Xenotransplantation Program, Department of Surgery, University of Alabama at Birmingham, Birmingham, AL, USA.
Division of Cardiothoracic Surgery, Department of Surgery, University of Alabama at Birmingham, Birmingham, AL, USA.
Transpl Immunol. 2022 Oct;74:101661. doi: 10.1016/j.trim.2022.101661. Epub 2022 Jul 3.
Pig heart xenotransplantation might act as a bridge in infants with complex congenital heart disease (CHD) until a deceased human donor heart becomes available. Infants develop antibodies to wild-type (WT, i.e., genetically-unmodified) pig cells, but rarely to cells in which expression of the 3 known carbohydrate xenoantigens has been deleted by genetic engineering (triple-knockout [TKO] pigs). Our objective was to test sera from children who had undergone palliative surgery for complex CHD (and who potentially might need a pig heart transplant) to determine whether they had serum cytotoxic antibodies against TKO pig cells.
Sera were obtained from children with CHD undergoing Glenn or Fontan operation (n = 14) and healthy adults (n = 8, as controls). All of the children had complex CHD and had undergone some form of cardiac surgery. Seven had received human blood transfusions and 3 bovine pericardial patch grafts. IgM and IgG binding to WT and TKO pig red blood cells (RBCs) and peripheral blood mononuclear cells (PBMCs) were measured by flow cytometry, and killing of PBMCs by a complement-dependent cytotoxicity assay.
Almost all children and adults demonstrated relatively high IgM/IgG binding to WT RBCs, but minimal binding to TKO RBCs (p < 0.0001 vs WT), although IgG binding was greater in children than adults (p < 0.01). All sera showed IgM/IgG binding to WT PBMCs, but this was much lower to TKO PBMCs (p < 0.0001 vs WT) and was greater in children than in adults (p < 0.05). Binding to both WT and TKO PBMCs was greater than to RBCs. Mean serum cytotoxicity to WT PBMCs was 90% in both children and adults, whereas to TKO PBMCs it was only 20% and < 5%, respectively. The sera from 6/14 (43%) children were cytotoxic to TKO PBMCs, but no adult sera were cytotoxic.
Although no children had high levels of antibodies to TKO RBCs, 13/14 demonstrated antibodies to TKO PBMCs, in 6 of these showed mild cytotoxicity. As no adults had cytotoxic antibodies to TKO PBMCs, the higher incidence in children may possibly be associated with their exposure to previous cardiac surgery and biological products. However, the numbers were too small to determine the influence of such past exposures. Before considering pig heart xenotransplantation for children with CHD, testing for antibody binding may be warranted.
猪心异种移植可能在患有复杂先天性心脏病 (CHD) 的婴儿中作为一种桥梁，直到有已故的人类供体心脏可用。婴儿会对野生型 (WT，即未经基因修饰) 猪细胞产生抗体，但很少对经过基因工程删除 3 种已知碳水化合物异种抗原表达的细胞产生抗体（三重敲除 [TKO] 猪）。我们的目的是检测接受姑息性心脏手术治疗复杂 CHD（并且可能需要猪心移植）的儿童的血清，以确定他们是否对 TKO 猪细胞有血清细胞毒性抗体。
从接受 Glenn 或 Fontan 手术的 CHD 患儿（n=14）和健康成年人（n=8，作为对照）中获取血清。所有患儿均患有复杂 CHD 并已接受某种形式的心脏手术。其中 7 例接受过人类输血，3 例接受过牛心包片移植。通过流式细胞术测量 IgM 和 IgG 与 WT 和 TKO 猪红细胞 (RBC) 和外周血单个核细胞 (PBMC) 的结合，并通过补体依赖性细胞毒性测定法测量 PBMC 的杀伤作用。
几乎所有儿童和成年人的 WT RBC 结合 IgM/IgG 均较高，但与 TKO RBC 结合较少（p<0.0001 比 WT），尽管儿童的 IgG 结合量大于成年人（p<0.01）。所有血清均显示出与 WT PBMC 的 IgM/IgG 结合，但与 TKO PBMC 的结合较少（p<0.0001 比 WT），且在儿童中大于成人（p<0.05）。与 WT 和 TKO PBMC 的结合均大于 RBC。WT PBMC 的平均血清细胞毒性在儿童和成人中均为 90%，而 TKO PBMC 的细胞毒性仅为 20%和<5%。14 名儿童中有 6 名（43%）的血清对 TKO PBMC 具有细胞毒性，但没有成人血清具有细胞毒性。
尽管没有儿童对 TKO RBC 有高水平的抗体，但 14 名儿童中有 13 名对 TKO PBMC 有抗体，其中 6 名显示出轻微的细胞毒性。由于没有成人对 TKO PBMC 有细胞毒性抗体，因此儿童的发病率较高可能与他们以前的心脏手术和生物制品暴露有关。然而，数量太少，无法确定过去暴露的影响。在考虑将猪心异种移植用于 CHD 儿童之前，可能需要进行抗体结合检测。
