Prolonged xenokidney graft survival in sensitized NHP recipients by expression of multiple human transgenes in a triple knockout pig

Abstract

Genetic modification of porcine donors, combined with optimized immunosuppression, has been shown to improve outcomes of experimental xenotransplant. However, little is known about outcomes in sensitized recipients, a population that could potentially benefit the most from the clinical implementation of xenotransplantation. Here, five highly allosensitized rhesus macaques received a porcine kidney from <i>GGTA1</i> (α1,3-galactosyltransferase) knockout pigs expressing the human <i>CD55</i> transgene (1KO.1TG) and were maintained on an anti-CD154 monoclonal antibody (mAb)-based immunosuppressive regimen. These recipients developed de novo xenoreactive antibodies and experienced xenograft rejection with evidence of thrombotic microangiopathy and antibody-mediated rejection (AMR). In comparison, three highly allosensitized rhesus macaques receiving a kidney from <i>GGTA1</i>, <i>CMAH</i> (cytidine monophospho-<i>N</i>-acetylneuraminic acid hydroxylase), and <i>b4GNT2</i>/<i>b4GALNT2</i> (β-1,4-<i>N</i>-acetyl-galactosaminyltransferase 2) knockout pigs expressing seven human transgenes including human <i>CD46</i>, <i>CD55</i>, <i>CD47</i>, <i>THBD</i> (thrombomodulin), <i>PROCR</i> (protein C receptor), <i>TNFAIP3</i> (tumor necrosis factor-α-induced protein 3), and <i>HMOX1</i> (heme oxygenase 1) (3KO.7TG) experienced significantly prolonged graft survival and reduced AMR, associated with dampened post-transplant humoral responses, early monocyte and neutrophil activation, and T cell repopulation. After withdrawal of all immunosuppression, recipients who received kidneys from 3KO.7TG pigs rejected the xenografts via AMR. These data suggest that allosensitized recipients may be suitable candidates for xenografts from genetically modified porcine donors and could benefit from an optimized immunosuppression regimen designed to target the post-transplant humoral response, thereby avoiding AMR.