title: CD154 blockade, sirolimus, and donor-specific transfusion prevents renal allograft rejection in cynomolgus monkeys despite homeostatic T-cell activation.
abstract: BACKGROUND
  CD154-specific antibodies have been shown to prevent acute rejection in many preclinical models including nonhuman primates (NHPs). However, they have been ineffective in pilot clinical trials, suggesting a need for more robust preclinical analysis. One factor affecting the disparate results may be related to the recipient's immune activation state. Specifically, adult humans have a high percentage of memory-phenotype T cells compared to young animals. Postdepletional homeostatic repopulation has been shown to enrich for memory-phenotype T cells and interfere with CD154-based therapies in rodents.
  
  
  METHODS
  We developed a NHP model nonspecifically enriched for peripheral memory-phenotype T cells. Thymectomized cynomolgus macaques underwent depletion with polyclonal anti-thymocyte globulin followed by repopulation. Peripheral phenotype was serially determined using polychromatic flow cytometry. In vitro response to donor and environmental antigens was also confirmed before and after manipulation. We then tested a regimen previously successful in rhesus monkeys combining anti-CD154, sirolimus, and donor-specific blood transfusion (DST), in a second primate species with and without the provocation of increased peripheral homeostatic T-cell activation.
  
  
  RESULTS
  Monkeys that were thymectomized (n=3) and depleted recovered via homeostatic repopulation with a repertoire enriched for cells with a memory surface phenotype compared to unmanipulated controls (n=3). Despite a repertoire markedly enriched for memory-phenotype cells, the regimen effectively prevented acute rejection for the duration of therapy.
  
  
  CONCLUSIONS
  Cynomolgus monkeys can be rendered memory phenotype enriched using homeostatic repopulation. Despite a generally activated T-cell repertoire, anti-CD154, sirolimus, and DST effectively prevents rejection in cynomolgus monkeys.
authors.affiliation: Transplantation Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, USA.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Pearl
authors.forename: He
authors.initials: H
authors.lastname: Xu
authors.forename: Frank
authors.initials: F
authors.lastname: Leopardi
authors.forename: Edwin
authors.initials: E
authors.lastname: Preston
authors.forename: Allan D
authors.initials: AD
authors.lastname: Kirk
mesh_terms: D000818:Animals; D001803:Blood Transfusion; D023201:CD40 Ligand / Q000037:antagonists & inhibitors*; D006084:Graft Rejection / Q000517:prevention & control*; D006706:Homeostasis; D007156:Immunologic Memory; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D016030:Kidney Transplantation; D008213:Lymphocyte Activation; D008252:Macaca fascicularis; D010641:Phenotype; D020123:Sirolimus / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000276:immunology*; D013934:Thymectomy; D014019:Tissue Donors; D014184:Transplantation, Homologous
chemical_list: D007166:Immunosuppressive Agents; D023201:CD40 Ligand; D020123:Sirolimus