Preclinical Translation of Kidney, Heart, and Lung Xenotransplantation

Massachusetts General Hospital, Boston MA

Investigators

Abstract

ABSTRACT To earn the confidence of the scientific community, regulatory authorities, and, ultimately, our patients that xenotransplantation deserves to be systematically evaluated in humans, it is essential to demonstrate consistent long-term, life-supporting xenograft survival in a preclinical model. Although we have accomplished over one year of life-supporting survival in nonhuman primates (NHPs) using kidney xenografts with knockout (KO) of genes encoding three major carbohydrate xenoantigens (GalT, b4GalNT2 and CMAH KO, triple knock-out, TKO) and multiple additional human transgenes, thrombotic microangiopathy (TMA) and antibody-mediated rejection (AMR) remain the primary, prevalent causes of the TKO-based multi-gene edited (multi-GE) kidney and also heart and lung xenograft loss. We will test four working hypotheses regarding the reason for these preclinical and, in the case of heart xenografts, clinical failures. First, strong evidence implicates that knocking out the CMAH gene in TKO (but not DKO) swine unveils the expression of a ‘4th antigen’ that is the target of innate immunity in NHP but is irrelevant in human recipients. We will evaluate the contribution of the CMAH gene KO to pathogenic immune injury occurring in TKO organ xenografts by comparing the performance, histology, and molecular profile of kidneys, hearts, and lungs from 10-GE TKO to those from 9-GE DKO pig. We expect results using DKO-based 9-GE pig organs will enable the design of IND-qualifying organ xenograft trials for one or more organs. Second, based on compelling in vitro, ex vivo, and in vivo evidence that NK cells contribute significantly to heart, kidney, and lung xenograft injury, we will test the hypothesis that activation of NK cells will be inhibited by HLA-E expression on pig endothelium, which will attenuate inflammation and injury both in the xenograft and systemically in the recipient. Third, we will optimize the immunosuppressive regimen for kidney, heart, and lung xenografts. Finally, we will evaluate complement inhibition, CD11b blockade, donor macrophage depletion, and ischemia minimization as strategies tailored to each organ with the general objective of effectively modulating inflammation in the graft and organ xenograft recipient. The hypotheses, aims, and experimental approaches are harmonized between each Project and supported by Administrative, Pathology Mechanistic, Infectious Disease, and Swine Production Cores, which together will facilitate a coordinated effort to understand and overcome the remaining barriers to the clinical application of kidney heart, and lung xenografts. To our knowledge, MGH is the only center in the world capable of performing comprehensive comparative studies of kidney, heart, and lung xenotransplantation in preclinical models. We anticipate that together, these highly interactive projects will generate one or more safe and effective protocols ready for clinical trial by the end of the funding period. If successful, these studies would impact the entire field of transplantation.