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Hara H, Yamamoto T, Wei HJ, Cooper DK. What Have We Learned From In Vitro Studies About Pig-to-primate Organ Transplantation? Transplantation 2023; 107:1265-1277. [PMID: 36536507 PMCID: PMC10205677 DOI: 10.1097/tp.0000000000004458] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Natural preformed and de novo antibodies against pig antigens are a major cause of pig xenograft rejection in nonhuman primates (NHPs). In vivo studies in pig-to-NHP models are time consuming. In vitro assays, for example, antibody binding to pig cells, complement-dependent cytotoxicity assays, provide valuable information quickly and inexpensively. Using in vitro assays for several years, it has been documented that (1) during the first year of life, humans and NHPs develop anti-wild-type pig antibodies, but humans develop no or minimal antibody to triple-knockout (TKO) pig cells. (2) Some adult humans have no or minimal antibodies to TKO pig cells and are therefore unlikely to rapidly reject a TKO organ, particularly if the organ also expresses human "protective" proteins. (3) There is good correlation between immunoglobulin (Ig)M (but no t IgG) binding and complement injury. (4) All Old World NHPs develop antibodies to TKO pig cells and are not optimal recipients of TKO organs. (5) galactosyltransferase gene-knockout/β4GalNT2KO pigs are preferred for Old World NHPs. (6) Humans develop anti-pig IgE and IgA antibodies against pig cells, but their role remains uncertain. (7) In a small percentage of allosensitized humans, antibodies that cross-react with swine leukocyte antigens may be detrimental to a pig organ xenograft. (8) Prior sensitization to pig antigens is unlikely to be detrimental to a subsequent allograft. (9) Deletion of expression of Gal and Neu5Gc is associated with a reduction in the T-cell response to pig cells. All of these valuable observations have largely predicted the results of in vivo studies.
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Affiliation(s)
- Hidetaka Hara
- College of Veterinary Medicine, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Takayuki Yamamoto
- Department of Surgery, Center for Transplantation Sciences, Massachusetts General Hospital/Harvard Medical School, Boston, MA
| | - Hong-Jiang Wei
- College of Veterinary Medicine, Yunnan Agricultural University, Kunming, Yunnan, China
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming, Yunnan, China
| | - David K.C. Cooper
- Department of Surgery, Center for Transplantation Sciences, Massachusetts General Hospital/Harvard Medical School, Boston, MA
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2
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Olivera-Ardid S, Bello-Gil D, Tuzikov A, Araujo RN, Ferrero-Alves Y, García Figueroa BE, Labrador-Horrillo M, García-Pérez AL, Bovin N, Mañez R. Poly-L-Lysine-Based αGal-Glycoconjugates for Treating Anti-αGal IgE-Mediated Diseases. Front Immunol 2022; 13:873019. [PMID: 35432370 PMCID: PMC9009260 DOI: 10.3389/fimmu.2022.873019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 03/02/2022] [Indexed: 11/25/2022] Open
Abstract
Anti-αGal IgE antibodies mediate a spreading allergic condition known as αGal-syndrome (AGS). People exposed to hard tick bites are sensitized to αGal, producing elevated levels of anti-αGal IgE, which are responsible for AGS. This work presents an immunotherapy based on polymeric αGal-glycoconjugates for potentially treating allergic disorders by selectively inhibiting anti-αGal IgE antibodies. We synthesized a set of αGal-glycoconjugates, based on poly-L-lysine of different degrees of polymerization (DP1000, DP600, and DP100), to specifically inhibit in vitro the anti-αGal IgE antibodies in the serum of αGal-sensitized patients (n=13). Moreover, an animal model for αGal sensitization in GalT-KO mice was developed by intradermal administration of hard tick' salivary gland extract, mimicking the sensitization mechanism postulated in humans. The in vitro exposure to all polymeric glycoconjugates (5-10-20-50-100 µg/mL) mainly inhibited anti-αGal IgE and IgM isotypes, with a lower inhibition effect on the IgA and IgG, respectively. We demonstrated a differential anti-αGal isotype inhibition as a function of the length of the poly-L-lysine and the number of αGal residues exposed in the glycoconjugates. These results defined a minimum of 27 αGal residues to inhibit most of the induced anti-αGal IgE in vitro. Furthermore, the αGal-glycoconjugate DP1000-RA0118 (10 mg/kg sc.) showed a high capacity to remove the anti-αGal IgE antibodies (≥75% on average) induced in GalT-KO mice, together with similar inhibition for circulating anti-αGal IgG and IgM. Our study suggests the potential clinical use of poly-L-lysine-based αGal-glycoconjugates for treating allergic disorders mediated by anti-αGal IgE antibodies.
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Affiliation(s)
- Sara Olivera-Ardid
- RemAb Therapeutics, Mòdul de Recerca B, UAB Bellaterra, Barcelona, Spain
| | - Daniel Bello-Gil
- RemAb Therapeutics, Mòdul de Recerca B, UAB Bellaterra, Barcelona, Spain
| | - Alexander Tuzikov
- Department of Chemical Biology of Glycans and Lipids, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry Russian Academy of Sciences (RAS), Moscow, Russia
| | - Ricardo N. Araujo
- Laboratório de Artrópodes Hematófagos, Departamento de Parasitologia, ICB/UFMG, Belo Horizonte, Brazil
| | - Yara Ferrero-Alves
- RemAb Therapeutics, Mòdul de Recerca B, UAB Bellaterra, Barcelona, Spain
| | - Blanca Esther García Figueroa
- MEGA: Asthma Inception and Progression Mechanisms, Complejo Hospitalario de Navarra (CHN), Pamplona, Spain
- Instituto de investigación sanitaria de Navarra (IdiSNA), Pamplona, Spain
- ARADyAL Research Network, Instituto de Salud Carlos III (ISCIII), Madrid, Spain
| | - Moisés Labrador-Horrillo
- ARADyAL Research Network, Instituto de Salud Carlos III (ISCIII), Madrid, Spain
- Department of Medicine, Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- Allergy Section, Internal Medicine Department, Hospital Universitari Vall d’Hebron (HUVH), Barcelona, Spain
- Immunomediated Diseases and Innovative Therapies, Vall d’Hebron Institut de Recerca (VHIR), Barcelona, Spain
| | - Ana L. García-Pérez
- Departamento de Sanidad Animal, Instituto Vasco de Investigación de Desarrollo Agrario (NEIKER), Derio, Spain
| | - Nicolai Bovin
- Department of Chemical Biology of Glycans and Lipids, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry Russian Academy of Sciences (RAS), Moscow, Russia
| | - Rafael Mañez
- RemAb Therapeutics, Mòdul de Recerca B, UAB Bellaterra, Barcelona, Spain
- Hospital Universitari de Bellvitge, Servicio de Medicina Intensiva, Hospitalet de Llobregat, Barcelona, Spain
- Instituto de Investigación Biomédica de Bellvitge (IDIBELL), Grupo Inmunidad Innata y Patología del Paciente Crítico, Hospitalet de Llobregat, Barcelona, Spain
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Singh AK, Goerlich CE, Shah AM, Zhang T, Tatarov I, Ayares D, Horvath KA, Mohiuddin MM. Cardiac Xenotransplantation: Progress in Preclinical Models and Prospects for Clinical Translation. Transpl Int 2022; 35:10171. [PMID: 35401039 PMCID: PMC8985160 DOI: 10.3389/ti.2022.10171] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 01/11/2022] [Indexed: 12/02/2022]
Abstract
Survival of pig cardiac xenografts in a non-human primate (NHP) model has improved significantly over the last 4 years with the introduction of costimulation blockade based immunosuppression (IS) and genetically engineered (GE) pig donors. The longest survival of a cardiac xenograft in the heterotopic (HHTx) position was almost 3 years and only rejected when IS was stopped. Recent reports of cardiac xenograft survival in a life-sustaining orthotopic (OHTx) position for 6 months is a significant step forward. Despite these achievements, there are still several barriers to the clinical success of xenotransplantation (XTx). This includes the possible transmission of porcine pathogens with pig donors and continued xenograft growth after XTx. Both these concerns, and issues with additional incompatibilities, have been addressed recently with the genetic modification of pigs. This review discusses the spectrum of issues related to cardiac xenotransplantation, recent progress in preclinical models, and its feasibility for clinical translation.
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Affiliation(s)
- Avneesh K. Singh
- Department of Surgery, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Corbin E. Goerlich
- Department of Surgery, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Aakash M. Shah
- Department of Surgery, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Tianshu Zhang
- Department of Surgery, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Ivan Tatarov
- Department of Surgery, School of Medicine, University of Maryland, Baltimore, MD, United States
| | | | - Keith A. Horvath
- National Heart, Lung, and Blood Institute, National Institute of Health, Bethesda, MD, United States
| | - Muhammad M. Mohiuddin
- Department of Surgery, School of Medicine, University of Maryland, Baltimore, MD, United States
- *Correspondence: Muhammad M. Mohiuddin,
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Siems C, Huddleston S, John R. A Brief History of Xenotransplantation. Ann Thorac Surg 2022; 113:706-710. [DOI: 10.1016/j.athoracsur.2022.01.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 01/19/2022] [Indexed: 11/25/2022]
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Cooper DKC, Ezzelarab MB, Hara H, Iwase H, Lee W, Wijkstrom M, Bottino R. The pathobiology of pig-to-primate xenotransplantation: a historical review. Xenotransplantation 2016; 23:83-105. [PMID: 26813438 DOI: 10.1111/xen.12219] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 12/22/2015] [Indexed: 12/16/2022]
Abstract
The immunologic barriers to successful xenotransplantation are related to the presence of natural anti-pig antibodies in humans and non-human primates that bind to antigens expressed on the transplanted pig organ (the most important of which is galactose-α1,3-galactose [Gal]), and activate the complement cascade, which results in rapid destruction of the graft, a process known as hyperacute rejection. High levels of elicited anti-pig IgG may develop if the adaptive immune response is not prevented by adequate immunosuppressive therapy, resulting in activation and injury of the vascular endothelium. The transplantation of organs and cells from pigs that do not express the important Gal antigen (α1,3-galactosyltransferase gene-knockout [GTKO] pigs) and express one or more human complement-regulatory proteins (hCRP, e.g., CD46, CD55), when combined with an effective costimulation blockade-based immunosuppressive regimen, prevents early antibody-mediated and cellular rejection. However, low levels of anti-non-Gal antibody and innate immune cells and/or platelets may initiate the development of a thrombotic microangiopathy in the graft that may be associated with a consumptive coagulopathy in the recipient. This pathogenic process is accentuated by the dysregulation of the coagulation-anticoagulation systems between pigs and primates. The expression in GTKO/hCRP pigs of a human coagulation-regulatory protein, for example, thrombomodulin, is increasingly being associated with prolonged pig graft survival in non-human primates. Initial clinical trials of islet and corneal xenotransplantation are already underway, and trials of pig kidney or heart transplantation are anticipated within the next few years.
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Affiliation(s)
- David K C Cooper
- The Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - Mohamed B Ezzelarab
- The Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - Hidetaka Hara
- The Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - Hayato Iwase
- The Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - Whayoung Lee
- The Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - Martin Wijkstrom
- The Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - Rita Bottino
- Institute for Cellular Therapeutics, Allegheny-Singer Research Institute, Pittsburgh, PA, USA
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6
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Azimzadeh AM, Byrne GW, Ezzelarab M, Welty E, Braileanu G, Cheng X, Robson SC, McGregor CGA, Cooper DKC, Pierson RN. Development of a consensus protocol to quantify primate anti-non-Gal xenoreactive antibodies using pig aortic endothelial cells. Xenotransplantation 2014; 21:555-66. [PMID: 25176173 DOI: 10.1111/xen.12125] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 05/30/2014] [Indexed: 01/05/2023]
Abstract
BACKGROUND Scientists working in the field of xenotransplantation do not employ a uniform method to measure and report natural and induced antibody responses to non-Galα(1,3)Gal (non-Gal) epitopes. Such humoral responses are thought to be particularly pathogenic after transplantation of vascularized GalTKO pig organs and having a more uniform assay and reporting format would greatly facilitate comparisons between laboratories. METHODS Flow cytometry allows examination of antibody reactivity to intact antigens in their natural location and conformation on cell membranes. We have established a simple and reproducible flow cytometric assay to detect antibodies specific for non-Gal pig antigens using primary porcine aortic endothelial cells (pAECs) and cell culture-adapted pAEC cell lines generated from wild type and α1,3galactosyl transferase knockout (GalTKO) swine. RESULTS The consensus protocol we propose here is based on procedures routinely used in four xenotransplantation centers and was independently evaluated at three sites using shared cells and serum samples. Our observation support use of the cell culture-adapted GalTKO pAEC KO:15502 cells as a routine method to determine the reactivity of anti-non-Gal antibodies in human and baboon serum. CONCLUSIONS We have developed an assay that allows the detection of natural and induced non-Gal xenoreactive antibodies present in human or baboon serum in a reliable and consistent manner. This consensus assay and format for reporting the data should be accessible to laboratories and will be useful for assessing experimental results between multiple research centers. Adopting this assay and format for reporting the data should facilitate the detection, monitoring, and detailed characterization of non-Gal antibody responses.
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Affiliation(s)
- Agnes M Azimzadeh
- Division of Cardiac Surgery, University of Maryland and VAMC Baltimore, Baltimore, MD, USA
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Cowan PJ, Cooper DKC, d'Apice AJF. Kidney xenotransplantation. Kidney Int 2014; 85:265-75. [PMID: 24088952 PMCID: PMC3946635 DOI: 10.1038/ki.2013.381] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 07/12/2013] [Accepted: 07/17/2013] [Indexed: 12/14/2022]
Abstract
Xenotransplantation using pigs as donors offers the possibility of eliminating the chronic shortage of donor kidneys, but there are several obstacles to be overcome before this goal can be achieved. Preclinical studies have shown that, while porcine renal xenografts are broadly compatible physiologically, they provoke a complex rejection process involving preformed and elicited antibodies, heightened innate immune cell reactivity, dysregulated coagulation, and a strong T cell-mediated adaptive response. Furthermore, the susceptibility of the xenograft to proinflammatory and procoagulant stimuli is probably increased by cross-species molecular defects in regulatory pathways. To balance these disadvantages, xenotransplantation has at its disposal a unique tool to address particular rejection mechanisms and incompatibilities: genetic modification of the donor. This review focuses on the pathophysiology of porcine renal xenograft rejection, and on the significant genetic, pharmacological, and technical progress that has been made to prolong xenograft survival.
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Affiliation(s)
- Peter J Cowan
- 1] Immunology Research Centre, St Vincent's Hospital, Melbourne, Victoria, Australia [2] Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia
| | - David K C Cooper
- Thomas E. Starzl Transplantation Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
| | - Anthony J F d'Apice
- 1] Immunology Research Centre, St Vincent's Hospital, Melbourne, Victoria, Australia [2] Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia
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Kim K, Schuetz C, Elias N, Veillette GR, Wamala I, Varma M, Smith RN, Robson SC, Cosimi AB, Sachs DH, Hertl M. Up to 9-day survival and control of thrombocytopenia following alpha1,3-galactosyl transferase knockout swine liver xenotransplantation in baboons. Xenotransplantation 2013; 19:256-64. [PMID: 22909139 DOI: 10.1111/j.1399-3089.2012.00717.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND With standard miniature swine donors, survivals of only 3 days have been achieved in primate liver-transplant recipients. The recent production of alpha1,3-galactosyl transferase knockout (GalT-KO) miniature swine has made it possible to evaluate xenotransplantation of pig organs in clinically relevant pig-to-non-human primate models in the absence of the effects of natural anti-Gal antibodies. We are reporting our results using GalT-KO liver grafts. METHODS We performed GalT-KO liver transplants in baboons using an immunosuppressive regimen previously used by our group in xeno heart and kidney transplantation. Post-operative liver function was assessed by laboratory function tests, coagulation parameters and histology. RESULTS In two hepatectomized recipients of GalT-KO grafts, post-transplant liver function returned rapidly to normal. Over the first few days, the synthetic products of the donor swine graft appeared to replace those of the baboon. The first recipient survived for 6 days and showed no histopathological evidence of rejection at the time of death from uncontrolled bleeding, probably caused by transfusion-refractory thrombocytopenia. Amicar treatment of the second and third recipients led to maintenance of platelet counts of over 40 000 per μl throughout their 9- and 8-day survivals, which represents the longest reported survival of pig-to-primate liver transplants to date. Both of the last two animals nevertheless succumbed to bleeding and enterococcal infection, without evidence of rejection. CONCLUSIONS These observations suggest that thrombocytopenia after liver xenotransplantation may be overcome by Amicar therapy. The coagulopathy and sepsis that nevertheless occurred suggest that additional causes of coagulation disturbance must be addressed, along with better prevention of infection, to achieve long-term survival.
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Affiliation(s)
- Karen Kim
- Department of Surgery, Massachusetts General Hospital, Boston, MA, USA
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9
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Abstract
Anti-non gal antibodies are produced in xenograft recipients against multiple xenogeneic antigens. Studies in monkeys transplanted with pig organs lacking α-gal epitopes have suggested that anti-non gal antibodies mediate acute and chronic rejection of xenografts. This overview describes studies of these antibodies in patients who received xenografts and includes (1) an ovarian carcinoma patient receiving three intraperitoneal infusions of mouse fibroblasts in a gene therapy study, (2) orthopedic patients with torn anterior cruciate ligament replaced by a ligament made of pig patellar tendon, and (3) diabetic patients receiving fetal pig islet cell clusters xenograft together with a kidney allograft. Anti-non gal antibodies were found to be continuously produced as long as the xenograft was present in the recipient and were directed against a large number of pig proteins. Monitoring the immune response in the recipient of mouse fibroblasts indicated that the production of anti-non gal antibodies is much slower than that of the anti-Gal antibody, suggesting that they are generated by multiple B-cell clones, each initially comprising relatively few cells. Potent immunosuppression to prevent allograft rejection does not fully inhibit the production of anti-non gal antibodies. Much of this antibody response seems to be due to the differences in amino acid sequences between pig and human orthologous proteins as a result of evolutionary mutations. Overcoming the anti-non gal antibody barrier will require immunosuppressive agents that preferentially inhibit this immune response while maintaining protection against pathogens, or alternatively development of methods for induction of immune tolerance to xenogeneic pig antigens.
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10
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Mohiuddin MM, Corcoran PC, Singh AK, Azimzadeh A, Hoyt RF, Thomas ML, Eckhaus MA, Seavey C, Ayares D, Pierson RN, Horvath KA. B-cell depletion extends the survival of GTKO.hCD46Tg pig heart xenografts in baboons for up to 8 months. Am J Transplant 2012; 12:763-71. [PMID: 22070772 PMCID: PMC4182960 DOI: 10.1111/j.1600-6143.2011.03846.x] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Xenotransplantation of genetically modified pig organs offers great potential to address the shortage of human organs for allotransplantation. Rejection in Gal knockout (GTKO) pigs due to elicited non-Gal antibody response required further genetic modifications of donor pigs and better control of the B-cell response to xenoantigens. We report significant prolongation of heterotopic alpha Galactosyl transferase "knock-out" and human CD46 transgenic (GTKO.hCD46Tg) pig cardiac xenografts survival in specific pathogen free baboons. Peritransplant B-cell depletion using 4 weekly doses of anti-CD20 antibody in the context of an established ATG, anti-CD154 and MMF-based immunosuppressive regimen prolonged GTKO.hCD46Tg graft survival for up to 236 days (n = 9, median survival 71 days and mean survival 94 days). B-cell depletion persisted for over 2 months, and elicited anti-non-Gal antibody production remained suppressed for the duration of graft follow-up. This result identifies a critical role for B cells in the mechanisms of elicited anti-non-Gal antibody and delayed xenograft rejection. Model-related morbidity due to variety of causes was seen in these experiments, suggesting that further therapeutic interventions, including candidate genetic modifications of donor pigs, may be necessary to reduce late morbidity in this model to a clinically manageable level.
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Affiliation(s)
- MM Mohiuddin
- Cardiothoracic Surgery Research Program, NHLBI, NIH, Bethesda, MD
| | - PC Corcoran
- Cardiothoracic Surgery Research Program, NHLBI, NIH, Bethesda, MD
| | - AK Singh
- Cardiothoracic Surgery Research Program, NHLBI, NIH, Bethesda, MD
| | - A Azimzadeh
- University of Maryland Medical Center, Baltimore, MD
| | - RF Hoyt
- LAMS, NHLBI, NIH, Bethesda, MD
| | | | | | - C Seavey
- Cardiothoracic Surgery Research Program, NHLBI, NIH, Bethesda, MD
| | | | - RN Pierson
- University of Maryland Medical Center, Baltimore, MD
| | - KA Horvath
- Cardiothoracic Surgery Research Program, NHLBI, NIH, Bethesda, MD
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Abstract
BACKGROUND This study compares the pathologic condition of delayed xenograft rejection in Gal-positive and Gal-knockout cardiac xenografts after pig-to-baboon heterotopic cardiac xenotransplantation when the induced anti-Gal antibody response is unregulated, blocked, or absent. METHODS Baboon recipients of Gal-positive, CD46 pig hearts were treated with an αGal polymer (group 1; n=11) or Gal-specific immunoapheresis (group 2; n=8) to block anti-Gal antibody. Gal-knockout cardiac xenografts recipients (group 3; n=5) received no anti-Gal therapy. Perioperative and interim biopsies were examined and antibody responses were determined. RESULTS No hyperacute rejection was seen and histologic findings were similar across the groups. All groups showed vascular antibody deposition in perioperative and interim biopsies and in explant samples. A prominent antibody response was detected only in group 2. Complement activation was evident by C3d deposition but deposition of C5b and C5b-9 was limited. Earliest evidence of myocardial injury was myocyte vacuolization in the absence of microvascular thrombosis or coagulative necrosis that developed later. Histology of explanted hearts exhibited mainly microvascular thrombosis and coagulative necrosis with little evidence of interstitial hemorrhage or edema. CONCLUSIONS The histology of rejection seemed independent of the anti-Gal or non-Gal immune response. Myocyte vacuolization seems to be an early feature of delayed xenograft rejection presaging more classic pathologic features.
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Byrne GW, Du Z, Sun Z, Asmann YW, McGregor CGA. Changes in cardiac gene expression after pig-to-primate orthotopic xenotransplantation. Xenotransplantation 2011; 18:14-27. [PMID: 21342284 PMCID: PMC10022692 DOI: 10.1111/j.1399-3089.2010.00620.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Gene profiling methods have been widely useful for delineating changes in gene expression as an approach for gaining insight into the mechanism of rejection or disease pathology. Herein, we use gene profiling to compare changes in gene expression associated with different orthotopic cardiac xenotransplantation (OCXTx) outcomes and to identify potential effects of OCXTx on cardiac physiology. METHODS We used the Affymetrix GeneChip Porcine Genomic Array to characterize three types of orthotopic cardiac xenograft outcomes: 1) rejected hearts that underwent delayed xenograft rejection (DXR); 2) survivor hearts in which the xenograft was not rejected and recipient death was due to model complications; and 3) hearts which failed to provide sufficient circulatory support within the first 48 h of transplant, termed "perioperative cardiac xenograft dysfunction" (PCXD). Gene expression in each group was compared to control, not transplanted pig hearts, and changes in gene expression > 3 standard deviations (±3SD) from the control samples were analyzed. A bioinformatics analysis was used to identify enrichments in genes involved in Kyoto Encyclopedia of Genes and Genomes pathways and gene ontogeny molecular functions. Changes in gene expression were confirmed by quantitative RT-PCR. RESULTS The ±3SD data set contained 260 probes, which minimally exhibited a 3.5-fold change in gene expression compared to control pig hearts. Hierarchical cluster analysis segregated rejected, survivor and PCXD samples, indicating a unique change in gene expression for each group. All transplant outcomes shared a set of 21 probes with similarly altered expression, which were indicative of ongoing myocardial inflammation and injury. Some outcome-specific changes in gene expression were identified. Bioinformatics analysis detected an enrichment of genes involved in protein, carbohydrate and branched amino acid metabolism, extracellular matrix-receptor interactions, focal adhesion, and cell communication. CONCLUSIONS This is the first genome wide assessment of changes in cardiac gene expression after OCXTx. Hierarchical cluster analysis indicates a unique gene profile for each transplant outcome but additional samples will be required to define the unique classifier probe sets. Quantitative RT-PCR confirmed that all transplants exhibited strong evidence of ongoing inflammation and myocardial injury consistent with the effects of cytokines and vascular antibody-mediated inflammation. This was also consistent with bioinformatic analysis suggesting ongoing tissue repair in survivor and PCXD samples. Bioinformatics analysis suggests for the first time that xenotransplantation may affect cardiac metabolism in survivor and rejected samples. This study highlights the potential utility of molecular analysis to monitor xenograft function, to identify new molecular markers and to understand processes, which may contribute to DXR.
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Affiliation(s)
- Guerard W Byrne
- Department of Medicine, University College London, London, UK.
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13
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Abstract
This work sought to summarize the main issues of the last decade in the field of clinical islet transplantation. Ten years ago in Edmonton, a new protocol initiated for islet transplantation brought a breakthrough to the field. The earlier, rather poor results were in a sharp contrast to the first published results of 100% insulin freedom at 1 year. However, later it became clear that the promising initial results decline with time; at around 5 years, only about 10% of the patients maintain freedom from external insulin. Despite that fact, a milestone was set and intensive research started worldwide. New hopes were raised for patients. Modifications of the original protocol have been implemented to improve clinical results; however, islet transplantation remains an experimental procedure to date.
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Affiliation(s)
- R M Langer
- Department of Transplantation and Surgery, Semmelweis University, Budapest, Hungary.
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14
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Tahara H, Ide K, Basnet NB, Tanaka Y, Matsuda H, Takematsu H, Kozutsumi Y, Ohdan H. Immunological Property of Antibodies against N-Glycolylneuraminic Acid Epitopes in Cytidine Monophospho–N-Acetylneuraminic Acid Hydroxylase-Deficient Mice. THE JOURNAL OF IMMUNOLOGY 2010; 184:3269-75. [DOI: 10.4049/jimmunol.0902857] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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15
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Pierson RN, Dorling A, Ayares D, Rees MA, Seebach JD, Fishman JA, Hering BJ, Cooper DKC. Current status of xenotransplantation and prospects for clinical application. Xenotransplantation 2009; 16:263-80. [PMID: 19796067 PMCID: PMC2866107 DOI: 10.1111/j.1399-3089.2009.00534.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Xenotransplantation is one promising approach to bridge the gap between available human cells, tissues, and organs and the needs of patients with diabetes or end-stage organ failure. Based on recent progress using genetically modified source pigs, improving results with conventional and experimental immunosuppression, and expanded understanding of residual physiologic hurdles, xenotransplantation appears likely to be evaluated in clinical trials in the near future for some select applications. This review offers a comprehensive overview of known mechanisms of xenograft injury, a contemporary assessment of preclinical progress and residual barriers, and our opinions regarding where breakthroughs are likely to occur.
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Affiliation(s)
- Richard N Pierson
- Division of Cardiac Surgery, Department of Surgery, University of Maryland, Baltimore VAMC, Baltimore, MD 21201, USA.
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Habiro K, Sykes M, Yang YG. Induction of human T-cell tolerance to pig xenoantigens via thymus transplantation in mice with an established human immune system. Am J Transplant 2009; 9:1324-9. [PMID: 19459808 PMCID: PMC2752337 DOI: 10.1111/j.1600-6143.2009.02646.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Thymus xenotransplantation has been shown to induce tolerance to porcine xenografts in mice and to permit survival of alpha1,3Gal-transferase knockout porcine kidney xenografts for months in nonhuman primates. We evaluated the ability of porcine thymus xenotransplantation to induce human T-cell tolerance using a humanized mouse (hu-mouse) model, where a human immune system is preestablished by implantation of fetal human thymus tissue under the kidney capsule and intravenous injection of CD34(+) hematopoietic stem/progenitor cells. Human T-cell depletion with an anti-CD2 mAb following surgical removal of human thymic grafts prevented the initial rejection of porcine thymic xenografts in hu-mice. In these hu-mice, porcine thymic grafts were capable of supporting human thymopoiesis and T-cell development, and inducing human T-cell tolerance to porcine xenoantigens. Human T cells from these mice responded strongly to third-party pig, but not to the thymic donor swine leukocyte antigen (SLA)-matched pig stimulators in a mixed lymphocyte reaction (MLR) assay. Anti-pig xenoreactive antibodies declined in these hu-mice, whereas antibody levels increased in nontolerant animals that rejected porcine thymus grafts. These data show that porcine thymic xenotransplantation can induce donor-specific tolerance in immunocompetent hu-mice, supporting this approach for tolerance induction in clinical xenotransplantation.
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Affiliation(s)
- Katsuyoshi Habiro
- Transplantation Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02129
| | - Megan Sykes
- Transplantation Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02129
| | - Yong-Guang Yang
- Transplantation Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02129, Corresponding Author: Yong-Guang Yang, MD, PhD, Transplantation Biology Research Center, Massachusetts General Hospital, Harvard Medical School, MGH-East, Building 149-5102, 13 street, Boston, MA 02129, USA, Tel: 617/726-6959; Fax: 617/724-9892; E-mail:
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Byrne GW, Stalboerger PG, Davila E, Heppelmann CJ, Gazi MH, McGregor HCJ, LaBreche PT, Davies WR, Rao VP, Oi K, Tazelaar HD, Logan JS, McGregor CGA. Proteomic identification of non-Gal antibody targets after pig-to-primate cardiac xenotransplantation. Xenotransplantation 2009; 15:268-76. [PMID: 18957049 DOI: 10.1111/j.1399-3089.2008.00480.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Experience with non-antigenic galactose alpha1,3 galactose (alphaGal) polymers and development of alphaGal deficient pigs has reduced or eliminated the significance of this antigen in xenograft rejection. Despite these advances, delayed xenograft rejection (DXR) continues to occur most likely due to antibody responses to non-Gal endothelial cell (EC) antigens. METHODS To gauge the diversity of the non-Gal antibody response we used antibody derived from CD46 transgenic heterotopic cardiac xenografts performed without T-cell immunosuppression, Group A (n = 4) and Gal knockout (GT-KO) heart transplants under tacrolimus and sirolimus immunosuppression, Group B (n = 8). Non-Gal antibody was measured by flow cytometry and by western blots using GT-KO EC membrane antigens. A nanoLC/MS/MS analysis of proteins recovered from 2D gels was used to identify target antigens. RESULTS Group A recipients exhibited a mixed cellular and humoral rejection. Group B recipients mainly exhibited classical DXR. Western blot analysis showed a non-Gal antibody response induced by GT+ and GT-KO hearts to an overlapping set of pig aortic EC membrane antigens. Proteomic analysis identified 14 potential target antigens but failed to define several immunodominant targets. CONCLUSIONS These experiments indicate that the non-Gal antibody response is directed to a number of stress response and inflammation related pig EC antigens and a few undefined targets. Further analysis of these antibody specificities using alternative methods is required to more fully define the repertoire of non-Gal antibody responses.
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Affiliation(s)
- Guerard W Byrne
- Department of Surgery, Mayo Clinic, Rochester, MN 55905, USA.
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Haspot F, Bardwell PD, Zhao G, Sykes M. High antigen levels do not preclude B-cell tolerance induction to alpha1,3-Gal via mixed chimerism. Xenotransplantation 2009; 15:313-20. [PMID: 19134161 DOI: 10.1111/j.1399-3089.2008.00487.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Studies of bone marrow transplantation (BMT) from wild-type mice or rats to alpha1,3-galactosyltransferase (GalT) knockout mice have demonstrated that induction of mixed chimerism tolerizes not only T cells, but also natural antibody-producing B cells, even across xenogeneic barriers. Given that rodent cells express lower levels of the alphaGal epitope than the more clinically relevant porcine species, the consequences of exposure to cells expressing high levels of alphaGal on the ability to induce B-cell tolerance are unknown. METHODS The effects on chimerism and anti-alphaGal B-cell tolerance of an i.p. injection of 10(9) porcine RBC were evaluated in GalT knockout mice receiving wild-type allogeneic BMT after non-myeloablative conditioning with T-cell depleting monoclonal antibodies, thymic irradiation, and low-dose total body irradiation. RESULTS Achievement of mixed chimerism and tolerance of anti-alphaGal-producing B cells was not affected by exposure to high-density alphaGal at the time of BMT. The absence of induced anti-alphaGal or anti-pig antibody responses in conditioned control mice suggested that the B-cell xeno-response to pig is T-cell-dependent. CONCLUSION High alphaGal density on pig cells might not preclude the ability to achieve tolerance of pre-existing alphaGal-reactive human B cells via induction of mixed chimerism. This strategy has the potential to induce B-cell tolerance to non-alphaGal epitopes, against which natural antibodies have been found in the sera of healthy humans.
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Affiliation(s)
- Fabienne Haspot
- Transplantation Biology Research Center, Massachusetts General Hospital, Harvard Medical School, 149-5102 13th Street, Boston, MA 02129, USA
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19
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Ichii H, Ricordi C. Current status of islet cell transplantation. ACTA ACUST UNITED AC 2008; 16:101-12. [PMID: 19110649 DOI: 10.1007/s00534-008-0021-2] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2008] [Accepted: 07/15/2008] [Indexed: 02/08/2023]
Abstract
Despite substantial advances in islet isolation methods and immunosuppressive protocol, pancreatic islet cell transplantation remains an experimental procedure currently limited to the most severe cases of type 1 diabetes mellitus. The objectives of this treatment are to prevent severe hypoglycemic episodes in patients with hypoglycemia unawareness and to achieve a more physiological metabolic control. Insulin independence and long term-graft function with improvement of quality of life have been obtained in several international islet transplant centers. However, experimental trials of islet transplantation clearly highlighted several obstacles that remain to be overcome before the procedure could be proposed to a much larger patient population. This review provides a brief historical perspective of islet transplantation, islet isolation techniques, the transplant procedure, immunosuppressive therapy, and outlines current challenges and future directions in clinical islet transplantation.
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Affiliation(s)
- Hirohito Ichii
- Cell Transplant Center, Diabetes Research Institute, University of Miami Leonard M Miller School of Medicine, Miami, FL 33136, USA.
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20
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Dehoux JP, Gianello P. Accommodation and antibodies. Transpl Immunol 2008; 21:106-10. [PMID: 18973811 DOI: 10.1016/j.trim.2008.10.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Accepted: 10/09/2008] [Indexed: 12/26/2022]
Abstract
Accommodation refers to the condition in which an organ transplant functions normally by acquiring resistance to immune-mediated injury (especially), despite the presence of anti-transplant antibodies in the recipient. This status is associated with several modifications in the recipient as well as in the graft, such as previous depletion of anti-graft antibodies and their slow return once the graft is placed; expression of several protective genes in the graft; a Th2 immune response in the recipient; and inhibition of the membrane attack complex of complement.
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Affiliation(s)
- Jean-Paul Dehoux
- Laboratory of Experimental Surgery, Faculté de médecine, Université catholique de Louvain, Brussels, Belgium
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Hall V. Porcine Embryonic Stem Cells: A Possible Source for Cell Replacement Therapy. ACTA ACUST UNITED AC 2008; 4:275-82. [DOI: 10.1007/s12015-008-9040-2] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Ricci D, Tazelaar HD, Miyagi N, Rao VP, Pedersen RA, Kremers WK, Byrne GW, McGregor CGA. The utility of right ventricular endomyocardial biopsy for the diagnosis of xenograft rejection after CD46 pig-to-baboon cardiac transplantation. J Heart Lung Transplant 2007; 26:1025-32. [PMID: 17919623 DOI: 10.1016/j.healun.2007.07.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Revised: 07/05/2007] [Accepted: 07/15/2007] [Indexed: 11/28/2022] Open
Abstract
INTRODUCTION Endomyocardial biopsy is the standard means of establishing cardiac allograft rejection diagnosis. The efficacy of this procedure in xenotransplantation has not been determined. In this study we compare the histology of right ventricular endomyocardial biopsy specimens with the corresponding full cross sections of explanted right ventricle (RV). We also compare RV with the related left ventricle (LV) cross sections. METHODS Heterotopic CD46 pig-to-baboon cardiac xenotransplants (n = 64) were studied. RV endomyocardial biopsy specimens were taken at cardiac explant by using a standard bioptome (n = 24) or by sharp dissection (n = 40). Hematoxylin and eosin stained sections of RV and LV cross-section and RV endomyocardial biopsy specimens were compared in a blinded fashion. Characteristics of delayed xenograft rejection and a global assessment of ischemia were scored from 0 to 4 according to the percentage of myocardium involved (0, 0%; 1, 1%-25%; 2, 26%-50%; 3, 51%-75%; and 4, 76%-100%). RESULTS Median graft survival was 30 days (range, 3-137 days). Linear regression analysis of histology scores demonstrated that specimens from both bioptome and sharp dissection equally represented the histology of the RV cross section. Global ischemic injury was strongly correlated between RV and RV endomyocardial biopsy (R(2) = 0.84) and between RV and LV cross sections (R(2) = 0.84). Individual characteristics of delayed xenograft rejection showed no significant variation between RV and RV endomyocardial biopsy or between RV and LV (p < 0.05). CONCLUSIONS These results indicate that delayed xenograft rejection is a widespread process involving both right and left ventricles similarly. This study shows that histologic assessment of RV endomyocardial biopsy specimens is an effective method for the monitoring of delayed xenograft rejection after cardiac xenotransplantation.
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Affiliation(s)
- Davide Ricci
- Mayo Clinic William J von Liebig Transplant Center, Mayo Clinic, Rochester, Minnesota 55905, USA
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Milland J, Yuriev E, Xing PX, McKenzie IFC, Ramsland PA, Sandrin MS. Carbohydrate residues downstream of the terminal Galalpha(1,3)Gal epitope modulate the specificity of xenoreactive antibodies. Immunol Cell Biol 2007; 85:623-32. [PMID: 17724458 DOI: 10.1038/sj.icb.7100111] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Carbohydrates are involved in many immunological responses including the rejection of incompatible blood, tissues and organs. Carbohydrate antigens with Galalpha(1,3)Gal epitopes are recognized by natural antibodies in humans and pose a major barrier for pig-to-human xenotransplantation. Genetically modified pigs have been established that have no functional alpha1,3-galactosyltransferase (alpha1,3GT), which transfers alphaGal to N-acetyllactosamine (LacNAc) type oligosaccharides. However, a low level of Galalpha(1,3)Gal is still expressed in alpha1,3GT knockout animals in the form of a lipid, isoglobotrihexosylceramide (iGb3), which is produced by iGb3 synthase on lactose (Lac) type core structures. Here, we define the reactivity of a series of monoclonal antibodies (mAb) generated in alpha1,3GT-/- mice immunized with rabbit red blood cells (RbRBC), as a rich source of lipid-linked antigens. Interestingly, one mAb (15.101) binds weakly to synthetic and cell surface-expressed Galalpha(1,3)Gal on LacNAc, but strongly to versions of the antigen on Lac cores, including iGb3. Three-dimensional models suggest that the terminal alpha-linked Gal binds tightly into the antibody-binding cavity. Furthermore, antibody interactions were predicted with the second and third monosaccharide units. Collectively, our findings suggest that although the terminal carbohydrate residues confer most of the binding affinity, the fine specificity is determined by subsequent residues in the oligosaccharide.
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Affiliation(s)
- Julie Milland
- Department of Surgery (Austin Health), University of Melbourne, Heidelberg, Victoria, Australia
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Zhu X, Dor FJMF, Cooper DKC. Pig-to-non-human primate heart transplantation: immunologic progress over 20 years. J Heart Lung Transplant 2007; 26:210-8. [PMID: 17346622 DOI: 10.1016/j.healun.2006.12.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2006] [Revised: 11/27/2006] [Accepted: 12/12/2006] [Indexed: 11/20/2022] Open
Abstract
The major developments in pig-to-non-human primate heart xenotransplantation during the past 20 years are summarized, largely through the experience of one investigator. Genetic modifications to organ-source pigs have been important steps in increasing heart xenograft survival from a few minutes in 1986 to 2 to 6 months in 2005.
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Affiliation(s)
- Xiaocheng Zhu
- Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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Using α1,3-galactosyltransferase gene-knockout pig organs in nonhuman primates. Curr Opin Organ Transplant 2007. [DOI: 10.1097/mot.0b013e3280146495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Kearns-Jonker M, Barteneva N, Mencel R, Hussain N, Shulkin I, Xu A, Yew M, Cramer DV. Use of molecular modeling and site-directed mutagenesis to define the structural basis for the immune response to carbohydrate xenoantigens. BMC Immunol 2007; 8:3. [PMID: 17352819 PMCID: PMC1851715 DOI: 10.1186/1471-2172-8-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2006] [Accepted: 03/12/2007] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Natural antibodies directed at carbohydrates reject porcine xenografts. They are initially expressed in germline configuration and are encoded by a small number of structurally-related germline progenitors. The transplantation of genetically-modified pig organs prevents hyperacute rejection, but delayed graft rejection still occurs, partly due to humoral responses. IgVH genes encoding induced xenoantibodies are predominantly, not exclusively, derived from germline progenitors in the VH3 family. We have previously identified the immunoglobulin heavy chain genes encoding VH3 xenoantibodies in patients and primates. In this manuscript, we complete the structural analysis of induced xenoantibodies by identifying the IgVH genes encoding the small proportion of VH4 xenoantibodies and the germline progenitors encoding xenoantibody light chains. This information has been used to define the xenoantibody/carbohydrate binding site using computer-simulated modeling. RESULTS The VH4-59 gene encodes antibodies in the VH4 family that are induced in human patients mounting active xenoantibody responses. The light chain of xenoantibodies is encoded by DPK5 and HSIGKV134. The structural information obtained by sequencing analysis was used to create computer-simulated models. Key contact sites for xenoantibody/carbohydrate interaction for VH3 family xenoantibodies include amino acids in sites 31, 33, 50, 57, 58 and the CDR3 region of the IgVH gene. Site-directed mutagenesis indicates that mutations in predicted contact sites alter binding to carbohydrate xenoantigens. Computer-simulated modeling suggests that the CDR3 region directly influences binding. CONCLUSION Xenoantibodies induced during early and delayed xenograft responses are predominantly encoded by genes in the VH3 family, with a small proportion encoded by VH4 germline progenitors. This restricted group can be identified by the unique canonical structure of the light chain, heavy chain and CDR3. Computer-simulated models depict this structure with accuracy, as confirmed by site-directed mutagenesis. Computer-simulated drug design using computer-simulated models may now be applied to develop new drugs that may enhance the survival of xenografted organs.
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Affiliation(s)
- Mary Kearns-Jonker
- Department of Cardiothoracic Surgery, Saban Research Institute of the Children's Hospital of Los Angeles, University of Southern California Keck School of Medicine, 4650 Sunset Blvd, Mailstop #137, Los Angeles, CA 90027 USA
| | - Natasha Barteneva
- Department of Cardiothoracic Surgery, Saban Research Institute of the Children's Hospital of Los Angeles, University of Southern California Keck School of Medicine, 4650 Sunset Blvd, Mailstop #137, Los Angeles, CA 90027 USA
| | - Robert Mencel
- Department of Cardiothoracic Surgery, Saban Research Institute of the Children's Hospital of Los Angeles, University of Southern California Keck School of Medicine, 4650 Sunset Blvd, Mailstop #137, Los Angeles, CA 90027 USA
| | - Namath Hussain
- Department of Cardiothoracic Surgery, Saban Research Institute of the Children's Hospital of Los Angeles, University of Southern California Keck School of Medicine, 4650 Sunset Blvd, Mailstop #137, Los Angeles, CA 90027 USA
| | - Irina Shulkin
- Department of Cardiothoracic Surgery, Saban Research Institute of the Children's Hospital of Los Angeles, University of Southern California Keck School of Medicine, 4650 Sunset Blvd, Mailstop #137, Los Angeles, CA 90027 USA
| | - Alan Xu
- Department of Cardiothoracic Surgery, Saban Research Institute of the Children's Hospital of Los Angeles, University of Southern California Keck School of Medicine, 4650 Sunset Blvd, Mailstop #137, Los Angeles, CA 90027 USA
| | - Margaret Yew
- Department of Cardiothoracic Surgery, Saban Research Institute of the Children's Hospital of Los Angeles, University of Southern California Keck School of Medicine, 4650 Sunset Blvd, Mailstop #137, Los Angeles, CA 90027 USA
| | - Donald V Cramer
- Department of Cardiothoracic Surgery, Saban Research Institute of the Children's Hospital of Los Angeles, University of Southern California Keck School of Medicine, 4650 Sunset Blvd, Mailstop #137, Los Angeles, CA 90027 USA
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Liu D, Kobayashi T, Onishi A, Furusawa T, Iwamoto M, Suzuki S, Miwa Y, Nagasaka T, Maruyama S, Kadomatsu K, Uchida K, Nakao A. Relation between human decay-accelerating factor (hDAF) expression in pig cells and inhibition of human serum anti-pig cytotoxicity: value of highly expressed hDAF for xenotransplantation. Xenotransplantation 2007; 14:67-73. [PMID: 17214706 DOI: 10.1111/j.1399-3089.2006.00365.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Although the successful production of alpha1,3-galactosyltransferase-knockout (GT-KO) pigs has increased expectations of clinical xenotransplantation, additional modifications of genetically engineered pigs are still being explored, because even GT-KO pigs are incapable of inhibiting the host's immunological response completely. One of the potential candidates is a complement-regulatory protein, such as human decay-accelerating factor (hDAF). However, there are few reports on how high the expression level of hDAF in pig cells would be required for suppression of complement activation. The purpose of this study was to examine the relationship between the level of hDAF expression and its inhibitory effect on human serum cytotoxicity. METHODS An expression (pCAGGS) vector containing the hDAF gene was transfected into pig fibroblasts using an electroporation system (Gene Pulser II). Forty-eight to fifty-two hours after transfection, the cells were stained with FITC-labeled anti-hDAF antibody and then applied to the cell sorter. hDAF-transfected cells with various expression levels were collected by gating on fluorescence intensity. The level of hDAF expression was determined relative to that in human control endothelial cells. Collected cells expressing x1, x5, x10, x15 and x30 hDAF were incubated into 96-well plates for 16 h, and the cells were subjected to 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide (MTT) assay. RESULTS hDAF expression levels in transfected cells at the time of MTT assay (16 h after sorting) were comparable to those immediately after sorting. hDAF expression in pig cells five times higher than in human endothelial cells was effective in inhibiting complement-dependent cytotoxicity of most human sera. However, 15- to 30-fold expression of hDAF was required for effective inhibition of human sera with the highest cytotoxic capacity. CONCLUSIONS A much higher level of hDAF expression in pig cells than previously considered necessary might be required to provide additional benefit in inhibiting antibody-mediated rejection. Genetically engineered pigs that express very high levels of hDAF would be beneficial for xenotransplantation.
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Affiliation(s)
- DaGe Liu
- Department of Surgery II, Nagoya University School of Medicine, Nagoya, Japan
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