Decellularized GGTA1-KO pig heart valves do not bind preformed human xenoantibodies

Pre-clinical and clinical data have unequivocally demonstrated the usefulness of decellularized heart valve (HV) matrices implanted for HV replacement therapy. However, human donor valves applicable for decellularization are in short supply, which prompts the search for suitable alternatives, such as porcine grafts. Since decellularization might be insufficient to remove all xenoantigens, we analysed the interaction of human preformed antibodies with decellularized porcine HV in vitro to assess potential immune reactions upon implantation. Detergent-decellularized pulmonary HV from German Landrace wild-type (wt) or α1,3-galactosyltransferase knockout (GGTA1-KO) pigs were investigated by inhibition ELISA and GSL I-B4 staining to localize and quantify matrix-bound αGal epitopes, which represent the most prominent xenoantigen. Additionally, preformed human xenoantibodies were affinity purified by perfusing porcine kidneys. Binding of purified human antibodies to decellularized HV was investigated by inhibition ELISA. Furthermore, binding of human plasma proteins to decellularized matrices was determined by western blot. Decellularized human pulmonary artery served as controls. Decellularization of wt HV led to a reduction of αGal epitopes by 70 %. Residual epitopes were associated with the subendothelial extracellular matrix. As expected, no αGal epitopes were found on decellularized GGTA1-KO matrix. The strongest binding of preformed human anti-pig antibodies was found on wt matrices, whereas GGTA1-KO matrices bound similar or even fewer xenoantibodies than human controls. These results demonstrate the suitability of GGTA1-KO pigs as donors for decellularized heart valves for human patients. Besides the presence of αGal antibodies on decellularized heart valves, no further preformed xenoantibodies against porcine matrix were detected in tested human sera.