Long-term acceptance of rat cardiac allografts on the basis of adenovirus mediated CD40Ig plus CTLA4Ig gene therapies.

BACKGROUND: We have previously demonstrated that blockade of either CD80/86-CD28 or CD40-CD154 costimulatory pathways by using adenovirus vector coding CTLA4Ig (AdCTLA4Ig) or CD40Ig (AdCD40Ig) genes induced donor-specific tolerance in rat liver transplantation. In this study, we asked whether these gene-therapy-based costimulation blockade would induce tolerance in cardiac transplantation. METHODS: Heterotopic heart transplantation was performed in a full major histocompatibility complex (MHC) barrier combination of ACI (RT1avl) to Lewis (LEW, RT1l) rats. Vector (1 x 10(9) plaque forming unit [PFU]), AdLacZ, AdCTLA4Ig, or AdCD40Ig, was administered intravenously to recipient animals immediately after grafting, and graft survival, serum CTLA4Ig/CD40Ig levels, and graft histology were assessed. Tolerance was determined by secondary skin-graft challenging. RESULTS: Allografts of both untreated and AdLacZ controls were promptly rejected within 7 days, whereas a single treatment with AdCTLA4Ig or AdCD40Ig significantly prolonged median graft survival to 55.5 and 28.5 days, respectively. In contrast, the combined AdCTLA4Ig and AdCD40Ig gene therapy maintained high CTLA4Ig and CD40Ig levels through the posttransplant period and allowed long-term cardiac allograft survival for more than 270 days. However, both donor and third-party skin grafts were rejected in the animals who harbored cardiac grafts over 150 days. Also, typical features of chronic rejection were evident in the long-term surviving grafts. CONCLUSION: Simultaneous blockade of CD28 and CD154 pathways by AdCTLA4Ig plus AdCD40Ig induces a strong immunosuppression that allows long-term acceptance of full MHC mismatched cardiac graft in rats. This strategy, however, was not enough to induce tolerance to skin grafts and to avoid chronic rejection, as shown in the liver-transplantation model.

Induction of donor-specific tolerance by adenovirus-mediated CD40Ig gene therapy in rat liver transplantation.

BACKGROUND: Blockade of CD40-CD40 ligand (CD154) costimulatory pathway with anti-CD154 antibody (Ab) prolongs allograft survival in experimental organ transplantations; however, repeated agent administration is needed to provide an adequate immunosuppression. Seeking for simple and effective approach to interfere this signaling, we applied adenovirus-mediated gene therapy by encoding CD40Ig gene (AdCD40Ig). METHODS: Liver graft from ACI (RT1av1) rat was transplanted orthotopically into LEW (RT1l) rat, and AdCD40Ig was given to animals via the penile vein immediately after grafting (n=6). RESULTS: A single treatment with AdCD40Ig at 1x10(9) plaque forming units induced specific expression of CD40Ig gene on allograft liver, produced substantial amount of the protein in the sera, and allowed indefinite graft survival. Whereas, LEW recipients given no treatment or control adenovirus vector (AdLacZ) promptly rejected ACI liver. In addition, AdCD40Ig-treated, long-term survivors accepted skin graft from the donor strain but not the third party graft. Histopathology revealed that liver structure of the long-term surviving animals was completely preserved in normal with no infiltration of mononuclear cells. CONCLUSION: Blockade of CD40-CD154 pathway by CD40Ig gene therapy is a potent alloantigen-specific immunosuppressive strategy to induce permanent acceptance of liver allograft and would be a new therapeutic candidate in a clinical liver transplantation.