The Knife's Edge of Tolerance: Inducing Stable Multilineage Mixed Chimerism but With a Significant Risk of CMV Reactivation and Disease in Rhesus Macaques

Am J Transplant. 2017 Mar;17(3):657-670. doi: 10.1111/ajt.14006. Epub 2016 Sep 19.

Abstract

Although stable mixed-hematopoietic chimerism induces robust immune tolerance to solid organ allografts in mice, the translation of this strategy to large animal models and to patients has been challenging. We have previously shown that in MHC-matched nonhuman primates (NHPs), a busulfan plus combined belatacept and anti-CD154-based regimen could induce long-lived myeloid chimerism, but without T cell chimerism. In that setting, donor chimerism was eventually rejected, and tolerance to skin allografts was not achieved. Here, we describe an adaptation of this strategy, with the addition of low-dose total body irradiation to our conditioning regimen. This strategy has successfully induced multilineage hematopoietic chimerism in MHC-matched transplants that was stable for as long as 24 months posttransplant, the entire length of analysis. High-level T cell chimerism was achieved and associated with significant donor-specific prolongation of skin graft acceptance. However, we also observed significant infectious toxicities, prominently including cytomegalovirus (CMV) reactivation and end-organ disease in the setting of functional defects in anti-CMV T cell immunity. These results underscore the significant benefits that multilineage chimerism-induction approaches may represent to transplant patients as well as the inherent risks, and they emphasize the precision with which a clinically successful regimen will need to be formulated and then validated in NHP models.

Keywords: animal models: nonhuman primate; bone marrow/hematopoietic stem cell transplantation; tolerance: chimerism; translational research/science.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Communicable Diseases / etiology
  • Communicable Diseases / pathology
  • Cytomegalovirus / immunology*
  • Cytomegalovirus Infections / complications*
  • Cytomegalovirus Infections / immunology
  • Cytomegalovirus Infections / virology
  • Graft Survival
  • Graft vs Host Disease / etiology
  • Graft vs Host Disease / pathology
  • Hematopoietic Stem Cell Transplantation
  • Macaca mulatta
  • Skin Transplantation*
  • T-Lymphocytes / immunology*
  • Transplantation Chimera / immunology*
  • Transplantation Conditioning
  • Transplantation Tolerance / immunology*
  • Transplantation, Homologous
  • Virus Activation / immunology*