STABLE EXPRESSION OF INTERLEUKIN-10 SUPPRESSES THE DEVELOPMENT OF CHRONIC ALLOGRAFT REJECTION IN RATS

Abstract

O65* Aims: Despite the improved early graft survival, the development of chronic graft rejection mediated by immune and non-immune factors is still the dominant cause of late graft loss. In this study, we investigated the efficacy of gene therapy based on various therapeutic strategies to prevent the development of chronic allograft rejection. Stable expression of transgene (rat indoleamine 2,3-dioxygenase, IDO; human CTLA4Ig; or human IL-10) in the grafts was achieved by using recombinant adeno-associated viral vectors. Methods: Heterotopic heart transplantation was performed using LEW and F344 rats as donors or recipients, respectively. After in situ perfusion of the donor heart with HTK solution, rAAVs (0.5-1×1012 v.g./graft) were infused through the coronary artery. The grafts were then preserved with cold HTK solution for 6 hours before transplantation. The experimental groups were as follows: 1) no treatment; 2) CsA 2.5 mg/kg/d. i.m. d.0-4; 3) rAAV-GFP + CsA; 4) rAAV/IDO + CsA; 5) rAAV/CTLA4Ig + CsA; 6) rAAV/IL-10 + CsA. Results: rAAV/hIL-10 gene transfer could promote long-term graft survival in 5 of 6 animals (MST: >200 days), whereas only 3 of 7 grafts could survive for more than 200 days in the CsA treatment group (MST=21 days, n=6). No IDO-trasnduced grafts could survive for long-term. In addition, no improvement of long-term survival rate of allografts was observed in CTLA4Ig-transduced animals. Although marked reduction of graft infiltrating cells and serum anti-donor antibodies was detected in hCTLA4Ig-transduced animals, massive intimal proliferation of medium arteries and severe narrowing of vessel lumen were found in all hCTLA4Ig-transduced grafts at day 200. Conversely, significant attenuation of obliterative arteriopathy was observed in hIL-10-transduced grafts at day 200 compared with grafts treated with CsA only or vector control. Detection of gene transcript levels of long-term surviving grafts by real-time RT-PCR demonstrated lower TGF-beta1 and higher HO-1 transcript levels in hIL-10-transduced grafts Conclusions: These findings suggest that IL-10 can be an ideal target for therapeutic intervention of chronic allograft rejection.