254
Transplantation
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February 2015
■
Volume 99
■
Number 2
was appointed director of the Transplantation Biology Section of the Immunology Branch, NCI, in 1974, then chief of the Immunology Branch in 1982. In 1990, David returned to the MGH and Harvard Medical School, where he felt he could bring his translational goals to the next level as a professor of surgery and director of the new Transplantation Biology Research Center, which rapidly became one of the world's leading transplantation centers. I was fortunate to be recruited by David as an assistant professor and benefited from the rich and collaborative research environment he created. It was there that David, with Drs. Ben Cosimi and Tatsuo Kawai, established the preclinical nonhuman primate transplant model that was pivotal in leading to the first clinical trials of combined kidney and bone marrow transplantation with intentional achievement of transplantation tolerance. David recognized that to achieve his translational goals, a key component would be a clinical bone marrow transplant (BMT) program, for which he was able to work with MGH to recruit Dr. Thomas Spitzer as director. Soon after Dr. Spitzer established the BMT program, he and I began to collaborate on the development of a mixed chimerism-based strategy for treatment of cancer patients that ultimately led to the protocol David and Ben used for the induction of renal allograft tolerance in the clinic. This collaboration between the BMT and organ transplant programs, for which David was largely responsible, permitted the culmination of a vision that he had developed over more than 20 years, beginning with his studies of mixed chimerism for tolerance induction in ro-
www.transplantjournal.com
dents, followed by the porcine and nonhuman primate studies and ultimately the successful application in humans. I would like to end this introduction with a few personal comments about David, who has been a role model, mentor, collaborator, and friend through my entire scientific career. I first met David in 1984 when he was chief of the Immunology Branch at the NCI, near the end of an arduous day of tightly timed half-hour fellowship interviews, each of which seemed to require a sprint across the vast NIH campus. Needless to say, I was somewhat frazzled when I entered David's office 20 minutes late for my 14th interview of the day. I was visiting the NIH to find a laboratory in which to pursue research in immunology, but had thought I would most likely work in an area of autoimmunity. David's manner immediately put me at ease, and his infectious enthusiasm and willingness to discuss ideas inspired me to enter the field of transplantation, as I quickly realized that I had found a mentor. He has similarly inspired and mentored generations of young scientists, many of whom went on to become leaders in our field. I consider myself very fortunate to have been one of the many beneficiaries of David's mentorship and also to be among the many who consider him one of their best friends. David's generosity, wisdom, and single-minded dedication to his goals have set an example to which younger scientists can aspire. This legacy, combined with the ground-breaking scientific contributions David has made in our field, deserves our deepest appreciation and recognition, which are now bestowed upon him with the award of the Medawar Prize.
The Medawar Prize Acceptance Speech 2014 David H. Sachs1
I
am honored and grateful to be the recipient of this award, especially because the work of Sir Peter Medawar was of such great importance to the development of my own career and to that of many of my mentors and colleagues. I have been asked today to provide a brief summary of my career, which I will attempt to do in the time allotted. However, because that time is brief, I must apologize in advance to the many people whom I may not mention by name, but whose efforts and contributions have been of great importance to my career and to whom I am also very grateful. I trace the beginning of my career in the field of transplantation to a lecture by Hugh McDevitt, during my second year at Harvard Medical School, in 1965. During that lecture, McDevitt described an experiment of nature which had been reported 2 decades earlier by Ray Owen, concerning the inheritance of blood groups by Freemartin cattle.1 These are fraternal cattle twins born of a common placenta. Owen had demonstrated that the blood groups of these cattle could only 1
Massachusetts General Hospital, Boston MA.
Correspondence: David H. Sachs, Massachusetts General Hospital, 55 Fruit St, Boston MA 02114. ([email protected]) Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0041-1337/15/9902-254 DOI: 10.1097/TP.0000000000000627
be explained by an exchange of hematopoietic cells between the twins in utero, which had thereafter survived into adult life. Sir Peter Medawar exchanged skin grafts between these cattle and found that they survived much longer than would have been predicted for fraternal twins.2 Recognizing that long-term survival of blood cells exchanged in utero implied that the animals had become immunologically tolerant of each other's tissue antigens, he and his colleagues then demonstrated the same phenomenon in the laboratory, using inbred mice.3 They showed that injection of hematopoietic cells between disparate strains of mice during the first 24 hours of life led to long-term acceptance of skin grafts in many of these mice when they reached adulthood. This was the first demonstration of the intentional induction of transplantation tolerance. For me, experiments of nature have always provided the most important proof of principle for the validity of unexpected biological phenomena. Of course, in the clinical setting, one does not know before an individual is born whether he/she will need an organ transplant as an adult. However, the fact that transplantation tolerance could be induced early in life proved that the phenomenon was possible. I was intrigued by the goal of inducing such tolerance in adults in need of a transplant and decided that this was an area of experimentation in which I wanted to work. I therefore inquired who in Boston was working in this field, and I was directed to
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
255
© 2015 Wolters Kluwer
FIGURE 1. Dr. David Sachs.
Dr. Paul Russell at the Massachusetts General Hospital (MGH). Dr. Russell accepted me into his laboratory as a student researcher and he became, and has remained, an important mentor and a close friend ever since. Dr. Russell introduced me, in turn, to Dr. Henry Winn, an immunogeneticist whom he had recently recruited to the MGH from the Jackson Laboratories in Bar Harbor, Maine. I worked with Drs. Winn and Russell during the summers and part time during the school year for the rest of my time at Harvard Medical School. My interest in transplantation led me to a surgical residency, also at the MGH. During the second year of that residency, I received a surgical scientist training grant, which enabled me to work partly on the transplant service and partly in the laboratory, again with Drs. Winn and Russell (Figure 1). During that period, I worked on the problem of the immunologic response to xenografts.4 Like tolerance, xenografts represented an area of research to which I was drawn by an experiment of nature—in this case, the nude mouse. This mutant strain of mice, born without a thymus and therefore without a cellular immune system, had been shown to accept skin grafts from numerous other species.5 Again, this indicated to me that xenografts could work—a conviction which I have maintained to this day, as I will describe further, later in this lecture. In 1970, I took a leave of absence from the MGH surgical residency for 2 years of military service, working as a fellow at the NIH. There, I worked with Dr. Christian B. Anfinsen, on the use of antibodies to study conformational equilibria of polypeptides.6 At the end of those 2 years, I was offered my own laboratory in the National Cancer Institute. Curious to
determine whether or not I would be capable of developing an independent research program, I applied for, and was granted, an extension of my leave of absence from the surgical residency. It was during the next year, while trying to make anti-idiotypic antibodies for induction of tolerance in mice that we discovered a previously unknown antigen expressed predominantly on B cells and macrophages and encoded by genes mapping within the MHC.7 This turned out to be the first serologic description of class II antigens—and led to a rapid increase in the size of my laboratory and another extension of my leave of absence from the MGH. One area of investigation undertaken in my laboratory at the NIH over the next 2 decades that was of particular importance to the goal of tolerance induction was the development of protocols for mixed hematopoietic chimerism. My close colleague, Ben Cosimi, used to say that there are hundreds of methods described for inducing tolerance in mice, but none of them work in large animals or in the clinic. However, mixed chimerism has been an exception. This technology modifies the recipient's immune system by establishing a mixture of host and donor hematopoietic elements through bone marrow transplantation. We were able to demonstrate, while at the NIH, that such chimerism was effective in inducing tolerance both in mice8 and in miniature swine.9 Then, after I returned to the MGH, and in collaboration with Cosimi and his colleague, Tatsuo Kawai, we demonstrated that mixed chimerism could also induce tolerance in monkeys.10 This methodology has most recently been taken successfully to the clinic.11 The methodology has required modifications in each species, and multiple mechanisms are likely involved, but the principle of mixed chimerism as a means of inducing transplantation tolerance clearly transcends the species. In 1991, I returned to the MGH, where I had been offered the opportunity to establish a new research center, the Transplantation Biology Research Center. Among my most important recruits to this new research center was Dr. Megan Sykes, who had been a fellow in my laboratory at the NIH and who quickly established her own outstanding laboratory
FIGURE 2. At the 2012 celebration of the 10th anniversary of the first successful tolerance transplant procedure, with several tolerant renal transplant patients and members of the transplant team.
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
256
Transplantation
■
February 2015
■
Volume 99
■
Number 2
FIGURE 3. Dr. Sachs with genetically engineered miniature swine.
at the MGH. Indeed, Dr. Sykes and Dr. Cosimi have been chief among my partners in the quest to bring mixed chimerism and tolerance from animal models to the clinic. (I am
www.transplantjournal.com
also proud to count them among my closest friends.) This collaborative effort culminated in a paper published in the New England Journal of Medicine in 2008, demonstrating that 4 of the first 5 patients treated by a mixed chimerism protocol were able to be weaned from all immunosuppression for a period of 3 to 5 years.12 In 2012, we celebrated the 10th anniversary of tolerance induction in the first of these patients, shown in Figure 2 (second from the right), along with several other tolerant patients from this protocol and members of our transplant team. My story would not be complete without mention of my part-time career as a pig farmer (Figure 3). I decided, while still at the NIH, that we needed a large animal model in the field of transplantation in which it would be possible to carry out genetic experiments, only possible at that time in mice. I chose miniature swine because of their size, which was identical to that of humans, their reproductive capacity, which would permit genetic experiments to be carried out in a feasible time frame, and because I considered them a likely candidate for a xenograft donor, to solve the problem of organ availability. Within a few years, we were able to achieve strains homozygous for the MHC (called SLA in swine), as well as recombinants within the SLA, making this the only large animal model in which it is possible to carry out transplants reproducibly across major, minor, or even selective class I or class II mismatched barriers.13 These animals have proved extremely helpful in studies of allogeneic tolerance. In addition, in contrast to tolerance studies in mice, the results of experiments in these swine have generally been readily translated to primates.
TABLE 1.
With Thanks to the Outstanding Pre- and Postdoctoral Fellow With Whom I Have Worked, (1973–2014)
Garrison C. Fathman, MD, 1973 Ted Hansen, PhD, 1975 David Pisetsky, MD, PhD, 1975 Nobukata Shinohara, MD, 1975, 1983 Wayne M. Flye, MD, 1976 Robert Kirkman, MD, 1976 Paul Nadler, MD, 1977 Geraldine Miller, MD, 1978 Keiko Ozato, PhD, 1978 Larry Pennington, MD, 1978 Hugh Auchincloss, MD, 1979 Jeffrey Bluestone, MD, 1979 Suzanne Epstein, PhD, 1979 Joan Lunney, PhD, 1979 James Thistlewaite, MD, 1980 Mark Pescovitz, MD, 1981 Suzanne Ildstad, MD, 1982 Ruth Rabinowitz, PhD, 1982 Christian Devaux, PhD, 1983 Oberdan Leo, PhD, 1983 Eunkye Park, PhD, 1984 Kaoru Sakamoto, MD, PhD, 1984 Megan Sykes, MD, 1985 Francois Hirsch, PhD, 1986 Karen Pratt, PhD, 1986 Yedida Sharabi, PhD, 1986 Takao Suzuki, MD, 1986 Kenth Gustafsson, PhD, 1987
Thoralf Sundt, MD, 1987 Bruce Rosengard, MD, 1988 David Emery, PhD, 1991 Pierre Gianello, MD, 1991 Dominique Latinne, MD, 1991 Craig Smith, MD, 1991 Thomas Lorf, MD, 1992 Tomasz Sablinski, MD, PhD, 1992 Robin Lee, MD, 1993 Kazuhiko Yamada, MD, PhD, 1993 David Anderson, PhD, 1994 Francesco Ierino, MD, PhD, 1994 Tomasz Kozlowski, MD, 1994 Han Lei, MD, 1994 Yasushi Fuchimoto, MD, 1995 Christene Huang, PhD, 1995 Jorg Seebach, MD, 1995 Akihiko Yasumoto, MD, PhD, 1995 Christine Colby, PharmD, 1996 Nestor Esnaola, MD, 1996 Denis Lambrigts, DVM, 1996 Gary Haller, MD, 1997 Anette Wu, MD, 1997 Shaun Kunasaki, MD, 1998 Ryu Utsugi, MD, 1998 Rolf Barth, MD, 1999 Zachary Gleit, MD, 1999 Naoki Kumagi, MD, 1999
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
John LaMattina, MD, 2000 Andrew Cameron, MD, PhD, 2001 Robert Cina, MD, 2001 Chisako Kamano, MD, 2001 Parsia Vagefi, MD, 2001 Hanzhou Hong, MD, 2002 Patricia Lee, MD, 2002 Akira Shimizu, MD, 2002 Shuji Nobori, MD, 2003 Matthew Nuhn, MD, 2003 Koji Yazawa, MD, 2003 Banny Wong, MD, 2004 Patricia Cho, MD, 2004 John Hanekamp, MD, 2004 Yosuke Hisashi, MD, 2004 Masa Okumi, MD, 2004 Krzysztof Wikiel, MD, 2004 Adam D. Griesemer, MD, 2005 Atsushi Hirakata, MD, 2005 Benjamin Horner, MD, 2005 Prashanth Vallabhajosyula, MD, 2005 Matthew J. Weiss, MD, 2005 Joshua Weiner, MD, 2008 Fan Liang, MD, 2009 Joseph Scalea, MD, 2009 Isaac Wamala, MD, 2009 David Leonard, BSc, MBChB, 2010 Vincenzo Villani, MD, 2011
257
© 2015 Wolters Kluwer
All of these work have been carried out by a large number of outstanding pre-doctoral and postdoctoral fellows with whom I have had the privilege of working over these years and to whom I owe so much (Table 1). Last, but not least, none of this work could have been accomplished without the love, support and endurance of my wife of 45 years, Kristina (Figure 4). REFERENCES
FIGURE 4. Dr. Sachs with wife, Kristina, at Rome Congress, 2000.
In addition, the size and the fact that they are inbred have made these animals an outstanding potential donor for xenografts.14 As soon as techniques for genetic engineering of large animals became available, we began to modify these swine to make their cells and organs more compatible with the immune system of primates. Starting with an inbred line of our miniature swine, we knocked out the gene encoding the most important antigen (Gal), responsible for antibodymediated rejection after pig-to-primate transplantation.15 Using these animals as donors, and a tolerance induction protocol involving concomitant thymic transplantation, Dr. Kazuhiko Yamada was able to obtain over 80-day survival of a baboon whose renal function was maintained by a pig kidney.16 We have subsequently engineered into these animals a human transgene (CD47) which has enabled us for the first time to establish the kind of transient pig-to-primate mixed chimerism which has previously been effective in inducing tolerance in monkeys and in our recent clinical study. Progress in the field of xenotransplantation has been slow but it has been continuous. When I first started in this field, the survival of vascularized organs from pigs transplanted into nonhuman primates was measured in minutes, while now the survivals are measured in months. As we and other groups continue to modify swine through genetic engineering, these results should continue to improve. I am therefore hopeful that 1 day, in the not-too-distant future, these animals will eliminate many of the problems now caused by the shortage of human organs for transplantation.
1. Owen RD. Immunogenetic consequences of vascular anastomoses between bovine twins. Science 1945;102:400. 2. Brent L. The discovery of immunologic tolerance. Hum Immunol 1997;52:75. 3. Billingham RE, Brent L, Medawar PB. Actively acquired tolerance to foreign cells. Nature 1953;172:603. 4. Sachs DH, Winn HJ, Russell PS. The immunologic response to xenografts. Recognition of mouse H-2 histocompatibility antigens by the rat. J Immunol 1971;107:481. 5. Rygaard J. Skin grafts in nude mice. 3. Fate of grafts from man and donors of other taxonomic classes. Acta Pathol Microbiol Scand [A] 1974;82:105. 6. Sachs DH, Schechter AN, Eastlake A, Anfinsen CB. An immunologic approach to the conformational equilibria of polypeptides. Proc Natl Acad Sci USA 1972;69:3790. 7. Sachs DH, Cone JL. A mouse B-cell alloantigen determined by gene(s) linked to the major histocompatibility complex. J Exp Med 1973;138:1289. 8. Sykes M, Sachs DH. Mixed allogeneic chimerism as an approach to transplantation tolerance. Immunol Today 1988;9:23. 9. Guzzetta PC, Sundt TM, Suzuki T, Mixon A, Rosengard BR, Sachs DH. Induction of kidney transplantation tolerance across MHC barriers by bone marrow transplantation in miniature swine. Transplantation 1991;51:862. 10. Kawai T, Cosimi AB, Colvin RB, et al. Mixed allogeneic chimerism and renal allograft tolerance in cynomolgus monkeys. Transplantation 1995;59:256. 11. Kawai T, Cosimi AB, Spitzer TR, et al. HLA-mismatched renal transplantationwithout maintenance immunosuppression. N Engl J Med 2008; 358:353. 12. Sahara H, Weiss MJ, Ng CY, et al. Thymectomy does not abrogate longterm acceptance of MHC class I-disparate lung allografts in miniature Swine. Transplant Proc 2006;38:3253. 13. Sachs DH. MHC homozygous miniature swine. In: Swine as Models in Biomedical Research, Eds. Swindle MM, Moody DC, Phillips LD. Ames, Iowa: Iowa State University Press, 1992. 3. 14. Sachs DH, Sykes M, Robson SC, Cooper DK. Xenotransplantation. Adv Immunol 2001;79:129. 15. Kolber-Simonds D, Lai L, Watt SR, et al. Production of alpha-1,3galactosyltransferase null pigs by means of nuclear transfer with fibroblasts bearing loss of heterozygosity mutations. Proc Natl Acad Sci U S A 2004;101:7335. 16. Yamada K, Yazawa K, Shimizu A, et al. Marked prolongation of porcine renal xenograft survival in baboons through the use of alpha1,3galactosyltransferase gene-knockout donors and the cotransplantation of vascularized thymic tissue. Nat Med 2005;11:32.
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Transplantation
■
February 2015
■
Volume 99
■
Number 2
was appointed director of the Transplantation Biology Section of the Immunology Branch, NCI, in 1974, then chief of the Immunology Branch in 1982. In 1990, David returned to the MGH and Harvard Medical School, where he felt he could bring his translational goals to the next level as a professor of surgery and director of the new Transplantation Biology Research Center, which rapidly became one of the world's leading transplantation centers. I was fortunate to be recruited by David as an assistant professor and benefited from the rich and collaborative research environment he created. It was there that David, with Drs. Ben Cosimi and Tatsuo Kawai, established the preclinical nonhuman primate transplant model that was pivotal in leading to the first clinical trials of combined kidney and bone marrow transplantation with intentional achievement of transplantation tolerance. David recognized that to achieve his translational goals, a key component would be a clinical bone marrow transplant (BMT) program, for which he was able to work with MGH to recruit Dr. Thomas Spitzer as director. Soon after Dr. Spitzer established the BMT program, he and I began to collaborate on the development of a mixed chimerism-based strategy for treatment of cancer patients that ultimately led to the protocol David and Ben used for the induction of renal allograft tolerance in the clinic. This collaboration between the BMT and organ transplant programs, for which David was largely responsible, permitted the culmination of a vision that he had developed over more than 20 years, beginning with his studies of mixed chimerism for tolerance induction in ro-
www.transplantjournal.com
dents, followed by the porcine and nonhuman primate studies and ultimately the successful application in humans. I would like to end this introduction with a few personal comments about David, who has been a role model, mentor, collaborator, and friend through my entire scientific career. I first met David in 1984 when he was chief of the Immunology Branch at the NCI, near the end of an arduous day of tightly timed half-hour fellowship interviews, each of which seemed to require a sprint across the vast NIH campus. Needless to say, I was somewhat frazzled when I entered David's office 20 minutes late for my 14th interview of the day. I was visiting the NIH to find a laboratory in which to pursue research in immunology, but had thought I would most likely work in an area of autoimmunity. David's manner immediately put me at ease, and his infectious enthusiasm and willingness to discuss ideas inspired me to enter the field of transplantation, as I quickly realized that I had found a mentor. He has similarly inspired and mentored generations of young scientists, many of whom went on to become leaders in our field. I consider myself very fortunate to have been one of the many beneficiaries of David's mentorship and also to be among the many who consider him one of their best friends. David's generosity, wisdom, and single-minded dedication to his goals have set an example to which younger scientists can aspire. This legacy, combined with the ground-breaking scientific contributions David has made in our field, deserves our deepest appreciation and recognition, which are now bestowed upon him with the award of the Medawar Prize.
The Medawar Prize Acceptance Speech 2014 David H. Sachs1
I
am honored and grateful to be the recipient of this award, especially because the work of Sir Peter Medawar was of such great importance to the development of my own career and to that of many of my mentors and colleagues. I have been asked today to provide a brief summary of my career, which I will attempt to do in the time allotted. However, because that time is brief, I must apologize in advance to the many people whom I may not mention by name, but whose efforts and contributions have been of great importance to my career and to whom I am also very grateful. I trace the beginning of my career in the field of transplantation to a lecture by Hugh McDevitt, during my second year at Harvard Medical School, in 1965. During that lecture, McDevitt described an experiment of nature which had been reported 2 decades earlier by Ray Owen, concerning the inheritance of blood groups by Freemartin cattle.1 These are fraternal cattle twins born of a common placenta. Owen had demonstrated that the blood groups of these cattle could only 1
Massachusetts General Hospital, Boston MA.
Correspondence: David H. Sachs, Massachusetts General Hospital, 55 Fruit St, Boston MA 02114. ([email protected]) Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0041-1337/15/9902-254 DOI: 10.1097/TP.0000000000000627
be explained by an exchange of hematopoietic cells between the twins in utero, which had thereafter survived into adult life. Sir Peter Medawar exchanged skin grafts between these cattle and found that they survived much longer than would have been predicted for fraternal twins.2 Recognizing that long-term survival of blood cells exchanged in utero implied that the animals had become immunologically tolerant of each other's tissue antigens, he and his colleagues then demonstrated the same phenomenon in the laboratory, using inbred mice.3 They showed that injection of hematopoietic cells between disparate strains of mice during the first 24 hours of life led to long-term acceptance of skin grafts in many of these mice when they reached adulthood. This was the first demonstration of the intentional induction of transplantation tolerance. For me, experiments of nature have always provided the most important proof of principle for the validity of unexpected biological phenomena. Of course, in the clinical setting, one does not know before an individual is born whether he/she will need an organ transplant as an adult. However, the fact that transplantation tolerance could be induced early in life proved that the phenomenon was possible. I was intrigued by the goal of inducing such tolerance in adults in need of a transplant and decided that this was an area of experimentation in which I wanted to work. I therefore inquired who in Boston was working in this field, and I was directed to
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
255
© 2015 Wolters Kluwer
FIGURE 1. Dr. David Sachs.
Dr. Paul Russell at the Massachusetts General Hospital (MGH). Dr. Russell accepted me into his laboratory as a student researcher and he became, and has remained, an important mentor and a close friend ever since. Dr. Russell introduced me, in turn, to Dr. Henry Winn, an immunogeneticist whom he had recently recruited to the MGH from the Jackson Laboratories in Bar Harbor, Maine. I worked with Drs. Winn and Russell during the summers and part time during the school year for the rest of my time at Harvard Medical School. My interest in transplantation led me to a surgical residency, also at the MGH. During the second year of that residency, I received a surgical scientist training grant, which enabled me to work partly on the transplant service and partly in the laboratory, again with Drs. Winn and Russell (Figure 1). During that period, I worked on the problem of the immunologic response to xenografts.4 Like tolerance, xenografts represented an area of research to which I was drawn by an experiment of nature—in this case, the nude mouse. This mutant strain of mice, born without a thymus and therefore without a cellular immune system, had been shown to accept skin grafts from numerous other species.5 Again, this indicated to me that xenografts could work—a conviction which I have maintained to this day, as I will describe further, later in this lecture. In 1970, I took a leave of absence from the MGH surgical residency for 2 years of military service, working as a fellow at the NIH. There, I worked with Dr. Christian B. Anfinsen, on the use of antibodies to study conformational equilibria of polypeptides.6 At the end of those 2 years, I was offered my own laboratory in the National Cancer Institute. Curious to
determine whether or not I would be capable of developing an independent research program, I applied for, and was granted, an extension of my leave of absence from the surgical residency. It was during the next year, while trying to make anti-idiotypic antibodies for induction of tolerance in mice that we discovered a previously unknown antigen expressed predominantly on B cells and macrophages and encoded by genes mapping within the MHC.7 This turned out to be the first serologic description of class II antigens—and led to a rapid increase in the size of my laboratory and another extension of my leave of absence from the MGH. One area of investigation undertaken in my laboratory at the NIH over the next 2 decades that was of particular importance to the goal of tolerance induction was the development of protocols for mixed hematopoietic chimerism. My close colleague, Ben Cosimi, used to say that there are hundreds of methods described for inducing tolerance in mice, but none of them work in large animals or in the clinic. However, mixed chimerism has been an exception. This technology modifies the recipient's immune system by establishing a mixture of host and donor hematopoietic elements through bone marrow transplantation. We were able to demonstrate, while at the NIH, that such chimerism was effective in inducing tolerance both in mice8 and in miniature swine.9 Then, after I returned to the MGH, and in collaboration with Cosimi and his colleague, Tatsuo Kawai, we demonstrated that mixed chimerism could also induce tolerance in monkeys.10 This methodology has most recently been taken successfully to the clinic.11 The methodology has required modifications in each species, and multiple mechanisms are likely involved, but the principle of mixed chimerism as a means of inducing transplantation tolerance clearly transcends the species. In 1991, I returned to the MGH, where I had been offered the opportunity to establish a new research center, the Transplantation Biology Research Center. Among my most important recruits to this new research center was Dr. Megan Sykes, who had been a fellow in my laboratory at the NIH and who quickly established her own outstanding laboratory
FIGURE 2. At the 2012 celebration of the 10th anniversary of the first successful tolerance transplant procedure, with several tolerant renal transplant patients and members of the transplant team.
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
256
Transplantation
■
February 2015
■
Volume 99
■
Number 2
FIGURE 3. Dr. Sachs with genetically engineered miniature swine.
at the MGH. Indeed, Dr. Sykes and Dr. Cosimi have been chief among my partners in the quest to bring mixed chimerism and tolerance from animal models to the clinic. (I am
www.transplantjournal.com
also proud to count them among my closest friends.) This collaborative effort culminated in a paper published in the New England Journal of Medicine in 2008, demonstrating that 4 of the first 5 patients treated by a mixed chimerism protocol were able to be weaned from all immunosuppression for a period of 3 to 5 years.12 In 2012, we celebrated the 10th anniversary of tolerance induction in the first of these patients, shown in Figure 2 (second from the right), along with several other tolerant patients from this protocol and members of our transplant team. My story would not be complete without mention of my part-time career as a pig farmer (Figure 3). I decided, while still at the NIH, that we needed a large animal model in the field of transplantation in which it would be possible to carry out genetic experiments, only possible at that time in mice. I chose miniature swine because of their size, which was identical to that of humans, their reproductive capacity, which would permit genetic experiments to be carried out in a feasible time frame, and because I considered them a likely candidate for a xenograft donor, to solve the problem of organ availability. Within a few years, we were able to achieve strains homozygous for the MHC (called SLA in swine), as well as recombinants within the SLA, making this the only large animal model in which it is possible to carry out transplants reproducibly across major, minor, or even selective class I or class II mismatched barriers.13 These animals have proved extremely helpful in studies of allogeneic tolerance. In addition, in contrast to tolerance studies in mice, the results of experiments in these swine have generally been readily translated to primates.
TABLE 1.
With Thanks to the Outstanding Pre- and Postdoctoral Fellow With Whom I Have Worked, (1973–2014)
Garrison C. Fathman, MD, 1973 Ted Hansen, PhD, 1975 David Pisetsky, MD, PhD, 1975 Nobukata Shinohara, MD, 1975, 1983 Wayne M. Flye, MD, 1976 Robert Kirkman, MD, 1976 Paul Nadler, MD, 1977 Geraldine Miller, MD, 1978 Keiko Ozato, PhD, 1978 Larry Pennington, MD, 1978 Hugh Auchincloss, MD, 1979 Jeffrey Bluestone, MD, 1979 Suzanne Epstein, PhD, 1979 Joan Lunney, PhD, 1979 James Thistlewaite, MD, 1980 Mark Pescovitz, MD, 1981 Suzanne Ildstad, MD, 1982 Ruth Rabinowitz, PhD, 1982 Christian Devaux, PhD, 1983 Oberdan Leo, PhD, 1983 Eunkye Park, PhD, 1984 Kaoru Sakamoto, MD, PhD, 1984 Megan Sykes, MD, 1985 Francois Hirsch, PhD, 1986 Karen Pratt, PhD, 1986 Yedida Sharabi, PhD, 1986 Takao Suzuki, MD, 1986 Kenth Gustafsson, PhD, 1987
Thoralf Sundt, MD, 1987 Bruce Rosengard, MD, 1988 David Emery, PhD, 1991 Pierre Gianello, MD, 1991 Dominique Latinne, MD, 1991 Craig Smith, MD, 1991 Thomas Lorf, MD, 1992 Tomasz Sablinski, MD, PhD, 1992 Robin Lee, MD, 1993 Kazuhiko Yamada, MD, PhD, 1993 David Anderson, PhD, 1994 Francesco Ierino, MD, PhD, 1994 Tomasz Kozlowski, MD, 1994 Han Lei, MD, 1994 Yasushi Fuchimoto, MD, 1995 Christene Huang, PhD, 1995 Jorg Seebach, MD, 1995 Akihiko Yasumoto, MD, PhD, 1995 Christine Colby, PharmD, 1996 Nestor Esnaola, MD, 1996 Denis Lambrigts, DVM, 1996 Gary Haller, MD, 1997 Anette Wu, MD, 1997 Shaun Kunasaki, MD, 1998 Ryu Utsugi, MD, 1998 Rolf Barth, MD, 1999 Zachary Gleit, MD, 1999 Naoki Kumagi, MD, 1999
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
John LaMattina, MD, 2000 Andrew Cameron, MD, PhD, 2001 Robert Cina, MD, 2001 Chisako Kamano, MD, 2001 Parsia Vagefi, MD, 2001 Hanzhou Hong, MD, 2002 Patricia Lee, MD, 2002 Akira Shimizu, MD, 2002 Shuji Nobori, MD, 2003 Matthew Nuhn, MD, 2003 Koji Yazawa, MD, 2003 Banny Wong, MD, 2004 Patricia Cho, MD, 2004 John Hanekamp, MD, 2004 Yosuke Hisashi, MD, 2004 Masa Okumi, MD, 2004 Krzysztof Wikiel, MD, 2004 Adam D. Griesemer, MD, 2005 Atsushi Hirakata, MD, 2005 Benjamin Horner, MD, 2005 Prashanth Vallabhajosyula, MD, 2005 Matthew J. Weiss, MD, 2005 Joshua Weiner, MD, 2008 Fan Liang, MD, 2009 Joseph Scalea, MD, 2009 Isaac Wamala, MD, 2009 David Leonard, BSc, MBChB, 2010 Vincenzo Villani, MD, 2011
257
© 2015 Wolters Kluwer
All of these work have been carried out by a large number of outstanding pre-doctoral and postdoctoral fellows with whom I have had the privilege of working over these years and to whom I owe so much (Table 1). Last, but not least, none of this work could have been accomplished without the love, support and endurance of my wife of 45 years, Kristina (Figure 4). REFERENCES
FIGURE 4. Dr. Sachs with wife, Kristina, at Rome Congress, 2000.
In addition, the size and the fact that they are inbred have made these animals an outstanding potential donor for xenografts.14 As soon as techniques for genetic engineering of large animals became available, we began to modify these swine to make their cells and organs more compatible with the immune system of primates. Starting with an inbred line of our miniature swine, we knocked out the gene encoding the most important antigen (Gal), responsible for antibodymediated rejection after pig-to-primate transplantation.15 Using these animals as donors, and a tolerance induction protocol involving concomitant thymic transplantation, Dr. Kazuhiko Yamada was able to obtain over 80-day survival of a baboon whose renal function was maintained by a pig kidney.16 We have subsequently engineered into these animals a human transgene (CD47) which has enabled us for the first time to establish the kind of transient pig-to-primate mixed chimerism which has previously been effective in inducing tolerance in monkeys and in our recent clinical study. Progress in the field of xenotransplantation has been slow but it has been continuous. When I first started in this field, the survival of vascularized organs from pigs transplanted into nonhuman primates was measured in minutes, while now the survivals are measured in months. As we and other groups continue to modify swine through genetic engineering, these results should continue to improve. I am therefore hopeful that 1 day, in the not-too-distant future, these animals will eliminate many of the problems now caused by the shortage of human organs for transplantation.
1. Owen RD. Immunogenetic consequences of vascular anastomoses between bovine twins. Science 1945;102:400. 2. Brent L. The discovery of immunologic tolerance. Hum Immunol 1997;52:75. 3. Billingham RE, Brent L, Medawar PB. Actively acquired tolerance to foreign cells. Nature 1953;172:603. 4. Sachs DH, Winn HJ, Russell PS. The immunologic response to xenografts. Recognition of mouse H-2 histocompatibility antigens by the rat. J Immunol 1971;107:481. 5. Rygaard J. Skin grafts in nude mice. 3. Fate of grafts from man and donors of other taxonomic classes. Acta Pathol Microbiol Scand [A] 1974;82:105. 6. Sachs DH, Schechter AN, Eastlake A, Anfinsen CB. An immunologic approach to the conformational equilibria of polypeptides. Proc Natl Acad Sci USA 1972;69:3790. 7. Sachs DH, Cone JL. A mouse B-cell alloantigen determined by gene(s) linked to the major histocompatibility complex. J Exp Med 1973;138:1289. 8. Sykes M, Sachs DH. Mixed allogeneic chimerism as an approach to transplantation tolerance. Immunol Today 1988;9:23. 9. Guzzetta PC, Sundt TM, Suzuki T, Mixon A, Rosengard BR, Sachs DH. Induction of kidney transplantation tolerance across MHC barriers by bone marrow transplantation in miniature swine. Transplantation 1991;51:862. 10. Kawai T, Cosimi AB, Colvin RB, et al. Mixed allogeneic chimerism and renal allograft tolerance in cynomolgus monkeys. Transplantation 1995;59:256. 11. Kawai T, Cosimi AB, Spitzer TR, et al. HLA-mismatched renal transplantationwithout maintenance immunosuppression. N Engl J Med 2008; 358:353. 12. Sahara H, Weiss MJ, Ng CY, et al. Thymectomy does not abrogate longterm acceptance of MHC class I-disparate lung allografts in miniature Swine. Transplant Proc 2006;38:3253. 13. Sachs DH. MHC homozygous miniature swine. In: Swine as Models in Biomedical Research, Eds. Swindle MM, Moody DC, Phillips LD. Ames, Iowa: Iowa State University Press, 1992. 3. 14. Sachs DH, Sykes M, Robson SC, Cooper DK. Xenotransplantation. Adv Immunol 2001;79:129. 15. Kolber-Simonds D, Lai L, Watt SR, et al. Production of alpha-1,3galactosyltransferase null pigs by means of nuclear transfer with fibroblasts bearing loss of heterozygosity mutations. Proc Natl Acad Sci U S A 2004;101:7335. 16. Yamada K, Yazawa K, Shimizu A, et al. Marked prolongation of porcine renal xenograft survival in baboons through the use of alpha1,3galactosyltransferase gene-knockout donors and the cotransplantation of vascularized thymic tissue. Nat Med 2005;11:32.
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