title: Upfront denileukin diftitox as in vivo regulatory T-cell depletion in order to enhance vaccination effects in a canine allogeneic hematopoietic stem cell transplantation model.
abstract: Denileukin Diftitox (ONTAK(®), DAB(389) IL-2) is a recombinant DNA-derived fusion protein depleting cells that express high-affinity IL-2 receptor. Important cell targets are CD4(+)CD25(+)Foxp3(+) regulatory T cells (T(reg)). Elimination of immunosuppressive T(reg) by Denileukin Diftitox may provide a way to modulate immune tolerance following stem cell transplantation. Here, we combined T(reg) depletion with a vaccination approach to induce donor-specific immune reactions. To investigate this approach we chose the mixed chimerism canine stem cell transplantation model which represents a high state of tolerance between two hematopoietic systems. The aim was therefore to induce a graft versus hematopoiesis effect thereby converting mixed to full donor chimerism. Dog leukocyte antigen identical siblings that had developed a stable mixed chimerism after non-myeloablative stem cell transplantation received a single dose of Denileukin Diftitox (18μg/kg, i.v.) followed by several cell-lysate vaccinations. Host peripheral blood mononuclear cell lysates combined with CpG-ODN, and Montanide(®) ISA 51 were locally applied. In vitro studies demonstrated that canine T(reg) are a target of Denileukin Diftitox. The suppression of T-cell proliferation by T(reg) was abolished by addition of Denileukin Diftitox (10nM). An increase of proliferation of median 300% (range: 200%-425%) was observed. No change in donor chimerism was observed after administration of Denileukin Diftitox and vaccination. This study highlights that application of Denileukin Diftitox resulted in a depletion of T(reg) followed by an increase of immune response in vitro. This effect could not be confirmed in vivo even if the immune system was stimulated by vaccinations.
authors.affiliation: Hematology/Oncology/Palliative Medicine, University of Rostock, Ernst-Heydemann Strasse 6, 18057 Rostock, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Knueppel
authors.forename: Sandra
authors.initials: S
authors.lastname: Lange
authors.forename: Simone
authors.initials: S
authors.lastname: Altmann
authors.forename: Anett
authors.initials: A
authors.lastname: Sekora
authors.forename: Gudrun
authors.initials: G
authors.lastname: Knuebel
authors.forename: Heike
authors.initials: H
authors.lastname: Vogel
authors.forename: Iris
authors.initials: I
authors.lastname: Lindner
authors.forename: Mathias
authors.initials: M
authors.lastname: Freund
authors.forename: Christian
authors.initials: C
authors.lastname: Junghanss
mesh_terms: D000818:Animals; D046528:Chimerism / Q000662:veterinary; D004167:Diphtheria Toxin / Q000494:pharmacology / Q000627:therapeutic use*; D004285:Dogs; D005434:Flow Cytometry / Q000662:veterinary; D018380:Hematopoietic Stem Cell Transplantation / Q000379:methods / Q000662:veterinary*; D007376:Interleukin-2 / Q000494:pharmacology / Q000627:therapeutic use*; D008213:Lymphocyte Activation / Q000187:drug effects; D008212:Lymphocyte Depletion / Q000662:veterinary; D011993:Recombinant Fusion Proteins / Q000494:pharmacology / Q000627:therapeutic use; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects*; D014611:Vaccination / Q000379:methods / Q000662:veterinary*
chemical_list: D004167:Diphtheria Toxin; D007376:Interleukin-2; D011993:Recombinant Fusion Proteins; C078456:denileukin diftitox