Determinants of donor-specific T cell tolerance in kidney transplantation in non-sensitized recipients

Studies from our current NHPCSG U19 revealed that induction with depletional thymoglobulin in combination with maintenance with co-stimulation blockade plus rapamycin (ATG/CoB/Rapa) is a highly effective regimen in repopulating the post-depletional lymphocyte repertoire with a naïve and CoB-sensitive phenotype. In this application, we hypothesize that this newly repopulated repertoire is now susceptible to donor-specific manipulation by an innovative cellular therapy using ECDI-treated, ex vivo expanded donor B cells to induce donor-specific transplantation tolerance via donor-specific deletion, anergy and regulation. To test our hypothesis, we will (1) deliver donor ECDI-B cells in the context of ATG/CoB/Rapa and determine its efficacy on the induction of donor-specific tolerance; (2) apply the cutting-edge technology of rhesus macaque single cell immune repertoire sequencing (scIRS) pioneered by our collaborator Dr. Peng at NCSU to investigate and precisely quantify donor-specific deletion, anergy or regulation at a single cell level. As infections have been brought into sharp focus by the recent SARS-CoV2 pandemic and have been shown to have a profound effect on the susceptibility and stability of immune tolerance, we propose to further interrogate the interaction between anti-viral immunity and donor-specific immune tolerance at a molecular level. We propose to use cytomegalovirus (CMV) as a model pathogen as it is commonly encountered in transplant recipients. With these goals in mind, we constructed three specific aims for this Project: Aim 1 will determine the efficacy of transplantation tolerance by donor ECDI-B cell infusions in the presence of ATG/CoB/Rapa in rhesus kidney transplantation, modeling both deceased donor as well as living donor kidney transplantation; Aim 2 will determine the effect of CVM exposures on the induction and maintenance of transplantation tolerance in rhesus macaques; and Aim 3 will employ cutting edge technologies including scIRS and the expertise in high- dimensional data analytics provided by the CIC to examine lymphocyte repertoire and functionality under tolerance conditions with or without concurrent CMV infection. At the completion of this project, we will: 1) establish a clinically feasible and effective regimen for transplantation tolerance induction in rhesus macaques using a combination of depletional induction and infusions of ECDI-fixed donor leukocytes; 2) understand the cellular and molecular mechanisms of this tolerance approach; 3) determine the effective components of therapeutic strategies to preserve transplantation tolerance in settings of unexpected viral infections. These advances will ultimately position us to conduct a first-in-human kidney transplant tolerance trial testing the optimized combinatorial regimen of donor ECDI-B cell infusions in the context of ATG/CoB/Rapa.