Transgenic expression of CTLA4-Ig by fetal pig neurons for xenotransplantation

Abstract

The transplantation of fetal porcine neurons is a potential therapeutic strategy for the treatment of human neurodegenerative disorders. A major obstacle to xenotransplantation, however, is the immune-mediated rejection that is resistant to conventional immunosuppression. To determine whether genetically modified donor pig neurons could be used to deliver immunosuppressive proteins locally in the brain, transgenic pigs were developed that express the human T cell inhibitory molecule hCTLA4-Ig under the control of the neuron-specific enolase promoter. Expression was found in various areas of the brain of transgenic pigs, including the mesencephalon, hippocampus and cortex. Neurons from 28-day old embryos secreted hCTLA4-Ig in vitro and this resulted in a 50% reduction of the proliferative response of human T lymphocytes in xenogenic proliferation assays. Transgenic embryonic neurons also secreted hCTLA4-Ig and had developed normally in vivo several weeks after transplantation into the striatum of immunosuppressed rats that were used here to study the engraftment in the absence of immunity. In conclusion, these data show that neurons from our transgenic pigs express hCTLA4-Ig in situ and support the use of this material in future pre-clinical trials in neuron xenotransplantation.

Gene Editing, Gene Therapy, and Cell Xenotransplantation: Cell Transplantation Across Species

“…Despite immunological privileges of the brain, Tcell-mediated immune rejection of grafted tissue is a major concern in neural cell xenotransplantation [68] and cyclosporine A immunosuppression was not sufficient to protect neural cell xenografts in rats [69,70]. As an alternative to immunosuppression, transgenic expression of human CTLA4 in porcine neurons inhibited human T lymphocytes proliferation in vitro without affecting normal development after transplantation in rats [71]. Genetic modifications can also enhance transplanted cells' function or even confer new functions.…”

Immunological Challenges and Therapies in Xenotransplantation

“…Several porcine and human CTLA-4Ig transgenic animals were obtained (Martin et al 2005;Phelps et al 2009;Koshika et al 2011), and hCTLA-4Ig transgenic pigs expressing the transgene selectively in neurons enabled a long-term survival of neural precursors in mice (Martin et al 2005) and primates (Aron Badin et al 2009). Because the constitutive expression of pCTLA-4Ig resulted in severely immunosuppressed animals, pigs with an inducible pCTLA-4Ig expression have recently been obtained (Klymiuk et al 2012).…”

The Use of Xenotransplantation in Neurodegenerative Diseases: A Way to Go?

“…Whereas numbers of genetically-engineered pigs have been created for producing specific type of peripheral organs to be used in xenotransplantation that are less prone to rejection by immune-and acute humoralresponses. One example of this is the generation of transgenic pigs that express the human inhibitory molecule CTLA4-Ig under the control of the neuron-specific enolase promoter (Martin et al, 2005). The hCTLA4-Ig is a fusion protein that blocks the CD28-mediated T cell co-stimulatory signal (Linsley et al, 1991) and stimulates the immunosuppressive activities of antigen-presenting cells in Man and non-human primates (Grohmann et al, 2002).…”

“…The hCTLA4-Ig is a fusion protein that blocks the CD28-mediated T cell co-stimulatory signal (Linsley et al, 1991) and stimulates the immunosuppressive activities of antigen-presenting cells in Man and non-human primates (Grohmann et al, 2002). Transgenic neurons, isolated from the ventral mesencephalon or the cortex of G28 pig foetus, secrete hCTLA4-Ig, which binds to human CD80, inhibiting the proliferation of human peripheral blood mononuclear cells in xenogeneic mixed lymphocyte reactions in vitro (Martin et al, 2005). The hCTLA4-Ig protein is secreted by transgenic neurons following transplantation into the striatum of rats (Martin et al, 2005).…”

“…Transgenic neurons, isolated from the ventral mesencephalon or the cortex of G28 pig foetus, secrete hCTLA4-Ig, which binds to human CD80, inhibiting the proliferation of human peripheral blood mononuclear cells in xenogeneic mixed lymphocyte reactions in vitro (Martin et al, 2005). The hCTLA4-Ig protein is secreted by transgenic neurons following transplantation into the striatum of rats (Martin et al, 2005).…”