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

Vet Immunol Immunopathol. 2012 Jan 15;145(1-2):233-40. doi: 10.1016/j.vetimm.2011.11.009. Epub 2011 Nov 25.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chimerism / veterinary
  • Diphtheria Toxin / pharmacology
  • Diphtheria Toxin / therapeutic use*
  • Dogs
  • Flow Cytometry / veterinary
  • Hematopoietic Stem Cell Transplantation / methods
  • Hematopoietic Stem Cell Transplantation / veterinary*
  • Interleukin-2 / pharmacology
  • Interleukin-2 / therapeutic use*
  • Lymphocyte Activation / drug effects
  • Lymphocyte Depletion / veterinary
  • Recombinant Fusion Proteins / pharmacology
  • Recombinant Fusion Proteins / therapeutic use
  • T-Lymphocytes, Regulatory / drug effects*
  • Vaccination / methods
  • Vaccination / veterinary*

Substances

  • Diphtheria Toxin
  • Interleukin-2
  • Recombinant Fusion Proteins
  • denileukin diftitox