were exposed to 2.3 nmol/ml medium). In conclusion, no evidence was found in the in vitro experiments for significant elevated exposure of humans to DON, since DON- 3G was not hydrolysed to DON in the digestion model representing the upper part of the GI-tract and DON-3G was not hydrolysed to DON by the intestinal epithelial Caco-2 cells. It was shown that bioavailability of DON-3G in humans may be low as compared to DON since Caco-2 cells did not absorb DON-3G, in contrast to DON

T Cell Chimerism After T Cell Depleted Allogeneic Stem Cell Transplantation Is Influenced by Immunological Factors Including the Conditioning Regimen, CMV Serostatus and GvHD and Does Significantly Bias Overall Chimerism Status

Immunobiology of allogeneic stem cell transplantation and immunotherapy of hematological disease

Impact of alemtuzumab pharmacokinetics on T-cell dynamics, graft-versus-host disease and viral reactivation in patients receiving allogeneic stem cell transplantation with an alemtuzumab-based T-cell-depleted graft

Administration of alemtuzumab (targeting the CD52 antigen) to the patient (in-vivo) or to the graft (in-vitro) before allogeneic stem cell transplantation (alloSCT) decreases the incidence of graft-versus-host disease (GvHD). Effectiveness of this treatment relies on depletion of donor T cells. Currently, no data are available on alemtuzumab pharmacokinetics and pharmacodynamics in patients who received combined in-vivo and in-vitro alemtuzumab-based T-cell depletion. In this prospective study, we analyzed alemtuzumab pharmacokinetics and its effect on the circulating T cells in 36 patients who received an allogeneic T-cell-depleted graft by addition of 20 mg alemtuzumab "to the bag" with or without prior alemtuzumab (30 mg cumulative dose intravenously) as part of the conditioning regimen. Effective T-cell depletion was shown for all patients, even though alemtuzumab plasma levels varied considerably. Peak alemtuzumab levels were observed directly after graft infusion and were not associated with the number of circulating T cells pre-infusion, but with plasma volumes of the patients. All patients engrafted, confirming feasibility of this transplantation protocol. Only three patients with low alemtuzumab levels developed acute GvHD (grade II in 2 patients and grade III in 1 patient). Persistence of circulating alemtuzumab at 3 weeks after transplantation had prevented reconstitution of CD52-positive T cells when alemtuzumab plasma levels were above 0.7 mu g/mL. However, overall T-cell reconstitution did not correlate with the levels of alemtuzumab exposure, due to early reconstitution of CD52-negative alemtuzumab-resistant T cells. The protective effect of these cells likely explains the low incidence of Epstein-Barr-virus- and cytomegalovirus-related disease despite circulating alemtuzumab.Personalised Therapeutic

CD4 Donor Lymphocyte Infusion Can Cause Conversion of Chimerism Without GVHD by Inducing Immune Responses Targeting Minor Histocompatibility Antigens in HLA Class II

Stemcel biology/Regenerative medicine (incl. bloodtransfusion

Phase I/II clinical trial demonstrates feasibility, safety and effectivity of CMV-pp65-specific donor T-cells for the treatment of refractory CMV reactivation after allogeneic stem cell transplantation

Immunobiology of allogeneic stem cell transplantation and immunotherapy of hematological disease