Since mixed chimerism has been shown in mouse and humanized mouse models (Project 3) to have the ability not only to induce central T cell tolerance, but also to prevent new antibody responses and turn off existing antibody responses, the establishment of xenogeneic mixed chimerism remains an attractive means for achieving xenograft tolerance. Before GalT-KO miniature swine were available, the failure of attempts to achieve mixed chimerism across the pig-to-primate barrier was attributed to high levels of primate natural antibodies to the Gal antigen. However, despite the absence of the Gal antigen on the cell surface of GalT-KO hematopoeitic cells (HSC), we have found that these cells are rapidly cleared from the circulation of baboons shortly after infusion, eluding the establishment of mixed chimerism. Our data indicate that two of the most important factors playing a role in this clearance are: 1) natural antibodies to non-Gal determinants, which are variably present in different baboons;and 2) absence of the species-specific cell-membrane protein, CD47, which is required to inhibit the innate immune system from rapidly clearing cells from the circulation. The goal of this proposal is to overcome these two barriers in order to establish mixed xenogeneic chimerism of GalT-KO HSC in baboons. Specifically, we will: 1) Optimize xenogeneic bone marrow engraftment by avoiding natural and induced anti-non-Gal antibodies;2) Test effect of human CD47 on engraftment of porcine marrow in baboons using GalT-KO pig bone marrow transduced with a human CD47 expression vector;and 3) Test the effect of GalT-KO pig HSC engraftment in baboons, either alone or in combination with vascularized porcine thymus transplantation, on the induction of tolerance of GalT-KO renal xenografts.
Aim 3 will apply the findings of Aims 1 and 2, as well as strategies developed in Project 1 of this Program Project, to the mixed chimerism approach for inducing transplantation tolerance to organ xenografts in this preclinical, discordant species combination. In addition, the experiments planned will provide basic information on xenogeneic stem cell engrafment and on the immunologic pathways responsible for xenogeneic rejection and tolerance induction in primates. As such, these studies should have both theoretical and practical implications for the eventual application of xenotransplantation as a clinical modality.

Public Health Relevance

Xenotransplantation remains the best near-term hope for alleviating the critical shortage of allogeneic organs today. However, the high level of immunosuppression required to avoid rejection of xenotransplants is likely to be too dangerous for clinical use. The goal of this project is to achieve tolerance of xenotransplants through mixed chimerism, and to thereby avoid the need for immunosuppressive drugs.

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Massachusetts General Hospital
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Peraino, Jaclyn Stromp; Zhang, Huiping; Rajasekera, Priyani V et al. (2014) Diphtheria toxin-based bivalent human IL-2 fusion toxin with improved efficacy for targeting human CD25(+) cells. J Immunol Methods 405:57-66
Yamada, Kazuhiko; Tasaki, Masayuki; Sekijima, Mitsuhiro et al. (2014) Porcine cytomegalovirus infection is associated with early rejection of kidney grafts in a pig to baboon xenotransplantation model. Transplantation 98:411-8
Wang, Yuantao; Wang, Hui; Bronson, Roderick et al. (2014) Rapid dendritic cell activation and resistance to allotolerance induction in anti-CD154-treated mice receiving CD47-deficient donor-specific transfusion. Cell Transplant 23:355-63
Navarro-Alvarez, Nalu; Yang, Yong-Guang (2014) Lack of CD47 on donor hepatocytes promotes innate immune cell activation and graft loss: a potential barrier to hepatocyte xenotransplantation. Cell Transplant 23:345-54
Kalscheuer, Hannes; Onoe, Takashi; Dahmani, Alexander et al. (2014) Xenograft tolerance and immune function of human T cells developing in pig thymus xenografts. J Immunol 192:3442-50
Tasaki, Masayuki; Shimizu, Akira; Hanekamp, Isabel et al. (2014) Rituximab treatment prevents the early development of proteinuria following pig-to-baboon xeno-kidney transplantation. J Am Soc Nephrol 25:737-44
Tena, A; Kurtz, J; Leonard, D A et al. (2014) Transgenic expression of human CD47 markedly increases engraftment in a murine model of pig-to-human hematopoietic cell transplantation. Am J Transplant 14:2713-22
Scalea, Joseph R; Villani, Vincenzo; Gillon, Bradford C et al. (2014) Development of antidonor antibody directed toward non-major histocompatibility complex antigens in tolerant animals. Transplantation 98:514-9
Sekijima, Mitsuhiro; Waki, Shiori; Sahara, Hisashi et al. (2014) Results of life-supporting galactosyltransferase knockout kidneys in cynomolgus monkeys using two different sources of galactosyltransferase knockout Swine. Transplantation 98:419-26
Haspot, F; Li, H W; Lucas, C L et al. (2014) Allospecific rejection of MHC class I-deficient bone marrow by CD8 T cells. Am J Transplant 14:49-58

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