Significance of anti-gal IgG in chronic xenograft rejection

doi:10.1016/S0041-1345(98)01846-6

Transplantation Proceedings

Volume 31, Issues 1–2, February–March 1999, Pages 940-941

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Anti-gal IgG production in chronic xenograft rejection

The long-term immune response in humans to α-gal epitope on pig xenografts could be studied in diabetic patients that were transplanted with cultured fetal pig pancreatic islet cell clusters.8 These patients were simultaneously transplanted with a kidney allograft and subjected to extensive immunosuppressive regimens. Analysis of anti-Gal activity in these patients demonstrated an average 50-fold increase in this antibody titer.9 Furthermore, the affinity of anti-Gal in these patients increased

Association between α-Gal epitope expression on xenograft and inflammatory infiltrates

Cartilage xenografts explanted from monkeys 2 months after transplantation contained extensive mononuclear inflammatory infiltrates that were comprised of approximately 70% T lymphocytes and 30% macrophages. Complete removal of α-gal epitopes from pig cartilage was achieved by incubation with 100 U/mL of recombinant α-galactosidase, for 4 hours at 26°C, followed by extensive washes to remove the enzyme.12 The recombinant enzyme was cloned from coffee beans and expressed in yeast.13 Monkeys

Endothelial cell activation by anti-gal

Palmetshofer et al14 incubated pig endothelial cells with sera from cynomolgus monkeys transplanted with pig cartilage, described earlier. Such incubation resulted in activation of the endothelial cells as indicated by the increased E-selection expression. Specific removal of anti-Gal from the sera eliminated their activating effect. Furthermore, sera obtained from the same monkeys prior to transplantation did not activate pig endothelial cells. These data imply that high-affinity anti-Gal

Conclusions

High-affinity anti-Gal IgG molecules produced in large amounts in response to α-gal epitopes in xenografts are detrimental to the xenograft and mediate chronic xenograft rejection. This antibody induces xenograft destruction by ADCC, by activation of the endothelial cells within the graft and by increasing activation of T cells against xenograft antigens.

Immunosuppressive drugs that effectively suppress allograft rejection fail to prevent production of the elicited high-affinity anti-Gal.

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Cited by (16)

Galactosyl-knock-out engineered pig as a xenogenic donor source of adipose MSCs for bone regeneration
2013, Biomaterials
Citation Excerpt :
Lipoaspiration products were kept for a maximum of 90 min (mean 43 ± 21 min) at 4 °C until tissue digestion and the AMSC isolation procedure. Two different pig strains were used as AMSCs donors: Belgian Landrace pigs (as galactosyl-positive [Gal+] cells; Centre A. de Marbaix, Université catholique de Louvain, Louvain-la-Neuve, Belgium) and homozygous Gal-KO pigs (Xenome consortium research group, C. Galli/Italy; H. Niemman/Germany) [21]. Animals were housed separately in accordance with the guidelines of the Belgian Ministry of Agriculture and Animal Care.
Pig adipose mesenchymal stem cells (AMSCs) could be proposed for the improvement of bone substitute. However, these xenogenic cells retain a galactosyl (Gal) epitope that elicits xenorejection. Our work aims to use Gal-Knock-Out (Gal-KO) pig AMSCs to associate cellular immunomodulation, humoral down-elicitation of Gal-KO cells and osteogenic capacity of AMSCs. Human and pig AMSCs were compared for proliferation/differentiation kinetics and bone neoformation in vivo. Humoral reaction against pig Gal+ vs. Gal-KO AMSCs and immunomodulation properties of Gal+ vs. Gal-KO AMSCs were assessed in vitro. Humoral/cellular reactions against Gal+ vs. Gal-KO osteogenic differentiated pig AMSC xenografts were assessed in an immunocompetent rodent model. Expansion/differentiation/bone neoformation was significantly improved with differentiated pig AMSCs compared with human cells. Based on immunohistochemistry and cell-based ELISA, Gal+ AMSCs had higher sensitivity to preformed/induced anti-pig antibodies than Gal-KO AMSCs. In vitro cellular immunomodulation was similar between Gal+ and Gal-KO AMSCs. In vivo, a significant reduction of anti-pig IgG was found at 1 month in rats implanted with Gal-KO AMSCs compared with those implanted with Gal+ AMSCs. Lymphocyte/macrophage infiltration of osteogenic differentiated pig AMSC xenografts was significantly lower at post-operative day (POD) 7 in recipients of Gal-KO vs. Gal+ pig cells. No significant difference was found at POD 28. The combination of the cellular immunomodulation with the Gal-KO phenotype of AMSCs can significantly improve the cellular engraftment of pig osteogenic cells by delaying xenorejection.
Distribution of the Alpha-Gal Epitope on Adult Porcine Bone Tissue
2006, Transplantation Proceedings
Citation Excerpt :
In the chronic xenograft rejection of meniscus cartilage, high-affinity anti-Gal IgG molecules are produced in large amounts in response to alpha-Gal epitopes in xenografts. This antibody induces xenograft destruction by ADCC, by activation of endothelial cells within the graft, and by increased activation of T cells against xenograft antigens.6 Just like cartilage xenografts, we presumed that alpha-Gal epitopes may also induce acute vascular rejection and chronic rejection in bone xenografts.
Bone xenografts from pig to human appear to be an alternative to resolve the shortage of bone autologous and allografts. However, the major obstacle of pig-to-human xenotransplantation is the interaction between human natural anti-Gal antibody and the alpha-Gal epitope abundantly expressed on pig endothelium. It was important to investigate the expression of alpha-Gal epitopes in porcine bone tissue to look for an ideal method to remove the alpha-Gal epitopes.
The cortical and trabecular bone were retrieved from five pigs. After the soft tissues and periosteum were removed, the blood and marrow cavity were cleaned with phosphate-buffered solution. All 5 mm × 5 mm × 5 mm samples were imbedded in paraffin and methyl methacrylate resin for histological sections. The mouse IgM M86 monoclonal antibody, which was highly specific for alpha-Gal epitopes, was used to document alpha-Gal epitope expression by immunostaining of tissues and immunofluorescence.
Gal-positive immunostaining and immunofluorescence were observed on the surface of osteocytes and Haversian canals. There was a significant difference in Gal expression between cortical and trabecular bone tissues. There was no Gal expression in the extracellular matrix of bone.
Major alpha-Gal epitopes were on the surface of osteocytes of porcine bone tissues. A method should be used to damage the osteocytes and eliminate the alpha-Gal epitopes to avoid the xenogenic rejection in xenotransplantation of porcine bone tissues.
Identification of peptide mimetics of xenoreactive α-Gal antigenic epitope by phage display
2006, Biochemical and Biophysical Research Communications
The prevention of hyperacute rejection (HAR) triggered by interaction between the human natural antibody and xenoreactive antigenic epitope (Gal-α1, 3Gal) present on pig cells is the key to success in pig-to-human xenotransplantation. The phage display technology offers an effective strategy for screening peptides which can interact with the anti-Gal antibody to block α-Gal antigen binding site. Two peptide libraries, linear 7 peptide library and C7C library, were panned on the anti-B monoclonal antibody which has the characteristic of binding to the α-Gal antigenic epitope. After four rounds of panning, 22 positive phage clones were selected. Highly homologous sequence PT and STL existed among these selected peptides. Stachyose competitive ELISAs revealed that these peptides specifically bound to α-Gal antigen binding site. Eight peptide mimics of α-Gal antigenic epitope could inhibit the agglutination of pig red blood cells mediated by human sera in a dose-dependent manner. These results demonstrated that the selected peptides can mimic the conformational structure of α-Gal antigenic epitope and have the therapeutic potential in xenotransplantation.
Tolerance induction by lentiviral gene therapy with a nonmyeloablative regimen
2006, Blood
Citation Excerpt :
All mammals except humans, apes, and old-world monkeys express α1,3 galactosyltransferase (GalT), hence Galα1,3Galβ1, 4GlcNac-R (αGal) is expressed on most tissues including vascular endothelium.2-4 However, as humans have natural antibodies (Abs) against αGal, it is known that xenotransplantation of pig organs into humans induces hyperacute rejection, acute vascular rejection/delayed xenograft rejection, and even chronic rejection against αGal.5-7 In pig-to-primate discordant combination, 80% to 90% of antipig xenogeneic Abs are anti-αGal Abs.8
Antibodies (Abs) directed at the Galα1,3Galβ1,4GlcNAc-R (αGal) carbohydrate epitope initiate xenograft rejection. Previously, we have shown that bone marrow transplantation (BMT) with lentivirus-mediated gene transfer of porcine α1,3 galactosyltransferase (GalT) is able to induce tolerance to αGal-expressing heart grafts following a lethal dose of irradiation. Here we show the first demonstration of permanent survival of αGal⁺ hearts following transplantation with autologous, lentivirus-transduced BM using a nonmyeloablative regimen. Autologous BM from GalT knockout (GalT^–/–) mice was transduced with a lentiviral vector expressing porcine GalT and transplanted into sublethally irradiated (3 Gy) GalT^–/– mice. Chimerism in the peripheral blood cells (PBCs) remained low but was higher in the BM, especially within the stromal cell population. Mice reconstituted with GalT did not produce anti-αGal Abs over time. We immunized these mice with αGal-expressing cells and assessed humoral immune responses. Anti-αGal xenoantibodies were not produced in mice reconstituted with GalT, but normal Ab responses to other xenoantigens were detected. Mice reconstituted with GalT accepted αGal⁺ heart grafts over 100 days. Transduction with lentiviral vectors results in chimerism at levels sufficient to induce long-term tolerance under nonmyeloablative conditions.
Carbohydrates in transplantation
1999, Current Opinion in Chemical Biology
Carbohydrate materials have become increasingly utilized in transplantation and cell/tissue engineering within the past year. This has been well documented in recent applications of immobilized or soluble α-galactosyl epitopes (i.e. oligosaccharides with a terminal Galα1–3Gal sequence) in preventing hyperacute rejection in pig-to-primate xenotransplantation. In addition, α-galactosyl polymers have been shown to exhibit much greater activity (up to 10⁴ times) than α-galactosyl monomers in inhibiting the binding of anti-galactosyl antibodies to pig kidney epithelial cells and assisting in the prevention of cytotoxicity in human serum.
A porcine xenograft-derived bone scaffold is a biocompatible bone graft substitute: An assessment of cytocompatibility and the alpha-Gal epitope
2019, Xenotransplantation

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Proceedings of the XVIITH World Congress of the Transplantation SocietySignificance of anti-gal IgG in chronic xenograft rejection

Section snippets

Anti-gal IgG production in chronic xenograft rejection

Association between α-Gal epitope expression on xenograft and inflammatory infiltrates

Endothelial cell activation by anti-gal

Conclusions

Immunol Today

Lancet

Arch Biochem Biophys

Transplant Proc

Proc Natl Acad Sci USA

J Immunol

Transplantation

Proceedings of the XVIITH World Congress of the Transplantation Society
Significance of anti-gal IgG in chronic xenograft rejection