Production and characterization of transgenic pigs expressing porcine CTLA4‐Ig

Abstract

Viable pigs exhibiting robust and ubiquitous expression of pCTLA4-Ig were produced on both a WT and GTKO background. Expression of pCTLA4-Ig resulted in acute susceptibility to opportunistic pathogens due at least in part to a significantly compromised humoral immune status. As this molecule is known to have immunosuppressive activity, high levels of pCTLA4-Ig expression in the blood, as well as defective development related to exposure to pCTLA4-Ig in utero, may contribute to this reduced immune status. Prophylactic treatment with antibiotics may promote survival of disease-free transgenic pigs to a size optimal for organ procurement for transplantation. Additional genetic modifications and/or tightly regulated expression of pCTLA4Ig may reduce the impact of this transgene on the humoral immune system.

Infection Barriers to Successful Xenotransplantation Focusing on Porcine Endogenous Retroviruses

“…Early attempts to reduce the amount of these antibodies by adsorption strategies failed (156). The most successful approach involves the production of (i) transgenic pigs that express human complement regulatory proteins capable of inhibiting the injurious effect of antibody-mediated complement activation on the vascularized pig organ (283,361) and (ii) pigs with a knocked-out galactose-alpha-1,3-galactosyltransferase gene locus (GalT-KO pigs) (62,168,253). This genetic knockout prevents expression of Gal-alpha-1,3-Gal residues.…”

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

“…A much more elegant approach would be to engineer islet cells to produce immunosuppressive antibodies or molecules locally at the graft site, thus preserving the islets and sparing the host from complications of systemic immunosuppression. Pig islets expressing anti-human CD2 [47], porcine cytotoxic T lymphocyte-associated antigen (pCTLA4) [48], or co-stimulatory signal inhibitor LEA29Y [49] have been described. Whereas transgenic pCTLA4 expression in pigs seemed to compromise their immune system [48], beta cell-specific or ubiquitous LEA29Y expression had no deleterious effect on pig health or reproduction [49,50].…”

“…Pig islets expressing anti-human CD2 [47], porcine cytotoxic T lymphocyte-associated antigen (pCTLA4) [48], or co-stimulatory signal inhibitor LEA29Y [49] have been described. Whereas transgenic pCTLA4 expression in pigs seemed to compromise their immune system [48], beta cell-specific or ubiquitous LEA29Y expression had no deleterious effect on pig health or reproduction [49,50]. Pig-tomouse transplantation of anti-CD2-or LEA29-expressing islets benefited from CD3 + T-cell depletion and protection against human peripheral blood mononuclear cells respectively [47,49] but pig-to-primate transplantation of pCTLA4-expressing islets did not provide significant amelioration of long-term survival (less than 5 months) [51].…”

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).…”